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This paper first compares strengths and weaknesses of different options for performing optical diagnostics on HD diesel sprays. Then, practical experiences are described with the design and operation of a constant volume test cell over a period of more than five years. In this test rig, pre-combustion of a lean gas mixture is used to generate realistic gas mixture conditions prior to fuel injection. Spray growth, vaporization are studied using Schlieren and Mie scattering experiments. The Schlieren set-up is also used for registration of light emitted by the combustion process; this can also provide information on ignition delay and on soot lift-off length. The paper further describes difficulties encountered with image processing and suggests methods on how to deal with them.

An EGR system for turbocharged (and aftercooled) heavy-duty diesel engines has been demonstrated on a 12 litre 315 kW engine with 4 valves per cylinder head and high pressure injection system. In the EGR system exhaust gas is tapped off before the turbine, run through a cooler and mixed with the intake air after the compressor and aftercooler. This is done with a minimum of disturbance to the pressure balance across the engine by combining a very efficient venturi-mixer unit with a VGT turbocharger. The venturi-mixer is positioned between the aftercooler and the intake manifold and provides a suction power to the EGR gas. Optimization of EGR quantity and injection timing reduced the NOx emission over the European 13-mode test by almost 60% to 2.4 g/kWh. Particulate emissions were 0.107 g/kWh and the BSFC penalty 2.5%. Initial tests demonstrate acceptable transient behaviour when using a dedicated control strategy.

This paper reports on an experimental study of the autoignition behaviour of an automotive gasoil on a large constant volume combustion chamber with single shot injection. In the experiments the pressure and the temperature of the air in the combustion chamber before injection varied between 30 and 70 bar and between 730 and 905 K. Illumination delay and pressure delay values have been correlated with the pressure and the temperature in the combustion chamber before injection. Based on a large number of experiments, semi-empirical two-stage ignition delay formulae are proposed that give a much better description of the fuel ignition behaviour than the classical Wolfer formula. Ignition delay values, calculated with these formulae, correlate very well with the ignition delay values of the same fuel as measured in a 260 mm bore commercial diesel engine.