Variable Geometry Compressor Transient Compensation
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Solution Overview
Problem
Variable geometry compressors in turbocharged engines face issues with compressor surge and choke, leading to noise, vibration, and harshness (NVH) due to transient disturbances in engine operating parameters, which affect fuel economy and emission control, and existing solutions like passive and active casing treatments have limitations in effectively managing these conditions.
Innovation Solution
The implementation of a method that adjusts exhaust gas recirculation (EGR) flow and turbine flow via actuators while adjusting the compressor geometry, using a combination of feedback and feedforward control signals to maintain constant engine gas flow and pressure, thereby reducing disturbances caused by compressor geometry changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If compressor geometry is adjusted to prevent surge or choke, then compressor operating range is expanded, but transient disturbances occur in engine operating parameters causing NVH and performance deterioration
Solution Approach 1:
The feedforward controller calculates expected disturbances from compressor geometry changes and adjusts EGR flow and turbine flow in advance before the disturbances occur. This preliminary action compensates for the transient effects of compressor adjustment, preventing NVH and performance deterioration while maintaining the expanded compressor operating range.
Solution Approach 2:
The feedback controller continuously monitors actual engine operating parameters and adjusts control signals to correct any residual deviations from desired setpoints. This closed-loop feedback ensures that transient disturbances are minimized and engine parameters remain stable during compressor geometry adjustments.
2Stability of the object's composition
If feedback control loop is used to maintain engine operating parameters, then parameter stability is improved, but response time is slow compared to compressor adjustment speed
Solution Approach 1:
The feedforward controller performs preliminary adjustments based on predicted disturbances from compressor geometry changes, acting before the feedback controller can respond. This eliminates the delay inherent in feedback control, matching the fast response required for compressor adjustments while maintaining parameter stability.
Solution Approach 2:
The feedforward control signal acts as an intermediary that bridges the gap between slow feedback control and fast compressor adjustments. By calculating and applying compensatory signals in advance, it enables the feedback controller to maintain stability without needing to respond as quickly.
3Stability of the object's composition
If EGR flow and turbine flow are adjusted concurrently with compressor geometry, then transient disturbances are reduced, but control system complexity increases
Solution Approach 1:
The unified feedforward and feedback control system uses sensor inputs and calculated disturbance models to automatically coordinate adjustments of EGR flow, turbine flow, and compressor geometry. This intelligent control reduces transient disturbances while managing system complexity through algorithmic coordination rather than additional physical components.
Data Source
AI summary
Methods and systems are provided for controlling a turbocharged engine. In one arrangement, a method may include concurrently adjusting an exhaust recirculation gas flow and a turbine flow while adjusting geometry of a compressor to compensate for disturbance caused by the compressor adjustment.