Patent Description:
Multi-stage compressors can use single-row or multiple-row, fixed or rotatable return vanes to direct and/or control interstage flow, when operated at full and partial load conditions. These return vans can, at partial load conditions lead to low-momentum zones in return channel passages or adverse pressure gradients that alter the intended side stream injection flow rate, which can lead to compressor instability, reduced system efficiency, and result in narrower operating ranges. <CIT> is directed to a centrifugal compressor having first and second impellers, with a port allowing introduction of fluid from an economizer and/or from a recirculation flow path into the compressor, between the first and second impellers.

This disclosure is directed to an interstage capacity control valve for a centrifugal compressor, particularly one providing side stream flow regulation or distribution.

The interstage capacity control valve can simultaneously control flow between stages of a multi-stage compressor while regulating the addition of a side stream flow to that flow between stages. The interstage capacity control valve increases the velocity of the interstage flow where the side stream is added, avoiding stagnant areas of flow. This in turn can improve the stability and efficiency of the compressor at both partial and full load conditions.

The axial extension of the interstage capacity control valve further can reduce maintenance issues relating to the complexity of rotatable vane designs for capacity control in centrifugal compressors.

Further, embodiments can add the side stream flow at a comparatively low-pressure area in the interstage line, facilitating addition of the side stream and allowing more of the side stream to be successfully introduced. This can avoid cycling and compression of bypass gases.

In an embodiment, a centrifugal compressor includes a first stage impeller and a second stage impeller. The centrifugal compressor includes a side stream injection port located between the first stage impeller and the second stage impeller, the side stream injection port configured to receive a side stream of a fluid. The centrifugal compressor includes a capacity control valve. The capacity control valve is configured to extend and retract through the side stream injection port. The capacity control valve has a curved surface facing a direction of flow from the first stage impeller to the second stage impeller. The capacity control valve is configured to be extended through the side stream injection port between an open position where the side stream of the fluid can flow through the side stream injection port and a closed position where the capacity control valve obstructs flow of the side stream of the fluid through the side stream injection port.

In an embodiment, the capacity control valve has a ring shape.

In an embodiment, the centrifugal compressor includes a plurality of the side stream injection ports and a plurality of the capacity control valves.

In an embodiment, when in the open position, a tip of the capacity control valve at an end of the curved surface is within the side stream injection port.

In an embodiment, the capacity control valve extends and retracts in a direction substantially perpendicular to the direction of flow from the first stage impeller to the second stage impeller.

In an embodiment, the centrifugal compressor further includes one or more deswirl vanes between the first stage impeller and the second stage impeller. In an embodiment, the capacity control valve includes one or more notches, the one or more notches each configured to accommodate at least a portion of one of the one or more deswirl vanes. In an embodiment, the one or more deswirl vanes each include one or more notches, the one or more notches each configured to accommodate at least a portion of the capacity control valve.

In an embodiment, the capacity control valve has a linear meridional profile on a side opposite the curved surface, the linear meridional profile contacting an edge of the side stream injection port.

In an embodiment, a side of the capacity control valve opposite the curved surface is configured such that when the capacity control valve is between the open position and the closed position, the fluid can flow past the capacity control valve on the side of the capacity control valve opposite the curved surface. In an embodiment, the side of the capacity control valve opposite the curved surface includes a second curved surface. In an embodiment, the side of the capacity control valve opposite the curved surface includes one or more channels configured to allow flow of the side stream of the fluid.

In an embodiment, a heating, ventilation, air conditioning, and refrigeration (HVACR) circuit includes a centrifugal compressor, a condenser, an expander, and an evaporator. The centrifugal compressor includes a first stage impeller and a second stage impeller. The centrifugal compressor also includes side stream injection port located between the first stage impeller and the second stage impeller. The side stream injection port is configured to receive a side stream of a fluid. The centrifugal compressor further includes a capacity control valve. The capacity control valve is configured to extend and retract through the side stream injection port. The capacity control valve has a curved surface facing a direction of flow from the first stage impeller to the second stage impeller. The capacity control valve is configured to be extended through the side stream injection port between an open position where the side stream of the fluid can flow through the side stream injection port and a closed position where the capacity control valve obstructs flow of the side stream of the fluid through the side stream injection port.

In an embodiment, the side stream of the fluid is from the condenser to the side stream injection port.

In an embodiment, the HVACR circuit further includes an economizer and wherein the side stream of the fluid is from the economizer to the side stream injection port.

In an embodiment, the HVACR circuit further includes an intercooler and wherein the side stream of the fluid is from the intercooler to the side stream injection port.

In an embodiment, the capacity control valve has a linear meridional profile on a side opposite the curved surface, the linear meridional contacting an edge of the side stream injection port. In an embodiment, a side of the capacity control valve opposite the curved surface is configured such that when the capacity control valve is between the open position and the closed position, the fluid can flow past the capacity control valve on the side of the capacity control valve opposite the curved surface.

<FIG> shows a sectional view of a compressor <NUM> according to an embodiment when a capacity control valve is in a fully open position. Compressor <NUM> can have a cylindrical structure such that the sectional view shown in <FIG> be repeated or continuous through <NUM>° of rotation about axis A of the compressor <NUM>.

Compressor <NUM> is a multi-stage centrifugal compressor according to an embodiment. Compressor <NUM> includes an inlet guide vane <NUM> where a core flow of fluid to be compressed is received. Compressor <NUM> includes a first stage impeller <NUM> driven by rotation of shaft <NUM>, a diffuser <NUM> downstream of the first stage impeller <NUM>, and a return bend <NUM> downstream of the diffuser <NUM>. Compressor <NUM> further includes one or more deswirl vanes <NUM> downstream of the return bend <NUM>. Compressor <NUM> includes a side stream injection port <NUM> and a capacity control valve <NUM>. Compressor <NUM> includes a second stage impeller <NUM> downstream of the deswirl vanes <NUM> and the side stream injection port <NUM>, with a volute scroll <NUM> and a discharge conic <NUM> downstream of the second stage impeller <NUM>.

While compressor <NUM> is shown in <FIG> as a two-stage compressor, compressors according to embodiments can include any number of stages, with the side stream injection port <NUM> and the capacity control valve <NUM> are provided in an interstage flow path between any two stages of the compressor. For example, compressor <NUM> can be a three-stage compressor, with the side stream injection port <NUM> and capacity control valve <NUM> disposed between the exhaust of the second stage and the intake of the third stage, or the like.

Flow of working fluid into compressor <NUM> may be controlled using one or more inlet guide vanes <NUM>. The one or more inlet guide vanes <NUM> can be configured to obstruct or permit flow of working fluid into the compressor <NUM>. In an embodiment, each of the inlet guide vanes <NUM> can be a rotating vane, for example, each rotating vane forming a section of a circle such that when all rotating vanes are in a closed position, the inlet guide vanes <NUM> obstruct an inlet of the compressor <NUM>. The one or more inlet guide vanes <NUM> can be movable between a fully open position and the closed position. In the fully open position the effect of the inlet guide vanes <NUM> on flow into compressor <NUM> can be minimized, for example by positioning the inlet guide vanes <NUM> such that the plane of each vane is substantially parallel to the direction of flow of working fluid into the inlet of compressor <NUM>. In an embodiment, each or all of the one or more inlet guide vanes <NUM> can be varied continuously from the fully open position to the closed position, through one or more partially open positions.

Compressor <NUM> includes a first stage impeller <NUM>. The first stage impeller <NUM> includes a plurality of blades. The first stage impeller <NUM> is configured to draw in the working fluid that passes the one or more inlet guide vanes <NUM> when rotated, and to expel the working fluid towards diffuser <NUM>. The first stage impeller <NUM> is joined to shaft <NUM>. Shaft <NUM> is rotated by, for example, a prime mover such as a motor.

Diffuser <NUM> receives the fluid discharged from first stage impellers <NUM> and directs the flow of the fluid towards return bend <NUM>. Return bend <NUM> changes the direction of the flow of the fluid such that it travels through the deswirl vanes <NUM> towards the second stage impeller <NUM>.

One or more deswirl vanes <NUM> are vanes extending from the return bend <NUM> towards the second stage impeller <NUM>. The deswirl vanes <NUM> are shaped to straighten the flow of the fluid as the flow passes towards the second stage impeller <NUM>. The deswirl vanes <NUM> can include notches configured to receive at least a portion of the capacity control valve <NUM>.

Side stream injection port <NUM> is a port configured to allow a side stream to be introduced into the interstage flow of fluid through compressor <NUM>. The side stream injection port <NUM> includes a leading end <NUM> and a trailing end <NUM>, with the leading end <NUM> towards the return bend <NUM> and the trailing end <NUM> towards the second stage impeller <NUM>. Side stream injection port <NUM> fluidly connects a side stream flow channel <NUM> with the interstage flow. The side stream flow channel <NUM> can receive a side stream of fluid from within a fluid circuit including the compressor <NUM>. The source of the side stream of fluid received by side stream flow channel can be from one or more of a condenser, an economizer, an intercooler, a heat exchanger, or any other suitable source of fluid that is at an intermediate pressure, between the suction pressure and the discharge pressure of the compressor <NUM>. The side stream injection port <NUM> can be a ring shape surrounding an intake of the second stage impeller <NUM>. The side stream injection port <NUM> can be provided between the return bend <NUM> and the second stage impeller <NUM>.

Capacity control valve <NUM> is a valve configured regulate the flow through the side stream injection port <NUM>. Capacity control valve <NUM> is configured to be extended axially through the side stream injection port <NUM> such that it extends substantially perpendicular to a direction of flow of the interstage flow from deswirl vane <NUM> towards the second stage impeller <NUM>. Capacity control valve <NUM> is configured to be able to prohibit flow through side stream injection port <NUM> in a closed position, for example by including a portion having a thickness corresponding to the width of the side stream injection port <NUM> from leading end <NUM> to trailing end <NUM>. In an embodiment, capacity control valve <NUM> is controlled in conjunction with inlet guide vanes <NUM>. In an embodiment, capacity control valve <NUM> is controlled independently of inlet guide vanes <NUM>.

Capacity control valve <NUM> includes a leading side <NUM> facing towards the return bend <NUM> and a trailing side <NUM> facing towards an inlet into second stage impeller <NUM>. Leading side <NUM> includes curved surface <NUM> extending towards a tip <NUM> of the capacity control valve <NUM>. The curved surface <NUM> can reduce the cross-sectional thickness of the capacity control valve <NUM> from a thickness corresponding to the width of the side stream injection port <NUM> at the base of the curved surface <NUM> to a smaller thickness at the tip <NUM>. The change in the cross-sectional thickness of capacity control valve <NUM> over the length of curved surface <NUM> towards tip <NUM> is configured to vary the amount of flow through the side stream injection port based on the extension of the capacity control valve <NUM>. In the embodiment shown in <FIG>, trailing side <NUM> can be, for example, a linear profile in the longitudinal direction of the capacity control valve <NUM> configured to always be in contact with trailing end <NUM> of the side stream injection port <NUM>, such that all flow of the side stream into the interstage flow is over the leading side <NUM>.

Where side stream injection port <NUM> has a ring shape, the capacity control valve <NUM> can have a corresponding ring shape. In an embodiment, the capacity control valve is a single ring. In an embodiment, the capacity control valve includes a plurality of ring segments. In an embodiment, the capacity control valve <NUM> includes one or more notches configured to avoid contact between the capacity control valve <NUM> and one or more deswirl vanes <NUM> as the capacity control valve <NUM> is extended. In an embodiment, the capacity control valve can be moved from a fully open position where the tip <NUM> is located within the side stream injection port <NUM> or the side stream channel <NUM>, and a fully closed position, where the capacity control valve <NUM> obstructs the side stream injection port <NUM> from leading end <NUM> to trailing end <NUM>.

In the fully open position of the capacity control valve <NUM>, the tip <NUM> of the capacity control valve <NUM> does not extend through the side stream injection port <NUM>. Accordingly, the interstage flow through the deswirl vane <NUM> is not obstructed, and obstruction of the side stream injection port <NUM> by the capacity control valve is at a minimum. The side stream fluid passes over the curved surface <NUM> to join the interstage flow between return bend <NUM> and second stage impeller <NUM>. The fully open position can be used when the compressor <NUM> is operating at or near a full-load capacity.

Second stage impeller <NUM> is used to achieve the second stage of compression. Second stage impeller <NUM> draws in the combined interstage and side stream flows and expels the fluid towards volute scroll <NUM>. Second stage impeller <NUM> can be rotated by shaft <NUM>, which is also used to rotate first stage impeller <NUM>. Fluid at the volute scroll <NUM> can then be discharged from compressor <NUM> at discharge conic <NUM>.

In an embodiment, the side stream provided through side stream injection port <NUM> can be received from an economizer, such as the economizer <NUM> shown in <FIG> and described below. The economizer can be a flash-tank economizer, where flash or bypass gas rises and can be directed to the side stream flow channel <NUM>. The gas from the economizer being directed to the side stream flow channel <NUM> can reduce or eliminate the presence of gas in the liquid being passed to an evaporator of the HVACR system including compressor <NUM>. This can in turn improve the absorption of energy at the evaporator without further subcooling by providing more saturated liquid working fluid. In the full load cycle corresponding to the fully open position of capacity control valve <NUM>, the pressure at the side stream injection port <NUM> can allow the entrained vapor to be substantially removed from the working fluid in the economizer.

<FIG> shows a sectional view of the compressor shown in <FIG> when the capacity control valve <NUM> is in a high flow position. The high flow position shown in <FIG> can be used in a partial load condition where the load is relatively close to full load for the compressor <NUM>. In the high flow position shown in <FIG>, the capacity control valve <NUM> is extended axially such that it partially extends through side stream injection port <NUM>. The leading side <NUM> of the capacity control valve <NUM> partially deflects the interstage flow in compressor <NUM> due to the projection of the capacity control valve reducing the size of the passage for interstage flow. The capacity control valve <NUM> restricts flow through the side stream injection port to a greater extent than when in the fully-open position shown in <FIG> and described above, with curved surface <NUM> reducing the orifice size by being closer to the leading end <NUM> of the side stream injection port <NUM>. The trailing side <NUM> of the capacity control valve <NUM> continues to be in contact with the trailing end <NUM> of the side stream injection port <NUM>, and all flow through side stream injection port <NUM> passes between the leading end <NUM> of side stream injection port <NUM> and the leading side <NUM> of capacity control valve <NUM>. Optionally, inlet guide vane <NUM> can be rotated to partially obstruct flow to the first stage impeller <NUM> of compressor <NUM>.

<FIG> shows a sectional view of the compressor shown in <FIG> when the capacity control valve is in a low flow position. The low flow position shown in <FIG> can be used in a partial load condition where the load is below the full load for the compressor <NUM>, and less than the load where the capacity control valve is in a high flow position such as in <FIG>. In the low flow position shown in <FIG>, the capacity control valve <NUM> is extended axially such that it extends through side stream injection port <NUM>, extending further than the high flow position shown in <FIG>. The leading side <NUM> of the capacity control valve <NUM> deflects the interstage flow in compressor <NUM> due to the greater projection of the capacity control valve <NUM>, further reducing the size of the passage for interstage flow. The capacity control valve <NUM> restricts flow through the side stream injection port to a greater extent than when in the high flow position shown in <FIG> and described above, with curved surface <NUM> further reducing the orifice size by being even closer to the leading end <NUM> of the side stream injection port <NUM>. The trailing side <NUM> of the capacity control valve <NUM> continues to be in contact with the trailing end <NUM> of the side stream injection port <NUM>, and all flow through side stream injection port <NUM> passes between the leading end <NUM> of side stream injection port <NUM> and the leading side <NUM> of capacity control valve <NUM>. Optionally, inlet guide vane <NUM> can be rotated to further obstruct flow to the first stage impeller <NUM> of compressor <NUM> compared to its position in the high flow position shown in <FIG>.

<FIG> shows a sectional view of the compressor shown in <FIG> when the capacity control valve is in a closed position. The closed position shown in <FIG> can be used when the compressor <NUM> is in a partial-load condition at or near a minimum load for the compressor. In the closed position, capacity control valve <NUM> partially or completely obstructs side stream injection port <NUM>, from leading end <NUM> to trailing end <NUM>. It is appreciated that due to manufacturing tolerances, wear, etc. that there may be some leakage even when the capacity control valve <NUM> is configured to completely obstruct the side stream and is in the closed position. In an embodiment, capacity control valve <NUM> is sized such that it does not contact side stream injection port <NUM> and allows some flow to continue through side stream injection port <NUM> even in the fully extended closed position. The extension of the capacity control valve <NUM> into the interstage flow through compressor <NUM> is at a maximum, reducing the size of the orifice through which the interstage flow passes from return bend <NUM> towards second stage impeller <NUM>. Accordingly, this position imparts the greatest additional velocity to the interstage flow, while prohibiting the side stream flow from joining the interstage flow. Optionally, inlet guide vane <NUM> can be rotated to further obstruct flow to the first stage impeller <NUM> of compressor <NUM>, for example by pacing the inlet guide vane <NUM> in a minimum-flow position.

Compressor <NUM> is a multi-stage centrifugal compressor. Compressor <NUM> includes an inlet guide vane <NUM> where a core flow of fluid to be compressed is received. Compressor <NUM> includes a first stage impeller <NUM> driven by rotation of shaft <NUM>, a diffuser <NUM> downstream of the first stage impeller <NUM>, and a return bend <NUM> downstream of the diffuser <NUM>. Compressor <NUM> further includes one or more deswirl vanes <NUM> downstream of the return bend <NUM>. Compressor <NUM> includes a side stream injection port <NUM> and a capacity control valve <NUM>. Compressor <NUM> includes a second stage impeller <NUM> downstream of the deswirl vanes <NUM> and the side stream injection port <NUM>, with a volute scroll <NUM> and a discharge conic <NUM> downstream of the second stage impeller <NUM>.

Compressor <NUM> can include one or more inlet guide vane <NUM> to control flow of working fluid into the compressor <NUM>. The inlet guide vanes <NUM> can be substantially similar to the inlet guide vanes <NUM> described above and shown in <FIG>. The one or more inlet guide vanes <NUM> can be configured to obstruct or permit flow of working fluid into the compressor <NUM>. In an embodiment, each of the inlet guide vanes <NUM> can be a rotating vane, for example, each rotating vane forming a section of a circle such that when all rotating vanes are in a closed position, the inlet guide vanes <NUM> obstruct an inlet of the compressor <NUM>. The one or more inlet guide vanes <NUM> can be movable between a fully open position and the closed position. In the fully open position the effect of the inlet guide vanes <NUM> on flow into compressor <NUM> can be minimized, for example by positioning the inlet guide vanes <NUM> such that the plane of each vane is substantially parallel to the direction of flow of working fluid into the inlet of compressor <NUM>. In an embodiment, each or all of the one or more inlet guide vanes <NUM> can be varied continuously from the fully open position to the closed position.

Compressor <NUM> includes a first stage impeller <NUM>. The first stage impeller <NUM> is driven by shaft <NUM>. Shaft <NUM> is rotated by, for example, a prime mover such as a motor. The first stage impellers <NUM> are configured to draw in the working fluid that passes the one or more inlet guide vanes <NUM> when rotated, and to expel the working fluid towards diffuser <NUM>.

Side stream injection port <NUM> is a port configured to allow a side stream to be introduced into the interstage flow of fluid through compressor <NUM>. The side stream injection port <NUM> includes a leading end <NUM> and a trailing end <NUM>, with the leading end <NUM> towards the return bend <NUM> and the trailing end <NUM> towards the second stage impeller <NUM>. Side stream injection port <NUM> fluidly connects a side stream flow channel <NUM> with the interstage flow. The side stream flow channel <NUM> can receive a side stream of fluid from within a fluid circuit including the compressor <NUM>. The source of the side stream of fluid received by side stream flow channel <NUM> can be from one or more of a condenser, an economizer, an intercooler, a heat exchanger, or any other suitable source of fluid that is at an intermediate pressure, between the suction pressure and the discharge pressure of the compressor <NUM>. The side stream injection port <NUM> can be a ring shape surrounding an intake of the second stage impeller <NUM>. The side stream injection port <NUM> can be provided between the return bend <NUM> and the second stage impeller <NUM>.

Capacity control valve <NUM> is a valve that configured regulate the flow through the side stream injection port <NUM>. Capacity control valve <NUM> is configured to be extended axially through the side stream injection port <NUM> such that it extends substantially perpendicular to a direction of flow of the interstage flow from deswirl vane <NUM> towards the second stage impeller <NUM>. Capacity control valve <NUM> is configured to be able to prohibit flow through side stream injection port <NUM> in a closed position, for example by including a portion having a thickness corresponding to the width of the side stream injection port <NUM> from leading end <NUM> to trailing end <NUM>. In an embodiment, capacity control valve <NUM> is controlled in conjunction with inlet guide vanes <NUM>. In an embodiment, capacity control valve <NUM> is controlled independently of inlet guide vanes <NUM>.

Capacity control valve <NUM> includes a leading side <NUM> facing towards the return bend <NUM> and a trailing side <NUM> facing towards an inlet into second stage impeller <NUM>. Leading side <NUM> includes curved surface <NUM> extending towards a tip <NUM> of the capacity control valve <NUM>. The curved surface <NUM> can cause the distance between capacity control valve <NUM> and leading end <NUM> of side stream injection port <NUM> to be varied as capacity control valve <NUM> is axially extended or retracted.

Trailing side <NUM> includes one or more passages <NUM> configured to allow the side stream flow from side stream flow channel <NUM> to pass through the side stream injection port <NUM> and be introduced into the interstage flow on the trailing side <NUM> of the capacity control valve <NUM>. In an embodiment, passage <NUM> includes one or more channels having openings on the trailing side <NUM> of the capacity control valve <NUM>. In an embodiment, passage <NUM> is a cutout or scalloping formed in the trailing side <NUM>, such that in some positions of capacity control valve <NUM>, a gap exists between the trailing side <NUM> and the trailing end <NUM> of the side stream injection port <NUM>.

In the fully open position of the capacity control valve <NUM>, side stream flow passes from the side stream flow channel <NUM> through side stream injection port <NUM>, between the leading end <NUM> of the side stream injection port <NUM> and the leading side <NUM> of the capacity control valve <NUM>. Tip <NUM> of the capacity control valve <NUM> is located within the side stream injection port <NUM> or retracted into the side stream flow channel <NUM>, and capacity control valve <NUM> does not substantially affect the interstage flow passing from return bend <NUM> to second stage impeller <NUM>. Optionally, in the fully open position shown in <FIG>, inlet guide vane <NUM> can be in an open position where it provides little to no resistance to flow into the first stage impeller <NUM>. The fully open position shown in <FIG> can be used, for example, when compressor <NUM> is being operated at or near full load capacity. In the embodiment shown in <FIG>, when in the fully open position shown in <FIG>, some or all of the side stream flow passing through side stream injection port <NUM> can pass over the leading side <NUM> of capacity control valve <NUM>.

<FIG> shows a sectional view of the compressor shown in <FIG> when the capacity control valve <NUM> is in a high flow position. The high flow position shown in <FIG> can be used in a partial load condition where the load is relatively close to full load for the compressor <NUM>. In the high flow position shown in <FIG>, capacity control valve <NUM> is extended such that tip <NUM> projects into the path for interstage flow from return bend <NUM> to the second impeller <NUM>, partially obstructing the path for the interstage flow. In the high flow position of the embodiment shown in <FIG>, a first gap exists between the leading end <NUM> of the side stream injection port and the leading side <NUM> of the capacity control valve <NUM>, and a second gap exists at passage <NUM> between the trailing side <NUM> of the capacity control valve <NUM> and the trailing end <NUM> of the side stream injection port <NUM>. Each of the first and second gaps allow some of the side stream flow to join the interstage flow. The portion passing through the second gap experiences less of the pressure exerted by the interstage flow due to its introduction on the trailing side <NUM> of the capacity control valve <NUM>. Optionally, in the high flow position shown in <FIG>, inlet guide vane <NUM> can be in a high flow position where the inlet guide vane <NUM> provides increased resistance to flow into the first stage impeller <NUM> compared to the fully open position shown in <FIG>, but less resistance to flow than the low flow or closed positions shown in <FIG> and <FIG>, respectively. In the high-flow position shown in <FIG>, flow through side stream injection port <NUM> can include both flow over the leading side <NUM> and past the trailing side <NUM> of the capacity control valve.

<FIG> shows a sectional view of the compressor shown in <FIG> when the capacity control valve <NUM> is in a low flow position. The low flow position shown in <FIG> can be used in a partial load condition where the load is below the full load for the compressor <NUM>, and less than the load where the capacity control valve is in a high flow position such as in <FIG>. In the low flow position shown in <FIG>, capacity control valve <NUM> is extended further into the interstage flow from return bend <NUM> to second impeller <NUM>. The capacity control valve <NUM> thus provides even greater resistance to the interstage flow when compared to the high flow position shown in <FIG>. In the low flow position of the embodiment shown in <FIG>, a first gap exists between the leading end <NUM> of the side stream injection port and the leading side <NUM> of the capacity control valve <NUM>, and a second gap exists at passage <NUM> between the trailing side <NUM> of the capacity control valve <NUM> and the trailing end <NUM> of the side stream injection port <NUM>. Compared to the first and second gaps shown of the high flow position shown in <FIG>, in the low flow position of <FIG>, the second gap is relatively larger compared to the first, and a greater proportion of the side stream flow passes through the second gap to join the interstage flow relative to the amount of the side stream flow passing through the first gap. Optionally, in the low flow position shown in <FIG>, inlet guide vane <NUM> can be in a low flow position where the inlet guide vane <NUM> provides increased resistance to flow into the first stage impeller <NUM> compared to the high flow position shown in <FIG>, but less resistance to flow than the closed positions shown in <FIG>. In the low-flow position shown in <FIG>, flow through side stream injection port <NUM> can primarily or entirely be past the trailing side <NUM> of the capacity control valve. The shape of the leading side <NUM> and of passage <NUM> can each or both be selected to control the relative amount of flow being introduced on either the leading side <NUM> or trailing side <NUM> of the capacity control valve <NUM>, and how those relative amounts vary with the position of capacity control valve <NUM> from the fully open position through the closed position as shown in <FIG>.

In an embodiment, side stream flow channel <NUM> can receive the side stream flow from an economizer, such as economizer <NUM> shown in <FIG> and described below. Providing passage <NUM> in capacity control valve <NUM> can allow capacity control valve <NUM> to not only control the quantity of flow being introduced, but the particular point at which the side stream is introduced in side stream injection port <NUM>, and the pressure at the point of introduction. Controlling the position of the point of introduction of side stream flow can provide control over the relationship between core flow and side stream flow in the compressor. Control of the point of introduction can improve economizer effectiveness across different load conditions. The low flow position shown in <FIG> can be used when compressor <NUM> is operated at part load. When the compressor <NUM> is operated at part load, the static pressure at the side stream injection port <NUM>, particularly between leading end <NUM> of the side stream injection port <NUM> and the leading side <NUM> of the capacity control valve <NUM>, can be relatively elevated. The pressure within the economizer is a function of the static pressure at the injection location in compressor <NUM>, in addition to pipe losses and fixed orifice pressure drops for the system. The elevated pressure at side stream injection port <NUM> can therefore lead to an elevated pressure at the economizer, reducing effectiveness in removing flash or bypass gas from the fluid contained within. Passage <NUM>, by being on an opposite side of the capacity control valve <NUM> from leading side <NUM> that is facing the interstage flow within compressor <NUM>, is subject to a reduced pressure in comparison to the pressure on the leading side <NUM>, or the static pressure at the side stream injection port <NUM> in the embodiment shown in <FIG>. The reduced pressure at such an injection point can correspondingly lower the pressure within the economizer as described above, improving the release of flash or bypass gas from liquid in the economizer and its removal from the stream of working fluid passing to the evaporator. This improves the heat transfer at the evaporator and can also reduce recompression losses in the system including compressor <NUM> having capacity control valve <NUM> including passages <NUM>.

<FIG> shows a sectional view of the compressor shown in <FIG> when the capacity control valve <NUM> is in a closed position. The closed position shown in <FIG> can be used when the compressor <NUM> is in a partial-load condition at or near a minimum load for the compressor. In the closed position, capacity control valve <NUM> partially or completely obstructs side stream injection port <NUM>, from leading end <NUM> to trailing end <NUM>. It is appreciated that due to manufacturing tolerances, etc., there may be some possible leakage even when capacity control valve <NUM> is in the closed position. In an embodiment, capacity control valve <NUM> may be sized such that it does not contact side stream injection port <NUM>, and allows some flow through the gap between the side stream injection port <NUM> and the capacity control valve <NUM>. Any features of capacity control valve <NUM> configured to allow the introduction of the side stream flow on the trailing side <NUM> of the capacity control valve <NUM> such as passage <NUM> can be configured such that they do not permit such flow when capacity control valve <NUM> in the closed position. For example, as shown in <FIG>, a scalloped portion on the trailing side <NUM> forming passage <NUM> in this embodiment is sized and positioned such the trailing side <NUM> contacts the trailing end <NUM> of side stream injection port <NUM> when the capacity control valve <NUM> is extended into the closed position. The extension of the capacity control valve <NUM> into the interstage flow through compressor <NUM> is at a maximum, reducing the size of the orifice through which the interstage flow passes from return bend <NUM> towards second stage impeller <NUM>. Accordingly, this position imparts the greatest additional velocity to the interstage flow, while prohibiting the side stream flow from joining the interstage flow. Optionally, inlet guide vane <NUM> can be rotated to further obstruct flow to the first stage impeller <NUM> of compressor <NUM>, for example by pacing the inlet guide vane <NUM> in a minimum-flow position.

<FIG> shows a heating, ventilation, air conditioning and refrigeration (HVACR) circuit according to an embodiment. HVACR circuit <NUM> includes compressor <NUM>, condenser <NUM>, expander <NUM>, and evaporator <NUM>.

Compressor <NUM> is a centrifugal compressor, for example compressor <NUM> shown in <FIG> or compressor <NUM> shown in <FIG> and described above.

Condenser <NUM> receives working fluid from compressor <NUM> and allows the working fluid to reject heat, for example to air or another heat exchange medium. In an embodiment, a fluid line from the condenser <NUM> can convey some of the working fluid of HVACR circuit <NUM> back to compressor <NUM>, as the side stream flow provided to the side stream flow injection port of the compressor <NUM>, such as side stream injection ports <NUM> or <NUM> described above and shown in <FIG>. Condensed working fluid from condenser <NUM> can then pass to expander <NUM>.

Expander <NUM> expands the working fluid passing through as the fluid passes through HVACR circuit <NUM>. Expander <NUM> can be any suitable expander for the working fluid within the HVACR circuit <NUM>, such as, for example, an expansion valve, one or more expansion orifices, or any other suitable expansion device for use in an HVACR circuit.

Evaporator <NUM> is a heat exchanger where the working fluid of HVACR circuit <NUM> absorbs heat, for example from an ambient environment or a fluid to be cooled such as water in a water chiller HVACR system. The evaporator <NUM> can be, for example, an indoor coil of an air conditioner or a heat exchanger configured to cool water used in an HVACR system including the HVACR circuit <NUM>.

HVACR circuit <NUM> can further include an intercooler <NUM>. Intercooler <NUM> is a heat exchanger where working fluid from the HVACR circuit exchanges heat with the interstage flow within compressor <NUM>. The working fluid that exchanges heat with the interstage flow in intercooler <NUM> can be sourced from, for example, evaporator <NUM>, between expander <NUM> and evaporator <NUM>, or between the evaporator <NUM> and the compressor <NUM>. Some or all of the working fluid that exchanges heat with the interstage flow can then be reintroduced into HVACR circuit <NUM> downstream of where the working fluid is sourced. In an embodiment, at least some of the working fluid from intercooler <NUM> can be directed to a side stream flow channel of compressor <NUM> instead of returning to the ordinary flow path through HVACR circuit <NUM>. The side stream flow channel can be, for example, side stream flow channel <NUM> or side stream flow channel <NUM> of the compressors <NUM> and <NUM> described above and shown in <FIG> and <FIG>.

<FIG> shows an economized HVACR circuit <NUM> according to an embodiment. In <FIG>, compressor <NUM>, condenser <NUM> and evaporator <NUM> are included as in HVACR circuit <NUM> described above and shown in <FIG>, with compressor <NUM> being a multi-stage compressor in this embodiment. HVACR circuit <NUM> includes a first expander <NUM> and a second expander <NUM>. Each of first expander <NUM> and second expander <NUM> can be any suitable expander for the working fluid within the HVACR circuit <NUM> such as, for example, an expansion valve, one or more expansion orifices, or any other suitable expansion device for use in an HVACR circuit. Economizer <NUM> can be disposed between first and second expanders <NUM>, <NUM>, such that working fluid of HVACR circuit <NUM> is at an intermediate pressure at the economizer <NUM>. The economizer <NUM> can be used as a source for the side stream introduced into compressor <NUM>, for example through a side stream flow channel such as side stream flow channel <NUM> or side stream flow channel <NUM> as described above and shown in <FIG> and <FIG>.

<FIG> shows a sectional view of a centrifugal compressor according to an embodiment along an interstage flow path. Centrifugal compressor <NUM> includes compressor housing <NUM>. Compressor housing <NUM> in part defines an interstage flow path <NUM>. The interstage flow path includes deswirl vanes <NUM> radially distributed around the interstage flow path <NUM>. Capacity control valve ring <NUM> extends into interstage flow path <NUM>, upstream of following stage inlet <NUM>. Capacity control valve ring can <NUM> be, for example, capacity control valve <NUM> or capacity control valve <NUM> as described above and shown in <FIG> and <FIG>. Capacity control valve ring <NUM> can be a single continuous ring or composed of a plurality of ring segments that combine to provide the ring shape. Following stage inlet <NUM> receives flow passing the capacity control valve ring <NUM> and allows the flow to enter into the following stage impeller <NUM>.

<FIG> shows a sectional view of a portion of a centrifugal compressor according to an embodiment. In the view of centrifugal compressor <NUM>, the interaction between the deswirl vanes <NUM> and the capacity control valve ring <NUM>. Deswirl vanes <NUM> can be any of the deswirl vanes shown in <FIG>, <FIG>, or <FIG>. Capacity control valve ring <NUM> can be any of the capacity control valves shown in <FIG>, <FIG>, or <FIG>. Capacity control valve ring includes notches <NUM>, each of notches <NUM> configured to accommodate one of the deswirl vanes <NUM> such that the capacity control valve ring <NUM> can be extended into a flow path including the deswirl vanes <NUM> without mechanically interfering with the deswirl vanes <NUM>. In an embodiment, notches corresponding to notches <NUM> can instead be included on each of the deswirl vanes <NUM> such that the deswirl vanes <NUM> do not contact the capacity control valve ring <NUM> as it is extended. In an embodiment, notches <NUM> are provided along with corresponding notches on the deswirl vanes <NUM>. In this embodiment, the notches <NUM> can have a depth that is less than an entire height of the area where capacity control valve ring <NUM> could contact deswirl vanes <NUM>, and the notches in the deswirl vanes have a depth such that they accommodate any portion of capacity control valve ring <NUM> that would otherwise contact the deswirl vanes <NUM> in the absence of said notches.

Claim 1:
A centrifugal compressor (<NUM>), comprising:
a first stage impeller (<NUM>);
a second stage impeller (<NUM>);
a side stream injection port (<NUM>) located between the first stage impeller and the second stage impeller, the side stream injection port configured to receive a side stream of a fluid; and
a capacity control valve (<NUM>), the capacity control valve configured to extend and retract through the side stream injection port, wherein:
the capacity control valve has a curved surface (<NUM>) facing a direction of flow from the first stage impeller to the second stage impeller; and
the capacity control valve is configured to be extended through the side stream injection port between an open position where the side stream of the fluid can flow through the side stream injection port and a closed position where the capacity control valve obstructs flow of the side stream of the fluid through the side stream injection port.