Combustion and Knock Characteristics of Natural Gas Diesel Dual Fuel Engine

In this study, a single cylinder direct injection diesel research engine was modified to operate as the DDF engine. A gas mixer was installed on the intake manifold to supply natural gas to the engine. Test runs of normal and abnormal conditions were investigated and these include i) determination of diesel engine and DDF engine performance, ii) varying ratios of natural gas and diesel fuel while keeping constant engine speed and torque, iii) varying intake temperature while keeping constant engine speed and amount of natural gas and diesel fuel, and iv) varying amount of natural gas while keeping constant speed and amount of diesel fuel. Operating parameters such as engine speed, torque, and intake temperature, were controlled and recorded. The average cylinder pressure-time data were recorded and analyzed for all test conditions. Results from cylinder pressure-time data analysis such as ignition delay period, premixed combustion phase, diffusion combustion phase, etc, are compared and discussed in the paper.

Moreover, results of abnormal combustion conditions tested in the laboratory are used to explain the possible causes of DDF engine damage in the real situation occurred in Thailand.