Use of Numerical Techniques in the Diesel Engine Intake Manifold Optimization

Abstract

This paper is mainly focused on the design and optimization of intake manifold as regards plenum volume, shape and runner length to improve the breathing capacity of NA and TC diesel engines. The main aim of this work is to maximize volumetric efficiency of diesel engine intake manifolds in order to handle high EGR levels and ensure uniform distribution of charge to minimize cylinder-to-cylinder variation. The intake manifold is designed by using numerical techniques and analysis is carried out by employing 1D and 3D CFD simulation tools. The entire engines have been modeled in 1D-code using base manifold dimensions and validated with experimental data. Simulation result shows good agreement with the acquired real-time data of intake and exhaust manifold pressure characteristics particularly during overlap period. Also, basic engine performance, combustion pressure and NOx & Soot emissions predicted are found within 5–10% of the experimental data. This paper presents the work carried out on intake manifold design through case studies on one each NA and TC diesel engine, with and without EGR. The optimized manifold plenum volume for NA engine of approximately 75% (including runners) of swept volume and runner length of 97mm have shown considerable improvement in volumetric efficiency resulting in 2.5% improvement in bsfc. Whereas, plenum volume of 1.45 times engine displacement with same runner length shows more than 3% improvement in bsfc for TCI diesel engine. Further, transient simulation study is carried out using 3D CFD simulation tool for two complete cycles and it is observed that mass flow rate deviation between the runners is reduced to less than 5%. Shape of the runner is also modified to avoid any eddy formation in the flow path. The runner diameter is optimized. Optimization location for EGR entry and modification to runner design is also described in this paper demonstrating uniform EGR distribution with acceptable deviation.