Mitsubishi Heavy Indus-tries has put on the market its newly developed eight cylinder in-line gas engine, the 8MACH-30G. The new unit is rated at 2.55 MW at 50 Hz, 2.45 MW at 60Hz, and boasts a claimed 45% power-generator efficiency, the highest among gas engines of this class.

MHI launched the first four models in the Mach-30G series in 2001, in 12, 14, 16 and 18 cylinders versions with outputs ranging from 3.65 to 5.75 MW. Over 60 of them have been sold to date, a demand strong enough to persuade MHI to increase gas-engine production capacity at its Kanazawa (Yokohama) plant from 36 units/year to 50, in a product area that is not from a mass production line – engines are only built to order.

This addition to MHI’s MACH-30G series slots into a gap in its gas engine offering, completing a range that runs in outputs from

280 kW to 5.75 MW.

Development of the 8MACH-30G was undertaken with two main objectives, to reduce CO2 and NOx emissions and to provide a range of engines to supply the increasing demand for distributed power sources in line with accelerated adoption of the ‘Esco’ (energy service company) business format.

The new unit incorporates much of the MHI engine technology adopted in the GSR and other Mach-30G gas engines, including its Miller cycle thin-combustion technology, and a micro-pilot fuel-injection system requiring an extremely small amount of liquid fuel for ignition. On the control side an electronically controlled common rail, enabling flexible control of fuel injection, and a knock monitoring function (M-RICS, standing for Mitsubishi real time intelligent control) using advanced sensors, have been incorporated. A 24-hour remote monitoring service by the KU customer assistance centre located within the Kanazawa plant is also provided.

M-RICS is an advanced combustion analysis and combustion control system that makes use of sensors located within each cylinder to directly measure combustion pressure, significantly reducing mis-firing caused by engine knocking.

Miller cycle engines have higher thermal efficiency because the compression ratio is lower than the expansion ratio, so less energy is used in compression. The inherently lower power density (caused by the reduction in fuel-air mixture in the cylinder) can be offset by the use of a high-efficiency turbocharger.