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Ethanol direct injection (EDI) is a new technology to use ethanol fuel more efficiently in spark ignition engines. Fuel temperature is one of the key factors which determine the evaporation process of liquid fuel spray, and consequently influence the combustion and emission generation of the engine. To better understand the mixture formation process of the EDI spray and provide experimental data for engine modelling, experiments were conducted in a constant volume chamber in engine-like conditions. The high speed Shadowgraphy imaging technique was used to capture the ethanol spray behaviours. The experiments covered a wide range of fuel temperature, ranged from 275 K (non-evaporating) to 400 K (flash-boiling). Particularly the transition of the ethanol spray from normal-evaporating to flash-boiling was investigated.

Problems such as higher heat load in the diesel engine and the occurrence of crazes within the valve bridge of heavy-duty vehicle diesel engine should be solved, with the increase of the power density of heavy-duty vehicle diesel engine. In this paper, the heat load experiment of complete machine, temperature-measuring of bottom part of cylinder head and the three-dimension numerical simulation on coolant flow and heat transfer in the water jacket have been performed. The result shows that the main reasons of higher heat load of the engine are insufficiency of heat-sinking capability of the water-radiator and shortage of coolant flux; and the unsuitable flow field in water jacket in cylinder head, where only a little of the coolant can cool the bottom of cylinder head, is the main cause of cylinder head bottom over-heated and thermal crack in the valve-bridge region.

Pure diesel and biodiesel were tested inside a constant-volume combustion chamber which simulates the in-cylinder conditions similar to a diesel engine and is more flexible to change the engine operation boundary conditions. The ambient temperature effect on flame lift-off length for both fuels was first investigated with fixed injection pressure, duration, ambient density, and ambient oxygen concentration. This was determined from time-averaged OH chemiluminescence imaging technique. Then, the impacts of the observed lift-off length variations on oxygen ratio upstream of the lift-off location and the soot formation process were also studied. A Forward Illumination Light Extinction (FILE) soot measurement technique was adopted to study the soot formation process. The FILE technique with the capability of two-dimensional time-resolved quantitative soot measurement provides the much-needed information to investigate the soot formation mechanism.

Ethanol direct injection plus gasoline port injection (EDI+GPI) is a new technology to make the use of ethanol fuel more effective and efficient in spark ignition engines. It takes the advantages of ethanol fuel, such as its greater latent heat of vaporization than that of gasoline fuel, to enhance the charge cooling effect and consequently to increase the compression ratio and improve the engine thermal efficiency. Experimental investigation has shown improvement in the performance of a single cylinder spark ignition engine equipped with EDI+GPI. It was inferred that the charge cooling enhanced by EDI played an important role. To investigate it, a CFD model has been developed for the experimentally tested engine. The Eulerian-Lagrangian approach and Discrete Droplet Model were used to model the evolution of the fuel sprays. The model was verified by comparing the numerical and experimental results of cylinder pressure during the intake and compression strokes.

The work reported in this paper contributes to understanding the effects of ethanol/gasoline ratio on mixture formation and cooling effect which are crucial in the development of EDI+GPI engine. The spray simulations were carried out using a commercial CFD code. The model was verified by comparing the numerical and experimental results of spray shapes in a constant volume chamber and cylinder pressure in an EDI+GPI research engine. The verified model was used to investigate the fuel vaporization and mixture formation of the EDI+GPI research engine. The effect of the ethanol/gasoline ratio on charge cooling has been studied. Compared with GPI only, EDI+GPI demonstrated stronger effect on charge cooling by decreased in-cylinder temperature. However, the cooling effect was limited by the low evaporation rate of the ethanol fuel due to its lower saturation vapour pressure than gasoline's in low temperature conditions.