| Summary: | 碩士 === 國立雲林科技大學 === 機械工程系 === 102 === This research studies the Spray impingement and atomization behavior of a Kymco Xciting 500c.c. modified gasoline direct injection engine. The back light strobescope is used to observe the spray phenomena under different injection pressure (30, 60, 100 bars) and chamber pressure (0, 3.5, 6 bars) The PIV system is applied in this study.
The CNC machined semi GDI piston surface has the wall-guide shape; however, the nozzle position is one the piston top. The spray-guided injection mode is used on the wall-guided piston surface to observe the droplet atomization and movement.
Results indicate the higher injection pressure causes the spray sliding distance to increase by 30~40%. The PIV analysis find the spray angle, spray penetration velocity and spray splash range (reduced by 28~36%) are both reduced when the chamber pressure is increased. The spray moves upward is restricted by the increased nitrogen gas chamber pressure. This is because the dense charge reduces the droplet velocity.
This research finds the increase of the injection pressure and plate temperature can increase the droplet moving velocity, the better spray distribution and optimized spark position design allows the optimization design and combustion. A best fuel nozzle position, spark plug position, and ignition timing can achieve the best engine operation conditions.
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