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Many applications of liquefied petroleum gas (LPG) to commercial vehicles have used their corresponding diesel engine counterparts for their basic architecture. Here a review is made of the application to commercial vehicle operation of a robust 4 L, light-duty, 6-cylinder in-line engine produced by Ford Australia on a unique long-term production line. Since 2000 it has had a dedicated LPG pick-up truck and cab-chassis variant. A sequence of research programs has focused on optimizing this engine for low carbon dioxide (CO₂) emissions. Best results (from steady state engine maps) suggest reductions in CO₂ emissions of over 30% are possible in New European Drive Cycle (NEDC) light-duty tests compared with the base gasoline engine counterpart. This has been achieved through increasing compression ratio to 12, running lean burn (to λ = 1.6) and careful study (through CFD and bench tests) of the injected LPG-air mixing system.

This paper presents a combined experimental and numerical study of a modified Cooperative Fuel Research (CFR) engine that allows both the Research and Motor octane numbers (RON and MON) of any arbitrary Liquefied Petroleum Gas (LPG) mixture to be determined. The design of the modified engine incorporates modern hardware that enables accurate metering of different LPG mixtures, together with measurement of the in-cylinder pressure, the air-fuel ratio and the engine-out emissions. The modified CFR engine is first used to measure the octane numbers of different LPG mixtures. The measured octane numbers are shown to be similar to the limited data acquired using the now withdrawn Motor (LP) test method (ASTM D2623). The volumetric efficiency, engine-out emissions and combustion efficiency for twelve alternative LPG mixtures are then compared with equivalent data acquired with the standard CFR engine operating on a liquid fuel. Finally, the modified CFR engine is modelled using GT-Power.

A comparison is being undertaken of the performance of five identical vehicles, using alternative fuels, by the Public Works Department of Victoria. The comparison is being made in normal vehicle duty in service, over 60,000 km, and by laboratory testing. Problems encountered in vehicle conversion to alternative fuels, and in installing instrumentation, and in normal operation are described. Laboratory test results of vehicle efficiency and emissions are presented and compared. The fuels considered are petrol, diesel fuel, Liquified Petroleum Gas (LPG), and Compressed Natural Gas (CNG). An Electric powered vehicle is proposed for this trial and is described. Initial conclusions indicate favourable cost reduction in using LPG or diesel fuel compared with Petrol and CNG.

This paper presents a study from the same, spark ignition, reciprocating engine running on natural gas, hydrogen and two different synthesis gases. The effects of varying fuel composition on the engine's energy balance is examined in detail, with a particular emphasis on the lean burn performance. Closure of the First Law over the engine is achieved through the integrated use of measurement and engine simulation. This integrated approach enables validation of the heat losses from the entire engine, and in particular the in-cylinder heat losses. These analyses demonstrate high in-cylinder heat losses for the hydrogen-rich fuels relative to those for the natural gas, which is consistent with the literature. Further, they also suggest a plausible explanation for the consistently observed lean air-fuel ratio for peak thermal efficiency.