Method for controlling a TRIM adjustment mechanism of a centrifugal compressor

Abstract

A method for controlling an inlet regulating mechanism in an air inlet of a compressor to binary switch the mechanism between an open position and a closed position for adjusting the flow area of ​​the inlet. The method includes identifying a threshold line on a compressor diagram that represents the relationship between the compressor's pressure ratio and a corrected flow rate, at which the inlet regulating mechanism switches from one position to another. A fixed switching band spanning the threshold line can be used to determine when to initiate the position switching so that the switching is timed to coincide with the operating point reaching the threshold line. Alternatively, the time to reach the threshold line can be calculated instantaneously and compared with the actuator / mechanism response time.

Description

Technical Field

[0001] The present disclosure relates to centrifugal compressors, such as those used in turbochargers, and more particularly to centrifugal compressors in which the effective inlet area or diameter can be adjusted for different operating points. Background Art

[0002] An exhaust-driven turbocharger is a device that is used in conjunction with an internal combustion engine to increase the power output of the engine by compressing air delivered to the air intake of the engine for mixing with fuel and burning in the engine. A turbocharger includes a compressor wheel mounted on one end of a shaft in a compressor housing and a turbine wheel mounted on the other end of the shaft in a turbine housing. Typically, the turbine housing is formed separately from the compressor housing, and there is another center housing connected between the turbine housing and the compressor housing for accommodating the bearings of the shaft. The turbine housing defines a generally annular chamber that surrounds the turbine wheel and receives exhaust gas from the engine. The turbine assembly includes a nozzle leading from the chamber to the turbine wheel. Exhaust gas flows from the chamber through the nozzle to the turbine wheel, and the turbine wheel is driven by the exhaust gas. Thus, the turbine extracts power from the exhaust gas and drives the compressor. The compressor receives ambient air through the inlet of the compressor housing, and the air is compressed by the compressor wheel and then discharged from the housing to the engine air intake.

[0003] Turbochargers typically employ a centrifugal (also known as "radial") compressor wheel because centrifugal compressors can achieve relatively high pressure ratios in a compact arrangement. The compressor's intake air is received at an inlet section (inducer) portion of a centrifugal compressor wheel in a generally axial direction and is discharged at an outlet section (exducer) portion of the wheel in a generally radial direction. The compressed air from the wheel is delivered to a volute, and the air is supplied from the volute to the intake of an internal combustion engine.

[0004] The operating range of the compressor is an important aspect of the overall performance of the turbocharger. The operating range is usually defined by the surge line and the choke line on the compressor's operating map. The compressor map is usually expressed as a pressure ratio (discharge pressure) on the vertical axis. Pout Divide by the inlet pressure Pin ) versus the corrected mass flow rate on the horizontal axis. The choke line on the compressor map is located at high flow rates and represents the locus of maximum mass flow rate points over a range of pressure ratios; that is, for a given point on the choke line, it is not possible to increase the flow rate while maintaining the same pressure ratio because a choked flow condition occurs in the compressor.

[0005] The surge line is located at low flow rates and represents the locus of minimum mass flow rate points without surge over a range of pressure ratios; that is, for a given point on the surge line, decreasing the flow rate without changing the pressure ratio or increasing the pressure ratio without changing the flow rate will cause surge to occur. Surge is a flow instability that typically occurs when the compressor blade incidence angle becomes so large that significant flow separation occurs over the compressor blades. Pressure fluctuations and flow reversals may occur during surge.

[0006] In a turbocharger for an internal combustion engine, compressor surge may occur when the engine is operated at high load or torque and low engine speed or when the engine is operated at low speed and there is a high level of exhaust gas recirculation (EGR). Surge may also occur when the engine is suddenly decelerated from a high speed state. Extending the surge-free operating range of the compressor to lower flow rates is a goal generally sought in compressor design.

[0007] One approach for shifting the surge line of a centrifugal compressor to the left (i.e., surge is delayed to a lower flow rate at a given pressure ratio) and shifting the choke flow line to the right (i.e., choke flow is increased to a higher flow rate at a given pressure ratio) is to employ a trim adjustment mechanism in the compressor inlet. Applicant is the owner of co-pending applications disclosing various such trim adjustment mechanisms, see, e.g., Application Nos. 14 / 537,339, 14 / 532,278, 14 / 642,825, 14 / 573,603, and 14 / 551,218; the entire disclosures of said applications are hereby incorporated by reference herein.

[0008] The present disclosure relates to a method for controlling such a trim adjustment mechanism. Summary of the invention

[0009] The present disclosure describes a method for controlling an inlet regulating mechanism in an air inlet of a compressor so as to switch the mechanism in a binary manner between a closed position and an open position. In the closed position, the flow area of ​​the inlet is reduced relative to the flow area in the open position of the mechanism. The method includes identifying a threshold line on a compressor map of the relationship between the pressure ratio PR of the compressor and the corrected flow rate Wc. The threshold line is a line where the inlet regulating mechanism will move from the open position to the closed position when the operating point of the compressor on the compressor map reaches the threshold line starting from the high flow side of the threshold line under conditions of a quasi-static movement of the operating point. According to one embodiment, the method includes the following steps:

[0010] Tracking movement of the compressor's operating point on a compressor map by sensing at periodic time intervals;

[0011] determining at each of said time intervals whether said operating point is on a high flow side of a threshold line or on a low flow side of a threshold line;

[0012] determining at each of the time intervals whether the operating point is moving toward a threshold line; and

[0013] When the operating point is determined to be on the high flow side of a threshold line and is moving toward the threshold line, actuation of the inlet regulating mechanism is initiated to switch from the open position to the closed position, wherein the actuation begins before the operating point reaches the threshold line.

[0014] When the operating point is determined to be on a low flow side of a threshold line and is moving toward the threshold line, the method includes initiating actuation of an inlet regulating mechanism to switch from a closed position to an open position before the operating point reaches the threshold line.

[0015] According to the present invention, there are various techniques by which a switch from open to closed or from closed to open can be "anticipated" before the operating point actually reaches the threshold line. In all cases, the goal is to time the switch so that, taking into account the time lag associated with moving the mechanism from one position to another, the mechanism reaches the new position substantially when the operating point reaches the threshold line. One such technique requires identifying a high switch line on the compressor map that is spaced from the threshold line on the high flow side of the threshold line, and identifying a low switch line on the compressor map that is spaced from the threshold line on the low flow side of the threshold line. The steps of initiating actuation of the inlet regulating mechanism to switch from the open position to the closed position and from the closed position to the open position are then based in part on the position of the operating point relative to the high switch line and relative to the low switch line, respectively.

[0016] For example, suppose that the operating point is moving from a region of the compressor map at a relatively high flow rate, where the inlet regulating mechanism is in the open position, and is moving towards the threshold line and is predicted to reach the threshold line. In this case, the initiation of the actuation of the mechanism begins when the operating point crosses the high switching line, which is located in part based on the maximum expected movement rate of the operating point on the map and the response time of the actuator and the inlet regulating mechanism. Therefore, even when the operating point is moving towards the threshold line at the maximum rate, the switching to the closed position will not occur too late.

[0017] Then, it will be readily understood by those skilled in the art that in the case of an electrically driven turbocharger (so-called "e-turbo"), the distance between the low switching line and the high switching line (represented herein as "switching band") must be relatively greater than in the case of a conventional turbocharger driven by an exhaust-driven turbine. This is because an e-turbo can accelerate and decelerate at a faster rate than a conventional turbocharger.

[0018] In one embodiment of the present invention, the step of determining whether the operating point is moving toward the threshold line includes calculating the time rate of change ΔNt / Δt of the speed of the turbocharger, and using the time rate of change together with the result of the step of determining whether the operating point is on the high flow side of the threshold line or on the low flow side of the threshold line. For example, if the time rate of change is negative (i.e., the turbocharger is decelerating, and the operating point is on the high flow side of the threshold line, then the operating point is moving toward the threshold line. On the other hand, if the time rate of change of the turbine speed is positive (accelerating), and the operating point is on the high flow side, then the operating point is moving away from the threshold line.

[0019] Instead of using the time rate of change of the turbocharger speed, the method may use the time rate of change of the speed of the internal combustion engine ΔNe / Δt together with the result of the step of determining whether the operating point is on the high flow side or the low flow side of the threshold line.

[0020] As described, the high switching line can be spaced apart from the threshold line by an amount based in part on the response time Tr required to move the inlet regulating mechanism from the open position to the closed position. Similarly, the low switching line can be spaced apart from the threshold line by an amount based in part on the response time Tr .

[0021] In one embodiment of the present invention, the method further comprises the following steps:

[0022] At each of said time intervals, the time rate of change of the engine speed ΔNe / Δt is calculated (or alternatively, the time rate of change of the turbocharger speed ΔNt / Δt; still another alternative is to use the time rate of change of the compressor corrected flow rate ΔWc / Δt );

[0023] At each of the time intervals, calculating a distance D between the operating point on the compressor map and the threshold line;

[0024] At each of the time intervals, the time period it will take for the operating point to reach the threshold line is calculated based on the distance D and the time change rate. T TL ;as well as

[0025] At each of the time intervals, during the time period T th compared with the known response time Tr of the inlet regulating mechanism transitioning between the open position and the closed position;

[0026] Wherein the step of initiating actuation of the inlet regulating mechanism is performed based on said comparison.

[0027] As an example, in one embodiment, the step of initiating actuation of the inlet regulating mechanism is performed during the time period T TL Approximately equal to the response time Tr The purpose is similar to that of the embodiment using a low switching line and a high switching line, namely, to time the switching so that, taking into account the response time associated with moving the mechanism from one position to another, the mechanism reaches the new position substantially when the operating point reaches the threshold line.

[0028] The following example is shown:

[0029] 1. A method for controlling a compressor inlet regulating mechanism, the compressor inlet regulating mechanism being arranged in an air inlet of a centrifugal compressor of a turbocharger so as to increase an intake pressure of an internal combustion engine, the inlet regulating mechanism being actuatable to switch between a closed position for reducing a flow area of ​​the air inlet and an open position for increasing a flow area of ​​the air inlet, the method comprising:

[0030] identifying a threshold line on a compressor map of the relationship between the pressure ratio PR and the corrected flow rate Wc of the compressor, the threshold line being a line at which the inlet regulating mechanism moves from the open position to the closed position when the operating point of the compressor on the compressor map reaches the threshold line starting from the high flow side of the threshold line under the condition of quasi-static movement of the operating point;

[0031] tracking movement of an operating point of the compressor on the compressor map by sensing at periodic time intervals;

[0032] determining at each of the time intervals whether the operating point is on the high flow side of the threshold line or on the low flow side of the threshold line;

[0033] determining at each of the time intervals whether the operating point is moving toward the threshold line; and

[0034] When the operating point is determined to be on the high flow side of the threshold line and is moving toward the threshold line, actuation of the inlet regulating mechanism is initiated to switch from the open position to the closed position, wherein the actuation begins before the operating point reaches the threshold line.

[0035] 2. The method according to example 1, further comprising:

[0036] When the operating point is determined to be on the low flow side of the threshold line and is moving toward the threshold line, actuation of the inlet regulating mechanism is initiated to switch from the closed position to the open position before the operating point reaches the threshold line.

[0037] 3. The method according to Example 2 further comprises:

[0038] identifying a high switching line on the compressor map, the high switching line spaced apart from the threshold line on the high flow side of the threshold line;

[0039] identifying a low switching line on the compressor map, the low switching line being spaced apart from the threshold line on the low flow side of the threshold line; and

[0040] Wherein, the step of initiating actuation of the inlet regulating mechanism to switch from the open position to the closed position and vice versa is based in part on the position of the operating point relative to the high switching line and relative to the low switching line, respectively.

[0041] 4. A method according to Example 3, wherein the step of determining whether the operating point is moving toward the threshold line includes calculating a time rate of change ΔNt / Δt of the speed of the turbocharger and using the time rate of change together with the result of the step of determining whether the operating point is on the high flow side of the threshold line or on the low flow side of the threshold line.

[0042] 5. A method according to Example 3, wherein the step of determining whether the operating point is moving toward the threshold line includes calculating a time rate of change ΔNe / Δt of the speed of the internal combustion engine and using the time rate of change together with a result of the step of determining whether the operating point is on the high flow side of the threshold line or on the low flow side of the threshold line.

[0043] 6. The method of example 3, wherein the high switching line is spaced apart from the threshold line by an amount based on a response time Tr required to move the inlet regulating mechanism from the open position to the closed position.

[0044] 7. The method of example 6, wherein the low switching line is spaced apart from the threshold line by an amount based on a response time Tr required to move the inlet regulating mechanism from the closed position to the open position.

[0045] 8. The method according to Example 2 further comprises:

[0046] At each of the time intervals, calculating a time rate of change ΔNe / Δt of the engine speed;

[0047] At each of the time intervals, calculating a distance D between the operating point on the compressor map and the threshold line;

[0048] At each of the time intervals, the time period it will take for the operating point to reach the threshold line is calculated based on the distance D and the time change rate ΔNe / Δt. T TL ;as well as

[0049] At each of the time intervals, during the time period T TL comparing with a known response time Tr of the inlet regulating mechanism to transition between the open position and the closed position;

[0050] Therein, the step of initiating activation of the inlet regulating mechanism is performed based on the comparison.

[0051] 9. The method of example 8, wherein the step of initiating actuation of the inlet regulating mechanism is performed during the time period T TL Approximately equal to the response time Tr When implemented.

[0052] 10. The method according to Example 2 further comprises:

[0053] At each of the time intervals, calculating a time rate of change ΔNt / Δt of the speed of the turbocharger;

[0054] At each of the time intervals, calculating a distance D between the operating point on the compressor map and the threshold line;

[0055] At each of the time intervals, the time period it will take for the operating point to reach the threshold line is calculated based on the distance D and the time change rate ΔNt / Δt. T TL ;as well as

[0056] At each of the time intervals, during the time period T TL comparing with a known response time Tr of the inlet regulating mechanism to transition between the open position and the closed position;

[0057] Therein, the step of initiating activation of the inlet regulating mechanism is performed based on the comparison.

[0058] 11. The method of example 10, wherein the step of initiating actuation of the inlet regulating mechanism is performed during the time period T TL Approximately equal to the response time Tr When implemented.

[0059] 12. The method according to Example 2 further comprises:

[0060] At each of the time intervals, calculating a time change rate ΔWc / Δt of the flow rate of the compressor;

[0061] At each of the time intervals, calculating a distance D between the operating point on the compressor map and the threshold line;

[0062] At each of the time intervals, the time period it will take for the operating point to reach the threshold line is calculated based on the distance D and the time change rate ΔWc / Δt. T TL ;as well as

[0063] At each of the time intervals, during the time period T TL comparing with a known response time Tr of the inlet regulating mechanism to transition between the open position and the closed position;

[0064] Therein, the step of initiating activation of the inlet regulating mechanism is performed based on the comparison.

[0065] 13. The method of example 12, wherein the step of initiating actuation of the inlet regulating mechanism is performed during the time period T TL Approximately equal to the response time Tr When implemented.

[0066] 14. A computer program product, comprising at least one computer-readable storage medium having computer-executable program code instructions stored therein for controlling a compressor inlet regulating mechanism disposed in an air inlet of a centrifugal compressor of a turbocharger so as to increase an intake pressure of an internal combustion engine, the inlet regulating mechanism being actuatable to switch between a closed position for reducing a flow area of ​​the air inlet and an open position for increasing a flow area of ​​the air inlet, the compressor having a compressor map of a relationship between a pressure ratio PR of the compressor and a corrected flow rate Wc, the compressor map comprising a threshold line, at which the inlet regulating mechanism moves from the open position to the closed position when an operating point of the compressor on the compressor map reaches the threshold line starting from a high flow side of the threshold line under a quasi-static movement of the operating point, the computer-executable program code instructions comprising:

[0067] program code instructions for tracking movement of an operating point of the compressor on the compressor map by sensing at periodic time intervals;

[0068] program code instructions for determining at each of the time intervals whether the operating point is on the high flow side of the threshold line or on the low flow side of the threshold line;

[0069] Program code instructions for determining at each of the time intervals whether the operating point is moving toward the threshold line; and

[0070] Program code instructions for initiating actuation of the inlet regulating mechanism to switch from the open position to the closed position in response to a determination that the operating point is on the high flow side of the threshold line and is moving toward the threshold line, wherein the initiation begins before the operating point reaches the threshold line.

[0071] 15. The computer program product of Example 14, further comprising program code instructions for initiating actuation of the inlet regulating mechanism to switch from the closed position to the open position before the operating point reaches the threshold line in response to a determination that the operating point is on the low flow side of the threshold line and is moving toward the threshold line.

[0072] 16. A computer program product according to Example 15, wherein the compressor map includes a high switching line spaced apart from the threshold line on the high flow side of the threshold line and a low switching line spaced apart from the threshold line on the low flow side of the threshold line, and the computer program product further includes program code instructions for switching from the open position to the closed position and from the closed position to the open position based in part on the position of the operating point relative to the high switching line and relative to the low switching line, respectively.

[0073] 17. A computer program product according to Example 16, wherein determining whether the operating point is moving toward the threshold line includes calculating a time rate of change ΔNt / Δt of the speed of the turbocharger and using the time rate of change together with the result of the step of determining whether the operating point is on the high flow side of the threshold line or on the low flow side of the threshold line.

[0074] 18. A computer program product according to Example 16, wherein determining whether the operating point is moving toward the threshold line includes calculating a time rate of change ΔNe / Δt of the speed of the internal combustion engine and using the time rate of change together with the result of the step of determining whether the operating point is on the high flow side of the threshold line or on the low flow side of the threshold line.

[0075] 19. The computer program product of example 15, further comprising:

[0076] program code instructions for calculating a time rate of change ΔNe / Δt of the engine speed at each of the time intervals;

[0077] program code instructions for calculating a distance D between the operating point on the compressor map and the threshold line at each of the time intervals;

[0078] For calculating the time period that the operating point will take to reach the threshold line based on the distance D and the time change rate ΔNe / Δt at each time interval T TL program code instructions; and

[0079] for at each said time interval in said time period T TL Program code instructions for comparing the response time Tr of the inlet adjustment mechanism to transition between the open and closed positions and initiating actuation of the inlet adjustment mechanism based on the comparison.

[0080] 20. The computer program product of example 15, further comprising:

[0081] program code instructions for calculating a time rate of change ΔNt / Δt of the speed of the turbocharger at each of the time intervals;

[0082] program code instructions for calculating a distance D between the operating point on the compressor map and the threshold line at each of the time intervals;

[0083] For calculating the time period that the operating point will take to reach the threshold line based on the distance D and the time change rate ΔNt / Δt at each time interval T TL program code instructions; and

[0084] for at each said time interval in said time period T TL Program code instructions for comparing the response time Tr of the inlet adjustment mechanism to transition between the open and closed positions and initiating actuation of the inlet adjustment mechanism based on the comparison.

[0085] 21. The computer program product of example 15, further comprising:

[0086] program code instructions for calculating a time rate of change ΔWc / Δt of a flow rate of the compressor at each of the time intervals;

[0087] program code instructions for calculating a distance D between the operating point on the compressor map and the threshold line at each of the time intervals;

[0088] For calculating the time period that the operating point will take to reach the threshold line based on the distance D and the time change rate ΔWc / Δt at each time interval T TL program code instructions; and

[0089] for at each said time interval in said time period T TL Program code instructions for comparing the response time Tr of the inlet adjustment mechanism to transition between the open and closed positions and initiating actuation of the inlet adjustment mechanism based on the comparison. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Having thus generally described the invention, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and in which:

[0091] Figure 1 is a diagrammatic depiction of a compressor having an inlet regulating mechanism, wherein the inlet regulating mechanism is in a closed position;

[0092] Figure 2 Similar to Figure 1 , but showing the inlet adjustment mechanism in an open position;

[0093] Figure 3 Schematically depicting a compressor diagram, where the inlet adjustment mechanism corresponds to Figure 1 in a closed position;

[0094] Figure 4 Schematically depicting a compressor diagram, where the inlet adjustment mechanism corresponds to Figure 2 in an open position;

[0095] Figure 5 depicts a compressor map according to one embodiment of the present invention, identifying a threshold line at which the inlet regulating mechanism switches between its open and closed positions, and showing a low switching line offset on the low flow side of the threshold line and a high switching line offset on the high flow side of the threshold line;

[0096] Figure 6 is a pictorial illustration of an engine control unit (ECU) in communication with an actuator that actuates an inlet regulating mechanism to move it between an open position and a closed position;

[0097] Figure 7 is a flow chart showing a method according to one embodiment of the present invention, which utilizes Figure 5 The low switching line and the high switching line depicted in ;

[0098] Figure 8 is similar to Figure 5 , but shows another embodiment of the invention, in which the time elapsed before the operating point reaches the threshold line is instantaneously calculated. T TL , and compare it with the response time of the inlet regulating mechanism switching from one position to another; and

[0099] Fig. 9 is a diagram showing the time of using instantaneous calculation according to an embodiment of the present invention T TL Flowchart of the method. DETAILED DESCRIPTION

[0100] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some but not all embodiments of the invention are shown. Indeed, these inventions may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Throughout the text, like reference numerals refer to like elements.

[0101] A compressor 10 according to one embodiment of the present invention is shown in cross-sectional view. Figure 1 and Figure 2 The compressor 10 includes a compressor housing 12 defining an air inlet 14 extending in an axial direction of the compressor. A compressor wheel 15 including a hub 16 from which a plurality of blades 20 extend generally radially outward is disposed in the compressor housing and is attached to one end of a shaft 18 rotatably driven in a suitable manner (e.g., by an exhaust gas driven turbine, not shown) for rotatably driving the compressor wheel 15. The compressor housing defines a diffuser 22 for receiving and diffusing air compressed as it passes through the compressor wheel. The diffuser delivers the diffused compressed air into a volute 24 defined by the compressor housing.

[0102] According to the invention, the compressor of the turbocharger comprises an inlet adjustment mechanism 30 which is arranged in the air inlet 14 of the compressor housing and which can be adjusted in a closed or "low trim" position ( Figure 1 ) versus the open or “high trim” position ( Figure 2 ). Movement of the mechanism 30 may require axial sliding, pivotal movement, or helical (screw-like) movement of the mechanism, to name a few non-limiting examples. The details of the structure and operation of the inlet adjustment mechanism 30 are not relevant to the present disclosure, and any mechanism that operates to effectively change the flow area of ​​the air inlet 14 to the compressor wheel 15 may be employed in the practice of the present invention.

[0103] The inlet adjustment mechanism 30 enables adjustment of the effective size or diameter of the inlet into the compressor wheel 15. Figure 2 As shown in FIG. 1 , when the inlet adjustment mechanism is in the high trim or open position, Figure 1 The effective diameter of the inlet into the compressor wheel is relatively increased compared to the effective diameter in the low trim or closed position of the compressor wheel. To achieve this effect, the axial spacing distance from the mechanism 30 to the compressor wheel must be as small as possible.

[0104] At intermediate and high flow rates, the inlet adjustment mechanism 30 may be as follows Figure 2 This can have the effect of increasing the effective inlet diameter and therefore reducing the flow velocity into the compressor wheel. Figure 4 Show Figure 2 An exemplary compressor diagram for a high trim position of . The diagram is in the form of a compressor pressure ratio (discharge pressure divided by inlet pressure) versus a corrected flow rate (e.g., mass flow rate corrected to standard temperature and pressure inlet conditions). The diagram includes a series of constant speed lines N1 open 、N2 open 、N3 open 、N4 open and N5 open , at each of which the compressor rotational speed is held constant while the corrected flow and pressure ratio vary. The graph includes a high trim surge line, which is the locus of the point at which surge of the compressor is about to occur; that is, if the flow is reduced at the same pressure ratio or the pressure ratio is increased at the same flow, the compressor will experience surge.

[0105] At low flow rates, the inlet adjustment mechanism 30 can be placed Figure 1 This can have the effect of reducing the effective inlet diameter, and therefore increasing the flow velocity into the compressor wheel. The result will be a reduction in the compressor blade incidence angle, effectively stabilizing the flow (i.e., making blade stall and compressor surge less likely). In other words, the compressor surge line will move to lower flow rates (to the left on a plot of compressor pressure ratio versus flow rate). This is shown in Figure 3 middle, Figure 3 The compressor map shows the low trim position. The low trim map has the same speed line value. That is, N1 closed The value is equal to N1 open and similarly for other speeds.

[0106] According to the present invention, Figure 3 and Figure 4The compressor map may be based on test data of the compressor operating with the inlet regulating mechanism in the closed position and in the open position, respectively. Alternatively, the compressor map may be based on model predicted data of the compressor with the inlet regulating mechanism in the closed position and in the open position, respectively.

[0107] Figure 5 It is superposition Figure 1 The speed line of the low trim or closed position and Figure 2 It will be seen that for a given compressor speed, the corresponding low and high trim speed lines are Figure 5 This means that at the pressure ratio and corrected flow conditions where the velocity lines cross, the inlet regulating mechanism can be switched from one of its two positions to the other without any significant effect on the flow rate and pressure ratio of the compressor. Thus, for example, Figure 5 At the point marked "A" in FIG. 1 , the inlet regulating mechanism can be moved from a closed position to an open position, or from an open position to a closed position, without significant effect on the compressor behavior.

[0108] This characteristic velocity line crossing feature can be utilized when designing a control scheme for controlling the operation of the inlet regulating mechanism. Figure 5 A "threshold" line TL is established on the superimposed graph in the figure, representing the "best fit" of the intersection of the speed lines, and the operation of the inlet regulating mechanism can be adjusted with reference to the position of the compressor on the compressor map where the compressor is operating, and in particular the position of the operating point relative to the threshold line. Figure 5 When operating in the area to the left of the threshold line TL (called the low flow side of the threshold line), the inlet adjustment mechanism can be placed Figure 1 When the compressor is operating to the right of the threshold line, in the region indicated as the high flow side of the threshold line, the inlet adjustment mechanism may be placed in the low trim or closed position. Figure 2 By switching between the closed position and the open position when the operating point moves to cross the threshold line, the transition from one position to the other will not result in any abrupt changes in the compressor flow rate and pressure ratio.

[0109]

[0066] Implementations of the control scheme described above may be implemented in various ways. Figure 6The general architecture of a system for controlling an inlet adjustment mechanism 30 is shown. An actuator 26 of a suitable type is coupled to the inlet adjustment mechanism. The actuator may operate on any of a variety of principles; for example, the actuator may employ an electric motor, pneumatics, hydraulics, etc., in order to impart movement to the inlet adjustment mechanism to move it between its closed and open positions. The actuator 26 communicates with a control unit 40. The control unit includes a processor 50 (e.g., a microprocessor), a memory 60 (e.g., a non-volatile ROM, PROM, EPROM, or EEPROM memory), and an interface 70 for communicating with other devices in the system. The memory may be programmed (e.g., in hardware and / or firmware and / or software) with control instructions that are executed by the processor to implement the functions of the control unit.

[0110] In an embodiment, the engine includes an engine control unit or ECU, such as that present on vehicles such as cars and trucks. An ECU is an electronic control unit that may include hardware and / or software components configured to control various aspects of engine operation. In particular, the ECU may receive inputs from various engine sensors and turbocharger sensors, and control various engine and turbocharger actuators. Engine sensors may be placed at various points in the engine to measure or otherwise determine corresponding engine parameters. Examples of engine sensors may include a throttle position sensor, an air temperature sensor, an engine revolutions per minute (RPM) sensor, an engine load sensor, an accelerator pedal position sensor, and / or other sensors. The engine actuator may include various relays, solenoids, ignition coils, or other electrically operable devices that may be used to control corresponding engine parameters. A turbocharger sensor may include sensors for measuring turbocharger rotational speed, compressor inlet pressure, compressor discharge pressure, compressor corrected flow rate, and other parameters.

[0111] In such Figure 6 In the exemplary embodiment shown in , the ECU 40 may include an anti-surge control module for adjusting the position of the inlet regulating mechanism 30. The anti-surge control module may be any device, such as an apparatus or circuit system implemented in hardware, software, or a combination of hardware and software configured to implement the corresponding functions of the anti-surge control module as described herein. In some embodiments, the anti-surge control module may be configured to enhance the ability of the ECU 20 with respect to surge prevention by identifying engine conditions based on which actions will be taken for anti-surge activities and with respect to taking or directing actions with respect to anti-surge activities (e.g., via control of the actuator 26 for the inlet regulating mechanism 30). As such, in an exemplary embodiment, the anti-surge control module may simply provide additional functionality to the ECU 40. However, in some embodiments, the anti-surge control module may be a unit separate from the ECU (i.e., Figure 6The control unit 40 shown in FIG. 4 may not include an ECU, but may communicate with the ECU).

[0112] The memory device 60 may include, for example, volatile and / or non-volatile memory. The memory device 60 may be configured to store information, data, applications, modules, instructions, etc. so as to enable the device to implement various functions according to exemplary embodiments of the present invention. For example, the memory device 60 may be configured to buffer input data for processing by the processor 50. Additionally or alternatively, the memory device 60 may be configured to store instructions corresponding to an application for execution by the processor 50.

[0113] The processor 50 may be a processor of an ECU or a co-processor or processor of a separate anti-surge control module. The processor 50 may be implemented in a variety of different ways. For example, the processor 50 may be implemented as a processing element, a co-processor, a controller, or various other processing devices or devices including integrated circuits, such as, for example, ASICs (Application Specific Integrated Circuits), FPGAs (Field Programmable Gate Arrays), hardware accelerators, and the like. In an exemplary embodiment, the processor 50 may be configured to execute instructions stored in a memory device 60 or otherwise accessible by the processor 50. In this way, whether configured by hardware or software methods or by a combination thereof, the processor 50 may represent an entity capable of implementing operations according to an embodiment of the present invention when configured accordingly. Thus, for example, when the processor 50 is implemented as an ASIC, FPGA, and the like, the processor 50 may be a specially configured hardware for performing the operations described herein. Alternatively, as another example, when the processor 50 is implemented as an executor of software instructions, the instructions may configure the processor 50 specifically to implement the algorithms and / or operations described herein, and if not for a specific configuration provided by the instructions, the processor 50 may otherwise be a general-purpose processing element. However, in some cases, the processor 50 may be a processor of a specific device (e.g., an ECU) that is suitable for employing embodiments of the present invention by further configuring the processor 50 with instructions for implementing the algorithms and / or operations described herein (e.g., by adding an anti-surge control module).

[0114] The memory 60 of the control unit stores basic compressor maps, for example corresponding to Figure 3 The diagram may be stored in any of a variety of forms, for example including a corrected flow rate along a series of constant velocity lines N1, N2, N3, etc. W c Variable and pressure ratio PR The speed can be the turbocharger speed Nt , or alternatively may be the engine speed NeThe following description assumes the use of engine speed, but it will be appreciated that turbocharger speed may be used in place of engine speed. The memory also stores a threshold line TL of a curve fit representing the intersection of the speed lines derived in the manner previously described. The threshold line may be stored in any of a variety of forms, such as PR and W c The relationship table or PR express W c Alternatively, the threshold line can be derived from the corrected flow W c With engine speed Ne The processor 50 receives the corrected flow rate of the compressor W c , Engine speed Ne and the time rate of change of engine speed ΔNe / Δt The flow rate, engine speed, and time rate of change of engine speed (also referred to as acceleration or deceleration) are continuously sensed by suitable sensors, and the sensed values ​​are sent to the processor (e.g., at regular time step intervals, such as every 0.1 second or other appropriately selected intervals). The processor uses these sensed parameters to decide what position the inlet adjustment mechanism should be placed in, and when to switch from one position to another, as further described below.

[0115] Reference now Figure 5 and Figure 7 A method according to a first embodiment of the invention is explained. The invention addresses the challenge of how to ensure that the inlet regulating mechanism switches from one position to another at an appropriate location on the compressor map. Ideally, the switch would occur exactly on the threshold line TL. However, in practice, this can be challenging because the operating point can move rapidly on the compressor map during certain operating conditions of the internal combustion engine. For example, consider the situation when the vehicle driver fully depresses the accelerator pedal to pass another vehicle and the engine is operating in a high speed, high flow state. Placing the operating point at the threshold line TL Figure 5 The high flow side of the middle threshold line (the inlet regulating mechanism is in the open position). Then, suppose the driver suddenly releases the accelerator pedal completely. The engine speed and flow rate will drop rapidly, resulting in an operating point of Figure 5 . In this case, if the controller waits until it senses that the operating point is on the threshold line before initiating actuation of the inlet regulating mechanism, the mechanism will actually close too late due to the finite response time required for the actuator to move the mechanism from the open position to the closed position. The present invention provides a method for "anticipating" the crossing of the threshold line so that the actuator can initiate the switching before the operating point reaches the threshold line.

[0116] Therefore, the first method of the present invention is shown in Figure 5 and Figure 7 The method requires the use of Figure 5 A "switching band" is defined between a low switching line LSL and a high switching line HSL as shown in . The low switching line is offset from the threshold line on the low flow side of the threshold line, and the high switching line is offset from the threshold line on the high flow side of the threshold line. The two switching lines are fixed in place, and their positions can be stored in the controller memory in the same manner as the threshold lines are stored (i.e., table lookup, curve fitting, etc.). The width of the switching band is selected based primarily on two factors: (1) the response time required for the actuator / mechanism to switch from one position to another; Tr , and (2) the maximum expected rate at which the operating point can move on the compressor map. This can be understood by considering some hypothetical cases. In one case, the operating point moves only “quasi-statically” (i.e., very slowly) and the response time Tr In this case, the controller does not need to start switching the mechanism from open to closed (or vice versa) until the operating point is very close to or substantially on the threshold line - or in other words, the switching band can be very narrow. At the other extreme, consider that the operating point can move very quickly along the compressor map, and the response time Tr In this case, the controller must anticipate that the operating point reaches the threshold line TL and must start switching the mechanism well before the operating point actually reaches the threshold line.

[0117] Those skilled in the art will recognize that in the case of an electric motor driven turbocharger (so-called "e-turbo"), the switching band must therefore be relatively wide, since the e-turbo can accelerate and decelerate quickly. On the other hand, a conventional exhaust gas driven turbocharger accelerates and decelerates more slowly, and therefore the switching band can be narrower. Therefore, the switching band is adjusted according to the specific engine / turbocharger system characteristics.

[0118] Figure 7 is a flow chart illustrating a first method according to one embodiment of the present invention. In step 102, a corrected flow rate of the compressor is detected for the current operating point of the compressor using suitable sensors well known in the art. W c , Engine speed Ne and the time rate of change of engine speed ΔNe / Δt In decision step 104, it is determined based on these parameters whether the operating point (OP) is located on the threshold line TL or on the high flow side of the threshold line ( Figure 5If the answer to the query is "yes" (Y), the process proceeds to decision step 106, which asks ΔNe / Δt is greater than zero (i.e., the engine is accelerating). If the answer to the inquiry is "yes", the inlet regulating mechanism remains in the open position as indicated at 107, because the operating point is not moving towards the threshold line. On the other hand, if the answer to decision step 106 is "no" (meaning that the engine is not accelerating), the operating point may be moving towards the threshold line, so a further decision step 108 is performed, asking whether the operating point (OP) is on the high switching line HSL. If the answer is "yes", the inlet regulating mechanism is switched to the closed position as indicated at 109; otherwise, if OP is not on HSL, the mechanism remains in the open position as indicated at 110.

[0119] If decision step 104 has a "no" answer (meaning the operating point is on the low flow side of the threshold line), then decision step 112 is performed, asking ΔNe / Δt Is it greater than zero (i.e., the engine is accelerating). If the answer is "no", the mechanism is closed (or remains in the closed position) as indicated at 113, because this means that the operating point is not moving towards the threshold line. If decision step 112 produces a "yes" result (i.e., the engine is accelerating), it means that the operating point is moving towards the threshold line. Therefore, a further decision step 114 is performed, asking whether the operating point is on the low switching line LSL. If the answer is "yes", the mechanism is switched to the open position as indicated at 115; otherwise, the mechanism remains closed as indicated at 116.

[0120] The process then returns to step 102 and the steps are repeated at regular time steps. At each time step, the detected operating parameters of the previous time step and the current time step are remembered and compared. By appropriately selecting the time step interval to be short enough relative to the expected maximum rate at which the flow rate through the compressor can change (and relative to the response time of the actuator / mechanism), it can be ensured that the inlet regulating mechanism switches from one position to another at or close enough to the threshold line that the switching has no significant effect on the flow rate and pressure ratio. Therefore, there is no sudden perceptible change in compressor performance when the switch occurs.

[0121] Thus, the method of the first embodiment generally requires the following steps: tracking the movement of the operating point of the compressor on the compressor map by detecting at periodic time intervals; determining at each of the time intervals whether the operating point is on the high flow side of the threshold line or on the low flow side of the threshold line; determining at each of the time intervals whether the operating point is moving toward the threshold line; and when the operating point is determined to be on the high flow side of the threshold line and moving toward the threshold line, initiating actuation of the inlet regulating mechanism to switch from the open position to the closed position, wherein the initiation begins before the operating point reaches the threshold line, and when the operating point is determined to be on the low flow side of the threshold line and moving toward the threshold line, initiating actuation of the inlet regulating mechanism to switch from the closed position to the open position before the operating point reaches the threshold line. More specifically, the method of the first embodiment of the present invention utilizes a fixed low switching line LSL and a fixed high switching line HSL in the decision of whether and when to switch the mechanism from closed to open or from open to closed, respectively.

[0122] Reference now Figure 8 and Fig. 9 A second embodiment of the present invention is explained. In the second embodiment, there is no fixed switching band as in the previous embodiment. Figure 8 In the compressor diagram of FIG. 1 , the dotted line shows that the operating point OP is moving toward the threshold line (i.e., Figure 8 However, in the case of Figure 8 At the instant indicated by , the operating point is currently on the high flow side of the threshold line TL. The method of the second embodiment generally requires instantaneous calculation (i.e., prediction based on the distance D to the threshold line and the current speed at which the operating point is moving on the graph) of the time it will take for the operating point to reach the threshold line, which time period is denoted herein as T TL The predicted time period is then compared to the response time Tr of the actuator / mechanism switching position, and the comparison is used to decide if and when to initiate switching.

[0123] More specifically, refer to Fig. 9 In step 202, a corrected flow rate of the compressor is detected for the current operating point of the compressor using suitable sensors well known in the art. W c , Engine speed Ne and the time rate of change of engine speed ΔNe / Δt At step 203, based on the detected parameters of step 202, the time T required for the operating point OP to move from its current position to the threshold line TL is calculated. TL In decision step 204, it is determined based on the detected parameters whether the operating point (OP) is located on the threshold line TL or on the high flow side of the threshold line ( Figure 8If the answer to the query is "yes" (Y), the process proceeds to decision step 206, which asks ΔNe / Δt is greater than zero (i.e., the engine is accelerating). If the answer to said inquiry is "yes," the inlet regulating mechanism remains in the open position as indicated at 207, since the operating point is not moving toward the threshold line. On the other hand, if the answer to decision step 206 is "no" (meaning that the engine is not accelerating), the operating point may be moving toward the threshold line, so an additional decision step 208 is performed, asking whether the response time Tr is greater than or equal to the time T required for the operating point to reach the threshold line. TL If the answer is "yes", the inlet regulating mechanism is switched to the closed position as indicated at 209; otherwise, if Tr is not greater than or equal to T TL , the mechanism remains in the open position as indicated at 210 .

[0124] If decision step 204 has a "no" outcome (meaning the operating point is on the low flow side of the threshold line), decision step 212 is performed, asking Ne / Δt Is the response time Tr greater than zero (i.e., the engine is accelerating). If the answer is "no", the mechanism is closed (or remains in the closed position) as indicated at 213, because this means that the operating point is not moving towards the threshold line. If decision step 212 produces a "yes" result (i.e., the engine is accelerating), this means that the operating point is moving towards the threshold line. Therefore, a further decision step 214 is performed, asking whether the response time Tr is greater than or equal to the time required for the operating point to reach the threshold line T TL If the answer is "yes", the mechanism switches to the open position as indicated at 215; otherwise the mechanism remains closed as indicated at 216.

[0125] In the above embodiment, it is assumed that the time change rate of the engine speed ΔNe / Δt However, alternatively, the time rate of change of turbocharger speed may be used instead ΔNt / Δt Yet another alternative is to use the corrected time rate of change of compressor flow ΔWc / Δt. Similarly, based on W and engine speed Ne Or based on W and turbocharger speed Nt Determine the location of the operating point on the graph.

[0126] Many modifications and other embodiments of the invention described herein will come to mind to those skilled in the art having the benefit of the foregoing description and the teachings presented in the associated drawings. Therefore, it should be understood that the invention is not limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A method for controlling a compressor inlet regulating mechanism, the compressor inlet regulating mechanism being arranged in an air inlet of a centrifugal compressor of a turbocharger so as to increase an intake pressure of an internal combustion engine, the inlet regulating mechanism being actuatable to switch between a closed position for reducing a flow area of ​​the air inlet and an open position for increasing a flow area of ​​the air inlet, the method comprising: identifying a threshold line on a compressor map of the relationship between the pressure ratio PR and the corrected flow rate Wc of the compressor, the threshold line being a line at which the inlet regulating mechanism moves from the open position to the closed position when the operating point of the compressor on the compressor map reaches the threshold line starting from the high flow side of the threshold line under the condition of quasi-static movement of the operating point; tracking movement of an operating point of the compressor on the compressor map by sensing at periodic time intervals; determining at each of the time intervals whether the operating point is on the high flow side of the threshold line or on the low flow side of the threshold line; determining at each of the time intervals whether the operating point is moving toward the threshold line; as well as When the operating point is determined to be on the high flow side of the threshold line and is moving toward the threshold line, actuation of the inlet regulating mechanism is initiated to switch from the open position to the closed position, wherein the actuation begins before the operating point reaches the threshold line.

2. The method according to claim 1, further comprising: When the operating point is determined to be on the low flow side of the threshold line and is moving toward the threshold line, actuation of the inlet regulating mechanism is initiated to switch from the closed position to the open position before the operating point reaches the threshold line.

3. The method according to claim 2, further comprising: identifying a high switching line on the compressor map, the high switching line spaced apart from the threshold line on the high flow side of the threshold line; identifying a low switching line on the compressor map, the low switching line spaced apart from the threshold line on the low flow side of the threshold line; and Wherein, the step of initiating actuation of the inlet regulating mechanism to switch from the open position to the closed position and vice versa is based in part on the position of the operating point relative to the high switching line and relative to the low switching line, respectively.

4. The method according to claim 3, wherein: The step of determining whether the operating point is moving toward the threshold line includes calculating a time rate of change ΔNt / Δt of the speed of the turbocharger and using the time rate of change together with the result of the step of determining whether the operating point is on the high flow side of the threshold line or on the low flow side of the threshold line.

5. The method according to claim 3, wherein: The step of determining whether the operating point is moving toward the threshold line includes calculating the time rate of change ΔNe / Δt of the speed of the internal combustion engine and using the time rate of change together with the result of the step of determining whether the operating point is on the high flow side of the threshold line or on the low flow side of the threshold line.

6. The method according to claim 3, wherein: The high switching line is spaced apart from the threshold line by an amount based on a response time Tr required to move the inlet regulating mechanism from the open position to the closed position.

7. The method according to claim 6, wherein: The low switching line is spaced apart from the threshold line by an amount based on a response time Tr required to move the inlet regulating mechanism from the closed position to the open position.

8. The method according to claim 2, further comprising: At each of the time intervals, calculating a time rate of change ΔNe / Δt of the engine speed; At each of the time intervals, calculating a distance D between the operating point on the compressor map and the threshold line; At each of the time intervals, the time period T that the operating point will take to reach the threshold line is calculated based on the distance D and the time change rate ΔNe / Δt. TL ; as well as At each of the time intervals, in the time period T TL comparing with a known response time Tr of the inlet regulating mechanism to transition between the open position and the closed position; Therein, the step of initiating activation of the inlet regulating mechanism is performed based on the comparison.

9. The method according to claim 8, wherein: The step of starting the actuation of the inlet regulating mechanism is performed during the time period T TL It is implemented when it is equal to the response time Tr.

10. The method according to claim 2, further comprising: At each of the time intervals, calculating a time rate of change ΔNt / Δt of the speed of the turbocharger; At each of the time intervals, calculating a distance D between the operating point on the compressor map and the threshold line; At each of the time intervals, the time period T that the operating point will take to reach the threshold line is calculated based on the distance D and the time change rate ΔNt / Δt. TL ; as well as At each of the time intervals, in the time period T TL comparing with a known response time Tr of the inlet regulating mechanism to transition between the open position and the closed position; Therein, the step of initiating activation of the inlet regulating mechanism is performed based on the comparison.

11. The method according to claim 10, wherein: The step of starting the actuation of the inlet regulating mechanism is performed during the time period T TL It is implemented when it is equal to the response time Tr.

12. The method according to claim 2, further comprising: At each of the time intervals, calculating a time change rate ΔWc / Δt of the flow rate of the compressor; At each of the time intervals, calculating a distance D between the operating point on the compressor map and the threshold line; At each of the time intervals, the time period T that the operating point will take to reach the threshold line is calculated based on the distance D and the time change rate ΔWc / Δt. TL ; as well as At each of the time intervals, in the time period T TL comparing with a known response time Tr of the inlet regulating mechanism to transition between the open position and the closed position; Therein, the step of initiating activation of the inlet regulating mechanism is performed based on the comparison.

13. The method according to claim 12, wherein: The step of starting the actuation of the inlet regulating mechanism is performed during the time period T TL It is implemented when it is equal to the response time Tr.

14. A computer program product comprising at least one computer-readable storage medium storing computer-executable program code instructions for controlling a compressor inlet regulating mechanism disposed in an air inlet of a centrifugal compressor of a turbocharger according to the method of any one of the preceding claims so as to increase the intake pressure of an internal combustion engine.

Images