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TITLE Development of High Efficiency Gas Engine for Green House Gas Reduction
(Joint Program to Promote Technological Development with the Private Sectors)

RITE - YOKOHAMA KANAZAWA LABORATORY in Mitsubishi Heavy Industries Ltd.


The coal mine methane, generated in a coal dig in a coal mine, is discharged the atmosphere that about 90% of all outbreak quantities currently.
As for the methane, greenhouse effect is big, and a quantity of release as greenhouse gas of the whole world is about 500 million ton a year by CO2 conversion. This is equivalent to about 40% of total CO2 discharge a year in Japan.
Methane is one of the energy source that is clean, but, as for the coal mine methane, a concentration fluctuation is large where the methane concentration is low, so the utilization by a boiler or a gas turbine is difficult.
With a traditional spark ignition gas engine, output density (mean effective pressure) is low level as 0.6 to 0.8 MPa and have to stop the engine if the methane concentration become lower such as coal mine methane.

In this development, high efficiency and high output gas engine that can utilize coal mine methane as fuel is executing based on the lean-burn gas engine using micro-pilot ignition technology.
The development target is as follows;
Output density : higher than 1.2MPa
Thermal efficiency : higher than 35%
Suitable for methane density fluctuation of 35 to 50%.

The development was carried out by the following step.

1. Designing and manufacturing of a micro-pilot ignition type small scale single cylinder engine to investigate a fundamental combustion characteristic in coal mine methane combustion is done, and then the basic performance test of the engine is done.
2. The performance test using the small scale single cylinder engine in a coal mine methane applications is done, then the most suitable engine specification is determined.
3. Designing and manufacturing of multi cylinder prototype engine of actual engine size is done based on the single cylinder test results.
4. The inspection examination that using the prototype is done.

The design and manufacturing of a small scale single cylinder engine and performance test applied coal mine methane were carried out, and it was confirmed that coal mine methane engine is able to obtain equivalent performance to conventional natural gas engine. And, based on this test results, the prototype was manufactured.
As a result of inspection examination using prototype, it was confirmed that the aim was achieved at both points of view of performance and stability against methane fluctuation.