Application Of Compound Combustion Mode Of Diesel/Methanol To Turbo-Charged Diesel Engine

The main point of this study is to investigate the burning principle and the practicability of the diesel/methanol compound combustion. Based on the analysis of the technical state of the diesel engines and the resources of the energy in our country, this study brings forward firstly a new combustion theory named compound combustion theory (CCT). The main purpose of CCT is to use the merits of different fuels to realize the high efficiency and lean combustion, and CCT is composed of two stages of the combustion occurring in diesel engine, the one stage adopts conventional diffusion combustion mode using diesel fuel only at low load, starting as well as warming up periods, and the other one utilizes Quasi-HCCI (homogenous charge compression ignition) mode, which is completed by pre-mixed alcohol formed in intake manifold ignited by diesel fuel at other operating conditions. Fully using the characteristic of alcohol, CCT used on diesel engines can not only simultaneously reduce the soot (PM) and nitride oxidation (NOx) emissions from the engines, but also avoid the acetaldehyde emissions of the diesel engine burning alcohol at low load. Meanwhile, burning alcohol in diesel engine can reduce the petroleum fuel consumption, which caters to the energy policy in our country.This study modified the a common diesel engine and a turbo-charged diesel engine to alcohol-injection engine according to the needs of CCT, optimized the parameters of alcohol injection start point which has important influence on the engine performance. And then, we thoroughly tested the engine performance including load characteristics and emission characteristics. Analyzed the combustion characteristics of the compound combustion diesel engine. Different styles of pre-mixed alcohol (Single Point Injection and Multiple Point Injection) were adopted on different diesel engines, and the performance of the engine under different pre-mixed alcohol (pure methanol, and raw methanol) has been compared.The experimental results show that the alcohol injection point should start at proper level to engine load, which is approximately 60%～70% of the maximum torque at one engine speed. The burning start point of compound combustion diesel engine is later than that of original diesel engine, but the combustion speed of the former is faster than that of the latter, and max gas pressure of the former is higher than that of the latter. Different from the double-peak heat release curve of the original diesel engine, the heat release curve of the compound combustion diesel engine is close to single-peak curve. The combustion temperature of the compound combustion diesel engine is lower than the original one. The engine performance experiments indicate that the alcohol injection engine is superior to the diesel engine in soot and NOx emission and fuel economy. Moreover, based on the CCT theory, investigated the performance of the engine pre-mixed raw methanol, the results show that the degree of emissions improvement of diesel engine pre-mixed raw methanol is nearly equal to that pre-mixed pure methanol; however, the fuel efficiency of the former is higher than that of the latter. And burning raw methanol has much more potential than that burning pure methanol due to the former cheaper price.Simply changed the original diesel engine to alcohol-injection engine operating in CCT can decrease the emissions of soot and NOx remarkably, and improve the fuel economy at the same time, therefore, the CCT is a significant innovative technology for the theoretic research and the applied foreground in future.