Method and system for operating a compressor for a prime mover

Abstract

A method of operating prime mover compressors comprising: Receiving sensor data at a controller (12); and Activating, via the controller (12), a second compressor in an engine intake (171) based on the sensor data in response to a first compressor being within a threshold airflow of a surge condition, wherein the second compressor is activated from a deactivated state, and further comprising adjusting a speed of the second compressor to provide a pressure at an output of the second compressor that is 180 degrees out of phase with a pressure at an output of the first compressor.

Description

Background / Summary

[0001] A turbocharger can compress the air supplied to an engine to improve engine power. The speed of a turbocharger can be controlled via a wastegate. The wastegate can be selectively opened and closed to regulate compressor speed. However, a turbocharger compressor can be prone to oscillation if a large change in flow through the compressor occurs. For example, a compressor may begin to oscillate if a driver at least partially releases an accelerator pedal from a higher driver demand to a lower driver demand. Rapidly closing the throttle can cause the air flow through the compressor to decrease, causing the compressor to begin oscillating.One way to reduce the possibility of compressor oscillation is to install a compressor bypass valve, which allows air to return from the compressor outlet to the compressor inlet. However, the energy applied to pressurize the air is lost and irrecoverable when the compressor bypass valve is open. Furthermore, if the driver applies the accelerator pedal after the air pressure downstream of the compressor has decreased, the turbocharger may be unable to provide a desired engine airflow. Consequently, the driver may experience "turbo lag" (e.g., a delay in engine torque production due at least in part to lower-than-desired airflow through the turbocharger) until the airflow through the turbocharger is sufficient to provide the desired engine airflow.Therefore, it may be desirable to provide a way to reduce compressor vibration while not releasing boost pressure or contributing to the possibility of turbo lag.

[0002] Methods for operating engine compressors comprising a first compressor and a second compressor in an engine inlet are known, for example from US 2009 / 0 107 140 A1, DE 20 2013 103 691 U1 and DE 10 2013 108 607 A1.

[0003] The inventors herein have recognized the above-mentioned disadvantages and have developed a method for operating engine compressors, comprising: receiving sensor data at a controller; and activating, via the controller, a second compressor in an engine intake based on the sensor data in response to a first compressor being within a threshold airflow of a surge condition.

[0004] By activating a second compressor in an engine air intake passage, it may be possible to provide the technical result of adjusting the air pressure in the engine air intake upstream of the first compressor, so that the possibility of speed oscillations of the first compressor may be reduced. In one example, airflow through the second compressor is adjusted in response to an increase in pressure at an outlet of the first compressor to reduce the pressure at an outlet of the second compressor. In this way, the boost pressure generated by the first compressor may be preserved, so that if a driver increases a requested torque, the air may be available to increase engine power with little or no turbo lag.

[0005] The present description may provide several advantages. For example, the approach may preserve the boost pressure provided by a turbocharger. Furthermore, the approach may improve engine air-fuel ratio control by reducing pressure oscillations in the engine's intake port. Even further, the approach may provide rapid access to boost pressure after a driver reduces driver-requested torque.

[0006] The above advantages and other advantages and features of the present description will be readily apparent from the following detailed description when considered alone or in conjunction with the accompanying drawings.

[0007] It should be understood that the above summary is provided to introduce, in simplified form, a selection of the concepts further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is clearly defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that eliminate all of the disadvantages noted above or in any part of this disclosure. Brief description of the drawings Fig. 1 shows a schematic representation of a power machine; Fig. 2 is a diagram illustrating an air flow of the engine according to the present description; Fig. 3 shows an exemplary engine operating sequence for reducing the possibility of compressor surge; and Fig. Figure 4 shows an exemplary method for reducing the possibility of compressor surge. Detailed description

[0008] This description relates to the operation of an engine containing a turbocharger compressor. The turbocharger compressor may experience speed oscillations if subjected to specific pressure and flow conditions. Fig. Figure 1 shows an exemplary engine that includes two compressors. The pressure oscillations in the air intake of the engine can be reduced by operating an electrically driven compressor in a Fig. 2. An exemplary engine operating sequence for controlling the pressure and flow within an air intake of the engine is shown in Fig. 3. A method for operating an engine and reducing the possibility of compressor surge is shown in Fig. 4 shown.

[0009] In Fig. 1 is an internal combustion engine 10 comprising several cylinders, one of which is in Fig. 1, is controlled by an electronic engine controller 12. The engine 10 includes a combustion chamber 30 and cylinder walls 32, with a piston 36 positioned therein and connected to a crankshaft 40. The combustion chamber 30 is shown communicating with an intake manifold 44 and an exhaust manifold 48, respectively, via an intake valve 52 and an exhaust valve 54. Each intake and exhaust valve may be actuated by an intake cam 51 and an exhaust cam 53. The position of the intake cam 51 may be determined by an intake cam sensor 55. The position of the exhaust cam 53 may be determined by an exhaust cam sensor 57.

[0010] A fuel injector 66 is shown positioned to inject fuel directly into the cylinder 30, known to those skilled in the art as direct injection. Alternatively, the fuel may be injected into an intake port, known to those skilled in the art as port injection. The fuel injector 66 delivers liquid fuel proportional to a pulse width provided by the controller 12. The fuel is delivered to the fuel injector 66 by a fuel system including a fuel tank (not shown), a fuel pump (not shown), and a fuel rail (not shown). Additionally, the intake manifold 44 is shown in communication with an optional electronic throttle 62 that adjusts a position of a throttle plate 64 to control airflow from an intake boost chamber 46.

[0011] Compressor 162 draws air from the engine's air intake 42 to supply it to boost chamber 46. The exhaust gases rotate turbine 164, which is coupled to compressor 162 via shaft 161. A bypass valve 175 of the exhaust-driven compressor can be electrically operated via a signal from controller 12. Compressor bypass valve 175 allows pressurized air to circulate back to the compressor inlet to limit boost pressure. Similarly, a wastegate actuator 72 allows exhaust gases to bypass turbine 164 so that boost pressure can be controlled under varying operating conditions.

[0012] The electrically driven compressor 150 can be selectively activated via the controller 12. Electrical energy from electrical energy storage devices and / or an alternator (not shown) supplies energy to rotate the electrically driven compressor 150. An electrically driven compressor bypass passage 37 includes an electrically driven compressor bypass valve 153 that can be selectively opened to allow air from the compressor 162 to flow through a charge air cooler 151 and to the boost chamber 46 without passing through the electrically driven compressor 150. The charge air cooler 151 cools the air entering an engine air intake 171. The charge air cooler 151 can be an air-to-air cooler or a liquid-to-air cooler.

[0013] A distributorless ignition system 88 provides an ignition spark to the combustion chamber 30 via a spark plug 92 in response to the controller 12. A universal exhaust gas oxygen (UEGO) sensor 126 is shown coupled to the exhaust manifold 48 upstream of a catalytic converter 70. Alternatively, the UEGO sensor 126 may be replaced with a dual-state exhaust gas oxygen sensor.

[0014] In one example, the catalyst 70 may include multiple catalyst modules. In another example, multiple emission control devices, each with multiple modules, may be used. In one example, the catalyst 70 may be a three-way catalyst.

[0015] The controller 12 is in Fig. 1 as a conventional microcomputer including a microprocessor unit 102, input / output ports 104, (non-volatile) read-only memory 106, random access memory 108, latch 110, and a conventional data bus. Controller 12 is shown receiving, in addition to those signals previously discussed, various signals from sensors coupled to engine 10, including: engine coolant temperature (ECT) from temperature sensor 112 coupled to cooling sleeve 114; position sensor 134 coupled to accelerator pedal 130 for sensing an accelerator pedal position set by foot 132; ambient air humidity from humidity sensor 19; a measurement of engine manifold pressure (MAP) from a pressure sensor 121 coupled to intake manifold 44;a measurement of boost pressure or throttle inlet pressure from a pressure sensor 122 coupled to the boost chamber 46 or, alternatively, upstream of the electrically driven compressor 150; an engine position sensor from a Hall-effect sensor 118 that senses the position of the crankshaft 40; a measurement of an air mass entering the engine from a sensor 120 (e.g., a hot-wire airflow meter); and a measurement of throttle position from a sensor 58. The engine position sensor 118 generates a predetermined number of equally spaced pulses with each revolution of the crankshaft, from which the engine speed (RPM) can be determined.

[0016] In some examples, the engine may be coupled to an electric motor / battery system in a hybrid vehicle. The hybrid vehicle may have a parallel configuration, a series configuration, or a variation or combination thereof. Further, in some examples, other engine configurations may be used, such as a diesel engine.

[0017] During operation, each cylinder in the engine 10 typically undergoes a four-stroke cycle: the cycle includes the intake stroke, the compression stroke, the power stroke, and the exhaust stroke. Generally, during the intake stroke, the exhaust valve 54 is closed and the intake valve 52 is open. Air is introduced into the combustion chamber 30 via the intake manifold 44, and the piston 36 moves toward the bottom of the cylinder to increase the volume in the combustion chamber 30. The position where the piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber 30 is at its largest volume) is typically referred to by those skilled in the art as bottom dead center (BDC). During the compression stroke, the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves toward the cylinder head to compress the air in the combustion chamber 30.The point at which piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when combustion chamber 30 is at its smallest volume) is typically referred to by those skilled in the art as top dead center (TDC). In a process referred to herein as injection, fuel is introduced into the combustion chamber. In a process referred to herein as ignition, the injected fuel is ignited by known ignition means, such as spark plug 92, resulting in combustion. During the power stroke, expanding gases push piston 36 back to BDC. Crankshaft 40 translates piston motion into rotating shaft torque. Finally, during the exhaust stroke, exhaust valve 54 is open to expel the combusted air-fuel mixture to exhaust manifold 48, returning the piston to TDC.It should be noted that the above has been described merely as an example and that the opening and / or closing times of the intake and exhaust valves may change, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples.

[0018] Air flows from the engine's air intake 42 through the engine, past the compressor 162, the charge air cooler 151, the electrically driven compressor 150, and the throttle valve 62, before entering the engine's intake manifold 44. The air enters the combustion chamber 30 from the engine's intake manifold 44 before passing as combustion byproducts or air to the exhaust manifold 48. The air and / or combustion byproducts are then released to the atmosphere after passing the turbine 164 and passing through the catalyst 70. Thus, the engine's air intake 42 is located upstream of the compressor 162, the charge air cooler 151, the electrically driven compressor 150, and the combustion chamber 30, according to a direction of airflow through the engine 10.

[0019] In Fig. 2 is a schematic illustrating engine airflow according to one aspect of the present description. Fig. 2 shows an air flow in the engine components, which in Fig. 1. The Fig. 2, which have the same reference numerals as in Fig. 1 are the same elements shown in Fig. 1. Furthermore, the elements operate in the same manner. Therefore, for the sake of brevity, a description of these elements is omitted.

[0020] During engine operating conditions when turbo lag may be present, valve 153 may be closed, allowing air to flow from compressor 162 to electrically driven compressor 150 before passing through electronic throttle 62. Air flows through engine intake 171 in the direction shown by arrows 201 when valve 153 is closed. Valve 153 may be open and electrically driven compressor 150 may be deactivated when compressor 162 can provide airflow at or greater than a desired engine airflow. Air flows through engine intake 171 in the direction shown by arrows 205 when valve 153 is open and the electrically driven compressor is deactivated.Air flow may occur in a direction opposite to that shown by arrows 205 when electrically driven compressor 150 is active and valve 153 is open. The air flows into engine 10, as shown by arrow 210. Air may flow into engine 10 when valve 153 is open or closed.

[0021] The speed of the electrically driven compressor 150 can be varied to increase or decrease the pressure in the boost chamber 46 and to increase or decrease the pressure between the electrically driven compressor 150 and the charge air cooler 151. In particular, the pressure in the boost chamber 46 can be increased as the speed of the electrically driven compressor 150 is increased. The pressure between the electrically driven compressor 150 and the charge air cooler can decrease as the speed of the electrically driven compressor 150 is increased. Conversely, the pressure in the boost chamber 46 can decrease from a higher pressure as the speed of the electrically driven compressor 150 is decreased due to the engine consuming air. The pressure between the electrically driven compressor 150 and the charge air cooler can increase as the speed of the electrically driven compressor 150 is decreased.

[0022] Air flow may occur in a direction shown by arrow 207 when compressor bypass valve 175 is open. Bypass valve 175 may be opened when compressor 162 approaches surge conditions (e.g., operating at a low flow rate and a medium to high pressure ratio across compressor 162).

[0023] Consequently, the system provides the Fig. 1 and Fig. 2 provides an engine system comprising: an engine including an air intake; an exhaust-driven compressor positioned along the air intake and including a bypass valve; an electrically driven compressor positioned along the air intake downstream of the exhaust-driven compressor; and a controller including non-transitory instructions to, in response to a first indication of impending surge of the exhaust-driven compressor, open the bypass valve and, in response to a second indication of impending surge of the exhaust-driven compressor, activate the electrically driven compressor while closing the bypass valve.The indication of impending surge may be an increasing pressure ratio across the turbocharger compressor and / or a reduction in airflow through the compressor turbine, which moves the operation of the turbocharger compressor closer to a surge line of a compressor map stored in controller memory.

[0024] In some examples, the engine system includes where the first indication of impending surge occurs at a first flow of the turbocharger compressor that is less than a second flow of the turbocharger compressor where the second indication of impending surge occurs. The engine system further comprises additional non-transitory instructions to adjust airflow through the electrically driven compressor in response to the second indication of impending surge. The engine system includes where adjusting airflow through the electrically driven compressor includes commanding airflow through the electrically driven compressor based on pressure or airflow data provided via a sensor. The engine system includes where the second compressor is enabled from a deactivated state.The engine system includes that the first and second indications of impending surge are based on an expected speed oscillation of the exhaust-driven compressor.

[0025] In Fig. 3 shows a prophetic operating sequence of the engine. The operating sequence of the engine can be controlled by the system according to Fig. 1 in accordance with the procedure laid down in Fig. 4. The vertical lines shown at T0-T5 represent points of particular interest in the sequence. The graphical representations are aligned to time and occur simultaneously.

[0026] The first graphic representation from top to Fig. Figure 3 is a graph of engine airflow versus time. The vertical axis represents engine airflow, with engine airflow increasing in the direction of the vertical axis arrow. The horizontal axis represents time, with time increasing from the left side of the graph to the right side of the graph.

[0027] The second graphical representation from top to Fig. Figure 3 is a graph of the speed of the electrically driven compressor versus time. The vertical axis represents the speed of the electrically driven compressor, with the speed increasing in the direction of the vertical axis arrow. The horizontal axis represents time, with time increasing from the left side of the graph to the right side of the graph.

[0028] The third graphical representation from top to Fig. Figure 3 is a graph of the position of the turbocharger compressor bypass valve versus time. The turbocharger compressor bypass valve is open when the trace is at a higher level near the vertical axis arrow. The turbocharger bypass valve is closed when the trace is at a lower level near the horizontal axis. The horizontal axis represents time, with time increasing from the left side of the figure to the right side of the figure.

[0029] The fourth graphical representation from top to Fig. Figure 3 is a graph of the operating state of the electrically driven (EC) compressor bypass valve versus time. The vertical axis represents the operating state of the EC bypass valve. The EC bypass valve is open when the trace is at a higher level near the vertical axis arrow. The EC bypass valve is closed when the trace is at a lower level near the horizontal axis. The horizontal axis represents time, with time increasing from the left side of the figure to the right side of the figure.

[0030] The fifth graphic representation from top to Fig. Figure 3 is a graph of driver demand torque versus time. The vertical axis represents driver demand torque, with driver demand torque increasing in the direction of the vertical axis arrow. The horizontal axis represents time, with time increasing from the left side of the figure to the right side of the figure.

[0031] At time T0, engine airflow is at a higher level and the electrically driven compressor is deactivated. The turbocharger compressor bypass valve is closed and the electrically driven compressor bypass valve is open. Driver demand torque is at a higher level. Such conditions may indicate engine operation while an engine is propelling or accelerating at highway speeds.

[0032] At time T1, the driver reduces the driver-requested torque by at least partially releasing the accelerator pedal. Engine airflow is reduced in response to the reduction in driver-requested torque. The electrically driven compressor is activated, with its speed adjusted to provide a pressure in the engine intake system that is out of phase with the pressure generated via the turbocharger compressor. For example, the pressure output of the electrically driven compressor may increase as the pressure output of the turbocharger compressor decreases. By providing pressure to the electrically driven compressor that is out of phase with the pressure generated via the turbocharger compressor, it may be possible to reduce a magnitude of pressure oscillations near the engine throttle.The speed of the electrically driven compressor may be controlled in response to a pressure in the engine intake, an airflow in the engine air intake, or according to a control command stored in memory. In this example, the electrically driven compressor bypass valve is shown commanded open, but in other examples, the electrically driven compressor valve may be commanded closed when the electrically driven compressor is activated. Further, the electrically driven compressor may be activated in response to a change in engine airflow (e.g., a decrease) that is greater than a threshold.

[0033] Between time T1 and time T2, the driver-demanded torque is reduced to a value near zero, and the engine airflow is reduced to a lower level in response to the lower driver-demanded torque. The electrically driven compressor is deactivated in response to the pressure ratio across the turbocharger compressor and the flow rate through the turbocharger compressor, which are not indicative of the turbocharger compressor surge conditions. The turbocharger compressor bypass valve remains closed, while the electrically driven compressor bypass valve remains open.

[0034] At time T2, the driver-requested torque is increased, and the electrically driven compressor bypass valve is closed in response to the increase in driver-requested torque. The electrically driven compressor is also activated in response to the increase in driver-requested torque. Activating the electrically driven compressor may reduce engine torque lag resulting from turbo lag. Engine airflow also increases in response to the activation of the electrically driven compressor and the increase in driver-requested torque.

[0035] At time T3, the engine airflow and the flow through the turbocharger reach a desired engine airflow amount. Therefore, the electrically driven compressor is deactivated, opening the electrically driven compressor bypass valve. By opening the electrically driven compressor bypass valve and deactivating the electrically driven compressor, the engine airflow can be provided exclusively by the turbocharger compressor without assistance from the electrically driven compressor. In this way, the energy consumed to operate the engine can be reduced.

[0036] Between time T2 and time T4, the driver-requested torque and engine airflow remain near a medium level. The electrically driven compressor remains deactivated, with the turbocharger compressor bypass valve closed. The electrically driven compressor bypass remains open.

[0037] At time T4, the driver decreases the driver-requested torque by at least partially releasing the accelerator pedal. Engine airflow is decreased in response to the decrease in driver-requested torque. However, the decrease in driver demand is less than the level at time T1. Further, the change in engine airflow is less than the change in engine airflow at time T1. Therefore, the turbocharger compressor bypass valve is opened instead of activating the electrically driven compressor. Opening the turbocharger compressor bypass valve decreases the pressure ratio between an inlet and an outlet of the turbocharger compressor, thereby reducing the possibility of compressor surge. The electrically driven compressor bypass valve remains open, with the electrically driven compressor remaining deactivated.Furthermore, less electrical energy can be used to open the turbocharger compressor bypass valve than to activate the electrically driven compressor.

[0038] At time T5, the turbocharger compressor bypass valve closes in response to a lower pressure ratio across the turbocharger compressor and lower airflow through the turbocharger compressor. Engine airflow remains at a lower-medium level, with driver demand torque also at a lower-medium level. The electrically driven compressor bypass valve remains closed, with the electrically driven compressor deactivated.

[0039] In this way, the possibility of turbocharger compressor surge can be reduced. For larger changes in engine airflow, for example, the electrically driven compressor can be activated to adjust the pressure in the engine intake and reduce the possibility of turbocharger compressor surge. However, if the change in engine airflow is smaller, the turbocharger compressor bypass valve can be opened, thus consuming less electrical energy compared to activating the electrically driven compressor.

[0040] In Fig. 4, an exemplary method for operating a turbocharged engine including an electrically driven compressor is shown. At least portions of the method of Fig. 4 can be input as executable instructions stored in a non-volatile memory into the controller 12 in the system according to Fig. 1. Furthermore, the stages of the procedure according to Fig. 4 steps taken by the controller 12 in the physical world to transform the operating conditions of the vehicle. The method according to Fig. 4 can Fig. Provide the operating procedure shown in Figure 3.

[0041] At 402, method 400 determines the vehicle operating conditions, including, but not limited to, driver requested torque, throttle intake pressure, desired engine airflow, engine speed, ambient humidity, ambient air temperature, and intake air temperature, which are obtained via querying the Fig. 1. After the operating conditions have been determined, method 400 proceeds to 404.

[0042] At 404, method 400 assesses whether there is a decrease in driver-requested torque or a change in engine operating conditions that may move engine operating conditions into a range where turbocharger compressor surge may occur. In one example, method 400 may assess that the turbocharger compressor is approaching turbocharger compressor surge conditions based on a pressure ratio across the turbocharger compressor and airflow through the turbocharger compressor. For example, method 400 may assess that engine operating conditions indicate that the engine is approaching a surge line of a compressor map.If method 400 judges that there is a decrease in driver-requested torque that may cause turbocharger compressor surge, or if the turbocharger compressor is approaching turbocharger compressor surge conditions, the answer is yes and method 400 proceeds to 406. Otherwise, the answer is no and method 400 proceeds to 430.

[0043] At 406, method 400 judges whether or not to activate the electrically driven compressor or supercharger (ES). In one example, method 400 judges to activate the ES in response to a decrease in engine airflow greater than a first threshold. In other examples, method 400 may judge to activate the ES in response to the airflow through the turbocharger compressor and the pressure ratio across the turbocharger compressor being within a threshold flow and pressure ratio of a turbocharger compressor surge line. In still other examples, method 400 may activate the ES in response to a decrease in accelerator pedal position greater than a first threshold or other conditions. If method 400 judges to activate the ES, the answer is yes and method 400 proceeds to 408.Otherwise, the answer is no and method 400 proceeds to 420.

[0044] At 408, method 400 activates the electrically driven compressor or supercharger (ES) to provide boost pressure and dampen the pressure oscillations in the engine intake that may develop from the turbocharger compressor. In one example, the ES speed may be commanded to a control speed that is varied in response to the time period since activation. For example, a desired ES speed may be stored in memory indexed by the time since which a turbocharger surge condition is expected. The ES is commanded to the speed stored in memory. In other examples, the ES speed may be regulated in response to a pressure in the engine intake downstream of the turbocharger compressor (e.g., at the throttle inlet or upstream of the ES) or the airflow through the turbocharger compressor. The ES speed may, for example,increased in response to a decrease in engine inlet pressure to increase engine inlet pressure. Alternatively, ES speed may be decreased in response to an increase in engine inlet pressure to decrease engine inlet pressure. In this manner, the pressure output from the ES may be 180 degrees out of phase with the pressure generated by the turbocharger compressor so that engine inlet pressure changes may be reduced. Additionally, ES speed may be a function of the turbocharger compressor bypass position and the time since turbocharger surge conditions are determined or expected. For example, ifWhen the turbocharger bypass valve is partially open, the turbocharger speed value extracted from memory may be multiplied by a value based on the position of the turbocharger compressor bypass valve when the compressor bypass valve is partially open. The ES bypass valve may be open during a first condition and closed during a second condition when the ES speed is adjusted in response to engine intake pressure.

[0045] At 410, method 400 deactivates the electrically driven compressor in response to operating conditions that do not indicate engine intake pressure oscillations due to turbocharger compressor surge. In one example, the electrically driven compressor may be deactivated in response to the turbocharger compressor pressure ratio and airflow being greater than a threshold away from the turbocharger surge conditions or a surge line of a turbocharger compressor map. If the turbocharger compressor continues to operate near the turbocharger compressor surge conditions, method 400 continues to adjust the ES speed at 408. After the ES is deactivated, method 400 proceeds to exit.

[0046] At 420, method 400 judges whether or not to open the turbocharger compressor bypass valve. In one example, method 400 judges to open the turbocharger compressor bypass valve in response to a reduction in turbocharger compressor airflow greater than a second threshold, where the second threshold is less than the first threshold and greater than a third threshold. In other examples, method 400 may judge to open the turbocharger compressor bypass valve in response to the airflow through the turbocharger compressor and the pressure ratio across the turbocharger compressor being within a threshold flow and pressure ratio of a compressor surge line.In still other examples, method 400 may open the turbocharger compressor bypass valve in response to a decrease in accelerator pedal position greater than a second threshold, less than the first threshold in accelerator pedal position, or other conditions. If method 400 judges to open the turbocharger compressor bypass valve, the answer is yes and method 400 proceeds to 422. Otherwise, the answer is no and method 400 proceeds to 424.

[0047] At 422, method 400 opens the turbocharger compressor bypass valve. The turbocharger compressor valve may be held open until conditions indicate that the turbocharger is not operating near surge conditions. For example, method 400 may hold the turbocharger compressor valve open until the flow through the turbocharger compressor and the pressure ratio across the turbocharger compressor are a threshold away from conditions indicating compressor surge. By opening the turbocharger compressor bypass valve, the possibility of turbocharger compressor surge may be reduced by decreasing the pressure ratio across the turbocharger compressor and increasing airflow through the turbocharger compressor. After the turbocharger bypass valve is closed, method 400 proceeds to the exit.

[0048] At 424, method 400 closes the turbocharger compressor bypass valve. The turbocharger compressor bypass valve is closed to increase the efficiency of the turbocharger compressor so that it can increase airflow to the engine if desired. After the turbocharger compressor bypass valve is closed, method 400 proceeds to the exit.

[0049] At 430, method 400 judges whether or not turbo lag or turbocharger lag conditions are present. Turbo lag conditions may be present when the turbocharger compressor speed is lower than a threshold speed and when the driver-requested torque is higher than a threshold and / or increasing. The turbocharger may not be able to immediately increase engine airflow in response to the increase in driver-requested torque when the turbocharger compressor speed is low due to turbocharger inertia and engine airflow is lagging. If method 400 judges that turbo lag conditions are present, the answer is yes, and method 400 proceeds to 432. Otherwise, the answer is no, and method 400 proceeds to 440.

[0050] At 432, method 400 closes the turbocharger compressor bypass valve and the electrically driven compressor or supercharger bypass valve. Closing the turbocharger compressor bypass valve may direct all flow from the turbocharger compressor to or around the electrically driven compressor. Alternatively, the turbocharger compressor bypass valve may initially be open and then closed in response to flow through the turbocharger compressor being greater than a threshold, allowing airflow to be drawn past the turbocharger compressor until flow through the turbocharger compressor is sufficient to reduce the possibility of a pressure drop in the engine intake upstream of the turbocharger compressor. The electrically driven compressor bypass valve is closed to pressurize the air downstream of the electrically driven compressor.

[0051] At 434, method 400 activates the electrically driven compressor (ES) by supplying current and / or voltage to the electrically driven compressor. The speed of the electrically driven compressor is increased to a value based on the desired engine airflow and the desired throttle inlet pressure. By activating the electrically driven compressor, air may be provided to the engine at a faster rate than if only the turbocharger were present along the engine intake passage. After activating the electrically driven compressor, method 400 proceeds to the exit.

[0052] At 440, method 400 closes the turbocharger compressor bypass valve if open, and opens the electrically driven compressor bypass valve if closed. By closing the turbocharger compressor bypass valve, turbocharger airflow to the engine may be increased compared to when the turbocharger compressor bypass valve is open. Further, by opening the electrically driven compressor bypass valve, airflow from the turbocharger compressor to the throttle may be increased. After the turbocharger compressor bypass valve is closed and the electrically driven compressor bypass valve is opened, method 400 proceeds to 442.

[0053] At 442, method 400 deactivates the electrically driven compressor or supercharger. Deactivating the electrically driven compressor may conserve electrical energy. Furthermore, increases in engine airflow may be provided exclusively by the turbocharger compressor without operating the electrically driven compressor because turbocharger retardation conditions are not present. After deactivating the electrically driven compressor, method 400 proceeds to 444.

[0054] At 444, method 400 provides boost pressure (e.g., pressurized air) to the engine via the turbocharger without assistance from the electrically driven compressor or supercharger. After boost pressure is provided to the engine via the electrically driven compressor, method 400 proceeds to the exit.

[0055] In this way, pressure oscillations in the engine intake system may be reduced via an electrically driven compressor operating in conjunction with a turbocharger compressor driven by the exhaust gases. Further, the electrically driven compressor may be activated in response to pressure oscillations in the engine intake that are higher than a threshold. However, if the pressure oscillations are lower than the threshold, it may be more efficient to open the turbocharger compressor bypass valve. Further, if the compressor speed is higher than a threshold, it may be desirable to open the turbocharger compressor bypass valve rather than activating the electrically driven compressor, whereby a threshold engine airflow may be provided in less than a threshold period of time.

[0056] Consequently, the procedure under Fig. 4 provides a method for operating the engine compressors, comprising: receiving sensor data at a controller; and activating, via the controller, a second compressor in an engine intake based on the sensor data in response to a first compressor being within a threshold airflow of a surge condition. The method includes activating the second compressor from a deactivated state and further comprising adjusting a speed of the second compressor to provide a pressure at an output of the second compressor that is 180 degrees out of phase with a pressure at an output of the first compressor. The method includes the sensor data including a pressure ratio across the first compressor.The method includes the sensor data including airflow through the first compressor, and further comprising adjusting a speed of the second compressor based on a position of a compressor bypass valve of the first compressor.

[0057] In some examples, the method includes positioning the first compressor along the engine air intake upstream of the second compressor. The method includes positioning the second compressor as an electrically driven compressor. The method includes controlling the second compressor to a speed based on a pressure in the engine intake.

[0058] The procedure according to Fig. 4 also provides a method for operating engine compressors, comprising: receiving sensor data at a controller; and adjusting, via the controller, airflow through a second compressor in an engine intake based on the sensor data in response to a first compressor being within a threshold airflow of a surge condition. The method includes where adjusting airflow through the second compressor includes commanding airflow through the second compressor based on a predetermined desired airflow based on surge conditions of the first compressor. The method includes where the surge condition is a speed oscillation of the first compressor.The method includes adjusting the airflow through the second compressor including commanding the airflow through the second compressor based on the pressure or airflow data provided via a sensor.

[0059] In some examples, the method includes where adjusting airflow through the second compressor includes decreasing pressure at an outlet of the second compressor in response to an increase in pressure at an outlet of the first compressor. The method also includes where adjusting airflow through the second compressor includes increasing pressure at an outlet of the second compressor in response to a decrease in pressure at an outlet of the first compressor. The method further includes closing a bypass valve of the second compressor in response to the first compressor being within a threshold airflow of the surge condition.

[0060] As will be recognized by one of ordinary skill in the art, the Fig.4 may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. As such, the various steps or functions illustrated may be performed in the order illustrated, performed in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the objects, features, and advantages described herein, but is provided for ease of illustration and description. Although not explicitly illustrated, one of ordinary skill in the art will recognize that one or more of the illustrated steps or functions may be repeatedly performed depending on the particular strategy employed.Furthermore, the methods described herein may be a combination of the steps taken by a controller in the physical world and the instructions within the controller. At least portions of the control methods and routines disclosed herein may be stored as executable instructions in non-volatile memory and may be executed by the control system, including the controller, in combination with the various sensors, actuators, and other engine hardware. Additionally, ejector may be replaced by the terms aspirator or venturi nozzle, because the devices may function in a similar manner.

[0061] This concludes the description. Many changes and modifications would become apparent to those skilled in the art upon reading the description without departing from the spirit and scope of the description. For example, single-cylinder, I2, I3, I4, I5, V6, V8, V10, V12, and V16 engines operating on natural gas, gasoline, diesel, or alternative fuel configurations could advantageously utilize the present description.

Claims

[1] A method of operating prime mover compressors comprising: Receiving sensor data at a controller (12); and Activating, via the controller (12), a second compressor in an engine intake (171) based on the sensor data in response to a first compressor being within a threshold airflow of a surge condition, wherein the second compressor is activated from a deactivated state, and further comprising adjusting a speed of the second compressor to provide a pressure at an output of the second compressor that is 180 degrees out of phase with a pressure at an output of the first compressor. [2] The method of claim 1, wherein the sensor data includes a pressure ratio across the first compressor, and the method further comprises adjusting a speed of the second compressor based on a position of a compressor bypass valve (175) of the first compressor. [3] The method of claim 1, wherein the sensor data includes an air flow through the first compressor. [4] The method of claim 1, wherein the first compressor is positioned along the air inlet (42) of the engine (10) upstream of the second compressor. [5] The method of claim 1, wherein the second compressor is an electrically driven compressor (150). [6] The method of claim 1, wherein the second compressor is controlled to a speed based on a pressure in the engine inlet (171). [7] A method of operating prime mover compressors comprising: Receiving sensor data at a controller (12); and Adjusting, via the controller (12), airflow through a second compressor in an engine intake (171) based on the sensor data in response to a first compressor being within a threshold airflow of a surge condition; and Adjusting a speed of the second compressor based on a position of a compressor bypass valve (175) of the first compressor. [8] A method of operating prime mover compressors comprising: Receiving sensor data at a controller (12); and Adjusting, via the controller (12), airflow through a second compressor in an engine intake (171) based on the sensor data in response to a first compressor being within a threshold airflow of a surge condition; and further comprising closing a bypass valve (175) of the second compressor in response to the first compressor being within a threshold airflow of the surge condition. [9] The method of claim 8, wherein adjusting the air flow through the second compressor includes commanding the air flow through the second compressor based on a predetermined desired air flow based on the surge condition of the first compressor. [10] The method of claim 8, wherein the surge condition is a speed oscillation of the first compressor. [11] The method of claim 8, wherein adjusting the air flow through the second compressor includes commanding the air flow through the second compressor based on the pressure or air flow data provided via a sensor (58, 120). [12] The method of claim 8, wherein adjusting the air flow through the second compressor includes decreasing the pressure at an outlet of the second compressor in response to an increase in the pressure at an outlet of the first compressor. [13] The method of claim 8, wherein adjusting the air flow through the second compressor includes increasing the pressure at an outlet of the second compressor in response to a decrease in the pressure at an outlet of the first compressor. [14] Power machine system comprising: a prime mover (10) including an air inlet (42); an exhaust gas driven compressor (162) positioned along the air inlet (42) and including a bypass valve (175); an electrically driven compressor (150) positioned along the air inlet (42) downstream of the exhaust gas driven compressor (162); and a controller (12) containing non-transitory instructions for opening the bypass valve (175) in response to a first indication of impending surge of the exhaust-driven compressor (162) and for activating the electrically driven compressor (150) in response to a second indication of impending surge of the exhaust-driven compressor (162), while the bypass valve (175) is closed. [15] The engine system of claim 14, wherein the first indication of impending surge occurs at a first turbocharger compressor flow that is less than a second turbocharger compressor flow where the second indication of impending surge occurs. [16] The engine system of claim 15, further comprising additional non-transitory instructions to adjust air flow through the electrically driven compressor (150) in response to the second indication of impending surge. [17] The engine system of claim 16, wherein adjusting the air flow through the electrically driven compressor (150) includes commanding the air flow through the electrically driven compressor (150) based on the pressure or air flow data provided via a sensor (58, 120). [18] The engine system of claim 14, wherein the second compressor is activated from a deactivated state. [19] The engine system of claim 14, wherein the first and second indications of impending surge are based on an expected speed oscillation of the exhaust-driven compressor (162).

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