BACKGROUND

[0001] The present invention relates to a gear driven compressor system. More particularly, the invention relates to a gear driven multi-stage compressor system including a screw expander.

[0002] Multi-stage compressors can be driven by a single prime mover such as a motor using a gear box that includes multiple drive outputs.

SUMMARY

[0003] In one embodiment, the invention provides a compressor system that includes a gear box having a first drive gear, a second drive gear and a first driven gear. A prime mover is coupled to the first drive gear and is operable to input rotational power to the gear box and a compressor is coupled to the first driven gear and is operable in response to rotation of the first driven gear to produce a flow of compressed gas. A heat exchanger is positioned to receive the flow of compressed gas and a flow of fluid and is operable to cool the flow of compressed gas and heat the flow of fluid to produce a flow of heated gas. A screw expander is coupled to the second drive gear and is operable in response to the flow of heated gas to input rotational power to the gear box.

[0004] In another construction, the invention provides a compressor system that includes a prime mover directly connected to a first drive gear and operable to produce a first torque in response to operation of the prime mover and a screw expander directly connected to a second drive gear and operable in response to a flow of heated gas to produce a second torque. A first compressor is directly connected to a first driven gear and is operable in response to rotation of the first driven gear to produce a first flow of compressed gas and a second compressor is directly connected to a second driven gear and is operable in response to rotation of the second driven gear to receive the first flow of compressed gas and produce a second flow of compressed gas, wherein the first drive gear and the second drive gear cooperate to directly rotate the first driven gear and the second driven gear. [0005] In another construction, the invention provides a compressor system that includes a first compressor rotatable to produce a first flow of compressed gas, a second compressor rotatable to receive the first flow of compressed gas and produce a second flow of compressed gas, and a first heat exchanger positioned to receive and cool the first flow of compressed gas before directing the first flow of compressed gas to the second compressor. A second heat exchanger is positioned to receive and cool the second flow of compressed gas and a pump is operable to direct a flow of fluid to the first heat exchanger and the second heat exchanger to produce a flow of heated fluid. A prime mover is operable to produce a first torque and an expander is operable in response to the flow of heated fluid to produce a second torque. The first torque and the second torque cooperate to rotate the first compressor and the second compressor.

[0006] Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Fig. 1 is a rear perspective view of a compressor system including a screw expander;

[0008] Fig. 2 is a front perspective view of the compressor system of Fig. 1 including the screw expander;

[0009] Fig. 3 is a partially broken away side view of the compressor system of Fig. 1 ;

[0010] Fig. 4 is a schematic illustration of the compressor system of Fig. 1 ;

[0011] Fig. 5 is a top broken away view of a prior art screw expander suitable for use in the compressor system of Fig. 1; and

[0012] Fig. 6 is a side broken away view of the prior art screw expander of Fig. 5. DETAILED DESCRIPTION

[0013] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms "mounted," "connected,"

"supported," and "coupled" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, "connected" and "coupled" are not restricted to physical or mechanical connections or couplings.

[0014] Figs. 1-3 illustrate a portion of a compressor system 10 integrated into one compact assembly. The compressor system 10 includes a tank 15, a gear box 20, a first stage compressor 25, a second stage compressor 30, and an expander 35. The tank 15 contains a quantity of lubricant and also functions as a base that supports the remaining components. The lubricant both lubricates and cools the various components during operation. In some constructions, filters, moisture separators, lubricant separators, and the like are supported on the tank 15 or within the tank 15 to condition the lubricant during use.

[0015] The gear box 20 includes a housing 40 that attaches to the tank 15 and contains a plurality of gears arranged in a meshing relationship to provide the desired rotational torque to the first stage compressor 25 and the second stage compressor 30. The gears are arranged to rotate about a plurality of parallel axis that are substantially horizontal. Of course, other arrangements are possible including vertical shaft arrangements or helical gear arrangements in which some of the rotational axes are not parallel.

[0016] A drive shaft 45 extends from the gear box housing 40 and supports a gear 50 (shown in Fig. 4) that is in meshing relationship with one or more gears within the gear box 20. The drive shaft 45 extends from the gear box 20 on the opposite side of the gear box 20 as the first stage compressor 25, the second stage compressor 30, and the expander 35. This arrangement provides room for a prime mover 55 to attach to the gear box 20 and to engage the drive shaft 45 to input a torque into the gear box. In preferred constructions, an electric motor attaches to the drive shaft and provides the desired torque. Of course, other prime movers 55 such as internal combustion engines, diesel engines, combustion turbines, and the like could be employed in place of, or in conjunction with the electric motor.

[0017] A lubricant pump (not shown) directs lubricant from the tank 15 to the various gears within the gear box 20 to provide lubrication and cooling. The lubricant is contained by the housing 40 and drains to the bottom of the housing 40 where it is collected and returned to the tank 15.

[0018] The first stage compressor 25 includes a first casing 60 that supports a rotating element. The first casing 60 attaches to the gear box housing 40 to support the first stage compressor 25 in an operating position. In the illustrated construction, the first stage compressor 25 is a rotary screw compressor that includes a drive screw having a drive shaft 65 that extends out of the first casing 60. A first driven gear 70 (shown in Fig. 4) is attached to the drive shaft 65 and meshes with one or more gears in the gear box 20 to facilitate rotational operation of the first stage compressor 25.

[0019] The first casing 60 includes an inlet 75 that provides a flow path for atmospheric air 185 into the compressor 25. In some constructions, a filter is provided to filter the air 185 before it enters the first casing 60. In other constructions, a gas supply is connected to the inlet 75 to provide a flow of a gas other than air to the compressor 25. The first casing 60 also defines an outlet 80 that provides a flow path for compressed gas 190 to exit the first stage compressor 25.

[0020] The second stage compressor 30 includes a second casing 85 that contains and supports a rotating element for rotation. The second casing 85 attaches to the gear box housing 40 to support the second stage compressor 30 in an operating position. In the illustrated construction, the second stage compressor 30 is a rotary screw compressor that includes a drive screw having a drive shaft 90 that extends out of the second casing 85. A second driven gear 95 (shown in Fig. 4) is attached to the drive shaft 90 and meshes with one or more gears in the gear box 20 to facilitate rotational operation of the second stage compressor 30.

[0021] The second casing 85 includes an inlet 100 that provides a flow path for gas 190 into the second stage compressor 30. As the second stage compressor 30, the gas 190 is received either directly, or indirectly from the first stage compressor 25. In preferred constructions, the compressed gas 190 is treated before it enters the second stage compressor 30. Treatment could include a drying process, an intercooling process, an oil separation process or the like. The second casing 85 also defines an outlet 105 that provides a flow path for compressed gas 195 to exit the second stage compressor 30.

[0022] In some constructions, oil-flooded screw compressors are employed as the first stage compressor 25 or the second stage compressor 30. In these constructions, lubricant is drawn from the tank 15 and directed into the first stage compressor 25 or the second stage compressor 30 to lubricate and cool the rotating elements. In preferred constructions, oil-less screw compressors (sometimes referred to as dry compressors) or other rotary compressors are employed as the first stage compressor 25 or the second stage compressor 30.

[0023] The expander 35 includes an expander casing 110 that contains and supports one or more rotary elements 1 15. The expander casing 1 10 attaches to the gear box housing 40 to support the expander 35 in the desired operating position. As illustrated in Fig. 3, one of the rotary elements 1 15 includes a drive shaft 120 that extends through the casing 1 10 and supports a drive gear 125. The drive gear 125 meshes with one or more gears in the gear box 20 to facilitate the input of torque by the expander 35 into the gear box 20.

[0024] The expander casing 1 10 includes an inlet aperture 130 and an outlet aperture 135. In a preferred construction, steam 175 enters the expander casing 110 through the inlet 130, passes through the rotary elements 1 15 where the steam 175 expands and imparts rotational energy to the rotary elements 115, and then exits the casing 110 via the outlet aperture 135. In some constructions, other gases are employed in place of steam 175 as the working fluid.

[0025] In the illustrated construction, the expander 35 is a rotary screw expander 35 such as the one illustrated in Figs. 5 and 6. The rotary screw expander 35 includes a drive screw 1 15a and an idler screw 115b that meshes with and rotates with the drive screw 115a. The steam 175 enters in the small spaces between the meshing screws 1 15a, 1 15b and forces the screws 115a, 115b to rotate. As the screws 1 15a, 1 15b rotate, the spaces expand until the steam 175 is discharged from the rotary screw expander 35. Of course, other constructions could employ other devices in place of the rotary screw expander 35. For example, some constructions may employ a radial or axial flow turbine in place of or in conjunction with the rotary screw expander 35. [0026] Fig. 4 schematically illustrates the portion of the compressor system 10 of Figs. 1- 3 incorporated into a full compressor system 140 that includes a first stage intercooler 145, a second stage intercooler 150, and a steam cycle 155 that provides steam 175 to the expander 35. The first stage intercooler 145 includes a first heat exchanger 160 positioned to receive the flow of compressed gas 190 from the first stage compressor 25, cool the flow of compressed gas 190, and direct the flow of compressed gas 190 to the second stage compressor 30.

[0027] The second stage intercooler 150 includes a second heat exchanger 165 positioned to receive the flow of compressed gas 195 from the second stage compressor 30, cool the flow of compressed gas 195, and direct the flow of compressed gas 195 to a point of use or other downstream process. It should be noted that other components such as moisture separators, filters, oil separators, and the like could be positioned upstream or downstream of either one of the first stage heat exchanger 160 or the second heat exchanger 165.

[0028] The steam cycle 155 includes a pump 170 positioned to pump water 200 to the second stage intercooler 150. The water 200 operates to cool the flow of compressed gas 195 as it passes through the second stage intercooler 150 and is in turn heated. The water 200 exits the second stage intercooler 150 and flows to the first stage intercooler 145. The water 200 flows through the first stage intercooler 145 and cools the compressed gas 190 as the gas 140 flows through the first stage intercooler 145. Again, the water 200 is heated as it cools the compressed gas 190 in the first stage intercooler 145. At some point between where the water 200 enters the second stage intercooler 150 and exits the first stage intercooler 145 the water 200 boils and transitions to a flow of steam 175.

[0029] The flow of steam 175 is directed to the expander 35 and flows through the expander 35 as discussed. After passing through the expander 35, the steam 175 flows to a condenser 180 and is cooled and condensed to water 200 which is collected in the bottom of the condenser 180. The water 200 is then drawn from the condenser 180 by the pump 170 to complete the steam cycle 155.

[0030] With continued reference to Fig. 4, the motor or prime mover 55 drives the first drive gear 50 to input torsional power into the gear box 20. The expander 35 drives the second drive gear 125 such that the expander 35 also provides torsional power to the gear box 20. In some constructions, a clutch mechanism is positioned between the expander 35 and the gear box 20 to inhibit rotation of the expander 35 when the expander 35 is not providing power to the gear box 20. In preferred constructions, the motor, or other prime mover 55, provides most of the torsional power. However, other constructions could employ larger expanders 35 that provide a larger percentage of the power to the gear box 20.

[0031] The drive shaft 65 of the first stage compressor 25 is coupled to the first driven gear 70 such that torsional power is applied to the first stage compressor 25 by the gear box 20. Similarly, the drive shaft 90 of the second stage compressor 30 is coupled to the second driven gear 95 such that torsional power is applied to the second stage compressor 30 by the gear box 20.

[0032] It should be noted that the size of the gears 50, 70, 95, 125 illustrated in Fig. 4 are selected for the convenience of the figure and do not necessarily represent the actual gear ratios between the various components. One of ordinary skill in the art would understand that the gear ratios selected for the compressor system 140 would be selected based on the desired operating speeds of the various components. It should also be noted that additional gears, such as idler gears, may be necessary to interconnect the gears 50, 70, 95, 125 as desired and to provide the desired gear ratios. It should also be noted that in some constructions, a belt drive or chain drive could be employed in place of some of the gears 50, 70, 95, 125 if desired.

[0033] The compressor system 140 illustrated herein utilizes the heat of compression to produce steam 175 that is used in an expander 35 to reduce the power required to drive the compressor stages 25, 30. The illustrated system thus reduces the energy used to compress a gas and improves the efficiency of the compressor system 140. In some constructions, an external source of heat 300 may be available. The external heat source 300 may be used with a heat exchanger 305 to replace or supplement the heat of compression to produce steam 175. For example, heat from an external industrial process or heat from an internal combustion engine may be available to produce additional steam 175, thereby facilitating the use of a larger expander 35 or an expander 35 that inputs a greater percentage of the total torque to the gear box 20. It should also be noted that similar systems could be employed to drive a single stage compression system or compressor systems with three or more stages. [0034] Thus, the invention provides, among other things, a compressor system 140 that uses heat of compression to drive an expander 35 to improve the efficiency of the compressor system 140.