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The effect of port injected small fuel droplets was evaluated for several different modes of engine operation. The droplets were generated by an Air Forced Injector (AFI), Figure 1, which uses high velocity air through a nozzle to produce fuel droplets on the order of 10mm Sauter Mean Diameter (SMD). AFI results were compared to those from a standard production pintle injector. Steady state data, “motored cold start” data, and injector cut-out data were collected. All three data sets illustrate functional advantages of AFI over standard Electronic Fuel Injection (EFI). Steady state testing showed that the AFI delivers complete freedom for specifying injection timing with respect to HC emissions. This freedom is highly advantageous for transient conditions because open valve injection with small droplets causes much less port wall wetting. Therefore, less control system compensation is necessary, and more accurate air-fuel ratio control is achievable.

This paper introduces a new measurement technique into the field of engine diagnostics. LlPA (Laser lnduced Photochemical Anemometry) is used to measure velocities and velocity gradients over a chosen plane in a motored two-stroke engine during scavenging. The LlPA technique consists of tracking a phosphorescing grid which is created by laser lines directed into the flow. A 308nm pulsed excimer laser beam is divided into 15 lines which are sent through the appropriate optics to create the grid. The grid energizes the seed chemical that is premixed in the carrier gas. The seed chemical used consists of a mixture of phosphorescent gases with nitrogen as the carrier. The results are not bias by out of plane motions, or the inertia or the charge of particles. In each plane forty-four simultaneous points of data are taken with an approximate grid mesh size of 3mm × 3mm. These measurements are taken over thirty consecutive cycles.