Three-dimensional numerical simulations on the effect of ignition timing on combustion characteristics, nitrogen oxides emissions, and energy loss of a hydrogen fuelled opposed rotary piston engine over wide open throttle conditions

• Published in: Fuel (Guildford) 2021-03, Vol.288, p.119722, Article 119722
• Main Authors: Gao, Jianbing, Tian, Guohong, Ma, Chaochen, Xing, Shikai, Huang, Liyong
• Format: Article
• Language: English
• Subjects: Chemical energy; Combustion; Combustion characteristics; Electric vehicles; Emission; Energy; Energy dissipation; Energy loss; Engines; Fuel economy; Heat transfer; Hybrid vehicles; Hydrogen fuel; Ignition timing; Mathematical models; Nitrogen oxides; NOx emission characteristics; Opposed rotary piston engines; Oxides; Photochemicals; Piston engines; Power sources; Spark ignition; Thermodynamic efficiency; Throttles
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.119722

[Display omitted] •ISFC were insensitive for ignition timing being earlier than −10° CA.•Power density of this hydrogen fuelled ORP engine was ~80 kW/L over 5000 RPM.•NOx emission factors were lower than 16 g/(kW·h) over the given scenarios.•Heat loss by cylinder walls ranged 6%–19% over wide open throttle condition. Opposed rotary piston (ORP) engines have advantages of high power density, few moving parts, and smooth operations, which makes ORP engines as potential power sources for hybrid vehicles and range extended electric vehicles. Ignition timing significantly affects the performance of spark ignition engines including fuel economy and emission factors. In this paper, the effect of ignition timing on the engine performance was investigated using a three-dimensional numerical simulation method. The results indicated that crank angle corresponding to the peak in-cylinder pressure over the ignition timing of −8.2° crank angle (CA) was advanced compared with other cases having earlier ignition timing; however, the crank angle of peak heat release rates were retarded. Start of combustion was delayed by retarding the ignition timing and increasing engine speed; combustion duration over the ignition timing of −18.9° CA ~ −11.1° CA changed slightly for individual engine speed. Indicated specific fuel consumption (ISFC), being hardly dependent on the ignition timing, was less than 74 g/(kW·h) over the ignition timing of −17.3° CA ~ −11.1° CA, where indicated thermal efficiency was approximately 41%, 39% and 35% for 1000 RPM, 3000 RPM and 5000 RPM respectively. When ignition timing was later than −11.1° CA, ISFC and indicated thermal efficiency were deteriorated seriously. Nitrogen oxides (NOx) emission factors increased with engine speed over early ignition timing; however, they were inverse for late ignition cases. Higher engine speed and retarded ignition timing led to higher percentage of exhaust energy in fuel chemical energy.