Division of Information Technology, Engineering and the Environment
School of Advanced Manufacturing and Mechanical Engineering
School of Advanced Manufacturing and Mechanical Engineering
Thesis Abstract
During diesel engine combustion process, a large portion (25-30%) of energy is wasted in terms of heat with the exhaust gases. In case of high performance engines the exhaust heat is used either for turbo charging or supercharging. The concept of Diesel Engine Waste Energy Recovery (DEWER) Technology is meant to capture the thermal energy from the hot exhaust gases and utilize this energy to produce additional power through steam-powered auxiliary drive. The combined power produced by the conventional diesel engine and the waste heat steam-powered auxiliary drive will result in reduced fuel consumption per kWh of power produced and thus reduce the emission of Green House Gases (GHG) per kWh of power.
The technology to be explored relies on the use of a heat exchanger attached to the current exhaust system on a diesel engine. A shell and tube heat exchanger was purchased and installed into the engine. The performance of the heat exchanger using water as the working fluid was then conducted. With the available data, computer simulation was carried out to improve the design of the heat exchanger and an appropriate heat exchanger is designed for this purpose by computer simulation. Two heat exchangers were needed for the purpose of producing additional power using Rankine Cycle, one to generate vapour and the other to generate super heated vapour. These two heat exchangers can be arranged in parallel or series. In case of series arrangement the exhaust gas entered the super heated heat exchanger first and then it entered into the vapour generator. Whereas in parallel arrangement, the exhaust gas was split to pass through both vapour and superheated heat exchanger. Computer simulation was carried out to investigate the effectiveness of the proposed heat exchanger for different working fluid like water, ammonia, and HFC 134a. Interestingly, in case of water as working fluid, it is found that higher power output can be achieved for parallel arrangement below 30 bar working pressure than the series arrangement whereas series arrangement can achieve higher power output above 30 bar working pressure than parallel arrangement. Therefore, in real-applications provision should be made to run the cycle on both arrangements to optimize the overall engine performance. The power output from the turbine is also estimated assuming 85% isentropic efficiency of turbine. It is found that with the exhaust heat available from the diesel engine additional 15%, 13% and 8% power can be achieved by using water, HFC-134a and ammonia as working fluid respectively. The designed heat exchanger is manufactured and experimental setup with designed heat exchanger is in progress.
