CA1084082A - Drag reducer for land vehicles - Google Patents
Drag reducer for land vehiclesInfo
- Publication number
- CA1084082A CA1084082A CA271,302A CA271302A CA1084082A CA 1084082 A CA1084082 A CA 1084082A CA 271302 A CA271302 A CA 271302A CA 1084082 A CA1084082 A CA 1084082A
- Authority
- CA
- Canada
- Prior art keywords
- fairing
- cab
- roof
- equal
- recited
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D35/00—Vehicle bodies characterised by streamlining
- B62D35/001—For commercial vehicles or tractor-trailer combinations, e.g. caravans
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
- Y02T10/82—Elements for improving aerodynamics
Abstract
ABSTRACT OF THE DISCLOSURE
Drag reducing means adapted to be mounted on the roof of the cab portion of a land vehicle in-cluding a trailing body for reducing aerodynamic drag.
The drag reducing means comprises a streamlined fair-ing including a bottom portion, a rear portion, a nose portion and a continuous contoured surface ex-tending widthwise and upwards from the nose portion to the rear portion. The contoured surface has a top portion and side portions which abut at their respec-tive boundaries. The top portion has a segment the tangential plane of which is inclined with respect to the horizontal at an angle which is less than or equal to approximately tan-1[2(H-h)/x] and greater than or equal to zero, where H represents the verti-cal distance from the roof of said cab portion to a top wall of said trailing body, h represents the height of said fairing, x represents the distance be-tween the rear portion of said fairing and the front of said trailing body, and h has a value greater than or equal to about .9H and less than H. The fairing is also designed so the segment of the top portion is located furthest from the bottom portion.
Drag reducing means adapted to be mounted on the roof of the cab portion of a land vehicle in-cluding a trailing body for reducing aerodynamic drag.
The drag reducing means comprises a streamlined fair-ing including a bottom portion, a rear portion, a nose portion and a continuous contoured surface ex-tending widthwise and upwards from the nose portion to the rear portion. The contoured surface has a top portion and side portions which abut at their respec-tive boundaries. The top portion has a segment the tangential plane of which is inclined with respect to the horizontal at an angle which is less than or equal to approximately tan-1[2(H-h)/x] and greater than or equal to zero, where H represents the verti-cal distance from the roof of said cab portion to a top wall of said trailing body, h represents the height of said fairing, x represents the distance be-tween the rear portion of said fairing and the front of said trailing body, and h has a value greater than or equal to about .9H and less than H. The fairing is also designed so the segment of the top portion is located furthest from the bottom portion.
Description
10840~2 This invention relates to a device for re-ducing the aerodynamic drag on articulated tractor-trailer combinations wherein the height of the trail-er is greater than the height of the tractor.
Research has demonstrated that a substan-tial part of the aerodynamic drag experienced by a tractor-trailer combination moving over the highway is the result of flow separations that occur at the forward edges of the trailer. These separations re-sult in large part from the inability of the flow that passes above the tractor roof and impinges on the front of the trailer to follow every contour of the trailer as it moves around its forward edges and onto its sides. The net effect of such separations is an increase in the average static pressure that acts on the front of the trailer with a corresponding increase in drag. It follows that significant drag reductions can be achieved with the aid of a device that will reduce flow separations in this region.
One prior art method of reducing the drag in the immediately described region lies in the de-sign of devices which are attached to the front of the trailer and improve the manner in which the im-pinging flow moves around the trailer's forward cor-ners. A disadvantage of such devices is the fact that those thus far designed have not been successful in the total elimination of flow separation, particu-larly of that part due to the flow which passes down-ward through the gap between the back of the tractor and the front of the trailer.
`~, 1(3 84(182 An alternate prior art method of reducing the drag on a tractor-trailer combination lies in the design of a device which attaches to the roof of the trac~or and prevents the flow passing over the roof from impinging on the trailer. Past examples of this approach have been primarily in the form of flow de-flectors designed to divert the flow about the por-tion of the front of the trailer which extends above the tractor cab roof. It is known, however, that the sizing of such devices for optimum drag reduction is a function of the size of the gap from the back of the tractor to the front of the trailer, that the drag reduction can decrease markedly when a device optimized for one gap is used at another, and that the performance of most such deflectors degrades very rapidly in the presence of winds that have a velocity component normal to the direction of motion.
The invention comprises a device that can be attached to the roof of a tractor for the purpose of reducing the aerodynamic drag on a tractor-trailer combination. The device is a fairing that is config-ured to prevent the flow that passes over the tractor roof from impinging on the front of the trailer. The fairing is designed to provide significant drag re-ductions in situations where the relative airstreamis aligned with the direction of motion of the vehicle (0 yaw condition), and in the presence of winds that have a velocity component normal to the direction of motion (yawed condition). Another important feature of the invention is that it provides a single device 1084(~82 ::.
which achieves optimum drag reductions on a given tractor-trailer combination for all practical gap settings between tractor and trailer.
The device consists essentially of a com-bination of top and side portions or walls. The topwall or portion is contoured upwardly from the front of the device, which is located at a forward position on the top surface of the tractor roof, to a rear-ward position whose height, ideally, is substantial-ly equal to the height of the front face or wall ofthe trailer above the tractor roof. The contour of the top wall of the device in the vicinity of the position of maximum height causes the flow that pas-ses over the top wall to be rearwardly directed across the gap between the tractor and the trailer, and to reattach smoothly on to the top of the trailer. Cri-teria are provided for the optimum design of the top wall or portion, together with a range of acceptable - non-optimum design conditions that will produce near-ly optimum drag reduction.
The side walls or portions of the device are generally vertical, and extend from the top wall to the roof of the tractor. The side walls are con-toured outwardly from a position near the longitudinal centerline of the tractor to a width at a rearward pos-ition which, ideally, is equal to that of the trail-er, or practically, as wide as the tractor roof will allow. The rearward portions of the side walls are configured to encourage the flow that passes along them to be rearwardly directed across the gap and to 108~ 82 reattach smoothly onto the side walls of the trailer.
Examples of side wall contours that will encourage good yaw performance are cited, and a range of widths that will yield usable drag reductions is provided.
The primary object of this invention is the provision of a device that can be attached to the roof of a tractor used in combination with a trailer.
A further object of this invention is the provision of a fairing which, by reducin~ wind resistance, will reduce fuel consumption, and will improve vehicle stability for purposes of reducing driver fatigue and enhancing safe vehicle operations.
- ~till another object of this invention is the provision of a device that will accomplish the foregoing objectives in a manner which is different from, and superior to those of previous devices intended for a similar purpose.
In accordance with the invention in one aspect there is provided a fairing adapted to be mounted at the bottom portion thereof on the roof of the cab of a truck with the longitudinal axis of the fairing being parallel to the longitudinal centerline of the roof of the cab, the fairing being adapted ; to reduce aerodynamic drag at the front portion of a truck trailer positioned behind the cab of a truck and comprising a nose portion disposed adjacent the front of the bottom portion of the fairing at the longitudinal axis thereof, the nose portion being adapted to be mounted adjacent the longitudinal centerline of the roof of the cab with the surface of the nose portion extending rearwardly with respect to the front portion of the roof of the cab, a curved top portion extending upwardly from the nose portion and rearwardly with respect to the longitudinal axis of the fairing, the top portion diverging in width from the nose portion toward the rear of the top portion, the rear of the top portion extending _ 5 _ 1084(182 transversely with respect to the longitudinal axis of the fairing and being adapted to be disposed above and adjacent the rear portion of the roof of the cab, each opposite end of the rear of the top portion being adapted to extend adjacent a different opposite extremity of the rear of the roof of the cab, the said top portion having a slope at its highest point which is substantially zero relative to the horizontal, and a : pair of oppositely disposed side portions diverging with respect to one another, each side portion extending rearwardly with respect to the nose portion and generally vertically to the bottom portion of the fairing from a different oppositely disposed longitudinal extremity of the diverging top portion, each side portion terminating adjacent and below a different end of the rear of the top portion.
In a further aspect there is provided a streamlined fairing adapted to be mounted on the roof of a cab portion of a land vehicle including a trailing body for reducing aerodyna-mic drag comprising, a bottom portion, a rear portion and a nose portion, and a continuous contoured surface extending widthwise and upwards from said nose portion to said rear portion and having a top portion and side portions which abut at their respective boundaries, said top portion having at least a segment the tangential plane of which is inclined with respect to the horizontal at an angle which is less than or equal to approximately tan 1 ~2(H-h)/x] and greater than or equal to zero, where H represents the vertical distance from the roof of said cab portion to a top wall of said trailing body, h represents the height of said fairing, x represents the distance between the rear portion of said fairing and the front of said trailing body, and h has a value greater than or equal to about .9H and less than H, and the said segment of said top - 5a -384~82 portion being located furthest from the said bottom portion.
In a still further aspect of the invention there is provided in combination with a load carrying vehicle of the type having a cab portion and a van portion spaced rearwardly of the cab portion, said van portion having a front wall which has a larger frontal area than the frontal area of the cab; drag reducing means mounted on the roof of the ca~, said drag re-ducing means comprising a streamlined fairing having at least a top wall smoothly curved upwardly from a point on the center line of the top surface of the cab roof to a rearward position substantially equal to the height of the front wall of the van at which rearward position a tangent to the top wall is generally parallel to a top surface of the van and a pair of oppositely disposed side walls smoothly curved outwardly from a point on the center line of the top surface of the cab roof with upper extremities of the side walls being joined to outer extremities of the top wall, the side walls diverging outwardly with respect to each other toward said rearward positio~.
In a still further aspect of the invention there is provided a streamlined fairing adapted to be mounted on a roof of a cab portion of a load carrying vehicle for reducing aero-dynamic drag, said vehicle including a van portion havin~ front and side walls, said front wall of said van portion extending above said cab portion, said fairing having a longitudinal axis and comprising: a bottom portion, a rear portion, and a continuous contoured surface extending width-wise and upwards from said bottom portion at the front of said fairing to said rear portion, said surface having a top portion and side portions on either side of the longitudinal axis of said fairing which abut at their respective boundaries, said top portion having at least a substantially horizontal segment a tangential plane of which is inclined with respect to the horizontal at an angle which is at least zero, said side portions diverging with - 5b --`- 1084~8Z
respect to each other toward said rear portion and having sub-stantially vertical segments which diverge with respect to the : longitudinal axis of said fairing at an angle which is at least zero, and said substantially horizontal segment of said top portion being located uppermost with respect to said bottom portion and said substantially vertical segments of said side portions being located furthest from said longitudinal axis of said fairing.
In a still further aspect of the invention there is 10 provided a streamlined fairing adapted to be mounted on a roof of a cab portion of a load carrying vehicle for reducing aero-dynamic drag, said vehicle including a van portion having front and side walls, said front wall of said van portion extending above said cab portion, said fairing having a longitudinal axis and comprising, a bottom portion, a rear portion, a continuous contoured surface extending widthwise and upwards from said bottom portion at the front of said fairing to said rear portion, and side portions on either side of the longitudinal axis of said fairing which abut at their respective boundaries with said contoured surface, said fairing further comprising a horizontalvariable release angle tab hinged to said contoured surface of said faîring, the height of said fairing being less than the vertical distance from the roof of said cab portion to the top of the front wall of said van portion.
In drawings which illustrate embodiments of the invention:
FIGURE 1 is a perspective view of a portion of a tractor-trailer combination having one form of prior art drag reducing means mounted on the roof of the cab of the tractor;
: 30 ~` 1084a8Z
FIGV~E 2 is a graph showing the effectiveness of the device shown in FIGURE l;
FIGURE 3 is a view like FIGURE 1 of another form of prior art drag reducing means;
FIGURE 4 is a graph like that shown in FIGU~E 2 showing a comparison of the effectiveness of the devices shown in FIGURES 1 and 3;
FIGURE S is a view like FIGURE 1 of one form of the present invention;
- 5d -1~8~Z
FIGURE 6 is a graph like that shown in FIG-URE 2 showing a comparison of the effectiveness of , the devices shown in FIGURES 1, 3, and 5;
FIGURE 7 is a diagrammatic showing of var-ious lengths of the drag reducing device of the in-: vention which come within the scope of the inventioni FIGURE 8 is a diagram illustrating the re-lationship between the width of the drag reducing de-vice and the width of the tractor roof and the van;
FIGURE 9 is a diagrammatic showing of means for extending the effective width of the drag reduc-ing devicei FIGURE 10 diagrammatically illustrates a means for extending the effective height of the drag reducing devicei FIGURE 11 diagrammatically illustrates an instance where the height of the drag reducing device plus the height of the tractor roof are not equal to the height of the trailer;
FIGURE 12 illustrates a situation where the upper edge of the drag reducing device is higher than the top of the trailer;
FIGURE 13 illustrates variations in the side wall configuration of drag reducers of the form of the instant invention;
FIGURE 14 is an envelope within which the plan view contour of the front and sides of drag re-ducing means is to be wholly contained;
FIGURE 15 is a diagrammatic elevational view showing various contours which the drag reducing 1084~Z
means of the invention can assume;
FIGURE 16 is a view like FIGURE 1 of another form of prior art drag reducing means; and FIGURE 17 is a graph showing a comparison 5 of the effectiveness of the devices shown in FIGURES
5 and 6.
In the discussion that follows, it will be useful to keep in mind the manner in which aerodynamic drag on a tractor-trailer combination is reduced with the aid of a device attached to the tractor roof.
When a device is attached to the roof of a tractor, the aerodynamic drag on the tractor is in-creased. However, because the front of the trailer rides in the low-speed wake produced by the device, l 5 the drag on the trailer is reduced. The net decrease ; in the drag of the combination, therefore, is equal to the decrease in the drag on the trailer minus the increase in the drag on the tractor. The net drag reduction that can be achieved on a given combination 20 will be a function of the device employed, the gap involved, and the ambient conditions.
In Figure 1, a prior art tractor 5 1 and trailer 51 ' are shown with one type of prior art drag reducing device 50 attached to the roof 51" of the 25 tractor. The height of the rear top edge 53 of the device above the tractor roof 51 " is equal to the height of the top forward edge 55 of the trailer above the tractor roof. The drag reducer 50 is de-signed to encourage the flow of air that passes over the roof of the tractor to move in an upward and ~084oBZ
rearward direction, as indicated by streamline 52, so that upon passing beyond the rear top edge of the device, the flow will move across the gap 54 in a substantially downstream direction and then reattach at the top forward edge 55 of the trailer. Thus, with regard to its design and with regard to the ef-fect it produces on the flow, device 50 can be con-sidered as a two-dimensional drag reducer. While, for the zero yaw flow condition assumed in Fig. 1, the flow passing above the tractor is prevented from impinging on the trailer thereby substantially reduc-ing its drag at that condition, a small part of the flow, illustrated by streamline 56, is widely diverted around the side edges 57 of device 50 giving rise to flow separations that increase the drag on the trac-tor 51. More importantly, these side edge separations increase in the presence of crosswinds, that is, for non-zero yaw conditions, and significantly reduce the effectiveness of device 50 at these conditions. This has been verified in experiments conducted in a low-speed wind-tunnel, results from which are presented in FIGURE 2. As can be seen from FIGURE 2, while the drag is substantially reduced at 0 yaw, the drag re-duction rapidly decreases in the presence of cross-winds, and even becomes negative, meaning that itincreases vehicle drag, at yaw angles of interest.
The average effectiveness of device 50 will be dis-cussed later.
A second type of drag reducer is illustrated in FIGURE 3. The drag reducing device 60, attached to the roof of tractor 61, is a deflector whose opt-imum height from the roof of the tractor is less than the height of the roof of trailer 61'; and whose opti-mum width is less than the trailer width. The device 60 is designed to deflect the airflow passing above the tractor in upward and outward directions in a manner to avoid entry of the air stream 62 into the - gap 63, and to cause the flow to reattach at the for-ward top edge 64 and sides 65 of the trailer. The height and width of a deflector which causes the stream surface to optimally reattach at the leading edges of the trailer is, for a given vehicle config-uration, a function of the size of the gap between the tractor and the trailer. In other words, a de-flector optimized at one gap will deflect the flowtoo widely at larger gaps, causing the flow to reat-tach downstream of the leading edges of the trailer -and too narrowly at smaller gaps, causing some of the flow to impinge on the front of the the trailer.
Consequently, non-optimum performance will be real-ized at these other gaps. Further, the optimum drag reduction that can be achieved at one gap setting will be generally different from that which can be achieved at another gap. Finally, the instability of the deflector's wake flow in the presence of cross-winds causes a significant reduction in the effective-. ness of the device with increasing yaw angle. Wind-tunnel measurements of the performance of device 60 are compared to those of device 50 in Figure 4 where, while device 60 proves to be generally supe-lQ~40az rior to device 50, the drag reduction effectiveness of device 60 is seen to decrease to near zero at yaw angles of interest. The average effectiveness of de-vice 60 will also be discussed later.
A third type of drag reducer is illustrated in Figure 16. The drag reducing device 40, attached to roof of tractor 41, is the combination of a deflec-tor whose optimum height from the roof of the tractor is less than the height of the trailer, and a fair-ing whose optimum width is equal to the width of the trailer. The rearwardly inclined upper surface 42 of the device is designed to deflect part of the air flow passing above the tractor in an upward direction so that the flow, after passing beyond the trailing edge 43 of the device, will continue to progress up-ward and onto the top of the trailing van. The side surfaces 44 of the device are designed to direct the remainder of the air flow in an initially outward direction before causing it to move downstream near the vertical trailing edges. The flow separates from these edges and reattaches along the upper vertical corners at the front of the trailer. As in the pre-ceding case, the separation stream surface produced downstream of the trailing edge of the inclined upper surface will, for a given deflector and vehicle con-figuration, be optimum at but one gap. At all other gaps the flow passing over the upper surface of the device will either be deflected too high or too low causing a decrease in drag reducing ability. The variation of average drag reduction effectiveness lQ~8~
with gap size to be presented later will demonstrate the considerable magnitude of the decrease in perfor-mance that may occur at such non-optimum operating conditions.
To summarize the prior art, there has been an evolution of designs for tractor roof-mounted drag reducers. With each new design there has come an im-provement in drag reducing ability. However, in every case cited, the designs either suffer from the inabil-ity to provide significant drag reductions in the crosswind situation or from having their design for optimum effectiveness being a function of the gap be-tween the tractor and the trailer.
The device of the instant invention has been found to provide significant drag reductions at 0 yaw, to maintain its effectiveness with increas-; ing yaw angle, and to have its geometry for optimum performance be independent of the size of the gap be-tween the tractor and the trailer. One form of the invention is illustrated in Figure 5. At zero yaw the flow of air passing above roof 71' of the trac-tor 71 is encouraged to divide, with a portion pass-ing over the top portion 72 of the device as shown by stream-line 73, and a portion passing around the side portions 74 of the device shown on the visible side by streamline 75. These flows are then encour-aged, by the shape of the device, to change their outward directions to downstream directions which are substantially parallel to the roof and sides of the trailer before separating from the device 70 at its downstream portion 76. The flow then continues across gap 77 and smoothly reat-taches itself to the trailer at its forward edges 78.
Ideally, to accomplish the latter effect in an optimum manner that is independent of the size of the gap 77, the height of the device 70 is sub-stantially that of the vertical distance from the tractor roof 71' to the trailer roof 80, the width of the device 70 is substantially that of the trail-er 82, the top wall is smoothly contoured upwardlyfrom the front of the device to the position of max-imum height at which position the tangential plane of the top wall is substantially parallel to the top of the trailer, and the side walls are smoothly con-toured outwardly from the front of the device to theposition of maximum width at which position the tan-gential planes of the side walls are substantially parallel to the sides of the trailer. In Figure 5 the longitudinal axis A of fairing 70 is shown. This axis A coincides with the center-line of the cab of tractor 71. It can be seen that fairing 70 is sym-metrical about a vertical plane passing through axis A.
General rules for the development of the top and side wall contours of the device to effect the described performance will be given later. Be-fore doing this, however, it is of interest to com-pare the performance of the instant invention with that of the prior art.
A comparison of wind-tunnel measurements of 1084~82 the variations of drag reduction effectiveness of de-vices 50, 60, and 70 with yaw angle is illustrated in Figure 6. As can be seen, device 70 provides su-perior performance not only at 0 yaw, but, more im-portantly, at non-zero yaw angles. Since a vehicle encounters a whole spectrum of wind-speeds and wind directions during highway operations, it is of ir,ter-est to estimate the average drag reduction that might be provided by a given device. This can be done by taking appropriate values for the average wind speed and vehicle operating speed, assuming that the wind is equally likely to approach the vehicle from any direction, computing the relative air-speed and yaw angle for a number of wind direction angles equally spaced around the compass, and then using this in-formation together with the drag coefficient versus yaw angle data to compute the average drag. This number would be indicative of the average drag that a vehicle could experience during long term opera-tions over the nation's highways. The results ofcomputations for a number of vehicle configurations, before and after modification by the addition of drag reduction devices, demonstrate that while the aver-age drag is a function of the vehicle design and the design of the drag reduction device, the average per-centage reduction in drag can be usually found in an approximate yaw angle range of from 5 to 8D.
With reference once again to Figure 6, it can be seen that the average drag reduction of the device of instant invention, estimated from the data 1084~2 data at yaw angles in the 5 to 8 range, is signif-icantly better than that of designs 50 and 60 of the prior art demonstrating the benefit of its unique de-sign. Similar results have been obtained in full-scale coast-down tests and in fuel economy runs.
Figure 17 presents a comparison of the variation of average drag reduction with gap size for device 70 of the instant invention with device 40 of the prior art. As can be seen, device 40 provides maximum drag reductions at a gap width of slightly greater than 50 inches. At gap distances less than this value, the device is not operating optimally in the respect that the flow is not sufficiently de-flected to prevent its impingement on the front of the trailer. As a consequence, the effectiveness of the drag reducer decreases very rapidly with decreas-ing gap size. At gap distances greater than the op-timum value, the flow is deflected too high so that flow reattachment occurs downstream of the trailer's leading edges. Again, the effectiveness decreases but this time as gap size increases.
In comparison, the effe~tiveness of device 70 increases with increasing gap size owing to the greater drag producing role played by the trailer face with increasing gap, and, hence, greater poten-tial for drag reduction as gap size increases. Note that the performance of device 70 is significantly better than device 40 except near the gap size about which device 40 is optimized. Since it is not unusu-al for the gap size on a given vehicle to be varied 1084~
quite frequently, it is apparent that the average drag reductions that would be provided by the device of the instant invention are significantly higher than those that would be provided by the device of the prior art.
As has been mentioned, device 70 as shown in Figure 5 is a preferred embodiment of the present invention. It has been found that, while ideal per-formance is achieved with the streamlined fairings of the present invention that extend the full-length of the tractor roof, useful drag reductions can be acheived with shorter designs, as illustrated by shapes 85 and 86 in Figure 7. The primary difference between the longer and the shorter fairings is that the longer fairing allows for the design of side~ wall contours that would provide better yaw performance than might be realized with a shorter design. Data have been obtained which indicate that acceptable performance can be achieved for fairings with lengths ~ as low as .2W, where W is the width of the trailer.
Ideally, the height of the streamlined fairing should be such that its height, h, be sub-stantially equal to the vertical distance from the top of the tractor cab roof to the top of the trail-er, H, that its width, w, be substantially equal to that of the trailer W, and that planes tangential to the top and side walls at their positions of maximum height and width be substantially parallel to the top and side walls of the trailer, respectively.
It is recognized that the width, w, may be limited by the width of the roof of the tractor to which it is attached, which is the usual case. This is particularly true in situations where the tractor is of conventional design as is illustrated in Figure 8. However, by designing the stream-lined fairing 87 such that a shallow angle, c~ is formed between the tangential plane of its sides at their back edges and the centerline of the truck, useful drag reductions can be achieved at a width as low as .5W. A consideration of the behavior of separated flows suggests that an angle c~ = tan 1 [(W-w)/x], where x is the distance from the back of the device to the front of the trailer, would provide near optimum drag reductions at zero yaw angle. However, excellent drag reduc-tions have been achieved in wind-tunnel tests with c~ nearly one-fourth the value suggested by the equation above.
In addition, the width w of the fairing may be wider than the width W of the trailer. However, in most situations the maximum width of the fairing is limited by legal restric-tions to the width W of the trailer.
A means for adjusting the angle with which the flow separates from the back edges of the sides of a streamline fairing of lesser width than the trailer is illustrated in Figure 9. Here, trim tab 80 (otherwise referred to as a variable release angle tab) is hinged near the back vertical edge of the fairing 88, and can be adjusted to g_ve optimum performance over a range of distances, x. Since the trim - - -- tab, in effect, forms an extension of the width of the fairing, the width of such a modified fairing would w + 2tsin7 where t is the width of the trim tab and ~ is the angle between the trim tab and the ; 5 centerline of the tractor.
It is further recognized that the height h of the streamline fairing may not always be equal to the vertical distance H from the roof of the cab portion of the vehicle to the top of the front wall of the trailing body. One instance where this can occur is illustrated in Figure 11. In this figure a tractor equipped with a fairing optimized for one trailer height indicated by top 91 is shown used in combination with a higher trailer as indicated by roof 90. Data have been obtained which demonstrate : that, in spite of the fact that some flow will im-pinge on the trailer, the device can retain greater than 9~ of its effectiveness for h > .9H and greater than 75% of its effectiveness for h > .&H.
Another instance where a height mismatch can occur is illustrated in Figure 12. Here a trac-tor equipped with a fairing optimized for one trailer - height indicated by roof 93 is shown used in combina-tion with a lower trailer indicated by top 92. Again, research results have been obtained which indicate that the device can retain greater than 93~ of its effectiveness for h < 1.2H and greater than 81~ of its effectivenss for h < 1.4.
In situations where a fairing is to be de-signed that will be used with trailers of various 1~
heights, a compromise design solution can be sought.It is apparent that the loss in performance for a given height mismatch is greater when the fairing is of lesser height than the trailer than when it is of greater height. This suggests that the fairing be designed with a height that is closer to that of the higher trailer than the lower one. A consideration of the results presented above indicates that a practically useful fairing be designed for a trailer whose height would be about equal to the height of the front wall of the lowest trailer above the cab roof plus about 60~ of the difference in height be-tween the highest and lowest trailer. For example, if the device is to be used with trailers that range in height from 12'6" to 13'6" above the ground, the fairing should be designed for a trailer height of about 13'1". A consideration of contemporary tractor heights suggests that the maximum value of h/H, cor-responding to use with the 12'6" trailer, is equal to about 1.2, and the minimum value of h/H, corres-ponding to use with the 13'6" is equal to about .9.
In light of the preceding data, it is apparent that the practical design solution provides optimum or near optimum performance for all trailer heights within the range considered in the solution.
Another possible practical design solution for the situation of use with trailers of various heights requires that the fairing be designed to have the smallest height possible. This would arise in situations where legal restrictions might limit the io8~82 ;~
height of the fairing to that of the lowest trailer.
In this situation, to regain the loss in performance with h < H, it would be advantageous to depart from the ideal design condition that requires the plane tangent to the top wall of the fairing at its maximum .- height position to be parallel to the top of the trailer. Thus, the fairing is provided with a slight inclination on the top wall near its trailing edge.
In this instance a consideration of the behavior of the flow separation from such a surface suggests that the angle of this inclination be less than or - equal to about tan 1[2(H - h)/x]. However, the pro-vision of such an angle for h much less than about .
9H would not be recommended because then the fairing may begin to exhibit some of the deleterious gap de-pendent performance characteristics of deflector type devices.
Another means for adjusting the flow that leaves the trailing edge of a fairing whose height h is less than H is illustrated in Figure 10. In this instance, trim tab 81 is shown hinged near the back horizontal edge of fairing 89, and deflected at a shallow angle ~ to optimize the performance of the fairing when used with the higher trailer.
To this point, discussion has been con-cerned with ideal and permissible non-ideal specifi-cations of the height, width, and length of fairings to the instant invention together with similar speci-fications for the inclination of its top and side walls at their positions of maximum height and width :10840~2 with respect to the top and side walls of the trail-er, respectively. Discussion will now be concerned with guidelines that can be used to develop the con-tours that fit within the prescribed dimensions and satisfy the specified tangency conditions.
Shown in Figure 15 are several examples of the profile view that the top wall of a streamlined fairing 97, 98, and 99 can assume and still function in a manner of performance consistent with the objec-tives of the invention. As can be seen, convex orconcave-convex contours can be used. The surface need not be continuously curved, as shown, but can include straigh~ portions as well. In all cases, at the position of maximum height, the tangent to the surface should be parallel to the~trailer roof or should be inclined relative to the trailer roof at the appropriate angle to ~ptimize performance when h < H. It is desirable, though not mandatory, that the surface be free of any areas where the slope is dis-continuous, the reason being that such areas couldcause flow separations to occur that might affect the angle that the flow separates from the top wall of the fairing, and could increase the drag on the fair-ing itself. For this same reason, gradual changes of direction with distance along the top wall are preferred over more rapid ones. Finally, it is de-sirable that the radius of curvature at the point of tangency be generous. For example, for fairings where ~ > h, the radius of curvature could be gradu-0 ally increased with distance from the front of the-20-1~2 fairing, or simpler yet, a circular arc could be de-scribed between the front and the position of maximum height with the center of the arc selected to satisfy the maximum height tangency condition. Or, for fair-ings where ~ ~ h, the radius of curvature could begradually decreased to a value that preferably would not be less than about .1W.
Figure 13 illustrates several configura-tions that the plan view of the sides 94, 95, and 96 can assume. As before, convex, concave-convex, or a combination of these and straight portions can be used. The guide lines used in the development of these contours within the length, width, and tangency requirements for the side walls are the same as those suggested for the top wall. Since the side wall con-tours play an important role in achieving good yaw performance, it is desirable that the width of any flat portion 94' at the front of the fairing be small compared with the width of the rear of the fairing.
A consideration of plan view shapes that should be capable of providing adequate yaw performance sug-gests that it is desirable to have the plan view con-tour of the front and sides of the fairing lie wholly within a rectangular envelope 100, Figure 14 of length ~ and of width w that is intersected by a line 110 having one end point located .2w aft of one of the forward corners of the rectangle and the other end point located .2w inboard from the same forward corner, and another line 110' similarly located from the opposite forward corner. This envelope is 108~)82 sketched as dashed line 100 in Figure 14.
- The drawings herein of the ins~ant inven-tion have shown its top and sides to intersect along a sharp corner. Experiments have shown that rounding the corner provides improvements in performance when compared to the sharp corner case. The drawings have also shown the profile view of the rear of the fair-ing to be generally vertical; for example, as in ~ Figure 7. Experiments have demonstrated that useful performance increases can be achieved, particularly with fairings of shorter length, by tilting the plane of the rear of the fairing such that the rearward extremity 84' of the top wall in Figure 7 is dis-placed in the aft direction.
Finally, the drawings have generally shown the rear of the fairing in the same vertical plane as the back of the tractor. However, other mounting positions on the roof of the tractor may be used.
A rearward displacement of the fairing from the posi-tions shown in the drawings may be limited by the requirement that the device not interfere with the~ .
articulation of the vehicle. A forward dii~placement of the fairing from that position may be limited by a legal length requirement that would mean that the fairing could not extend further forward than the front of the tractor.
From the foregoing, it is seen that there is herein provided an improved device for reducing the aerodynamic drag on tractor-trailer truck com-binations. Though the discussion above was speci-~0~4~82 fically concerned with the use of the present inven-tion on articulated vehicles, it is to be understood that the device would also have application for re-ducing the aerodynamic drag on single-chassis truck/
van combinations. Similarly, the discussion was con-cerned with van type trailers. It is to be further understood that the device would have application in any situation where the height of the front wall of the trailing body was higher than that of the cab.
Finally, the discussion and illustrations have shown the plan view contour of the sides of the fairing to be symmetrical about the longitudinal axis of the fairing. While this is preferred in order to provide similar drag reductions at equal positive and negative angles of yaw, it is to be understood that significant aerodynamic drag reductions could also be achieved with use of asymmetric contours developed in accordance with the guidelines set forth earlier.
3o
Research has demonstrated that a substan-tial part of the aerodynamic drag experienced by a tractor-trailer combination moving over the highway is the result of flow separations that occur at the forward edges of the trailer. These separations re-sult in large part from the inability of the flow that passes above the tractor roof and impinges on the front of the trailer to follow every contour of the trailer as it moves around its forward edges and onto its sides. The net effect of such separations is an increase in the average static pressure that acts on the front of the trailer with a corresponding increase in drag. It follows that significant drag reductions can be achieved with the aid of a device that will reduce flow separations in this region.
One prior art method of reducing the drag in the immediately described region lies in the de-sign of devices which are attached to the front of the trailer and improve the manner in which the im-pinging flow moves around the trailer's forward cor-ners. A disadvantage of such devices is the fact that those thus far designed have not been successful in the total elimination of flow separation, particu-larly of that part due to the flow which passes down-ward through the gap between the back of the tractor and the front of the trailer.
`~, 1(3 84(182 An alternate prior art method of reducing the drag on a tractor-trailer combination lies in the design of a device which attaches to the roof of the trac~or and prevents the flow passing over the roof from impinging on the trailer. Past examples of this approach have been primarily in the form of flow de-flectors designed to divert the flow about the por-tion of the front of the trailer which extends above the tractor cab roof. It is known, however, that the sizing of such devices for optimum drag reduction is a function of the size of the gap from the back of the tractor to the front of the trailer, that the drag reduction can decrease markedly when a device optimized for one gap is used at another, and that the performance of most such deflectors degrades very rapidly in the presence of winds that have a velocity component normal to the direction of motion.
The invention comprises a device that can be attached to the roof of a tractor for the purpose of reducing the aerodynamic drag on a tractor-trailer combination. The device is a fairing that is config-ured to prevent the flow that passes over the tractor roof from impinging on the front of the trailer. The fairing is designed to provide significant drag re-ductions in situations where the relative airstreamis aligned with the direction of motion of the vehicle (0 yaw condition), and in the presence of winds that have a velocity component normal to the direction of motion (yawed condition). Another important feature of the invention is that it provides a single device 1084(~82 ::.
which achieves optimum drag reductions on a given tractor-trailer combination for all practical gap settings between tractor and trailer.
The device consists essentially of a com-bination of top and side portions or walls. The topwall or portion is contoured upwardly from the front of the device, which is located at a forward position on the top surface of the tractor roof, to a rear-ward position whose height, ideally, is substantial-ly equal to the height of the front face or wall ofthe trailer above the tractor roof. The contour of the top wall of the device in the vicinity of the position of maximum height causes the flow that pas-ses over the top wall to be rearwardly directed across the gap between the tractor and the trailer, and to reattach smoothly on to the top of the trailer. Cri-teria are provided for the optimum design of the top wall or portion, together with a range of acceptable - non-optimum design conditions that will produce near-ly optimum drag reduction.
The side walls or portions of the device are generally vertical, and extend from the top wall to the roof of the tractor. The side walls are con-toured outwardly from a position near the longitudinal centerline of the tractor to a width at a rearward pos-ition which, ideally, is equal to that of the trail-er, or practically, as wide as the tractor roof will allow. The rearward portions of the side walls are configured to encourage the flow that passes along them to be rearwardly directed across the gap and to 108~ 82 reattach smoothly onto the side walls of the trailer.
Examples of side wall contours that will encourage good yaw performance are cited, and a range of widths that will yield usable drag reductions is provided.
The primary object of this invention is the provision of a device that can be attached to the roof of a tractor used in combination with a trailer.
A further object of this invention is the provision of a fairing which, by reducin~ wind resistance, will reduce fuel consumption, and will improve vehicle stability for purposes of reducing driver fatigue and enhancing safe vehicle operations.
- ~till another object of this invention is the provision of a device that will accomplish the foregoing objectives in a manner which is different from, and superior to those of previous devices intended for a similar purpose.
In accordance with the invention in one aspect there is provided a fairing adapted to be mounted at the bottom portion thereof on the roof of the cab of a truck with the longitudinal axis of the fairing being parallel to the longitudinal centerline of the roof of the cab, the fairing being adapted ; to reduce aerodynamic drag at the front portion of a truck trailer positioned behind the cab of a truck and comprising a nose portion disposed adjacent the front of the bottom portion of the fairing at the longitudinal axis thereof, the nose portion being adapted to be mounted adjacent the longitudinal centerline of the roof of the cab with the surface of the nose portion extending rearwardly with respect to the front portion of the roof of the cab, a curved top portion extending upwardly from the nose portion and rearwardly with respect to the longitudinal axis of the fairing, the top portion diverging in width from the nose portion toward the rear of the top portion, the rear of the top portion extending _ 5 _ 1084(182 transversely with respect to the longitudinal axis of the fairing and being adapted to be disposed above and adjacent the rear portion of the roof of the cab, each opposite end of the rear of the top portion being adapted to extend adjacent a different opposite extremity of the rear of the roof of the cab, the said top portion having a slope at its highest point which is substantially zero relative to the horizontal, and a : pair of oppositely disposed side portions diverging with respect to one another, each side portion extending rearwardly with respect to the nose portion and generally vertically to the bottom portion of the fairing from a different oppositely disposed longitudinal extremity of the diverging top portion, each side portion terminating adjacent and below a different end of the rear of the top portion.
In a further aspect there is provided a streamlined fairing adapted to be mounted on the roof of a cab portion of a land vehicle including a trailing body for reducing aerodyna-mic drag comprising, a bottom portion, a rear portion and a nose portion, and a continuous contoured surface extending widthwise and upwards from said nose portion to said rear portion and having a top portion and side portions which abut at their respective boundaries, said top portion having at least a segment the tangential plane of which is inclined with respect to the horizontal at an angle which is less than or equal to approximately tan 1 ~2(H-h)/x] and greater than or equal to zero, where H represents the vertical distance from the roof of said cab portion to a top wall of said trailing body, h represents the height of said fairing, x represents the distance between the rear portion of said fairing and the front of said trailing body, and h has a value greater than or equal to about .9H and less than H, and the said segment of said top - 5a -384~82 portion being located furthest from the said bottom portion.
In a still further aspect of the invention there is provided in combination with a load carrying vehicle of the type having a cab portion and a van portion spaced rearwardly of the cab portion, said van portion having a front wall which has a larger frontal area than the frontal area of the cab; drag reducing means mounted on the roof of the ca~, said drag re-ducing means comprising a streamlined fairing having at least a top wall smoothly curved upwardly from a point on the center line of the top surface of the cab roof to a rearward position substantially equal to the height of the front wall of the van at which rearward position a tangent to the top wall is generally parallel to a top surface of the van and a pair of oppositely disposed side walls smoothly curved outwardly from a point on the center line of the top surface of the cab roof with upper extremities of the side walls being joined to outer extremities of the top wall, the side walls diverging outwardly with respect to each other toward said rearward positio~.
In a still further aspect of the invention there is provided a streamlined fairing adapted to be mounted on a roof of a cab portion of a load carrying vehicle for reducing aero-dynamic drag, said vehicle including a van portion havin~ front and side walls, said front wall of said van portion extending above said cab portion, said fairing having a longitudinal axis and comprising: a bottom portion, a rear portion, and a continuous contoured surface extending width-wise and upwards from said bottom portion at the front of said fairing to said rear portion, said surface having a top portion and side portions on either side of the longitudinal axis of said fairing which abut at their respective boundaries, said top portion having at least a substantially horizontal segment a tangential plane of which is inclined with respect to the horizontal at an angle which is at least zero, said side portions diverging with - 5b --`- 1084~8Z
respect to each other toward said rear portion and having sub-stantially vertical segments which diverge with respect to the : longitudinal axis of said fairing at an angle which is at least zero, and said substantially horizontal segment of said top portion being located uppermost with respect to said bottom portion and said substantially vertical segments of said side portions being located furthest from said longitudinal axis of said fairing.
In a still further aspect of the invention there is 10 provided a streamlined fairing adapted to be mounted on a roof of a cab portion of a load carrying vehicle for reducing aero-dynamic drag, said vehicle including a van portion having front and side walls, said front wall of said van portion extending above said cab portion, said fairing having a longitudinal axis and comprising, a bottom portion, a rear portion, a continuous contoured surface extending widthwise and upwards from said bottom portion at the front of said fairing to said rear portion, and side portions on either side of the longitudinal axis of said fairing which abut at their respective boundaries with said contoured surface, said fairing further comprising a horizontalvariable release angle tab hinged to said contoured surface of said faîring, the height of said fairing being less than the vertical distance from the roof of said cab portion to the top of the front wall of said van portion.
In drawings which illustrate embodiments of the invention:
FIGURE 1 is a perspective view of a portion of a tractor-trailer combination having one form of prior art drag reducing means mounted on the roof of the cab of the tractor;
: 30 ~` 1084a8Z
FIGV~E 2 is a graph showing the effectiveness of the device shown in FIGURE l;
FIGURE 3 is a view like FIGURE 1 of another form of prior art drag reducing means;
FIGURE 4 is a graph like that shown in FIGU~E 2 showing a comparison of the effectiveness of the devices shown in FIGURES 1 and 3;
FIGURE S is a view like FIGURE 1 of one form of the present invention;
- 5d -1~8~Z
FIGURE 6 is a graph like that shown in FIG-URE 2 showing a comparison of the effectiveness of , the devices shown in FIGURES 1, 3, and 5;
FIGURE 7 is a diagrammatic showing of var-ious lengths of the drag reducing device of the in-: vention which come within the scope of the inventioni FIGURE 8 is a diagram illustrating the re-lationship between the width of the drag reducing de-vice and the width of the tractor roof and the van;
FIGURE 9 is a diagrammatic showing of means for extending the effective width of the drag reduc-ing devicei FIGURE 10 diagrammatically illustrates a means for extending the effective height of the drag reducing devicei FIGURE 11 diagrammatically illustrates an instance where the height of the drag reducing device plus the height of the tractor roof are not equal to the height of the trailer;
FIGURE 12 illustrates a situation where the upper edge of the drag reducing device is higher than the top of the trailer;
FIGURE 13 illustrates variations in the side wall configuration of drag reducers of the form of the instant invention;
FIGURE 14 is an envelope within which the plan view contour of the front and sides of drag re-ducing means is to be wholly contained;
FIGURE 15 is a diagrammatic elevational view showing various contours which the drag reducing 1084~Z
means of the invention can assume;
FIGURE 16 is a view like FIGURE 1 of another form of prior art drag reducing means; and FIGURE 17 is a graph showing a comparison 5 of the effectiveness of the devices shown in FIGURES
5 and 6.
In the discussion that follows, it will be useful to keep in mind the manner in which aerodynamic drag on a tractor-trailer combination is reduced with the aid of a device attached to the tractor roof.
When a device is attached to the roof of a tractor, the aerodynamic drag on the tractor is in-creased. However, because the front of the trailer rides in the low-speed wake produced by the device, l 5 the drag on the trailer is reduced. The net decrease ; in the drag of the combination, therefore, is equal to the decrease in the drag on the trailer minus the increase in the drag on the tractor. The net drag reduction that can be achieved on a given combination 20 will be a function of the device employed, the gap involved, and the ambient conditions.
In Figure 1, a prior art tractor 5 1 and trailer 51 ' are shown with one type of prior art drag reducing device 50 attached to the roof 51" of the 25 tractor. The height of the rear top edge 53 of the device above the tractor roof 51 " is equal to the height of the top forward edge 55 of the trailer above the tractor roof. The drag reducer 50 is de-signed to encourage the flow of air that passes over the roof of the tractor to move in an upward and ~084oBZ
rearward direction, as indicated by streamline 52, so that upon passing beyond the rear top edge of the device, the flow will move across the gap 54 in a substantially downstream direction and then reattach at the top forward edge 55 of the trailer. Thus, with regard to its design and with regard to the ef-fect it produces on the flow, device 50 can be con-sidered as a two-dimensional drag reducer. While, for the zero yaw flow condition assumed in Fig. 1, the flow passing above the tractor is prevented from impinging on the trailer thereby substantially reduc-ing its drag at that condition, a small part of the flow, illustrated by streamline 56, is widely diverted around the side edges 57 of device 50 giving rise to flow separations that increase the drag on the trac-tor 51. More importantly, these side edge separations increase in the presence of crosswinds, that is, for non-zero yaw conditions, and significantly reduce the effectiveness of device 50 at these conditions. This has been verified in experiments conducted in a low-speed wind-tunnel, results from which are presented in FIGURE 2. As can be seen from FIGURE 2, while the drag is substantially reduced at 0 yaw, the drag re-duction rapidly decreases in the presence of cross-winds, and even becomes negative, meaning that itincreases vehicle drag, at yaw angles of interest.
The average effectiveness of device 50 will be dis-cussed later.
A second type of drag reducer is illustrated in FIGURE 3. The drag reducing device 60, attached to the roof of tractor 61, is a deflector whose opt-imum height from the roof of the tractor is less than the height of the roof of trailer 61'; and whose opti-mum width is less than the trailer width. The device 60 is designed to deflect the airflow passing above the tractor in upward and outward directions in a manner to avoid entry of the air stream 62 into the - gap 63, and to cause the flow to reattach at the for-ward top edge 64 and sides 65 of the trailer. The height and width of a deflector which causes the stream surface to optimally reattach at the leading edges of the trailer is, for a given vehicle config-uration, a function of the size of the gap between the tractor and the trailer. In other words, a de-flector optimized at one gap will deflect the flowtoo widely at larger gaps, causing the flow to reat-tach downstream of the leading edges of the trailer -and too narrowly at smaller gaps, causing some of the flow to impinge on the front of the the trailer.
Consequently, non-optimum performance will be real-ized at these other gaps. Further, the optimum drag reduction that can be achieved at one gap setting will be generally different from that which can be achieved at another gap. Finally, the instability of the deflector's wake flow in the presence of cross-winds causes a significant reduction in the effective-. ness of the device with increasing yaw angle. Wind-tunnel measurements of the performance of device 60 are compared to those of device 50 in Figure 4 where, while device 60 proves to be generally supe-lQ~40az rior to device 50, the drag reduction effectiveness of device 60 is seen to decrease to near zero at yaw angles of interest. The average effectiveness of de-vice 60 will also be discussed later.
A third type of drag reducer is illustrated in Figure 16. The drag reducing device 40, attached to roof of tractor 41, is the combination of a deflec-tor whose optimum height from the roof of the tractor is less than the height of the trailer, and a fair-ing whose optimum width is equal to the width of the trailer. The rearwardly inclined upper surface 42 of the device is designed to deflect part of the air flow passing above the tractor in an upward direction so that the flow, after passing beyond the trailing edge 43 of the device, will continue to progress up-ward and onto the top of the trailing van. The side surfaces 44 of the device are designed to direct the remainder of the air flow in an initially outward direction before causing it to move downstream near the vertical trailing edges. The flow separates from these edges and reattaches along the upper vertical corners at the front of the trailer. As in the pre-ceding case, the separation stream surface produced downstream of the trailing edge of the inclined upper surface will, for a given deflector and vehicle con-figuration, be optimum at but one gap. At all other gaps the flow passing over the upper surface of the device will either be deflected too high or too low causing a decrease in drag reducing ability. The variation of average drag reduction effectiveness lQ~8~
with gap size to be presented later will demonstrate the considerable magnitude of the decrease in perfor-mance that may occur at such non-optimum operating conditions.
To summarize the prior art, there has been an evolution of designs for tractor roof-mounted drag reducers. With each new design there has come an im-provement in drag reducing ability. However, in every case cited, the designs either suffer from the inabil-ity to provide significant drag reductions in the crosswind situation or from having their design for optimum effectiveness being a function of the gap be-tween the tractor and the trailer.
The device of the instant invention has been found to provide significant drag reductions at 0 yaw, to maintain its effectiveness with increas-; ing yaw angle, and to have its geometry for optimum performance be independent of the size of the gap be-tween the tractor and the trailer. One form of the invention is illustrated in Figure 5. At zero yaw the flow of air passing above roof 71' of the trac-tor 71 is encouraged to divide, with a portion pass-ing over the top portion 72 of the device as shown by stream-line 73, and a portion passing around the side portions 74 of the device shown on the visible side by streamline 75. These flows are then encour-aged, by the shape of the device, to change their outward directions to downstream directions which are substantially parallel to the roof and sides of the trailer before separating from the device 70 at its downstream portion 76. The flow then continues across gap 77 and smoothly reat-taches itself to the trailer at its forward edges 78.
Ideally, to accomplish the latter effect in an optimum manner that is independent of the size of the gap 77, the height of the device 70 is sub-stantially that of the vertical distance from the tractor roof 71' to the trailer roof 80, the width of the device 70 is substantially that of the trail-er 82, the top wall is smoothly contoured upwardlyfrom the front of the device to the position of max-imum height at which position the tangential plane of the top wall is substantially parallel to the top of the trailer, and the side walls are smoothly con-toured outwardly from the front of the device to theposition of maximum width at which position the tan-gential planes of the side walls are substantially parallel to the sides of the trailer. In Figure 5 the longitudinal axis A of fairing 70 is shown. This axis A coincides with the center-line of the cab of tractor 71. It can be seen that fairing 70 is sym-metrical about a vertical plane passing through axis A.
General rules for the development of the top and side wall contours of the device to effect the described performance will be given later. Be-fore doing this, however, it is of interest to com-pare the performance of the instant invention with that of the prior art.
A comparison of wind-tunnel measurements of 1084~82 the variations of drag reduction effectiveness of de-vices 50, 60, and 70 with yaw angle is illustrated in Figure 6. As can be seen, device 70 provides su-perior performance not only at 0 yaw, but, more im-portantly, at non-zero yaw angles. Since a vehicle encounters a whole spectrum of wind-speeds and wind directions during highway operations, it is of ir,ter-est to estimate the average drag reduction that might be provided by a given device. This can be done by taking appropriate values for the average wind speed and vehicle operating speed, assuming that the wind is equally likely to approach the vehicle from any direction, computing the relative air-speed and yaw angle for a number of wind direction angles equally spaced around the compass, and then using this in-formation together with the drag coefficient versus yaw angle data to compute the average drag. This number would be indicative of the average drag that a vehicle could experience during long term opera-tions over the nation's highways. The results ofcomputations for a number of vehicle configurations, before and after modification by the addition of drag reduction devices, demonstrate that while the aver-age drag is a function of the vehicle design and the design of the drag reduction device, the average per-centage reduction in drag can be usually found in an approximate yaw angle range of from 5 to 8D.
With reference once again to Figure 6, it can be seen that the average drag reduction of the device of instant invention, estimated from the data 1084~2 data at yaw angles in the 5 to 8 range, is signif-icantly better than that of designs 50 and 60 of the prior art demonstrating the benefit of its unique de-sign. Similar results have been obtained in full-scale coast-down tests and in fuel economy runs.
Figure 17 presents a comparison of the variation of average drag reduction with gap size for device 70 of the instant invention with device 40 of the prior art. As can be seen, device 40 provides maximum drag reductions at a gap width of slightly greater than 50 inches. At gap distances less than this value, the device is not operating optimally in the respect that the flow is not sufficiently de-flected to prevent its impingement on the front of the trailer. As a consequence, the effectiveness of the drag reducer decreases very rapidly with decreas-ing gap size. At gap distances greater than the op-timum value, the flow is deflected too high so that flow reattachment occurs downstream of the trailer's leading edges. Again, the effectiveness decreases but this time as gap size increases.
In comparison, the effe~tiveness of device 70 increases with increasing gap size owing to the greater drag producing role played by the trailer face with increasing gap, and, hence, greater poten-tial for drag reduction as gap size increases. Note that the performance of device 70 is significantly better than device 40 except near the gap size about which device 40 is optimized. Since it is not unusu-al for the gap size on a given vehicle to be varied 1084~
quite frequently, it is apparent that the average drag reductions that would be provided by the device of the instant invention are significantly higher than those that would be provided by the device of the prior art.
As has been mentioned, device 70 as shown in Figure 5 is a preferred embodiment of the present invention. It has been found that, while ideal per-formance is achieved with the streamlined fairings of the present invention that extend the full-length of the tractor roof, useful drag reductions can be acheived with shorter designs, as illustrated by shapes 85 and 86 in Figure 7. The primary difference between the longer and the shorter fairings is that the longer fairing allows for the design of side~ wall contours that would provide better yaw performance than might be realized with a shorter design. Data have been obtained which indicate that acceptable performance can be achieved for fairings with lengths ~ as low as .2W, where W is the width of the trailer.
Ideally, the height of the streamlined fairing should be such that its height, h, be sub-stantially equal to the vertical distance from the top of the tractor cab roof to the top of the trail-er, H, that its width, w, be substantially equal to that of the trailer W, and that planes tangential to the top and side walls at their positions of maximum height and width be substantially parallel to the top and side walls of the trailer, respectively.
It is recognized that the width, w, may be limited by the width of the roof of the tractor to which it is attached, which is the usual case. This is particularly true in situations where the tractor is of conventional design as is illustrated in Figure 8. However, by designing the stream-lined fairing 87 such that a shallow angle, c~ is formed between the tangential plane of its sides at their back edges and the centerline of the truck, useful drag reductions can be achieved at a width as low as .5W. A consideration of the behavior of separated flows suggests that an angle c~ = tan 1 [(W-w)/x], where x is the distance from the back of the device to the front of the trailer, would provide near optimum drag reductions at zero yaw angle. However, excellent drag reduc-tions have been achieved in wind-tunnel tests with c~ nearly one-fourth the value suggested by the equation above.
In addition, the width w of the fairing may be wider than the width W of the trailer. However, in most situations the maximum width of the fairing is limited by legal restric-tions to the width W of the trailer.
A means for adjusting the angle with which the flow separates from the back edges of the sides of a streamline fairing of lesser width than the trailer is illustrated in Figure 9. Here, trim tab 80 (otherwise referred to as a variable release angle tab) is hinged near the back vertical edge of the fairing 88, and can be adjusted to g_ve optimum performance over a range of distances, x. Since the trim - - -- tab, in effect, forms an extension of the width of the fairing, the width of such a modified fairing would w + 2tsin7 where t is the width of the trim tab and ~ is the angle between the trim tab and the ; 5 centerline of the tractor.
It is further recognized that the height h of the streamline fairing may not always be equal to the vertical distance H from the roof of the cab portion of the vehicle to the top of the front wall of the trailing body. One instance where this can occur is illustrated in Figure 11. In this figure a tractor equipped with a fairing optimized for one trailer height indicated by top 91 is shown used in combination with a higher trailer as indicated by roof 90. Data have been obtained which demonstrate : that, in spite of the fact that some flow will im-pinge on the trailer, the device can retain greater than 9~ of its effectiveness for h > .9H and greater than 75% of its effectiveness for h > .&H.
Another instance where a height mismatch can occur is illustrated in Figure 12. Here a trac-tor equipped with a fairing optimized for one trailer - height indicated by roof 93 is shown used in combina-tion with a lower trailer indicated by top 92. Again, research results have been obtained which indicate that the device can retain greater than 93~ of its effectiveness for h < 1.2H and greater than 81~ of its effectivenss for h < 1.4.
In situations where a fairing is to be de-signed that will be used with trailers of various 1~
heights, a compromise design solution can be sought.It is apparent that the loss in performance for a given height mismatch is greater when the fairing is of lesser height than the trailer than when it is of greater height. This suggests that the fairing be designed with a height that is closer to that of the higher trailer than the lower one. A consideration of the results presented above indicates that a practically useful fairing be designed for a trailer whose height would be about equal to the height of the front wall of the lowest trailer above the cab roof plus about 60~ of the difference in height be-tween the highest and lowest trailer. For example, if the device is to be used with trailers that range in height from 12'6" to 13'6" above the ground, the fairing should be designed for a trailer height of about 13'1". A consideration of contemporary tractor heights suggests that the maximum value of h/H, cor-responding to use with the 12'6" trailer, is equal to about 1.2, and the minimum value of h/H, corres-ponding to use with the 13'6" is equal to about .9.
In light of the preceding data, it is apparent that the practical design solution provides optimum or near optimum performance for all trailer heights within the range considered in the solution.
Another possible practical design solution for the situation of use with trailers of various heights requires that the fairing be designed to have the smallest height possible. This would arise in situations where legal restrictions might limit the io8~82 ;~
height of the fairing to that of the lowest trailer.
In this situation, to regain the loss in performance with h < H, it would be advantageous to depart from the ideal design condition that requires the plane tangent to the top wall of the fairing at its maximum .- height position to be parallel to the top of the trailer. Thus, the fairing is provided with a slight inclination on the top wall near its trailing edge.
In this instance a consideration of the behavior of the flow separation from such a surface suggests that the angle of this inclination be less than or - equal to about tan 1[2(H - h)/x]. However, the pro-vision of such an angle for h much less than about .
9H would not be recommended because then the fairing may begin to exhibit some of the deleterious gap de-pendent performance characteristics of deflector type devices.
Another means for adjusting the flow that leaves the trailing edge of a fairing whose height h is less than H is illustrated in Figure 10. In this instance, trim tab 81 is shown hinged near the back horizontal edge of fairing 89, and deflected at a shallow angle ~ to optimize the performance of the fairing when used with the higher trailer.
To this point, discussion has been con-cerned with ideal and permissible non-ideal specifi-cations of the height, width, and length of fairings to the instant invention together with similar speci-fications for the inclination of its top and side walls at their positions of maximum height and width :10840~2 with respect to the top and side walls of the trail-er, respectively. Discussion will now be concerned with guidelines that can be used to develop the con-tours that fit within the prescribed dimensions and satisfy the specified tangency conditions.
Shown in Figure 15 are several examples of the profile view that the top wall of a streamlined fairing 97, 98, and 99 can assume and still function in a manner of performance consistent with the objec-tives of the invention. As can be seen, convex orconcave-convex contours can be used. The surface need not be continuously curved, as shown, but can include straigh~ portions as well. In all cases, at the position of maximum height, the tangent to the surface should be parallel to the~trailer roof or should be inclined relative to the trailer roof at the appropriate angle to ~ptimize performance when h < H. It is desirable, though not mandatory, that the surface be free of any areas where the slope is dis-continuous, the reason being that such areas couldcause flow separations to occur that might affect the angle that the flow separates from the top wall of the fairing, and could increase the drag on the fair-ing itself. For this same reason, gradual changes of direction with distance along the top wall are preferred over more rapid ones. Finally, it is de-sirable that the radius of curvature at the point of tangency be generous. For example, for fairings where ~ > h, the radius of curvature could be gradu-0 ally increased with distance from the front of the-20-1~2 fairing, or simpler yet, a circular arc could be de-scribed between the front and the position of maximum height with the center of the arc selected to satisfy the maximum height tangency condition. Or, for fair-ings where ~ ~ h, the radius of curvature could begradually decreased to a value that preferably would not be less than about .1W.
Figure 13 illustrates several configura-tions that the plan view of the sides 94, 95, and 96 can assume. As before, convex, concave-convex, or a combination of these and straight portions can be used. The guide lines used in the development of these contours within the length, width, and tangency requirements for the side walls are the same as those suggested for the top wall. Since the side wall con-tours play an important role in achieving good yaw performance, it is desirable that the width of any flat portion 94' at the front of the fairing be small compared with the width of the rear of the fairing.
A consideration of plan view shapes that should be capable of providing adequate yaw performance sug-gests that it is desirable to have the plan view con-tour of the front and sides of the fairing lie wholly within a rectangular envelope 100, Figure 14 of length ~ and of width w that is intersected by a line 110 having one end point located .2w aft of one of the forward corners of the rectangle and the other end point located .2w inboard from the same forward corner, and another line 110' similarly located from the opposite forward corner. This envelope is 108~)82 sketched as dashed line 100 in Figure 14.
- The drawings herein of the ins~ant inven-tion have shown its top and sides to intersect along a sharp corner. Experiments have shown that rounding the corner provides improvements in performance when compared to the sharp corner case. The drawings have also shown the profile view of the rear of the fair-ing to be generally vertical; for example, as in ~ Figure 7. Experiments have demonstrated that useful performance increases can be achieved, particularly with fairings of shorter length, by tilting the plane of the rear of the fairing such that the rearward extremity 84' of the top wall in Figure 7 is dis-placed in the aft direction.
Finally, the drawings have generally shown the rear of the fairing in the same vertical plane as the back of the tractor. However, other mounting positions on the roof of the tractor may be used.
A rearward displacement of the fairing from the posi-tions shown in the drawings may be limited by the requirement that the device not interfere with the~ .
articulation of the vehicle. A forward dii~placement of the fairing from that position may be limited by a legal length requirement that would mean that the fairing could not extend further forward than the front of the tractor.
From the foregoing, it is seen that there is herein provided an improved device for reducing the aerodynamic drag on tractor-trailer truck com-binations. Though the discussion above was speci-~0~4~82 fically concerned with the use of the present inven-tion on articulated vehicles, it is to be understood that the device would also have application for re-ducing the aerodynamic drag on single-chassis truck/
van combinations. Similarly, the discussion was con-cerned with van type trailers. It is to be further understood that the device would have application in any situation where the height of the front wall of the trailing body was higher than that of the cab.
Finally, the discussion and illustrations have shown the plan view contour of the sides of the fairing to be symmetrical about the longitudinal axis of the fairing. While this is preferred in order to provide similar drag reductions at equal positive and negative angles of yaw, it is to be understood that significant aerodynamic drag reductions could also be achieved with use of asymmetric contours developed in accordance with the guidelines set forth earlier.
3o
Claims (31)
1. A fairing adapted to be mounted at the bottom portion thereof on the roof of the cab of a truck with the longitudinal axis of the fairing being parallel to the longitudinal centerline of the roof of the cab, the fairing being adapted to reduce aerodynamic drag at the front portion of a truck trailer positioned behind the cab of a truck and com-prising a nose portion disposed adjacent the front of the bottom portion of the fairing at the longitudinal axis thereof, the nose portion being adapted to be mounted adjacent the longitudinal cen-terline of the roof of the cab with the surface of the nose portion extending rearwardly with respect to the front portion of the roof of the cab, a curved top portion extending up-wardly from the nose portion and rearwardly with respect to the longitudinal axis of the fairing, the top portion diverging in width from the nose portion toward the rear of the top portion, the rear of the top portion extending transversely with respect to the longitudinal axis of the fairing and being adapted to be disposed above and adjacent the rear portion of the roof of the cab, each opposite end of the rear of the top portion being adapted to extend adjacent a different opposite extremity of the rear of the roof of the cab, the said top portion having a slope at its highest point which is substantially zero relative to the horizontal, and a pair of oppositely disposed side portions diverging with respect to one another, each side portion extending rearwardly with respect to the nose portion and generally vertically to the bot-tom portion of the fairing from a different opposite-ly disposed longitudinal extremity of the diverging top portion, each side portion terminating adjacent and below a different end of the rear of the top por-tion.
2. A fairing in accordance with claim 1 in which the nose portion is curved substantially with respect to the vertical axis of the fairing, the curved nose portion extending rearwardly from the intersection therewith of the longitudinal axis of the fairing to each of the side portions thereof.
3. A fairing in accordance with claim 1 in which the slope of the curved top portion relative to the horizontal decreases toward the rear of the top portion of the fairing.
4. A fairing in accordance with claim 1 in which the surface of the curved top portion in the direction of the width thereof extends substan-tially parallel to the transverse axis of the fairing.
5. A streamlined fairing adapted to be mounted on the roof of a cab portion of a land vehi-cle including a trailing body for reducing aerodyna-mic drag comprising, a bottom portion, a rear portion and a nose portion, and a continuous contoured surface extend-ing widthwise and upwards from said nose portion to said rear portion and having a top portion and side portions which abut at their respective boundaries, said top portion having at least a segment the tangential plane of which is inclined with respect to the horizontal at an angle which is less than or equal to approximately tan-1[2(H-h)/x] and greater than or equal to zero, where H represents the vertical distance from the roof of said cab por-tion to a top wall of said trailing body, h repre-sents the height of said fairing, x represents the distance between the rear portion of said fairing and the front of said trailing body, and h has a value greater than or equal to about .9H and less than H, and the said segment of said top portion being located furthest from the said bottom portion.
6. The fairing recited in claim 5, where-in said segment of said top portion is generally parallel to the horizontal.
7. The fairing recited in claim 6, where-in the ratio of the height h of said fairing with re-spect to the vertical distance H from the roof of said cab portion to a top wall of said trailing body is greater than or equal to about .9 and less than or equal to about 1.2.
8. In combination with a load carrying vehicle of the type having a cab portion and a van portion spaced rearwardly of the cab portion, said van portion having a front wall which has a larger frontal area than the frontal area of the cab;
drag reducing means mounted on the roof of the cab, said drag reducing means comprising a streamlined fairing having at least a top wall smoothly curved upwardly from a point on the center line of the top surface of the cab roof to a rearward position substantially equal to the height of the front wall of the van at which rearward position a tangent to the top wall is generally parallel to a top surface of the van and a pair of oppositely disposed side walls smoothly curved outwardly from a point on the center line of the top surface of the cab roof with upper extremities of the side walls being joined to outer extremities of the top wall, the side walls diverging outwardly with respect to each other toward said rearward position.
drag reducing means mounted on the roof of the cab, said drag reducing means comprising a streamlined fairing having at least a top wall smoothly curved upwardly from a point on the center line of the top surface of the cab roof to a rearward position substantially equal to the height of the front wall of the van at which rearward position a tangent to the top wall is generally parallel to a top surface of the van and a pair of oppositely disposed side walls smoothly curved outwardly from a point on the center line of the top surface of the cab roof with upper extremities of the side walls being joined to outer extremities of the top wall, the side walls diverging outwardly with respect to each other toward said rearward position.
9. The fairing recited in claim 5, further comprising a horizontal variable release angle tab hinged to said continuous surface of said fairing.
10. The fairing recited in claim 9, wherein said tab is hinged to said continuous surface near a rear horizontal edge of said fairing.
11. The fairing recited in claim 5, further comprising vertical variable release angle tabs hinged to said side por-tions of said fairing.
12. The fairing recited in claim 11, wherein said tabs are hinged to said side portions near rear vertical edges of said fairing.
13. A streamlined fairing adapted to be mounted on a roof of a cab portion of a load carrying vehicle for reducing aerodynamic drag, said vehicle including a van portion having front and side walls, said front wall of said van portion ex-tending above said cab portion, said fairing having a longitu-dinal axis and comprising:
a bottom portion, a rear portion, and a continuous contoured surface extending width-wise and upwards from said bottom portion at the front of said fairing to said rear portion, said surface having a top portion and side portions on either side of the longitudinal axis of said fairing which abut at their respective boundaries, said top portion having at least a substantially horizontal segment, a tangential plane of which is inclined with respect to the horizontal at an angle which is at least zero, said side portions diverging with respect to each other toward said rear portion and having substantially vertical segments which diverge with respect to the longitudinal axis of said fairing at an angle which is at least zero, and said substantially horizontal segment of said top portion being located uppermost with respect to said bottom portion and said substantially vertical segments of said side portions being located furthest from said longitudinal axis of said fairing.
a bottom portion, a rear portion, and a continuous contoured surface extending width-wise and upwards from said bottom portion at the front of said fairing to said rear portion, said surface having a top portion and side portions on either side of the longitudinal axis of said fairing which abut at their respective boundaries, said top portion having at least a substantially horizontal segment, a tangential plane of which is inclined with respect to the horizontal at an angle which is at least zero, said side portions diverging with respect to each other toward said rear portion and having substantially vertical segments which diverge with respect to the longitudinal axis of said fairing at an angle which is at least zero, and said substantially horizontal segment of said top portion being located uppermost with respect to said bottom portion and said substantially vertical segments of said side portions being located furthest from said longitudinal axis of said fairing.
14. The fairing recited in claim 13, wherein the height of said fairing from said bottom portion to said substantially horizontal segment of said top portion is approximately equal to the vertical distance from the roof of said cab portion to the top of said front wall of said van portion; wherein the width of said fairing between said substantially vertical segments of said side portions is approximately equal to the width of said van portion; wherein the axial length of said fairing is approximately equal to the length of said roof of said cab por-tion; and wherein said substantially horizontal segment of said top portion is disposed parallel to the horizontal and said sub-stantially vertical segments of said side portions are disposed parallel to said longitudinal axis of said fairing.
15. The fairing recited in claim 13, wherein said substantially horizontal segment of said top portion is inclined with respect to the horizontal at an angle which is less than or equal to approximately tan-1 [2(H - h)/x] and greater than or equal to zero, where H represents the vertical distance from the roof of said cab portion to the top of said front wall of said van portion, h represents the height of said fairing, x represents the distance between the rear portion of said fairing and the front of said van portion, and h has a value which is less than or equal to H.
16. The fairing recited in claim 15, wherein h has a value which is greater than or equal to about .9H and less than or equal to H.
17. The fairing recited in claim 13, wherein said fair-ing further comprises a horizontal variable release angle tab hinged to said continuous surface of said fairing.
18. The fairing recited in claim 17, wherein said tab is hinged to said continuous surface near a rear horizontal edge of said fairing.
19. The fairing recited in claim 13, wherein said sub-stantially vertical segments of said side portions diverge with respect to said longitudinal axis of said fairing at an angle which is less than or equal to approximately tan-1 [(W-w)/x] and greater than or equal to zero, where W represents the width of said van portion, w represents the width of said fairing between said substantially vertical segments of said side por-tions, and x represents the distance between the rear portion of said fairing and the front of said van portion, and w has a value which is less than or equal to W.
20. The fairing recited in claim 19, wherein w has a value which is greater than or equal to .5W and less than or equal to W.
21. The fairing recited in claim 19, wherein said fairing further comprises vertical variable release angle tabs hinged to said side portions of said fairing.
22. The fairing recited in claim 21, wherein said tabs are hinged to said side portions near rear vertical edges of said fairing.
23. The fairing recited in claim 13, wherein the length of said fairing is less than the length of said roof of said cab portion and greater than or equal to .2W, where W represents the width of said van portion.
24. The fairing recited in claim 13, wherein the height of said fairing, h, is less than the vertical distance from the roof of said cab portion to the top of the front wall of said van portion, H, and wherein h has a value which is greater than or equal to .8H.
25. The fairing recited in claim 13, wherein the height of said fairing, h, is greater than the vertical distance from the roof of said cab portion to the top of the front wall of said van portion, H, and wherein h has a value which is less than or equal to 1.4H.
26. The fairing recited in claim 13, wherein said top portion of said fairing comprises a continuous, convex con-toured surface.
27. The fairing recited in claim 13, wherein said top portion of said fairing comprises a continuous, concave-convex contoured surface.
28. The fairing recited in claim 13, wherein said side portions of said fairing comprise continuous, convex contoured surfaces.
29. The fairing recited in claim 13, wherein said side portions of said fairing comprise continuous, concave-convex contoured surfaces.
30. A streamlined fairing adapted to be mounted on a roof of a cab portion of a load carrying vehicle for reducing aerodynamic drag, said vehicle including a van portion having front and side walls, said front wall of said van portion extending above said cab portion, said fairing having a longitudinal axis and comprising, a bottom portion, a rear portion, a continuous contoured surface extending widthwise and upwards from said bottom portion at the front of said fair-ing to said rear portion, and side portions on either side of the longitudinal axis of said fairing which abut at their respective boundaries with said contoured surface, said fairing further comprising a horizontal variable release angle tab hinged to said contoured surface of said fairing, the height of said fairing being less than the ver-tical distance from the roof of said cab portion to the top of the front wall of said van portion.
31. The fairing recited in claim 30, wherein said variable release angle tab is hinged to said contoured sur-face near a rear horizontal edge of said fairing.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US65951776A | 1976-02-19 | 1976-02-19 | |
| US659,517 | 1976-02-19 | ||
| US76379677A | 1977-02-01 | 1977-02-01 | |
| US763,796 | 1977-02-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1084082A true CA1084082A (en) | 1980-08-19 |
Family
ID=27097840
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA271,302A Expired CA1084082A (en) | 1976-02-19 | 1977-02-08 | Drag reducer for land vehicles |
Country Status (8)
| Country | Link |
|---|---|
| JP (2) | JPS52123021A (en) |
| AU (1) | AU516306B2 (en) |
| CA (1) | CA1084082A (en) |
| DE (1) | DE2705702A1 (en) |
| FR (1) | FR2341476A1 (en) |
| GB (1) | GB1573255A (en) |
| IT (1) | IT1077273B (en) |
| SE (1) | SE432085B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4245862A (en) * | 1976-02-19 | 1981-01-20 | Buckley Frank T Jun | Drag reducer for land vehicles |
| FR2421785A1 (en) * | 1978-04-07 | 1979-11-02 | Etudes Realis Automobile | FAIRING FOR CABIN OF HEAVY TRANSPORT VEHICLES |
| JPS54175717U (en) * | 1978-05-31 | 1979-12-12 | ||
| JPS56132176U (en) * | 1980-03-10 | 1981-10-07 | ||
| JPS56136865U (en) * | 1980-03-18 | 1981-10-16 | ||
| DE10325346B4 (en) * | 2003-06-05 | 2006-05-04 | Daimlerchrysler Ag | Device for reducing air resistance |
| FR2900898B1 (en) * | 2006-05-09 | 2008-08-01 | Fabrice Paille | BODY AERODYNAMIC SHAPE HATTING A LOWER PORTION OF A DRIVING CABIN OF A ROAD VEHICLE FOR CARRYING GOODS |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3309131A (en) * | 1966-02-11 | 1967-03-14 | Saunders Walter Selden | Means for reducing linear wind resistance in single chassis type vehicles |
| FR1472450A (en) * | 1966-03-10 | 1967-03-10 | Device for reducing the wind resistance of a combination of tractor and trailer | |
| US3425740A (en) * | 1966-08-15 | 1969-02-04 | Marshall S De Vaughn | Streamlining apparatus |
| US3514023A (en) * | 1968-02-28 | 1970-05-26 | Fred D Russell | Rooftop carrier |
| US3695673A (en) * | 1970-09-11 | 1972-10-03 | James H Meadows | Air-flow diverter for tractor-trailer rig |
| US4006931A (en) * | 1974-09-11 | 1977-02-08 | Ford Motor Company | Device for reducing wind resistance of a vehicle |
| US3972556A (en) * | 1974-10-15 | 1976-08-03 | General Motors Corporation | Tractor-trailer aerodynamic drag reducer |
| US4018472A (en) * | 1976-02-04 | 1977-04-19 | General Motors Corporation | Tractor-trailer aerodynamic drag reducer |
| US4079984A (en) * | 1976-10-14 | 1978-03-21 | Powell Jack N | Wind deflector for a towing vehicle |
| JP2565184Y2 (en) * | 1993-04-26 | 1998-03-11 | 株式会社飯塚製作所 | Hydraulic jack for turnout |
-
1977
- 1977-02-08 CA CA271,302A patent/CA1084082A/en not_active Expired
- 1977-02-11 DE DE19772705702 patent/DE2705702A1/en not_active Withdrawn
- 1977-02-15 AU AU22306/77A patent/AU516306B2/en not_active Ceased
- 1977-02-15 FR FR7704263A patent/FR2341476A1/en active Granted
- 1977-02-15 SE SE7701650A patent/SE432085B/en not_active IP Right Cessation
- 1977-02-16 JP JP1509077A patent/JPS52123021A/en active Pending
- 1977-02-16 GB GB6526/77A patent/GB1573255A/en not_active Expired
- 1977-02-18 IT IT20441/77A patent/IT1077273B/en active
-
1985
- 1985-06-17 JP JP1985090206U patent/JPS6115681U/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE2705702A1 (en) | 1977-09-01 |
| SE7701650L (en) | 1977-08-20 |
| JPS6115681U (en) | 1986-01-29 |
| JPS52123021A (en) | 1977-10-15 |
| SE432085B (en) | 1984-03-19 |
| FR2341476B1 (en) | 1982-11-12 |
| FR2341476A1 (en) | 1977-09-16 |
| AU2230677A (en) | 1978-08-24 |
| AU516306B2 (en) | 1981-05-28 |
| IT1077273B (en) | 1985-05-04 |
| GB1573255A (en) | 1980-08-20 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |