US2234733A

US2234733A - Compressor or pump of the rotary blades type

Info

Publication number: US2234733A
Application number: US217503A
Authority: US
Inventors: Jendrassik George
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-07-07
Filing date: 1938-07-05
Publication date: 1941-03-11
Anticipated expiration: 1958-03-11

Description

March 11, m41. a. '2234,733

COMPRESSOR 0R lPm 0F' THE'ROTARY BLADES TYPE Filed July 5, i938 Patented Mar., it, 194i conrnnsson on entre or anni no'ranr :etapas rizrn George .'iendrassilr, Budapest, lillnngary 6 @latina The invention relates to a compressor or pump of the rotary blades type in which the mean diameter oi any stationary or rotating blade ring is at least approximately equal to the average of the mean diameters of Ithe two blade rings adja-b shaped): In the case of compressors and pumpsoi" this type as known up to now the drawback has presented itself that .the friction of the working medium'taln'ng place on the surface of rotation guiding the flow, as on the compressor casing and on the wall of Ithe rotor, as well as on tid the blades, has exerted a disadvantageous inlinence on the distribution of velocities of the' working medium, and for this reason the eiciency of these machines .andthe pressure which it was possible to produce by their means have for many 'im applications not been sufiicient.

The layer of medium alongside the walls constituting the boundaries of the flow or on .those parts ot the blades which are adjacent to these boundary walls, which layer of medium is braked 353 by .the friction or by having become detached trom the suction side of the blades, i. e. the socalled tired boundary layer does not possess the same relative veloci-ty relatively to the blade ring as possessed by the portions of medium contained in the sound -core of the flow-and therefore the blades are unable to produce a suitable rise of pressure in .these places; accordingly the greater the success achieved in eliminating .the "tired boundary layers or 'at least reducing their dimensions, the more perfectly `the compressor or pump of the rotary blades Itypewill be able to operate. The boundary layer is, on the one hand, liable to rub against .the blades and against the walls, whereby its speed isdn'uenced in a disadvantageous manner, whilst on the other hand it is in a frictional relation with -the sound core of the flow likewise, by which latter friction, however, the velocity conditions of the boundary layer are influenced in an advantageous manner. Inlthe compressor or pump of the rotaryl blades type according to .the invention this drawback is eliminated by constructing the blading in such a manner, that the impulse convection (friction) between the sound core of the ilow and the boundary layer diminished in its (CEI. E30-mi2@ relative speed relatively .to .the blade ring should be substantially stronger than in the case of the types of apparatus known up to now.

lin order to enable the fundamental idea of the invention to be more readily understood,- let us suppose that a mass portion m of working medium possessing the mass m lpossesses a velocity component vt in the peripheral direction, the' said component suffering owing to friction either against the stationary or against the moving boundary wall or owing Lto friction against the blade rings, a variation of the infinitesimal figure of dut. The centrifugal force acting on this particle of medium is in which formula r means the distance from the axis of rotation. Owing to the said infinitesimal alteration of the peripheral component of the velocity this centrifugal force suiers an innitesimal varia-tion amounting to With a given variation of veloci-ty dut, this variation of .the centrifugal force is all the greater, the greater .the peripheral velocity component of the particle of medium. li in order to enable the conditions to be imagined more clearly it is supposed .that the working medium, for instance in the case of a compressor of axial throughiiow, possesses an average velocity of rotation of a idifaction identicai with that of the peripheral velocity of the rotor, but of smaller magnitude than .this veloci-ty, that part of the working medium which rubs against Ithe Wall of vthe rotor will become accelerated and .the surplus of centrifugal force acting on it in consequence hereof will be all the greater, the greater the rotation of the Working medium has been. Similarly, if the working medium rubs against the stationary wall (against the internal surface of the casing of the machine), its velocity will become diminished and the diminution of the centrifugal force acting on it will be all the greater, the greater Ithe average rotation of the medium has been. The force increment dPc acting on the particle rubbing against .the rotor will drive the rubbing particles outwards with a substantial force, whilst the par- -ticles of medium rubbing against the stationary casing will be impelled strongly towards the axis of rotation by the diminution of the centrifugal force as compared to the ambient. Both elects will give rise to a high amount of convection,

f serves for driving the compressor.

the condition for this being accordingly to keep the working medium in a substantial average rotation of not negligible extent relatively to the peripheral velocity of the rotor, tthe direction of such rotation being identical with the direction of the peripheral velocity of the rotor, but of smaller magnitude Ithan .the latter. The working medium willas is the case with the compressors or pumps of .the rotary blades type known up to nowhardly possess any speed component in the peripheral direction and thus the variations of such component resulting in consequence of the friction caused by the centrifugal force will in ythe case of-small variations Aof ,velocity be very small only, and in order that they should reach any appreciable figure, a variation of velocity of very great extent is necessary. The creation of increased exchange,y "of impulses will possess panticularly great 'importance in case the machines according .to the invention are of the multi-stage type, or, if the pressure head to be produced is high relatively to the velocity head corresponding to the peripheral velocity ofthe rotor. In the case of fans, where, f or instance, only one or two blade rings are employed, lthe importance of the friction of the boundary layer and, accordingly, also ythe importance of increasing the amount of convection, are substantially smaller.

In order to enable the invention to be more readily understoodFig. 1 of the accompanying drawing represents in a diagrammatical longitudinal section an embodiment shown by way of example of such a compressor or pump, Fig. 2 shows the picture, developed into a plane, of a section taken through the blading, Fig. 3 shows the correspondingvelocity triangles of the stationary and of the movingl blades, whilst Fig. 4 shows 'another embodiment of theinvention having rotating guide blades. I

In Fig; l, the rotor 5, in casing l, is fixed on shaft l journalled in bearings 2 and 3. The' rotor carries the rotary -blade rings 6. It is in the compressor casing that the stationary blade rings 'l are accommodated.v The shaft end 8 This apparatus operates in such a manner that the rotor will, if set into rotation'in the proper direction, -draw in the working medium through the inlet opening 9 and discharge it in compressed condition through the opening l0. rotating blade rings Il and lIl. move in the direction of the arrow I (in the plane of the section) at the peripheral velocity u, whilst the stationary blade rings I3 and I4, remain in a position of rest. vThe base line of the profile of the blades (its tangent line or in the case of blades convex on both sides the tangent of the adaptation circles of the blade profile tips) is at the outlet edge of the moving blades forming the angle ,32 with the peripheral direction, whilst at the outlet ends of the stationary blades the angle formed by this base line `and the peripheral direction is i. When determining the angles ,Si and p2, that one of the angles formed at the outlet end of the blade by the base line and the peripheral direction should be taken, between the sides of which the section of the blade does not fall, or, (for instance in the case of blades convex .onu both sides), that one between the.

sides of which only the smaller portion cf 4the blades is situated. In this manner the angles are dened unequivocally (they should always be measured on the working face of the blades at the outlet from the blade ring), and in what follows On Fig. 2 the.

also, it is always the angles measured in this manner which are meant when reference is made f to blade angles.

On Fig. 3 ci denotes the absolute velocityof the working medium before entrance into the stationary blades, whilst c2 denotes the absolute velocity of the said working medium after outlet from the stationary blades; the mean absolute velocity of the working medium is ck., The component of peripheral direction of this lastnamed velocity, which component vis equal to the average velocity of rotation of the medium,is vt;

Awhilst thecomponent va perpendicular thereto is the meridian velocity, which in the case of a compressor of axial throughiiow is equal to the axial velocity. The absolute velocities at the same time also mean the relative veocities vrelatively to the stationary blades. The velocities relatively to the moving blades arev obtained by adding the peripheral velocity u of the rotor, in the proper direction, to the velocities referred to above. Thus c'i is the relative velocity as between the medium and the rotating blades before the entrance of the medium into` the rotating blades, c'z is the relative velocity after the medium has left the rotating blades, whilst ck is the main relative velocity..

As in practice the base une of the mades is i with a good approximation equal to the mean direction of velocities, the angles i and z shown` on Fig. 3 are identical with the angles p1 and @a shown on Fig. 2.

As has been explained in what precedes, in order that a strong exchange of impulses should take place between the boundary. layer and the core o f the flow it is necessary that the average' peripheral velocity m of the medium should be suiiiciently high relatively to the peripheral velocity u. Thus a fairly good result can already be obtained if the average will at least on one diameter along the length of the blades reach one-third of the peripheral velocity; Naturally this exchange of impulses will be more advantageous if the average periph- -eral velocity of the medium is higher still than can be deduced also from Fig. 3, that the value of the quotient tan i tan z should, at least on one diameter along the blade length, be smaller than 2 andl larger than zero, wherein the angles fh and z belong to cooperating 'adjacent stationary and rotating blade rings.

In view of the fact that the magnitude of the meridian component of the velocity also exerts an influence on the attainment of high eiilciency, and in view of vthe fact that the magnitude 0f this meridian component should on a* least one diameter along the length of the blades preferably remain between one-fourth of the 'peripheral velocity and the total peripheral velocity, it is y possible to obtain a compressor of high efficiency in such a manner, if the constructional conditions of this last-named proportion are likewise fulfilled. In case the condition referred to above relating to the average rotation of the medium velocity of rotation I has also been satisfied, this further condition is fuliilled if the tangent of the angle ,81 between the peripheral direction and the base line of some stationary blade ring is, at least on one diameter along the blade length, greater than l@ and smaller than 3.

The circumstance that a substantial average velocity of rotation is imparted to the Working medium offers substantial advantages from the point of View of the operation of the compressor in case a rotor of high peripheral velocity is concerned. As Well known, it is not advisable to allow the relative velocity as between the working medium and the blades to approximate the speedof propagation of sound vibrations in the working medium too closely, as in this case the etliciency of the blades is liable to deteriorate in a substantial extent. In the case of a rotor having a given peripheral velocity, the only way in which the relative velocity can be diminished in a substantial extent consists in giving to the working medium a substantial average velocity of rotation in the direction of rotation of the rotor. This circumstance will, accordingly, on the one i' hand permit a higher elilclency to be obtained,

whilst on the other hand it will render higher peripheral velocities possible with good eiiiciency. The situation will be particularly favourable from the point of view of this last-na1ned circumstance, but will also be very advantageous from the point of View ci impulse exchange, in those cases, when an average rotation of such magnitude is imparted to the working medium as will, at least on onev blade diameter along the length of the blades, be equal to onehalf the peripheral velocity ci the rotor. 'The constructional condition for this is that, at least on one blade diameter, the angular setting of the stationary and of the rotary blades relatively to the peripheral direction should be mutually equal.

From the point of view of the magnitude of the exchange of impulses it is not immaterial how the average velocity of rotation of the working medium is distributed according to the distance from the axis of rotation. From this point l of view it is the most advantageous method to follow the distribution of speed of the so-called potential eddy, in which the velocity of rotation .stands in inverse ratio to the distance from the axis of rotation. In the case of such a rotation each particle of the working medium, being in an indifferent position of equilibrium, can be removed to any point of the radius with the smallest virtual force action, and therefore the variation of the centrifugal force acting on any particle will immediately and in the highest degree start convection. The constructional condition for ensuring that the average rotation should take place according to this law is that the ratio of the tangent of the angles i and z should at least approximately follow the law in which formula q is a suitably chosen constant, whilst r is the distance measured from the axis of rotation.

In the case of pumps, the rotation o f the working medium at a substantial velocity and the diminution by these means of the relative velocity between the working medium and the blades is also advantageous from the point of View of the diminution of the `danger of cavitation` The intensification, in the manner described, of the exchange of impulses also exercises an advantageous eii'ect from the point of view of diminishing the gap loss, seeing that the layer which has suffered a gap loss will become quickly mixed li with intact ow and it will not be possible, owin'g to the gap loss either, for a tired boundar layer,- by which the operation of the compressor would be influenced disadvantageously, to develop.

The forms of construction speciiication are only examples for illustrating the invention, and the invention can be carried into effect in very many kinds of vconstructional embodiments. From the point of view of interpreting the range of protection of the invenl5 tio-n in this manner, it is worth mentioning, for instance, that by a suitable generalisation of the wording of the invention, the range of the invention will also cover compressors constructed in such a manner that, in additionto the rotor, 2o

the so-ca1led stator (compressor casing) is also made rotatable in a sense of rotation opposite to the sense of rotation of the rotor;

Such an arrangement is shown onFig. i according to which the rotor lb and the stator it rnade rotatable relatively to each othen-the said stator being in this case a second external rotor rotating in the opposite sense--are by means of the journalling arrangements it and 2i! journalled in each other also in such a manner 30 vbrackets of the bearings ld and tu are also supported. This casing 23 is packed relatively to the shafts ll and I8 by means of the packings ill flu which are preferably of the labyrinth type.

Packing, preferably labyrinth packing likewise, is

required in addition hereto also between the rrlu. tually opposite cylindrical surfaces of the external rotor lli and ofthe casing 23, in order to prevent that the working iluid entering through the inlet opening 24 oi the casing 23, which working fluid has been brought to higher pressure in the compressor, should flow back from the high-pressure space into the low-pressure space of the casing, for which purpose, according to the illustration, the labyrinth packing 22A is employed. The low-pressure working fluid enters the low-pressure space of the casing 23 through the said opening 24, and passes from this space through the opening 26 on the external rotor I6 into the working space properj of the compressor, and streaming between the blades here, leaves the working space of the4 compressor through. the openings 2l of the ex- 60 terna] rotor, following which it leaves the highpressure space of the casing 23 through the opening 25. Of course, between the shafts Il and I8 rotating in mutually opposite senses, some kind of mechanical gear wheel connection, not shown o5 on the drawing, is required for uniting the rotations. If the peripheral velocity in any blade ring of the stator" (i. e., external rotor) at a.

certain blade diameter is denoted by u1, whilst .lo the same peripheral speed in an adjacent blade ring of the rotor proper cooperating with the said stator blade ring is denoted by u2, u1 being uz, it is possible to indicate regarding the ratio of the tangents of the blade angles i and ,Bz the u described in the lo ld in the 35 whilst in case the condition established above regarding the meridian component of the iiow speed according to which l s s 1 y 4 U2 X is also satised, tan r should be chosen between the following limits:

In case of u1=0 (stationary compressor casing) these expressions become converted into the conditions already stated above.

The compressor described is particularly suitable for use in connection with gas turbines, seeing that in the case of gas turbines the high emciency of the compressor is a very important condition.

Il claim: A

l. In a multiple stage rotary 'compressor or pump comprising a rotor and a casing, a plurality of blade rings on the rotor alternating with a plurality of blade rings on the casing, the mean diameter of any blade ring. being at least approximately equal to the average of the mean diameters of the adjacent blade rings, the blades of each ring having airfoil profiles and being positioned so that the value -of the quotient composed of the tangents of the angles ,91 and ,e2 should at least on one-blade diameter along the blade length fall within the limits:

tangentially to the working face of the bladev profile) of any blade ring on the casing, and of the adjacent blade ring cooperating therewith on the rotor, respectively, u1 and u2 denote the corresponding peripheral velocities of these blade rings, the casing and the blades carried thereby being made rotatable in a direction opposite to the direction of rotation of the rotor.

2. In a multiple stage axial flow rotary compressor or pump comprising a rotor and a casing,- a plurality of blade rings on the rotor alternating with a plurality of blade rings on the casing, the mean diameter of any blade ring being at least approximately equal to the average of the mean diameters of the adjacentv blade rings, the blades of each ring having airfoil proi'lles and being, at least one one blade diameter along the blade length, positioned so that the value of the quotient composed of 'the tangents of the angles ph and ,32 should fall within the limits:

2 tan l 1i tan z l +-3u2 besides the value of tan ,Si should fall within the limits:

.tangentially to the working face of the wherein p1 and ,s2 denote the angles formed at the outlet from the blade ring on the working face between the peripheral direction and the base line of the blade prole (e. g. the line tralted b e profile) of any blade ring on the casing, and of the adjacent blade ring cooperating therewith on the rotor, respectively, and u1 and u2 denote the corresponding peripheral velocities of these blade rings, the casing and the blades carried thereby being made rotatable in a direction opposite to the direction of rotation of the rotor.

3, In a. multiple stage axial ow rotary compressor or pump comprising a rotor and a stationary casing, a plurality of blade rings on the rotor alternating with a plurality of blade rings on the casing, the mean diameter. of any blade ring being at least approximately equal 'to the average of the mean diameters of the adjacent blade rings, the blades of each ring having airfoil proles and being positioned so that the value o f the quotient composed of the tangents of the angles [31 and z should at least on one blade diameter along the blade length fall within the limits 2 and 0, wherein p1 and' denote theiangles formed at the outlet from the blade ring on the working face between the peripheral direction and the base line of the blade' prole (e. g. the line traced tangentially to the working face of the blade profile) of any stationary blade ring carried by the stator, and of the adjacent rotating blade ring carried by the rotor and cooperating with the said stationary blade ring, respectively.

4. In a multiple stage axial flow rotary compressor or pump comprising a rotor and a stationary casing, a pluralityl of blade rings on the rotor alternating with a plurality of blade rings on the casing, the mean diameter of any blade ring being at least approximately equal to the average of the mean diameters of the adjacent blade rings, the blades of each ring having airfoil profiles and being, at least on one blade ditionary blade ring carried by the stator, and of the adjacent rotating blade ring carried by the rotor and cooperating with the said stationary blade ring, respectively.

5. In a multiple stage axial flow rotary compressor or pump comprising a rotor and a stationary casing, a plurality of blade rings on the rotor alternating with a plurality of blade rings on the casing, the mean diameter of any blade ring being at least approximately equal to the average of the mean diameters of the adjacent blade rings, the blades of each ring having airfoil profiles and being, at least on one blade diameter along the blade length, positioned so that the angles i and ,92 should be mutually equal, and tan )Si should fall within the limits 3 and 1A, wherein i and [iz denote the angles formed at the outlet from the blade ring on the working face between the peripheral direction and the base line of the blade prole (e. g. the line traced tangentially to the working face of the (blade ring carried blade prole) of any" stationary blade ring carried. by the stator, and of the adjacent rotating by the rotor and cooperating with the said stationary blade rinarespeetively. 6. ln a multiple stage arial flow rotary compressor or pump eomnrising a rotor and a oasing a plurality of blade rings on the rotor alternating with a pluralitr7 oi blade rings on the casing, the inean diameter of any blade ring being at least approximately equal to the averageoi the mean diameters of the adjacent blade rings, the blades oi each ring having airfoil profiles and being positioned so that the value of the quotient composed of the tangente of the angles i and 132 should at least on one blade diameter along the blade length fall Within the limits:

A 2 tan [g1 inw@ tan 2 0 farther, the same quotient of tangente should on the various blade diameters alom;l the blade length at least approximatel7 follow the law tan [3gwherein q' is a suitably selected constant and i' is the distance of the Various points oi the blade length measured from the axis of rotatiornwhilst i and z denote the angles formed at the outlet from the blade ring on the working face be tween the peripheral direction and the base line of the blade prole (e. g. the line traced tangentially to the Working face of the blade profile) of any blade ring on the casing, and of the adjacent blade ring cooperating therewith on the rotor, respectively, finally u1 and uz denote the eorresnOndine;r peripheral velocities oi: these blade rings, the casing and the blades carried thereby` being 4i'nade rotatable in a direction opposite to the direction oi rotation of the roten JENDRASSIK.