Investigation of the effect of HHO-assisted flame-jet ignition on in-cylinder combustion, engine performance, and environmental indicators in a propane-fueled SI engine

Abstract

In this paper, a spark ignition (SI) engine is modified to operate by flame-jet ignition using oxy-hydrogen (HHO) gas in a small pre-combustion chamber (PCC) at partial load. The air-propane mixture in the main combustion chamber was ignited with an HHO-assisted flame jet, and the effects on in-cylinder combustion, engine performance, and environmental factors were investigated. In experimental studies, the SI engine was operated at 2300 rpm with a throttle opening of 1/2 at 24 different operating points generated by combining six different mixtures (λ = 0.9–1.4) and four different HHO flow rates (HHO = 0–1.0 l.min−1). The situation in which the HHO gas is not injected into the PCC is passive, while the situation in which it is injected is active. The findings showed that operating conditions with active PCC at λs significantly improved engine performance and environmental impact. The effect of active PCC was greater with lean mixtures (λ = 1.3–1.4) and decreased as the mixture shifted towards the rich (λ = 0.9). In addition, the effect of active PCC at all λs slowed down after 0.7 l.min−1 HHO flow rate. At λ = 1.4 and 1.0 l.min−1 HHO flow rate, where the highest effect occurs, Pmax and IMEP with active PCC are 76.09 % and 58.9 % increased, respectively; ISFC decreased by 38.3 % and ηt reached by 37 %; mfb’s of 0–10 %, 10–90 %, and 90–100 % 38.27, 20.83 %, and 47.62 % shorten, respectively; COVIMEP decreased by 6043 units; HC decreased by 95.18 %; CO2 and NOx emissions increased by 44.6 % and 24 %, respectively. In addition, at λ = 1.4, ΣE&SC decreased up to 164.5 €.kWh−1 which is 11 % lower than the lowest value of 183.5 €.kWh−1 obtained at passive PCC.