SI Engine Fueled with Gasoline, CNG and CNG-HHO Blend: Comparative Evaluation of Performance, Emission and Lubrication Oil Deterioration

Hydroxy gas (HHO) is one of the potential alternative fuels for spark ignition (SI) engine, notably due to simultaneous increase in engine performance and reduction in exhaust emissions. However, impact of HHO gas on lubrication oil for longer periods of engine operation has not yet been studied. Current study focuses on investigation of the effect of gasoline, CNG and CNG-HHO blend on lubrication oil deterioration along with engine performance and emissions in SI engine. HHO unit produces HHO gas at 4.72 L/min by using 6 g/L of KOH in the aqueous solution. CNG was supplied to the test engine at a pressure of 0.11 MPa using an electronically controlled solenoid valve. Engine tests were carried out at different speeds at 80% open throttle condition and various performance parameters such as brake power (BP), brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), exhaust gas temperature and exhaust emissions (HC, CO2, CO and NOx) were investigated. In addition, various lubrication oil samples were extracted over 120 h of engine running while topping for drain out volume and samples were analyzed as per ASTM standards. CNG-HHO blend exhibited better performance i.e. 15.4% increase in average BP in comparison to CNG, however, 15.1% decrease was observed when compared to gasoline. CNG-HHO outperformed gasoline and CNG in the case of HC, CO2, CO and brake specific fuel consumption (31.1% decrease in comparison to gasoline). On the other hand, CNG-HHO produced higher average NOx(12.9%) when compared to CNG only. Furthermore, lubrication oil condition (kinematic viscosity, water contents, flash point and total base number (TBN)), wear debris (Iron (Fe), Aluminum (Al), Copper (Cu), Chromium (Cr)) and additives depletion (Zinc (Zn), Calcium (Ca)) presented a significant degradation in the case of CNG-HHO blend as compared to gasoline and CNG. Lubrication oil analyses illustrated 19.6%, 12.8% and 14.2% decrease in average viscosity, flash point and TBN for CNG-HHO blend respectively. However, average water contents, Fe, Al and Cu mass concentration appeared 2.7%, 25x10-6, 19x10-6, and 22x10-6 in lubrication oil for CNG-HHO respectively.