Engine Piston Cavity Fuel Injection Control
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Solution Overview
Problem
Existing diesel engine technologies face challenges in reducing soot emission while maintaining fuel efficiency, as advancing the post injection timing to improve torque and thermal efficiency leads to locally high fuel concentrations and new soot generation issues.
Innovation Solution
A control system for the engine that includes a piston with a cavity and a fuel injector, where the first injection occurs near the top dead center for torque generation, and a second injection is performed after the first injection has flowed back, with the fuel injector injecting fuel toward the cavity at a timing when the fuel is offset from the injection axis to avoid mixing and stimulate soot oxidation, thereby reducing soot emission and improving fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the post injection timing is advanced to increase engine torque and improve thermal efficiency, then fuel efficiency is improved, but the interval between main injection and post injection becomes shorter causing locally high fuel concentration and new soot generation
Solution Approach 1:
The fuel injection is divided into two separate injections: a main injection that contributes to torque generation, and a post injection that targets soot oxidation. By segmenting the injection timing and purpose, the system can optimize each injection's function independently, allowing the post injection to occur at an advanced timing that improves fuel efficiency without causing excessive soot generation from a single large injection event
Solution Approach 2:
The invention changes the timing parameter of the post injection to occur at an advanced crank angle position (e.g., 10-20 degrees after top dead center) rather than the conventional later timing. This parameter change allows the post injection to contribute to torque generation while the controlled injection quantity prevents locally high fuel concentration and soot formation
2Object-generated harmful factors
If the post injection is performed on expansion stroke when piston descends from top dead center, then soot emission is reduced through oxidation, but fuel efficiency deteriorates as the fuel does not contribute much to engine torque
Solution Approach 1:
The post injection is performed at an advanced timing before the piston fully descends from top dead center, rather than waiting for the expansion stroke. This preliminary action allows the injected fuel to contribute to torque generation during the power stroke while still providing soot oxidation benefits, thus improving fuel efficiency without compromising emission reduction
3Use of energy by moving object
If the interval between main injection and post injection is shortened to improve thermal efficiency, then fuel efficiency is improved, but locally high fuel concentration occurs causing soot generation
Solution Approach 1:
The post injection uses a controlled, relatively small quantity of fuel compared to the main injection. This partial action approach allows the post injection to occur at an advanced timing that improves thermal efficiency, while the limited fuel quantity prevents locally high concentration and subsequent soot generation
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 soot emission and improves fuel efficiency by avoiding locally high fuel concentrations and stimulating soot oxidation, while ensuring the second injection contributes to engine torque generation.
Implementation Method 1
the fuel flows from the fuel injector toward the cavity along the injection axis; collides with an inner surface of the cavity; then flows back toward the fuel injector along the inner surface of the cavity
Implementation Method 2
The fuel of the first injection may partially start to combust at the timing of flowing back
Implementation Method 3
by performing the second injection, oxidation of soot generated as the fuel of the first injection combusts is stimulated, and therefore, soot emission is reduced
Data Source
AI summary
A control system of an engine is provided, which includes a piston formed with a cavity and configured to reciprocate in a cylinder along a center axis of the cylinder, and a fuel injector disposed facing a top surface of the piston and configured to inject fuel along an injection axis. When the piston is located near a top dead center of compression stroke, the fuel injector performs a first injection so that the fuel flows from the fuel injector toward the cavity along the injection axis, collides with an inner surface of the cavity, then flows back toward the fuel injector along the inner surface of the cavity from a position offset from the injection axis. The fuel injector performs a second injection toward the cavity at a timing after the first injection and at which the fuel of the first injection flows back.