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A numerical optimization technique has been applied in order to obtain the optimum level of some design variables of the diesel fuel injection nozzle. A description of the optimization procedure is provided together with a discussion of the physical and mathematical flow model used. Sample applications of the optimization procedure addressing design of a fuel injection nozzle consideration along with comparisons among three different fuels are presented. The fuel injection mean rate, the diameter of the injection cavity, and the diameter of the injection orifice were used as the objective functions in different aspects of the optimization procedure. Chosen design variables were: the angle of the needle tip, the diameter of the nozzle injection cavity, and the injection orifice diameter. Some constraints characterizing the operating conditions of the injection nozzles were taken under consideration.

The application of a multiple polynomial regression procedure for optimization of design and performance parameters has been presented. To illustrate the statistical method, data from a laboratory test of an exhaust emission reduction device was used. There were four factor variables for which the response was constructed. Among the factor variables two were design parameters; the remaining two were the operating parameters. The selected response variables were CO, NO, and HC's. The assumptions for the analysis procedure are presented. Problems which could affect the validity of the statistical procedures for the design optimization are discussed. Experimental verification of the optimization results was performed. Overall agreement between the predicted level of pollutants reduction and measured values did not differ by more than ten percent.