Staged Boost Control for Compressor Surge Mitigation
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Solution Overview
Problem
Engine systems with boosting devices, such as turbochargers and superchargers, face issues with compressor surge, leading to noise and performance degradation, particularly during throttle tip-out conditions, where reduced flow causes surge and degrades turbocharger performance.
Innovation Solution
The method involves using a staged boosting system where an electric supercharger is operated upstream of a turbocharger, increasing pressure at the turbocharger compressor inlet during throttle reduction to move the compressor ratio away from the surge threshold, thereby reducing the need for a compressor recirculation valve and mitigating surge without degrading engine performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a compressor recirculation valve is used to mitigate surge, then surge is reduced, but device complexity and system cost increase
Solution Approach 1:
The patent extracts the surge mitigation function from the downstream compressor recirculation valve and transfers it to the upstream compressor. By controlling the upstream compressor to maintain pressure ratio above the surge threshold, the need for a complex recirculation valve system is eliminated, reducing device complexity while maintaining surge mitigation capability
Solution Approach 2:
The upstream compressor performs preliminary action by maintaining pressure ratio above the surge threshold before surge can occur. This proactive control approach prevents surge conditions from developing in the downstream compressor, eliminating the need for reactive recirculation valve intervention
2Ease of manufacture
If compressor recirculation valve size is reduced to lower cost, then system cost decreases, but surge mitigation capability is degraded
Solution Approach 1:
The patent removes the requirement for a large recirculation valve by extracting the surge mitigation function to the upstream compressor. This eliminates the need to manufacture and install expensive, large-capacity recirculation valves, reducing system cost while maintaining or improving surge mitigation through upstream pressure control
3Reliability
If the second compressor is accelerated during throttle reduction, then surge is mitigated by maintaining pressure ratio, but energy consumption increases
Solution Approach 1:
The upstream compressor performs preliminary action by maintaining pressure ratio above the surge threshold during transient conditions. This proactive control prevents surge and the associated NVH issues, justifying the temporary energy consumption as a trade-off for avoiding more severe operational problems
Solution Approach 2:
The second compressor is accelerated periodically or transiently only when needed during throttle reduction events, rather than operating continuously. This on-demand operation minimizes energy consumption while providing surge mitigation precisely when the downstream compressor is at risk
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach extends the surge-free operating regime, potentially reducing the size or eliminating the need for a compressor recirculation valve, improving engine performance and reducing system costs by maintaining boosted engine performance while minimizing surge occurrences.
Implementation Method 1
accelerating the second compressor and reducing the flow of compressed air to the engine
Implementation Method 2
increasing pressure at the turbocharger compressor inlet
Data Source
AI summary
Methods and systems are provided for surge control in an engine system having multiple staged charge boosting devices. In one example, responsive to a drop in driver torque demand, compressed air is continued to be provided by operating a downstream intake compressor while accelerating an upstream compressor to reduce flow through the first compressor. By increasing the compressor pressure ratio at the first compressor via operation of the second compressor, surge is reduced without degrading boosted engine performance.