Direct-Injection Engine Fuel Spray Control for Cold Catalyst Activation
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Solution Overview
Problem
Direct-injection spark-ignition engines face challenges in maintaining combustion stability and efficiency, particularly during cold engine operation, as high fuel viscosity makes it difficult to consistently control fuel injection timing, leading to deterioration in combustion state and inefficient catalyst activation.
Innovation Solution
A direct-injection spark-ignition engine design featuring a multi-hole injector that injects fuel sprays obliquely downward from the roof wall surface, with a concave cavity in the piston crown surface to create a spherical combustion chamber around the spark plug, allowing for controlled fuel injection timing and enhanced fuel retention, including a first spray entering the cavity during the compression stroke and a second spray being pulled towards the cavity by negative pressure, ensuring a rich air-fuel mixture around the spark plug.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ignition timing is maximally retarded to raise exhaust gas temperature for catalyst activation, then catalyst activation is promoted, but combustion stability deteriorates
Solution Approach 1:
Fuel is preliminarily injected during the intake stroke before the compression stroke to allow the fuel to be spread over the combustion chamber. This preliminary fuel injection creates a more uniform air-fuel mixture distribution, which enables the use of retarded ignition timing while maintaining combustion stability. The preliminary action prepares the combustion chamber conditions necessary for stable combustion even with delayed ignition.
Solution Approach 2:
The invention changes the fuel injection timing parameter by dividing injection into two periods: early injection during the intake stroke and main injection during the compression stroke. This parameter change allows the engine to achieve both stable combustion and high exhaust gas temperature for catalyst activation by controlling when fuel is introduced into the combustion chamber.
2Reliability
If fuel injection timing is advanced to improve combustion stability, then combustion stability is enhanced, but exhaust gas temperature increases too slowly for early catalyst activation
Solution Approach 1:
The fuel injection process is segmented into two distinct periods: an early injection period during the intake stroke and a main injection period during the compression stroke. This segmentation allows the engine to achieve both stable combustion (through controlled early injection) and high exhaust gas temperature (through optimized main injection timing and amount), thereby resolving the contradiction between combustion stability and catalyst activation.
Solution Approach 2:
By performing preliminary fuel injection during the intake stroke, the system prepares the combustion chamber with a distributed fuel-air mixture that promotes stable combustion. This preliminary action allows the main injection to occur at an optimized timing that maximizes exhaust gas temperature for catalyst activation without compromising combustion stability.
3Measurement precision
If high pressure fuel injection is used to ensure accurate ignition timing, then ignition timing precision is improved, but fuel injection timing control becomes more difficult due to high fuel viscosity during cold operation
Solution Approach 1:
Fuel is preliminarily injected during the intake stroke before compression, allowing the fuel to be distributed throughout the combustion chamber in advance. This preliminary injection reduces the sensitivity of subsequent ignition timing to precise high-pressure injection control, as the fuel is already positioned and mixed with air. This approach mitigates the difficulty of controlling injection timing under cold, high-viscosity conditions.
Solution Approach 2:
The system changes the fuel injection parameters by using lower pressure injection during the intake stroke for preliminary fuel distribution, followed by optimized pressure control during the compression stroke. This parameter change strategy makes timing control more manageable during cold operation by avoiding the need for consistently high-pressure injection while still achieving accurate ignition timing.
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 design stabilizes combustion and promotes catalyst activation during cold engine operation while improving combustion efficiency in homogenous mode during normal engine operation by effectively holding fuel sprays around the spark plug, ensuring reliable ignition and increased exhaust gas temperature for earlier catalyst activation.
Implementation Method 1
a first spray hole adapted to form a first fuel spray in such a manner as to, after being injected, directly enter the cavity at a given timing in a later period of a compression stroke
Implementation Method 2
the cavity having a guide sub-surface provided in a part of a region thereof on a far side with respect to the injector, and allow the first fuel spray to be turned toward the combustion chamber-defining roof wall surface after entering the cavity
Implementation Method 3
allow the second fuel spray to impinge against a region of the piston crown surface located closer to the injector than the cavity, so as to cause the second fuel spray having a lowered penetration force due to the impingement to be pulled toward the cavity by a negative pressure generated in the cavity as a result of passing of the first fuel spray therethrough
Implementation Method 4
be pulled toward the cavity by a negative pressure generated in the cavity as a result of passing of the first fuel spray therethrough
Implementation Method 5
a concave cavity provided in a central region of a piston crown surface of a piston located in opposed relation to the spark plug, whereby the cavity defines a combustion chamber having a generally spherical shape with a center at an electrode of the spark plug
Implementation Method 6
effectively holding fuel sprays around the spark plug
Implementation Method 7
A direct-injection spark-ignition engine design featuring a multi-hole injector that injects fuel sprays obliquely downward from the roof wall surface
Implementation Method 8
ensuring a rich air-fuel mixture around the spark plug
Implementation Method 9
ensuring reliable ignition and increased exhaust gas temperature for earlier catalyst activation
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Disclosed is a direct-injection spark-ignition engine designed to promote catalyst activation during cold engine operation. A fuel injection timing for a fuel injection period in an compression stroke (second fuel injection period F2) is set to allow a first fuel spray Ga injected from a first spray hole 40a to enter a cavity 34 in a piston crown surface 30, and allow a second fuel spray Gb to impinge against a region of the piston crown surface 30 located closer to an injector than the cavity 34, so as to cause the second fuel spray Gb having a lowered penetration force due to the impingement to be pulled toward the cavity 34 by a negative pressure generated in the cavity 34 as a result of passing of the first fuel spray Ga therethrough, The direct-injection spark-ignition engine can maximally hold an injected fuel spray around a spark plug to reliably stabilize a combustion state in a combustion mode for promoting catalyst activation during cold engine operation, while enhancing combustion efficiency in a homogenous combustion mode during normal engine operation.