Computational optimization of a combustion system for a stoichiometric DME fueled compression ignition engine

Abstract

An optimization methodology based on a genetic algorithm coupled with the KIVA computational fluid dynamics (CFD) code is applied to the design of a combustion system of a heavy-duty diesel engine fueled with dimethyl ether (DME) and working with stoichiometric combustion in order to equip the system with a three way catalyst (TWC) to control the NOx emissions. The target of the optimization is to improve net indicated efficiency (NIE) while keeping NOx emissions, peak pressure and pressure rise rate under the reference engine levels. The results of the study provide an optimum configuration that offers a 0.6% NIE improvement while satisfying the restrictions and offering NOx values lower than 1% of the original emissions. Due to the methodology, not only the optimum combustion system configuration is presented, but also the cause-effect relation of the most relevant inputs with the optimization outputs are identified and analyzed. The new geometry shape reduced heat transfer losses by minimizing the surface area. Injection pressure and swirl proved to be key parameters necessary to overcome the increased mixing requirements of stoichiometric operation. EGR was found to simultaneously increase NIE while controlling NOx emissions. The results show the potential of stoichiometric compression ignition operation using DME as a promising pathway to maintain diesel-like efficiency, while achieving near zero NOx and soot emissions.

Combustion system optimization for dimethyl ether using a genetic algorithm

“…A possible e-fuel candidate for future combustion in compression ignition engines is dimethyl ether (DME), which has already been investigated in the past and has gained increasing attention again in the recent years. [4][5][6][7][8][9] DME has very beneficial combustion properties for compression ignition engines due to its high oxygen content and the absence of C-C bonds. Therefore, its combustion is almost soot free, even at stoichiometric air/fuel conditions.…”

Methanol fuel production, utilization, and techno-economy: a review

“…An optimum configuration with a 0.6% net indicated efficiency improvement and 1% reduction in nitrogen oxide values compared to that of the original case is also found by Benajes et al for heavy-duty diesel engine combustion using dimethyl ether. An increased net indicated efficiency was seen with exhaust gas recirculation with nitrogen oxide and soot emission control (Benajes et al 2018). Problems related to the combustion of dimethyl ether in spark ignition engines like leakage in the fuel system, engine wear and cavity were discussed by KRUCZYŃKI et al Nitrogen oxides, total hydrocarbon, and particle matter emission with the dimethyl ether-fuelled spark ignition engine were found to be 1.19, 0.22, and 0.015 g/kWh, respectively.…”

Future Power Train Solutions for Long-Haul Trucks

“…Recently, Benajes et al [203,204] and Kim et al [205] published regarding the numerical optimization of DME combustion in a diesel engine. Kim et al [205] sought optimal operating conditions of engine operation with DME and diesel, varying the start of injection, injection pressure, and angle, as well as the equivalence ratio, using a genetic algorithm.…”

“…The results showed that fuel and combustion systems must be optimized simultaneously and that an absolute efficiency improvement of 6.9% over baseline the diesel configuration can be achieved with similar emissions. Secondly, stoichiometric combustion was investigated in order to only equip the system with a three-way catalyst to control the NOx emissions [203]. It was noted that high-EGR rates for controlling the NOx led to lower efficiency and higher PM emissions.…”