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The role of biomass energy is becoming more and more important in renewable energy. As biomass energy utilization has the problems of collection and transportation. A small-scale dispersed power source is required. Biomass gasification CHP (combined heat and power) system converting biomass energy into gas for CHP at high temperature is one of the most effective solutions because of its high energy conversion efficiency. Dual fuel engine which can ignite low calorie biomass gasification gas by injected light oil is suitable for woody biomass gasification gas of changing calorie and amount. The effect of gas ratio which is defined as gas energy ratio in total inlet energy, injection timing, throttling and gas composition on the performance and exhaust emission of dual fuel engine was investigated by using 2 kinds of model gas which consists of H₂, CO, CH₄, CO₂ and N₂. As gas ratio of low calorie gas increases, NOx and thermal efficiency decrease but CO and THC increase.

The main objectives of this research are to establish the practical use of DME (Dimethyl ether) diesel engine with high performance and clear the emission regulation in urban area by securing a stable DME supply system and the engine durability and reliability. In this research, the fuel injection system including a fuel supply system that provides a long-term stable engine operation was developed. The effect of thermal efficiency improvement using larger EGR (Exhaust gas recirculation) was not found by changing injection parameter. The decrease of suction temperature by cooling the EGR was the most effective in thermal efficiency improvement at the target NOx (Oxides of nitrogen) of 100 ppm (13%O2 conversion). With DME, the amount of PM (Particulate matter) with EGR was extremely low compared with diesel fuel. The endurance test was conducted for a continuous operation of 5000hrs and the engine and fuel system durability were achieved.

Oxidation catalyst performances are studied under HCCI (Homogeneous Charge Compression Ignition) and SI (Spark ignited) conditions using a model gas reactor and with natural gas fuelled HCCI and SI engines. The characteristic emissions of HCCI engines are high levels of CO and hydrocarbons, and temperatures as low as 120°C. Conventional oxidation catalysts typically light off at around 200°C, well above these temperatures. The oxidation catalyst for a HCCI engine is required to be active at low temperature, and be durable. Test results will be shown for bench-scale experiments for a series of catalyst formulations. Some catalyst formulations show excellent performance. The HCCI-tailored catalyst exhibits complete conversion of CO under HCCI engine emission conditions with various loads. Under SI conditions, high conversion efficiencies are observed for methane and non-methane hydrocarbons.

In this study, it was attempted to operate the 4-cycle multi cylinder natural gas engine introduced PCCI combustion system without electric heater for intake air heating. In experiment, by optimization of the compression ratio and in addition to the control of spark ignition timing, the engine could be operated using only intake air heating with coolant water. The results showed that the suppression of the auto-ignition timing variations among cylinders owing to the independent spark timing control of each cylinder leads to the improvement of engine output, fuel economy and exhaust emissions. Furthermore, this paper describes the engine starting and corresponding change of engine load on electric demand on generator. The stable operation could be achieved by using spark ignition, controlling of excess air ratio and intake air temperature during change the engine load from idle to rated power.

A novel EGR (exhaust gas recirculation) method by means of the intake-valve pilot-opening has been demonstrated using a single-cylinder test engine, in order to control the combustion and to reduce the energy loss due to intake-gas pre-heating in a natural gas HCCI (homogeneous charge compression ignition) engine. The intake valve, together with the exhaust valve, is slightly opened at the beginning of the exhaust stroke. Then, part of the burnt gas, which has a high temperature, is introduced into the suction pipe backward, resulting in an increase in the intake-gas temperature. The EGR rate can be varied successfully up to about 40% by using the specially designed camshaft and the valve control device, which can delay the closing timing. The effect of the EGR rate on engine performance and emissions has been investigated under the condition that the temperature of the fresh mixture and the fuel consumption rate are kept constant.