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A computer model solving the 1-D flow in a typical fuel injection system for direct-injection diesel engines is presented. A Bosch distributor - type VE pump connected to four Stanadyne pencil - type nozzles has been used to validate the computer model over a wide range of operating conditions. Validation of the developed computer code has been performed for eight representative test cases. The predicted values which were compared with the experimental ones include the pumping chamber pressure, the line pressure, the needle lift and the injection rate. Results using as input the measured pumping chamber pressure are also presented in order to identify the error in the injection rate signal attributed to the difference between the simulated and the experimental pumping chamber pressure. In addition, the total fuel injection quantity for pump speeds between 500 and 2000 rpm and lever positions between 20% to 100% was calculated and compared with measurements.

The spray/wall interaction in small direct-injection diesel engines employing swirl was simulated in a bench-type experiment by a steady cross-flow of air acting on a transient diesel spray impinging normally onto a heated and unheated flat plate under atmospheric conditions. The droplet size and velocity characteristics in the radial wall-jet formed on the plate after spray impingement were investigated by phase-Doppler anemometry and the spray/wall heat transfer during impingement was measured using fast-response thermocouples. The results showed that the mechanism of secondary atomisation of the impinging droplets was altered as droplets from the approaching spray were entrained by the cross-flow, while the spray/wall heat transfer was reduced due to the lower droplet flux reaching the wall. Based on the approaching droplet velocity and size characteristics and wall temperature, an empirical correlation has been derived between the flow and heat transfer parameters.

The spatial and temporal characteristics of transient diesel sprays impinging on unheated and heated walls were investigated by phase-Doppler anemometry (PDA) and the heat-transfer distribution in the vicinity of the impingement region was determined by fast response thermocouples. The results have provided quantitative evidence about the effect that the presence of the flat wall exerts on the spray characteristics. For example, independent of the thickness of the liquid film, the wall rearranges the droplet size distribution of the free spray with droplet collision and coalescence playing an important role in both the droplet redistribution and in the development of the wall-jet. Droplet sizes were reduced and mean tangential velocities increased with wall temperature at the upstream side and at the front of the wall-jet, respectively.

Two optical single-cylinder spark-ignition engines equipped with two- and four-valve cylinder heads were used to examine the flow and flame interaction under lean mixture conditions. Images of the developing flame under quiescent, swirl, low tumble and high tumble flow conditions corresponding to a wide range of mean velocity and turbulence levels around the time of ignition were obtained with an image-intensified CCD camera using the light radiated by the flame and the flow in the vicinity of the spark plug was quantified by laser Doppler velocimetry. In the case of the tumbling flow, the flame images were software-processed to allow estimation of the total flame area, the displacement of its centre as a function of crank angle and their correlation with the cylinder pressure.

An enlarged transparent model of a six-hole vertical diesel injector has been used to allow visualization of the flow at Reynolds and cavitation numbers matching those of real size injectors operating under normal Diesel engine conditions. The visualization system comprised a CCD camera, high-magnification lenses and a spark light source which allowed high-resolution images to be obtained. The flow conditions examined in terms of flow rates and pressures covered the range from low to full load of the real size injector while the needle lift position corresponded to that of full lift of the first- and second- stage in two-stage injectors. In addition, different values of needle eccentricity were tested in order to examine its effect on the cavitation structures within the injection holes.

A one-dimensional, transient and compressible flow model was used in order to simulate the flow and pressure distribution in advanced high-pressure fuel injection systems; these include electronic distributor-type pumps with either axial or radial plungers and a common-rail system. Experimental data for the line pressure, needle lift, injection rate and total fuel injection quantity obtained over a wide range of operating conditions (from idle to high speed/full load) were used to validate the model. The FIE system used for validation comprised an electronic high-pressure pump connected to two-stage injectors of different type including 6-hole vertical and 5-hole inclined conical-sac and VCO nozzles.