Experimental Investigation of a Gasoline-to-LPG Converted Engine Performance at Various Injection and Cylinder Pressures with Respect to Propane Spray Structures

Power reduction when converting a gasoline engine to propane can be mitigated by designing an injection system so the heat required for evaporation of the propane is drawn from the intake air. Air is cooled and densified, resulting in volumetric efficiency increase. LPG sprays were imaged using Mie and LIF imaging techniques from a port fuel injector, and from long and short connecting pipes. Images were taken in an optically-accessed pressure chamber at atmospheric pressure and fuel pressures of 1.5 MPa. Images of the pipe-coupled injection spray show significant evaporation in the pipe, whose amount depend on the length and diameter of the pipe. The duration of the LPG pulse at the manifold end is, for 300mm pipes, five times the original duration at the injector, and even greater for 600mm pipes. The narrow sprays and the amount of evaporation that occurs before the fuel enters the manifold explains the differences in engine torque and in-cylinder mixture temperature with the different systems.

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