US3248896A - Controls for centrifugal refrigerant compressors having spin vanes in their inlets - Google Patents

Description

y 1966 R. I PLASTER 3,248,896

CONTROLS FOR CENTRIFUGAL REFRIGERANT COMPRESSORS HAVING SPIN VANES IN THEIR INLETS Filed Oct. 16, 1964 2 Sheets-Sheet 2 METERING v VE 36 CHECK VALVE SUPPLY EISA RETURN F I G 5 -CLOSE I L i 54 TRANSISTOR 1 RELAY x, AMPLIF ER fi I 59 To 58 57 CURRENT X I TRANSFORME 8 TRANSISTOR I To RELAY CR2 4l AMPLIFIER IN VE N TO R ROBERT L. PLASTER United States Patent 3,248,896 CONTROLS FDR CENTRIFUGAL REFRIGERANT COMPRESSORS HAVING SllN VANES IN THEIR INLETS Robert L. Plaster, Staunton, Va., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Get. 16, 1964, Ser. No. 404,338 12 Claims. (Cl. 62201) This invention relates to controls for centrifugal refrigerant compressors having spin inducing vanes in their inlets.

Centrifugal refrigerant compressors such as are disclosed in the copening application of R. W. Wolfe and R. R. Young, Serial No. 280,606, filed May 15, 1963, have spin inducing vanes in their inlets for capacity control. When the load on such a compressor is relatively small, its spin vanes are adjusted by a thermostat to increase the spin in the gas entering the compressor inet, and when the load is relatively large, the spin vanes are adjusted to decrease the spin or to positions in which they induce no spin. Hunting of the spin vanes may occur about the set point of the thermostat, and the most common method of preventing such hunting has been to use feeler rods which contact the vane adjusting mechanisms and respond to over-shoot, and to control feedback circuits using such rods. Such a method requires that feeler rods and wires extend through compressor casings, and does not operate satisfactorily when loads vary over a wide range.

This invention is a control which is simpler, less costly, and operates more satisfactorily than the usual feedback circuit, and which also adjusts the spin vanes to prevent overloading a compressor motor, and to prevent the usual low pressure cut-out from stopping the compressor motor on rapidly falling temperatures as may happen right after start-up. A feature of this invention is that it provides slow adjustment of the spin vanes when they are controlled by a thermostat, and for fast adjustment of the vanes towards closed positions when they are adjusted by a safety control or by a switch which over-rides the usual low pressure cut-out switch.

An object of this invention is to improve the controls of spin vanes of centrifugal refrigerant compressors.

Another object of this invention is to simplify and reduce the cost of controls used to prevent hunting of spin vanes of centrifugal refrigerant compressors.

This invention will now be described with reference to the annexed drawings, of which:

FIG. 1 is a diagrammatic view of a refrigeration system embodying this invention;

FIGS. 2a-2e are diagrammatic views of control relays used in the system;

FIG. 3 is a diagrammatic view of the mechanism for adjustment of the spin vanes of the compressor of the system, a fragmentary sectional view of the compressor being shown;

FIG. 4 is a simplified electrical circuit schematic of the controls of the system; and

FIG. 5 is a simplified electrical circuit schematic of the motor load control of FIG. 4.

Referring now to FIG. 1, a centrifugal refrigerant compressor C, driven by an electric motor CM, has its outlet connected by discharge gas tube to the refrigerant inlet of a condenser 11. The refrigerant outlet of the condenser 11 is connected by tube 12 and expansion valve EV to the refrigerant inlet of a shell-and-tube evaporator 14, the refrigerant outlet of which is connected by suction gas tube 15 to the inlet of the compressor. The tube 15 contains a conventional low pressure control LPC having a normally open switch LPCS.

"ice

The evaporator 14 has a water inlet tube 16 and a Water outlet tube 17, water being chilled within the evaporator and supplied to local air coolers which are not shown. A thermostat bulb 18 is in contact with the tube 17, and has a capillary tube 19 connected to a conventional two-stage thermostat T. The thermostat T is of the type having a low temperature switch LTS and a high temperature switch HTS with an adjustable deadband between the operating points of its two switches. Such a thermostat may be a PENN Series 219 thermostat manufactured by Penn Controls Inc., of Goshen, Indiana, and described in its Bulletin 219T2X.

Referring now to FIGS. 2a-2e, a relay R1 has a normally cosed switch RlS which opens when the relay R1 is energized. A relay R2 has a normally closed switch R2S which opens when the relay R2 is energized. A relay R3 has a normally closed switch RSS1 which opens when the relay R3 is energized, and has a normally open switch RSS2 which closes when the relay R3 is energized. A relay CR1 has a normally closed switch LCS. A relay CR2 has a normally open switch HCS.

Referring now to FIG. 3, the centrifugal compressor C, a fragment of which is shown by FIG. 3, and which is disclosed in detail in the previously mentioned Wolfe- Young application, has an axial inlet passage 20 containing spin vanes 21 which have supporting and adjusting rods 22 journalled for rotation in wall 23 of the compressor. The vanes 21 have off-center pins 24 extending into an annular slot 25 in annular piston 26. The piston 26 has outer portions in slidable contact with surfaces of compressor wall 27, and has inner portions in slidable contact with surfaces of the wall 23. The right end portion of the piston 26 has an enlargement 29 with a cylinder passage portion 30 formed by portions of the walls 23 and 27 to the right of its right end, and with a cylinder passage portion 31 formed within the wall 27 to the left of its left end. A fluid tube 33 connects with the passage portion 30, and a fluid tube 34 connects with the passage portion 31.

A three-way valve VA, adjustable by a solenoid SA, is connected to the tube 34. A three-way valve VB, adjustable by a solenoid SB is connected to the tube 33. A conventional source of fluid under pressure which is not shown, and which may be an oil pump driven by the compressor C or by an electric motor, is connected through tube 36, adjustable metering valve MV and check-valve 38 to the valve VA, and is connected through the tube 36, the valve MV, tube 39 and check-valve 40 to the valve VB. The valves VA and VB are connected to fluid return tube 42. A one-way valve VC, adjustable by a solenoid SC, is connected across the metering valve MV.

When the solenoids SA and SB are energized, they adjust the valves VA and VB respectively, to permit flow in through the tube 34 and out the tube 33, and when deenergized they adjust the valves VA and VB respectively, to permit flow in through the tube 33 and out the tube 34.

Referring now to FIG. 4, the compressor motor CM is connected by conductor 45 to electric supply lines L1 and L2, the usual motor starter switches not being shown. A current transformer winding 46 extends around the conductor 45, and is connected to a conventional motor load control 47, a simplified circuit of which is shown by FIG. 5. The solenoid SA is connected through the switches R381 and R18 to the supply lines, and is normally energized. The solenoid SB is connected through the switches R28 and R381 to the supply lines, and is normally deenergized. The solenoid SC is connected through the switch R382 to the supply lines, and is normally deenergized. The relay R3 is connected through the parallelconnected switches HCS and LPCS to the supply lines, and is normally deenergized. The relay R2 is connected c3) through the series-connected switches LTS and LCS to the supply lines, and is normally deenergized. The relay R1 is connected through the switch HTS to the supply lines, and is normally deenergized.

Referring now to FIG. 5, the current transformer winding 45 of FIG. 4 is connected to parallel-connected primary windings 48 and 49 of transformers 50 and 51 respectively. Secondary winding 52 of the tranfsormer 50 has connected thereacross a rectifier bridge 53, and seriesconnected, oppositely poled Zener diodes 54. The bridge 53 is connected to the input of a conventional transistor amplifier-54, the output of which is connected to the relay CR1. Secondary winding 56 of the transformer 51 has connected thereacross a rectifier bridge 57, and series-connected, oppositely poled diodes 58. The bridge 57 is connected to the input of a conventional transistor amplifier 59, the output of which is connected to the relay CR2. The circuit of FIG. 5 is a simplification of a conventional motor load control such as the Barber-Coleman CC-5191.

OPERATION The compressor C supplies discharge gas through the tube into the condenser 11. Refrigerant liquid from the condenser 11 flows through the tube 12 and expansion valve EV into the evaporator 14, in which the refrigerant liquid is evaporated and chills the water circulated through the evaporator 14. Gas from the evaporator 14 flows through :the tube 15 and low pressure control LPC into the inlet passage of the compressor C, and past the spin vanes 21 into the rotor which is not shown, of the compressor. Since the solenoid SA is normally energized, the valve VA is normally adjusted to pass compressed fluid through the tube 34 into the cylinder passage 31 against the piston 26, tending to push the piston to the right so as to rotate the vanes 21 towards fully open positions. But, since the solenoid SB is deenergized, the valve VB is adjusted to pass compressed fluid through the tube 33 into the cylinder passage 30, preventing movement of the piston so that it is in a hold position.

When the cooling load is such that the thermostat T calls for additional cooling, its switch LTS closes and energizes through the closed switch LCS, the relay R2. The latter closes its switch R2S, energizing the solenoid SB which adjusts the valve VB to permit fluid to flow from the cylinder passage 30 through the tube 33 into the fluid return tube 42. The piston 26 is moved to the right by the compressed fluid supplied through the valve VA and the tube 34 into the cylinder passage 31, and adjusts the spin vanes 21 towards fully open positions for increasing the output of the compressor. When the temperature of the Water flowing through the tube 17 decreases to the operating point of the thermostat switch LTS at the lower end of the dead-band of the thermostat T, the switch LTS opens and deenergizes the solenoid SB which adjusts the valve VB to supply compressed fluid through the tube 33 into the cylinder passage 30, to stop the movement of the piston 26 and of the spin vanes 21.

When the cooling load decreases, the thermostat switch HTS closes at a temperature at the upper end of the deadband of the thermostat T, and energizes the relay R1 which opens its switch R18, deenergizing the solenoid SA. The solenoid SB is also deenergized by the open switch LTS, and the valves VA and VB are adjusted to permit compressed fluid to flow through the tube 33 into the cylinder passage 30, and to permit fluid to flow from the cylinder passage 31 through the tube 34. The piston 26 moves to the left and rotates the vanes 21 towards closed positions, reducing the output of the compressor. When the temperature of the water flowing through the tube 17 increases as a result of the reduced compressor output, to the operating point of the switch HTS, the latter opens and deenergizes the relay R1 which closes its switch RlS which reenergizes the solenoid SA. The latter adjusts the valve VA to permit fluid flow through the tube 34 into the cylinder passage 31, stopping movement of the piston 26 and of the vanes 21.

During the described thermostatic adjustment of the spin vanes 21, the solenoid SC is deenergized, and the valve VC is closed so that the fluid supplied to the piston 26 passes through the metering valve MV which is adjusted to restrict the fluid flow for slowing the opening and closing of the vanes 21 under control of the thermostat T.

When the thermostat switches LTS and HTS are open, the relays R2 and R1 are deenergized; the switch R28 is open and the switch R18 is closed. The open switch R2S deenergizes the solenoid SB, and the closed switch RlS energizes the solenoid SA. The solenoid SA adjusts the valve VA to pass fluid through the tube 34 against the piston 26, and the solenoid SB adjusts the valve VB to admit fluid through the tube 33 against the piston 26-. The piston 26 thus is in a hold position through having fluid under pressure against its opposite fluid responsive surfaces.

When abnormally large current is drawn by the compressor motor CM, the current in the transformer winding 46 increases conformably; the rectifier bridges 53 and 57 supply correspondingly increased D.C. currents to the inputs of the amplifiers 54 and 59 respectively, which energize the relays CR1 and CR2 respectively. The diodes 54 and 58 limit the maximum current. The relay CR1 opens its switch LCS. The relay CR2 closes its switch HCS. The closed switch HCS energizes the relay R3 which opens its switch R381 and closes its switch R352. The closed switch RSS2 energizes the solenoid SC which opens the valve SV, bypassing compressed fluid around the metering valve MV, removing the restriction of the latter, and thus providing for fast closing of the the spin vanes 21 in the operations to be described in the following. The solenoids SA and SB are deenergized by the open switch R351 so that the valves VA and VB are adjusted to permit compressed fluid to move the piston 26 quickly to the left to quickly rotate the spin vanes 21 towards closed positions for quickly reducing the load on the compressor motor CM. The open switch LCS prevents the relay R2 from being energized at this time under control of the thermostat T. When the current drawn by the compressor motor CM returns to normal, the relays CR1 and CR2 are deenergized. The switch HCS opens, and the switch LCS closes. The now open switch HCS deenergizes the relay R3. The closed switch LCS, assuming that the switch LTS is closed, energizes the relay R2, returning the spin vanes towards open position under control of the thermostat T. The switch R3S2 of the relay R3 opens, deenergizing the solenoid SC which adjusts the valve VC to its closed position so that adjustment of the spin vanes by the thermostat T is slow.

If the suction pressure of the compressor C decreases to approach the pressure at which the usual low pressure cut-out which is not shown, would stop the compressor motor, the switch LPCS of the low pressure control LPC closes and energizes the relay R3 to cause the piston 26 to move to the left, and the valve VC to be opened, so as to move the spin vanes 21 quickly towards closed positions as described in the foregoing in connection with the closing of the switch HCS across which the switch LPCS is shunted.

Slow closing and opening of the spin vanes under control of the thermostat T is desirable for decreasing the tendency of the controls to hunt, and quick closing of the spin vanes under control of the motor load control 47, and under control of the low pressure control LPC is desirable for quickly reducing the load on the compressor motor at such times as temporary overloads occur, and for quickly reducing the load on the compressor at such times as suction pressures temporarily drop below normal.

What is claimed is:

1. A refrigeration system comprising a centrifugal refrigerant compressor, a condenser, an evaporator, means connecting said compressor, condenser and evaporator in a refrigeration circuit, said compressor having an axial, suction gas inlet, spin inducing vanes in said inlet, means forming a cylindrical passage, means including a piston slidable in said passage for rotating said vanes towards open or closed positions, said passage having a first portion into which fluid under pressure is supplied to move said piston in one direction to rotate said vanes towards open positions, said passage having a second portion into which fluid under pressure is supplied to move said piston in the opposite direction to rotate said vanes towards closed positions, a compressed fluid supply tube, a fluid return tube, a first three-way valve connected to said tubes and to said first passage portion, a second three-way valve connected to said tubes and to said second passage portion, said first valve in a first position routing fluid from said supply tube into said first passage portion, and in a second position routing fluid from said first passage portion into said return tube, said seco'nd valve in a first position routing fluid from said supply tube into said second passage portion, and in a second position routing fluid from said second passage portion into said return tube, a first solenoid for moving, when energized, said first valve to its said first position, and when deenergized, for moving said first valve to its said second position, a second solenoid for moving, when energized, said second valve to its said second position, and when deenergized, for moving said second valve to its said first position, means for normally energizing said first solenoid, a thermostat responsive to changw in temperature caused by evapora tion of refrigerant in said evaporator, said thermostat having a first, normally open switch which closes when there is a predetermined increase in temperature at said thermostat, and means including said switch when closed for energizing said second solenoid.

2. A refrigeration system as claimed in claim 1 in which said means for energizing said first solenoid includes a normally deenergized relay and includes a normally closed switch of said relay, in which said thermostat has a second normally open switch which closes when there is a further increase in temperature at said thermostat, and in which means including said last mentioned switch when closed is provided for energizing said relay.

3. A refrigeration system as claimed in claim 2 in which said means for energizing said second solenoid includes electric supply connections, includes a second normally deenergized relay and includes a normally open switch when closed of said second relay for connecting said second solenoid to said connections, and in which means including said first switch when closed of said thermostat is provided for connecting said second relay to said connections.

4. A refrigeration system as claimed in claim 3 in which said means for energizing said first and second solenoids includes a third normally deenergized relay and includes a normally closed switch of said third relay, in which said compressor has a driving motor, in which relay means responsive to current drawn by said motor is provided, in which said relay means includes a normally open switch which closes when abnormally large current is drawn by said motor, and in which means including said last mentioned switch is provided for energizing said third relay.

5. A refrigeration system as claimed in claim 4 in which said refrigeration circuit between said evaporator and said compressor includes a low pressure control having a normally open switch which closes when the suction pressure is low, and which is shunted across said switch of said relay means.

6. A refrigeration system as claimed in claim 5 in which said supply tu be includes a metering valve which constricts the flow of fluid to said first and second valves, in which there is provided a normally closed valve shunted across said metering valve, in which there is provided a 6 third solenoid for opening when energized, said normally closed valve, and in which means including a normally open switch of said third relay is provided for energizing said thirdsolenoid when said third relay is energized and said last mentioned switch is closed.

7. A refrigeration system as claimed in claim 1 in which said means for energizing said first and second solenoids includes a normally deenergized relay and includes a normally closed switch of said relay, in which said compressor has an electric driving motor, in which relay means responsive to current drawn by said motor is provided, in which said relay means includes a normally open switch which closes when abnormally large current is drawn by said motor, and in which means including said last mentioned switch is provided for energizing said relay.

8. A refrigeration system as claimed in claim 7 in which said refrigeration circuit between said evaporator and said compressor includes a low pressure control having a normally open switch which closes when the suction pressure is low, and which is shunted across said switch of said relay means.

9. A refrigeration system comprising a centrifugal refrigerant compressor, a condenser, an evaporator, means connecting said compressor, condenser and evaporator in a refrigeration circuit, said compressor having an axial, suction gas inlet, spin inducing vanes in said inlet, means forming a cylindrical passage, means including a piston slidable in said passage for rotating said vanes towards open or closed positions, said passage having a first portion into which fluid under pressure is supplied to move said piston in one direction to rotate said vanes towards open positions, said passage having a second portion into which fluid under pressure is supplied to move said piston in the opposite direction to rotate said vanes towards closed positions, a compressed fluid supply tube, a fluid return tube, a first three-way valve connected to said tubes and to said first passage portion, a second three-way valve connected to said tubes and to said second passage portion, said first valve in said first position routing fluid from said supply tube into said first passage portion, and in a second position routing fluid from said first passage portion into said return tube, said second valve in a first position routing fluid from said supply tube into said second passage portion, and in a second position routing fluid from said second passage portion into said return tube, a first solenoid for moving, when energized, said first valve to said first position, and when deenergized, for moving said first valve to its said second position, a second solenoid for moving, when energized, said second valve to its said second position, and when deenergized, for moving said second valve to its said first position, a thermostat having a deadband, having a first switch at the lower end of said deadband, and having a second switch at the upper end of said deadband, first and second relays, electric supply connections, said first relay having a normally closed switch which opens when said first relay is energized, said second relay having a normally open switch which closes when said second relay is energized, means including said switch of said first relay connecting said first solenoid to said connections, means including said switch, when closed, of said second relay connecting said second solenoid to said connections, means including said first switch of said thermostat for connecting, when closed, said second relay to said connections, and means including said second switch of said thermostat for connecting, when closed, said first relay to said connections.

10. A refrigeration system as claimed in claim 9 in which a third relay having a normally closed switch which opens when said third relay is energized is provided, in which said means connecting said first solenoid to said connections includes said switch of said third relay, in which said means connecting said second solenoid to said connections includes said switch of said third relay, in which said compressor has an electric driving motor, in which relay means responsive to current drawn by said motor is provided, said relay means having a low current switch and a high current switch, in which means including said high current switch, when closed, connects said third relay to said connections, and in which said means connecting said second relay to said connections includes, when closed, said low current switch.

11. A refrigeration system as claimed in claim 10 in which said supply tube includes a metering valve which constricts the How of fluid to said first and second valves, in which there is provided a normally closed valve shunted across said metering valve, in which there is provided a third solenoid for opening, when energized, said normally closed valve, in which said third relay has a sec-- ond normally open switch, and in which means including said last mentioned switch is provided for connecting said third solenoid to said connections when said third relay is energized and said last mentioned switch is 20 closed.

References Cited by the Examiner UNITED STATES PATENTS 2,934,323 4/1960 Burke 6=2-160 X 2,969,959 1/1961 Kuhn et al. 62-160* X 2,983,111 5/1961 Miner et al 6 2 -227 X 3,081,604 3/1963 Namisniak 62217 X ROBERT A. OLEARY, Primary Examiner.

W. E. WAYNER, Assistant Examiner.

Claims (1)

1. A REFRIGERATION SYSTEM COMPRISING A CENTRIFUGAL REFRIGERANT COMPRESSOR, A CONDENSER, AN EVAPORATOR, MEANS CONNECTING SAID COMPRESSOR, CONDENSOR AND EVAPORATOR IN A REFRIGERATION CIRCUIT, SAID COMPRESSOR HAVING AN AXIAL, SUCTION GAS INLET, SPIN INDUCING VANES IN SAID INLET, MEANS FORMING A CYLINDRICAL PASSAGE, MEANS INCLUDING A PISTON SLIDBLE IN SAID PASSAGE FOR ROTATING SAID VANES TOWARDS OPEN OR CLOSED POSITIONS, SAID PASSAGE HAVING A FIRST PORTION INTO WHICH FLUID UNDER PRESSURE IS SUPPLIED TO MOVE SAID PISTON IN ONE DIRECTION TO ROTATE SAID VANES TOWARDS OPEN POSITIONS, SAID PRESSURE IS SUPPLIED TO MOVE SAID PISTON WHICH FLUID UNDER PRESSURE HAVING A SECOND PORTION INTO IN THE OPPOSITE DIRECTION TO ROTATE SAID VANES TOWARDS CLOSED POSITIONS, A COMPRESSED FLUID SUPPLY TUBE, A FLUID RETURN TUBE, A FIRST THREE-WAY VALVE CONNECTED TO SAID TUBES AND TO SAID FIRST PASSAGE PORTION, AND SECOND THREE-WAY VALVE CONNECTED TO SAID TUBES SAID TO SAID SECOND PASSAGE PORTII, SAID VALVE IN A FIRST POSITION ROUTING FLUID PORTION, SAID FIRST VALVE IN A FIRST POSITION ROUTING FLUID IN A SECOND POSITION ROUTING FLUID FROM SAID FIRST PASSAGE

Images