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Technical Paper

Opportunities for making LPG a clean and low greenhouse emission fuel

It is shown that LPG has the potential to be a main stream fuel because of its low particulate emissions and low greenhouse emission potential. The experimental study reported is directed at minimising the cost of LPG optimised engines through the use of gas phase, throttle body injection in an engine with 11.7 compression ratio up from 9.65 of the base gasoline engine. The advantages of throttle body injection, guided by CFD studies, are extension of the lean limit to lambda 1.6, where NOx is low enough to meet Euro4 emission standards without a reducing catalyst, as deduced from bench test results. Comparison is also made between throttle body and both liquid and gas phase multipoint port injection. Differences in the method of mixing significantly affect engine performance. Notable improvements in emissions and thermal efficiencies were achieved when compared with gasoline, eg.
Technical Paper

SI Engine Lean-Limit Extension Through LPG Throttle-Body Injection for Low CO2 and NOx

This paper presents the experimental results of a new look at throttle body injection (TBI) for LPG, targeting the same objectives as fourth generation LPG systems. The TBI system is configured from CFD studies to minimize cylinder-to-cylinder air-fuel variations, enabling the lean limit to be extended as far as lambda 1.6. An in-line, six-cylinder engine with a compression ratio of 11.7:1 (up from the standard 9.65:1) over a range of speed/torque conditions was utilized, with the air/fuel ratio varied from lambda 1.2 to 1.6. Additionally, cylinder-to- cylinder air-fuel variations were measured over a range of speeds and throttle positions representing most of the steady state parts in the Euro drive-cycle for light-duty vehicles. It is shown that mixing characteristics have a considerable effect on emissions and thermal efficiency.