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J. Shakal, 後藤新一 （機械研）、 進藤誠司, 本城史隆、上野弘樹（茨城大学）、 原山直也（日産ディーゼル）
INTRODUCTION
A heavy-duty type premixed charge spark ignited lean burn LPG engine is now being developed for use in trucks. This engine uses a computer-controlled steady flow type fuel metering system with a relatively simple outlet port (or nozzle) in the intake manifold. The structure of this port has a remarkable effect on the lean limit and engine characteristics, so it is important to study the effect of various designs on the inlet flow pattern. In this study, the actual intake pipe was simplified as a 60mm ID (66mm OD) transparent acrylic pipe, and various types of fuel outlet ports (e.g. "L" type, 1, 2, 3 or 6 holes, cut off flush with wall, etc.) were installed 23.5cm upstream of a throttle plate. In place of gaseous fuel, an oil mist was injected to allow visualization with a YAG laser. The laser beam was formed into a vertical sheet which was directed down the center of the acrylic pipe. To see other cross sections, the pipe could be rotated.
A gas sampling probe was used to obtain the fuel concentration at four cross sectional locations downstream of the injector (three locations if the throttle was used). For these tests, prevaporized LPG was injected by each fuel outlet port and the downstream flow was sampled for a 5s effective averaging time at each measurement point. LPG was 20% propane, 24% iso-butane, and 56% n-butane.
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Results Section
