The Research Of Overallscheme For Engine Exhaust Waste Heat Recoery Based On Organic Rankin Cycle

Organic Rankine Cycle (ORC) is an effective technique to recovery waste heatfrom engine exhaust. Advantages of ORC are high efficiency, simple system,environment friendly, and so on. With the aggravation of China’s energy problems,the recovery and utilization of engine exhaust waste heat have important practicalsignificance, it is helpful to solve China’s energy pressure, and can effectively inhibitthe environmental pollution. The total waste heat recovery system is theoretically andsimulated investigated on two aspects, and preliminary study of test. Detail of thiswork is as follows:1The selection of working fluid in ORC system was presented in this work. Bycomparing working fluid’s six properties of environment protection performance,chemical stability, safety, cost, and critical parameter, boiling point and solidificationtemperature, and fluidity, heat-exchange performance and price, R245fa was selectedas the working fluid in the ORC system.2The cycle process of ORC was analyzed by the mathematical model, and theeffect of condensing temperature and evaporating pressure on ORC systemperformances was studied. The results showed that for a fixed cooling temperature,net work was increased with the increase of the evaporating temperature. For a fixedevaporating temperature, net work was increased with the increase of the coolingtemperature. For a fixed exhaust mass flow rate and temperature, evaporating rateincreased with the decrease of the evaporating pressure.3The optimal evaporating pressures under different engine speed were determinedaccording to the simulating results gained under various engine operating conditions.The results showed that when the engine speed was lower than2000r/min, the optimalevaporating pressure is1.2MPa. When the engine speed was from2000r/min to2600r/min, the optimal evaporating pressure was1.6MPa. When the engine speed washigher than2600r/min, the optimal evaporating pressure was2.4MPa. In addition, thiswork analyzed the effect of different position on working fluid state under differentengine speed. The results also showed that the state of working fluids can be dividedinto four categories according to its positions in the system under all engine speedsand evaporating pressures. It was also confirmed that most of the optimal operatingconditions were found in Case3.4This work used GT-Power to build the BJ493ZLQ3diesel engine model and ORCsystem model. The simulating results showed that based on the validated experimental data of the engine, the uncertainty between the simulating and test results was lowerthan5%. Therefore, the ORC system model is built, based on the engine model. Theuncertainty between simulating and analyzing results was lower than10%. The resultsalso showed that the results of thermodynamic model could be as a reference fordesigning the experimental procedure.5The parts specifications were carefully selected to accomplish the construction ofthe experimental system, based on the operating characteristics of diesel engines. Themain work included that the selecting of evaporator, single screw-expander, condenserand working fluid pump in ORC system, and the designing of working fluid tank andsystem pipe. In addition, the system working process was designed, which mainlyincluded four cycles that is engine cycle, ORC, condensing cycle, lubrication cycle.The system was adjusted under different engine operating conditions.