Patent Application
20180209407
The disclosure relates to reciprocating compressors. More particularly, the disclosure relates to discharge valves.
Reciprocating compressors have long been used in applications such as refrigeration. One recent configuration involves pistons whose upper surface has a protrusion that, at top-dead-center, protrudes above the upper face of the cylinder block to help completely fill a volume within a valve plate to provide a more complete expulsion of compressed fluid.
One aspect of the disclosure involves a compressor comprising: a case; and at least one piston mounted for reciprocating movement, each in a respective cylinder of the case, the at least one piston has a peripheral surface and an upper surface. At least one discharge valve comprises: a valve element shiftable between a closed condition and an open condition; a valve guide; one or more springs held at least partially the valve guide biasing the valve element from the open condition toward the closed condition; and one or more vents in the valve guide providing a flow path from a region above the valve element upward through the valve guide.
In one or more embodiments of any of the foregoing embodiments, the one or more springs are a plurality of coil springs.
In one or more embodiments of any of the foregoing embodiments, the one or more springs are eight to sixteen springs per cylinder.
In one or more embodiments of any of the foregoing embodiments, the one or more springs are partially accommodated in one or more pockets and the one or more vents extend to the one or more spring pockets.
In one or more embodiments of any of the foregoing embodiments, the each of the one or more vents is coaxial with a respective associated one of the one or more pockets.
In one or more embodiments of any of the foregoing embodiments, the valve element is an annular element.
In one or more embodiments of any of the foregoing embodiments, one or more peripheral openings provide communication from the cylinder to a discharge plenum.
In one or more embodiments of any of the foregoing embodiments, the compressor further comprises: a motor; a crankshaft driven by the motor; and at least one connecting rod coupling the crankshaft to the at least one piston.
In one or more embodiments of any of the foregoing embodiments, the one or more vents each comprise a drilled hole.
In one or more embodiments of any of the foregoing embodiments, the at least one piston comprises a plurality of identical pistons.
In one or more embodiments of any of the foregoing embodiments: the cylinder is formed in a cylinder block; a valve plate assembly is mounted to the cylinder block; and the valve guide is mounted to the valve plate assembly.
In one or more embodiments of any of the foregoing embodiments: the valve plate assembly has a seat forming a seating surface of a suction valve; the piston upper surface has an outer portion and projection extending centrally upward; and the piston has a top-dead-center condition wherein the projection is partially received within the seat.
In one or more embodiments of any of the foregoing embodiments: the seat forms an outer seating surface of a discharge valve; the valve plate assembly has an inner seat forming an inner seating surface of the discharge valve; the piston has a recess in the projection; and in the top-dead-center condition, the inner seat is partially received within the recess.
In one or more embodiments of any of the foregoing embodiments, a method for manufacturing the compressor comprises drilling to form the at least one vent.
In one or more embodiments of any of the foregoing embodiments, a method for using the compressor comprises reciprocating the piston in the cylinder, during an upward portion of the reciprocating a flow of fluid passing through the at least one vent.
In one or more embodiments of any of the foregoing embodiments, the flow of fluid is a branch of a flow being discharged from the cylinder with another branch passing out a peripheral opening.
In one or more embodiments of any of the foregoing embodiments, a vapor compression system comprises the compressor.
In one or more embodiments of any of the foregoing embodiments, the vapor compression system is a refrigeration system.
The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
Like reference numbers and designations in the various drawings indicate like elements.
Each piston has a lateral or side or outer diameter (OD) surface 50 (
The exemplary valve plate assembly 70 comprises a bottom plate 90 and a top plate 92 separated by spacers. The spacers may include a perimeter plate 94 matching the perimeter of the valve plate assembly so as to enclose a plenum 96. Additional spacers 98 may be distributed within the plenum. As is discussed further below, the plenum 96 is a suction plenum in communication with the suction port 24. For example, with the suction port 24 in a motor case section of the case assembly, the suction plenum 96 may be in communication with the interior of the motor case via a passageway (not shown) cast in the case assembly.
The suction valve comprises a flexible valve element 120 (
The exemplary suction valve element is generally round but has two tabs 135 (
The exemplary seat 132 comprises an upper portion mounted to the upper plate 92 (e.g., via press fit, braze, or the like) and a lower portion depending through the plenum 96 and through an associated aperture 140 in the bottom plate 90. In operation, as the piston withdraws from its top-dead-center condition, reduced pressure/suction causes the valve element 120 to flex, bending in the middle (like a U) and supported by the two tabs 135 at the edge of the cylinder bore and stopped by cooperation of tabs 136 and complementary associated surfaces of recesses in the cylinder. This flexing downward disengages the element from the ID and OD seat surfaces to allow ingestion of refrigerant from the suction plenum 96 into the cylinder via a port 148 (an annular perimeter portion of the aperture 140 radially outboard of the outer diameter (OD) surface of the lower portion of the seat 132). Upon bottoming and reversing of the piston, the valve element 120 flexes back into its closed or sealing condition engaging the seating surfaces to close the port 148.
The discharge valve may similarly comprise a valve element 150 (
As the piston moves upward towards its top-dead-center condition, eventually pressure in the headspace will exceed pressure in the discharge plenum. At this point (or thereafter due to bias of the discharge valve) the discharge valve element 150 will shift from its closed condition toward an open condition allowing refrigerant to pass from the headspace into the discharge plenum. When the piston reaches top-dead-center, the discharge valve will reclose.
With this exemplary configuration of discharge valve, the piston projection 80 includes a central recess 200 (
As the piston approaches top-dead-center, gas in the small space above the lateral portion 54 of the upper surface 52 is driven upward. In a baseline system, this refrigerant is driven upward between the lateral surface 82 of the projection 80 and the adjacent ID surface 134 of the seat 132. The tightness of the space may cause flow resistance, reducing compressor efficiency. Accordingly,
During a late stage of upward movement, the channel lower end 224 will be exposed between the suction valve element above and piston upward surface lateral portion 52 below. Further upward movement of the piston will tend to drive some gas upward through the channel 220 exiting the upper end/outlet 226 and passing therefrom out the discharge valve. Tests on a prototype have shown approximately 1% improvement in efficiency at the rated condition of the baseline compressor. Depending upon implementation, embodiments may be configured to provide a slight increase in capacity (or potentially a slight decrease).
Exemplary dimensions of each hole involve a diameter of 0.5 mm and cross-sectional area of 4.9 mm2. Exemplary aggregate cross-sectional area of the channels (e.g. four times the hole cross-sectional area for the exemplary piston) is 19.6 mm2.
When compared to an otherwise similar baseline compressor lacking the holes/channels 220, the holes caused a TDC clearance volume increase of 5%. This would normally be expected to decrease overall performance Nevertheless there was an observed performance increase due to the increased clearance volume's influence being outweighed by the improved flow, and reduced power. Thus, it is expected that a diminishing return on hole size flow benefit will be overcome by the increased clearance volume and cause decreased performance if the holes are too large. There may also be a lower threshold on hole size where small size does not provide overall benefit due to resistance to flow through the holes.
Alternative individual hole cross-sectional area is at least 2.0 mm2 or 2.0 mm2 to 10.0 mm2. Alternative aggregate cross-sectional area is at least 5.0 mm2 or 5.0 mm2to 50.0 mm2.
An additional modification relative to the baseline compressor is the addition of vents 300 (
One or more of several advantages may be obtained by adding the vent 300. Aspects of discharge valve responsiveness may be improved by allowing the pocket 182 to vent. For example, when the valve element 150 is driven upward from its closed position, vapor above the valve element is either driven into the pocket or squeezed laterally out through a peripheral opening 320. To the extent that vapor is driven into the pocket, this may cause back pressure in the pocket resisting upward movement of the valve element 150. To the extent that vapor is driven laterally outward, this may also involve back pressure but also may cause that vapor to compete with vapor displaced from the cylinder.
One or both of these situations may be addressed by addition of the vent. In some embodiments, the vent may allow vapor initially above the valve element 150 to be vented into the pocket and vapor in the pocket to be vented outward.
Yet an additional potential advantage of some embodiments involves passing of flow from the cylinder through the pocket and vent. For example, the nature of spring bias may be that during some portion or all of the discharging stroke of the piston, the valve element 150 does not top out and close the lower end of the pocket 182. In this situation, a portion of the vapor being discharged from the cylinder may pass radially and axially around the OD perimeter 160 of the valve element 150 and then back inward and upward through the pocket 182 and vent 300. In yet other situations, channels or other passageways may be provided so that flow may pass from the cylinder through the pockets and vents even with the valve element topped out against a stop surface.
Independently of the modifications discussed above regarding the piston channels 220, testing on a prototype showed a capacity increase of approximately 2% at the rating condition and an EER improvement of 1%.
Various further modifications may be made to the channels 220 or vents 300. In one example, the illustrated channels 220 may be replaced with fully open channels along the periphery of the projection or with some form of hybrid of open channel and closed channel such as an open channel along a lower portion of the projection periphery transitioning to a closed channel penetrating into the recess 200. Another variation might involve replacing the array of coil springs 180 and pockets 182 with a single wave spring (e.g., in an annular space such as a downwardly-open channel). The vents could extend upward from that annular space.
The compressor is used in a vapor compression system (e.g., refrigeration system including chillers, air conditioners, heat pumps, and the like). In such a system, the compressor may drive refrigerant flow along the recirculating flowpath passing through one or more heat rejection heat exchangers and one or more heat absorption heat exchangers. The basic configuration involves a sequential flowpath passing through a heat rejection heat exchanger, an expansion device, a heat absorption heat exchanger, and returning to the compressor.
The compressor may be made using otherwise conventional or yet-developed materials and techniques.
The use of “first”, “second”, and the like in the description and following claims is for differentiation within the claim only and does not necessarily indicate relative or absolute importance or temporal order. Similarly, the identification in a claim of one element as “first” (or the like) does not preclude such “first” element from identifying an element that is referred to as “second” (or the like) in another claim or in the description.
One or more embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, when applied to an existing basic system, details of such configuration or its associated use may influence details of particular implementations. Accordingly, other embodiments are within the scope of the following claims.
Benefit is claimed of U.S. Patent Application Ser. No. 62/210,105, filed Aug. 26, 2015, and entitled “Reciprocating Compressor Vented Discharge Valve”, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2016/048518 | 8/25/2016 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62210105 | Aug 2015 | US |
