Diesel Engine Combustion Noise Control via Pilot Fuel Feedback
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Solution Overview
Problem
Diesel engines experience abnormal combustion noise due to clogged fuel injectors and aging, leading to reduced fuel injection quantities and increased vibration, which existing noise reduction methods fail to adequately address.
Innovation Solution
A combustion noise controlling method that sets target vibration values based on control variables, diagnoses combustion noise, adjusts pilot fuel quantity through feedback control, and uses wavelet transforms to measure and analyze vibration signals to maintain optimal fuel injection levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the pilot fuel quantity is increased to compensate for injector aging and clogging, then the combustion noise is reduced, but the fuel consumption increases and the emission control becomes more difficult
Solution Approach 1:
The system performs preliminary diagnosis of injector conditions by monitoring vibration signals and fuel injection quantities before abnormal combustion noise occurs. Based on this preliminary assessment, the ECU proactively adjusts pilot fuel injection timing and quantity to prevent coking and maintain optimal combustion, rather than simply increasing fuel after problems arise. This prevents energy waste while maintaining low noise levels.
Solution Approach 2:
The system continuously monitors vibration peak values, fuel injection quantities, and combustion noise levels, feeding this information back to the ECU. The ECU dynamically adjusts pilot fuel injection parameters based on this feedback to maintain optimal combustion conditions. This closed-loop control ensures fuel is injected at precise quantities and timings, reducing waste while controlling noise.
2Object-generated harmful factors
If the pilot fuel quantity is increased to maintain combustion stability, then the abnormal combustion noise is reduced, but the injection system complexity increases
Solution Approach 1:
The system uses the engine's own vibration signals and combustion characteristics as diagnostic indicators of injector health. The ECU automatically diagnoses injector clogging or aging based on changes in vibration peak values and fuel injection quantities, then self-adjusts pilot fuel injection parameters accordingly. This eliminates the need for complex external diagnostic equipment while maintaining combustion stability and reducing noise.
Solution Approach 2:
The system controls abnormal combustion noise by dynamically changing injection parameters (timing, quantity, pressure) of the pilot fuel based on diagnosed injector conditions. Rather than increasing pilot fuel quantity universally, the ECU adjusts specific parameters based on real-time feedback from vibration and injection monitoring, maintaining simplicity while effectively reducing noise.
3Loss of substance
If the fuel injection quantity is reduced due to injector clogging, then the emission decreases, but the combustion noise increases abnormally
Solution Approach 1:
The system detects reduced fuel injection quantities caused by injector clogging through vibration analysis before abnormal noise occurs. The ECU proactively compensates by adjusting pilot fuel injection parameters to maintain proper combustion conditions, preventing the abnormal noise that would result from incomplete combustion while preserving the emission reduction benefit of the reduced main injection quantity.
Solution Approach 2:
When injector clogging reduces main fuel injection quantity, the ECU compensates by changing pilot fuel injection parameters (increasing quantity, adjusting timing) to ensure complete combustion. This parameter adjustment maintains low emissions from reduced total fuel consumption while preventing abnormal noise through proper combustion conditions.
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
The method effectively reduces combustion noise by iteratively adjusting pilot fuel quantities, maintaining noise levels similar to new engines and preventing abnormal noise from injector aging or clogging, with noise levels decreasing from 154.0 dB to 144.8 dB with double pilot injection.
Implementation Method 1
a vibration signal of the engine is measured by an accelerometer mounted on a cylinder block of the engine
Implementation Method 2
the vibration signal of the engine is measured by an accelerometer mounted on a cylinder block of the engine
Implementation Method 3
the vibration signal is converted using wavelet transform
Implementation Method 4
The pilot injection involves creating a combustion condition (increasing the temperature of a combustion chamber to mix fuel and air well) before a main fuel injection
Implementation Method 5
a feedback control step of obtaining a correction value by an arithmetic operation using the target value and the vibration peak value, and controlling a pilot fuel quantity according to the correction value
Data Source
AI summary
A combustion-noise controlling method for a diesel engine includes: setting a target value for a vibration peak using one or more control variables needed for driving a vehicle, diagnosing a combustion noise of the engine based on the target value, and checking whether the diagnostic value for the combustion noise is higher than a reference value previously input to a controller. Combustion is performed depending on a result of the checking. A vibration signal of the engine is measured, and a vibration peak value depending on the measured vibration signal is obtained. A feedback control step includes obtaining a correction value by performing an arithmetic operation using the target value and the vibration peak value. A pilot fuel quantity is controlled according to the correction value.