Turbine Wheel

Abstract

A turbine wheel or rotor for operation by gas streams containing entrained particles of liquid or solids or liquid streams containing bubbles, such as in power recovery from dust-bearing gas or boiling liquid. The passageways between blades of the rotor are so shaped that as the flow progresses radially inwardly and its circumferential motion with the wheel is retarded and centrifugal force on such particles therefore decreases, there will be at first a radial and small negative relative tangential component of flow, and the radial inward rate of flow component and hence drag on such particles opposed to such centrifugal force will decrease accordingly to maintain a substantial balance of radial forces on such particles. Also the passages are curved so that they will substantially parallel the circumferential-axial flow rate component as the decrease in radial flow rate component is replaced by increase in circumferential flow rate component relative to the rotor, while the axial flow rate component is maintained at or increased to a value to move the stream through the axial extent of such passages in such time as is required for the circumferential flow rate component relative to the rotor to substantially equal and oppose the circumferential velocity of the outlets of such passageways. Thereby the drag on such particles to cause them to impinge on the blades will be minimized. The words "tangential" and "circumferential" are used synonymously.

Description

SUMMARY OF THE INVENTION

BACKGROUND OF THE INVENTION

This invention relates to turbines for operation by streams containing entrained particles. It is applicable to power recovery turbines for gas streams containing dust. It is also applicable to turbines operated by streams of gas or vapor, at least a portion of which precipitates or may condense and precipitate as minute liquid or solid particles as the streams pass through the turbines. It is applicable likewise to liquids at temperature and pressure such that they will boil while passing through the turbine or which already at entrance have entrained vapor or gas.

Most turbines are of the "axial flow" design which consists of stationary nozzles in combination with a rotor having a series of peripheral blades. The nozzles jet an expanding stream into the rotor between the blades in a tangential-axial direction. The rotor blades change the direction of flow of the stream passing through and generally jet or direct the stream backward with respect to the tangential direction of the rotor blades. This involves a change of direction in the circumferential plane as the stream passes through the rotor blades. This change of direction (tangential or circumferential acceleration) tends to throw the particles out of the stream and against a passage wall causing blade damage and loss of efficiency.

There is another type turbine called the radial or "inflow" turbine. It is similar to that described above except that the primary nozzles jet the stream into the rotating blades in a direction having a radial component. Usually there is little if any axial component to this direction, the jetted stream having a tangential-radial direction only. The rotor blades usually have 3-dimensionally curved passages to turn the stream from radially inward to axial and at the same time direct it backwards relative to the rotor.

In radial turbines the same problem with suspended particles and liquid droplets applies as occurs with the axial flow turbines. There is the additional effect of centrifuging the particles radially outward causing them to accumulate in the rotor and compounding the problem.

Attempted solutions have involved a separator at the outer periphery of the rotor to accumulate the liquid or solids and the provision of a bypass conduit around the rotor blades; and, where there is only a trace of solids, to provide pockets in which they can accumulate and remain.

THE SOLUTION PROVIDED BY THE PRESENT INVENTION

This invention solves the stated problem by controlling and combining the forces that act on any suspended particle by so designing and selecting the shape of the passage through the rotor that the net force on the particle is substantially parallel to the passage walls so that the particle is not thrown against any wall to collect or cause erosion or other trouble. This invention also employs a stream velocity through the rotor passage which is higher than the particle's relative upstream or slippage velocity which is caused by the dynamic forces acting on the particle.

The combined dynamic force acting on any particle suspended in the flowing stream of fluid as it passes through the rotor is the sum of the centrifugal force, a small axial acceleration force and a tangential acceleration force.

It is, therefore, one of the primary objects of this invention to provide a turbine wheel having flow passages therethrough between the blades of the wheel, which passages are so-shaped that the net forces on a particle suspended in the stream passing therethrough have a resultant substantially parallel to the passage walls and with a predominant resultant force on the particles in a direction toward the outlet or discharge end of the passage.

The above and other objects of this invention are achieved through the arrangement and shapes of parts disclosed in the accompanying drawings, in which there is illustrated by way of example only and not by way of limitation, certain preferred embodiments of the invention.

In the drawings

FIG. 1 is a diagrammatic illustration in section along an axially extending surface curved relative to a truly radial direction to follow the passageways through two opposite nozzles of a radial turbine and a rotor constructed in accordance with this invention as indicated by the line 1--1 of FIG. 2, illustrating the flow of gas in radial and axial directions through such passageways;

FIG. 2 is likewise a diagrammatic and rather fragmentary view of the same structure taken along a surface at substantially right angles to that of FIG. 1 and essentially along the line 2--2 of FIG. 1, and showing an elongated form of nozzle;

FIG. 3 is a vector illustration of the radial and axial velocity and acceleration components in a surface comparable to that along which FIG. 1 is taken;

FIG. 4 is a vector illustration of the radial and tangential velocity and acceleration components in a surface at right angles to that represented in FIG. 3 and extending radially relative to the axis of rotation of the turbine;

FIG. 4A is a vector illustration of the velocity and acceleration components looking from the outside radially inwardly toward the axis of the turbine in a radial developed view;

FIG. 5 is a fragmentary view similar to the upper portion of FIG. 2 but showing a slight modification of the idealistically preferred form of wheel shown in FIG. 2 so as to provide a slightly more practical embodiment;

FIG. 6 is a side elevation of a radial-axial flow turbine wheel constructed in accordance with the present invention and showing the peripherally arranged entrances for the gas to be expanded;

FIG. 7 is a partial end view of the turbine wheel shown in FIG. 6 with parts broken away in order to better illustrate the shape, arrangement and disposition of the blades providing the passageways through the wheel;

FIG. 8 is a view similar to FIG. 7 showing a different form of rotor for a substantially entirely radial flow constructed in accordance with this invention;

FIG. 9A is an axial diagrammatic view of a fragment of a rotor of the form of FIGS. 5-7, with a slight modification, showing a projection, on a plane normal to its axis, of a passage between two blades;

FIG. 9B is a developed radial view of the trajectories of particles passing through the impeller along the paths A--B and C--D of FIG. 9A;

FIG. 9C is a lateral view showing the projection of such passages on a radial-axial plane;

FIG. 10 is the projection of two extreme courses of the absolute path in a transverse plane (axial view), which is followed by an element as it passes the rotor along said paths A--B and C--D, with force vector diagrams at representative time intervals showing the component and resultant forces acting on such elements respectively at such intervals.

FIG. 11 is a view similar to FIG. 9C showing a modification.

In accordance with the present invention, the blades which provide the passages through the turbine wheel are so arranged and shaped as to create a directed inlet velocity adjacent the rotor passageway entrances which is different from the tangential velocity of the rotor. Such inlet velocity and direction through the rotor passage is controlled and altered so as to attain the condition of negligible acceleration of suspended particles transverse to the stream line.

This can be best understood by following the stepwise path as illustrated in FIGS. 1 and 2, and the shaping of the cover of the wheel. These provide the desired passageway cross section and hence the gas velocity through the passages so that the walls or blades forming the walls of such passages can be located as needed to meet the requirements.

Referring more in detail to the drawings, FIGS. 1 and 2 show the gas entering from a high pressure zone 1 into a nozzle 2 which is stationary relative to the rotation of the turbine. In the throat 3 of the nozzle 2 this gas is accelerated to a high velocity. Most of this velocity is in a tangential direction, but a component of it is in the radial direction as is shown in FIG. 1. The throats of such nozzles may be elongated by extension of the upstream ends of the nozzle blades from usual length as shown in dotted lines to the solid line length as shown at 2A in FIG. 2. This allows more time for an entrained particle to be accelerated to the high velocity of the gas in the nozzle. This is particularly desirable if the particles are relatively large in size.

In accordance with this invention, the projected sum of a components of the velocity is the radial-axial plane should idealistically follow the arrows 4 (FIG. 1) through the rotor, and while so doing make substantially a 90.degree. turn, thereupon leaving the turbine wheel axially and with substantially no or only a small radial component as indicated by the arrow 5. In doing this, entrained particles in the flowing stream should follow the path of the arrows and have negligible tendency to drift toward the passage wall and impinge on the wall.

Referring to the vector diagram of forces acting on a suspended particle in the radial and axial directions, as shown in FIG. 3, let it be assumed that arrow 4A indicates the initial velocity of gas and entrained particles entering the rotor and that this velocity has a small axial component 4C in the direction toward the discharge. In this diagram, the arrow 4A may be considered as a vector representing the strong drag force of gas flow in the direction of the flow of the main stream in which is suspended a particle whose movement is to be observed, the force being due to the particle slip relative to the gas. It is proportional to the slip rate as the particle tends to resist being swept along. There is also a reasonably strong force 4B in a radial direction due to the centrifugal force, the origin of which is more obvious by inspection of FIG. 2. The vector sum of forces 4A and 4B is the force 4C, which accelerates the particle in the axial direction and changes its net velocity from that at the point of application of force 4A to that of application of force 4D as the stream moves along.

The velocity in the direction represented by the arrow 4D having a direction which is more nearly axial than that of the arrow 4A, it would provide a larger axial component of force 4C' than that represented by the arrow 4C, and one which is usually greater than necessary or desirable to provide the required acceleration in the axial direction. Likewise the arrow 4E would be more nearly axial then 4D and provide a larger axial component 4C" than that of 4D. To reduce and control this axial force to a desirable value which may be approximately constant throughout the passage through the rotor, the tangential velocity of the stream is changed by curving the passage in a downstream direction to give the stream a backwards relative motion with respect to the direction of rotation of the turbine wheel. This reduces the absolute tangential velocity of the gas flow, and the centrifugal force associated therewith. It is noted that at the same time the centrifugal force will be reduced by virtue of the shorter radius arm of the rotation of the particle as it gets closer to the axis of the wheel. By proper choice of the aggregate reduction in centrifugal force in the particle's radial slip in the stream may be reduced. Along with this the axial force, or the component of force 4C" in an axial direction, may be reduced and hence the particle's axial slip in the stream, to any desired positive value. Thus the direction of the net dynamic force on a suspended particle in the radial-axial plane can be controlled and the particle caused to follow a stream line.

It is noteworthy that in the foregoing discussion an initial stream direction was called for in which there was an axial component for the purpose of providing the axial force 4C. Initial deviation from the radial direction is thus contemplated by the present invention. However, this deviation may be secured either by guiding the stream into the rotor blade passages with the initial axially inclined angle, which is sometimes mechanically inconvenient, or by deliberately turning the stream and sustaining a momentary small axial acceleration on suspended particles therein perpendicular to the stream lines. This last may be done because the necessary change in direction is so small as to be insignificant from the standpoint of causing impingement of particles or acceleration thereof in the direction perpendicular to the stream lines. Nevertheless, such change in direction provides the necessary small initial axial component for carrying out this invention.

Referring now to the velocity and acceleration component projection in a plane transverse to the axis of rotation, these are shown in FIG. 2. The pressurized fluid at 1 in this Figure is jetted by means of nozzle 2 in an absolute direction 6. A particle 7 moving with such jetted stream will have a tangential velocity slightly less than that of the rotor so that initially it will have a small tangential component relative to the rotor and backward relative to the rotor rotation and will have a small radial velocity. It is desirable although not essential that this relative velocity increase somewhat throughout the passage of the gas through the turbine wheel.

The gas stream thus carries the suspended particle 7 radially inward as indicated by arrows 8 in FIG. 2. Acting on such particle is a radially outward centrifugal force which results from the tangential or circumferential component of motion of the particle, and it varies with the tangential speed of the particle, etc. This is opposed by the drag on the particle as it is carried along by the stream.

With reference to FIG. 4, the arrow T designates the tangential or circumferential direction and the direction of rotation, 8A is an arrow representing the centrifugal force vector acting on the particle 7, 8B represents the drag force vector on such particle, and 8C is an arrow representing the net sum of the two which is a decelerating force in the opposite direction from the tangential arrow T. This force 8C serves to increase the reverse motion of the particle 7 relative to the turbine wheel and to deflect its relative motion to a direction shown by the vector 8D. Along with the curving of the passage so as to turn it to the desired ultimate direction, its cross section is so sized as to accelerate the stream backward, relative to the turbine wheel, to a near zero absolute tangential velocity at which it is discharged, its axial absolute velocity at this point being preferably the only absolute velocity remaining in the stream.

FIG. 4 shows the particle to move radially inwardly while being accelerated backward, and finally has only a small axial velocity at the discharge which is radially inward of the inlet. However, the vectors 8A" and possibly 8A' could in some cases be negative (upward) which would increase the radius at the point of discharge, even to a point where it is of larger radius than the inlet.

Reference is had to FIG. 4A for a projection of vectors similar to those shown in FIGS. 3 and 4, but in a circumferential surface with the rotor axis as its center. Here it will be seen that the vector sum of the axial component 4C and the tangential component 8C is 14C, representing the axial-tangential component. Similar views of the other vectors show the relative path of the particle with respect to the rotor in this radial developed view.

A closer examination of FIG. 4 makes it apparent that for the vectors to be as illustrated, the initial negative tangential relative velocity 8C is required. This negative velocity may easily be created by proper choice of exit velocity from the nozzles 3. However, if it is desired to use a different nozzle velocity relative to the tangential rotor velocity, this can be done and then the stream turned to the required direction in the immediate vicinity of the rotor entrance.

By reference to FIG. 5, it will be seen that there is a curve 9 in each of the blades 10 which initially receives the gas entering the entrances to the passages through the wheel and provides for turning the stream substantially at the entrance so that it has the required initial negative tangential component of relative velocity. The provision for such a turn or change of direction naturally applies a force to any suspended particle perpendicular to the stream line. However, the magnitude and extent of such force are small, and its effect is negligible. The remainder of the action in FIG. 5 is the same as in FIGS. 1 and 2, the flow being through passageways between the curved portions 10 of successive blades 13 and between the main disc 16 of the rotor and the cover 12. This flow enters through entrances 17 of FIG. 2 of 17A of FIG. 5 and emerges through discharge 11.

Thus, by controlling the relative inlet tangential velocity and the passage direction and cross section, the sum of the dynamic forces acting on the suspended particle can be maintained parallel to the stream line as the particle passes through the rotor.

The control of the tangential velocity and that previously described with respect to the radial-axial plane, can be accomplished simultaneously.

Thus it will be seen that by providing a substantial initial velocity to the stream in chosen directions (axial, and/or tangential) there is provided due to drag an initial axial and/or tangential component of the net dynamic force substantially at the rotor passage inlet. This component acting on a suspended particle is sufficient so that as the centrifugal force decreases the axial-tangential component may be increased and redirected to cause the particle to follow a streamline path through the rotor provided by blades of reasonable and convenient shape, without substantial impingement on those blades.

Referring now to FIGS. 6 and 7, there is illustrated one specific embodiment of this invention and in FIG. 8 is found another specific embodiment, both of which will now be described.

In FIG. 6 the turbine rotor is shown as having a main wheel portion with a radially extending disclike part 16 having a surface which provides one of the walls of each of the gas passageways through the rotor. The disclike part 16 is shaped as shown at 17, with a slight axial inclination so that when the gas to be expanded is jetted into the rotor it will strike this surface and be given a slight axial component of motion as hereinbefore described. The passageways through the rotor are bounded at circumferentially spaced positions by the blades 18. Blades 18 are given both a compound curve and an increase in width from the radially outermost portion inwardly. The blades 18 are each joined continuously along one edge to the adjacent surface of the disclike part 16. The outermost portions of the opposite edges of the blades are preferably joined by a cover ring or shroud 12 which is shaped to provide the necessary axial widening of the passageways through the rotor as they extend inwardly toward the axis. The cover ring may be omitted if the blade edges rotate in close proximity to a stationary wall matching the contour of the blade edges.

It is noted that these blades 18 are constructed as hereinbefore described so that they have portions 9 adjacent their outermost extremities and at the entrances to the passageways through the rotor. These portions 9 are inclined slightly rearwardly and radially outwardly so as to permit gas, if desired, to be jetted into the rotor at a tangential velocity slightly greater than that of the outer portions of the rotor where the entrances to these passageways are located. These outer portions of the blades are then curved slightly so that from a point just slightly inwardly from the entrances to the passageways the blades extend and curve ever more steeply toward the rear in an inward direction. Thus, from a point just inwardly of and adjacent the entrances the tangential velocity of the gas within these passageways will be slightly less than that of the rotor at such points. As the gases move inwardly they will be decelerated in a tangential absolute sense to an ever increasing degree. Preferably this deceleration will continue until the absolute tangential velocity of the gas is substantially zero. Its velocity relative to the wheel will then be the same as the absolute velocity of the rotor but in the opposite direction to the rotor velocity. It will be discharged from the outlets of the passageways which in this instance are axially open as shown at 11.

In the form of the invention shown in FIGS. 6 and 7, the discharge of the gas from the passageways through the rotor is axial. The disc portion 16 is provided with a hub section 19 which extends axially to a plane substantially coincident with the outlets 11 between the blades, and is integrally secured to the inner edges of said blades. Any suitable opening 20 through the hub 19 may be provided for the purpose of mounting the rotor upon a suitable shaft.

In FIG. 6 and FIG. 7 the wall of the disc portion 16 which forms a portion of the walls of the passageways through the rotor, has an initial axial inclination in an inward direction to cause the gases in passing through this rotor to move axially and they are discharged from one end of the rotor in an axial direction. Another form of the invention is applicable to a wheel such as shown in FIG. 8 in which the discharge 111 from between the blades is radially inward into a hollow portion or open space around the axis. In such case it is unnecessary that the gas entering the entrances of the wheel passageways have any axial component because the gases do not move substantially in an axial direction until after their discharge from the passageways between blades. In the case of this wheel, as in the case of that shown in FIGS. 6 and 7, the entrances are around the outer periphery and are between a disc section 116 and a cover 112 spaced axially therefrom, and between blades 118 spaced circumferentially about the rotor between the disc section 116 and the cover 112.

All of such blades 118 are curved adjacent their outermost portions at 109 in a slightly outward and rearward direction, and throughout all portions inwardly therefrom in a radially inward and rearward direction. The cross sections of the passageways formed between these blades are controlled by the widths of the blades and the positioning of the cover 112 relative to the disc 116. Unlike the device of FIGS. 6 and 7, the outlets of the passageways between the blades, as shown at 111, are in a radially inward direction. As a result, while the gas emerges from the passageways at substantially zero absolute tangential velocity, the same as in the case of FIGS. 6 and 7, it emerges without any axial velocity and with only a moderate radially inward velocity. While it is true that the gas after emerging in a radial direction as just described must be turned to an axial direction, this can be accomplished without impingement upon the blades because the turning is accomplished only after the gas has emerged from between the blades.

The same principles apply to he rotor of FIG. 8 as previously described in connection with the other figures. However, there is no necessity for an initial axial component nor for any provision to be made for imparting an axial component to the gas at any time during its passage through the rotor.

Reference will be had now for more detailed and explanatory disclosure and for certain specific modifications to FIGS. 9A, 9B, 9C, 10, and 11.

To use a convenient and practical example, it will be considered that the tip speed of the rotor in these figures is slightly over 1,000 feet per second and that the gas entering the periphery of this rotor is being jetted from the surrounding primary nozzles at a tangential component of 1,000 feet per second, a radial component of velocity of 125 feet per second and a negligible axial component of velocity. The cross section of the passage through the rotor is so proportioned as to increase the velocity in the radial-axial plane to about 200 feet per second at the discharge.

The curve A--B in FIG. 10 is the projection of the absolute path in the transverse plane (axial view) which is followed by an element of the fluid as it passes through the rotor. This element will be referred to as the radially outermost element of flow. The beginning point A is shown in FIGS. 9A, 9B, and 9C. As the element proceeds from its beginning point A towards its exhausting point B, its absolute velocity in the transverse plane (FIG. 10) is gradually reduced and the curvature of its path gradually increases (radius of curvature becomes shorter). This curve is not an arbitrary one, but is constructed stepwise from the assumed initial conditions and premises including the assumed blade shape in FIGS. 9A, 9B, and 9C. This latter blade shape will be discussed in more detail further below.

Referring again to path A--B in FIG. 10, a succession of stations at equally timed intervals are marked as t,1 t2, t3 and so on. At a representative selection of these stations there is a number on the convex side of the curve stating the centrifugal force acting on the element in terms of gravity. The first one is marked 72,000 which means a centrifugal force 72,000 times the force of gravity. This centrifugal force is due to the velocity at which the element follows a curved absolute path.

As stated above, the absolute velocity component of the element along this path A--B is gradually reduced, and this deceleration requires a force tangential to the curve for its accomplishment. The numbers written on the concave side of curve A-B at each time station t1, t2, etc. gives the tangential force in multiples of gravity at each point required to decelerate the element the required amount.

The centrifugal forces act radially (to the curve) and the deceleration forces act tangentially. A vector diagram is drawn at representative points showing the resultant force in this plane.

Examination of the path of a particle along path A-B in FIG. 10 and comparing it with the blade shape in FIG. 9A will reveal that at each corresponding position, with a minor deviation described below, the inclination of the blade shape is coincident with the resultant force vector.

Past point t6, the resultant force deviates from being parallel to the passage wall because in this case there is a deviation of the blade shape from the ideal (dashed line) to the more practical (dotted line) position. Its deviation is in the direction away from the outer wall of the passage inward into the main stream of flow which is desirable because the stream will sweep it on through. This situation is due to the presence of a secondary nozzle (described below) at the end of the path where the element is jetted out of the rotor passage.

One significance of this blade shape and performance is that if the stream should have a small entrained particle (liquid droplet), which is small enough that it is entrained forcibly with the stream with only a moderate drift even under high acceleration forces, it would not tend to impinge the passage wall. This is true of particles of the size of fog particles and also larger ones --up to about one thousandth inch in diameter under commonly occurring circumstances. This drop size limit is relative.

Instead of reference as above to an element of the gas, reference will now be to an entrained particle. The force against such a particle is the vector sum of forces as described above. With this improved blade shape it acts at all points parallel to the wall of the passage or away from the wall so that what drift the particle sustains under the influence of these forces as the stream passes through the rotor is parallel or away from the wall and not toward it, which might cause the particle to impinge and collect on the wall.

Reference is now had to path C-D in FIG. 10, which is the axial projection of the absolute path of a particle following the path shown in FIGS. 9A, 9B, and 9C and which will be referred to as the radially innermost element of flow. The projection of this path in FIG. 10 also has force vector diagrams drawn at representative time intervals, which reveal the resultant force at each time point. Comparison of this axial projection of the path and series of vector diagrams with the shape of the axial projection of the adjacent wall of the passage in FIG. 9A shows that the wall is parallel to the resultant vectors at all points between C and time point t10. At this point, as shown in FIG. 9A, it will be at an angle to a radius of between 45.degree. and 60.degree.. Between time point t10 and D, the vectors are very much smaller. A small component of each of these small resultant vector forces is perpendicular to the passage wall (dashed line) urging the suspended particle toward the wall. The cross section of the portion of the passage through the rotor which is radially inside of time point t10, being near the center of the rotor, is a small fraction of the cross section of the full passage. That is to say that the force causing particle drift toward the passage wall is very small and it affects a portion of the stream which is a small fraction of the total. The blade could be made of such shape as to fully meet the requirement of being parallel to the resultant acceleration force all the way to the discharge, but it would not be as structurally resistant to high rotating speeds as is usually necessary for tip speeds of the order of 1,000 feet per second. Thus, the blade shape has been compromised in this vicinity, and, except as discussed below, it has been found permissible in most instances to accept this moderate movement of the suspended particle toward the wall in a zone which carries only a small fraction of the total stream.

At less than full design capacity, the discharge passages between the blades will not be well filled. Because of centrifugal force opposing the stream's approach toward the central portions of the passages, the stream channels toward the outer portions of the passages. This tends to minimize or solve the problem for less than design flow or, conversely, when the passages are oversize for the actual flow.

However, there is an improvement which solves the problem of the slight movement of particles toward the wall. It consists of ending this portion of the passage at this point as shown in FIG. 11.

Another improvement solving this same problem consists of a lip 20 at the outer edge of the blade as shown in FIGS. 9A and 9B. This lip interferes with the flow of gas near the leading wall of the passage leaving it almost stagnant. Accordingly, along this portion of the path C-D where the resultant force vector has a component perpendicular to the wall this force will affect particles entrained in the main stream but not those in the portion of the stream near the wall because there the stream is relatively stagnant. The small amount of drift resulting from these small vector forces may carry the particle over into this nearly stagnant stream. This stream being nearly stagnant leaves any suspended particle subject only to a radial centrifugal force. When this suspended particle tends to move radially outward, it looses angular velocity and moves away from the wall out into the flowing stream which then will carry it away. If it should continue toward the discharge and impinge on lip 20, as some particles no doubt will, it may collect on the lip, but centrifugal force will carry it radially outward on the surface of this lip toward the outer edge. At this point, centrifugal force will cause it to leave the lip and fly out into the main stream which already is near the rotor discharge. In one form of the invention, the rotor is constructed as seen in FIG. 9C so that this edge labeled 20a is clear of any part of the rotor so that the particle which is slung off of the edge of the lip will enter the discharge passage and cannot touch the rotor.

Referring now to FIG. 9C, which shows the projection of the path of the element or particle in an axial-radial plane, it is seen that the path is curved. This will tend to force the particle radially away from the convex face of the path. In the case of path A-B this is desirable because it throws the particle out into the main stream so that it will be swept out the discharge.

In path C-D which is near the inner wall of the passage, this is undesirable, although the forces are small. By this effect, particles would tend to impinge on the inner face of the rotor passage. As stated above, this is nearing the center of the rotor so this area is not extensive and the amount of gas involved is small and the forces not important.

In another facet of this invention a radially extending lip is placed at the discharge edge of the "floor" of the passage as shown by 21 in FIG. 9A. This again creates a stagnant zone upstream of it and causes the net force on particles therein to be away from the "floor" and out into the main stream to be swept out. Any particles from the main stream entering this stagnant layer will likewise be thrown back.

In an extension of this form of the invention, multiple ridges 22 (FIG. 9C) are placed on this (floor) surface so that accumulated liquid will not crawl up along the floor toward the inlet of the rotor but due to centrifugal force will be thrown from the crests of the ridges out into the main stream and be swept out through the discharge. This also extends the stagnant layer and makes it more stable.

In some instances the lip 20 at the discharge edge does not influence the flow sufficiently far back upstream. In these cases radial ridges 23 or other roughness may be formed on the blade wall similar to those 22 described previously for the "floor" of the passages.

To the extent that particles land on a ridge, centrifugal force will throw them radially outward, this creates a negative angular acceleration on the particles or droplets, so they leave the surface and find themselves in the main stream again.

Paths A-B and C-D were predicated upon a moderate radially inward velocity and about 60 percent acceleration through the rotor. If the inlet velocity should be higher, the required blade shape would have to extend farther around the rotor and the two paths (in FIG. 9A) would be somewhat closer together. Thus, it is desirable not to have too high a radial inlet velocity. This can be accomplished by making the axial dimension of the passage greater at the inlet.

From the foregoing it will be seen that a gas turbine wheel has been provided which is capable of carrying out all of the objects and advantages sought by this invention and that certain illustrations and examples have been disclosed for the purpose of illustrating and describing the invention so as to enable others skilled in the art to practice the same within the scope of the invention as set forth in the following claims. outer periphery,

Claims

I claim:

1. In a gas turbine wheel for expanding gas having during at least part of the expansion nongaseous particles in suspension therein while deriving mechanical power therefrom, said wheel comprising a body symmetrical about an axis and having a series of passages with entrances circumferentially spaced about its outer periphery the improvement which comprises said passages each having from an initial point adjacent its entrance and to a point adjacent its discharge a path of flow with radial and circumferential components, the radial component varying from a maximum at said initial point to a minimum at the discharge and the circumferential component varying from approximately zero relative to the wheel at said initial point to a maximum at the discharge, the last-mentioned component being rearward relative to rotation of said wheel, said components having such respective magnitudes that at any given point for a given rate of gas flow through said passages, the drag on a nongaseous particle suspended in said gas will have a radially inward component approximating the centrifugal force thereon and the direction of the resultant of all forces tending to accelerate such particle is substantially parallel to the adjacent portions of the passage walls.

2. The improvement in gas turbine wheel as set forth in claim 1 in which said wheel has discharges at a lesser distance from the axis than said entrances, and there is a change in direction of drag to more nearly tangential, to effect reduction in radial component of drag to match reduction in centrifugal force as a particle moves from entrance toward discharge, and to effect an increase in the tangential component of drag.

3. The improvement in gas turbine wheel as set forth in claim 1 in which said discharges are axially open and axially spaced from said entrances and said passages are shaped to provide at an initial point adjacent their entrances and throughout the remainder of their lengths respectively paths of flow with an increasing axial component also.

4. The improvement in a gas turbine wheel as set forth in claim 3 in which said wheel has discharges at a lesser distance from the axis than said entrances, and there is a change in direction of drag whereby the resultant of the axial and tangential components of said drag will increase at successively radially inward points as the centrifugal force opposing said drag decreases, and the axial component will be increasing in a downstream direction all such given points.

5. The improvement in a gas turbine wheel as set forth in claim 4 in which there is a change in direction of drag whereby the resultant of the components of drag normal to the centrifugal force will have a tangential component which increases at such given points as the particle approaches the axis and centrifugal force thereon decreases.

6. In a gas turbine wheel for expanding gas having during at least part of the expansion nongaseous particles in suspension therein, while deriving mechanical power therefrom, said wheel comprising a body symmetrical about an axis and having a series of passages with entrances circumferentially spaced about its outer periphery and axially open discharges at a lesser distance from the axis than and axially spaced from said entrances, the improvement which comprises said passages each having a direction at an initial location adjacent its entrance with a radial component such that the radial component of drag of gas at said initial location flowing through said passage at a predetermined design velocity on a nongaseous particle suspended therein will approximately equal the centrifugal force on said particle at said initial location, and the component at right angles to said centrifugal force is at an angle to the axis such that the axial component of such drag will have a predetermined value required to axially accelerate the particle immediately and the passages each being so increasingly directed radially and axially progressively from said entrance as to cause the drag to constantly increase the axial acceleration with an initial value such as to reach a desired value at discharge while matching the deceleration in the tangential and radial directions so as to maintain the resultant of the three force components parallel to stream flow through the passage.

7. The improvement in a gas turbine wheel as set forth in claim 6 in which the direction of drag will give it a circumferential component such as to decelerate the absolute circumferential movement of the particle.

8. In a gas turbine wheel for expanding gas having during at least part of the expansion nongaseous particles in suspension therein while deriving mechanical power therefrom, said wheel comprising a body symmetrical about an axis and having a series of passages with entrances circumferentially spaced about its outer periphery and axially open discharges at a lesser distance from the axis than and axially spaced from said entrances, the improvement which comprises said passages each having such shape as to provide a decreasing radial component of velocity and an increasing component relative to said wheel tangentially normal thereto to provide a decreasing circumferential velocity thereby decreasing the centrifugal force on such particle at successive locations closer to the axis, and an increasing component in the axial direction.

9. A radial reaction turbine rotor having a backwall and multiple circumferentially spaced blades extending therefrom in one axial direction so-shaped that the axial projection of the path followed by the radially outermost element of flow relative to the rotor and its direction of rotation is radially inward and slightly backward relative to its normal direction of rotation beginning adjacent the periphery of the rotor and is increasingly so relatively backward and axial until almost entirely tangential and axial adjacent its point of discharge, and the path of the radially innermost element has a contour beginning adjacent the periphery of the rotor almost coincident with that of the outermost element and is increasingly backward relative to normal direction of rotation until about 45.degree.-60.degree. with a radius in a circumferential direction.

10. A rotor of the type described in claim 1 in which the inner edges of the discharge ends of the blades extend axially beyond their outer edges.

11. A rotor of the type described in claim 1 in which the outer edges of the discharge ends of the blades extend axially beyond their inner edges.

12. The rotor of claim 2 in which the discharge edge of each blade has a trailing overhanging lip.

13. The rotor of claim 4 in which the inner border of the discharge of each passage has an overhanging lip.

14. The rotor of claim 1 in which the innermost wall of each passage has multiple transverse roughness.

15. The rotor of claim 1 in which the leading wall of each passage has multiple roughness.

16. A radial reaction turbine rotor for expanding gas having during at least part of the expansion nongaseous particles in suspension therein having multiple blades, each blade having a contour parallel to the vector sum of the tangential and centrifugal forces acting on an adjacent suspended nongaseous element of the flowing stream.

17. A rotor according to claim 16 in which the vector sum of forces to which the blade contour is parallel includes also the axial force acting on the adjacent element of the flowing stream.

18. A rotor according to claim 16 in combination with nozzle means positioned to direct a stream tangentially of said rotor into the passageways between the outer ends of the blades thereof but with a small radial component relative to said rotor, said nozzle means having a throat portion long enough so that the drag of a stream flowing therethrough will act on a particle suspended therein long enough to accelerate the particle to substantially the velocity of the stream in the throat portion.