Rotary regenerative heat exchanger
United States Patent Penny Apr. 29, 1975 l5 l ROTARY REGENERATWE HEAT 3.039265 6/l962 Williamsct al. 165/7 x EXCHANGER 3.232.335 2/1966 Kalhfleisch 165/9 [76] Inventor: Robert Noel Penny, l1 Alderbrook solihunawarwickshire Prmrury E.\&#39;mnmerAlbert W. Davis, Jr. England Allurney, Agent. or Firm-Hanke, Gifford, Patalidis &amp; Dumorit 22] Filed: Dec. 7. 1972 [-1] Appl. No. 3l3,l74 [57] ABSTRACT A rotarv regenerative heat exchanger including a de- 30 F A l t P l I U pp i Data g were for detecting the rate of flow of leakage of heat l Umml 890ml exchange fluid between a seal and the relevant surface of the matrix and for controlling the application of 2? 3 63 pressurizing fluid to a pressurized seal in response to g &#39;l 2 9 the detected rate of leakage flow, thereby to control l 0 l the rate of leakage flow of heat exchange fluid and to Referenceg Cited maintain it at a desired value.  
 UNITED STATES PATENTS 4 Claims, 3 Drawing Figures 2.747.843 5/1956 Cox ct all. 165/7 X II II n 1 I 5 1 a ll lb 7 l i l2 &#34;g 3 4 IO 1} 4 l7 l9 s ROTARY REGENERATIVE HEAT EXCHANGER BACKGROUND OF THE INVENTION l. Field of the Invention The invention relates to a rotary regenerative heat exchanger having a matrix in which flow paths therethrough for the fluids between which heat exchange is to be effected are defined by seals of the kind to which a pressurizing fluid is applied to control the loading of the seal on the relevant surface of the matrix. Such seals are usually in the form of bellows.  
 I. Prior Art Where the loading of a seal is too great, excessive wear of the seal or matrix surface or both will occur. Where the loading of a seal is too small, there will be excessive leakage of heat exchange fluid between the seal and the matrix. The loading of a pressurized seal can be controlled by adjusting the pressure of pressurizing fluid applied to the seal to a value at which there is correct running clearance between the seal and the matrix surface.  
 SUMMARY OF THE PRESENT INVENTION According to the invention, a rotary regenerative heat exchanger comprising a matrix, seals defining the flow paths through the matrix for the fluids between which heat exchange is to be effected and means by which at least one of the seals is arranged to be subjected to a pressurizing fluid to effect a desired seal loading, includes means for detecting the rate of flow of leakage of heat exchange fluid between a seal and the relevant surface of the matrix and means for controlling the application of pressurizing fluid to the pressurized seal or seals in response to the detected rate of leakage flow, thereby to control the rate of leakage flow of heat exchange fluid and to maintain it at a desired value.  
  Preferably duct means are provided adjacent a seal to lead leakage flow of fluid to a fluid-responsive device arranged to control the supply of pressurizing fluid applied to the pressurized seal or seals.  
  The fluid-responsive device may comprise a pressure-actuated spool valve connected to admit pressurizing fluid to or to exhaust fluid from the pressurized seal or seals. The spool valve may be operated by a piston or diaphragm responsive to the pressure of leakage fluid.  
  Alternatively the leakage fluid may be applied to a fluidic switching device arranged to admit pressurizing fluid to or to exhaust fluid from the pressurized seal or seals.  
  In yet another arrangement, the leakage fluid may be applied to a pressure transducer arranged to operate electrical means for applying pressurizing fluid to or to exhaust fluid from the pressurized seal or seals. The electrical means could be a switch controlling an electric motor or a solenoid arranged to move a fluid control valve.  
  Whichever means of detecting the rate of leakage flow of heat exchange fluid and controlling the pressure of pressurizing fluid applied to the seal is employed, the control means is adjusted to control the internal fluid pressure in the seal to a value at which there is a predetermined rate of leakage flow of heat exchange fluid between the seal and the adjacent matrix surface, thereby ensuring that the seal loading is maintained at its desired value to minimize wear and leakage of fluid.  
  The pressurized seal or seals may be in the form of pistons or diaphragms to which the pressurizing fluid is applied. Alternatively the pressurized seal or seals may be in the form of bellows or other internally pressurized device to which the pressurizing fluid is applied.  
  The pressurizing fluid may be one or other of the fluids between which heat exchange is to occur or it may be another source of pressurizing fluid.  
 BRIEF DESCRIPTION OF THE DRAWINGS By way of example, a rotary regenerative heat exchanger in accordance with the invention is now described with reference to the accompanying drawings, in which:  
  FIG. 1 is an axial section through the heat exchanger showing a pressure-actuated spool valve for controlling the application of a pressurizing fluid to pressurized seals of the heat exchanger,  
 FIG. 2 is a section on the line II-II in FIG. I, and  
  FIG. 3 is a fluidic switching device employed in place of the spool valve shown in FIG. 1.  
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, the heat exchanger comprises a disc-like matrix 1 mounted for rotation by a shaft 2 in a housing 3. The matrix I has a plurality of pores of passages 4 extending parallel with the axis of rotation of the matrix and through which during operation of the heat exchanger the fluids, e.g., compressed air and exhaust gases from a turbine ofa gas turbine engine, are passed in two separated streams defined by seals 5 and 6 engaging the ends of the matrix. The seal 5 defines in one end of the housing 3 a region 7 to which compressed air from a compressor (not shown) of the gas turbine engine is supplied and a region 8 through which exhaust gases from the turbine (not shown) are exhausted after passing through the matrix. The seal 6 defines in the other end of the housing 3 a region 9, opposite the region 7, through which the compressed air stream after having been passed through the matrix is passed to a combustion chamber (not shown) of the engine and a region 10 opposite the region 8 through which exhaust gases from the turbine are passed through the matrix. The seal 5 incorporates or is engaged by a bellows 11 which is internally pressurized to urge the seal 5 axially towards the matrix 1 and the latter axially against the seal 6. The bellows 11 is connected by a pipe 12 to spool valve 13 which is movable either to admit compressed air tapped from the region 9 through a duct 14 or to exhaust compressed air from the bellows 11 and the pipe 12 through an exhaust duct 15;  
  The portion of the interior of the housing 3 surrounding the outer periphery of the seals 5 and 6 and the matrix 1 and containing the bellows 11 receives compressed air that has leaked between the seals and the end faces of the matrix as indicated by arrows 16. The leakage air is led through a pipe 17 having a restricted mouth to a chamber 18 containing a piston 19 carrying a cup washer 20 mounted on one end of the spool 21 of the spool valve 13. The piston 19 is urged by a spring 22 in the direction in which the spool valve will bleed compressed air from the interior of the bellows 11 through the pipe 12 and the exhaust duct 15.  
  The operation of the pressure-actuated spool valve is as follows: when leakage of compressed air in the direction of arrows 16 increases, for example, due to wear,  
 the piston 19 will be moved downwardly as in FIG. I, against the spring 22. This will have the effect of admitting compressed air through the spool valve 13 to the bellows 11 to decrease the leakage flow. If the sealing load should become too great. i.e., the leakage flow decreases. the spring 22 will move the piston 19 upwardly. with respect to FIG. 1, thereby moving the spool 21 to a position in which air in the bellows ll will be exhausted through the spool valve I3 to the exhaust duct 15. In this way the leakage flow of compressed air as indicated by arrows 16 can be kept substantially con stant, thereby maintaining the seal loading substantially constant and thus minimizing wear of the seals and the matrix end faces.  
  Instead of the pressure-actuated spool valve 13 shown in FIG. 1, the pipe 17 can be connected to a fluidic switching device such as that shown in FIG. 3. In the switching device 25 shown diagrammatically in FIG. 3, the pipe 12 is normally in registration through the device 25 with the exhaust duct 15 but when the pressure in the pipe 17 ie. the leakage pressure, increases. the fluid flow from the pipe 14 is deflected to admit compressed air flowing through the duct 14 to flow through the pipe 12 to the bellows 11.  
  Instead of the pressure-actuated spool valve 13 or fluidic switching device 25, the pressure in the pipe 17 may be used to operate a pressure transducer and this may in turn actuate an electrical switch for effecting operation of an electric motor or a solenoid arranged to move a fluid control valve for admitting compressed air from the duct 14 to be admitted to the pipe 12 or compressed air in the pipe I2 to be exhausted through the duct 15.  
  What I claim as my invention and desire to secure by Letters Patent of the United States is:  
  I. A rotary regenerative heat exchanger comprising a rotatable disc-like matrix having heat exchange passages therein extending between end faces of the ma trix, and seals co-operable with said end faces and delining areas thereof through which the fluids between which heat exchange is to be effected will flow in separated streams, at least one of said seals being in the form of a closed loop and having a hollow bellows-like cross-section and inlet means communicating with the interior of said hollow seal for the admission thereto of a pressurising fluid, the head exchanger also including means for detecting the rate of flow of leakage of heat exchange fluid between one of said seals and the adjacent end face of the matrix, a fluid-responsive device to control the supply of pressurising fluid to said pressurised seal in response to the detected rate of leakage flow and duct means provided adjacent said one seal to lead said leakage flow of fluid to said fluid-responsive device.  
  2. A heat exchanger as claimed in claim 1 in which said fluid-responsive device comprises a pressureactuated spool valve connected to control application of pressurising fluid to said pressurised seal.  
  3. A heat exchanger as claimed in claim 2 in which said spool valve includes an operating piston responsive to the pressure of said leakage fluid.  
  4. A heat exchanger as claimed in claim 1 in which said fluid-responsive device is a fluidics switching device controlled by said leakage fluid and connected to apply said pressurising fluid to said pressurised seal.