Gas Engine Ignition Timing Control for Turbocharged Load Response
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Solution Overview
Problem
Gas engines connected to turbochargers face challenges in improving load responsiveness while suppressing knocking, especially when no throttle valve is provided on the intake passage, as the air supply from the compressor does not increase immediately due to turbo lag, leading to potential misfire and abnormal combustion.
Innovation Solution
A method of controlling the gas engine that involves optimizing ignition timing during steady operations and adjusting fuel injection amounts based on the rate of load increase, where slower load increases allow gradual fuel injection while faster increases involve retarding ignition timing to increase the excess air ratio margin, allowing larger fuel injection volumes and improved responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fuel gas flow rate is increased to improve load responsiveness, then the engine output increases, but knocking occurs due to insufficient excess air ratio
Solution Approach 1:
The patent changes the ignition timing parameter dynamically based on the rate of load increase. During rapid load increases, ignition timing is retarded to increase the excess air ratio margin and prevent knocking. During gradual load increases, ignition timing is maintained to preserve lean burn efficiency. This parameter change resolves the contradiction by allowing fuel flow to increase while adjusting ignition timing to prevent knocking.
Solution Approach 2:
The patent implements dynamic control of ignition timing based on the rate of change of load (dP/dt). The control system continuously monitors load changes and adjusts ignition timing in real-time: retarding timing during rapid load increases and maintaining optimal timing during gradual increases. This dynamic adjustment allows the system to achieve both high load responsiveness and knocking suppression.
2Object-affected harmful factors
If ignition timing is retarded to prevent knocking during rapid load increase, then knocking is suppressed, but combustion efficiency decreases
Solution Approach 1:
The patent applies dynamic ignition timing control that adapts to the rate of load increase. Ignition timing is retarded only during rapid load increases when knocking risk is high, and maintained at optimal values during gradual load increases or steady-state operation when efficiency is paramount. This time-dependent control strategy minimizes the impact on combustion efficiency while effectively suppressing knocking.
Solution Approach 2:
The control system performs preliminary action by detecting the rate of load increase and proactively adjusting ignition timing before knocking can occur. By anticipating the knocking risk based on dP/dt threshold comparison, the system retards ignition timing in advance during rapid load increases, preventing knocking while minimizing efficiency loss through brief, targeted adjustments.
3Measurement precision
If a throttle valve is installed on the intake passage to control air flow, then air-fuel ratio control precision improves, but load responsiveness deteriorates due to turbo lag
Solution Approach 1:
The patent extracts the air flow control function from the throttle valve and transfers it to the ignition timing control system. Instead of using the throttle valve to control air flow for load response, the system maintains the throttle valve in a fully open state for maximum air flow and unobstructed response, while using ignition timing adjustment to manage combustion characteristics and prevent knocking. This separation resolves the contradiction by eliminating the throttle valve's restrictive effect on load responsiveness.
Solution Approach 2:
The patent changes the control strategy from air flow regulation (throttle valve positioning) to combustion parameter regulation (ignition timing). By maintaining the throttle valve fully open and using ignition timing as the primary control parameter during transient operations, the system achieves both rapid load response and precise combustion control, avoiding the turbo lag penalty associated with throttle valve operation.
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 enhances load responsiveness and prevents knocking by allowing larger fuel injection volumes during rapid load increases, maintaining efficiency and reducing emissions.
Implementation Method 1
a gas engine connected to a turbocharger including a compressor and a turbine
Implementation Method 2
gas engines that combust a fuel gas, such as natural gas or town gas
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A method of controlling a gas engine connected to a turbocharger including a compressor and a turbine includes: performing a knocking control operation of optimizing an ignition timing as a steady operation; and in a case where a load of the gas engine increases during the steady operation, when a degree of increase in the load is relatively small, gradually increasing an actual fuel injection amount while keeping the ignition timing, and when the degree of increase in the load is relatively great, retarding the ignition timing and then gradually increasing the actual fuel injection amount.