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Observations of the scavenging flow field have been made in a modified poppet-valved two-stroke engine with a transparent cylinder. Four kinds of cylinder heads with different port configuration were created to analyze their effects on the scavenging flow and develop new scavenging concepts. A mineral oil fog discharge system was used to visualize the air flow during the scavenging process. All of the images were recorded by a high speed video camera which show the development of the scavenging processes and clearly indicate the scavenging jet structure, the tumble pattern and the location of re-circulation regions. The analyses allow us to judge the quality of the scavenging processes. The small changes in port geometry could significantly affect the scavenging flow. Tumble as well as swirl should be considered as main means to organize the scavenging flow in order to avoid short-circuiting losses and create condition favorable to combustion.

In CFD (Computational Fluid Dynamics) verification of vehicle aerodynamics, detailed velocity measurements are required. The conventional 2D-PIV (Two Dimensional Particle Image Velocimetry) needs at least twice the number of operations to measure the three components of velocity ( u,v,w ), thus it is difficult to set up precise measurement positions. Furthermore, there are some areas where measurements are rendered impossible due to the relative position of the object and the optical system. That is why the acquisition of detailed velocity data around a vehicle has not yet been attained. In this study, a detailed velocity measurement was conducted using a 3D-PIV measurement system. The measurement target was a quarter scale SAE standard vehicle model. The wind tunnel system which was also designed for a quarter scale car model was utilized. It consisted of a moving belt and a boundary suction system.

High-pressure fuel spray proposed for direct injection gasoline engine was evaluated by means of a phase Doppler anemometer (PDA) and flow visualization. The intermittent fuel spray from a swirl type injector was injected in a constant volume chamber under various conditions of backpressure and ambient temperature. The backpressures were set to 0, 0.5 and 1 MPa in gauge pressure. The ambient temperatures were set to 293, 373, 423 and 473K. Normal-heptane was used as a fuel with injection pressure of 10MPa and injection frequency of 10Hz. Spray characteristics of the temporal and spatial distributions of the mean velocity and the mean diameter were measured by the PDA. Visualizations of spray were also made by a particle image velocimetry (PIV). The experimental results show the effects of backpressure and ambient temperature on the spray shape and characteristics of droplet size and velocity distributions.

The combination method for measuring the oil film thickness and velocity is proposed. The oil film thickness is measured by laser induced fluorescence (LIF) method and its velocity is measured by particle image velocimetry (PIV). A model engine is employed in order to check the LIF measurement for oil film thickness, and an optical access engine based on production engine is utilized for both measurements of oil film thickness and velocity. In the combination method, LIF images are used in the PIV measurement instead of particle images. From the results, the oil film thickness and velocity can be measured simultaneously by the combination method utilizing only LIF dye. The oil film thickness and velocity are presented along with crank angle of the engine under the motoring operation. The oil film velocity is also measured under the firing operation.