Overall Efficiency Optimization Of Diesel Engines Using Electronic Cooling System And Waste Heat Recovery Thermoelectric Generator

Among different waste heat recovery technologies,thermoelectric conversion technology has received extensive attention of academia as results from its merits of small device,light weight,simple structure and no moving parts.When it is used in vehicles,thermoelectric generator(TEG)usually use the engine cooling system as the cold source.But it will bring the extra heat release to the cooling system and increase the cooling consumption.This is the power coupling relationship between the thermoelectric generator and the cooling system.This paper mainly explores how to optimize the system overall efficiency through the TEG design and by-pass optimal control under this coupling relationship.In order to improve the overall efficiency of engine and thermoelectric generator system,an experimental platform consisted of engine,electronic cooling system and thermoelectric generator has been built.And the integrated electronic control cooling diesel engine and thermoelectric generator system simulation model is built and verified based on a 12 L heavy diesel engine.The multi-level efficiency evaluation system has been presented.The research explores the influence of TEG main parameters on system overall efficiency and gives the matching principles under the engine 1300rpm-80% condition.The results show that increasing the convective heat transfer area of exhaust pipe can better improve the overall efficiency than increasing that of the coolant pipe.Under the same thermoelectric ZT value,choosing higher Seebeck coefficient or lower thermal conductivity thermoelectric materials both can improve the system overall efficiency.When the higher Seebeck coefficient thermoelectric material is used,there is a optimal thermoelectric materials laying area making the system overall efficiency highest.When the external load resistance is bigger than the TEG internal resistance,the system overall efficiency is the highest.Besides that,the study also explores the fuel saving in all engine conditions and road conditions.The results show that,under the coupling effect between TEG and cooling system,for one thing TEG is suitable for the low speed and high load conditions of engine,for another thing the road condition fuel saving rate has the positive correlation with acceleration time,the correlation coefficient is 0.66.Through the above research,TEG has different effects on the system overall efficiency under different engine conditions.It needs the by-pass real-time predictive control to avoid TEG working at overall efficiency deteriorating conditions.Therefore,the research also comes up with the simplified model-building method and uses the model built by this method to predict the system overall efficiency influence.Based the influence,the by-pass is controlled.Under HUDDS road condition the fuel saving rate of engine and TEG system using the by-pass optimal control is 0.21%.The unused is 0.15%.