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We propose a spray pattern control method for swirl-type injectors in direct injection (DI) gasoline engines. An L-cut orifice nozzle (L-Step nozzle) that produces a horseshoe spray pattern is used to create a rich and lean concentration region. To further control the distribution of fuel, the relationship between the nozzle geometry and the spray pattern is investigated. The mechanism for a horseshoe spray formation is hypothesized and verified through experiment. The spray shape and fuel distribution is found to be controllable by configuring the L-cut step-walls. Furthermore, it is discovered that independent control of rich and lean region distribution is possible by arranging the step-wall position and height.

We propose a flat spray pattern to improve conventional stratified-charge combustion systems in a direct-injection (DI) gasoline engine. Swirl-type DI fuel injectors with a V-groove cut orifice nozzle (V-groove nozzle) and a rectangular-groove cut orifice nozzle (U-groove nozzle) are newly designed. We examine experimentally the characteristics of newly designed injector nozzles under various ambient pressure and fuel pressure conditions. The fuel spray characteristics were tested inside an experimental pressure chamber. The resulting spray patterns were illuminated by YAG-laser sheet and recorded by CCD cameras. The atomization of fuel-spray in the V-groove and U-groove nozzle was also investigated. These experiments showed that the V-groove and the U-groove nozzles generate a well-atomized flat fuel-spray pattern that can be controlled by the orifice-depth and it is robust under ambient pressure variations.

The conventional fuel injector for direct-injection gasoline engines is driven by voltage step-up circuitry and current control circuitry. The voltage step-up circuitry boosts the battery voltage to near 100 volts. This conventional system is fairly large and a more compact system is preferable. We have developed a mass producible battery-voltage-driven fuel injector for direct-injection gasoline engines. The injector has a dual-coil structure that enables the injector to operate at the battery voltage, thus eliminating the need for either voltage step-up circuitry or current control circuitry. Deviation in battery voltage and changes in harness resistance are fully compensated through opening-coil energization-time control. In addition, with this control method, the injector can be used with a wide range of fuel pressures.

Fuel-spray pattern is one of the most critical factors for obtaining stable combustion. A DI fuel injector in which the fuel-spray pattern can be easily controlled and predicted is therefore essential. Our main goal is to develop a fuel-spray pattern control method that takes into account the influences of ambient pressure and fuel pressure. After deciding how to incline and split the fuel spray, we designed an L-cut orifice nozzle (L-step nozzle) based on a swirl-type injector. We investigated the fuel-spray pattern of the newly designed injector both experimentally and numerically. Experimentally, the L-step nozzle injector was used to spray fuel into an experimental pressure chamber. The resulting spray patterns were visualized by YAG-laser sheet and recorded by CCD cameras. The spray formation was analyzed and the spray patterns were evaluated in terms of spray angle and penetration length. Atomization from the spray in the L-step nozzle injector was also investigated.

We examine experimentally and numerically the influences of nozzle geometry on spray angle and penetration length. Swirl-type DI fuel injectors with an L-cut orifice nozzle (L-type) and a taper-cut orifice nozzle (Taper-type) are newly designed. The new injectors are used to spray fuel inside an experimental pressure chamber. The resulting spray patterns are visualized by YAG-laser sheet and recorded by CCD cameras. These experiments showed that both the L-type and taper-type nozzles can produce an inclined fuel-spray pattern. Furthermore, the fuel-spray pattern can be controlled by changing the depth of the orifice in both nozzles. During the development of the new nozzles, a CFD code for predicting the spray shape are also developed. By comparing the calculated results to the experiments, it was shown that the CFD code can predict the spray angle with reasonable accuracy. The spray angle was found to be strongly dependent on the air void geometry formed inside the orifice.