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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 The measured octane numbers are shown to be similar to the limited data acquired using the now withdrawn Motor (LP) test method (ASTM D2623).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.

This paper extends previous development of the ALSI concept, by investigating the performance delivered with a turbocharged version of this engine. The research is based on extensive experimental research with lean burn, high compression ratio engines using hydrogen, LPG, CNG and gasoline fuels. It also builds on recent experience with highly boosted spark ignition gasoline and LPG engines and single cylinder engine research used extensively for model calibration. The final experimental foundation is the wide ranging evaluation of jet assisted ignition that generally allows a lean limit mixture shift of more than one unit of lambda with consequential benefits of improved thermal efficiency and close to zero NOx. The paper describes the capability of the ultra lean burn spark ignition engine with the mild boost needed provided by a Honeywell turbocharger.

Cyclic variability in spark ignition engine combustion, especially at high dilution through lean burn or high EGR rates, places limits on in-cylinder NOx reduction and thermal efficiency. Flame wrinkling, resulting from interactions with turbulence, is a potential source of cyclic variations in turbulence. Previous studies have shown that flame kernels are subject to significant distortions when they are smaller than the integral length scale of turbulence. With the assumption that flame development is not subject to noticeable variations, after it reaches the integral length scale, the authors have shown that turbulent-burning-caused combustion variability can be successfully modeled as a function of laminar flame speed and turbulence intensity. This paper explores the contributions of flame wrinkling to flame kernel growth variation. As the kernel growth problem is complex, this study only explores one of the many aspects of the problem.

The minimisation of tail-pipe emissions and fuel consumption during cold-start can be viewed as a constrained optimisation problem involving many parameters. Examining this problem mathematically first requires an accurate and computationally practical model of the engine and exhaust system. This paper proposes such a model for use during the cold-start of a conventional spark ignition engine. This model uses as much physics-based modelling as is computationally practical for optimisation and control studies. It takes a given set of engine control inputs to simulate tailpipe CO , HC and NO emissions, and is both calibrated and validated using detailed measurements obtained on a transient engine dynamometer following the New European Drive Cycle (NEDC).

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.