Gas Engine Fuel Supply Control via Turbocharger Mixer
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Solution Overview
Problem
Conventional gas engines face challenges in achieving precise air-fuel ratio control, especially when using low calorific value fuel gases that vary in calorific value, leading to potential explosion risks and the need for large, power-consuming gas compressors.
Innovation Solution
A method where a part of the fuel-gas is supplied to the engine suction air induced by the turbocharger, using a mixer to maintain a fuel-air mixture concentration below the lean limit of flammability, with the second gas valve for suction air being opened when the fuel-gas is of low calorific value or engine output is high, and closed when the fuel-gas changes to high calorific value or engine output decreases, allowing precise control through the first gas valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fuel-gas is supplied to the upstream side of air-inflow line before the turbocharger, then the fuel-gas and air are mixed and compressed through the turbocharger compressor, but the flammable air fuel-gas mixture is compressed into high temperature and high pressure causing potential gas explosion risks
Solution Approach 1:
The patent introduces a mixing section as an intermediary component between the fuel-gas supply and the turbocharger compressor. In this mixing section, fuel-gas is mixed with air to form a fuel-gas/air mixture before being supplied to the compressor, thereby preventing direct compression of flammable fuel-gas and eliminating the explosion hazard.
Solution Approach 2:
The patent changes the composition parameters of the gas mixture by introducing air into the fuel-gas stream in the mixing section. This parameter change (adding air to dilute fuel-gas) reduces the flammability of the mixture before compression, eliminating the explosion risk while maintaining the desired fuel supply function.
2Stress or pressure
If a gas compressor of large capacity is used to compress low pressure fuel-gas of low calorific value, then the fuel-gas pressure at the inlet of the cylinder can be higher than the supercharged air pressure, but the power consumption and size of the gas compressor increase
Solution Approach 1:
The patent merges the fuel-gas supply system with the air supply system by introducing fuel-gas into the air inlet passage of the turbocharger. The air stream acts as a carrier that delivers fuel-gas to the compressor inlet, allowing the existing compressor to handle the mixed gas without requiring additional compression capacity or power consumption.
Solution Approach 2:
The air stream from the air supply system serves dual purposes: it provides the necessary oxygen for combustion and simultaneously acts as a carrier gas that transports and pressurizes the fuel-gas through the turbocharger compressor, eliminating the need for a separate dedicated fuel-gas compressor.
3Manufacturing precision
If the opening level of the first gas valve and the load level of the engine are controlled to regulate fuel-gas flow rate, then the fuel-gas supply to each cylinder can be equalized, but when the first gas valve is fully opened and engine output increases, the fuel-gas flow rate becomes insufficient
Solution Approach 1:
The patent segments the fuel-gas supply control into two independent pathways: (1) the first gas valve that controls fuel-gas flow to each cylinder for uniform distribution, and (2) the second gas valve that controls fuel-gas flow to the air inlet passage for additional fuel supply. This segmentation allows each valve to operate within its optimal range without interference.
Solution Approach 2:
The patent implements partial fuel-gas supply through the second gas valve to the air inlet passage, providing additional fuel-gas flow to supplement the first gas valve. This partial action through an alternative pathway ensures sufficient total fuel-gas flow rate even when the first gas valve is fully opened and engine output increases.
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 enables high precision air-fuel ratio control, reduces the size and power consumption of the gas compressor, and minimizes fuel-gas explosion risks by ensuring the fuel-air mixture concentration remains below the flammability limit, while allowing for simple control mechanisms.
Implementation Method 1
a mixer to maintain a fuel-air mixture concentration below the lean limit of flammability
Implementation Method 2
the engine suction air induced by the turbocharger
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3(a)~3(c)
AI summary
A method to control a gas engine system is disclosed, whereby the engine can be operated with an air-fuel-ratio controlled with high precision, even in using a low calorific fuel-gas that is prone to vary in calorific value; the engine system includes: a first gas line toward each cylinder via a first gas valve from a gas supply source line, the first gas valve regulating flow rates of the fuel-gas through a gas compressor on the line; a second gas line toward suction air, the line being branched from the gas supply source line and the line being provided with a gas air mixer and a second gas valve on the line. In the case when the fuel-gas is of a low calorific value or where the output of the engine is high, a part of the fuel-gas is supplied to the engine through the first and second lines. The mixer forms a mixture of a prescribed mixing ratio that is leaner than a lower limit of flammability of the fuel-gas, while the remaining fuel-gas through the first line is supplied to the mixture just before each cylinder so that a final prescribed air fuel ratio is formed. In the case when the calorific value of the fuel-gas is high, or of high engine output, the whole fuel-gas can be supplied only through the first gas line.