Patent Publication Number: US-4321006-A

Title: Gas compression cycle and apparatus therefor

Description:
BRIEF SUMMARY 
     Great difficulties have been encountered in trying to adapt gas turbine drives to automobiles and trucks because of low overall efficiency and cost limitations preventing use of multistage compressors. Attaining pressure ratios in excess of four to one in a single stage centrifugal or mixed flow compressor is impractical because of excessive temperature rise and flow instability. 
     In accordance with the invention a compressor system is provided which substantially alleviates the problems encountered in the prior art. This is accomplished by providing a conventional vaned centrifugal compressor rotor, either single or double sided, and housed to provide a gas inlet and an outlet from the rotor vane passages. Means are provided for admitting a dense material in the form of solid small particles under sufficient pressure to flow at a controlled rate into the rotor vane gas flow passages or into separate radial passages formed in the rotor. The dense particles flow along the pressure faces of the rotor vanes or in the separate rotor radial passages and remain segregated from the gas flow until both pass into the inlet of a vane free radial diffuser. In the entrance of the diffuser the gas and particle streams intimately mix to form a composite flow in which the gas molecules absorb kinetic energy from the dense particles while the latter absorb heat of compression from the gas molecules so that the compression cycle is substantially isothermal. With a radial diffuser having an outlet radius equal to four or more times the inlet radius, pressure ratios at the outlet may be obtained in the order of ten to twenty to one with substantially ninety percent or more of the kinetic energy of the dense particles transferred to the gas stream. Pressure ratios obtained can be controlled by regulation of the quantity of particulate matter allowed to flow per unit of time. The composite flow discharge from the radial diffuser is passed into a centrifugal particle separator where the high pressure gas is separated from the particles and available for end use in a gas turbine, refrigeration cycle or the like with the separated particles being subsequently cooled and returned for recycling. 
     REFERENCE TO PRIOR ART 
     We are aware of the following U.S. letters patent which have some pertinence in the field of the invention: U.S. Pat. Nos. 2,549,818; 3,379,011; 3,729,930; 3,748,057 and 4,027,993. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the invention reference should be made to the detailed description taken in conjunction with the appended drawings in which: 
     FIG. 1 is a side elevation partly in section illustrating a gas compression system in accordance with the invention and; 
     FIG. 2 is a flat developed view partially illustrating the rotor vane and particulate dispensing structure and; 
     FIG. 3 is a cross sectional view taken on line 3--3 of FIG. 1 streamlined particulate feed conduit and; 
     FIG. 4 is a partial vertical sectional view illustrating the invention applied to a double sided centrifugal compressor rotor and; 
     FIG. 5 is a schematic view of a gas turbine power plant utilizing a compressor such as illustrated in FIG. 4 and; 
     FIG. 6 is a fragmentary sectional view of a modified form of the compressor of FIG. 1 ensuring complete segregation of the particles from the gas streams during centrifugal acceleration in the rotor and; 
     FIG. 7 is a fragmentary front elevation of the compressor rotor of FIG. 6 and; 
     FIG. 8 is a developed top plan view of the rotor of FIG. 7 taken on line 8--8 of FIG. 7 and; 
     FIG. 9 is an isometric sketch further illustrating the compressor rotor of FIGS. 6 through 8. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, the reference numeral 1 generally indicates a power source such as an electric motor adapted to drive a shaft 2 journalled in bearings 3 and constituting the drive means for a centrifugal compressor generally indicated by the reference numeral 5. The compressor 5 is divided on the vertical centerline into front housing 6 and a rear housing 8, the upper half of the housings and other compressor structure only being shown. The housing 6 is provided with a bell mouth air inlet 7. The housings are stiffened by a plurality of webs 9 and 10 respectively equally angularly disposed about the horizontal centerline. The housings 6 and 8 enclose a rotor hub 12 rigidly secured to and rotatable with the shaft 2. The rotor hub 12 has secured thereto radial vanes 14 with the entrance portions deflected forward as seen in FIG. 2, to provide a shock free entrance for air received from the inlet 7. The rotor vanes 14 are equally angularly disposed about the horizontal centerline and may number for example 18 vanes with straight radial vanes 15 for example nine in number each disposed between pairs of adjacent vanes 14 (note FIG. 2). 
     The housing elements 6 and 8 together form a radially extending diffuser passage 16 connected at one end to the radial flow passages between the rotor vanes 14 and 15 and at its outer end by means of an annular port 17 into a hollow annular collecting ring 18 which may be if desired in the form of a scroll. The radius R 2  of the outlet of the diffuser 16 is equal to or greater than four times R 1  the radius of the outlet of the compressor rotor vanes 14 and 15. The collector ring 18 as seen in FIG. 1 is provided with a plurality of ports 19 each adapted to be connected to the interior of a particulate separator generally indicated by the reference numeral 20. The separator 20 is of the type disclosed in U.S. Pat. No. 3,535,850 and is a modified form of the separator shown in FIG. 5 of the patent. The separator 20 comprises a cylindrical casing 21 shown in section, and forming a vortex chamber connected at its forward end to the port 19 and is provided with a plurality of radial swirl vanes 22 and with a central streamline body 24 which serves as an anchor for one end of the spin axis of the vortex flow initiated in the housing 21 by the swirl vanes 22. The housing 21 is provided downstream from the swirl vanes 22 with a circumferential groove 26 which collects particulate matter centrifuged outward by the vortex flow and is connected to a discharge conduit 28. The vortex chamber formed by the casing 21 is provided near its outer end with a cusp shaped guide surface 30 surrounding a conical diffuser 32 having a central inlet 34. The diffuser 32 is provided with a wall member 36 which serves as an anchor for the outer end of the vortex spin axis. The diffuser 32 includes radial diffuser vanes 38 which remove the residual spin of the flow and discharges the same to a cylindrical chamber 40 from which clean high pressure air is discharged for utilization in a gas turbine, refrigeration equipment or in closed cycle gas pumping systems. 
     The centrifugal particle separators 20 connected to ports 19, FIG. 1, may number 6 equally angularly disposed about the axis of shaft 2, two only being shown in FIG. 1, the upper one in section as noted. The collector grooves 26 from each separator are connected in series to discharge conduit 28, see FIGS. 6B and 6C, U.S. Pat. No. 3,535,850 previously referenced. The vortex swirl direction in adjacent separators 20 are in opposite directions so as to have the direction of flow in the connected sections of conduit 28 in the same direction, in the manner shown in FIGS. 6B and 6C of the patent. 
     Referring again to FIG. 1, the terminal end of the separated particle conduit 28 connects to a conduit 42 which returns the total particles collected from the separators 20 to the upper end of a reservoir generally indicated by reference numeral 45. The container 45 is provided with an internal cooling coil 46 adapted to circulate a cooling medium from an external source (not shown) to remove heat from the particulate matter returned to container 45. The container 45 has a tapered bottom portion 47 terminating in a discharge conduit 48, flow through which is adapted to be controlled by a valve member 50 actuated by servo or other means to regulate the flow of particulate matter into the compressor. The discharge conduit 48 connects to a feed conduit 52, which in the portion within the compressor inlet bell 7, is preferably of hollow streamline cross section (note FIG. 3). The feed conduit 52 connects to the hollow interior chamber 53 of an annular casing ring 54. The chamber 53 is provided with an annular portion fitted with discharge vanes 55 of airfoil shape and curved (see FIG. 2) to direct the discharge of particulate material in the direction of rotation of the compressor rotor vanes 14 so as to minimize entry shock. 
     The operation of the device disclosed in FIGS. 1 through 3 is as follows: The particulate container 45 is filled with the requisite amount of material which may be spherical particles of carbon, titanium, titanium aluminate or the like with dimensions of the order of from one to ten microns. When the electric motor or other power source 1 is energized shaft 2 of compressor 5 is rotated at high speed driving the rotor hub 12 and vanes 14 and 15 which will draw air or other gas into the inlet bell 7 where it will contact the curved entrance portions of vanes 14 (note FIG. 2) and impelled into the flow passages between the vanes 14 and radial vanes 15. The air accelerated in the vane flow passages will be discharged at high velocity into the entrance of the radial diffuser passage 16. Simultaneously particulate material in the container 45 will flow at a controlled rate past valve element 50 into conduits 48 and 52 into the annular chamber 53 of the casing element 54. The particulate material emerges from the flow spaces between vanes 55 (note FIG. 2) and is directed into the flow spaces between the rotor vanes. The particles will immediately flow into contact with the pressure faces of the rotor vanes and will remain segregated from the adjacent air flowing in the vane passages. The particulate matter will be discharged from the rotor vane passages with a high radial and circumferential velocity into the entrance of the diffuser 16. There the fine particles will mix with the entering compressed air or other gas stream and proceed radially outward in the diffuser page 16 as a composite flow. The air stream component of the composite flow will by viscous friction absorb kinetic energy from the particles so that by the time the composite flow reaches the exit of the radial diffuser 16, a large portion, such as ninety-five percent, of the kinetic energy of the particles will have been transferred to the gas molecules. Further, the particulate matter or particles will absorb the heat generated in compression of the gas so that the cycle will be substantially isothermal. The composite flow will be discharged and from the diffuser passage 16 under high pressure and pass through the annular port 17 into the collector ring 18 and thence through ports 19 into the separators 20, six or more in number, two only being shown in FIG. 1. Upon entering the separator housing 21, the composite flow will meet the swirl vanes 22 which will initiate a vortex flow which will have its spin axis anchored on the rear of the streamline body 24 and the stationary wall member 36. Due to intense rotation at the core of the vortex flow the particulate matter will be separated out by centrifugal force and will travel along the chamber walls to be collected in the annular groove 26 to ultimately be discharged into conduit sections 28 and returned under pressure via conduit 42 to reservoir 45 for cooling and recirculation. In the vortex chamber 21 flow proceeding downstream in part is redirected by the cusp like wall member 30 to carry particulate matter back to the collector groove 26. Clean air with all particles removed passes by port 34 into a radial diffuser chamber 32 with further rotation removed by diffuser vanes 38 and flowing as clean gas under high pressure through discharge chamber 40 for ultimate use in a gas turbine, refrigeration cycle or the like. The theory of centrifugal particle separators of the type above described is more fully disclosed in U.S. Pat. No. 3,535,850 previously referenced. 
     With reference to FIG. 4 there is shown a centrifugal compressor similar in operation to that of FIG. 1 and differing only in employing a double entry impeller. In this figure parts corresponding to FIG. 1 are indicated by the same reference numeral with the subscript a. The compressor 5a is symmetrical about both horizontal and vertical centerlines and includes driving shaft 2a supported by journal bearings 3a. The front and rear housings 6a and 8a are identical and enclose radial and annular diffuser chamber or passage 16a. The housings are provided with identical bell mouth air inlets 7a. The compressor rotor hub 12a has mounted thereon pairs of vanes 14a having curved inlet portions as in FIG. 2 abutting at the vertical centerline to form a continuous vane and with radial intermediate vanes 15a positioned between adjacent pairs of vanes 14a at each end of the rotor 12a is an annular housing 54a with an interior chamber 53a adapted to be connected by conduits 52a to a single particulate chamber such as 45, FIG. 1. The chambers 53a are provided with sets of vanes 55a adapted to direct controlled streams of dense small particles into the space between vanes 14a in the same manner as in the device of FIG. 1. 
     In operation the rotor blades draw in air or other gas through the inlet bells 7a into the inlet portions of the compressor vanes 14a and together with radial vanes 15a deliver merging air streams into the inlet of the vane free diffuser passage 16a. Similar to the action in FIG. 1, particulate matter in the chambers 53a is dispensed by the director vanes 55a into the spaces between adjacent rotor vanes 14a. The dense particles will rest against the pressure faces of vanes 14a and 15a while being centrifugally impelled toward the rotor vane outlets and into the entrance of the radial vane free diffuser 16a where the flow becomes a composite flow which proceeds toward the diffuser outlet in the same manner as in the device of FIG. 1. The principal advantage of the double ended compressor 5a of FIG. 4 is that lower frictional losses in the double entry compressor makes it more suitable for use in a gas turbine power plant. 
     The use of a compressor in accordance with the invention in a gas turbine power plant is illustrated in FIG. 5. In this figure a double sided compressor 5a of the type disclosed in FIG. 4, is employed with a scroll type collector ring 18a delivering the compressed composite flow from the compressor 5a to a single large particle separator 20a of the same type as in FIG. 1. The separated particulate matter is collected in an annular groove 26a and delivered by a conduit 28a to particle storage container 45a whose rate of discharge can be controlled by a servo valve actuator 60 in a known manner. The inlet housings 7a of the compressor 5a are each connected to an air supply conduit 62a which in turn are connected in parallel to a conduit 64. 
     The output of clean compressed air discharged from the separator 20a is led by a conduit 65 to the combustion chamber 66 of a gas turbine power plant generally indicated by the reference numeral 70 and which also includes a turbine section 67 which drives compressor shaft 2a, an exhaust section 68 which has a recuperating heat exchanger 69 in conjunction therewith. The heat exchanger 69 has vanes 71 in contact with the exhaust gases with portions 72 adapted to conduct heat to the inlet air flowing into the heat exchanger and passing out to the compressor 5a via the conduit 64 connected at its outer end to the heat exchanger 69. In this power plant the high pressure ratios obtainable in the diffuser 20a, because of the interchange of energy between the air flow and the particle flow therein, makes it possible to have a high efficiency and still only employ a conventional heat exchanger as a recuperator. 
     With reference now to FIG. 6, there is shown a centrifugal compressor similar to that of FIG. 1 except for means to more thoroughly isolating the particle streams when centrifugally accelerated in the compressor rotor. Parts corresponding to FIG. 1 are indicated by the same reference numeral as in FIG. 1 plus one hundred. 
     As seen in this figure, the compressor generally indicated at 105 has a driving shaft 102 journalled in bearings 103. The compressor has a front housing 106, with bell mouth inlet 107 and a rear housing 108 which together define a radial vane free diffuser passage 116 terminating in an annular outlet passage 117 which discharges into an annular collector ring 118 which may be in the form of a scroll or may be connected laterally to centrifugal separators, not shown, similar to the separators 20 of FIG. 1. 
     The inlet bell 107 of casing 106 is provided with stationary swirl or prerotation vanes 174 having their outlet portions bent in the direction of rotation of the compressor rotor so as to give a shock free entry to the gas or air stream entering the compressor rotor. The swirl vanes 174 are mounted on a stationary core ring 175 whose outer surface is contoured so as to form together with the inner wall of inlet bell 107 a smooth arcuate flow passage between the adjacent inlet swirl vanes 174. The stationary core ring 175 is provided with a central bore 176 adapted to receive the solid particle dispensing means which includes a tubular casing 154 which extends into the bore 176. The casing 154 has a hollow interior 153 communicating with the spaces between the vanes 155 which are adapted to be deflected to distribute particle flow therethrough with a swirl in the same direction of rotation as the centrifugal rotor, as in FIG. 1. The particles dispensing passage 153 is supplied with particles under pressure from a conduit 152, conduit 148 and particle reservoir 145 provided with particle cooling coil 146, and control valve 150 with particle return conduit 142 all intended to function in the same manner as in the device of FIG. 1. The stationary core ring 175 is provided with a longitudinally extending narrow annular slot 178 intended to serve as a labyrinth seal in conjunction with a hollow cylindrical projection 179 of the compressor rotor hub structure 180. The rotor is made from a solid metal cylinder bored out to form the central conical cavity 181. The rotor blank is milled out to form narrow rectangular slots 182 extending radially from the central cavity 181, to the rotor outlet. The slots 182 are closed on their rear sides by a web 183, note FIGS. 7, 8 and 9, formed in milling the slots in the rotor blank. The slots 182 are closed on their front sides by thin metal fingers 184, note FIGS. 6 and 7, secured at their inner ends to the annular ring 178, the fingers and ring being brazed or otherwise bonded to the rotor body. The radial rotor slots 182 may be equangularly spaced about the rotor periphery for example every 10° or a total of thirty-six slots. The rotor vanes 185 are formed by milling arcuate wedge shaped cavities 186 between the slots 182 leaving thin webs 185 on each side to in part define part of the walls of the slots 182. The rotor vanes each are formed by a pair of thin webs 185, the slot 182 and slot closure strip 184. The rotor vane passages are formed by the milled out cavities 186, note FIG. 9. The cavities 186 are open on their front side and adapted to receive air drawn in through inlet bell mouth 107, past the stationary prerotation vanes 174 into the rotor vane passages, cavities 186 and impacted by the vanes 185 forming the side walls of the cavities 186. Air entering the cavities 186 is centrifuged radially outward and discharged into the entrance of the radial vane free diffuser passage 116. 
     At the same time cooled particles are driven by pressure from the particle reservoir 145 past valve 150 into conduits 148 and 152 into chamber 153 and discharged from the spaces between the vanes 155 where the particle streams are given a whirl in the direction of rotation of the compressor rotor 180 to attain shock free entrance. The flow from the vanes enters the conical bore 181 of the rotor 180 and directly passes into the radial passages 182 in direct communication therewith. The particles entering the rectangular vane passages or slots 182 are centrifuged radially outward and discharged with high velocity between adjacent streams of air or gas from the cavities 186. Because the slots or passages 182 extend substantially over the full width of the rotor 180 a more even discharge of the particles into the inlet of the diffuser is achieved. The alternate streams of air or gas, and particles entering the diffuser 116 form a more uniform composite flow than in the device of FIG. 1 and a more complete transfer of kinetic energy from the particles to the gas and heat from the gas to the particles is achieved. To achieve good results it is essential that the exit radius R 2  of the diffuser 116 be at least four or more times the exit radius R 1  of the compressor 105. 
     The discharge of the composite flow from the diffuser 116 outlet port 117 into the collector ring 118 is the same as in the previous forms of the invention. Though not shown, it is contemplated that centrifugal particle separators such as 20 of FIG. 1 will be employed to separate the particles from the high pressure gas stream. The particles separated will be returned via conduit 142 to reservoir 145 for cooling and recirculation as in the device of FIG. 1.