Optimization of combustion chamber geometry for natural gas engines with diesel micro-pilot-induced ignition

Abstract

a b s t r a c tSmokeless, low nitrogen oxides (NOx), and high thermal efficiency have been achieved through the lean-burn concept for natural gas engine with diesel micro-pilot-induced ignition (MPII). However, the combustion chamber is usually not specialized for natural gas combustion, and increases in the unburned hydrocarbon (HC) and carbon monoxide (CO) emissions are still a challenge for this type of engines. This paper describes optimization of the combustion chamber geometry to reduce the HC and CO emissions and improve the combustion efficiency in the MPII natural gas engine. The 3-D computational fluid dynamics (CFD) simulation model coupled with a chemical reaction mechanism is described. The temporal development of the short-pulsed diesel spray in a high pressure constant-volume vessel is measured and used to calibrate the spray model in the CFD simulation. The simulation models are validated by the experimental data of the in-cylinder pressure trace, apparent heat release rate (AHRR) and exhaust gas emissions from a single-cylinder MPII natural gas engine. To generate the various combustion chamber geometries, the bowl outline is parameterized by the two cubic Bezier curves while keeping the compression ratio constant. The available design space is explored by the multi-objective non-dominated sorting genetic algorithm II (NSGA-II) with Kriging-based meta-model. With the optimization, the HC and CO emissions are reduced by 56.47% and 33.55%, respectively, while the NOx emissions, the maximum rate of pressure rise and the gross indicated thermal efficiency that are employed as the constraints are slightly improved. Finally, the mechanism of the reduction in HC and CO emissions with the optimized combustion chamber geometry is investigated and discussed in details.

Research on Fuel Efficiency and Emissions of Converted Diesel Engine with Conventional Fuel Injection System for Operation on Natural Gas

“…These types of engines, also known as dual-fuel engines, can provide significant improvements in efficiency and emissions [16][17][18][19][20][21][22][23][24][25]. For example, in research on a dual-fuel cargo truck engine [26] a decrease in NO x of up to six times and decrease in CO of up to 83% were observed compared to diesel only operation.…”

Investigation of the Effects of Piston Geometry and Combustion Process Parameters on Engine Performance of Methane Fuelled Compression Ignition Engines with Kriging Method

“…Yapılan bir çalışmada kullanılan Kriging yöntemi ile metan yakılan sıkıştırmalı ateşlemeli motorlarda en az emisyon oluşturabilecek yanma odası geometrisi tasarlanmıştır [5]. Bu çalışmanın bir amacı da, fakir yanma sonucunda CO ve HC emisyonlarının artışını yanma odasının geometrisini optimize ederek azaltmaktır.…”

Prospects for energy efficiency improvement and reduction of emissions and life cycle costs for natural gas vehicles

“…The peculiar properties of the dual-fuel engine working process enable obtaining the best economic effect at medium and high loads and provide the possibility to operate by diesel fuel when using up all the gas in the tank. The diesel engine operating according to the dual-fuel cycle is also a prospective solution in terms of reduction of nitrogen oxide and particulate matter emissions, while requiring marginal design updates [15,16].…”