Optimization design of combustion chamber for a non-road diesel engine in high-altitude region

Abstract

Modifying and optimizing the combustion chamber structure of diesel engines is one of the effective measures to improve in-cylinder combustion and reduce emissions in high-altitude areas. This study focuses on a non-road diesel engine running in a high-altitude environment of 2000 m. Initially, sensitivity analysis was conducted to identify the critical structural parameters of the combustion chamber at peak torque condition. Subsequently, a Latin hypercube sampling (LHS) approach was employed for experimental design, and a back-propagation (BP) neural network was utilized to develop a surrogate model. Finally, the non-dominated sorting genetic algorithm II (NSGA-II) was employed to perform multi-objective optimization, and the technique for order preference by similarity to ideal solution (TOPSIS) was utilized to select the optimal combustion chamber structural parameters suitable for high-altitude regions. Results show that the optimized combustion chamber improved in-cylinder fuel-air mixing and reduced emissions at high altitude. Compared to the original design, the optimized throat diameter (D_i) decreased by 6.22 %, height of the central protrusion (T_m) decreased by 1.57 %, and pit radius (R₄) increased by 3.87 %. The optimized brake specific fuel consumption (BSFC) remained almost unchanged at this altitude, while nitrogen oxides (NOx) and soot emissions were reduced by 12.47 % and 3.23 %, respectively.