The Effect of Fuel Composition and Manifold Conditions Upon Spray Formation from an SI Engine Pintle Injector

The performance of a pintle-type gasoline injector has been studied. Observations performed on test-rigs and running engines suggest that under conditions of low manifold pressure a ‘pencil-jet’ formation may replace the well atomized spray normally produced by the injector. Importantly, this phenomenon was not observed when using substitute fuels such as n-heptane.

It is concluded that both the mechanical design of the injector and the combination of the liquid properties density, viscosity and surface tension influence the ability of a given injector to produce a well atomized spray at low manifold pressures. The paper discusses measures to prevent pencil-jet formation.