Based On The Diesel Engine VGT/EGR Turbocharger Performance Characteristics Studies And Simulation

In recent years, the energy crisis and the pollution of the environment have become increasingly seriously. The study on the energy saving and emission reduction of the internal combustion engine is closely related to the human production and life. It has very important practical significance. Therefore, with the technology of internal combustion engine emission reduction methods continue to emerge, including the variable geometry turbocharger and exhaust gas recirculation technology. As the variable geometry turbocharger technology has the advantages of large torque at low speed, high transient response, and wide adaptability,exhaust gas recirculation technology has the advantages of reducing the heat load of the cylinder and reducing the NOx emissions, so they are considered as the most promising technology for energy saving and emission reduction of internal combustion engine.Combined the variable geometry turbocharger with exhaust gas recirculation technology, the paper realizes the high precision control of nozzle ring of the variable geometry turbocharger by improving the structure of turbine and the installation of VGT module. It guarantees the power, reduces fuel consumption, reduce the carbon smoke-NOx, achieves the expected target.The basic principle of this method is, first of all, the two-phase 4 shoot step stepper motor drives the rotation of the nozzle, changes the turbine flow area by changing the angle position of the nozzle ring, then controls the turbocharger speed and boost pressure. At the low speed, the increasing pressure improves the diesel engine characteristics by reducing the turbine flow area; at the high speed, increasing the area of the turbine gradually, reducing the pressure, makes the turbocharger not over the highest speed, the economy of the diesel engine won’t be damaged at the same time. Secondly, adapting the throttle valve EGR system, by controlling the EGR rate of different working conditions of the diesel engine, the carbon smoke-NOx emissions are decreased. For the purpose, the VGT/EGR system is developed,which is based on the stepping motor drives VGT nozzle ring, realizes the forward movement and the reverse motion; embedded VGT components in the turbine, the space utilization is high and the installation is convenient; the EGR system is placed before the turbine, which can form an external high pressure EGR system.In the GT power software, using the developed system VGT/EGR, on a six cylinder direct injection diesel engine vortex pressure, boost pressure, fuel economy, air intake, emptyburning ratio and carbon smoke-NOx emissions simulation analysis is carried out under different speed and different load. Through the analysis of simulation data shows: firstly,whether the vortex pressure and boost pressure, the system is higher than conventional turbocharger system, with increasing speed, the greater the pressure, easy to implement the effect of EGR; secondly, the air intake and air fuel ratio are relatively high. The EGR rate is above 12% and the fuel consumption is low under the middle low speed. The fuel consumption is too large, but can guarantee the high speed of the power characteristic under the high speed; thirdly, when the NOx emission meets the requirements of the country-four,combined the variable geometry turbocharger with exhaust gas recirculation technology, the carbon smoke of the low speed of four is reduced by 50%. Therefore, compared with the conventional pressurization method, the system has the obvious advantages in the diesel engine energy saving and emission reduction performance.