System and method for turbocharger compressor surge control

An internal combustion engine having intake and exhaust manifolds, a turbocharger with a compressor, and at least one of: an exhaust gas recirculation (EGR) valve and a variable geometry turbine (VGT). The system further includes a control computer configured to determine at least one of torque demand, pressure across the compressor, and pressure gradient ratio between the exhaust manifold and the intake manifold relative to one of exhaust manifold pressure, intake manifold pressure, and 1. The control computer performs at least one of: closing the EGR valve in response to the determined at least one of torque demand, pressure across the compressor, and pressure gradient ratio, and lessening restriction provided by the variable geometry turbine responsive to the determined at least one of torque demand, pressure across the compressor, and pressure gradient between the exhaust manifold and the intake manifold.

FIELD OF THE DISCLOSURE

The present invention relates generally to systems for controlling turbocharged internal combustion engines, and more specifically to systems for controlling turbocharger compressor surge.

BACKGROUND

Turbocharging machinery is well-known and commonly used in the internal combustion engine industry to pressurize intake air entering the engine combustion chambers and thereby increase the efficiency and power output of the engine. In general, pressurizing the intake air increases the quantity of air entering the engine cylinders during the intake stroke, and this allows more fuel to be utilized in establishing a desired air/fuel ratio. Increased available engine output torque and power thereby results.

Conventional turbochargers for internal combustion engines include a turbine disposed in the path of exhaust gas exiting the engine exhaust manifold, wherein the turbine typically includes a wheel that is rotated via the flow of exhaust gas thereby. The turbine wheel is rotatably coupled to a wheel of a compressor disposed in-line with the air intake system of the engine. Rotation of the turbine by the exhaust gas flow causes the compressor wheel to likewise rotate, wherein rotation of the compressor wheel acts to increase the flow of fresh air to, and consequently the air pressure within, the air intake system. Generally, the rotational speed of the turbocharger turbine and compressor wheels, and hence the air pressure within the air intake system, is proportional to the flow rate of exhaust gas, which is itself proportional to engine speed.

In the operation of turbochargers of the type just described, a condition known as turbocharger compressor surge is known to occur under certain engine and air handling system operation. Generally, turbocharger compressor surge occurs when the accumulated pressure in the intake manifold (downstream of the compressor) exceeds the ability of the compressor to sustain positive air movement (i.e. the intake manifold pressure downstream of the compressor is so great that the compressor lacks sufficient power to compress more air into the intake manifold). This causes significant resistance to the rotational motion of the vanes of the compressor. The compressor then effectively “stalls out” and stops (or significantly slows) or even reverses air being pumped in by the compressor (i.e. surge). As a result, high vibration, temperature increases, undesired noise, and rapid changes in axial thrust can occur. These occurrences can damage the rotor seals, rotor bearings, the compressor driver and cycle operation. When this occurs, intake manifold air pressure decreases by an amount generally proportional to the intensity of the surge condition. Light compressor surge that produces an audible sound is also called compressor “chuff.”

A number of engine and air handling system conditions contribute to, and define, turbocharger compressor surge including, for example, engine speed, engine fueling rate, turbocharger speed, mass flow rate of intake air, intake manifold pressure, intake manifold volume, intake manifold temperature, and the like. In engines including exhaust gas recirculation systems, another engine operating parameter that impacts and defines turbocharger compressor surge is the flow rate of exhaust gas recirculated to the intake manifold, which affects the mass flow rate of intake air and intake manifold pressure.

What is therefore needed is a system for monitoring conditions that are indicative of surge, and then taking affirmative steps to prevent the onset of surge.

DETAILED DESCRIPTION

Briefly, in one example, a system for controlling turbocharger compressor surge is provided. The system includes an internal combustion engine having intake and exhaust manifolds. The system also has a turbocharger with a compressor that has an inlet fluidly coupled to ambient and an outlet fluidly coupled to the intake manifold. The system further includes at least one of: an exhaust gas recirculation (EGR) valve and a variable geometry turbine (VGT). The EGR valve disposed in-line with an EGR conduit fluidly coupled between said intake and exhaust manifolds, said EGR valve responsive to an EGR valve control signal to control exhaust gas flow therethrough. The VGT fluidly coupled to the exhaust manifold the VGT responsive to a VGT control signal to control the geometry thereof. The system further includes a control computer configured to determine at least one of torque demand, pressure across the compressor, and pressure gradient between the exhaust manifold and the intake manifold. The control computer performs at least one of: closing the EGR valve in response to the determined at least one of torque demand, pressure across the compressor, and pressure gradient between the exhaust manifold and the intake manifold, and lessening restriction provided by the variable geometry turbine responsive to the determined at least one of torque demand, pressure across the compressor, and pressure gradient between the exhaust manifold and the intake manifold.

In another example, a method of operating a turbocharger compressor is provided including determining at least one of torque demand, pressure across the compressor, and pressure gradient between an exhaust manifold and an intake manifold of an engine coupled to the compressor; and performing at least one of: closing an EGR valve of the engine in response to the determined at least one of torque demand, pressure across the compressor, and pressure gradient between the exhaust manifold and the intake manifold and lessening a restriction provided by a variable restrictor turbine that is in-line with an exhaust manifold responsively to the determined at least one of torque demand, pressure across the compressor, and pressure gradient between the exhaust manifold and the intake manifold.

In yet another example, a non-transitory computer-readable media having instructions thereon for controlling operation of an engine is provided. The instructions, when interpreted by a processor, cause the processor to: determine at least one of torque demand, pressure across the compressor, and pressure gradient between an exhaust manifold and an intake manifold of an engine coupled to the compressor; and emit at least one signal operative to perform at least one of: close an EGR valve of the engine in response to the determined at least one of torque demand, pressure across the compressor, and pressure gradient between the exhaust manifold and the intake manifold, and lessen a restriction provided by a variable restrictor turbine that is in-line with an exhaust manifold responsively to the determined at least one of torque demand, pressure across the compressor, and pressure gradient between the exhaust manifold and the intake manifold.

In another example, an engine control unit is provided including a first input operable to receive a signal indicative of at least one of torque demand, pressure across the compressor, and pressure gradient between the exhaust manifold and the intake manifold; a processor operable to generate at least one signal of: an EGR valve signal instructing closure of the EGR valve in response to the determined at least one of torque demand, pressure across the compressor, and pressure gradient between the exhaust manifold and the intake manifold; and a VGT signal instructing lessening of a restriction provided by a variable restrictor turbine that is in-line with an exhaust manifold responsively to the determined at least one of torque demand, pressure across the compressor, and pressure gradient between the exhaust manifold and the intake manifold. The engine control unit further including a first output operable to output the generated at least one signal.

Referring now toFIG. 1, a diagram of one illustrative embodiment of a system10for controlling turbocharger compressor surge in a turbocharged internal combustion engine is shown. System10includes an internal combustion engine12having an intake manifold14fluidly coupled to an outlet of a compressor16of a turbocharger18via an intake conduit20, wherein the compressor16includes a compressor inlet coupled to an intake conduit22for receiving fresh ambient air therefrom. Optionally, as shown in phantom inFIG. 1, system10may include an intake air cooler24of known construction disposed in-line with intake conduit20between the turbocharger compressor16and the intake manifold14. Further optionally, as shown in phantom inFIG. 1, system10may include an intake charge valve25disposed in-line with intake conduit20between the turbocharger compressor16and the intake manifold14. The turbocharger compressor16is mechanically and rotatably coupled to a variable geometry turbocharger turbine26via a drive shaft28, wherein turbine26includes a turbine inlet fluidly coupled to an exhaust manifold30of engine12via an exhaust conduit32, and further includes a turbine outlet fluidly coupled to ambient via an exhaust conduit34. An EGR valve36is disposed in-line with an EGR conduit38fluidly coupled at one end to the intake conduit20and an opposite end to the exhaust conduit32, and an EGR cooler40of known construction may optionally be disposed in-line with EGR conduit38between EGR valve36and intake conduit20as shown in phantom inFIG. 1.

System10includes a control computer42that is generally operable to control and manage the overall operation of engine12. Control computer42includes a memory unit45as well as a number of inputs and outputs for interfacing with various sensors and systems coupled to engine12. Control computer42is, in one embodiment, microprocessor-based and may be a known control unit sometimes referred to as an electronic or engine control module (ECM), electronic or engine control unit (ECU) or the like, or may alternatively be a general purpose control circuit capable of operation as will be described hereinafter. In any case, control computer42includes one or more control algorithms, as will be described in greater detail hereinafter, for controlling turbocharger compressor surge.

Control computer42includes a number of inputs for receiving signals from various sensors or sensing systems associated with system10. For example, system10includes an engine speed sensor48electrically connected to an engine speed input, ES, of control computer42via signal path50. Engine speed sensor48is operable to sense rotational speed of the engine12and produce a corresponding engine speed signal on signal path50indicative of engine rotational speed. In one embodiment, sensor48is a Hall effect sensor operable to determine engine speed by sensing passage thereby of a number of equi-angularly spaced teeth formed on a gear or tone wheel. Alternatively, engine speed sensor48may be any other known sensor operable as just described including, but not limited to, a variable reluctance sensor or the like.

System10further includes a compressor inlet pressure sensor53disposed in fluid communication with the fresh air intake conduit22adjacent to the fresh air inlet of the compressor16and electrically connected to a compressor inlet pressure input, CIP, of control computer42via signal path55. Pressure sensor53may be of known construction, and is operable to produce a pressure signal on signal path55indicative of the pressure of fresh air entering the inlet of the compressor16. Embodiments are envisioned where CIP is not measured, but rather estimated based on a signal indicating ambient air pressure from an ambient air pressure sensor (not shown). Indeed, whereas many values are discussed herein as being measured by a sensor or otherwise, embodiments are envisioned where such values are estimated from other values rather than being directly measured.

System10further includes a compressor outlet pressure sensor49disposed in fluid communication with the manifold intake conduit20adjacent to the air outlet of the compressor16and electrically connected to a compressor outlet pressure input, COP, of control computer42via signal path51. Pressure sensor49may be of known construction, and is operable to produce a pressure signal on signal path51indicative of the pressure of charged air exiting the outlet of the compressor16. Embodiments are envisioned where COP is not measured, but rather estimated based on other sensor readings (also called a virtual sensor).

System10further includes an intake manifold pressure sensor52disposed in fluid communication with intake manifold14and electrically connected to an intake manifold pressure input, IMP, of control computer42via signal path54. Alternatively, pressure sensor52may be disposed in fluid communication with intake conduit20. In any case, pressure sensor52may be of known construction, and is operable to produce a pressure signal on signal path54indicative of the pressure within intake conduit20and intake manifold14. Embodiments are envisioned where IMP is not measured, but rather estimated based on other sensor readings (a “virtual sensor”).

System10further includes a differential pressure sensor, or ΔP sensor,60fluidly coupled at one end to EGR conduit38adjacent to an exhaust gas inlet of EGR valve36, and fluidly coupled at its opposite end to EGR conduit38adjacent to an exhaust gas outlet of EGR valve36, via bypass conduit62. Alternatively, the ΔP sensor60may be coupled across another flow restriction mechanism disposed in-line with EGR conduit38. In any case, the ΔP sensor60may be of known construction and is electrically connected to a ΔP input of control computer42via signal path64. The ΔP sensor60is operable to provide a differential pressure signal on signal path64indicative of the pressure differential across EGR valve36or other flow restriction mechanism as just described. Embodiments are envisioned where ΔP sensor60provides a signal from which EGR flow can be estimated. Still further, embodiments are envisioned where fresh air flow is measured and/or estimated via a fresh air flow sensor (not shown) or otherwise rather than EGR flow.

System10may further optionally include an engine exhaust pressure sensor74disposed in fluid communication with exhaust conduit32and electrically connected to an engine exhaust pressure input, EMP, of control computer42via signal path76, as shown in phantom inFIG. 1. Alternatively, sensor74may be disposed in direct communication with the exhaust manifold30. In either case, pressure sensor74is operable to provide a pressure signal on signal path76indicative of the pressure of exhaust gas produced by engine12. It should be appreciated that exhaust pressure sensor74is optional in view of the intake manifold pressure sensor52and the differential pressure sensor60. One of skill in the art recognizes that exhaust manifold pressure, or a rough estimation thereof, can be determined from the combination of the intake manifold pressure and the change in pressure across the EGR valve. Thus, in some embodiments, intake manifold pressure sensor52and exhaust manifold pressure sensor74are provided and differential pressure sensor60is optional. In such systems, the differential pressure is able to be determined by comparing IMP and EMP.

Control computer42also includes a number of other inputs. One such input is an indication of torque demand, TD via path47. In one embodiment, TD is a signal indicative of a throttle position, such as a gas pedal. In one embodiment, a fueling command, FC, is used as an indication of torque demand. It should be appreciated that control computer42, as discussed below, generates the fuel command, FC. Regardless, control computer42receives an indication of torque demand, from either an external (outside of control computer42) or internal (inside of control computer42) source, block400,500,FIG. 4. Still further, in another embodiment, engine speed, via engine speed sensor48, is used as an indication of torque demand, TD. Embodiments are envisioned where engine speed from engine speed sensor48is used, prior to and after filtering to remove noise or other signal impurities.

Control computer42also includes a number of outputs for controlling one or more engine functions associated with system10. For example, EGR valve36includes an EGR valve actuator78electrically connected to an EGR valve control output, EGRC, of control computer42via signal path80. Control computer42is operable to produce an EGR valve control signal on signal path80, and actuator78is responsive to the EGR valve control signal to control the position of EGR valve36relative to a reference position in a known manner. Control computer42is accordingly operable to control EGR valve36in a known manner to selectively provide a flow of recirculated exhaust gas from exhaust manifold30to intake manifold14. EGR valve36further includes an EGR position sensor66electrically connected to an EGR valve position input, EGRP, of control computer42via signal path68. Sensor66may be of known construction and is operable to determine a position of EGR valve36by determining a position of EGR valve actuator78relative to a reference actuator position, and producing a position signal on signal path68indicative of the position of EGR valve36relative to a reference position. Intake charge valve25includes an intake valve actuator27, electrically connected to an intake valve control output, IVC, of control computer42via signal path72. Control computer42is operable to produce an intake valve control signal on signal path72, and actuator29is responsive to the intake valve control signal to control the position of intake valve25relative to a reference position in a known manner. Control computer42is accordingly operable to control intake valve25, when present, in a known manner to adjust a flow gas into intake manifold14. Intake valve25further includes an intake valve position sensor31electrically connected to an intake valve position input, IVP, of control computer42via signal path46. Sensor31may be of known construction and is operable to determine a position of intake valve25by determining a position of intake valve actuator29relative to a reference actuator position, and producing a position signal on signal path46indicative of the position of intake valve25relative to a reference position.

System10further includes a variable geometry turbocharger (VGT) mechanism, shown generally as82, and electrically connected to a VGT control output, VGTC, of control computer42via signal path84. The VGT mechanism82may be embodied as any combination of a mechanical or electromechanical mechanism controllable in a known manner to modify the effective geometry of the turbocharger turbine26, a wastegate disposed between conduits32and34and controllable in a known manner to selectively route exhaust gas around the turbine26and an exhaust throttle disposed in-line with either of conduits32and34and controllable in a known manner to selectively restrict exhaust gas flow through conduits32and34and turbine26. Control computer42is accordingly operable to control any one or more of these VGT mechanisms in a known manner to selectively control the swallowing capacity and/or efficiency of the turbocharger18.

System10further includes a fuel system86electrically connected to a fuel command output, FC, of control computer42via a number, K, of signal paths88wherein K may be any positive integer. Fuel system86is responsive to fueling commands, FC, produced by control computer42to supply fuel to engine12in a known manner.

Referring now toFIG. 2, a block diagram of one illustrative configuration of some of the internal features of the control computer42ofFIG. 1, as they relate to controlling turbocharger compressor surge, is shown. Control computer42includes a fueling determination block102receiving as inputs a number of engine operating condition values, EOC, including, for example, engine speed and other engine operating parameters, as is known in the art. Block102is responsive to the number of engine operating condition values, EOC, to determine a number of fueling parameters, including a mass fuel flow rate value and a start-of-fuel injection timing value, and to compute the fueling command, FC, as a function of these various fueling parameters, all in a manner well known in the art. The fueling determination block102is operable to provide the fueling command, FC, on signal path88, and the fueling system86is responsive to the fueling command, FC, to supply fuel to engine12as described hereinabove. In some embodiments, FC is also provided to torque demand, cross-compressor pressure, and cross-engine pressure estimation block100as a value indicative of torque demand, TD, on path47.

Torque demand, cross-compressor pressure, and cross-engine pressure estimation block100has an engine speed input, ES, receiving the engine speed signal on signal path50, an intake manifold pressure input, IMP, receiving the intake manifold pressure signal on signal path54, a delta pressure input, ΔP, receiving the delta pressure signal on signal path64, an exhaust manifold pressure input, EMP, receiving the exhaust manifold pressure signal on signal path76, and a torque demand signal (as previously noted, FC and/or ES may serve as a torque demand signal) on path47(or50). As shown previously noted, only two of IMP, ΔP, and EMP are needed. Accordingly, embodiments are envisioned where one or more of the three is omitted. Block100further receives compressor intake pressure input, CIP, on signal path55and compressor outlet pressure, COP, on signal path51. The torque demand, cross-compressor pressure, and cross-engine pressure estimation block100is operable, as will be more fully described hereinafter, to estimate and/or measure torque demand trend, TDT, to estimate and/or measure a ratio of the input and output pressures for the compressor, CPR, and to estimate and/or measure the pressure difference across the engine and compare it to the IMP, ΔP/P, and provide these values at outputs, TDT, CPR, ΔP/P, of block100.

Control computer42further includes a compressor surge limiting logic block104having inputs receiving the torque demand trend, TD, and compressor input/output ratio, CPR, and pressure difference across the engine, ΔP/P, values from logic block100. It should be appreciated that while certain inputs are described as going to block100and being processed prior to being provided to block104, certain embodiments are envisioned where the functions of each of blocks100,104are combined into a single block and/or certain functionalities are shared and/or moved between the two blocks. The groupings of various functionalities in blocks is meant to be exemplary only and not limiting. In one embodiment, the compressor surge limiting logic block104is configured, as will be described in greater detail hereinafter, to produce one or more output signals, as a function of at least some of its input variables for controlling one or more of VGT mechanism82, EGR valve36, and intake valve25. In one embodiment, the compressor surge limiting logic block104is configured, as will be described in greater detail hereinafter, to produce a compressor surge limiting parameter, CSLP, as a function of at least some of its input variables. CSLP is output to turbocharger control logic block110, intake valve mechanism control logic107, and EGR valve position logic block112.

Control computer42further includes an air handling command logic block108producing a commanded EGR fraction value, CEGRFR, corresponding to a desired EGR fraction, wherein the EGR fraction is the fractional amount of recirculated exhaust gas in the charge air supplied to the intake manifold14. The charge air supplied to the intake manifold14is generally understood to be a combination of fresh air supplied to the intake manifold14via compressor16and recirculated exhaust gas provided to the intake manifold14via EGR valve36. Logic block108may additionally be configured to produce other command values, as illustrated in phantom inFIG. 2. In one embodiment, logic block108is configured to produce the commanded EGR fraction value, CEGRFR, as a function of ambient air temperature, engine speed and coolant temperature. Alternatively, the air handling command logic block108may be configured to produce at least the commanded EGR fraction value, CEGRFR, in any known manner as a function of one or more engine and/or air handling system operating conditions. Air handling command logic block108further provides output signals to turbocharger control logic block110, and intake valve mechanism control logic107.

Control computer42further includes a turbocharger control logic block110having a compressor surge limiting parameter input, CSLP, receiving the compressor surge limiting parameter, CSLP, from logic block104. The turbocharger control logic block110is configured to limit and/or override the commanded variable geometry turbocharger command (received from air handling command logic block108), VGTC, as a function of the compressor surge limiting parameter, CSLP, and to produce a correspondingly limited and/or overridden commanded turbocharger geometry setting, VGTC.

Control computer42further includes a EGR valve position logic block112having a compressor surge limiting parameter input, CSLP, receiving the compressor surge limiting parameter, CSLP, from logic block104, the EGR valve position signal, EGRP, via path68, and another input receiving the commanded EGR fraction value, CEGRFR, produced by the air handling command logic block108. As it relates to the EGR fraction command, CEGRFR, produced by block108, the EGR valve position logic block112is operable to control the position of the EGR valve36via a corresponding EGR value control signal, EGRC, that is based on CEGRFR to control the position of the EGR valve36so that the flow rate of exhaust gas therethrough is controlled as discussed below. The EGR valve position logic block112is configured to limit and/or override the commanded EGR fraction command, CEGRFR, as a function of the compressor surge limiting parameter, CSLP, and to produce a correspondingly limited and/or overridden commanded EGR fraction setting

Control computer42further includes intake valve mechanism control logic107. Intake valve mechanism control logic107receives CSLP input from compressor surge limiting logic104block (as well as inputs regarding normal operation of intake valve25from air handling command logic block108and regarding valve position, IVP, via path46) and outputs a control signal, IVC, on path72.

In operation, as depicted inFIG. 3, the torque demand, compressor pressure and cross-engine pressure estimation logic block100is operable to measure and/or determine, as a function of current engine operating condition, the rate of change in torque demand, the ratio of the pressure at the compressor input to the pressure at the compressor outlet, and the change in pressure across the engine. As previously noted, logic block100receives TD on path47. Block100uses TD to calculate a rate of change of TD (ΔTD), block300. This value is then output on path302to block104.

Block100further receives COP on path51and receives CIP on path55. Block100uses COP and CIP to calculate the ratio of COP to CIP (COP/CIP, CPR), block320,FIG. 3; block410,510,FIG. 4. This value is then output on path304to block104.

Block100also receives one or more of ΔP/P on path64, EMP on path76, an IMP on path54. All such signals are shown in the figures as being received by block100,FIG. 3shows “OR” logic block340in phantom to represent that there are multiple ways that ΔP/P can be determined, block420,520,FIG. 4. Logic block340is not indicating that an OR logic chip or its equivalent is present and responsive to the shown signals. If necessary, block100determines ΔP/P by calculating (EMP-IMP)/IMP, block330. In other embodiments, ΔP and IMP are used, block310. ΔP/P signal is output by block100to block104via path306.

Block104receives TDT (ΔTD) on path302, CPR (COP/CIP) signal on path304, and ΔP/P signal on path306. Block104determines if TDT (ΔTD) is less than a threshold (ΔTD)TH, at block350. Accordingly, block104determines if the torque demand is dropping quickly. As a generalization, reduced torque demand is expected to slow the engine's intake of air and thus provides an increased likelihood of buildup of compressed air at the intake manifold. Furthermore, a quick dropoff in such demand is especially prone to such a buildup. The output of the comparison of the (ΔTD) to the (ΔTD)THis illustratively a binary one that is either high or low. However, embodiments are envisioned where the output is a scaled value such that the degree/severity of the (ΔTD) can be considered by block104.

Block104also determines if the CPR (COP/CIP) value is greater than a threshold (COP/CIP)TH, block360. Accordingly, block104determines if the pressure gain across the compressor is relatively high. As previously noted, COP is the pressure against which the compressor is pushing. CIP is a pressure that is, at least somewhat, aiding the movement of the vanes of the compressor. More accurately, the difference in pressure across the compressor is the force resisting movement of the compressor. Too great of a relative pressure gradient across the compressor stresses the compressor and provides conditions that may permit surge and/or chuff.

Block104also determines if ΔP/P is greater than a threshold ΔP/PTH, block370. As stated elsewhere, ΔP is EMP-IMP. IMP is the pressure that compressor16is pumping against. IMP is further the pressure that is available to pump through engine12. Accordingly, a high pressure gradient between EMP and IMP relative to IMP, EMP, or 1 is indicative of relatively high resistance engine pumping and reduces the pumping efficiency of the overall signal.

Block104checks CPR and ΔP/P and if CPR, ΔP/P or both meet the stated conditions relative to their thresholds (to check if engine pressure conditions, compressor pressure conditions, or both are reached for a surge and/or chuff event to occur) and sets Pressure Condition Parameter, PCP accordingly. The AND/OR block380ofFIG. 3represents that CPR and ΔP/P can be used individually (OR logic block), or together (AND block). Block104monitors all of these conditions and if they (TDT, and at least one of CPR and ΔP/P) meet the stated condition relative to their thresholds, then CSLP signal is set to high. Overall, system10is detecting conditions that are indicative of a potentially likely near-term conditions in which surge and/or chuff can be expected. Thus, the system is somewhat predictive and then intervenes before the conditions conducive to surge and/or chuff can be created.

Upon producing a high CSLP signal, control computer42executes one or more actions to avoid surge and/or chuff. A first executable is illustrated as being executed by EGR Valve position logic block112. The first executable overrides any EGR valve commands (from air handling command logic block108or otherwise) to fully close EGR valve36, block430,530,FIG. 4. It should be appreciated that the pressure and exhaust gas in the exhaust manifold30and exhaust conduit32are what is available to drive turbocharger turbine26. Having EGR valve36open allows some of that pressure and gas to be diverted to intake conduit20and intake manifold14. Closing EGR valve36provides that all available pressure and exhaust gas is routed to turbocharger turbine26. Thus, all available gas is directed to powering turbocharger turbine26and thereby providing power to compressor16.

A second executable is executed by turbocharger control logic block110. The second executable overrides control logic for setting the variable geometry gas turbine26, block440(FIG. 4),540(FIG. 5). Accordingly, the VGTC signal on path84is set to adjust the geometry on turbine26to minimize the restriction on gas (and energy flow) through the turbine26. In one embodiment, this is achieved by removing turbo interference via setting a turbo actuator to increase flow through the turbine26. It should be appreciated that this again attempts to maximize the power provided to compressor16.

A third executable is illustrated as being executed by intake valve limiting logic107. Any closing or restriction provided by intake valve25potentially holds pressure at the compressor outlet and does not let such pressure be fully felt at the engine intake manifold14. Accordingly, intake valve25potentially provides a hindrance to engine12consuming the charge air and pressure of intake conduit20. Accordingly, upon receiving a high value of CLSP, the intake valve mechanism control logic107causes the opening, such as full opening, of intake valve25, block550,FIG. 5. Accordingly, the intake valve25is set to allow a more (or the most) efficient disposal of the compressed air in intake conduit20that compressor16is pushing against.

Overall, upon detection of conditions that are likely to cause surge and/or chuff in the immediate near term, control computer42takes actions to increase the power to compressor16and to reduce the resistance seen by compressor16. Such actions reduce the likelihood of surge and/or chuff.

The measurement and/or determination of engine conditions is a constant and iterative process. Accordingly, the conditions that give rise to the output of a high signal for CSLP are typically transient. Upon the elimination of one of the two determined conditions (ΔTD), and PCP) CSLP ceases to be a high signal and the default operations of intake valve25, EGR valve36, and turbine26are resumed.

For any value that is described herein as being measured off of engine12, it should be appreciated that such value may be estimated or calculated instead of directly measured by various ways known in the art.

The above detailed description and the examples described therein have been presented for the purposes of illustration and description only and not for limitation. For example, the operations described may be done in any suitable manner. The method steps may be done in any suitable order still providing the described operation and results. It is therefore contemplated that the present embodiments cover any and all modifications, variations or equivalents that fall within the spirit and scope of the basic underlying principles disclosed above and claimed herein.