JPH03275968A - Spark-ignition gas engine - Google Patents

Abstract

PURPOSE:To obtain a low NOx gas engine equipped with a supercharger capable of using low-pressure gas of a general town gas supply system by using a gas compressor driven in association with the rotary shaft of an engine to boost the pressure of a small amount of auxiliary chamber supply gas requiring supply pressure higher than charged pressure. CONSTITUTION:Combustion gas to be supplied at low pressure is guided at fixed pressure from gas feed facility 10 while being separated into a gas mixer 11 and a gas compressor 12. By the gas mixer 11 most part of the combustion gas is formed into lean mixture needed for low NOx combustion and is taken into an engine main chamber by a supercharger compressor 110b and an intake manifold 102. Auxiliary chamber supply gas that is allowed to flow through the gas compressor 12 has its pressure boosted to pressure proportional to engine speed by the gas compressor 12 which is driven in association with an engine rotary shaft and the pressure is adjusted to fixed differential pressure by a pressure governor 13 associated with inlet manifold pressure and is supplied into an auxiliary chamber through an auxiliary chamber gas valve 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to fuel gas supply for spark ignition gas engines.

[Conventional technology]

A conventional example will be described with reference to FIGS. 2 and 3.

In FIG. 3, gas fuel with a mixing ratio that is easy to ignite is formed in the subchamber 20, ignited by the spark plug 22 installed in the subchamber, and a torch is formed in the main combustion chamber by the flame ejected from the subchamber nozzle 21. , a dilute gas fuel that is normally difficult to ignite is ignited and combusted to reduce the generation of NOx. FIG. 2 is a typical example of a fuel gas supply system for a lean-burn gas engine that is supercharged by a supercharger. Fuel gas is supplied to the turbocharger compressor by gas supply equipment 10.
The pressure is regulated higher than the discharge pressure of gas mixer 110b.
1 and the subchamber gas valve 15.

The gas mixer 11 forms a lean mixture for Nox # and M, and supplies it to the main combustion chamber from the air supply manifold 102. On the other hand, fuel gas is supplied to the pre-chamber 20 through the pre-chamber gas manifold 14 and the pre-chamber gas valve 15 at a pressure higher than the pre-chamber pressure, and the lean main gas flows into the pre-chamber nozzle 21 during the compression stroke of the engine. It mixes with the air-fuel mixture in the chamber to form a gas fuel with a mixture ratio that is easy to ignite.

[Problem to be solved by the invention]

Gas engines generally use city gas as fuel and have the advantage of not requiring fuel storage. However, the gas pressure supplied by gas companies is divided into medium pressure and low pressure, and differs depending on the equipment used and the amount used. Among these, low-pressure supply systems are characterized by lower construction costs and a more complete pipe network than medium-pressure pipes.

In a supercharged gas engine, a gas supply pressure higher than the supercharger compressor discharge pressure is required, and the gas supply pressure is 1.5 kg/cm.
Either a medium-pressure gas supply or auxiliary equipment to boost the pressure of low-pressure gas is required.

An object of the present invention is to solve the problems of the conventional device and provide a low NOx gas engine equipped with a supercharger that can use low pressure gas from a city gas supply system.

[Means to solve the problem]

In the spark-ignition gas engine of the present invention, the main chamber fuel portion of the fuel gas supplied at low pressure is mixed with air in front of the supercharger, and a small sub-chamber where a supply pressure higher than the supercharging pressure is required is used. The gas to be supplied is raised and regulated by a gas compressor driven in conjunction with the rotating shaft of the engine.

The subchamber volume is 3 to 5% L less than the main chamber volume when collapsed.
Since the amount of gas to be supplied is small, the gas compressor to be driven can be small.

[For production]

In the gas engine of the present invention, most of the fuel gas is mixed with air in front of the supercharger, and a small amount of the fuel gas for the pre-chamber is kept in the gas compressor with the engine at a pressure above the pre-chamber pressure, which is approximately equal to the in-cylinder pressure. Boost the pressure and supply it.

With this configuration, ignition in the pre-chamber becomes easy, combustion of a lean air-fuel mixture using general city gas supplied at low pressure becomes possible, and a supercharged gas engine with low NoX can be realized.

〔Example〕

Embodiments of the present invention will now be described with reference to FIG.

FIG. 1 is a system diagram of a gas engine with a supercharger.

The main parts are a gas compressor 12 and a pressure regulator I3 that are driven in conjunction with the engine rotating shaft.

The fuel gas supplied at low pressure passes through the strainer and pressure regulator of the supply equipment 10, and is branched and guided to the gas mixer 11 and gas compressor [12] at a constant pressure.

Most of the fuel gas is formed into a lean mixture necessary for low NOx combustion in the gas mixer 11, and then the supercharger compressor 7
Air is supplied from the air supply manifold 102 to the J-clan main room.

On the other hand, gas compression I! The subchamber supply gas flowing into the subchamber 12 is boosted to a pressure proportional to the engine rotation speed. The amount of gas supplied to the pre-chamber is determined by the difference between the pressure in the pre-chamber gas manifold 14 and the pressure in the sub-chamber (approximately the same as the supply air pressure when supplying gas to the sub-chamber)2.Therefore, a pressure regulator 13 that is linked to the supply air manifold pressure is used. The pressure is adjusted to a constant differential pressure, and the gas is supplied into the subchamber from the subchamber gas valve 15.

With such a mechanism, an air-fuel mixture that is easily ignited by the spark plug 22 is formed in the subchamber 20,
The flame generated by ignition in the sub-chamber is ejected as a torch into the main combustion chamber from the sub-chamber nozzle 21, thereby facilitating the ignition and combustion of rare gas that is normally difficult to ignite, thereby reducing the generation of NO8. I can do it.

〔Effect of the invention〕

Since the present invention is constructed as described above, it is easy to use low-pressure gas from a city gas supply system on a boat and burn it in a lean mixture, thereby realizing a gas engine with a low NOx supercharger. can.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a gas engine with a supercharger according to a first embodiment of the present invention, Fig. 2 is a system diagram of a conventional gas engine with a supercharger, and Fig. 3 is a system diagram of a gas engine with a pre-chamber. It is a sectional view of the subchamber part of.

Claims (1)

[Claims] In a spark-ignition gas engine with a supercharger that has a subchamber in the cylinder head, a passage for auxiliary ignition gas to flow into the subchamber, and a spark plug that ignites the flame in the subchamber to form a torch into the main combustion chamber. , a means for mixing most of the low-pressure gas fuel supplied to the main combustion chamber with air in a gas mixer in front of the supercharger, and a gas compressor driven by the engine's rotating shaft for supplying part of the fuel gas to the auxiliary chamber. A spark ignition gas engine comprising means for increasing the pressure in the engine and supplying a constant differential pressure higher than the pre-chamber pressure.