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To model sprays from pintle type nozzles with large hollow cone angle and high injection pressure, the correct flow field in the near region must be predicted. A new model was implemented in KIVA-3V code, which adopts the theory of steady gas jet to correct the relative velocities between the drop and gas phases, based on the existence of quasi-steady part of the conical spray and an assumption of equivalent gas jet. Accordingly, the structure of the sprays is defined into three parts: 1. initial part that the gas phase velocity is set to the assumed gas injection velocity; 2. quasi-steady part where the component of velocity in the symmetric line direction of the spray is corrected; 3. stagnation part which is left unchanged. This new model is referred to as the Relative Velocity Correction (RVC) model, and is a set of empirical equations that calculate the sectional distribution of the gas-phase velocity along the symmetric line of the sprays.

A relative velocity correction model (RVC), combined with the drop tracing system and spherical coordinate transformation, was developed and implemented in KIVA-3V code to yield grid-independent results for the spray simulations, especially for 3-D cases. The model applies the theory of steady turbulent jet flow to obtain sectional distribution of the gas-phase velocity along the spray axial in near region, which is used to correct the relative velocity between the drop and gas phases. The computed results were compared with the experimental data for both single-hole and three-hole fuel injections, including the spray tip penetrations and the spray images. The comparison shows that the RVC model performed well for all the cases.

Three-dimensional computations are performed to investigate the scavenging characteristics of poppet-valved two-stroke engines. The new subroutines are developed to handle various valve shrouds. Visualization of scavenging flow on a modified two-stroke transparent cylinder engine is used for validation and compared well in flow pattern. The flows in engines with different configurations are simulated at a speed of 5000 r/min. The stroke bore/ratio and valve arrangements were considered to investigate their effects on the scavenging flows. Additionally, valve timing and boost pressure have also been studied. The results show that stroke/bore ratio of 0.4 to 0.6, shroud angle of 69° to 108°, turn angle of shroud of 18° to 28°, average tumble ratio of 1.2-1.6 were found to be the optimum range for effective scavenging.

On the basis of heat release progresses for the various operating conditions acquired from a quiescent D.I. diesel engine, the quantitative relations hold among the values related to the combustion in the period after the end of rapid combustion are examined by experiment. SubjecTs on a method for dividing the burning period, on the burning characteristics for each period, on the relations among the values, and on the values expressing the mixing function of the fuel spray as well as the burning performance of the period are included. Discussions on the burning mechanism of the fuel spray are also given.

On the basis of heat release progresses for the various operating conditions acquired from a quiescent directinjection diesel engine, the quantitative relations between the quantities relating to the combustion in the rapid combustion period are examined by experiment. A couple of linear relations causing a particular feature of the burning process in this combustion period and some other relating fundamental properties are found and discussed. The experimental equations for the principal relations are also given. Acquired results illustrate the existence of macroscopic quantitative relations holding in the combustion process in diesel engines.