The Spray Characteristics of a Liquid Phase LPG Port Injection Type Injector for a Remodeled Diesel Engine

摘要

In present days, most of researches concerned with vehicle engines have been performed to reduce vehicle emissions and to improve engine efficiency. For the requirements, LPG (Liquefied Petroleum Gas) engine which has lots of advantages such as low emission level, cheaper fuel cost and enough infrastructures has had lots of interest as an alternative fuel engine. What is more, it has a low emission level of CO_2 well-known as the factor of 'Global Warming,' thus the use of LPG engines has been increased. Especially since MPI (Multi Point Injection) type LPLi (Liquid Phase LPG injection) system was used for the fuel supply system, disadvantages of LPG engine such as low engine performance, decreased charging efficiency and cold starting difficulty have been improved and prejudices against LPG engines have been changed a lot. In light of this, the motion to use LPLi engines instead of diesel engines has been increasing. Therefore in this research, spray visualization experiment was performed to find the optimal LPG injection conditions for a modified diesel engine. And the effect of the ambient pressure on spray characteristics of LPLi injector was investigated in a high pressure chamber which simulates the air charging condition of the base diesel engine. As a result, the ambient pressure affects both injection quantity and spray structure. And the results provide valuable information on macroscopic spray structure and design factors for modifying LPG injection system for the engine.