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A comprehensive set of computational and experimental results for high- pressure diesel sprays are presented and discussed. The test cases investigated include injection of diesel into air under both atmospheric and high pressure/temperature chamber conditions, injection against pressurized and cross-flowing CF6 simulating respectively the density and flow conditions of a diesel engine at the time of injection, as well as injection into the piston bowl of both research and production turbocharged high-speed DI diesel engines. A variety of high-pressure injection systems and injector nozzles have been used including mechanical and electronic high-pressure pumps as well as common-rail systems connected to nozzles incorporating a varying number of holes with diameters ranging from conventional to micro-size.

The injection rate signals from a commercial diesel fuel injection system, based on a distributor pump driven by a DC motor, were characterised independently and consecutively by two injection rate meters based on the Zeuch and Bosch methods. The signals were first analysed in terms of their shot-to-shot variations over 64 consecutive injections and the correlations between needle lift and injection rate over a range of pump speeds and loads quantified by Fast Fourier Transform. A direct comparison of the injection rate signals on a cycle-resolved basis was achieved by connecting two consecutive injectors from the pump-line-nozzle injection system to a Bosch- and a Zeuch-based injection rate meters. The signals were acquired over a large number of injections in terms of mean and rms of the injected quantity, mean injection rate, maximum injection rate, average cumulative fuel injected and average injection duration.

The continuity and momentum equations for a pump-pipe-nozzle fuel injection system have been solved by a computer simulation program employing both the Runge-Kutta method and the more widely used method of characteristics. This allows the prediction of fluid phenomena and the dynamics of the mechanical components based on the geometry of the FIE system. The simulation includes the effects of possible cavitation, system leakage as well as variations in fuel density and bulk modulus. The computer model has been made as flexible as possible by using a modular format and inputting the system parameters from external files or dialog boxes. Experimentation was done on a Bosch VE type distributor pump supplying a multi-hole type nozzle which allowed preliminary evaluation of the model by comparing the predicted and measured injection rates and line pressures over a range of pump speeds and loads.

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.

A computer model simulating the flow in fuel injection systems has been used in order to investigate the fuel injection processes in an in-line pump-based fuel injection system for direct-injection diesel engines. The model is one-dimensional and it is based on the mass and momentum conservation equations for the simulation of the fuel flow and on the equilibrium of forces for the simulation of the mechanical movements of the valves present in the system. The fuel injection system tested comprised an in-line pump whose characteristics were examined by using as input the measured line pressure signal and by modeling the pump operation itself as well as the fuel flow through single- and two-stage injectors. For the validation of the model, extensive comparison with experimental data has been performed for a wide range of pump operating conditions.

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.