US3178100A

US3178100A - Fan

Info

Publication number: US3178100A
Application number: US168065A
Authority: US
Inventors: Datwyler Gottfried
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-01-25
Filing date: 1962-01-23
Publication date: 1965-04-13
Anticipated expiration: 1982-04-13
Also published as: CH391947A

Description

A ril 13, 1965 G. DATWYLER 3,178,100

FAN

Filed Jan. 23. 1962 F/GJ PRIFSSURE F20 VEZOC/T) 3' DEVELOPED ROTOR PER/PHERY 5 |NVENTOR GOTI'F/P/[D DA'TWYLER BY AMMWC W ATTORNEYS Ed'lhjhh Patented Apr. 13, 1965 savanna FAN Gottfried Diitwyler, Dahliastrasse l6, Zurich, Switzerland Filed Jan. 23, 1962, Ser. No. 168365 Claims priority, application Switzerland, Ian. 25, 1961, 875/61; Aug. 15, 1961, 9,568/61; Get. 17, 1961, 12,013/61 1 6 Claims. (Cl. 230-425) This invention relates in general to fan constructions and in particular to a new and useful fan construction in which the fluid fiow through the rotor is transverse to the rotor axis. The fluid is drawn in from one side of the rotor and passes in a direction transverse to the rotor for discharge at the opposite side.

The present invention is particularly directed to a type of fan in which the fluid is drawn in from one side of the rotor and passed in a direction transverse to the rotor for discharge at the opposite side. Fans of this type are suitable for many special applications. A wide practical use for a fan of this character, however, has been limited by the pressure volume curve inherent in the construction of fans of such type which are presently known. It is a characteristic of the operation of such presently known fans that a maximum pressure occurs at an intermediate value of mass flow and the pressure falls off with increasing mass flow and falls oif particularly sharply with a decreasing mass flow.

It is generally recognized that a pressure drop with increasing mass flow is a phenomenon common to all turbo blowers or fans of this character. However, the pressure drop which results with a decreasing mass how, that is, in the region below the mass flow for the maximum pressure, is a serious drawback particularly since with increasing back pressure and a corresponding decrease in mass flow, the pressure collapses. With rotary fans of a type referred to as Sirocco fans, the pressure increases steadily toward zero mass how and this characteristic is desirable in a fan in which the fluid flow is transverse to the axis of the rotor and which is the fan of a type which is the subject matter of the present invention.

The undesirable characteristics of cross flow fans of the type with which the present invention is concerned makes it virtually impossible to operate two or more such fans into a common pressure chamber because at mass flows below the point or" maximum pressure the pressure of one of the fans may collapse and the flow through this fan will reverse.

Various constructions of fans have been proposed to improve the operating characteristics of such fans. In cross flow fans, it is known that a whirling vortex is produced which has its center inside the fan rotor and which rotates in the same sense as the rotor. In the transverse tans known prior to the present invention, the center of this vortex approaches the center of the rotor with increasing back pressure, and thus the pressure produced by the fan decreases with low mass flow values. To augment the pressure at small flow volumes, it has been attempted to stabilize the position of this vortex near the inner periphery of the rotors by one or more pockets, bulges or recesses in the casing wall. The attempts to halt the drop in the pressure volume curve at low mass flow either have not been successful, or very complicated and expensive casings have resulted.

In accordance with the present invention, there is provided a fan construction in which fluid is arranged for cross flow movement in respect to the axis of the rotor and wherein the fan operates to produce an increase in pressure at decreasing flow values. The construction includes a casing showing, in any plane normal to the longitudinal axis of the fan, an outwardly curved volute as an outer wall and an S-shaped, or smooth ogee surface, inner wall which curves towards the outer wall. The construction further includes a rotor with forwardly curved blades, this rotor turning between the two casing walls and dividing the fan into a low pressure, intake, or suction side and a high pressure, outlet, or discharge side, both casing walls extending parallel to the rotor axis for the full length of the rotor.

The open arc of the rotor periphery between the casing walls at the intake side, in accordance with the present invention, is less than the open arc of the rotor periphery between the casing walls at the outlet side. An essential feature of the present invention is that the contour of the outer casing wall turns through an angle of more than from the beginning of the wall, adjacent the rotor periphery at the intake side, to the outlet side of the fan. This causes the flow between the intake and discharge sides and contained between the inner and outer casing walls and going through the rotor, to be deflected by an angle in excess of 130 in any plane normal to the rotor axis.

In a cross flow fan construction embodying the present invention, the flow in the outlet or discharge side of the fan, in any plane normal to the axis of the fan rotor, has a stagnation or resting point on the S-shaped inner casing wall. At this stagnation or arresting point, the fiow is stably divided into a first portion, which flows out through the outlet as net, useful mass flow of the fan, and a second portion flowing back into the rotor. This latter circulatory flow back into the rotor is due to the vortex which, in the present construction, has its center located always near the circle described by the inner edges of the rotor blades, and lying some distance away from the cut-off edge of the S-shaped inner casing wall which is opposed to the direction of rotation of the rotor.

Accordingly, it is an object of this invention to provide an improved cross fiow fan construction.

A further object of the present invention is to provide, in a cross flow fan, an inner, S-shaped, or smooth ogee surface, wall of the casing approaching the rotor periphery in a direction essentially tangential to the rotor and in opposition to the latters direction of rotation. This inner, S-shaped wall ends in a thin cut-0d edge, just referred to, which extends parallel to the rotor axis.

A further object of the invention is to provide a fan which is simple in design, rugged in construction and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.

In the drawings:

FIG. 1 indicates pressure volume curves for prior art fan constructions and for a fan constructed in accordance with the invention;

FIG. 2 is a somewhat schematic transverse section of a fan constructed in accordance with the invention;

. FIG. 3 is a somewhat schematic transverse section of another embodiment of the invention;

FIG. 4 is a curve indicating a part of the flow velocity into the rotor along a part of the periphery of the latter in the region of the cut-off edge of the inner casing wall; and

FIG. 5 is a somewhat schematic transverse section of a further embodiment of the invention.

' formance.

As indicated in FIG/1, the curve marked I illustrates a pressure volume curve of a cross flow fan (a fan in which the flow is transverse to the axis of the rotor) of a type known at the present time. This curve has a pressuremaximum at a certain mean mass flow. The curve shows clearly the pressure drop at a mass flow below the one corresponding to the maximum pressure and also indicates that with reduced mass flow the pressure drops to a very low value.

The curve marked II shows the characteristic pressurevolume curve, of a radial blower (Sirocco blower) where the pressure does not drop with decreasing mass flow but rather remains constant with some. tendency to even rise towards no flow.-

The curve indicated III shows the characteristic be havior of a cross flow fan constructed inaccordance with the invention. As indicated, the pressure does not drop with'small mass flow values, but increases appreciably as a no flow condition is approached. 7

Referring to theother drawings, as indicated in FIG. 2, the invention embodied therein includes a fan which has an outer casing wall 1 and an inner casing wall 2 betweenwhich is rotatably mounted the rotor, generally designated 3, and having an axis of rotation indicated at 4. The outer casing wall 1 is anoutwardly curved volute beginning at the point 5 near therrotor periphery,

while the inner casing wall 2 is S-shaped, or has a smooth ogee surface, begins at the point 6 near the rotor periph ery, approaches the rotor periphery in an essentially tangential direction, and points toward the rotor in a direction which is opposite to the'latters direction of rotation. i

The center of the vortex 7 inside of the rotor is designated by :7, and the stagnation point on the S-shaped inner casing wall 2 is designated at 8. Stagnation point 8 lies near the point of inflection of the S-shaped wall.

The flow lines drawn in this figure exemplify the flow as

Points

5 and 6 are defined by described previously. the two oasing'walls, near the rotor periphery, and limit or define the termination area of the high pressure portion or outlet 9 and the low pressure portion or inlet 10. In accordance with the invention, the casing is thus configured to. enclose an are, at the periphery of the rotor on the high pressure side 9, which is more than 180 as indicated by the angle a. In the embodiment illustrated inFIG. 2, angle or is about 220 and the rotor periphery or circumference exposed on the low pressure side 10 is about 140. 7

The part of the rotor circumference onthe high pressure side 9 is thus always larger than the part of the rotor circumference on. the low pressure side 10. The optimum value for the high pressure side part of the rotor circumference lies between 220 and 270.

The outer wall 1 of the rotor casing is shaped to define a volute which is outwardly curved. Its contour, beginning at point 5 near the rotor periphery, turns through an angle of more than 130 degrees as it approaches the outlet of the high pressure side of the casing.

In FIG. 2, a generated whirling vortex 7 is indicated by the flow lines with arrows, which vortex has a center indicated at7. This center lies inside the rotor 3, and contrary to prior art casing constructions whichmay include bulges, forexample, the vortex center is not confined to any particular part of the casing but can move freely in the high pressure portion 9 and adjust itself as to intensity and location to the flow pattern which prevails in the fan depending upon the operating conditions of the latter.

. The fan construction as set forth in FIG. 2 not only produces a fan characteristic as indicated by the curve 111 in FIG. 1, but also gives a considerably higher fan per- Inaddition, a diffuser which is usually employed at a location following the high pressure outlet can be dispensed with, permitting the size of the casing to be reduced. The velocity distribution at the high pressure outlet is more uniform. The increased performance 4 of a crossflow fan constructed in accordance with the present invention permits its application beyond the field of ordinary use in such applications, for example, as turbo machines and gas turbines and supercharger applications.

The tendency of the vortex, often found in cross flow fan designs, to extend toward the outlet of the high pressure side and thereby leading to adverse pressure gradients on the inner casing wall with flow reversal there and pressure pulsations, is eliminated in the fan of the present invention by the S-sh'ape of the inner casing wall 2, wherein the flow can establish a stable stagnation point 8 where the flow stably separates into the portion that flows out into the outlet as net and useful mass flow of the fan, and into a portion which flowsback into the rotor. In addition, the'flow in the high pressure side 9 may be guided by a guiding element 11, such as shown in FIG. 3 in which a crossflow fan with a casing 1 of a fan is provided with the general configuration indicated in FIG. 2.

This guiding element, for example, a guide vane, helps to direct part of the flow towards. the stagnation point 8 and toward the rotor 3 to'further stablizethe position of the vortex 7 for various operating conditions of the fan.

By the means previously described,'the pressure'produced by the fan, particularly at small mass flow values,

is increased considerably over the vortex intensity of rotor cross flow fans. In some cases, however, strong velocity gradients are present in the flow directed back toward the rotor on both sides of the S-shaped inner casing wall 2 toward the thin cut-ofi edge 6 of the latter. From such velocity gradients, through which the blades of the rotor turn, a noise such as produced by sirens may result. Such noise is undesirable and any tendency thereto is suppressed by a further development of the invention.

In FIG. 4is shown a flow velocity diagram for the various stream lines before their entrance into the rotor from the cut-Olfedge 6 of the S-shaped inner casing wall 2. The development of the rotor periphery is indicated in the direction R. The curve A indicates the condition for a fan according to FIG. 3. The shaded part of this curve indicates the wake on both sides of the S-shaped inner casing wall 2 of FIG. 3, with a pronounced downward dip a. Also, in its overall aspect, the curve A indicates in the mean a strong positive velocity gradient. Curve B, on the other hand, shows a much lower gradient with only a weak wake b which is produced as a result of the construction in accordance with the further developmen to be described with reference to FIG. 5.

In FIG. 5, a double wall construction for the S-shaped inner wall is shown which includes an outer volute casing wall 1 and the double S-shaped inner wall designated 13. Between the outer and inner casing walls 1 and 2 a rotor 3 is rotatably mounted. A double inner wall construction is formed by the S-shaped wall 13 on the high' pressure side 9 and by an S-shaped wall 12 on the low pressure side 10. These walls, 12 and 13, the inner one 13 acting as guiding element of the flow, define a channel K opening into the high pressure side 9. Arrow 14 indicates the direction of rotor rotation.

While specific embodiments of the invention have been shown and described in detail to illustrate the application I of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. A fan comprising a rotor having axiall extending blades, said rotor having affluid flow peripherally outwardly therefrom, a casing about said rotor including a pair of spaced axially extending walls, said walls defining a suction chamber and a high pressure discharge chamber circumferentially disposed about the periphery of the rotor, said rotor having its periphery on the discharge side exposed in excess of degrees, one of said walls having a projection adjacent the periphery of the rotor and extending in a smooth spiraling surface outwardly and away charge end, said second wall being a common wall between said suction chamber and said high pressure chamber, said second wall being shaped as a smooth ogee surface, one end of which is adjacent the periphery of the rotor and said ogee surface terminating in said one end in a plane substantially tangential to the periphery of the rotor, and the said ogee surface terminating in a discharge end oppositely from the discharge end of said first Wall to define a restricted outlet therewith from the casing, said tangential portion of the ogee surface cooperating with the fluid flow thereover to define a reverse flow vortex adjacent the periphery of the rotor and eccentrical thereto, said reverse flow vortex cooperating with the flow from the suction chamber to induce flow into the periphery of the rotor.

2. A fan according to claim 1, including wall means adjacent said common second wall, said common second wall converging toward said wall means, in the direction of flow therehetweeu, to decrease the cross section of the flow area from the point of substantial rotor tangency of said common second wall toward the fan discharge side.

3. A fan according to claim 1, wherein the casing is arranged so that the open part of said rotor circumference on the high pressure side is between 220 to 270.

4. A fan according to claim 1, including a channel forming element disposed in the casing high pressure side arranged to guide the fluid flow in a direction toward the rotor.

5. A fan according to claim 1, wherein said casing includes a double wall construction separating said suction 6 and discharge chambers, which double wall construction opens at least toward the rotor periphery.

6. A fan according to claim 5, wherein the walls of said double wall construction are of different length, with the inner wall being shorter than the outer wall and permitting flow in said high pressure chamber backwardly through said double wall construction toward said rotor.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Centrifugal Pumps and Blowers, by Austin H. Church, pages 19-20, 118-128, 1944.

German printed application 1,070,337, Dec. 24, 1959.

KARL J. ALBRECHT, Primary Examiner.

JOSEPH H. BRANSON, JR., LAURENCE V. EFNER,

Examiners.

Claims

1. A FAN COMPRISING A ROTOR HAVING AXIALLY EXTENDING BLADES, SAID ROTOR HAVING A FLUID FLOW PERIPHERALLY OUTWARDLY THEREFROM, A CASING ABOUT SAID ROTOR INCLUDING A PAIR OF SPACED AXIALLY EXTENDING WALLS, SAID WALLS DEFINING A SUCTION CHAMBER AND A HIGH PRESSURE DISCHARGE CHAMBER CIRCUMFERENTIALLY DISPOSED ABOUT THE PERIPHERY OF THE ROTOR, SAID ROTOR HAVING ITS PERIPHERY ON THE DISCHARGE SIDE EXPOSED IN EXCESS OF 180 DEGREES, ONE OF SAID WALLS HAVING A PROJECTION ADJACENT THE PERIPHERY OF THE ROTOR AND EXTENDING IN A SMOOTH SPIRALING SURFACE OUTWARDLY AND AWAY FROM THE PERIPHERY OF THE ROTOR AND TERMINATING IN A DISCHARGE END, SAID SECOND WALL BEING A COMMON WALL BETWEEN SAID SUCTION CHAMBER AND SAID HIGH PRESSURE CHAMBER, SAID SECOND WALL BEING SHAPED AS A SMOOTH OGEE SURFACE, ONE END OF WHICH ADJACENT THE PERIPHERY OF THE ROTOR AND SAID OGEE SURFACE TERMINATING IN SAID ONE END IN A PLANE SUBSTANTIALLY TANGENTIAL TO THE PERIHERY OF THE ROTOR, AND THE SAID OGEE SURFACE TERMINATING IN A DISCHARGE END OPPOSTELY FROM THE DISCHARGE END OF SAID FIRST WALL TO DEFINE A RESTRICTED OUTLET THEREWITH FROM THE CASING, SAID TANGENTIAL PORTION OF THE OGEE SURFACE COOPERATING WITH THE FLUID THEREOVER TO DEFINE A REVERSE FLOW VORTEX ADJACENT THE PERIPHERY OF THE ROTOR AND ECCENTRICAL THERETO, SAID REVERSE FLOW VORTEX COOPERATING WITH THE FLOW FROM THE SUCTION CHAMBER TO INDUCE FLOW INTO THE PERIPHERY OF THE ROTOR.