Stationary Gas Engine Speed Control via Air Ratio Limiting
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Solution Overview
Problem
Existing automatic control systems for stationary gas engines face challenges in maintaining a stable air-fuel mixture during dynamic load changes, leading to potential mixture enrichment, excessive component stress, and poor exhaust gas values due to sluggish response times and overshooting correcting variables.
Innovation Solution
A method that computes a speed control deviation to determine a set torque, which is limited by an air ratio limit torque, and uses this limited torque to calculate a set volume flow for determining both the mixture throttle angle and gas throttle angle, preventing mixture enrichment by setting the air ratio limit torque based on a minimum lambda value and actual mixture volume, and incorporating a torque limiter to manage sensor failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the mixture throttle is adjusted to change power output, then the power output changes, but the response time becomes sluggish and the mixture becomes too rich
Solution Approach 1:
The control system is segmented into two independent control paths: a fast lambda control path that adjusts the gas throttle to maintain air-fuel ratio, and a power control path that adjusts the mixture throttle to change power output. This segmentation allows each control path to operate independently without interfering with the other, enabling fast response in both lambda maintenance and power adjustment.
Solution Approach 2:
The gas throttle acts as an intermediary control element that mediates between the lambda controller and the power output requirement. When power changes are needed, the mixture throttle adjusts while the gas throttle is simultaneously adjusted by the lambda controller to maintain proper air-fuel ratio, preventing mixture enrichment during transient states.
2Stability of the object's composition
If the gas throttle is adjusted to maintain lambda value, then the air-fuel ratio is maintained, but the correcting variables overshoot during dynamic load changes
Solution Approach 1:
The control system dynamically adapts the gas throttle position based on the operating state. During transient load changes, the lambda controller actively adjusts the gas throttle to compensate for mixture throttle movements, maintaining stable air-fuel ratio. The system transitions from static throttle positioning to dynamic coordinated control, preventing overshooting of correcting variables.
3Productivity
If the mixture throttle is moved in the closing direction to enrich the mixture, then the power output changes, but impermissible mixture enrichment occurs causing excessive component stress
Solution Approach 1:
The lambda controller provides continuous feedback on the air-fuel ratio and actively adjusts the gas throttle to maintain the lambda value within permissible limits. This feedback mechanism prevents impermissible mixture enrichment by detecting lambda deviations and correcting them through gas throttle adjustment, thereby preventing excessive component stress while allowing power output changes through mixture throttle adjustment.
Data Source
AI summary
The invention relates to a method for regulating a stationary gas motor (1). In said method, a deviation of the regulated speed is calculated from a desired speed and an actual speed, a desired moment is determined as an adjustable variable from the deviation of the regulated speed by means of a speed governor, said desired moment being limited to an air ratio-limiting moment by limiting the moment, and a desired volume flow (VSL) is determined from the limited desired moment in order to define an angle (DKW1, DKW2) of the mixture throttle valve and an angle of the gas throttle valve.