Premixed Compression Ignition Engine Combustion Noise Reduction
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Solution Overview
Problem
In premixed compression ignition engine systems, rapid combustion at high engine loads leads to increased combustion noise, while slowing down combustion improves stability but compromises noise reduction, and early fuel injection risks abnormal combustion due to heat loss through chamber walls.
Innovation Solution
The engine system employs two separate fuel injections and a water injection between them to cool the surrounding space, delaying the ignition of the fuel-air mixture in the surrounding space, ensuring a time lag between central and surrounding space ignitions, thus reducing noise and stabilizing combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuel is injected at an early timing to avoid smoke and improve fuel efficiency, then mixing of fuel and air is sufficient and fuel efficiency improves, but the fuel-air mixture in the surrounding space is subjected to abnormal combustion and pre-ignition is likely to be caused
Solution Approach 1:
The combustion chamber is divided into central space and surrounding space, with separate fuel injection timings for each region. The central space receives early fuel injection for stable combustion, while the surrounding space receives delayed fuel injection to avoid pre-ignition and reduce combustion noise.
Solution Approach 2:
Different fuel injection timings are applied to different spatial regions within the combustion chamber. The central region uses early injection timing optimized for stability, while the surrounding region uses late injection timing optimized for noise reduction, creating locally optimized combustion conditions.
2Power
If compression-ignition combustion proceeds rapidly with increase in engine load, then power output increases, but the pressure in the cylinder sharply elevates which increases combustion noise
Solution Approach 1:
Fuel injection is divided into multiple periodic stages with different timings for different spatial regions. The central space combusts first, followed by the surrounding space, creating a staged combustion process that controls pressure rise rate and reduces combustion noise while maintaining power output.
3Object-generated harmful factors
If the fuel-air mixture in the surrounding space is ignited in a delayed manner to reduce combustion noise, then combustion noise is reduced, but the fuel-air mixture may be subjected to abnormal combustion due to extended exposure to high-temperature environment
Solution Approach 1:
The central space fuel-air mixture is ignited first as a preliminary action, creating a controlled ignition source that initiates combustion before the surrounding space mixture is ignited. This staged approach ensures stable combustion progression while maintaining delayed ignition in the surrounding space for noise reduction.
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 configuration effectively reduces combustion noise and enhances stability by maintaining ignitability while delaying the ignition of the surrounding space fuel-air mixture, preventing pre-ignition and improving thermal efficiency.
Implementation Method 1
applies water to the surface of the cavity of the piston, whereby a water film is formed on the surface
Implementation Method 2
This water film is capable of keeping combustion heat from being dissipated through the crown top surface of the piston
Implementation Method 3
the formed fuel-air mixture is ignited by compression and burnt at around the compression top dead center
Implementation Method 4
the first fuel injection causes the fuel injector to inject fuel to form a fuel-air mixture in the surrounding space of the combustion chamber
Data Source
AI summary
A premixed compression ignition engine system includes an engine, a fuel injector, a water injector, and a controller. The controller conducts: a compression-stroke mid-period injection that causes a fuel injector to inject fuel to form a fuel-air mixture in a surrounding space of a combustion chamber; a compression top-dead-center injection that causes the fuel injector to inject fuel to form a fuel-air mixture in the central space of the combustion chamber after the compression-stroke mid-period injection; and a water injection that causes a water injector to inject water to the surrounding space of the combustion chamber at a timing from commencement of the compression-stroke mid-period injection to commencement of the compression top-dead-center injection.