벽면 충돌 가솔린 분무의 미립화

Abstract

현재 대부분의 가솔린 기관은 흡기포트에 연료를 분사시켜 혼합기를 형성하는 방법(MPI)을 채용하고 있다. 인젝터에서 분사된 연료는 포트 벽면과 흡기밸브에 충돌하여 일부는 벽면에 부착하여 액막을 형성하고 나머지는 충돌에너지에 의하여 작은 액적으로 2차 미립화된다. 이러한 충돌분무의 특성은 기관 응답성과 배기가스에 큰 영향을 미친다. 따라서 이러한 특성을 명확히 파악하는 것은 기관 성능 개선에 중요하다.

본 연구는 단공 hole노즐을 사용하여 벽면에 충돌하는 가솔린 분무의 미립화 특성을 레이저 시트광을 이용한 가시화법으로 조사하였다. 연료에 형광물질을 첨가하여 레이저로 이를 여기시켜 얻은 형광과 액적의 산란광을 동시에 촬영하여 분무의 공간적 확산, 연료농도의 분포, 미립화 정도를 정성적으로 측정하였다. 충돌각도, 충돌속도가 충돌 후 분무의 미립화 특성에 미치는 영향을 파악하였다. 벽면에 부착되어 액막이 되는 연료량도 충돌부 주위에 설치된 가는 틈새로 흘러든 연료량을 측정하여 정량적으로 계측하였다.

Most gasoline engines employ a port injection system to achieve the better fuel-air mixing. A part of injected fuels adheres to the wall or intake valve and forms a film of liquid fuel. The other is secondarily atomized by the spray-wall interaction. A better understanding of this interaction will help in designing injection systems and control strategies to improve engine performance and exhaust emissions.

In the present research, the spray-wall interaction was investigated by laser sheet visualization method. The fluorescence from the fuel doped with fluorescer(Rhodamine 6G) and scattering light were imaged simultaneously by a negative color film. The shape of sprays was pictured at various impinging velocities and angles. The fuel dispersion was estimated by fluorescence light, and the atomization was evaluated by the fluorescence/scattering light ratio. The amount of fuel in a film was measured by weighting the fuel trapped in a circular narrow groove around the impinging point.

Most gasoline engines employ a port injection system to achieve the better fuel-air mixing. A part of injected fuels adheres to the wall or intake valve and forms a film of liquid fuel. The other is secondarily atomized by the spray-wall interaction. A better understanding of this interaction will help in designing injection systems and control strategies to improve engine performance and exhaust emissions.

In the present research, the spray-wall interaction was investigated by laser sheet visualization method. The fluorescence from the fuel doped with fluorescer(Rhodamine 6G) and scattering light were imaged simultaneously by a negative color film. The shape of sprays was pictured at various impinging velocities and angles. The fuel dispersion was estimated by fluorescence light, and the atomization was evaluated by the fluorescence/scattering light ratio. The amount of fuel in a film was measured by weighting the fuel trapped in a circular narrow groove around the impinging point.