Search Results

Gasoline direct-injection (GDI) engines have evolved as a solution to meet the current demands of the automotive industry. Benefits of a GDI engine include good fuel economy, good transient response, and low cold start emissions. However, they suffer from problems, like combustion instability, misfire, and impingement of fuel on in-cylinder surfaces. Therefore, to highlight the influence of fuel injection timing on in-cylinder flow, turbulence, mixture distribution and wall impingement, a computational study is conducted on a small-bore GDI engine. Results showed that air motion inside the engine cylinder is influenced by direct-injection of fuel, with considerable variation in turbulent kinetic energy at the time of injection. Due to charge cooling effect, mixture density and trapped mass were increased by about 10.8% and 9.5%, respectively.

In this experimental work, the potential advantages of lowering the Compression Ratio (CR) of a diesel engine in terms of performance, combustion and emission related parameters along with the analysis and improvement in its cold starting characteristics are presented. The CR of a single cylinder direct injection common rail diesel engine used for light-duty automotive applications was lowered from 18:1 to 14:1 by suitable modifications to the combustion bowl while retaining its shape. The engine with both the CRs was tested on a dynamometer rig under similar operating and fuelling conditions. Additionally, experiments were carried out to determine the extent to which in-cylinder smoke emissions can be reduced when the Nitric Oxide (NO) levels of 14 CR are matched to the higher levels seen in 18CR. In order to evaluate cold start ability and idling stability of the engine with a reduced CR (14:1), the engine was instrumented inside a cold chamber.