Method for estimating efficiency loss of a turbocharger of an engine

Abstract

The present invention relates to improvements in turbocharger efficiency, and more specifically, to a method and system for estimating efficiency loss of a turbocharger. The method comprises the steps of monitoring a plurality of operating parameters and determining a compressor outlet temperature according to a first calibration map based on the operating parameters. Then, an estimate of a transient turbocharger efficiency loss is determined according to a second calibration map based on the compressor outlet temperature. The transient turbocharger efficiency loss is used to determine an estimate of a cumulative turbocharger efficiency loss during engine service. The estimate of the cumulative turbocharger efficiency loss is compared to a first predetermined efficiency loss threshold, and a first signal is generated if the first predetermined efficiency loss threshold is exceeded.

Description

Technical Field

[0001] The present invention relates to improvements in turbocharger efficiency and, more particularly, to methods and systems for estimating efficiency losses of turbochargers. Background Art

[0002] An internal combustion engine is supplied with a mixture of air and fuel for combustion in the engine to generate mechanical power. In order to maximize the power generated by this combustion process, the engine is often equipped with a turbocharged fluid (usually air) intake system, generally referred to as a turbocharger. An internal combustion engine can thus include one or more turbochargers for compressing a fluid that will be supplied to one or more combustion chambers in a corresponding combustion cylinder. Each turbocharger typically includes a turbine driven by exhaust gas from the engine and a compressor driven by the turbine. The compressor receives the fluid to be compressed and supplies the compressed fluid to the combustion chamber. The fluid compressed by the compressor can be in the form of combustion air only, or can be a mixture of fuel and combustion air. By using a turbocharger, the power that can be obtained from an engine of a given size can be significantly improved.

[0003] Engines that may be exposed to high ambient temperatures and / or continuous operation at high duty cycles may experience an increase in turbocharger compressor temperature. As the temperature inside the turbocharger increases, the turbocharger speed can no longer be increased effectively, which may lead to a decrease in engine performance. Although internal combustion engines can be designed with open or closed snorkel systems, most use closed snorkel systems today, which may lead to additional fouling problems. During the compression and power strokes of an internal combustion engine, the pressure difference of the gas above and below the piston may be sufficient to cause leakage of gas through the piston into the engine crankcase (blow-by). The resulting increase in crankcase pressure may force the oil (vapor or liquid) to pass through the engine oil seals, and this pressure may also damage the oil seals and thus cause further leakage of the oil. In order to reduce the destructive effects of blow-by, the crankcase pressure is usually relieved by venting the snorkel gases to the atmosphere via an open snorkel, or by connecting the crankcase to the engine intake system so that the snorkel gases are delivered to the engine combustion chamber via the engine intake system and under the control of a pressure regulating device. This latter system constitutes a closed-circuit snorkel system.

[0004] In a breather system, it is desirable to include a means to retrieve the oil contained in the breather gas and return it to the engine lubricating oil sump for reuse. Otherwise, the entrained oil may cause contamination and, in a closed loop system, fouling of the turbocharger compressor blades, engine poppet valves, and other components that come in contact with the intake air.

[0005] In addition to potentially causing pollution and emissions problems, carryover oil in the breather tube gases may reduce the amount of oil available for engine lubrication and cooling requirements. It is desirable to minimize oil carryover, and an oil / air separator may therefore be included in most closed circuit breather tube systems.

[0006] Current internal combustion engines typically have closed circuit snorkel separators that operate at 80%-90% efficiency. At elevated temperatures, and especially when operating at elevated temperatures for extended periods of time, residual oil can burn onto the compressor impeller, causing fouling. Such fouling can result in a significant reduction in turbocharging efficiency and therefore engine performance. In the worst case, compressor seizure and component failures have been observed during durability validation. Currently, such fouling cannot be measured by existing engine sensors, and detection of any problems due to fouling relies on a full service program.

[0007] US-B-7801660 discloses a system for estimating the effect of compressor fouling in a power plant. The system includes a control unit that communicates with one or more monitoring devices and receives current performance data. The control unit includes program logic that calculates the fouling of the compressor and the recoverable effect on the fuel consumption of the combined cycle power plant based on the recoverable effect on efficiency.

[0008] It is an object of the present invention to provide a method and a system for estimating efficiency loss of a turbocharger due to compressor fouling. Summary of the invention

[0009] Embodiments of the present invention provide methods and systems for addressing efficiency loss of a turbocharger due to compressor fouling while the turbocharger is in service and providing warnings and / or controlling the turbocharger if the efficiency loss drops below a threshold.

[0010] In an embodiment of the present invention, the efficiency loss of an engine turbocharger during service in an engine is monitored by measuring a plurality of operating parameters of the turbocharger. These parameters are calibrated using a map to process the compressor outlet temperature. The compressor outlet temperature is then correlated with another calibration Figure 1The turbocharger calibration map is used to process an estimate of transient turbocharger efficiency loss according to a second calibration map. The transient turbocharger efficiency loss is processed to determine an estimate of cumulative turbocharger efficiency loss during engine service, and the cumulative turbocharger efficiency loss can be compared to a first predetermined efficiency loss threshold. If the cumulative turbocharger efficiency loss exceeds the first predetermined efficiency loss threshold, a signal is generated, and the signal can generate a warning and / or be communicated to a controller to control the operation of the turbocharger. The signal / warning can prescribe maintenance of the turbocharger, and the controller can control the turbocharger to operate in a safe state until maintenance can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic diagram of a system for estimating efficiency loss of a turbocharger according to the present invention;

[0012] Figure 2 is a graph showing turbocharger efficiency loss versus compressor outlet temperature; and

[0013] Figure 3 It shows that the estimated Figure 1 The system uses the steps of a method for reducing the efficiency loss of a turbocharger. DETAILED DESCRIPTION

[0014] In an embodiment of the present invention, the operation of the turbocharger is monitored in order to maintain the efficiency of the turbocharger and prevent damage to the turbocharger. In order to maintain and protect the turbocharger, when the turbocharger is in service in the engine, the efficiency loss of the turbocharger is processed in real time. The efficiency loss is processed by monitoring the operating parameters of the turbocharger and using a calibration map to determine the compressor outlet temperature based on the operating parameters of the turbocharger. The estimate of the instantaneous turbocharger efficiency loss is found from the second calibration map using the determined compressor outlet temperature. The instantaneous turbocharger efficiency loss is used to determine the estimate of the cumulative turbocharger efficiency loss during the engine service. The estimate of the cumulative turbocharger efficiency loss is compared with a predetermined efficiency loss threshold, and if the predetermined efficiency loss threshold is exceeded, a warning signal is generated and / or the turbocharger is controlled to prevent damage. The detection of the cumulative turbocharger efficiency loss exceeding the predetermined efficiency loss threshold can be used to make a maintenance decision about the turbocharger and / or control the turbocharger / engine to operate in a safe state until the service is provided.

[0015] refer to Figure 1 , showing the suitability for operation Figure 3Schematic diagram of a system 10 for a method for estimating efficiency loss of a turbocharger 11 illustrated in and disclosed herein. The system 10 may include a turbocharger 11 for an engine 16. The turbocharger 11 may be mounted within a turbocharger housing 12. The turbocharger 11 may include a compressor wheel 13 and a turbine wheel 14, which may be connected in a known manner via a shaft 15. A fluid (typically air) may circulate through the turbocharger 11 and the engine 16 via a fluid conduit 17. The turbocharger housing 12 may include a compressor inlet 18, a compressor outlet 19, a turbine inlet 20, and a turbine outlet 21. The system 10 may include a plurality of sensors for monitoring various parameters to be used in estimating efficiency loss of the turbocharger 11. These sensors may include:

[0016] - Air pressure sensor 22, which can measure the air pressure (P bar ), which may be mounted on the electronic control module 30 (described in detail below);

[0017] - An engine speed sensor 24 , which may be positioned within the engine 16 in a conventional manner, which may measure the engine speed (Ω). The engine speed sensor 24 may be a crank speed sensor or other suitable type of sensor that monitors the position or speed of the crankshaft;

[0018] A compressor inlet temperature sensor 26 which can measure the temperature (T amb ), which may be attached to the turbocharger housing 12 or may be positioned at another point within one of the fluid conduits 17 upstream of the compressor inlet 18; and

[0019] -NO x The sensor 27 may be a sensor for measuring the NOx (nitrogen oxide) concentration (NOx con ) and may be located in the exhaust pipe (not shown) of a vehicle utilizing system 10 .

[0020] The system 10 may include an electronic control module 30 (also referred to as an ECU or ECM) connected to the engine 16. The electronic control module 25 may perform several functions, including monitoring the performance of the engine 16 and the turbocharger 11. The electronic control module 30 may be part of a main control system (not shown) of a machine or vehicle in which the system 10 is installed, which monitors and controls other functions of the machine or vehicle and the engine 16. Alternatively, it may also be a separate module. The electronic control module 30 may include a memory and a processing unit, the memory may store instructions or algorithms in the form of data, and the processing unit may include software configured to perform operations based on instructions. The memory may include any suitable computer-accessible storage medium or non-transitory storage medium for storing computer program instructions, such as RAM, SDRAM, DDR, SDRAM, RDRAM, SRAM, ROM, magnetic media, optical media, etc. The processing unit may include any suitable processor capable of executing instructions stored in the memory, such as a microprocessor, a single processor, a multiprocessor, etc.

[0021] The electronic control module 30 may also include a service hour meter that measures the engine operating time for each period to determine the engine service life (t engine ), which is the total number of hours that the engine 16 has been running during its life.

[0022] Air pressure sensor 22, engine speed sensor 24, compressor inlet temperature sensor 26 and NO x The sensor 27 can provide the electronic control module 30 with the parameters of air pressure (P bar ), engine speed (Ω), ambient temperature of intake air (T amb ) and the concentration of nitrogen oxides (C nox The communication line 28 may be hardwired or wireless.

[0023] In addition, another parameter, the fuel injection amount (V i ) can be determined by the electronic control module 30. The injection of fuel can be controlled by the electronic control module 30, and the fuel injection amount (V i ) can be determined by the amount of fuel delivered and the injection duration.

[0024] Calibration maps (also referred to as performance maps, and which may include fuel maps, efficiency maps, and consumption maps) may be used to represent the expected performance of the engine 16 and turbocharger 11 under different combinations of loads and operating conditions. Such calibration maps may enable certain output parameters to be predicted (determined) based on certain input parameters in situations where certain parameters cannot be measured or are difficult to measure. The electronic control module 30 may thus include a memory configured to store such engine performance maps, and may continuously use the input parameters along with data from the engine performance maps to determine other parameters used in the turbocharger efficiency loss estimation method.

[0025] In the present system 10, the electronic control module 30 may store a compressor outlet temperature map 31, which may be used in the method for estimating the efficiency loss of the turbocharger 11 to provide an estimate of the compressor outlet temperature (T exit ), which is the temperature of the fluid at the compressor outlet 19. The compressor outlet temperature may be difficult to measure directly, so the method uses the compressor outlet temperature map 31 based on the pressure sensor 22, the engine speed sensor 24, the compressor inlet temperature sensor 26 and the NO x The engine speed (Ω), air pressure (P bar ) and ambient temperature (T amb ) and the amount of fuel (V) as determined by the electronic control module 30 to determine the compressor outlet temperature (T exit ). An adjustable low pass filter may be used to smooth inputs due to engine transients. The compressor outlet temperature graph 31 may be compiled using empirically derived off-line data, simulation data, and / or operational test data.

[0026] The compressor outlet temperature (T exit ) may be used as an input parameter to a compressor fouling damage icon 32, which may also be stored in the electronic control module 30. The compressor fouling damage icon 32 may provide an estimate of the transient turbocharger efficiency loss percentage (TEL i ) to the input compressor outlet temperature (T e The compressor fouling damage icon 32 may also be compiled using empirically derived offline data, and Figure 2 The output is plotted. The lowest compressor outlet temperature (T exitmin) can be determined from the simulation, and this temperature can be set as the starting point of the gradient. The simulation can be used to show that there is a linear increase in the percentage of compressor fouling, so that in the worst case scenario, the time it takes to reach the fouling rate threshold is of concern. In addition, the maximum safe operating temperature for the engine 16 may also be known or predicted, and this temperature can be used to set the maximum compressor outlet temperature (T) at the end of the gradient. exitmax ). Therefore, using test data and modeling, the transient turbocharger efficiency loss (TEL i ) over time (i.e., the current operating time) can be expressed relative to the input compressor outlet temperature (T e )draw.

[0027] The electronic control module 30 can use the transient turbocharger efficiency loss percentage (TELi) to determine the turbocharger 11 over the engine life (t engine ) in the cumulative turbocharger efficiency loss percentage (TEL c This can be achieved by calculating the engine life (t engine ) in the instantaneous efficiency loss (TEL i ) is integrated to calculate the cumulative turbocharger efficiency loss percentage (TEL c ) may be stored in non-volatile memory of the electronic control module 30 and may be updated periodically, such as each time the engine 16 is shut down (off) or after a predetermined operating period. If the engine level analysis shows that operation under certain operating conditions results in fouling recovery and therefore efficiency improvement and is limited to an overall range of 0% to 100%, the integrator may be designed to allow for both increment and decrement accumulation.

[0028] When the electronic control module 30 is powered on, the integral should be initialized to the previously stored cumulative turbocharger efficiency loss percentage (TEL c ), and then in subsequent power cycles, the integral should be accumulated from this point onwards.

[0029] The cumulative turbocharger efficiency loss percentage (TEL) indicates the overall decrease in turbocharger efficiency. c ) can be compared to one or more predetermined efficiency loss thresholds, and if a threshold is exceeded, a signal can be generated. The signal can trigger an alarm, which can be displayed or communicated to an operator, service team, or dealer. In this example, there are 2 threshold levels:

[0030] -Level 1 Efficiency Loss Threshold (TEL thresh1) can be set at a level where the estimated efficiency loss has not reached a level where immediate action should be taken because there is no imminent risk of damage due to fouling, but action is recommended at the next scheduled service. If the cumulative turbocharger efficiency loss percentage (TEL c ) exceeds the level 1 efficiency loss threshold (TEL thresh1 ), a turbocharger inefficiency level 1 event alarm (A1) may be triggered.

[0031] -Level 2 Efficiency Loss Threshold (TEL thresh2 ) may be set at a level where the estimated efficiency loss reaches a level at which immediate action should be taken because there is an imminent risk of damage to the turbocharger 11 due to compressor fouling. Such action may be to slow down the engine, which may limit power or vehicle speed, which may reduce the amount of fuel injected into the engine 16 and thereby reduce temperature, which in turn may reduce the risk of further fouling. If the cumulative turbocharger efficiency loss percentage (TEL) reaches a level at which immediate action should be taken because there is an imminent risk of damage to the turbocharger 11 due to compressor fouling. Such action may be to slow down the engine, which may limit power or vehicle speed, which may reduce the amount of fuel injected into the engine 16 and thereby reduce temperature, which in turn may reduce the risk of further fouling. c ) exceeds the level 2 efficiency loss threshold (TEL thresh2 ), a turbocharger inefficiency level 2 event alarm (A2) may be triggered.

[0032] Although in this example, there are two efficiency loss thresholds, the system 10 may have only one or more than two, each of which gives a different alarm based on exceeding the threshold.

[0033] Before issuing a turbocharger inefficiency level 2 event alarm (A2), the system 10 may determine the exhaust gas NOx concentration (NOx con ) for further inspection. NOx (or nitrogen oxides) is a chemical in automobile exhaust that is produced when the temperature inside the vehicle engine combustion chamber exceeds 1370°C. A selective catalytic reduction aftertreatment system can be used to convert NOx that may be produced into less harmful emissions, such as nitrogen and water. The selective catalytic reduction system can include a catalyst that promotes a reaction between NOx that may be present in the gas stream passing through the selective catalytic reduction system and a reductant to substantially remove NOx from the gas stream. Since the temperature of the engine 16 directly affects the NOx level, further inspection can be performed to determine if the high level of NOx is due to other factors other than compressor fouling.

[0034] NOx concentration (NOx con ) can be compared with a predetermined NOx threshold (NOx thresh ) and if the NOx concentration (NOx con ) exceeds a predetermined NOx threshold (NOx thresh), which can trigger a turbocharger inefficiency level 2 event alarm. NOx concentration (NOx con ) can be measured in parts per million (ppm), and if a predetermined NOx threshold (NOx thresh ) is set in g / kWh, the NOx concentration can be converted to grams of emissions per kilowatt-hour (g / kWh) of the engine using known formulas.

[0035] On engines with an aftertreatment system based on selective catalytic reduction and exhaust pipe NOx, NOx concentration (NOx con ) may have been directly monitored by the SCR control strategy. On an engine without a SCR based aftertreatment system and without a NOx sensor 27, the NOx estimation strategy may be used to estimate the “engine out” NOx concentration (NOx con ). In this example, the assumption is that if the turbocharger begins to foul, a reduction in turbocharger performance will be detected by the exhaust gas recirculation and total air mass flow estimates, which are inputs to the exhaust gas recirculation ratio and the burned gas fraction calculations used as inputs to the NOx estimation strategy. Since there is no selective catalytic reduction catalyst, the estimated NOx concentration out of the engine (NOx con ) will be equivalent to the NOx concentration in the exhaust pipe after the diesel oxidation catalyst and the diesel particulate filter (NOx con ). Such NOx estimation strategies may take the form of complex models, such as neural networks, and / or simpler NOx estimation lookup maps.

[0036] In the present system 10, a NOx sensor installation status sensor (not shown) may be used to determine the installation status of the NOx sensor 27, and if the NOx sensor installation status sensor determines that the NOx sensor 27 is installed, the system 10 may be directed to use the NOx concentration measured by the NOx sensor 27. If the NOx sensor installation status sensor determines that the NOx sensor 27 is not installed, the system 10 may be directed to use the NOx estimation strategy to determine an estimate of the NOx concentration.

[0037] If the NOx sensor 27 is used to provide the NOx concentration (NOx con ), and it is determined that the NOx sensor 27 is faulty, then the NOx concentration (NOx con) may be set to 0 and the turbocharger inefficiency level 2 event may be suspended from triggering until the NOx concentration reading can be trusted. If a NOx emissions map is used to provide NOx concentration, there may be inherent fault logic in the NOx emissions map that switches to an alternate NOx map estimate, and that NOx map estimate may still be used to provide NOx concentration and a turbocharger inefficiency level 2 event alarm may still be triggered.

[0038] Turbocharger Inefficiency Level 1 events can be set to occur after the cumulative turbocharger efficiency loss (TEL c ) exceeds a first predetermined efficiency loss threshold. The alarm may be programmed to be reset only after the turbocharger has been cleaned or replaced via a service tool reset function.

[0039] Turbocharger Inefficiency Level 2 events can be set to occur after the cumulative turbocharger efficiency loss (TEL c ) exceeds a second predetermined efficiency loss threshold, which is higher than the first predetermined efficiency loss threshold, and an alarm is triggered when the NOx concentration (NOx con ) was also used in additional test cases, NOx concentration (NOx con )Predetermined NOx concentration threshold (NOx thresh ) for a predetermined period of time (t nox ).

[0040] When the electronic control module 30 determines that certain operating conditions exist, such as the engine 16 is operating in an operating or fault mode with known elevated NOx conditions, the predetermined NOx concentration threshold check may be precluded. These conditions may include a fault in the exhaust gas recirculation system, which may cause the exhaust gas recirculation valve to close or stick; high temperature operating conditions with reduced exhaust gas recirculation; and aftertreatment regeneration and warm-up modes. For example, if the engine 16 is idling, the system 10 may determine that it is insignificant whether the NOx concentration is high because the fluid temperature at the compressor outlet 19 is unlikely to exceed the minimum compressor outlet temperature (T exitmin ), and the compressor is therefore unlikely to foul. Enable icon 33 can also be used to determine if any of these operating conditions exist, which can use the engine speed (Ω) and fuel injection amount (V i ) as an input parameter to this determination step. The NOx trigger may also be conditionally enabled to protect the LRC engine hardware group so that the diagnostic may be triggered in applications that do not have the ability to measure or estimate NOx. The overall event trigger may also be conditionally enabled so that the system 10 may be used on other platforms, rather than in a vehicle, for the purpose of monitoring turbocharger efficiency. The alarm may be programmed to be reset via a service tool reset function only after the turbocharger 11 has been cleaned or replaced.

[0041] The turbocharger inefficiency level 2 event alarm may also be configured to trigger an engine speed reduction procedure to protect the turbocharger 11. In this example, the speed reduction percentage may be mapped to the cumulative turbocharger efficiency loss (TEL c ) function.

[0042] Industrial Applicability

[0043] The method and system for estimating the efficiency loss of a turbocharger is particularly suitable for use in an engine 16 of a vehicle, such as an internal combustion engine, although it can be extended to other applications. Since it is impossible to detect the actual fouling of the compressor impeller 13 caused by the burning of the leftover oil onto the compressor impeller 13 when the engine 16 is in place, there is a risk that although such fouling may cause a significant decrease in turbocharging efficiency and thus engine performance, the fouling may not be considered to be the cause of such a decrease. Therefore, in many cases, compressor fouling may not be realized until a comprehensive service is performed, which may mean that the fouling may have caused greater damage than if it was detected earlier, or has caused non-compliance with emission regulations. The present method and system for estimating the efficiency loss of a turbocharger can thus predict when the fouling reaches a level at which action should be taken, whether immediately or at the next service. Depending on the severity of the estimated efficiency loss, different threshold levels can be set to generate different alarms.

[0044] The method may further provide a sanity check to ensure that the likelihood of efficiency loss is a result of fouling, rather than other systems, such as the exhaust gas recirculation system, not functioning as expected.

Claims

1. A method for estimating the efficiency loss of a turbocharger of an engine, the method comprising the following steps: Monitor multiple operating parameters; determining a compressor outlet temperature according to a first calibration map based on the plurality of operating parameters; determining an estimate of transient turbocharger efficiency loss from a second calibration map based on the compressor outlet temperature; determining an estimate of cumulative turbocharger efficiency loss during engine service using the determined instantaneous turbocharger efficiency loss; comparing the estimate of accumulated turbocharger efficiency loss to a first predetermined efficiency loss threshold and generating a first signal if the first predetermined efficiency loss threshold is exceeded; Determine NOx concentration in engine exhaust; comparing the determined NOx concentration to a predetermined NOx threshold value; as well as A second signal is provided when the determined NOx concentration exceeds the predetermined NOx threshold and the estimate of the accumulated turbocharger efficiency loss exceeds a second predetermined efficiency loss threshold that is higher than the first predetermined efficiency loss threshold.

2. The method of claim 1, further comprising: A controller is configured to control the operation of the engine and / or control the turbocharger to operate in a safe state when the first signal is generated.

3. The method of claim 1, wherein: The plurality of operating parameters include engine speed, fuel injection amount, air pressure, and ambient temperature.

4. The method according to claim 1, further comprising the steps of: determining the presence of any predetermined operating conditions from a third calibration map; as well as If any such predetermined operating conditions exist, the step of comparing the determined NOx concentration with said predetermined NOx threshold value is excluded.

5. The method of claim 4, wherein: The engine speed and the fuel injection amount are used as input parameters by the third calibration map for determining whether any predetermined operating conditions exist.

6. The method of claim 5, wherein: The predetermined operating conditions include engine operating or fault modes in which there are known elevated NOx conditions.

7. The method of claim 1, wherein: The first signal triggers a first alarm and / or a change of the engine and / or a turbocharger operation, and the second signal triggers a second alarm and / or a change of the engine and / or a turbocharger operation.

8. A system configured to implement the method for estimating efficiency loss of an engine turbocharger as claimed in claim 1, comprising: engine; Turbocharger; a plurality of sensors that monitor the plurality of operating parameters; A controller is configured to receive signals related to the plurality of operating parameters, the controller comprising a memory configured to store the first calibration map and the second calibration map, wherein the controller is configured to generate one or more of the signals.

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