Optimization of Fuel Injection Configurations for the Reduction of Emissions and Fuel Consumption in a Diesel Engine Using a Conjugate Gradient Method

摘要

The objective of this study is the development of a computationally efficient CFD-based tool with the capability of finding optimal engine operating conditions with respect to emissions and fuel consumption. The approach taken uses a conjugate gradient method, where the line search is performed with a backtracking algorithm. The initial backtracking step employs an adaptive step size mechanism which depends on the steepness of the search direction. The engine simulations are performed with a KIVA-3-based code which is equipped with well-established spray, combustion and emission models. The cost function is based on the idea of the penalty method and is minimized over the unit cube in n-dimensional space, which represents the set of normalized injection parameters under investigation. The application of this optimization tool is demonstrated for the Sulzer S20, a central-injection, non-road DI diesel engine. The spray parameters that are optimized are the number of nozzle orifices, the injection direction, the start of injection and the injection duration/injection pressure. Simulations are performed for different cost function weights to illustrate how optima can be attained. It was found that the computational costs are considerably lower than the ones of other global optimization methods.