The performance characteristics of a hydrogen-fuelled free piston internal combustion engine and linear generator system

A power generation system that utilizes a hydrogen-fuelled free piston engine (FPICE) and a linear generator are under development. A FPICE gives power output more efficiently compared with conventional reciprocating piston engines, because it utilizes many benefits such as low friction loss and inherently variable compression ratio apart from the low emission of hazardous exhaust gases. In addition, if hydrogen fuel is used in an FPICE, it would be possible to make the exhaust emission level almost zero without sacrificing the efficiency. In this study, a prototype FPICE, two-stroke twin-cylinder engine, was developed and a linear generation system was incorporated in between the cylinders to get the electricity and the start of the engine, as well. It was possible to operate the engine at a velocity of 17 Hz. The FPICE was found to give different piston positions at top dead centre, and this irregular piston movement affected significantly both the compression process and the subsequent combustion of the other cylinder of the engine at the same time. Both compressed natural gas and hydrogen were used to the test engine, and the results showed different combustion characteristics with the fuels used. Since the scavenging efficiency easily gets worse in such a low-speed operation of the two-stroke engines, hydrogen fuel has been found to give higher burn rate and resultantly to show improvements in power output and the emissions. Copyright The Author 2009. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org, Oxford University Press.