Search Results

In-cylinder flows such as tumble and swirl have an important role on the engine combustion efficiencies and emission formations. In particular, the tumble flow which is dominant in current high performance gasoline engines has an important effect on the fuel consumptions and exhaust emissions under part load conditions. Therefore, it is important to understand the effect of the tumble ratio on the part load performance and optimize the tumble ratio for better fuel economy and exhaust emissions. First step in optimizing a tumble flow is to measure a tumble ratio accurately. In this research the tumble ratio was measured, compared, and correlated using three different measurement methods: steady flow rig, 2-Dimensional PIV (Particle Image Velocimetry), and 3-Dimensional PTV (Particle Tracking Velocimetry). Engine dynamometer test was also conducted to find out the effect of the tumble ratio on the part load performance.

The effects of intake-generated swirl and tumble on cold start performance have been investigated in a firing single-cylinder Gasoline Direct-Injection (GDI) engine. The engine utilizes a Ford Zetec cylinder head modified for GDI operation and a fused silica cylinder which provides extensive optical access to the combustion chamber. Uniquely designed port-inserts were positioned in the intake ports to generate enhanced swirling or tumbling motion inside the cylinder. Experiments were conducted using a constant speed (∼ 900 rpm) simulated cold start procedure, where the engine is motored for approximately 40 cycles, after which fuel injection and spark ignition commence and continue for 190 cycles and then the engine is stopped. Measurements were made of the various engine temperatures, engine-out total hydrocarbon emissions, and in-cylinder pressure throughout the test period.

Experiments have been conducted in a firing single-cylinder spark-ignition engine employing a Ford Zetec cylinder head that has been modified to operate with either standard port-fuel-injection, air-forced port-fuel-injection or direct-injection. The engine utilizes a fused silica cylinder and therefore provides extensive optical access to the combustion chamber. Tests were conducted using a constant speed simulated cold start procedure, which is composed of an initial start-up transient and a quasi-steady-state idle period. In this procedure, the engine is briefly motored at 889 rpm and then combustion commences shortly after the start of fuel injection. Measurements which were performed include in-cylinder pressure as well as intake valve, exhaust valve, piston, cylinder, head, and intake air temperature throughout each cycle of the test period. The engine-out total hydrocarbon emissions were also measured.