Lean-Mixture Operation of a Passenger Car Gasoline Engine Ignited by Passively Q-Switched Nd:Yag/Cr4+:Yag Laser Spark Plugs

Abstract

Increasing human concern on the environment impact of the present internal combustion engines motivates the research for methods, techniques or even new concepts and technical solutions that could improve the engines performances. A promising technique for reduction of both fuel consumption and exhaust gas emissions in automotive engines is the operation by laser ignition (LI) [1]. For the first time, LI was used by Dale et al. in 1978 to run a one-cylinder ASTM-CFR engine [2] whereas LI of a four-cylinder Ford Mondeo engine was first achieved by Mullet et al. in 2008 [3]. More recently, based on development of compact laser spark plugs (LSP), similar to classical spark plugs (CSP), LI was successfully applied to operate real vehicles, by T. Taira et al. in 2013 [4] and by our research teams in 2015–2017 [5,6]. The results proved increased engine combustion stability [4,5] under LI in comparison with CSP ignition. However, there are still few experimental data, while investigations were done mainly at stoichiometric λ∼1 air-fuel mixture; furthermore, even fewer results are available regarding the exhaust emissions. In this work we report on LI of a four-stroke, four-cylinder, multipoint fuel injection gasoline passenger car engine that was operated at lean air-fuel mixtures using LI with high-peak power, passively Q-switched Nd:YAG/Cr4+:YAG LSP compact devices.