Effects of argon dilution on the thermal efficiency and exhaust emissions of a NG engine

Abstract

Argon (Ar) is the third most common gas in the Earth’s atmosphere. About 700,000 tonnes of Ar are produced worldwide every year. Ar is inexpensive since it occurs naturally in air, and is readily obtained as a byproduct of cryogenic air separation in the production of O2 and N2. To decrease NOx emissions and slightly improve the thermal efficiency, Ar has been used in ICE before. However, it appears that it was used only in diesel and gasoline engines. This paper presents the effects of Ar dilution on the thermal efficiency and NOx emissions of a 6-cylinder natural gas SI engine. Ar was added into the intake charge at fixed boundaries under 1450 rpm and 50% load. The results show that the thermal efficiency increases first and then decreases with NOx emissions being decreased significantly as the dilution ratio (DR) of Ar increases. The thermal efficiency peaks at 9.8% DR with NOx emissions being decreased by 31.1%. At the maximum DR (18.4%), the thermal efficiency decreases by 0.3% with NOx emissions being decreased by 64.0%. Furthermore, from comparative experimental results it can be concluded that Ar dilution is superior in maintaining higher thermal efficiencies than CO2 and N2 for NG engines.