Patent Application
20240392774
The present disclosure relates to pump control, and more particularly to control for variable displacement pumps (VDPs).
Variable displacement pumps have non-linear mechanical efficiencies as a function of percentage of displacement. Temperature rise in the fluid across the pump is inversely proportional to the mechanical efficiency. As a result, as a variable displacement pump decreases output flow, temperature rise in the fluid across the pump goes up.
The conventional techniques have been considered satisfactory for their intended purpose. However, there is an ever present need for improved systems and methods for control of VDPs. This disclosure provides a solution for this need.
A system includes a variable displacement pump (VDP) in fluid communication with an inlet line and with an outlet line. The VDP includes a variable displacement mechanism configured to vary pressure to the outlet line. A bypass valve (BPV) includes a BPV inlet in fluid communication with the outlet line, and a BPV outlet in fluid communication with a bypass line that feeds into the inlet line upstream of the VDP. An actuator is operatively connected to control the BPV to vary flow from the BPV inlet to the bypass line. An electromechanical actuator (EMA) is operatively connected to actuate the variable displacement mechanism. A controller is operatively connected: to the EMA to control the variable displacement mechanism; and to the actuator to control recirculation flow passed through the BPV based on requested flow from a downstream system supplied by the outlet line and based on a predetermined low threshold of flow through the VDP. The BPV outlet can be the only outlet of the BPV so all flow through the BPV is supplied to the BPV outlet. A temperature sensor is operatively connected to the outlet line to generate sensor output indicative of fluid temperature in the outlet line, wherein the temperature sensor is operatively connected to the controller for active control of the EMA and/or of the actuator based on temperature in the outlet line.
The controller can be configured to control the BPV to maintain a baseline flow through the BPV under a first condition wherein requested flow from the downstream system is above than the predetermined low threshold. The controller can be configured to control the BPV to increase the flow through the BPV above the baseline flow for a second flow condition wherein requested flow from the downstream system is at or below the predetermined low threshold.
An electrohydraulic servo valve (EHSV) can be connected in fluid communication with the BPV by a first control line. The EHSV can be connected in fluid communication with both the inlet line and with the outlet line through respective connection lines. The EHSV can be operatively connected to the controller for active control of the EHSV to actuate the BPV.
A first position sensor can be operatively connected to the BPV to provide sensor output indicative of position of a valve member of the BPV. The first position sensor can be operatively connect the controller to provide feedback for controlling the BPV. A second position sensor can be operatively connected to the variable displacement mechanism to provide sensor output indicative of position of the variable displacement mechanism, wherein the second position sensor is operatively connect the controller to provide feedback for controlling the variable displacement mechanism.
The controller can be operatively connected to receive input indicative of flow demanded by the downstream system supplied by the outlet line. The controller can be configured to control position of the valve member of the BPV to maintain bypass flow through the BPV in the second condition wherein the controller governs the bypass flow through the BPV according to
BF=PF−DSFD
wherein BF is flow through the BPV, PF is flow through the VDP, and DSFD is flow demanded by the downstream system supplied by the outlet line.
A method includes receiving input indicative of flow demanded by a downstream system supplied from an outlet line of a variable displacement pump (VDP). The method includes controlling a bypass valve (BPV) to recirculate flow from the outlet line to an input line of the VDP in the event of flow demanded by the downstream system dropping below a predetermined low threshold of flow through the VDP. The method includes controlling displacement of the VDP, wherein at least one of controlling the BPV and controlling displacement is based on fluid temperature in the output line.
The method can include controlling the BPV to recirculate flow from the outlet line to the inlet line at a constant base recirculation rate in the event of flow demanded by the downstream system being at or above the predetermined low threshold of flow through the VDP. The base recirculation rate can be zero recirculation flow. Controlling the BPV to recirculate flow can include governing the bypass flow through the BPV according to
BF=PF−DSFD
wherein BF is flow through the BPF, PF is flow through the VDP, and DSFD is flow demanded by the downstream system supplied by the outlet line. The method can include receiving data from a sensor indicative of position of a valve member of the BPV. Controlling the BPV can include controlling the BPV based on position of the valve member. The method can include receiving data from a sensor indicative of position of a variable displacement mechanism of the VDP. Controlling displacement can include controlling displacement of the VDP based on position of the variable displacement mechanism.
These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.
So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:
Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an embodiment of a system in accordance with the disclosure is shown in
The system 100 includes a variable displacement pump (VDP) 102 in fluid communication with an inlet line 104 and with an outlet line 106. The VDP 102 includes a variable displacement mechanism 108 configured to vary pressure to the outlet line 106. A bypass valve (BPV) 110 includes a BPV inlet 112 in fluid communication with the outlet line 106, and a BPV outlet 114 in fluid communication with a bypass line 116 that feeds into the inlet line 104 upstream of the VDP 102. An actuator 118 is operatively connected to control the BPV 110 to vary flow from the BPV inlet 112 to the bypass line 116. An electromechanical actuator (EMA) 136 is operatively connected to actuate the variable displacement mechanism 108.
A controller 120 is operatively connected: to the EMA 136 to control the variable displacement mechanism 108; and to the actuator 118 to control recirculation flow passed through the BPV 110 based on requested flow from a downstream system 122 supplied by the outlet line 106 and based on a predetermined low threshold of flow through the VDP 104. A temperature sensor 146 is operatively connected to the outlet line 106 to generate sensor output indicative of fluid temperature in the outlet line 106. The temperature sensor 146 is operatively connected to the controller 120 for active control of the EMA 136 and/or of the actuator 118 based on fluid temperature in the outlet line 106. The downstream system 122 can be a combustor, augmenter, or other gas generator of a gas turbine engine, for example. The low threshold of flow of the VDP 104 can be the threshold below which the VDP 104 cannot self-lubricate, or other design requirements for low or minimum flow. The BPV outlet 114 can be the only outlet of the BPV 110 so all flow through the BPV 110 from the BPV inlet 112 is supplied to the BPV outlet 114.
The controller 120 is configured, e.g. including analog circuitry, digital logic, and/or machine readable instructions, to control the BPV 110 to maintain a baseline flow through the BPV 110 under a first condition wherein requested flow from the downstream system 122 is above than the predetermined low threshold. The controller 122 is configured to control the BPV 110 to increase the flow through the BPV 110 above the baseline flow for a second flow condition wherein requested flow from the downstream system 122 is at or below the predetermined low threshold.
The actuator 118 includes an electrohydraulic servo valve (EHSV) 124 that is connected in fluid communication with the BPV 110 by a first control line 126. The EHSV 124 is connected in fluid communication with both the inlet line 104, by way of the recirculation line 116, and with the outlet line 106 through respective connection lines 128, 130. The EHSV 124 is operatively connected to the controller 120 for active control of the EHSV 124 to actuate the BPV 110.
A first position sensor 132, such as a linear variable differential transformer (LVDT), is operatively connected to the BPV 110 to provide sensor output indicative of position of a valve member 134 of the BPV 110 within the BPV 110. The first position sensor 132 is operatively connect the controller 120 to provide feedback for controlling the BPV 110. A second position sensor 144, such as an LVDT, is operatively connected to the variable displacement mechanism 108 to provide sensor output indicative of position of the variable displacement mechanism 108, wherein the second position sensor 144 is operatively connect the controller 120 to provide feedback for controlling the variable displacement mechanism 108.
The controller 120 is operatively connected to receive input indicative of flow demanded by the downstream system 122, as indicated by the arrow and label in
BF=PF−DSFD
wherein BF is flow through the BPV 110, PF is flow through the VDP 102 (e.g. as indicated by sensors 144 and/or a pressure sensor elsewhere in the system or incorporated in sensor 146), and DSFD is flow demanded by the downstream system 122.
In the first condition, e.g. when flow demanded by the downstream system 122 is at or above the predetermined low threshold for flow through the VDP 112, the controller 120 controls the BPV 110 to recirculate flow from the outlet line 106 to the inlet line 102 at a constant base recirculation rate. The base recirculation rate can be zero recirculation flow.
Systems and methods as disclosed herein provide potential benefits including the following. Utilizing a variable displacement pump with direct pump displacement control via an EMA and a temperature feedback loop in the controller, a maximum temperature threshold at any given set of operating conditions can be actively maintained. This will allow the minimum displacement of the pump to be actively varied as the operating conditions dictate. Allowing for the absolute tolerable minimum displacement as a function of temperature will allow the pump to have the minimum parasitic horsepower loss while being able to maintain non-detrimental temperature rise, therefor favorable fluid properties to ensure the mechanical health of the pump.
The methods and systems of the present disclosure, as described above and shown in the drawings, provide for temperature based control of variable displacement pumps, such as for use in supplying fuel to gas generators in aircraft engines. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.
