US2410259A

US2410259A - Elastic fluid mechanism

Info

Publication number: US2410259A
Application number: US422837A
Authority: US
Inventors: Birmann Rudolph
Original assignee: FED RESERVE BANK
Current assignee: FED RESERVE BANK; FEDERAL RESERVE BANK
Priority date: 1941-12-13
Filing date: 1941-12-13
Publication date: 1946-10-29
Anticipated expiration: 1963-10-29

Description

. 061.29, 1946. R. BIRMANN ELASTIC FLUID MECHANISM 2 Sheets-Sheet 1 Filed Dec. 13, 1941 ilk/7mm:

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Oct. 29, 1946. R. BIRMANN ELASTIC FLUID MECHANISM 2 Sheets-Sheet 2 Filed Dec 15, 1941 yrzzwigm.

Mr/vfss PPM-- Patented Oct. 29, 1946 mesne assignments, to Federal Reserve Bank of Philadelphia, a corporation of the United States of America Application December 13, 1941, Serial No. 422,837 7 6 Claims.

This invention relates to elastic fluid mechanisms, and more particularlyto the efficient cooling of elastic fluid turbines.

In my U. S. Patent 2,283,176, issued May 19, 1942, there are disclosed methods and means for cooling elastic fluid turbines, particularly of the types operating at very high temperatures through the use of products of combustion as driving fluid, this cooling being effected with at least no substantial loss of energy by imparting heat energy to the cooling gases and then recovering a substantial part of such energy as either pressure of the exhausted gas or rotational effort 2 utilized, but the principle of boundary layer energization is alsoutilized to secure aresulting torque in the direction of rotation of the turbine wheel by the lowering of pressure on the leading side of the turbine blades constituting the walls between the driving gas passages. As the cooling air mingles with the hot driving gas, it is further heated and upon discharge adds to the mass of the discharging jet to promote the driving torque.

The various objects of the invention will become apparent from the following description,

on the turbine Wheel. In the preferred mode of utilization of the invention of said prior patent, the turbine gas passages and the cooling gas passages are separate and alternate about the turbine wheel. The cooling gas passages, which in practice generally handle air, are provided with impeller intake portions adapted to turn the gas flow radially outwardly and thereby effect substantial compression. This portion of the passage is then followed by a portion designed similarly to a turbine bucket from which the gas is discharged rearwardly with respect to the direc-] tion'of rotation. During the compression in the impeller portion of the gas passage, the transfer of heat to the gas is desirably at a minimum, though necessarily sometransfer occurs from the walls of the passage. .A major portion of heat transfer occurs, however, near the completion of the compression and through the portion of the passage joining the impeller and the turbine portions and in the latter portion.v The expansion of the compressed and heated gas causes the transformation of both'the pressure and heat energy to a substantial extent into kinetic energy of the gas, which is discharged in the form of a I high velocity jet relative to the turbine-wheel.

Thus working torque is' applied to the wheel aiding the main driving gases in effecting rotation of the shaft to carry the load. 7

The present invention involves the same basic principles as those outlined above, but results in even more effective recovery of energy from the coolinggas. In accordance with the present invention, the gas is compressed in the impeller portions of passages alternating in a turbine wheel with the driving gas or bucket passages. At substantial completion of the compression, a major quantity of heat is applied to the gases by transfer from the walls of the passages,;and the compressed gases are caused to discharge atsubstantial velocity as before. The dischargehowe ever, is not in this case effected at substantially the axial position of discharge from the driving gas passages, but rather directly al the trailing walls of the driving gas passages substantially in advance, of their discharge ends. By this type of discharge, not only is the force of reaction read in conjunction With the accompanying drawings, in which:

Figure 1 is a diagrammatic sectional view illustrating a portion of a turbine wheel constructed in accordance with the present invention, the

View showing a circumferential projection of a section taken on a surface as indicated at I-l in Figure 3; 4

Figure 2 is va fragmentary'developed section taken on the surface of revolution the trace of which is indicated at 22 in Figure 1, the ordinates of said Figure 2 being in terms of angles rather than circumferential lengths;

Figure 3' is a section similar to Figure 2, but

taken on the surface of revolution the trace of I which is indicated at 3-3 inFigure 1;

Figure 4 is a fragmentarysectional View showing the mode of application of the invention to a turbine having inserted blades, the section through the blade being taken on the radial surface the trace of which is indicated at'4-4 in Figure 5; and g Figure 5 is a fragmentary developed sectional view taken on the cylinder the trace of which is indicated at 5-5 in Figure 4.

Referring first tothe modification of Figures 1, 2 and 3, the turbine wheel indicated'therein is of the same general type as described in detail in said prior patent, and reference may be made theretofor thefundamental principles of design and theassociated parts involved in incorporation of this wheel in a complete mechanism. Thehub of the wheel is indicated at 2, and the blading is integral therewith in order to enable it to withstand the combination of high temperatures and intense centrifugal forces. The turbine bladingis indicated at '4 and provides driving gas passagesli, the form of which will preliminary compression stages. This cooling gas is then subjected to deflection toward a radial direction of flow with consequent additional compression finally reaching a region of l maximum compression in the portions of the turbine blades directly between the iving gas passages. This region of each passage 8 opens adjacent the trailing face of the driving gas pas.- sage in advance of it through a radially elongated slot IE3 shaped in accordance with known principles of nozzle design to form a nozzle arranged to accelerate the compressed coolinggas which will have been heated to a quite considerable extent in the upper portion of the passage, the major heating occurring after compression issubstantially completed. The arrangement is such through the proper design of the parts, taking into account any preliminary compression of the cooling gas and the amount of heat added by conduction from the walls, to impart to the gas issuing from the nozzle slots iii a velocity substantially in excess of the driving gas velocity at the point of communication between the nozzle iii and the driving gas. The discharge is effected in a direction, for example, as indicated, slightly inwardly toward the axis, corresponding to the direction of flow of the driving gas at the location of the nozzle slot. Desirably, the center line of each of the cooling gas passages is at a distance from the axis of rotation in an intermediate portion thereof at least as great as at its intake and discharge portions. Usually since discharge desirably takes place with a radial inward component, the intermediate portion of this axis will be at a greater radius than its discharge portion, as is the case in Figure 1. The net result of this is to provide not only a high reaction force but also on the advancing side of each turbine vane a boundary layer having a velocity substantially exceeding the velocity on the trailing side of each turbine vane. This, in accordance with well-known principles of aerodynamics, results in a net pressure difference across each vane tending to provide a driving torque. It will be noted that this boundary layer is providedat .the radially outermost portions of the wheel so that the torque for a given pressure difference is a maximum. Furthermore, as this boundary layer flows, in a sheet over the vane, it will tend to accelerate the driving gases and will havev further heat. imparted to it so that this acceleration ta es place while its own velocity decreases, the net result being a substantial average increase of kinetic energy of the gases discharged from the drivin gas passages as compared with the kinetic energy which would result from the use of the driving gases alone. In this way, there is recov-.

ered a net energywhich, in a carefully designed wheel, may substantially exceed the ener y put into the cooling gas during its compression by reason of utilization as mechanical .e ergy of a substantial portion of the heat transferred to-the cooling gas, The energy. recovery through the utilization of this energized boundary layer is somewhat greater than is attainable in accordance with the specific disclosure of said prior patent. To secure maximum efficiency, the design of the passages may follow substantially the disclosure of saidprior patent modified slightly to provide the intermingling of the cooling and driving gases as described. In' other words, the impeller passages and driving gas passages are designed as described therein,the vanes present- 7 not particularly critical 4 ing substantially air foil shapes to the flow of both cooling and driving gases.

Besides the advantages just indicated, there are others over the constructions described in said prior patent. The long passages for cooling air extending to the discharge ends of the drivin gas passages are eliminated, thus substantially reducingmanufacturing dimculties which must be concentrated largely on securing proper discharge portions of the cooling gas passages. The inlet portions of the cooling gas passages are as to design, provided their pick-up angles are correct and provision is made for smooth flow. Even if the coolin air passages of the type described in said prior patent are made as narrow as possible from a manufacturing point of view, the thickness of the working blades between the driving gas passages becomes excessive when the cooling passages are extended to the discharge face of the wheel. This excessive thickness results in the necessity for substantial departure from the best airfoil sections and particularly results in a serious reduction in capacity of thewheel due to the fact that so much discharge area must be sacrificed for the cooling air passages and wall thickness. In the present arrangement, however, the sheet of cooling air can be made as thin as de sired and, in fact, a very high velocity of flow consistent with this is desirable. No boundary wall is necessary, and, therefore, a discharge area is attainable.

The high velocities of the cooling air are not only desirable for producing a maximum torque as described above, both by reaction and by reduction of pressure on the trailing walls of the turbine buckets, but provide also ideal conditions for the cooling of the blading, since the rate of heat transfer from a metal surface to a gas flow ing over it increases with the velocity of the gas. At the same time, the relative velocity between the cooling air and driving gas is relatively low so that there is comparatively little heat exchange between the two resulting in the maintenanceof high cooling ability of the cooling air. The improved arrangement accordingly offers numerous advantages, all consistent with each other for the production of maximum efficiency.

The invention is not soleiy applicable to the type of wheel described in Figures 1, Z and 3, but is also applicable to the type of wheel having inserted blades, which is ,quite practical for lower temperature and lower speed operation. Figures i and 5 show the application of the principles of theinvention to such type of mechanism.

The turbine wheel in this embodiment of the invention is indicated at 12 carried by a hollow shaft l4 designed to provide for the flow-of cooling air through passages it to the blading, compression taking place in passages 55 which function as impeller passages. The periphery of the wheel is designed, as indicatedat it, to carry the blades l8, which are formed integral with blocks 20 suitably interengaged with the disc. The

' blades i8 may have generallyconventional-shape,

stantially in advance of the discharge ends of the buckets, thereby providing a boundary layer of the cooling gas moving at a higher velocity than the driving gas passing through the driving gas passages, to produce a resulting pressure difference across each blade H8 in the same fashion as described in connection with the previous modification.

It will be evident that the invention may be embodied in turbines generally, in forms other than those specifically indicated.

What I claim and desire to protect by Letters Patent is:

1. An elastic fluid mechanism including a re. tor mounted for rotation about an axis and'provided with turbine passages, means for directing hot driving fluid into the turbine passages, and passages for elastic cooling fluid adjacent to said turbine passages, each of said elastic cooling fluid passages opening, through a nozzle constructed vided with turbine passages, means for directing hot driving fluid into the turbine passages, and passages for elastic cooling fluid adjacent to said turbine passages, each of said elastic cooling fluid passages opening, through a nozzle constructed and arranged to expand the cooling fluid and impart to it a high velocity at least of the order of magnitude of the velocity of the driving fluid through the turbine passages, adjacent to the trailing wall of a turbine passage to discharge the cooling fluid at such high velocity along said wall in the direction of flow of driving fluid, and

each of said cooling fluid passages having a portion through which flow takes place with a radially outward component of motion to effect compression of the cooling fluid prior to its discharge.

3. An elastic fluid mechanism including a rotor mounted for rotation about an axis and provided with passages for elastic fluid having axially spaced intake and discharge portions and continuous between said portions, said passages extending spirally in the rotor substantially about its axis, as viewed in a radial direction, from their intake portions to their discharge portions, and the center line of each of such passages being at a distance from the axis of rotation in an intermediate portion thereof at least as great as at its intake and discharge portions, the passages being constructed and arranged so that compression occurs in the intake portions thereof, said rotor also being provided with turbine buckets, and means for directing hot elastic. driving fluid to the turbine buckets to effect driving of the rotor and substantial heat transfer to elastic fluid during its flow through said passages, said pas-' sages and turbine buckets being so constructed and arranged that the turbine buckets are closely adjacent to only those portions of each passage beyond its intake portion in which no substantial compression occurs so that the transfer of substantial amounts of heat is confined to such portions in which no substantial compression occurs, and each of such passages being constructed and arranged as a nozzle at its discharge portion to effect therein expansion of the fluid and to discharge it at high velocity backwardly relatively to the rotor along the trailing wall of an adjacent bucket and in the direction of flow of driving fluid through the bucket so that power is imparted thereby to the rotor both by reaction and by reduction of pressure on said bucket wall.

4. An elastic fluid mechanism including a rotor mounted for rotation about an axis, passages for driving fluid in the rotor, and means for directing hot driving fluid to said passages, said rotor being provided with passages for elastic cooling fluid having axially spaced intake and discharge portions and continuous between said'portions, said passages extending spirally in the rotor substantially about its axis, as viewed in a radial direction, from their intake portions to their discharge portions, each passage extending at its intake portion in the direction of approach of cooling fluid to the rotor to scoop up and compress the cooling fluid and imp-art to it an axial component of fl'ow, and each of such passages being arranged as a nozzle at its discharge portion to discharge the cooling fluid rearwardly at high velocity along the trailing wall of an adjacent driving fluid passage and in the direction of flow of driving fluid, said driving fluid passages and cooling fluid passages being so constructed and arranged with closely adjacent portions that compressed cooling fluid receives from the rotor in the cooling fluid passages beyond said intake portions heat from the driving fluid.

5. An elastic fluid mechanism including a rotor mounted for rotation about an axis, turbine passages in said rotor, means for directing hot driving fluid into the turbine passages, and passages located adjacent the turbine passages for elastic cooling fluid having axially spaced intake and discharge portions and continuous between said portions, said passages extending spirally in the rotor substantially about its axis, as viewed in a radial direction, from their intake portions to their discharge portions, each passage extending of cooling fluid to the rotor to' scoop up and at its intake portion in the direction of approach compress the cooling fluid and impart to it an axial component of flow, and each of such pas- I sages being arranged as a nozzle at its discharge portion to discharge the cooling fluid rearwardly at high velocity along the trailing wall of an adjacent turbine passage and in the direction of flow of driving fluid, said turbine passages and cooling fluid passages being so constructed and arranged with closely adjacent portions that compressed cooling fluid receives from the rotor in the cooling fluid passages beyond said intake portions heat from the driving fluid.

6. An elastic fluid mechanism including a rotor mounted for rotation about an axis and provided with turbine passages, means for directing hot driving fluid into the turbine passages, and passages for elastic cooling fluid adjacent to said turbine passages, each of said elastic cooling fluid passages opening adjacent to the trailing wall of a turbine passage and constructed and arranged as a nozzle to discharge the cooling fluid at high velocity, at least of the order of magnitude of the velocity of the driving fluid through the turbine passages, along said wall in the direction of flow of driving fluid, and each of said cooling fluid passages having a portion through which flow takes place with a radially outward component of motion to effect compression of the cooling fluid prior to its discharge.

RUDOLPH BIRMAN N.