US2675670A - Pulse jet engine havingf variable - Google Patents

Description

April 20, 1954 w. TENNEY I 2,675,670 PULSE JET ENGINE HAVING VARIABLE INLET CONTROL Filed May 15, 1948 2 Sheets-Sheet 2 INVENTOR. lMLL/AM L. TZ-WNEY w a E Q u A z a m E w M m .5 7 x a MM m /m m B I g \Lf) E w W5 v 6 4d m E I E 1 m7 M #w 7 E i ATTORNEYS Patented Apr. 20, 1954 UNITED. STATES PATENT OFFICE PULSE JET ENGINE VARIABLE" INLET CONTROL 4 Claims.

This invention relatesto pulse jet engines and more particularly to intake controls therefor. In jet engines of this character air is introduced at the forward end of the engine into a com bustion chamber which may be merely a forward section of the jet tube. Fuel is likewise introduced into the combustion chamber or section and the combustible fuel-air mixture is exploded therein. The resultant products of combustion and any augmentation air which may have been drawn into-the open end of the exhaust tube are ejected forcibly from a rearwardly' extending tail pipe or jet nozzle and thus produce the thrust effort of the engine which serves to drive it and its load in a forward direction.

The frequency of the explosions in the unit depends primarily upon the length and other physical dimensions of the combustion chamber-tailpipe assembly. In small engines suitable for the propulsion of model airplanes, boats, cars and the like, the frequency of the explosions are in the. order of 200-300 cycles per second, whereas in larger units such as are suitable for the propulsion of target airplanes, guided missiles and the like, the explosion frequency is lower.

The operation of pulse jet engines is exceedingly critical in that even slight and almost negligible variations in the physical constants and operating conditions cause substantial and largely unexplained variations in thrust, fuel consumption and the like. Such theory ashas been advanced to explainv such phenomena as (l) re-ignition without sustained external ignition apparatus, (2) frequency of explosion, (3) variation in thrust and fuel consumption with changes in speed and altitude and. other factors, is largely speculative and for the most part unsubstantiated. Such progress as has been made is based primarily on experimentation, using the trial and error method.

In my experiments it has been discovered that thrust, fuel economy and indeed, even the maintenance of the cyclic; explosive phenomena is considerably dependent upon the rate of intro-- duction of the air component of the combustion mixture into the combustion chamber. Thus, utilizing a pulse jet engine of the general design described in copending applications Serial No. 649,882 filed February 25, 1946, now Patentv No. 2,609,660, and Serial No. 661,280 filed April 11, 1946, now Patent No.. 2,587,100, itlhas been found that when the unit is standing still andv hence is not receiving any ram air, certain thrust and specific fuel consumption are obtainable, yet

when the same unit is permitted to obtain an appreciable velocity or is subjected to variations in air pressure within the range of atmospheric variations, relatively substantial decreases in thrust and fuel economy ensue. The same phenomena hold true for larger size units which I have? tested. In extreme instances the effect of velocity and pressure variations may be so pronounced that the unit ceases to function in that.

cyclic operation does not continue. It has also been observed that as the: velocity increases with wide open: intake, the zone of combustion as indicated by most pronounced heat liberation, shifts towards the exhaust end of the jet tubes.

In seeking to overcome these objections I have discovered. that theconditionof maximum thrust and minimum specific fuel consumption can be better maintained under varying conditions of velocity and atmospheric pressure (or altitude) by varying the restriction at the air intake throat, and it is an object of the invention to provide for such variation.

More specific objects of the invention include provision of mechanisms in pulse jet engines for adjusting the air intake for various conditions; to provide-a pulse jet engine wherein the throat restriction. is adjusted automatically in response to speed. or in response tothe joint action of speed and altitude and to provide an improved pulse jet engine having means for manually adjusting the air intake either at the intake itself by the use of variousforms of restrictions or remotely controlled.

Other and further objects of the invention are those: inherent in. the apparatus herein illustrated, described and claimed.

The invention is illustrated with reference to the drawings wherein Figure 1 is a sideview of a pulse jet engine, partly in section, showing; one form of adjustable intake;

Figure 2 is a side view of a pulse jet engine, partly in section, showing asecond form of ad, justable intake which is automatically responsive to velocity;

Figure 3 is aside view of a pulse jet engine, partly in section, showing a third form of adjustable intake, which is capable of manual ads justment";

Figure 4: is a side view of a pulse jet engine, partly section, showing a fourth form of adjustable intake which is automatically responsive to variations velocity and altitude (barometric pressure-) Figure 5 is e side view of a pulse jet engine,

partly in section, showing another form of adjustable intake;

Figs. 6 and 7 are side views partly in section showing modified forms of exhaust tube.

Throughout the drawings the combustion chamber and jet tube (or exhaust tube, as it is sometimes designated) are foreshortened so as to afiord a larger scale for illustration of the intake end of the several engines which are the principal subject of the invention, but it will be understood that the combustion chamber and exhaust tube are of appropriate length, suitable for the service involved. In use the devices shown in the drawings produce a thrust and tend to move from left to right. The portion on the right in each figure is accordingly referred to as the forward end, portion or direction. The portion at the left is the rear end, portion or direction.

Throughout the drawings corresponding numerals show corresponding parts.

Referring to the drawings the basic engine is illustrated in Figures 1 through and consists of a combined combustion chamber and jet exhaust tube 10 which is provided at H with a valve or valve bank of any suitable design capable of permitting the flow of air or a fuel-air mixture therethrough cyclically according to valve operation and in the direction indicated by the arrows l2. The valve bank Il may be of any suitable design such as that illustrated in Patent No. 2,609,660, or application Serial No. 661,367 filed April 11, 1946, now-abandoned. The valve mechanism in the illustrative structure herein is shown as being mounted in a bulkhead wall !3 and spaced from the interior surface of the combustion chamber and exhaust jet tube 10 so as to provide an area through which fuel jet nozzles 14 protrude. The nozzles M, of which a plurality are used, are oriented so as to provide a spray discharge towards the central area downstream from the valve bank II, the spray discharge of the nozzles being illustrated at I5. The fuel thus introduced into the combustion chamber mixes with the infiowing air stream which enters through the valve bank II and provides an explosive mixture which is exploded cyclically in the operation of the device. The plurality of nozzles I 4 are connected together by a ring header-tube 16 which circumscribes the valve bank I I. At one point a fuel supply line is connected to the ring, as indicated at l8. Fuel under pressure is pumped to the header ring l6 from an external supply.

Other fuel injection mechanisms, such as those illustrated in the aforesaid Patent No. 2,609,660,

may be utilized, if desired. Likewise one or more valve banks, such as those illustrated in said application may be utilized at H.

The tube l0 not only forms the combustion chamber but also forms the jet exhaust tube of the device and may be of uniform diameter throughout or may, if desired, have a larger diameter adjacent the valve bank as shown in Fig. 6 so as to form a combustion chamber which is then connected by an intermediate section of smaller diameter to the terminal end 20 which may, if desired, be flared as illustrated at 2|. The tube I0, if desired, may have a gradually increasing diameter towards the terminal end followed by a reverse curve similar to a wine goblet section as shown in Fig. 7 so as to provide for supersonic jet velocities of jet exhaust.

The intake section generally designated 22 has a smooth interior Venturi curved section 23 having a minimum diameter at 24 which is smoothly 4 curved to the entering or nose section 25. The exterior surface 26 is preferably kept as free as possible of protuberances so as to cut down parasitic drag where the unit is used in free flight as in a guided missile, but where the unit is housed the housing is shaped so as to provide the least parasitic drag. This much of the construction is uniform throughout the various figures in the drawings.

In the operation of a device of this character air enters at the forward end 25 at a velocity depending upon the engine design and condition of operation, as well as the forward motion of the unit. After entering through the Venturi nozzle 24 the air or fuel-air mixture, in the event the fuel is introduced in the nozzle section 22, impinges upon the valve bank II or other suitable inlet section and passes into the combustion section which is the portion of tube 10 immediately downstream from the valve bank I I. Initially ignition is accomplished from an external source such as by means of a spark plug 28. As soon as the combustible mixture is ignited the pressure developed in the combustion zone forces the products of combustion in the forward portion of the tube and the fresh air mass in the rear portion of the tube rearwardly through the tube I0 and out of the terminal end 20 as indicated by the arrows 29. The explosion likewise causes the valves of the valve bank II to close until the pressure of the explosion has subsided. Even when the unit 22 is static, that is to say it has no forward velocity, the rearward flow or mass action of the gases moving in the direction of arrows 29 produces what is apparently a negative pressure condition in the combustion zone (to the left of the valve bank I l as shown in the figures), and this causes a fresh flow of air or airfuel mixture to be drawn through the valve bank I! whereupon the second explosion occurs. A negative pressure also occurs at the rear end of tube l0, causing a flow of fresh air back into the rear portion of the tube through the terminal end 20. This action is repeated cyclically and soon after operation begins the high tension supply to the spark plug 28 is interrupted and re-ignition occurs thereafter due to the inherent functioning of the apparatus. The zone of most intense heating is somewhat removed to the left from the valve bank I I, since the fresh inflow of air or fuel-air mixture through the valve bank ll serves to cool the valve bank and somewhat to lower the temperature of the region immediately adjacent thereto, and the cyclic fresh air influx through the terminal end 20 tends to cool the region adjacent thereto.

When the device is moving rapidly through the atmosphere the air flow through the venturi 24 increases due to the ram air effect, and it has been observed that the zone of most intense heating or combustion moves farther and farther away from the valve bank towards the outlet of the jet tube 26 as the ram air effect increases. A decrease in barometric pressure has an opposite eifect for while the velocity of the incoming air flow may be increased the decrease in barometric pressure has the effect of decreasing the incoming mass of air. Therefore, to some extent an increase in velocity is counterbalanced by a decrease in barometric pressure, though not in equally compensating amounts.

As the ram air or velocity effect increases the thrust afforded by the engine decreases and the specific fuel consumption, in pounds of fuel per pound of thrust per hour, increases. I havediscovered that by valving he Ven tufi tube section 24, this decrease in thrust and increase in *iZue'l consumption can be partially or completely counteracted, depending upon other -operating conditions and details of engine designand as a result the unit prov-ides improved thrust and fuel econonly as-oompared with previous pulse gle't engines.

In Figure 1 the Venturi section is provided with a'frame composed of two or more forwardly and inwardly curved struts 3% which are joined together by a streamlined nose section 3| which serves as a central support for the forward end of the rod 32, the rear end 33 of which is'attached to the valve ban-x. Upon the rod-there is mounted an object which has a streamlinedsur-faceSpresenting the comparatively blunt-nose portion 34, a maximum diameter section 35 and the long tapered end section 3%. This object generally designated. 37, which may be termed a Venturi flow restrictor, is mounted so as to be-movable forward or back upon the rod 32 and since the rod 32 is mounted at the longitudinal axis of the Venturi section 2-4, the flow restrictor 3! may thus be adjusted so as to be at any 'posi. tion from the forward (least restricting) position shown by dotted'lines 37 to the rearward (most restricting) position shown in full lines. In the forward position the blunt nose section 34 fits neatly within the correspondingly curved surface 3% of the central nose '31. The flow 'restrictor is provided with one or more set screws or other fastening devices at 39 by'which its position may be fixed by manual adjustment so as to be located anywhere along the rod 32. In this form of the invention the restrictor is adjusted at any position so as to provide maximum thrust and minimum fuel consumption for any desired speed or barometic operating conditions.

Referring to Figure 2 there is illustrated another formof the device of generally similar construction except that in this form the flow restrictor, generally designated 40, is mounted so as to be automatically movable between 'fixed least-restricting and most-restricting positions with reference to the Venturi section 2t. flow 'restrict'or to is internally boredat II and is provided with a web at 2 having an aperture therein sized so as to slide neatly upon the 'rod '32. The front end of the bore l'l'is provided with a screw-in plug 43 which is likewise apertured so as to slide upon the rod 32. The rear end of the restrictor 46 has bore '44 in which the long cylindrical stop member 65, which is fixed to the rod .32 by means of set screw 46, is adapted to slide. The member 65 is fixed upon the shaft 32 and the restrictor iii slides thereon from the position shown in full lines to the position shown in dotted lines. It will be noted that in the dotted line position the trailing edge 41 of the restrictor is still supported on the forward end 48 of the stop member 45. When the web 42 is against the front end of the stop member 45, the flow restrictor 50 is in the most restricting position. Upon the rod 32 there is provided a collar 5'6 which is held in any adjusted position on the rod by means of a set screw 5|. The collar 50 serves as a stop. for the spring 52, the forward end of which pushes against the screwin plug #3. Spring 52 is shown compressed in Figure 2 and the force exerted by it upon the plug 43 is in the forward direction. Thus, the spring 52 naturally tends to expand and to force the entire flow restrictor Ali to the forward or dotted line position til, in which the flow restrictor resides when the device i in static con- The acme-to dition. In this pesi tion thenumoer Wt 'is finfth least-restricting condition.

As velocity of the engine increases the ram air pressure exerted upon "the forward end of the flow restrictor Ml, indicated by the arrows =51, gradually increases "until it is sulii'cierrt to over come the force-of spring 52 and a the velocity increases the' flow restrictor M1 is gradually pushed back until it reaches "the position shown in full iines in which a maximum restricting edect thej fiow'through ti-re 'ventur i 23 is achieved. will be noted passing the force exerted by the ram air upon the flow restrictorlll decreases as the barometric pressure decreases (clue to the lesser density of the air) while the force producedin the direction of arrows at increases for increases of velocity. Decrease in'barometric pressure as is occasioned by high altitudgffli partially *but not entirely compensates the mcrease in velocity. The position 'of member l'il moves to compensate for variation in speed and barometric "pressure -=during operation. Referring to Figure 3 there is illustrated "a device corresponding to that shown in "l ligure 2, except that the underside of the "flow restrictor notched at 56 to receive an actuating link 51-wh=ich is 'connectedto the flow 'restr'ictor by the pivot-pin 5B. The 'rear end of the actuating link is pivotally connected at 5-9 to the lever cue men extends through a slot "6| in the-sideof the venturi *22, the lever 60 being pivoted at 62 'to' -the Venturi'inlet structure. At 63 there is illustrated a housing which may be part of the air 'r'ciilor other structure into which the engine unit is built and upon this portion of "the device there is mounted a pull wire control bracket "64 which serves to hold the housing "65 of the pull wire which extends to a remote operating station '6'6. An operator control 6"! is connected to "the wire 68 that extends through the housing 65 and is Divotally connected at 69 to the lever 69. By movement of the operator control 67 in therearward direction, as indicated by the arrow f'l'll, the restrictor can thus be moved in the forward direction for static operation or operation at low velocities. As the velocity increases DI" when other'conditions require an adjustment of the now through "the venturi 22, the operator control '6"! is pulled 'or pushed and the flow restri'ctor .4? is accordingly moved to "any desired position from fully open (unrestricted flow conditions shown at 40') to the maximum restriction position shown in full lines in'Fig'ure 3. I In Figure 4 the apparatus of Figure 3 is shown slightlymodified in that a greater range of motion is provided for the 'flow restrictor 4-0. This is'afiorded by extending the braces 30A to a more forward position so as to provide a longer rod 32A on'which the flow restrictor is adapted to slide. The movement of the flow restrictor i!)- is of the same type as that described with reference to Figure 3, "but the range is greater, this being alforded by the lever 60A which is-mountedupon a bracket H extending outwardly from the outer surface of the "Venturi nozzle section '22. f The length of the s'lotBiA, link 51A1w'hich is pivoted to both the flow'restrictor and to the lever 60A, and the length of thelever 60A are all proportioned accordingly. As a result the flow restrictor may be moved from the least-restricting position shown in dotted lines to the position of maximum restriction of the Venturi tube shown in full lines.

The full range of movement is accomplished by means of a mechanism generally designated 72'whlch is automaticallyresponsive to velocity and barometric pressure changes. Thus, within the housing 13 shown in dotted lines merelyas representative, upon which the engine unit is mounted, there is provided a bracket 14 having an annular bellows chamber 15 which is con nected by the tube 83 to an open-ended air inlet funnel 81. The bellows section '15 is closed at its forward end by the plate 15 to which there is likewise attached the forward end of a baroe metric Sylphon bellows containing a puregas 11. The rear end 18 of the barometric Sylphon bellows 11 is pivotally attached at 19' to; -a lever-80 which is pivoted at 8| to the bracket 82 on the unit 13. The upper end of the lever 80 which is a motion multiplying lever is attached at 84 to a link 85 which is pivotally attached at- 86 to the lower end of the leverBOA. A spring 89 is attached to the mounting panel 14' andto the pivot 86 and accordingly tends to pull-the link 88 and the lower end of lever 60A in the rearward direction as indicated by the arrow 89. This tends to push the flow restrictor 40 to the dotted line position. If it is assumed that the flow restrictor is in an intermediate positiondue to a steady pressure exerted through tube 93; upon the interior of annular bellows section 15, then the effect of a decrease in barometric pressure will be to expand the bellows TI and to push the lever 80 in the direction of arrow 90. This tends to push the flow restrictor 40 toward the dotted line position. If the velocity of the unit increases greater pressure is exerted in the direction of arrows 90, and this tends to increase the (ii: mension W of the annular bellows section 1 5. This has the effect of pulling the lever in the direction of arrow 9! and tends to move the flow restrictor 40 toward the full line position. If desired, a servomotor system may be incorporated in the linkage between the actuator '12 and the flow restrictor 40 so as to increase the power for moving the flow restrictor, particu larly in larger size units. A

In Figure the Venturi nozzle section 22 an the remaining portions of the engine are equipped with two or more forwardly extending ribs 92 which converge together at 93 and serveas a support for the forward end of the rod 3213. Upon the rod there is mounted a flow restrictor generally designated 100 which has a smoothly: curved converging forward end 94 and a fiat planar or undercut trailing edge 95. This flow restrictor may be undercut as shown by the 'dotted' lines 96 so as to reduce weight. The flow restrictor is provided with a set screw 91 by means of which it may be adjusted in any position from the forward full line position to a position closer to the nose 25 of the venturi. When the flow restrictor is in the forward or full line position shown Figure 5, the air flow therearound is as indicated by the full line arrows l0l. When the flow restrictor is in a position more closely adjacent the nose 25 and the venturi 22, the flow is restricted to a greater degree and is in the direction of the dotted line arrows I02. Any degree of restriction may thus be achieved'by adjusting the position of the flow restrictor I00. I

As many apparently widely different embodi- '8 ments' of this invention maybe-made without departing from the spirit and scope thereof, '-it is to be understood that I do not limit myself to the specific embodiments herein. 7

What I claim is: r e

1. A resonant pulse jet engine having a combustion zone enclosure with interior walls constructed for the rapid pulsating flow of gases therethrough and asubstantially unrestricted jet exhaust tube emanating therefrom and having a cross section not substantially less than that ofthe adjacent end of said combustion chamber, said engine also having an automatic valve operable by and in direct timed relation with the resonating pulsations of said engine, a Venturi shaped inlet into said combustion zone enclosure, said inlet being orientated to face in the opposite direction from said jet exhaust tube, said automatic valve being located in said inlet passage, means for introducing air and fuel into said combustion zone enclosure for resonant periodic selfsustaining combustion within said combustion chamber and said exhaust tube, an inlet passage restrictor in the shape of an air foil surface of revolution closed to the passage of air therethrough, means mounting said restrictor substantially coaxially of the Venturi inlet passage and for movement to varying positions with refer-- ence to the end of said passage for varying the restriction to air flow through said passage to control the quantity of air supplied to said engine to maintain said self-sustaining combustion therein under varying conditions, and means normal- 1y biasing the movement of said restrictor to a position least restricting said Venturi passage.

2. The apparatus of claim 1 further characterized in that stops are provided on the means mounting the passage restrictor for limiting its movement at positions of selected minimum and maximum restriction of said Venturi passage.

3. The apparatus of claim 2 further characterized in that said passage restrictor is mounted for movement under the effect of ram air impinging thereon and said means for biasing has an inherent strength insufficient to maintain said passagerestrictor in the least restricting position when the ram air pressure reaches a predetermined amount.

4. The apparatus of claim 1 further characterized in that means is provided connecting said passage restrictor to a remote control for manually varying the position of said passage restrictor from said remote station.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1 2,142,601 Bleecker Jan. 3, 1939 2,390,161 Mercier Dec. 4, 1945 2,396,598 Neumann et al Mar. 12, 1946 2,489,953 Burney Nov. 29, 1949 2,570,629 Anxionnaz et a1 Oct. 9, 1951 FOREIGN PATENTS Number Country Date 50,033 France Aug. 1, 1939 Addition to No. 779,655

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