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A variable compression ratio concept that can give a different expansion ratio to the compression ratio has been evaluated by means of a simulation of a turbocharged diesel engine. The VR/LE mechanism kinematics have been defined and described, and the compression ratio and expansion ratio have been presented as a function of the eccentric phase angle (αo). A zero-dimensional engine simulation that has been the subject of comprehensive validation, has been used as the basis of the VR/LE study. The effect of the compression ratio on the engine performance at fixed loads is presented. The principal benefits are a reduction in fuel consumption at part load of about 2%, and a reduction in ignition delay that leads to an estimated 6 dB reduction in combustion noise. The study has been conducted within the assumption of a maximum cylinder pressure of 160 bar.

An experimental investigation of the PJC (Pulsed Jet Combustion) system in a research engine is presented. The modus operandi is based on the introduction into the combustion chamber of a turbulent plume formed by a jet of rich combustion products issued from an orifice of a generator plug. This study is a continuation of previous investigations performed with the use of, sequentially, a constant volume vessel and a single compression machine. The PJC generator was supplied with a rich mixture via a Bosch injector. Methane was used as a fuel. Pressure records of a piezo-electric transducer were processed by a computer data acquisition system. The investigations were performed for lean combustible mixtures (ϕ=0.625, 1.0) over a wide range of spark advance angles. Direct comparison between the PJC system and conventional spark ignition was made for optimal ignition advance angle.