Optimal Design of Conventional In-Line Fuel Injection Equipment

Abstract

The paper describes an application of optimal design procedure employed on conventional in-line fuel injection equipment for a diesel engine. The procedure is applied to a set of design parameters concerning the design of the cam, high-pressure pump, delivery valve, snubber valve, high-pressure tube and injector respectively. The values of these design parameters are optimized simultaneously within specified maximum and minimum values in order to approach a target injection rate history. The proposed optimal design procedure is defined as a solution process of a non-linear mathematical programming problem defined by the objective and constraint functions. The objective function measures the difference between the target and actual injection rate histories while the constraints concern the response of the system as well as several technological limitations. The form of the objective function is such that it requires special treatment similar to those employed in optimal design of dynamic multi-body systems. However, the complexity of the fuel injection equipment causes specific numerical difficulties when the ideas employed for dynamic systems are adopted. The paper describes how to modify the usual approach in order to circumvent these difficulties. The theory is illustrated with a numerical example comparing the usual versus the modified approach.