US2983111A

US2983111A - Refrigeration machine and method of controlling same

Info

Publication number: US2983111A
Application number: US774351A
Authority: US
Inventors: Robert G Miner; Joseph R Lejk
Original assignee: Trane Co
Current assignee: Trane Co
Priority date: 1958-11-17
Filing date: 1958-11-17
Publication date: 1961-05-09
Anticipated expiration: 1978-05-09

Description

May 9, 1961 R. G. MINER ETAL 2,983,111

REFRIGERATION MACHINE AND METHOD OF CONTROLLING SAME Filed Nov. 17, 1958 2 Sheets-Sheet 1 INVENTORS ROBERT e. MINER JOSEPH R. LEJK Wy W ATTOR N E YS R. G. MINER ETAL 2,983,111

REFRIGERATION MACHINE AND METHOD OF CONTROLLING SAME Filed Nov. 17, 1958 2 Sheets-Sheet 2 May 9, 1961 5333930 NI 9N|N3d0 3/nvA INVENTOR. ROBERT G. MINER JOSEPH R4 LEJK BY MW W ATTORNEYS United States Patent O REFRIGERATION MACHINE AND METHOD OF CONTROLLING SAME Robert G. Miner, La Crosse, and Joseph R. Lejk, Onalaska, Wis., assignors to The Trane Company, La Crosse, Wis., a corporation of Wisconsin Filed Nov. 17, 1958, Ser. No. 774,351

11 Claims. (Cl. 62-115) This invention relates to a refrigeration machine having a turbine driven centrifugal compressor and to a method of controlling such machine.

With refrigeration machines of this type, it is important to be able to vary the output from full capacity to a small percentage of full capacity with good efliciency over the range and without developing in the compressor a condition of surge. Surge is an unstable condition during which the gas periodically flows through the compressor in a direction from the discharge to the suction.

It is an object of this invention to provide a control for turbine driven centrifugal comprmsors which will economize on the use of the steam or other motive fluid.

It is another object of the invention to provide a con trol which reduces the output of the compressor from full output by first reducing the speed, secondly, further reducing the output by closing the prerotation inlet guide vanes while simultaneously increasing the speed.

It is another object of the invention to provide a method of controlling a refrigeration machine to conserve the use of motive fluid and to avoid surging conditions.

Other objects and advantages of the invention will appear as the specification proceeds to describe the invention with reference to the accompanying drawings in which:

Fig. l is a diagrammatic view of the refrigeration machine and control system of this invention;

Fig. 2 is a partial view of the compressor partly in section on an axial plane;

Fig. 3 is a diagram showing the cycle of operation of the governor and the inlet vanes; and

Fig. 4 is a diagram showing the cycle of operation of the valves which determine the speed at which the governor controls. 7

Referring now to Fig. l, a compressor 10 has an impeller 12 which is driven by a turbine 14. The compressor 10 discharges refrigerant gas under pressure to a conduit 16 through which the gas flows into a condenser 18. The condenser 18 has a coil 20 which receives water or other cooling fluid from a source 22. The cooling water is discharged from the coil 20 through a conduit 24. The condensed refrigerant flows from the condenser 18 through a conduit 26 to an evaporator 28 which is preferably of the shell and tube type in which a secondary refrigerant liquid such as chilled water or brine flows through the tubes 30. The chilled water or brine from a refrigeration load flows to the evaporator 28 through conduit 32 andreturns from the evaporator 28 to therefrigeration load through a conduit 34. The refrigerant liquid in the evaporator 28 boils to form gas which passes through suction pipe 36 to the compressor 12.

Steam or other motive fluid flows to'the turbine 14 through a valve 38 from a source 40. A rod 42 actuates the valve 38. The rod 42 moves to the right as viewed in Fig. l to open the valve 38. A bell crank 44 is pivotally mounted on a fixed abutment 46 and has one pivotally secured at 50 to the piston 52.

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An oil pump 54 is driven by the shaft of the turbine 14 as indicated by line 55 and receives oil through conduit 56. The pump 54 discharges the oil under pressure to conduit 58 which conducts the oil to the bellows chamber 60 of the governor 62. A valve member 64 is in threaded engagement with the body of the governor 62 and is adjustable to determine the flow of oil from the bellows chamber 60 through orifice 65. A bellows 66 is mounted in the bellows chamber 60 and has its interior connected by passageway 68 to the passageway 70 downstream from the orifice 65. A spring 72 opposes the force of the oil pressure on the outside of the bellows 66. A stem 74 is secured to the bellows 66 and acts upon a lever 76 pivoted at 78 on the piston 52. A pilot valve 80 is pivotally secured to lever 76 at 82. A spring 83 acts to raise pilot valve 80. Movement of the valve 36 to one position connects fluid pressure to the chamber 84 through

passageways

86, 88, and 70. Movement of valve 86 to another position connects fluid pressure to the chamber 90 through

passageways

92, 94, and 70. Fluid from chambers 84 and 90 exhausts through conduit 96 under the control of the valve 80. It is thus seen that the pressure drop across the orifice 65 determines the amount that the bellows 66 is compressed, that the extent of the bellows 66 deter I ment of piston 52 opens steam valve 38 and downward movement closes steam valve 38. Should the speed rise, the pressure drop across the orifice 65 is increased and the bellows 66 lowers, forcing the valve 80 down admitting oil to the top of the piston 52, which forces it downward to reduce the opening of valve 38. Reduction of opening of valve 38 brings the speed hack to the control point. The reverse action would occur if the speed tended to decrease below the control point. 7

If the valve member 64 is adjusted to reduce the opening of orifice 65, the pressure drop across orifice 65 would be increased forcing the bellows 66 downward until equilibrium is restored at a new lower speed.

In order to control the speed of operation of the turbine 14, pneumatically controlled valves 97 and 98 are connected to receive fluid from bellows chamber 60 through conduit 99. Fluid from valves 97 and 98 flows through conduit 100 to passageway 70 and to pressure relief valve 101 which may be set to regulate the pressure at about 45 pounds per sq. in.

From the pressure relief valve 101, the fluid passes through a conduit 103 to the bearings of the turbine 14 and to a pressure relief valve 105 which is set to regulate the pressure in conduit 103 at about 15 pounds per sq. in. From pressure relief valve 105, the fluid flows through conduit 107 to conduit 96 which conducts the fluid back to the turbine 14.

Valve 97 is connected by conduits 102 and 104 to a pneumatic thermostat 106. Valve 98 is connected by conduits 108 and 104 to pneumatic thermostat 106. Pneumatic thermostat 106 has a bulb 110 in temperature sensing relationship with conduit 34 which conducts chilled water from the evaporator 28 to the refrigeration load. It should be understood that the temperature of the leaving chilled water is close to the temperature of the evaporator and that the bulb 110 could be' mounted in the evaporator, if desired, so that it is responsive to evaporator temperature. The pneumatic thermostat is connected to a source of compressed air 112.

A fluid cylinder 114 has a piston rod 116 which is pivotally connected to a lever 118. As shown in Fig. 2, lever 118 is pivoted to the compressor casing at 120. Lever 118 extends into the compressor casing and a bellows 122 provides a flexible seal between the casing and the lever 118. The inner end of lever 118 is pivotally mounted on a ring 124 which is rotatably mounted on v r 3 V inlet 126, A plurality of radially arranged prerotation inlet guide vanes 128 are pivotally mounted in inlet 126. Each guide vane 128 has a crank 130 secured thereto. Cranks 131} are. pivotally secured to ring 124 so that rotation of ring 124. rotates all of the vanes 128 unison. The vanes 128 are adjustable to'positions In which they are at right angles to the path of flow and substantially prevent flow of gas thus reducing the 'capacity of the machine to substantially zero. The prerotation guide vanes 128 may be adjusted to anglessuch that they guide the refrigerant gas partially in the direction of flow into the impeller, thus causing the-machine to operate at some capacity less than full capacity. The vanes 128 may be adjusted to positions in which they are substantially in planes radial to the axis of the inlet so that there is substantially no prerotation' of the gas. Under this condition, the machine operates at substantially full capacity. It is thus seen that the vanes 128 operate to provide variable throttling means in the suction passageway to the compressor impeller 12. Fluid cylinder 114 receives fluid pressure .from thermostat 106 through conduits 132 and 104.

The method of operation of the device will now be described. Let us assume that the machine is operating at full capacity and the temperature of the chilled water in conduit 34 falls slightly indicating that less capacity is required; Bulb 1*10 senses this drop in temperature and causes thermostat 166 to transmit a lower pressure through conduit 104, and normally closed valve 93 gradually closes because the pressure in conduit 108 is always the same as that in conduit 104. The reduced flow of fluid from bellows chamber at through conduit 99 and valve 98 increases'the pressure in bellows chamber 60 and consequently bellows 66 is compressed against the :force of spring 72. Stem 74, lever 76 and .valve 80 are therefore lowered. When valve 80 moves downwardly, more fluid is admitted above the piston 52 and more fluid is exhausted from below the piston 52. Consequently, piston 52 moves downwardly and through bell crank 44 and rod 42 moves steam valve 38 toward closed position. Movement of steam valve 38 toward closed position reduces the speed of the turbine and consequently the output of the compressor is reduced.

At full load, the pressure in conduit 104 from thermostat is about 18 pounds. Valve 98 reaches fully closed position at about 13 pounds and the output of the compressor is slightly greater than 75% of full output.

A further drop in temperature of the water in conduit 34 indicates that a further reduction in capacity is required and thermostat 106 reduces the pressure in conduit 104 below '13 pounds. As the pressure in conduit 104 falls below 13 pounds, fluid cylinder 114 gradually closes the inlet vanes 126 to reduce the output of the compressor, and normally open valve 97 gradually opens to increase the speed of the compressor. When the fluid pressure from thermostat 105 drops to three pounds, the vanes 126 are fully closed and the valve 97 is fully open with the result that the turbine is operating at full speed. When the pressure from thermostat 1% tends to drop below three pounds indicating that refrigeration is not required, mechanism (not shown) shuts down the machine.

Although We have described specifically a preferred embodiment of our invention, we contemplate that changes may be made without departing from the scope or spirit of our invention and we desire to be limited only by the claims.

we claim:

'1. A control system for a refrigeration machine having 'a centrifugal compressor, a condenser connected to receive compressed refrigerant from said compressor, an evaporator for removing heat from a heat exchange fluid, said evaporator being connected to said condenser to receive. condensed refrigerant from said condenser,

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conduit for conducting refrigerant from said evaporator to said compressor, means for throttling the flow of refrigerant to said compressor, a turbine connected to drive said compressor, a governor for controlling the speed of said turbine, means responsive to the temperature of the heat exchange fluid of said evaporator for adjusting said governor to control the turbine at a difierent speed and means responsive to the temperature of the heat exchange fluid of said evaporator for varying the effectiveness of said throttling means to vary the output of the compressor.

2. A control system fora refrigeration machine having a centrifugal compressor, a condenser connected to receive compressed refrigerant from said compressor, an evaporator for removing heat from a heat exchange fluid, said evaporator being connected to said condenser to receive condensed refrigerant from said condenser, conduit for conducting refrigerant from said evaporator to said compressor, prerotation angularly adjustable guide vanes in said conduit adjacent said compressor, a turbine connected to drive said compressor, a governor for controlling the speed of said turbine, means responsive to the temperature of the heat exchange fluid of said evaporator for adjusting said governor to control the turbine at a diflerent speed and means responsive to the temperature of the heat exchange fluid of said evaporator for adjusting the inlet guide vanes to vary the output of the compressor.

3. In arefrigeration system, a centrifugal compressor, a condenser connected to said compressor to receive compressed refrigerant from said compressor, an evaporator connected to said condenser to receive condensed refrigerant from said condenser, means for conducting a heat exchange fluid to be cooled through said evaporator, conduit for conducting refrigerant from said evaporator to said compressor, prerotation angularly adjustable guide vanes mounted in said conduit adjacent said compressor, a turbine connected to drive said compressor, a valve for controlling the flow of driving fluid to said turbine, a governor responsive to the speed of said turbine to control the position of said valve to control the speed 1 of said turbine, means responsive to the temperature of heat exchange fluid of said evaporator for adjusting said governor to vary the speed at which said governor controls the turbine, and means responsive to the temperature of the heat exchange fluid of said evaporator for angularly adjustingsaid angularly adjustable prerotation guide vanes to vary the output of the compressor.

4. In a refrigeration system, a centrifugal compressor, a condenser connected to said compressor to receive cornpressed refrigerant from said compressor, an evaporator connected to said condenser to receive condenser refrigerant fromsaid condenser, means for conducting a heat exchange fluid to be cooled through said evaporator, conduit for conducting refrigerant from said evaporator to said compressor, prerotation angularly adjustable guide vanes mounted in said conduit adjacent said compressor, a turbine connected to drive said compressor, a valve for for controlling the flow of driving fluid to said turbine, a governor responsive to the speed of said turbine to control the position of said valve to control the speed of said turbine, fluid means responsive to the temperature of heat exchange fluid of said evaporator for adjusting said governor to vary the speed at which said governor controls the turbine, and fluid means responsive to the temperature of the heat exchange fluid of said evaporator for angularly adjusting said angularly adjustable prerotation guide vanes to vary the output of the compressor.

5. A method of controlling the output of a refrigeration machine having a turbine driven centrifugal compressor comprising reducing the speed of the compressor to reduce its output from substantially full output to a partial output and then further reducing the output of the machine by throttling the flow of the refrigerant entering the impeller of the compressor while simultaneously increasing the speed of the compressor.

6. A method of controlling the output of a refrigeration machine having a turbine driven centrifugal compressor comprising reducing the speed of the compressor to reduce its output from substantially full output to a partial output and then further reducing the output of the machine by causing the refrigerant entering the compressor to prerotate in the direction of rotation of the compressor While simultaneously increasing the speed or" the compressor.

7. A control system for a refrigeration machine having a centrifugal compressor, a condenser connected to receive compressed refrigerant from said compressor, an evaporator for removing heat from a fluid, said evaporator being connected to said condenser to receive condensed refrigerant from said condenser, conduit for conducting refrigerant from said evaporator to said compressor, a turbine connected to drive said compressor, a valve for controlling the flow of motive fluid to said turbine, a pump driven by said turbine for circulating hydraulic fluid, a hydraulic cylinder connected to receive hydraulic fluid from said pump, a piston operating in said cylinder and operatively connected to said valve, means responsive to the magnitude of the speed of rotation of said turbine for controlling the pressure of hydraulic fluid in said cylinder to position said piston in said cylinder and means responsive to the temperature of said evaporator for adjusting said last mentioned means to vary the position of said piston in said cylinder and thereby vary the position of said valve.

8. A control system for a refrigeration machine having a centrifugal compressor, a condenser connected to receive compressed refrigerant from said compressor, an evaporator for removing heat from a fluid, said evaporator being connected to said condenser to receive condensed refrigerant from said condenser, conduit for conducting refrigerant from said evaporator to said compressor, a turbine connected to drive said compressor, a valve for controlling the flow of motive fluid to said turbine, a pump driven by said turbine for circulating hydraulic fluid, a hydraulic cylinder connected to receive hydraulic fluid from said pump, a piston operating in said cylinder and operatively connected to said valve, means responsive to the pressure of hydraulic fluid delivered by said pump for controlling the pressure of hydraulic fluid in said cylinder to position said piston in said cylinder and means responsive to the temperature of said evaporator for adjusting said last mentioned means to vary the position of said piston in said cylinder and thereby vary the position of said valve. 7

9. A control system for a refrigeration machine having a centrifugal compressor, a condenser connected to receive compressed refrigerant from said compressor, an evaporator for removing heat from a heat exchange fluid, said evaporator being connected to said condenser to receive condensed refrigerant from said condenser, conduit for conducting refrigerant from said evaporator to said compressor, a turbine connected to drive said compressor, valve means for control-ling the flow of motive fluid to said turbine, a lubricating system for said turbine, a pump driven by said turbine for circulating lubricant in said lubricating system, a hydraulic cylinder connected to receive lubricant from said pump, a piston operating in said cylinder and operatively connected to said valve, means responsive to the pressure of lubricant delivered by said pump for positioning said piston and means re sponsive to the temperature of said evaporator for adjusting said last mentioned means to vary the position of said piston and thereby vary the position of said valve.

10. The invention set forth in claim 9 including adjustable means for throttling the flow of refrigerant to said compressor and means responsive to the temperature of said evaporator for adjusting said throttling means to vary the effectiveness of said throttling means.

11. A control system for a refrigeration machine having a centrifugal compressor, a condenser connected to receive compressed refrigerant from said compressor, an evaporator for removing heat from a fluid, said evaporator being connected to said condenser to receive condensed refrigerant from said condenser, conduit for conducting refrigerant from said evaporator to said compressor, adjustable means for throttling the flow of refrigerant to said compressor, a turbine connected to drive said compressor, a valve for controlling the flow of motive fluid to said turbine, a pump driven by said turbine for circulating hydraulic fluid, a hydraulic cylinder connected to receive hydraulic fluid from said pump, a piston operating in said cylinder and operatively connected to said valve, means responsive to the pressure of hydraulic fluid delivered by said pump for controlling the pressure of hydraulic fluid in said cylinder to position said piston in said cylinder, means responsive to the temperature of said evaporator for adjusting said last mentioned means to vary the position of said piston in said References Cited in the file of this patent UNITED STATES PATENTS I 1,268,079 Banner June 4, 1918 2,817,213 Miner Dec. 24, 1957