Optimization of Performance of Compression Charge Ignition Engine

Abstract

The internal combustion engines are used for transport and for power generation. These engines include spark ignition , compression ignition and gas turbine. Among these engines diesel is the most popular, it has higher thermal efficiency, higher re liability and durability as compared with spark ignition and gas turbine. However, the engine faces two challenges; the environment unfriendly exhaust emissions and the fluctuating fuel prices. The exhaust emissions from diesel engine have significant negative impacts on environment, human and plants. The depletion of the fossil fu els deposits and political instabilities in oil producing countries have been the cause of fluactuating fuel prices. Further, the thermal efficiency of diesel engine as com pared to other engines such as steam turbines is below 50%. As the environmental issues have become of great concern across the globe, the international environmen tal regulatory bodies have set stringent emission control standards and fuel economy regulations. This has made researchers to search and develop higher performance engines with near to zero emissions and environmental friendly fuels. These research areas includes integrated emission control technologies, alternative fuel vehicle tech nology and low temperature combustion. Fossil fuel and diesel engine remain the preferred power source and means of transport and for power generation for the fore seeable future. The capital investment, supporting technologies, the thermodynamic properties of the diesel fuel present compact and fuel efficient systems among other benefits. Therefore the world will continue to operate with these systems, however technologies of reducing the pollutants resulting from these emissions such as NOx, CO and HC have to be developed. Among these technologies is retrofit. When ap plied to IC engine, it is the addition of new technology or features to older systems to improve efficiency and reduce emissions. Optimization of existing plant compo nents, adaptation of the plant for new and or changed products and guaranteed spare parts availability are some of the benefits of retrofit technology. Among these modi fications include cylinder head modifications for fitting injector nozzle with different design configuration, installation of catalytic converter and exhaust gas recirculation. and installing exhaust gas recirculation system. This was done by incorporating an xix electronic control unit (ECU) onto the set up. The ECU facilitated the variation of injection timing and the injection pressure. The amount of EGR was varied manually by using a regulating valve on the EGR system. A single cylinder (conventional) diesel engine was used as the test engine. The diesel engine was coupled to a hydraulic dy namometer. Engine and dynamometer cooling water systems, electronic control unit and exhaust gas recirculation (EGR) were installed as a part of the set up. The range of injection pressure was varied between 180 to 230 bars, the speed from 800 to 1650 rpm, the injection timing was retarded 5o BTDC and advanced 9o BTDC respectively while the EGR was varied up to 30 % of exhaust gas. To measure the performance and the exhaust gas emissions, a hydraulic dynamometer and the gas analyzer were used respectively. It was found that the electronic control unit can be designed and assembled from the equipment and materials which are locally and readily available. Further, it was found that the assembled ECU can be incorporated as an external system to an existing diesel engine and can be used to vary engine operating param eters. The results obtained show that the premixed charge compression engine had improved performance and reduced exhaust emissions. The best operating conditions were found to be at an injection timing of 30o BTDC, injection pressure of 200 bar and at 5 kg load. The performance in terms of thermal efficiency of the premixed charge ignition engine was found to be 33.35 % while emissions of CO and HC at 1.2 % and 185 ppm respectively. In addition, thermal efficiency for the base line was found to be 32.6% while emissions of CO and HC at 1.3% and 168 ppm respectively. Therefore improvement of 2.3 % in thermal efficiency and 7.6% reduction in emissions was realized. The results also showed that with medium load, up to 20 % of EGR would be effective in reducing exhaust emissions. The improved engine performance and the reduced exhaust emissions shows that the retrofit technology used in this work can be applied to the existing diesel engines and power plants for better engine performance and reduced exhaust emissions.