Under-expanded Gaseous Jets Characterization for Application in Direct Injection Engines: Experimental and Numerical Approach
In the last years, increasing concerns about environmental pollution and fossil sources depletion led transport sector’s research and development towards the study of new technologies capable to reduce vehicle’s emissions and fuel consumption. Direct-injection systems (DI) for internal combustion engines propose as an effective way to achieve these goals. This technology has already been adopted in gasoline engines (GDI) and, lately, a great interest is growing for its use in natural gas fuelling engines, so increasing efficiency with respect to port-fuel injection engines. Alone or in combination with other fuels, compressed natural gas (CNG) represents an attractive way to reduce exhaust emission (high H/C ratio), can be produced in renewable ways, and is more widespread and cheaper than gasoline or diesel fuels. Gas direct-injection process involves the occurrence of under-expanded jets in the combustion chamber.