Auto-Ignition Engine Ignition Timing Control via Segmented Fuel Injection
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Solution Overview
Problem
Current compression-ignition engines operating in auto-ignition mode face challenges in controlling ignition timing independently of injection timing, leading to limited operating range, excessive engine noise, and poor emissions performance at high loads.
Innovation Solution
A method involving controllable intake and exhaust valve actuation systems, where a portion of the fuel charge is partially oxidized during a negative valve overlap period before the compression stroke, allowing for independent control of ignition timing by altering the composition of trapped residuals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If injection timing is retarded to control ignition timing in auto-ignition mode, then ignition timing can be controlled, but injection must be completed before ignition which limits control flexibility
Solution Approach 1:
The fuel injection process is segmented into two distinct phases: a first injection event during the compression stroke and a second injection event during the expansion stroke. This segmentation allows independent control of ignition timing (via first injection) from combustion phasing (via second injection), resolving the contradiction between timing control and control flexibility
Solution Approach 2:
The first fuel injection event occurs during the compression stroke before top dead center, preliminarily establishing the ignition timing. The second injection event during the expansion stroke then adjusts combustion phasing without affecting ignition timing, providing flexible control throughout the cycle
2Ease of operation
If EGR is increased to retard combustion at high load, then combustion timing can be retarded, but sufficient EGR cannot be inducted resulting in excessive engine noise
Solution Approach 1:
Combustion control is segmented into two independent functions: ignition timing controlled by first injection during compression, and combustion phasing controlled by second injection during expansion. This allows combustion timing to be retarded at high load through second injection without requiring excessive EGR, thereby reducing engine noise
Solution Approach 2:
The system changes the timing parameter of the second fuel injection event during the expansion stroke to control combustion phasing independently of ignition timing. This parameter change allows combustion retardation at high load without the need for high EGR rates, reducing noise while maintaining control
3Device complexity
If single injection timing is used to control both ignition and combustion, then control is simple, but operating range is limited and emissions performance is poor at high loads
Solution Approach 1:
The single injection event is segmented into two separate injection events: first during compression stroke for ignition timing control, and second during expansion stroke for combustion phasing control. This segmentation expands the operating range and improves emissions performance while maintaining relatively simple control architecture
Solution Approach 2:
The first injection event preliminarily sets the ignition timing during compression, establishing the foundation for combustion. The second injection event then fine-tunes combustion phasing independently, expanding the usable operating range without significantly increasing system complexity
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 expands the dynamic operating range of the engine, improves emissions performance, and reduces engine noise by retarding ignition timing, thereby enhancing fuel economy and emissions control.
Implementation Method 1
A portion of the fuel charge is partially oxidized by injection into the cylinder during a negative valve overlap period immediately prior to a compression stroke
Implementation Method 2
The homogeneously mixed cylinder charge auto-ignites as the cylinder charge is compressed and its temperature increases
Data Source
AI summary
A method for controlling timing of ignition of a fuel charge in a compression-ignition engine operating in a controlled auto-ignition mode wherein the engine includes controllable intake and exhaust valve actuation systems is described. The method comprises determining a preferred ignition timing for a cylinder charge and a mass of the fuel charge based upon operator torque request. A portion of the fuel charge is partially oxidized during a negative valve overlap period immediately prior to a compression stroke. Magnitude of the portion of the fuel charge is based upon the preferred ignition timing of the cylinder charge. A remainder of the fuel charge is injected into the cylinder during the compression stroke.