Injection Characteristics on the Surface of a Coaxial Jet

Abstract

In high pressure injection systems such as diesel motors, turbojets and rocket engines the injection process is critical in defining performance. The injection jet breakup and mixing controls the burning efficiency and overall energy conversion. This investigation takes a look at the jet behavior for a single injector element to determine the influence of the injection conditions on a round liquid jet. To adjust the relative velocity between the liquid jet and the gaseous ambient a wind tunnel like coaxial flow configuration has been used. This made it possible to distinguish between effects of aerodynamic forces, chamber pressure, jet velocity and turbulence. Shadowgraphy and a novel image processing approach was used to determine the jet surface characteristics; wavelength and amplitude. The absolute injection velocity of the jet seems to affect the structures the most with an increasing velocity causing the wavelengths to be smaller. An increase in chamber pressure seems to have little influence on the jet with no relative velocity between the gas and liquid jet, but increased the amplitude and drop formation frequency at other testing conditions. The amplitude trends provide information about the likelihood of drop formation.