Turbocharger Boost Pressure Control Using Open-Actuator Backpressure
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Solution Overview
Problem
Existing methods for determining the base boost pressure in internal combustion engines have moderate accuracy, leading to increased fuel consumption due to controllers operating in parallel, particularly in engines based on the Miller combustion process.
Innovation Solution
A method for determining the base boost pressure by calculating the exhaust back pressure with the turbocharger actuator in the open position, using models and maps to determine turbine and compressor speeds, and then deriving the base boost pressure based on these calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lambda probe is used to detect oxygen concentration in the exhaust gas, then the air-fuel ratio can be controlled, but the response time is insufficient for dynamic basic boost pressure determination
Solution Approach 1:
The patent performs preliminary determination of the basic boost pressure during engine operation at a specific operating point (first operating point) before actual dynamic operation. The controller stores this pre-determined basic boost pressure value and uses it during transient operations when rapid response is needed, eliminating the time delay associated with real-time oxygen concentration measurement.
Solution Approach 2:
The patent introduces an intermediary approach by using a model-based calculation method that combines measured parameters (intake air amount, engine speed, throttle opening) with stored reference data (basic boost pressure from preliminary measurement) to determine the actual boost pressure during dynamic operation, rather than relying solely on direct oxygen concentration measurement.
2Reliability
If the engine operating point is changed frequently for basic boost pressure determination, then the basic boost pressure can be updated, but the engine wear increases due to frequent operating point changes
Solution Approach 1:
The patent performs the basic boost pressure determination action in advance during normal engine operation and stores the result. This preliminary-determined value is then reused during subsequent transient operations, avoiding the need to frequently change operating points just for measurement purposes, thereby reducing engine wear while maintaining measurement reliability.
Solution Approach 2:
The controller monitors the current operating conditions and compares them with the stored basic boost pressure data. When the operating point matches or is close to the predetermined operating point, the controller uses the stored basic boost pressure value, creating a feedback mechanism that avoids unnecessary operating point changes and reduces engine wear.
3Speed
If the basic boost pressure is determined during transient operation, then the response speed improves, but the measurement accuracy decreases due to changing operating conditions
Solution Approach 1:
The patent determines the basic boost pressure during stable engine operation at a predetermined operating point where conditions are well-defined and measurable with high accuracy. This pre-measured value serves as a reference that can be quickly applied during transient operations, combining the accuracy of stable-state measurement with the speed of transient response.
Solution Approach 2:
The patent uses a partial action approach by determining the basic boost pressure at a specific predetermined operating point rather than attempting to measure it during all transient conditions. This focused measurement at optimal conditions ensures accuracy, while the stored value provides sufficient response speed for transient operations.
Data Source
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AI summary
The present invention relates to a method for determining a basic boost pressure of a gas conducting system (2) of an internal combustion engine (1) having a turbocharger (20) which has a compressor (202), a turbine (200), a shaft which connects the compressor (202) and the turbine (200), and a turbocharger actuator for varying a flow velocity through the turbine (200) or a pressure ratio across the turbine (200). The method comprises the calculation (40) of an exhaust gas back pressure in the case of an open turbocharger actuator position, wherein the flow velocity through the turbine (200) or the pressure ratio across the turbine (200) is minimum in the open turbocharger actuator position, and the determination (43) of the basic boost pressure in a manner which is dependent on the calculated exhaust gas back pressure in the case of an open turbocharger actuator position. Furthermore, the invention relates to an engine controller for carrying out a method for determining a basic boost pressure.