Investigation On Thermoelectric System Used For Exhaust Gas Waste Heat Recovery Of Heavy Duty Diesel Engine

With the increasingly serious problem of energy and environment,it is significant to enhance the efficiency of diesel engine which is one of the main oil-consuming equipment.The related research indicates that about one-third fuel energy in a typical diesel engine is taken away by the exhaust gas with high temperature and great quality.Hence,engine efficiency could greatly increase when recovering such a waste heat.As a technology to convert thermal energy into electric energy,thermoelectric technology takes advantage of its simple structure,high reliability and no moving part,which has broad foreground of application to the waste heat recovery of diesel engine.Based on the summarization of different semiconductor thermoelectric power generation system and the specific characteristics of the exhaust,this paper designs a cylindrical-type thermoelectric generating system for a heavy-duty diesel.The heat-flux coupling model of heat exchanger by Fluent software,one-dimensional power model,and the model of exhaust back pressure are combined to simulate the semiconductor thermoelectric power generation system.Results show that the temperature of collector increases at first and then becomes stable in direction of the flowing path of exhaust;the output power of thermoelectric generation at the front of the collector is small;the loss of exhaust back pressure is about 20% of total output power and cannot be ignored.By using the combined model of semiconductor thermoelectric power generation system,this paper optimizes the system structure with different guiding devices.The results show that systems with guiding devices have the higher efficiency than the basic system.The guiding devices generate a larger increase of thermoelectric generator efficiency than that of collector efficiency.Guide device has little influence on the mean temperature of collector,but changes the location of high-temperature region.With an increase in the size of guiding device,the loss of exhaust back pressure increases.By the simulation and the optimization,the largest net power output has an significant increase of 75.2% at the optimized size of guiding device.