Two-Stroke Engine Air-Fuel Ratio Control via Exhaust Valve Timing
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Solution Overview
Problem
In two-stroke dual-fuel engines, maintaining an appropriate air-fuel ratio during gas mode operation is challenging due to variations in intake air temperature and outlet air temperature, leading to inefficient and unstable combustion.
Innovation Solution
A two-stroke engine with an air-fuel ratio controller that calculates and adjusts the average air-fuel ratio by controlling air flow volume and exhaust valve timing, ensuring the ratio is within 1.0 to 2.5, using sensors to measure air-fuel ratios in exhaust pipes and crank angle detection for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air flow volume is increased to maintain appropriate air-fuel ratio, then combustion stability is improved, but fuel consumption increases
Solution Approach 1:
The air-fuel ratio controller continuously monitors the air-fuel ratio and adjusts the air flow volume based on real-time feedback to maintain the optimal range (1.0 to 2.5). This feedback mechanism ensures combustion stability while preventing excessive fuel consumption by dynamically optimizing air supply rather than continuously increasing it.
Solution Approach 2:
The system dynamically changes the air flow volume parameter based on operating conditions and measured air-fuel ratio deviations. By adjusting this parameter within specific ranges (1.0 to 2.5), the system achieves stable combustion without unnecessarily increasing fuel consumption, as the air flow is optimized rather than maximized.
2Productivity
If exhaust valve timing is adjusted to control air-fuel ratio, then combustion efficiency is improved, but mechanical complexity increases
Solution Approach 1:
The exhaust valve timing is made dynamically adjustable rather than fixed, allowing the system to optimize air-fuel ratio and combustion efficiency based on real-time operating conditions. This dynamic adjustment capability enables improved combustion efficiency without requiring complex mechanical mechanisms, as the timing can be modified through controlled actuation.
Solution Approach 2:
The exhaust valve serves multiple functions: exhaust gas discharge, air-fuel ratio control, and combustion efficiency optimization. By integrating air-fuel ratio control into the exhaust valve timing adjustment, the system achieves improved combustion efficiency without adding separate complex mechanisms, as the existing valve system performs multiple roles.
3Reliability
If air-fuel ratio is maintained within 1.0 to 2.5, then combustion stability is improved, but control system complexity increases
Solution Approach 1:
The air-fuel ratio controller implements a feedback control system that continuously monitors the air-fuel ratio and adjusts air flow volume to maintain it within the 1.0 to 2.5 range. This feedback mechanism provides combustion stability through automated control rather than complex manual intervention, as the system self-regulates based on measured deviations from the target range.
Solution Approach 2:
The control system performs self-adjustment by automatically modifying air flow volume based on real-time air-fuel ratio measurements. This self-service capability maintains combustion stability within the 1.0 to 2.5 range without requiring external complex control mechanisms, as the system autonomously optimizes its own operation based on sensor feedback.
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 solution maintains an appropriate air-fuel ratio, ensuring efficient and stable combustion by adjusting air flow and exhaust valve timing based on real-time measurements, improving engine performance.
Implementation Method 1
an exhaust valve actuator to open and close the exhaust valve
Implementation Method 2
an air-fuel ratio sensor to measure an air-fuel ratio of the exhaust
Implementation Method 3
one cycle of intake, compression, combustion, and exhaust is completed in each reciprocating motion of piston inside a cylinder
Implementation Method 4
a pilot injection valve to inject liquid fuel into the combustion chamber
Implementation Method 5
one cycle of intake, compression, combustion, and exhaust is completed in each reciprocating motion of piston inside a cylinder
Implementation Method 6
one cycle of intake, compression, combustion, and exhaust is completed in each reciprocating motion of piston inside a cylinder
Data Source
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AI summary
This two-stroke engine (101, 102) is capable of performing at least a gas mode operation using a flammable gas as a main fuel, and includes a plurality of cylinders (1), an exhaust valve (13) provided in each of the plurality of cylinders (1), and an air-fuel ratio controller (70, 74). At a time of the gas mode operation, the air-fuel ratio controller (70, 74) has: a function of calculating an average air-fuel ratio inside the plurality of cylinders (1), and of controlling the average air-fuel ratio by adjusting an air flow volume which is supplied to the plurality of cylinders (1); and a function of calculating an air-fuel ratio inside each cylinder (1), and of controlling the air-fuel ratio by adjusting a closing timing of the exhaust valve (13).