AU2018211336A1 - Air Compressor Control System - Google Patents

Abstract

Abstract In one aspect, an air compressor controller 12 is disclosed. In at least one embodiment, the air compressor controller 12 is operable for controlling an air compressor 24 powered by an engine. The air compressor 24 has an air inlet 102 which regulates the volume of air consumed by the compressor and an outlet 106 connected to a reservoir for supply of compressed air from the reservoir. The controller 12 comprises a receiver of desired compressed air output pressure, a receiver of desired compressed air volume consumption, a receiver of reservoir pressure, a receiver of an indication of engine power output, a processor for determining an output based on the received desired output pressure, the received desired volume consumption, the received reservoir pressure, and the indication of engine power output. The output comprises a control signal for controlling the position of the inlet valve into the air compressor. -2/2 X'wn -g D 4160 /t'ad (ic<) (4~0?Ot e er1 S) 6""" A//rsk164 / e.1%tW/ac 62 6en ,A62 O'~' a tod170 /rr\c176 > Controller BDV Actuator Delivery Valve BD Valve Open / Closed Fig. 3

Description

Air Compressor Control System

Field of the Invention [0001] The present invention relates to a control system for an air compressor.

Background [0002] Compressed air consuming equipment, such as a drill string of a drill rig, can consume the vast majority of power available from an engine powering an air compressor that provides compressed air to the equipment. Accordingly, when scoping the required engine capacity for the equipment, the maximum load on the engine is taken into account. This becomes more complicated when the engine is tasked with powering other equipment, such as electrical equipment, via a generator, and hydraulic equipment, via a hydraulic liquid pump.

[0003] Even though all of these demands may not be required at once, some design principles suggest that the worst case be taken into account and the engine be sized to accommodate all of these demands as if they were required at once. The result is that a larger engine capacity is specified. Larger capacity engines are generally larger in size, heavier and consume more fuel. These factors can be limiting when the engine and other equipment must be portable.

[0004] A typical air compressor control system directly controls an air inlet valve which regulates air intake into the air compressor. The air compressor produces compressed air in volumes according to the position of the air intake valve and the required pressure. With little or no demand, a running blowdown valve vents air to the atmosphere so as to maintain a minimum airflow.

[0005] The present invention seeks to provide an alternative air compressor control system. In some, but not necessarily all circumstances, this air compressor control system could potentially enable a smaller capacity engine to be selected to power the air compressor and other engine power consuming equipment.

Summary of the Present Invention [0006] According to the present invention there is provided an air compressor controller for controlling an air compressor powered by an engine, the compressor having an air inlet

2018211336 03 Aug 2018 which regulates the volume of air consumed by the compressor and an outlet connected to a reservoir for supply of compressed air from the reservoir, the controller comprising: a receiver of desired compressed air output pressure;

a receiver of desired compressed air volume consumption;

a receiver of reservoir pressure;

a receiver of an indication of engine power output;

a processor for determining an output based on the received desired output pressure, the received desired volume consumption, the received reservoir pressure and the indication of engine power output; wherein the output comprises a control signal for controlling the position of the inlet valve into the air compressor.

[0007] In an embodiment, the controller further comprises a receiver of a position of an inlet valve; and the processor determines the output also based on the received inlet valve position. In an alternative, the processor outputs the required position of the inlet valve based on intrinsic recording of the current inlet valve position.

[0008] In an embodiment, the controller further comprises a receiver of a position of an outlet valve from the reservoir.

[0009] In an embodiment, the output further comprises a position of a running blowdown valve from the reservoir.

[0010] In an embodiment, the running blowdown valve position is controllable to be open or closed.

[0011] In an embodiment, the processor is configured to only open the running blowdown valve when there is low or no demand on the reservoir pressure. In an embodiment the processor is configured to determine that there is no demand on the reservoir pressure based on the position of the outlet valve. In an embodiment low demand is less than 20% of the maximum pressure output from the reservoir or from the compressor, alternatively 15%, alternative 10%, alternatively 5%.

[0012] In an embodiment, the engine output is provided to the air compressor and to one or more other power demanding systems. In an embodiment, the maximum engine output is less than the potential combined demand from the air compressor and other power demanding systems.

2018211336 03 Aug 2018 [0013] In an embodiment, the processor is configured so that the position of the input valve is controlled such that air input to the compressor is reduced as engine load approaches maximum power output.

[0014] In an embodiment, the processor is configured to control the input valve according to a configuration setting. In an embodiment the control of the input valve is according to one of a plurality of configuration settings.

[0015] According to the present invention there is provided an apparatus comprising a compressed air demanding item of equipment; an engine; an air compressor powered by the engine; an air inlet which regulates the volume of air consumed by the compressor; a reservoir connected to an output of the air compressor, wherein the reservoir is for supply of compressed air to the item of equipment; and a controller for controlling the air compressor, wherein the controller comprises:

a receiver of desired compressed air output pressure;

a receiver of desired compressed air volume consumption;

a receiver of reservoir pressure;

a receiver of an indication of engine power output;

a processor for determining an output based on the received desired output pressure, the received desired volume consumption, the received reservoir pressure and the indication of engine power output; wherein the output comprises a control signal for controlling the position of the inlet valve into the air compressor.

[0016] According to the present invention there is provided a method of controlling an air compressor powered by an engine, the compressor having an air inlet which regulates the volume of air consumed by the compressor and an outlet connected to a reservoir for supply of compressed air from the reservoir, the method comprising:

receiving a desired compressed air output pressure;

receiving a desired compressed air volume consumption;

receiving a signal representing reservoir pressure;

receiving a signal representing engine power output processing the received desired output pressure, the received desired volume consumption, the received reservoir pressure, the current inlet valve position and the engine power output so as to determine a desired position of the inlet valve into the air compressor.

[0017] In an embodiment, the method further comprises receiving the current position of the inlet valve.

2018211336 03 Aug 2018 [0018] In an alternative embodiment, the method further comprises intrinsically recording the inlet valve position.

[0019] In an embodiment, the method further comprises computing a required position of a running blowdown valve from the reservoir.

[0020] In an embodiment, the computed position of the running blowdown valve is for the running blowdown valve to be closed unless there is no demand on the reservoir pressure.

[0021] In an embodiment, the method further comprises receiving an indication of engine power output.

[0022] In an embodiment, the method further comprises receiving an indication of the position of an outlet valve from the reservoir.

[0023] In an embodiment, the demand on the reservoir pressure is determined based on the indication of the outlet valve.

[0024] In an embodiment, the processing step determines the desired position of the inlet valve based on the received indication of engine power output.

[0025] In an embodiment, the processing step determines the desired position of the inlet valve so that air input to the compressor is reduced as engine load approaches maximum power output.

[0026] In an embodiment, the processing step determines the desired position of the inlet valve according to a configuration setting.

[0027] According to the present invention there is provided a method of controlling an air compressor powered by an engine, the compressor having an air inlet which regulates the volume of air consumed by the compressor, an outlet connected to a reservoir for supply of compressed air from the reservoir, the method comprising:

receiving a signal representing an outlet valve position;

2018211336 03 Aug 2018 receiving a signal representing reservoir pressure;

processing the received signal representing an outlet valve position and the received reservoir pressure so as to determine a position of a running blowdown valve from the reservoir.

[0028] In an embodiment, the determined position of the running blowdown valve is closed unless there is low or no demand on the reservoir pressure. In an embodiment low demand is less than 20% of the maximum pressure output from the reservoir or from the compressor, alternatively 15%, alternative 10%, alternatively 5%.

[0029] In an embodiment, the method further comprises receiving a signal representing a desired pressure in the reservoir, and the processing step further comprises determining the position of the running blowdown valve based on the position of the desired pressure in the reservoir.

[0030] According to the present invention there is provided a controller for controlling an air compressor powered by an engine, the compressor having an air inlet which regulates the volume of air consumed by the compressor, an outlet connected to a reservoir for supply of compressed air from the reservoir and a running blowdown valve from the reservoir, the controller comprising:

a receiver of a signal representing an outlet valve position;

a receiver of a signal representing reservoir pressure;

a processor for determining a position of the running blowdown valve from the reservoir based on the outlet valve position and the reservoir pressure.

[0031] In this specification the terms “having”, “comprising” or “comprises” are used inclusively and not exclusively or exhaustively.

Description of Drawings of the Invention [0032] In order to provide a better understanding of the present invention, preferred embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

[0033] Figure 1 is a schematic block diagram of an air compressor control system according to an embodiment of the present invention;

2018211336 03 Aug 2018 [0034] Figure 2 is a schematic block diagram of a controller of the control system of Figure

1; and [0035] Figure 3 is a schematic block diagram of logical controller elements of the controller of Figure 2.

Description of Embodiments of the Invention [0036] Referring to Figure 1, there is shown one embodiment of an air compressor system 10 comprising an air compressor 24 powered by an engine (not shown) and a controller 12 for controlling the system 10. In this embodiment, the air compressor 24 is a rotary screw air compressor. The compressor 24 receives a rotational force 104 from the engine. The compressor 24 has an air inlet 102 which receives air regulated by an inlet valve 26. The inlet valve 26 has an air intake 100. The compressor 24 has an outlet 106 connected to a reservoir 20. In this embodiment, the air compressor 24 is oil lubricated and the reservoir 20 is also an oil sump. The reservoir 20 has a compressed air outlet 108 which leads to a valve 36 and then supplies compressed air to equipment, such as a drill string when the air compressor 24 is installed for use on a drilling rig. An outlet valve position signal line 88 connects a sensor of the valve position to the controller 12.

[0037] The sump 20 also has a running blowdown valve 30 for venting air to the atmosphere by an outlet 32. Typically, the supply of compressed air to the equipment would be controlled by controlling the inlet valve 26 and/or the outlet valve 36 to supply compressed air at a desired pressure and a desired volume (rate) from the reservoir 20. The desired pressure and desired volume (also referred to as desired consumption) are user inputs 40 received by a control panel 80. The control panel 80 provides the desired pressure and desired volume as respective signals 42 and 44 to the controller 12.

[0038] The controller 12 of the present invention by-passes the normal control of the inlet valve 26, and in some embodiments, also controls the running blowdown valve 30 in response to: the user inputs 40 and feedback inputs 16. The feedback inputs 16 comprise the actual pressure in the reservoir 20; the position of the inlet valve 26; and preferably an engine load signal 86, which can be provided by an engine control unit (ECU), via engine load line 86 from the ECU to the controller 12.

2018211336 03 Aug 2018 [0039] The inlet valve 26 comprises an inlet actuator 22 that controls the position of the inlet valve 26 and an actuator controller 18 that provides a control signal to the inlet actuator 22. The inlet actuator 22 also comprises a sensor 28 for detecting the inlet valve’s position. A control line 90 connects the controller 12 to the actuator controller 18. An inlet valve signal line 82 connects the sensor 28 to the controller 12. In an embodiment, the inlet value 26 comprises a failsafe shut off.

[0040] The normal running blowdown valve is modified or replaced with a controllable position valve, that is able to be opened or shut as determined by the controller 12. A control line 92 connects the controller 12 to the actuator of the controllable blowdown valve 30 so as to control it to be open or shut when required by the controller 12.

[0041] The reservoir 20 comprises a pressure sensor 34 for reading the current air pressure inside of the reservoir 20. A reservoir pressure signal line 84 connects the pressure sensor 34 to the controller 12.

[0042] Referring to Figure 2, the controller 12 comprises a first processor in the form of a logic controller 60 configured to receive the desired volume signal 44 and an engine load signal 52 received on the engine load line 86, and produces an output of an allowable volume signal 62. The volume signal 62 is provided to a second processor in the form of a logic controller 64 configured to also receive the desired pressure signal 42, a signal 54 representing the inlet valve position from the signal line 82, a signal 56 representing the sump pressure from the signal line 84, and a signal 58 representing the outlet value 36 position from the signal line 88. From these inputs, the second processor 64 determines an output of a signal 72 representing the inlet valve position on control line 90 and a signal 74 representing the blowdown valve position on control line 92, thereby controlling the inlet valve positon and the blowdown valve position.

[0043] The allowable volume signal places a limit on the volume that can be provided to the output 108 and thus the equipment (for example drill string) even though more volume may be desired via the desired volume signal 44. The limitation is based on the current engine load. This is particularly useful when the engine has other demands beside the compressor 24 as it can reserve capacity for those other loads, or it can accommodate varying load priorities. This is also useful to limit engine fuel consumption and prolong engine life by restricting the engine from running at full capacity.

2018211336 03 Aug 2018 [0044] In the embodiment shown, the processor 64 is configured to only open the running blowdown valve 30 when there is no demand on the reservoir pressure. The required blowdown valve 30 position can be determined by knowing whether valve 36 is open or closed, and reservoir pressure. The blowdown valve 30 will be open if the reservoir 20 is at the desired pressure and valve 36 closed. The blowdown valve 30 will be closed if:

- reservoir 20 is at the desired pressure and valve 36 is open or

- reservoir 20 is below the desired pressure and valve 36 is open; or

- reservoir 20 is below the desired pressure and valve 36 is closed.

[0045] In one embodiment, the second processor 64 preferably also takes into account the desired reservoir pressure 40. The second processor 64 will open the blowdown valve 30 when the reservoir pressure is a set amount (such as 1 bar) less than the input desired pressure. The valve 30 will remain open when the reservoir pressure is more than the desired reservoir pressure. When the reservoir pressure drops below the set amount the blowdown valve 30 will be closed according to the above rules.

[0046] The present invention may allow for the selection of an engine on a piece of equipment, such as a drill rig, to be of a smaller capacity than would be currently selected. Typically, all of the engine power demands would be summed (as a worst case engine demand scenario) and this used to determine the required engine capacity. Thus in the present invention, the maximum engine output can be less than the potential demand from the air compressor 24 and all of the other power demanding systems.

[0047] In an embodiment, the first processor 60 is configured so that the allowable volume, and thus the position of the input valve 26 is controlled, such that air input to the compressor 24 is reduced as engine load approaches a selected maximum power output.

[0048] In an embodiment, the first processor 60 is configured to control the input valve 26 according to a selected configuration setting. In an embodiment one of the configuration settings is a normal operation setting, such that the air input to the compressor 24 is limited to achieve a maximum of about 70-80%, and preferably about 75%, of maximum engine load. In an embodiment one of the configuration settings is an override setting, such that the air input to the compressor is limited to achieve a maximum of about 90-98%, and preferably about 95%, of maximum engine output load.

2018211336 03 Aug 2018 [0049] In an embodiment the second processor 64 is also configured to implement a proportional-integral-derivative control system on the position of the inlet control valve position.

[0050] Referring to Figure 3, an embodiment of the controller 12 implements a cascaded PID control method, where multiple layers of PID’s control the intake valve position to load/unload the compressor, whilst maintaining a desired maximum engine load.

[0051] In this embodiment the logic controller 60 comprises a PID controller 160 which receives the current engine load signal 86, the desired volume 44 and a desired engine load setting 120. The setting 120 allows the user to select how much the engine can be used. For example, the selection may be such that there is an economy mode that limits engine loading to 70%, a normal operation mode that limits engine loading to 80%, and an override mode that allow engine load to reach 95%. These are merely examples.

[0052] The controller 160 determines and outputs the maximum allowable volume signal 62 which is provided as an input to another PID controller 170 which also receives the current reservoir pressure 84 and the desired pressure 40. Controller 170 determines and outputs the required intake valve position signal 176. Signal 176 is provided as an input to another PID controller 172 which also receives the current intake valve position 82. Controller 172 determines and outputs the signal 72 to the valve actuator 22 so that the intake valve 26 is adjusted to the required position.

[0053] In an embodiment, PID controller 170 has a varying gain value for the Integral term based on an equation. The equation has the controller 170 compute an error between the current and desired pressure and then determines a high gain in a range below the set pressure, a nominal gain near the set pressure and a higher gain when the pressure overshoots the set pressure. This provides an improved response that better matches the real-life response of the compressor system.

[0054] Other forms of control that may be suited are: proportional / linear control, or fuzzy logic control.

[0055] The controller 64 may be implemented as controllers 170 and 172. Controller 64 may also implement a further controller element 174 for controlling the blowdown valve 30. Controller 174 receives the position of the delivery valve signal 58, the signal representing

2018211336 03 Aug 2018 the current reservoir pressure 84, and preferably the desired reservoir pressure 40. These inputs are applied to logic (as noted above) to determine whether the blowdown valve actuator signal 74 should open or close the blowdown valve 30.

[0056] Modifications may be made to the present invention within the context of that described and shown in the drawings. Such modifications are intended to form part of the invention described in this specification.

[0057] An example modification is for the second processor 64 to intrinsically record the current inlet valve position and to determine the required inlet valve position based on the intrinsic position record. In that case, the feedback from the inlet valve would not be required.

Claims (29)

1. An air compressor controller for controlling an air compressor powered by an engine, the compressor having an air inlet which regulates the volume of air consumed by the compressor and an outlet connected to a reservoir for supply of compressed air from the reservoir, the controller comprising:

a receiver of desired compressed air output pressure; a receiver of desired compressed air volume consumption; a receiver of reservoir pressure;

a receiver of an indication of engine power output;

a processor for determining an output based on the received desired output pressure, the received desired volume consumption, the received reservoir pressure and the indication of engine power output;

wherein the output comprises a control signal for controlling the position of the inlet valve into the air compressor.

2. An air compressor controller according to claim 1, wherein the controller further comprises a receiver of a position of an inlet valve; and the processor determines the output also based on the received inlet valve position.

3. An air compressor controller according to claim 2, wherein the processor outputs the required position of the inlet valve based on intrinsic recording of the current inlet valve position.

4. An air compressor controller according to any one of the preceding claims, wherein the controller further comprises a receiver of a position of an outlet valve from the reservoir.

5. An air compressor controller according to any one of the preceding claims, wherein the output further comprises a position of a running blowdown valve from the reservoir.

6. An air compressor controller according to claim 5, wherein the running blowdown valve position is controllable to be open or closed.

2018211336 03 Aug 2018

7. An air compressor controller according to claim 5 or claim 6, wherein the processor is configured to only open the running blowdown valve when there is low or no demand on the reservoir pressure.

8. An air compressor controller according to any one of the preceding claims when dependent on claim 4, wherein the processor is configured to determine that there is low or no demand on the reservoir pressure based on the position of the outlet valve.

9. An air compressor controller according to any one of the preceding claims, wherein the engine output is provided to the air compressor and to one or more other power demanding systems.

10. An air compressor controller according to claim 9, wherein the maximum engine output is less than the potential combined demand from the air compressor and other power demanding systems.

11. An air compressor controller according to any one of the preceding claims, wherein the processor is configured so that the position of the input valve is controlled such that air input to the compressor is reduced as engine load approaches maximum power output.

12. An air compressor controller according to any one of the preceding claims, wherein the processor is configured to control the input valve according to a configuration setting.

13. An air compressor controller according to claim 12, wherein the control of the input valve is according to one of a plurality of configuration settings.

14. An apparatus comprising a compressed air demanding item of equipment; an engine; an air compressor powered by the engine; an air inlet which regulates the volume of air consumed by the compressor; a reservoir connected to an output of the air compressor, wherein the reservoir is for supply of compressed air to the item of equipment; and a controller for controlling the air compressor, wherein the controller comprises:

a receiver of desired compressed air output pressure; a receiver of desired compressed air volume consumption; a receiver of reservoir pressure;

2018211336 03 Aug 2018 a receiver of an indication of engine power output;

a processor for determining an output based on the received desired output pressure, the received desired volume consumption, the received reservoir pressure and the indication of engine power output; wherein the output comprises a control signal for controlling the position of the inlet valve into the air compressor.

15. A method of controlling an air compressor powered by an engine, the compressor having an air inlet which regulates the volume of air consumed by the compressor and an outlet connected to a reservoir for supply of compressed air from the reservoir, the method comprising:

receiving a desired compressed air output pressure; receiving a desired compressed air volume consumption; receiving a signal representing reservoir pressure; receiving a signal representing engine power output processing the received desired output pressure, the received desired volume consumption, the received reservoir pressure, the current inlet valve position and the engine power output so as to determine a desired position of the inlet valve into the air compressor.

16. A method according to claim 15, wherein the method further comprises receiving the current position of the inlet valve.

17. A method according to claim 15 or claim 16, wherein the method further comprises intrinsically recording the inlet valve position.

18. A method according to any one of claims 15 to 17, wherein the method further comprises computing a required position of a running blowdown valve from the reservoir.

19. A method according to claim 18, wherein the computed position of the running blowdown valve is for the running blowdown valve to be closed unless there is no demand on the reservoir pressure.

20. A method according to any one of claims 15 to 19, wherein the method further comprises receiving an indication of engine power output.

2018211336 03 Aug 2018

21. A method according to any one of claims 15 to 20, wherein the method further comprises receiving an indication of the position of an outlet valve from the reservoir.

22. A method according to claim 21, wherein the demand on the reservoir pressure is determined based on the indication of the outlet valve.

23. A method according to any one of claims 15 to 22 when dependent on claim 20, wherein the processing step determines the desired position of the inlet valve based on the received indication of engine power output.

24. A method according to any one of claims 15 to 23, wherein the processing step determines the desired position of the inlet valve so that air input to the compressor is reduced as engine load approaches maximum power output.

25. A method according to any one of claims 15 to 24, wherein the processing step determines the desired position of the inlet valve according to a configuration setting.

26. A method of controlling an air compressor powered by an engine, the compressor having an air inlet which regulates the volume of air consumed by the compressor, an outlet connected to a reservoir for supply of compressed air from the reservoir, the method comprising:

receiving a signal representing an outlet valve position; receiving a signal representing reservoir pressure;

processing the received signal representing an outlet valve position and the received reservoir pressure so as to determine a position of a running blowdown valve from the reservoir.

27. A method according to claim 26, wherein the determined position of the running blowdown valve is closed unless there is low or no demand on the reservoir pressure.

28. A method according to claim 26 or claim 27, wherein the method further comprises receiving a signal representing a desired pressure in the reservoir, and the processing step further comprises determining the position of the running blowdown valve based on the position of the desired pressure in the reservoir.

29. A controller for controlling an air compressor powered by an engine, the compressor having an air inlet which regulates the volume of air consumed by the compressor, an outlet connected to a reservoir for supply of compressed air from the reservoir and a running blowdown valve from the reservoir, the controller comprising:

a receiver of a signal representing an outlet valve position; a receiver of a signal representing reservoir pressure;

a processor for determining a position of the running blowdown valve from the reservoir based on the outlet valve position and the reservoir pressure.