Browse Publications Technical Papers 2009-32-0135

Effect of Boost Pressure on Engine Performance and Exhaust Emissions in Direct-Injection Compressed Natural Gas (CNG-DI) Spark Ignition Engine. 2009-32-0135

Natural gas vehicle gives 11-22% lower power output compared to equivalent liquid-fuelled vehicles. With direct injection of gaseous fuel there has been a problem of reduction in volumetric efficiency when injecting the fuel at early and partial direct injection. This is due to some of the air will be displaced by the fuel as these injection timings have inlet valve open during injection. Recently, there is an increasing interest in supercharging S.I. engines operating on natural gas mainly to its superior knock resisting properties in comparison to traditional liquid fuels. The present work reports the effect of boost pressure on engine performance and exhaust emissions. The experimental study was conducted on a 4-stroke direct injection compressed natural gas spark ignition engine with compression ratio of 14. Simulated port injection (Early injection), 300° BTDC, and partial direct injection, 180° BTDC, were varied at each operating speed with variation of supercharging pressure. For boost pressure above 7.5kPa it is proven that there is better performance at all operating engine speeds compared to without supercharging system. In-cylinder pressure and temperature would be high with increasing boost pressure that outcome high NOx emission. Boost pressure has no significant influence on HC emission while it makes CO emission level lower due to improvement of brake specific fuel consumption. With supercharging system, partial direct injection gives better performance for speeds 2000 to 4000 RPM compared to early injection timings. Whereas early injection timing with boost pressure gives better performance for engine speeds 4000 to 5000 RPM compared to partial direct injection due to enough time available for mixture preparation.


Subscribers can view annotate, and download all of SAE's content. Learn More »


Members save up to 16% off list price.
Login to see discount.
Special Offer: Download multiple Technical Papers each year? TechSelect is a cost-effective subscription option to select and download 12-100 full-text Technical Papers per year. Find more information here.
We also recommend:

Improvement of Combustion and Emissions in a Dual Fuel Compression Ignition Engine with Natural Gas as the Main Fuel


View Details


Spark Ignition Engine Control Variables Study


View Details


Triple Stratification in a Spark Ignition Engine: The Effect on the Emission at Unthrottled Light Load


View Details