Compressor Surge Detection via MAF Sensor Feedback
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Solution Overview
Problem
Air charger systems face challenges in detecting compressor surge events, which can lead to inaccurate air density calculations and suboptimal fuel metering due to the limitations of manifold absolute pressure sensors, necessitating a reliable method for compressor surge detection to enable model-based air estimation.
Innovation Solution
A method for compressor surge detection involves determining the compressor pressure ratio using throttle inlet and turbocharger inlet air pressures, calculating air flow differences with a string length counter, and transitioning to a model-based air mass estimation when the sum of differences exceeds a predetermined threshold, allowing for accurate air mass per cylinder calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a manifold absolute pressure sensor is used to detect manifold pressure for air density calculation, then the system can provide fuel metering information, but the sensor cannot detect compressor surge events leading to inaccurate air density calculations
Solution Approach 1:
The patent uses the mass air flow sensor as an intermediary device to detect compressor surge events. Instead of relying on the MAP sensor alone, the system introduces the MAF sensor's flow rate measurements as a mediator to identify surge conditions through characteristic fluctuations, thereby enabling reliable surge detection while maintaining the MAP sensor's pressure measurement function
Solution Approach 2:
The system implements feedback by continuously monitoring the relationship between MAF sensor readings and calculated air density from MAP sensor data. When the MAF sensor detects flow rate fluctuations characteristic of compressor surge, the system uses this feedback to trigger a transition to surge detection mode, switching the air mass measurement source to maintain accurate fuel metering
2Productivity
If the system relies on speed density calculation for fuel metering during compressor surge, then it can continue operation, but air mass estimation accuracy deteriorates
Solution Approach 1:
The system dynamically switches between different air mass measurement strategies based on operating conditions. During normal operation, it uses speed density calculation from MAP sensor data. When compressor surge is detected through MAF sensor feedback, the system dynamically transitions to using direct MAF sensor measurements for air mass estimation, thereby maintaining both continuous operation and measurement precision across varying conditions
Data Source
AI summary
A method for compressor surge detection to enable model based air estimation includes determining if an intake air compressor pressure ratio is within a predetermined surge pressure range. Then the differences between mass air flow sensor signals measured at a start and finish of each count of a predetermined string length counter when the compressor pressure ratio is within the predetermined surge pressure range. Next, a transition is made to an air mass estimation model output signal from a mass air flow sensor signal when a sum of the air flow differences is greater than a predetermined compressor surge threshold.