Turbocharger Controller Speed Thresholds
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Solution Overview
Problem
Variable geometry turbochargers face challenges in controlling rotational speed to prevent exceeding the endurance limit, leading to time lag and deteriorated supercharging performance, with existing fuel control methods either causing overspeed or compromising performance.
Innovation Solution
A controller for turbocharged engines sets two rotational speed thresholds, adjusting fuel injection based on the current speed relative to these thresholds to prioritize preventing overspeed or maintaining supercharging performance, with specific strategies for reducing fuel injection rates and recovery to manage turbocharger speed effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotational speed threshold of the turbine is set to be low to prevent overspeed, then the reliability is improved, but the supercharging performance deteriorates
Solution Approach 1:
The patent divides the turbine rotational speed control into two distinct segments: a first threshold (Nt1) below the endurance limit for reliable overspeed prevention, and a second threshold (Nt2) below the first threshold for performance optimization. This segmentation allows the system to operate in different control modes depending on the current speed range, resolving the contradiction between reliability and productivity.
Solution Approach 2:
The control system dynamically adjusts fuel injection strategy based on the current turbine speed relative to the two thresholds. When speed is between Nt2 and Nt1, the system prioritizes performance with moderate fuel reduction. When speed reaches Nt1, it switches to priority overspeed prevention mode with aggressive fuel reduction. This dynamic adaptation resolves the static contradiction between reliability and performance.
2Productivity
If the rotational speed threshold of the turbine is set to be high to maintain supercharging performance, then the productivity is improved, but the turbine overspeeds exceeding the endurance limit
Solution Approach 1:
The patent implements preliminary action by setting the first threshold (Nt1) below the endurance limit and the second threshold (Nt2) below the first threshold. This creates a buffer zone that allows the system to take preventive fuel reduction actions before the turbine approaches dangerous speeds, while still permitting operation at high speeds that maintain supercharging performance. The preliminary thresholds prevent overspeed before it becomes a reliability issue.
3Reliability
If fuel control is used to control turbocharger rotational speed, then the reliability is improved, but a time lag is caused in speed management
Solution Approach 1:
The control device continuously monitors turbine rotational speed and provides feedback to the fuel injection system. When the speed reaches Nt1 or Nt2, the system immediately adjusts fuel injection accordingly. This closed-loop feedback minimizes time lag by constantly comparing actual speed against thresholds and making real-time corrections, resolving the contradiction between reliable control and rapid response.
Data Source
AI summary
Disclosed is a controller for a turbocharged engine. The engine includes a supercharger configured to supercharge intake air using an exhaust gas from the engine, and including movable flaps arranged so that a boost pressure generated in an intake passage is adjustable. If a rotational speed of a turbine and compressor that constitute the supercharger has reached a first threshold lower than an endurance limit, an amount of fuel injected to the engine is reduced to a predetermined amount. If the rotational speed has reached a second threshold lower than the first threshold, the amount of fuel injected is reduced in accordance with an excess of the rotational speed over the second threshold.