Abstract
A reciprocating compressor having: a suction valve; a discharge valve; and a working chamber; wherein the suction valve is configured to provide fluid communication between a suction channel and the working chamber and the discharge valve is configured to provide fluid communication between the working chamber and a discharge channel; wherein the suction valve has at least one non-self-actuated valve and the discharge valve has at least one self-actuated check valve.
Claims
1-29. (canceled)
30. A reciprocating compressor comprising: a suction valve; a discharge valve; and a working chamber; wherein the suction valve is configured to provide fluid communication between a suction channel and the working chamber and the discharge valve is configured to provide fluid communication between the working chamber and a discharge channel; wherein the suction valve comprises at least one non-self-actuated valve and the discharge valve comprises at least one self-actuated check valve.
31. The reciprocating compressor according to claim 30, wherein the self-actuated check valve comprises one or more of: a reed valve; a plate-valve; self-actuated poppet valve; self-actuated ball check valve.
32. The reciprocating compressor according to claim 30, wherein the non-self-actuated valve is one or more of: a poppet valve; a rotary valve; a piston valve; a slide valve; a spool valve.
33. The reciprocating compressor according to claim 30, wherein the non-self-actuated valve is one or more of: mechanically controlled; pneumatically controlled; electrically controlled; hydraulically controlled.
34. The reciprocating compressor according to claim 30, further comprising: a compressor block having at least one cylinder with a piston arranged to reciprocate therein; and at least one cylinder head; wherein the suction valve is arranged in the cylinder head.
35. The reciprocating compressor according to claim 30, wherein the at least one discharge valve is a plurality of self-actuated check valves.
36. The reciprocating compressor according to claim 30, wherein the discharge valve is arranged concentrically with the suction valve.
37. The reciprocating compressor according to claim 35, wherein the plurality of self-actuated check valves are each concentric with the suction valve.
38. The reciprocating compressor according to claim 34, wherein the suction valve and/or discharge valve are arranged such that their central axis is shared with the central axis of the at least one cylinder.
39. The reciprocating compressor according to claim 34, wherein the piston is provided with at least one protrusion and the cylinder head is provided with at least one cylinder head recess, wherein the at least one protrusion and the at least one cylinder head recess are registered such that the protrusion will displace at least a portion of the volume of the cylinder head recess in use.
40. The reciprocating compressor according to claim 34, wherein the piston is provided with at least one piston recess which is shaped and configured to receive a non-self-actuated valve in use.
41. The reciprocating compressor according to claim 34, wherein the suction channel comprises: a first portion formed in the compressor block; and a second portion formed in the at least one cylinder head; wherein the first and second portions are configured to mate at a connection to form a fluid passage between the first portion and the second portion for delivering working fluid to the working chamber in use.
42. The reciprocating compressor according to claim 41, wherein the first portion of the suction channel comprises a fluid entry path adjacent the connection when the first and second portions are mated in use, wherein the fluid entry path is configured to direct fluid at an angle of between 20 degrees and 80 degrees relative to a normal on a cylinder center axis.
43. The reciprocating compressor according to claim 42, wherein the angle is around 45 degrees.
44. The reciprocating compressor according to claim 41, wherein the first portion comprises a buffer reservoir.
45. The reciprocating compressor according to claim 30, wherein: the working chamber is a first working chamber and the suction channel is a first suction channel; the compressor further comprises a second working chamber and a second suction channel; the first and second suction channels join to form a combined suction channel comprising an inlet for the compressor receiving working fluid therethrough.
46. A heat pump comprising the reciprocating compressor according to claim 30.
47. The heat pump according to claim 46, wherein the heat pump is a high-temperature heat pump capable in use of supplying output temperatures above 55 degrees Celsius or above 80 degrees Celsius or above 90 degrees Celsius or above 100 degrees Celsius or above 110 degrees Celsius or above 120 degrees Celsius or above 130 degrees Celsius or above 140 degrees Celsius or above 150 degrees Celsius or above 160 degrees Celsius or above 170 degrees Celsius or above 180 degrees Celsius or above 190 degrees Celsius or above 200 degrees Celsius or above 210 degrees Celsius or above 220 degrees Celsius or above 230 degrees Celsius or above 240 degrees Celsius or above 250 degrees Celsius.
48. Use of a reciprocating compressor according to claim 30 in a heat pump.
49. A method of operating a reciprocating compressor according to claim 30, comprising the steps of: a. sucking working fluid into the working chamber via the at least one non-self-actuated valve; and b. discharging working fluid from the working chamber via the at least one self-actuated check valve.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0071] The prior art and embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
[0072] FIG. 1 shows a standard prior art compressor;
[0073] FIG. 2 shows an improved compressor;
[0074] FIG. 3 shows the improved compressor of FIG. 2 with an improved alternative suction channel;
[0075] FIG. 4 shows the improved compressor of FIG. 2 with an alternative suction channel;
[0076] FIG. 5 shows a detailed section view of a piston compressor;
[0077] FIG. 6 shows a detailed section view of the piston compressor of FIG. 5;
[0078] FIG. 7 shows a detailed bottom view of the cylinder head of FIG. 6;
[0079] FIG. 8 shows a limited section view of a discharge valve of the piston compressor shown in FIG. 5;
[0080] FIG. 9 shows an optional lubricant return system for the compressor shown in FIG. 5.
[0081] FIGS. 10a and 10b show a first example of a self-actuated valve;
[0082] FIGS. 11a and 11b show a second example of a self-actuated valve; and
[0083] FIGS. 12a and 12b show a third example of a self-actuated valve.
DETAILED DESCRIPTION
[0084] FIG. 1 shows a prior art compressor 1 in the form of a piston compressor which utilises a condensable working fluid. The compressor 1 comprises a compressor block 20 having a cylinder 250 with a reciprocating piston 240 arranged inside the cylinder 250, and a cylinder head 10 having a suction channel 40 and a discharge channel 50. The cylinder 250, cylinder head 10 and piston 240 define a working chamber 251 for compression of the compressible working fluid therein. Selection of suitable compressible working fluids is well known in the art.
[0085] Working fluid inflow is controlled and admitted from the suction channel 40 into the working chamber 251 through a suction valve 110, and working fluid outflow is controlled and admitted out of the working chamber 251 to the discharge channel 50 through two discharge valves 120. As can clearly be seen in FIG. 1, the suction channel 40 is arranged to suck working fluid into the working chamber 251. The suction channel 40 is of a substantially vertical and substantially straight configuration. It will be understood by a person skilled in the art that the suction channel 40 connects to other piping and/or manifolds where the working fluid is provided through. Although in the presently described example one suction valve 110 and two discharge valves 120 are provided, any number of suction valves 110 and discharge valves 120 working in parallel may be found in other prior art examples.
[0086] The valves 110, 120 shown in FIG. 1 are of the reed-type, having at least a reed valve blade 121 and a reed valve retainer plate 122, also called a stop plate. The reed blade 121 controls the opening and thus the fluid communication through a valve opening 143, also called a valve port or a valve slot, in the cylinder head 10. Reed valves function in the way that they are operated by a differential pressure exerted across them, and as such they are passively controlled, which means that they do not need any actuator elements to open or close. Opening or closing is performed solely as a function of the differential pressure across the reed blades 121 and in this way such valves can have a simple construction, however, as described above, they also come with drawbacks. In other words, the valve is closed by the reed blade 121 being pushed against the valve slot 143, and thus closing the slot, due to the pressure differential across the reed blade 121 in this direction. Therefore, reed valves also function as check valves, since they only open in one direction.
[0087] FIG. 2 shows an example of an improved compressor 1. Similarly to the prior art compressor 1 described with reference to FIG. 1, the compressor 1 is a piston compressor which utilises a condensable working fluid. The compressor 1 comprises a compressor block 20 having a cylinder 250 with a reciprocating piston 240 arranged inside the cylinder 250, and a cylinder head 10 having a suction channel 40 and a discharge channel 50. The cylinder 250, cylinder head 10 and piston 240 define a working chamber 251 for compression of the working fluid therein.
[0088] Working fluid inflow is controlled and admitted from the suction channel 40 into the working chamber 251 through a suction valve 110, and working fluid outflow is controlled and admitted out of the working chamber 251 to the discharge channel 50 through discharge valves 120. As can clearly be seen in FIG. 2, the suction channel 40 is arranged to suck working fluid into the working chamber 251 with the suction channel 40 in a substantially vertical and substantially straight configuration. It will be understood by a person skilled in the art that the suction channel 40 connects to other piping where the working fluid is provided through. Although in the presently described example one suction valve 110 and two discharge valves 120 are provided for one cylinder 250, any number of suction and discharge valves working in parallel may be found in other examples where multiple cylinders 250 are provided. Similarly, although shown as one suction valve 110 and two discharge valves 120 in the presently described example, in other examples there may be any number of suction valves 110 and/or any number of discharge valves 120 for each cylinder 250.
[0089] The suction valve 110 of the example shown in FIG. 2 is a poppet valve, while the discharge valves 120 are reed valves as in the prior art compressor 1 shown in FIG. 1. Due to the geometry of the poppet suction valve 110, a larger effective opening area can be achieved than with a reed valve, considering the same overall dimension of the compressor 1, such as cylinder bore. In addition, the poppet suction valve 110 can be actively controlled by means of mechanical actuators as is shown in greater detail later with reference to later Figures.
[0090] Still referring to FIG. 2, it can be seen that in the presently described example, the suction valve 110 is arranged centrally relative to the working chamber 251 and cylinder 250, i.e. the suction valve 110 is on the central axis 252 of the cylinder 250. Additionally, it can be seen that the discharge valves 120 are arranged circumferentially around the suction valve 110. That is to say, the discharge valves 120 encircle the suction valve 110 and the suction valve 110 and discharge valves 120 share a central axis with the central axis 252 of the cylinder 250, and together the suction valve 110 and discharge valves 120 consume substantially the entire area of the top of the working chamber 251. The suction valve 110 and the discharge valves 120 are arranged concentrically as shown in FIG. 2. In some alternative examples, the suction valve 110 and discharge valves 120 may be arranged concentrically, but not sharing a central axis 252 with the cylinder 240.
[0091] Referring now to FIG. 3, an alternative compressor 1 is shown with a suction channel 40 configured to provide a suction fluid flow path 41 therethrough in use. The suction fluid flow path 41 is significantly different from a fluid flow path (not shown) for the compressor 1. The suction fluid flow path 41 is formed by connection of the compressor block 20 and the cylinder head 10 at a connection 42. The suction channel 40 is partly in the cylinder head 10 and partly in the compressor block 20. The suction channel 40 comprises a common manifold 43 in the compressor block 20 where working fluid first enters the suction channel 40 from auxiliary piping, a buffer reservoir 44 and a fluid inlet channel 45 connecting the buffer reservoir 44 to the working chamber 251. Still referring to the cross-sectional view shown in FIG. 3, the compressor 1 has a front facing towards the viewer in FIG. 3, a rear facing away from the viewer and a top where the suction channel 40 and discharge channel 50 connect to additional piping.
[0092] As working fluid enters the common manifold 43 of the suction channel 40 at the rear of the compressor 1, the working fluid travels towards the front of the compressor 1 in the direction of the viewer in FIG. 3 and travels downwards to the buffer reservoir 44. From the buffer reservoir 44 the working fluid is sent upwards towards the top of the compressor 1 through the connection 42 and via the fluid inlet channel 45 to the working chamber 251. In the presently described example, the working fluid travels across the compressor 1 and then travels upwards towards the top of the compressor 1 through the angle 46 in the buffer reservoir 44. In the presently described example, the angle 46 is 90 degrees, that is to say the fluid travels across the compressor 1 perpendicular to the central axis 252 of the cylinder along a horizontal axis 47 and then travels parallel to the central axis 252 of the cylinder along a vertical axis 48 and then turns into the working chamber 251 via the suction valve 110 as can be seen in FIG. 3.
[0093] In other exemplary compressors (not shown) comprising multiple cylinders 250, there may be provided a single common manifold 43 for receiving working fluid from the auxiliary piping. In this connection, each cylinder 250 may be arranged to receive working fluid from the common manifold 43 through a splitting of the working fluid between the common manifold 43 and each of the buffer reservoirs 44. This not only reduces the number of external connections that otherwise need to be made (e.g. one for each cylinder head's 10 suction channel 40), but also greatly reduces the number of seals/gaskets needed, since the connection 42 is sealed using the same seal as would be required anyway for the interface between the cylinder head 10 and the compressor block 20, as will be explained in more detail later.
[0094] Still referring to FIG. 3, it can be seen that in the presently described example, the suction valve 110 is arranged centrally relative to the working chamber 251 and cylinder 250, i.e. the suction valve 110 is on the central axis 252 of the cylinder 250. Additionally, it can be seen that the discharge valves 120 are arranged circumferentially around the suction valve 110. That is to say, the discharge valves 120 encircle the suction valve 110 and share a central axis with the central axis 252 of the cylinder 250, and together the suction valve 110 and discharge valves 120 consume substantially the entire area of the top of the working chamber 251.
[0095] Referring now to FIG. 4, another alternative compressor 1 is shown with a suction channel 40 configured to provide a suction fluid flow path 41 therethrough in use. Similarly to the compressor 1 of FIG. 3, the suction fluid flow path 41 is formed by connection of the compressor block 20 and the cylinder head 10 at a connection 42. The suction channel 40 is partly in the cylinder head 10 and partly in the compressor block 20. The suction channel 40 comprises a common manifold 43 in the compressor block 20 where working fluid first enters the suction channel 40 from auxiliary piping, a buffer reservoir 44 and a fluid inlet channel 45 connecting the buffer reservoir 44 to the working chamber 251. Still referring to the cross-sectional view shown in FIG. 4, the compressor 1 has a front facing towards the viewer in FIG. 4, a rear facing away from the viewer and a top where the suction channel 40 and discharge channel 50 connect to additional piping.
[0096] As working fluid enters the common manifold 43 of the suction channel 40 at the rear of the compressor 1, the working fluid travels towards the front of the compressor 1 in the direction of the viewer in FIG. 4 and travels downwards to the buffer reservoir 44. From the buffer reservoir 44 the working fluid is sent upwards towards the top of the compressor 1 through the connection 42 and via the fluid inlet channel 45 to the working chamber 251. In the presently described example, the working fluid travels across the compressor 1 and then travels upwards towards the top of the compressor 1 through the angle 46 in the buffer reservoir 44. In the presently described example, the angle 46 is 45 degrees, that is to say the fluid travels across the compressor 1 perpendicular the central axis 252 of the cylinder 240 along a horizontal axis 47 and then travels obliquely to the central axis 252 of the cylinder 240 as shown in FIG. 4. In other examples, another acute angle may be provided for the angle 46. For example, the angle 46 may be 30 degrees, or 40 degrees, or between 40 degrees and 50 degrees, or 60 degrees.
[0097] Reducing the angle 46 which the working fluid must turn at in the buffer reservoir 44 results in the fluid flow path 41 taking a smoother path through the compressor 1, which may result in a reduced pressure drop as the working fluid moves from the common manifold 43 to the fluid inlet channel 45, thereby resulting in increased performance of the compressor 1.
[0098] The cylinder head 10 may in some examples comprise a valve plate (not shown in FIG. 4) configured to provide seating and sealing of the suction valve 110 and discharge valves 120 in the top of the working chamber 251.
[0099] FIG. 5 shows a detailed section view of an alternative compressor 1, FIG. 6 shows show a detailed section view of the valve system of the compressor 1, FIG. 7 shows a detailed bottom view of the cylinder head of the compressor 1 and FIG. 8 shows a detailed view of the discharge valve of the compressor 1.
[0100] Referring firstly to FIG. 5, the compressor 1 comprises first and second cylinder heads 10A, 10B, a compressor block 20, a lubricant reservoir 30, a crankshaft 210 with counterweights 220 to reduce vibration and first and second connecting rods 211A, 211B connected between the crankshaft 210 and first and second pistons 240A, 240B arranged in first and second cylinders 250A, 250B to define first and second working chambers 251A, 251B. The compressor 1 further comprises first and second suction channels 40A, 40B configured to provide working fluid to the working chambers 251A, 251B in use. The compressor 1 is designed using a so-called V-configuration, having the first and second cylinders 250A, 250B angularly separated by about 90. Preferably, V-configuration compressors such as in the presently described example may comprise an even number of cylinders 250A, 250B, however it may be envisaged that the compressor 1 may be configured with an odd number of cylinders 250A, 250B in some examples.
[0101] A working fluid has typically undergone pre-heating, evaporation and superheating in one or more heat exchangers (not shown) before entering the compressor 1 typically through a pipe, a manifold, or a network of pipes (not shown). The working fluid enters the compressor 1 through a single common manifold 43, thereby providing only one entry point for the working fluid into the compressor 1. In the presently described example, as in previous examples, the common manifold 43 is arranged at the rear of the compressor 1. It will be understood that the front and rear of the compressor 1 may be reversed in other examples, and indeed that the common manifold 43 may be located centrally on the compressor in some examples rather than being at the front or the rear.
[0102] Still referring to FIG. 5, after the working fluid has entered the common manifold 43, the working fluid splits and travels towards the front of the compressor 1 from the common manifold 43 in two separate flows (not shown) of working fluid travelling in the direction of the viewer in FIG. 5 and each flow travelling downwards with the first working fluid flow travelling to the first buffer reservoir 44A and the second working fluid flow travelling to the second buffer reservoir 44B. In the interest of brevity, the following explanation is in regard to the first fluid flow only. However, it will be understood that the same description applies to the second fluid flow, mutatis mutandis.
[0103] The first fluid flow travels from the first buffer reservoir 44A upwards towards the top of the compressor 1 through a first connection 42A and via a first fluid inlet channel 45A to a first working chamber 251A. In summary, in the presently described example, the working fluid travels across the compressor 1 and then travels upwards towards the top of the compressor 1 via the first buffer reservoir 44A.
[0104] When the first piston 240A expands the volume of the working chamber 251A while moving away from the cylinder head 10A, suction causes working fluid to enter the first working chamber 251A through a first suction valve 110A, which in the presently described example is a poppet valve.
[0105] By the rotary motion of the crankshaft 210, a translatory motion of the first piston 240A inside the first cylinder 250A is provided, cyclically bringing the pistons 240A down to bottom dead center (BDC) position, at which the suction process stops. The compressor 1 then starts to compress the working fluid in the first working chamber 251A until the working fluid has reached a pressure exceeding that of the pressure in a discharge channel 50A, and then the discharge process begins, as the first discharge valves 120A, which in the presently described example are reed valves, then open because of the differential pressure across their reed blades, as previously explained.
[0106] As previously discussed, the same steps are performed for the second piston 240B in the second cylinder 250B. The first discharge channel 50A may continue into a manifold, pipe or similar where a fluid connection may be made to the second discharge channel 50B such that the working fluid flows can be combined and the combined fluid flow may then be lead further to one or more heat exchangers (not shown), in which the working fluid is typically desuperheated, condensed and optionally subcooled. In other examples, one or more of these processes may be applied, or other processes may be applied to the discharged working fluid.
[0107] The first and second inlet valves 110A, 110B are actuated by conventional valve actuator mechanisms, the design and/selection of which will be well within the capabilities of a person skilled in the art.
[0108] The first suction channel 40A is partly in the first cylinder head 10A and partly in the compressor block 20 with connection of the two parts of the first suction channel 40A being provided by the first connection 42A.
[0109] In the presently described example, the working fluid in the first fluid flow stream travels across the compressor 1 and then travels upwards towards the top of the compressor 1.
[0110] Although the working fluid path is only described above with reference to the first buffer reservoir 44A, it will be appreciated that the second buffer reservoir 44B is also configured in a similar fashion to as described for the first buffer reservoir 44A. It will also be appreciated that in examples with further cylinders, such as sixteen cylinders, some or all of the buffer reservoirs may be as described above for the first buffer reservoir 44A.
[0111] Still referring to FIG. 5, the first buffer reservoir 44A provides a larger volume relative to the common manifold 43 and piping leading to the first buffer reservoir 44A. As can be seen in FIG. 5, the first buffer reservoir 44A is located directly adjacent the first working chamber 251A with only the required fluid inlet channel 45A connecting the first buffer reservoir 44A and the first working chamber 251A. This allows the first buffer reservoir 44A to maintain a sufficient volume of working fluid such that when working fluid is sucked into the first working chamber 251A there is not a significant pressure drop, as may be the case if the relatively narrow piping between the common manifold 43 and the first buffer reservoir 44A were to extend directly to the working chamber 251A without entering a region of larger volume. In this connection, the first buffer reservoir 44A is of a sufficiently large volume relative to the first working chamber 251A such that when a volume of working fluid equal to the volume of the first working chamber 251A when the first piston is at bottom dead centre position, i.e. the full volume of the first working chamber 251A, is extracted from the first buffer reservoir 44A, there is not substantial pressure drop in the fluid in the first buffer reservoir 44A. In this connection, sufficiently pressurised fluid is always available to the first working chamber 251A. Additionally, the first buffer reservoir 44A can be continually fed working fluid from the common manifold 43 to continually top up the first buffer reservoir 44A, rather than the first working chamber 251A sucking fluid from the entire suction channel 40A which would result in a pressure drop. The reduction or elimination of a substantial pressure drop improves the performance of the compressor 1.
[0112] Still referring to FIG. 5, when the compressor 1 is assembled and ready to operate in a heat pump system for example, there are a plurality of interior volumes 60 in the compressor 1 which will typically be pressurised due to the properties of the working fluid being used. Therefore the compressor 1 needs to be hermetically closed against the atmosphere. In order to still have practical access to important internal volumes 60 of the compressor 1, the compressor 1 comprises pressure-reinforced covers 101A, 101B, 201A, 201B, that enable practical access during assembly, service or for other relevant reasons, while still being strong enough to withstand the internal pressures in the compressor's 1 interior volumes 60 when pressurized.
[0113] The lubricant reservoir 30 is equipped with a plurality of lubricant heaters 301, that are embedded in a main block 300 of the lubricant reservoir 30. These heaters 301 can be activated upon relevant need through a standard control system (not shown).
[0114] FIG. 6 shows a detailed view of the suction and discharge of the first working chamber 251A and the associated components previously described.
[0115] FIG. 7 shows a detailed section view at the first cylinder head 10A of the compressor 1 where the first cylinder head 10A meets the compressor block 20. The first suction valve 110A can be seen encircled by the first discharge valve 120A. The first discharge valve 120A comprises a first valve plate 140A, in which there are a plurality of first discharge valve slots 142A and corresponding first discharge valve bridges 143A between the slots 142A. In the presently described example the plurality of first discharge valve slots 142A are arranged in concentric circles, however it will be understood that other arrangements are possible.
[0116] The first discharge valve slots 142A provide fluid communication between the first working chamber 251A (shown in FIGS. 5 and 6) and the first discharge channel 50A. In some examples (not shown), the first valve plate 140A may be omitted, and its function replaced by the cylinder head main block (not shown) instead, as will be appreciated by a person skilled in the art.
[0117] In the cross-sectional view in FIG. 7 the first connection 42A and first discharge channel 50A are also visible.
[0118] FIG. 8 shows a detailed view of the first discharge valve 120A. The first discharge valve 120A comprises first reed valve blades 121A which are pressed against the first valve slots 142A of the first valve plate 140A so that the first discharge valve 120A is closed. Separate first reed valve springs 123A provide a closing force to the first reed valve blades 121A, as the first reed valve springs 123A are pressed against a first valve retainer plate 122A on the opposite side of the first reed valve blades 121A. In other examples, the spring force provided by the first reed valve springs 123A may be provided by forming the first reed valve blades 121A out of a spring material and arranging the first reed valve blades 121A so that they close the discharge valve 120A automatically through their own inherent spring force (such an arrangement is shown in FIGS. 1 to 4). However, in the preferred example shown in FIGS. 5 to 8, due to the use of separate first reed valve springs 123A, the first reed valve blades 121A can be made from a non-spring material.
[0119] In the present invention, a first recess 141A is provided in the first valve plate 140A as can be seen in FIG. 8. The first recess 141A covers the region comprising the first reed valve slots 142A, to decrease the dead volume contribution by the first reed valve slots 142A. The first recess 141A is formed by machining away this region in which there is no need for the full thickness of the first valve plate 140A, and so material can be machined away without compromising on the required rigidity.
[0120] Volumetric efficiency is an important performance factor of any compressor, and this is closely linked to the compressor cylinders' dead volume: The dead volume is the combination of non-displaceable (by the piston) volumes primarily caused by two factors. Firstly, the clearance volume needed to ensure that the piston does not collide with the cylinder head, valve plate or valves due to production tolerances, valve motion, varying gasket thicknesses etc., and secondly passive volumes that are required as part of ports, slots or other, due to the need to provide a certain material thickness to house these.
[0121] Referring again to FIG. 6, the first piston 240A comprises a first piston crown 241A comprising a first crown recess 242A and a first crown protrusion 243A. The first crown recess 242A is provided such that the suction valve 110A will enter and displace a major part of the volume of the first crown recess 242A when the first piston 240A is close to top dead center (TDC) during operation. The first crown protrusion 243A is seen on either side of the first crown recess 242A, although it will be easily understood that the first crown protrusion 243A is circular on the first piston 240A. The first crown protrusion 243A is registered with the first recess 141A such that the first crown protrusion 243A will enter and displace a major part of the volume of the first recess 141A when the first piston 240A is close to top dead center (TDC) during operation. The provision of a first crown protrusion 243A and a first crown recess 242A reduces the dead volume and thereby increase the volumetric efficiency.
[0122] Referring now to FIG. 9, the compressor 1 is again shown but now with an optional lubricant return system 400 comprising an inlet 401 fluidly connected to a lower surface of the first buffer reservoir 44A. The inlet 401 communicates lubricant to a tank 402 where the lubricant is temporarily stored in use. The tank 402 comprises a valve 403 which is selectively openable to transfer the lubricant from the tank 402 to the lubricant reservoir 30. The valve 403 may be configured with a timer such that the valve 403 opens every 20 seconds, 30 seconds, 40 seconds for example, to transfer lubricant back into the lubricant reservoir 30. Alternatively, or in addition to the timer, the valve 403 may be configured to be selectively opened by the user of the system or to open automatically when a certain volume of lubricant has gathered in the tank 402. Although only shown in FIG. 9 in connection with the first buffer reservoir 44A, it will be understood that one, all or only some of the buffer reservoirs may be provided with a lubricant return system 400. For example, if sixteen cylinders are used, there may be provided sixteen lubricant return systems 400. In some examples where there are multiple buffer reservoirs, the lubricant from each buffer reservoir may be channelled and gathered in one tank, before being channelled back to the lubricant reservoir 30. In some examples, a valve (not shown) may be provided at the inlet 401 to selectively control the delivery of lubricant to the tank 402. In other examples, the tank 402 may be omitted.
[0123] In any of the above-described examples, the suction channels 40, 40, 40, 40A, 40B, and/or discharge channels 50, 50, 50, 50A, 50B, may be formed during casting of the cylinder head 10, 10, 10, 10A, 10B and compressor block 20, 20, 20, 20, respectively.
[0124] The presently described compressors allow a lower pressure drop to be maintained across the suction valve during operation, thereby maintaining a higher efficiency of the compressor when utilizing more demanding working fluids, and especially those with a higher density.
[0125] The present disclosure describes poppet and reed valves. It will be understood that the reed valves may be replaced by any self-actuated check valve or valves and the poppet valve may be replaced by any non-self-actuated valve or valves. As non-limiting examples only, known arrangements of self-actuated check valves are now described briefly with reference to FIGS. 10a to 12b. Firstly referring to FIGS. 10a and 10b there is shown a first self-actuated check valve 500 which is configured to move from a closed position shown in FIG. 10a to an open position shown in FIG. 10b. The self-actuated check valve 500 comprises a valve plate 510 and first and second reed elements 521, 522 which are biased to respectively close first and second apertures 531, 532 in the valve plate 510 in the absence of sufficient pressure in the direction of arrows A. The self-actuated check valve 500 further comprises first and second curved stop plates 541, 542 configured to arrest the movement of the first and second reed elements 521, 522 when the reed elements 521, 522 are moved to the open position.
[0126] As another non-limiting example, another self-actuated check valve 600 in the form of a plate valve is provided which is configured to move from a closed position shown in FIG. 11a to an open position shown in FIG. 11b. The self-actuated check valve 600 comprises a valve plate 610 and first, second and third biased closure elements 621, 622, 623 which are biased to respectively close first, second and third apertures 631, 632, 633 in the valve plate 610 in the absence of sufficient pressure in the direction of arrow A. The self-actuated check valve 600 further comprises first, second and third stop plates 641, 642, 643 configured to arrest the movement of the first, second and third biased closure elements 621, 622, 623 when the biased closure elements 621, 622, 623 are moved to the open position shown in FIG. 11b. The actual biassing means used is not shown, however it will be understood that the biassing may be implement in a myriad of ways.
[0127] As another non-limiting example, another self-actuated check valve 700 is provided which is configured to move from a closed position shown in FIG. 12a to an open position shown in FIG. 12b. The self-actuated check valve 700 comprises a valve plate 710 and first, second and third spring biased poppet elements 721, 722, 723 which are biased to respectively close first, second and third apertures 731, 732, 733 in the valve plate 710 in the absence of sufficient pressure in the direction of arrow A.
[0128] As previously mentioned, throughout the present disclosure, reference is made to reed valves and poppet valves. However, it will be appreciated that configurations using a reed valve or valves may be replaced by any self-actuated check valve or valves and configurations using a poppet valve or valves may be replaced by any non-self-actuated valve or valves. The self-actuated valves may be any of the non-limiting examples shown in FIGS. 10 to 12, or may be any other self-actuated valve.
[0129] It will also be appreciated that self-actuated is intended to carry the standard meaning within the art. That is that self-actuated valves are passively opened and closed, i.e. they open and close in response to fluid pressure in the system rather than being driven by an external electrical or mechanical source provided for the purpose of opening or closing the valve. Similarly, non-self actuated is also intended to carry the standard meaning within the art, i.e. that the valve is actively driven, rather than opening and closing in response to fluid pressure in the system.
[0130] It will be understood that at the time of writing, the term high-temperature heat pump generally refers to the heat pumps capable of supplying output temperatures above 55 degrees Celsius. It will be appreciated by a person skilled in the art that the definition of high-temperature in this context may change over time, and it is foreseeable with advancements in technology that in the future high-temperature may be used to refer to heat pumps with an output temperature of above 80 degrees Celsius for example, or even higher.
[0131] In the above description there are several features of the described examples that are well-known to a person skilled in the art, and which have either been omitted or at least not described in detail for the sake of brevity. Further, although a preferred example comprises a heat pump compressor, and more specifically a heat pump compressor that utilises a condensable gas, the invention is not limited to this, and may be just as relevant for any other application requiring a compressor, for example an air compressor, natural gas compressor, CO2 compressor etc.
[0132] It will be understood that a plurality of non-self-actuated valves may together form a suction valve, i.e. there need not be one single non-self-actuated valve element forming the entire suction valve. Likewise, a plurality of self-actuated check valves may together form a discharge valve, i.e. there need not be one single self-actuated check valve element forming the entire discharge valve.
[0133] For example, as shown in the example described with reference to FIG. 2, there is provide two self-actuated check valve discharge elements forming the discharge valve. It will be understood that there may likewise be two, three, four or more non-self-actuated suction valve elements forming the suction valve in some examples (not shown).
