Effect Of Exhaust Energy Quality Of Diesel On Efficiency Of Turbine Generation Energy Utilization

For a long time,the internal combustion engine working processes,as well as a variety of advanced engine technology(such as pressurization,HCCI)has been studied,although these technologies can improve indicated thermal efficiency but the efficiency just change little.To maximize the efficiency of internal combustion engines,from exhaust gas energy recovery and utilization point of view,starting a new direction for the study of energy-saving and emission cutting of internal combustion engine.Studies have shown that different ways of exhaust energy recycling ask for different qualities of exhaust gas energy;Combustion processes in cylinder are complex,the same to the exhaust gas energy qualities.Therefore,the exhaust gas energy quality analysis under different conditions can be achieved fully and rationally utilizing engine exhaust gas energy,and promote the improvement of exhaust gas energy recycling technology,achieve the goal of energy conservation and emission reduction.On the basis of building a comprehensive classification method of exhaust energy quality,this paper studies the effect of exhaust energy quality on energy efficiency and power generation efficiency of power turbine exhaust gas.Firstly,selected a YND485 Q diesel engine and a J56 power Turbo as experimental equipments and built test system.Then,through analyzing test datum to find the influences which exhaust gas energy quality posed on linear head loss and the utilizable energy to power turbo;Lastly,with the help of Matlab/Simulink achieved simulation of power Turbo-deceleration institutions-power system combined model,and calculated out effects of exhaust energy quality changes law to efficiency of exhaust turbo generator system.Results show that from the perspective of thermodynamics,available exhaust energy accounts for(that is,turbo front exhaust enthalpy minus the enthalpy of exhaust gases at room temperature)19% ~30% of diesel's total energy(the product of the mass flow rate of the diesel and diesel fuel higher heating value).Even engine exhaust contains a large amount of available energy,utilization of the power turbine for this part of energy is just 5.69%~15.52%,and when the engine works at 2800 rpm with 90%loads,utilizing rate to available energy reaches to the top of about 15.52%.In the quality of exhaust gas energy comprehensive grade division method,power turbine inlet exhaust energy levels of quality,power turbine exhaust energy levels of quality,quality and grade of energy difference of the range is 2.69~5.98,1.95~4.91 and0.70~1.15.When 2800 rpm with 75% loads,the quality of exhaust gas energy leveldifference reaches a maximum value,corresponding to the turbine of energy efficiency is also the largest value.Compared with the temperature partition method,the range of energy quality level of the exhaust energy after the vortex front and the vortex is reduced,and the energy level difference value is increased.At 2800r/min speed,the load is increased from 75% to 90%,and the exhaust turbine energy recovery efficiency is maintained in a good and steady state.With the increase of the energy quality of the exhaust gas,the entropy efficiency of the power turbine increases first and then decreases.The energy loss increases at first and then decreases to a minimum,and then increases.When the quality of exhaust gas energy level of about 4.75,exhaust outlet pressure of the turbine,turbine inlet pressure and the turbine inlet exhaust temperature respectively 9.83 kP,22.08 kP and 670 K.at this time of turbine expansion than 2.27 and optimal,power turbine isentropic efficiency reached its peak,turbine power available to the minimum loss.The simulation results show that,when the exhaust gas energy quality rank number is 4.70 and turbo with 14.22 kW isentropic power and correspondingly turbine with50900 rpm,the output toques of gearbox is not enough to rotate generator.The generator begins to rotate when the exhaust gas energy quality is greater than 4.74 and the exhaust gas energy quality will linearly increase at over 6200 rpm.When generator works stability,the output voltage with a 28 V amplitude is stable and changes according to the sine wave over time,amplitude of 28 V,and the output current is 0.56 A,when loads is 50.On the whole,when the exhaust gas energy quality rank is more than 4.70,the exhaust energy for recycling can be completely convert into electricity is about 2.12 kW to 3.08 kW,and efficiency of gas turbine power generation of energy recycling system is from 5.49% to 10.14%.