New cogen gas engine from MHI and Tokyo Gas shows benefits of slowing down7 February 2014
MHI and Tokyo Gas Co have jointly developed a new 1000 kW gas engine for cogeneration based on their previous 930 kW machine, but with increased engine maintenance interval due to lower speed and therefore less friction wear of the engine components
MHI and Tokyo Gas Co have jointly developed a new 1000 kW gas engine for cogeneration based on their previous 930 kW machine, but with increased engine maintenance interval due to lower speed and therefore less friction wear of the engine components. The engine speed has been reduced from 1500 rpm to 1000 rpm, but without loss of power, thanks to the use of new long-stroke pistons, which increase the piston stroke by about 20%.
In fact, use of these long-stroke pistons combined with a high-efficiency turbocharger that increases the amount of compressed fuel/air mixture supplied into the cylinders, raising the mean effective pressure by about 30%, has made it possible to increase the output to 1000 kW.
In addition, upgraded engine control technologies have enabled generating efficiency to be increased to 42.3% (LHV basis) -- said to be the "highest level in the 1 000 kW class" when compared with gas cogeneration systems of up to 1 000 kW sold by Japanese manufacturers as of 1 October 2013.
The overall thermal efficiency in CHP mode has been increased to 78.5%, a major contributor being upgrade of the one-stage intercooler used on the previous system to a two-stage intercooler system.
Reduced maintenance cost and increased efficiency greatly reduces running costs, meaning that the initial investment can be recovered approximately three years sooner than with the previous system.
In recent years, says MHI, business continuity plans and efforts to increase efficiency have resulted in growing customer interest in gas engine based cogeneration systems. The new engine is a response to this.
The lower speed increases the replacement interval for spark plugs and other consumables, with the interval for oil change and other basic maintenance extended by 1.5 times, while the minimum interval for overhaul has been extended by 1.9 times, reducing overall maintenance costs by approximately 30%.
The overall width of the engine enclosure has also been reduced, by 15% (from 3000 mm to 2500 mm), making it more suitable for indoor installations such as in hospitals and in commercial facilities. Although high-output, high-efficiency systems generally require increased ventilation and capacity for auxiliary equipment, optimal arrangement of components within the new system ensures that space requirements are no greater than that of the previous cogen system.
The basic specifications of the two systems are compared in the Table.