| About 30% of the total energy generated by the engine fuel is discharged into the air with the exhaust gas,resulting in energy loss.The exhaust gas has the characteristics of high temperature,high pressure and high speed,and contains a lot of kinetic energy,pressure energy and thermal energy,so the exhaust energy has great recycling value.The exhaust gas turbine power generation system based on diesel engine can achieve the goal of energy saving and emission reduction.According to the characteristics of engine exhaust,this paper establishes an exhaust energy calculation model.Based on the model,a diesel engine exhaust turbine power generation system with different exhaust pipe lengths is designed and built.The experimental data of different engine conditions and exhaust pipe lengths are measured and analyzed by bench test.The influence of exhaust pipe length on exhaust state parameters and exhaust energy,as well as the loss of exhaust energy along the exhaust pipe are obtained.In addition,the influence of exhaust pipe length on the temperature difference between inlet and outlet of power turbine and turbine speed,the influence of exhaust pipe length on power output and energy conversion efficiency of power turbine,as well as the influence of exhaust pipe length on system power generation and the change characteristics of power generation efficiency of exhaust turbine power generation system are obtained through data analysis.The results show that:When the exhaust pipe length is the same,the exhaust state parameters and exhaust energy increase with the increase of engine condition(speed and load);under the same engine condition,they decrease with the increase of exhaust pipe length,and the exhaust mass flow does not change with the change of exhaust pipe length.The decreasing speed of exhaust temperature,exhaust flow rate,exhaust heat energy and residual kinetic energy in exhaust pipe is mainly affected by engine load,and the decreasing speed of exhaust pressure and residual pressure energy in exhaust pipe is mainly affected by the change of speed.In the exhaust energy,the ratio of waste heat energy is the highest,the residual pressure energy is the second,and the residual kinetic energy is the least.The maximum values of temperature,pressure,mass flow and velocity of exhaust state parameters in the experiment are 1168 K,99.15 kpa,0.0487kg/s and 65.73m/s respectively,and the minimum values are 357 k,6.46 kpa,0.0295kg/s and 22.44m/s respectively.In the exhaust energy,the content of waste heat energy is the highest,followed by residual pressure energy,and the residual kinetic energy is the least.The maximum values of waste heat energy,residual pressure energy,residual kinetic energy and total energy are 20.72 kw,4.2893 kw,0.0531 kw and25.06 kw respectively.Under the same engine condition,the exhaust energy loss increases with the increase of exhaust pipe;in the same exhaust pipe section,the exhaust energy loss increases with the increase of engine condition;with the same exhaust pipe length,the exhaust energy loss increases with the increase of engine condition.The maximum exhaust energy loss in the exhaust pipe section is 15.255 kw,the minimum is 0.18kw;the maximum exhaust energy loss is 19.16 kw when the pipe length is 408 cm,and the minimum exhaust energy loss is 5.92 kw when the pipe length is 260 cm.Under the same engine condition,the temperature difference of turbine inlet and exhaust port,turbine speed and turbine output power all decrease with the increase of exhaust pipe;when the length of exhaust pipe is the same,the temperature difference of turbine inlet and exhaust port,turbine speed and turbine output power all increase with the increase of engine condition.The maximum temperature difference between the inlet and outlet is 49 K,the minimum is 3K;the maximum turbine speed is 17820r/ min,the minimum is 3648 r / min;the maximum power output of the power turbine is 2.17 kw,the minimum is 0.24 kw.The influence of exhaust pipe length and engine condition on power turbine energy conversion efficiency is consistent with that of power generation system.Under the same engine condition,the energy conversion efficiency of the power turbine and the power generation efficiency of the turbine power generation system increase with the increase of the exhaust pipe;under the same exhaust pipe length,the energy conversion efficiency of the power turbine and the power generation efficiency of the turbine power generation system decrease with the increase of the load at the same speed,and increase with the increase of the speed at the same load.The maximum energy conversion efficiency of power turbine is 27.53%,the minimum is16.05%;the maximum energy conversion efficiency of exhaust gas turbine power generation system is 6.72%,the minimum energy conversion efficiency is 1.02%. |
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