Simulation of a Diesel Engine with Variable Geometry Turbocharger and Parametric Study of Variable Vane Position on Engine Performance

Abstract

NomeNclature INtroductIoNDiesel engines will continue to be the prime-movers of future battle tanks owing to their fuel economy, high torque and ease of maintenance. Common rail direct injection (CR DI) technology with electronic engine control is likely to overcome the challenges imposed by extreme weather conditions and other hazards like zero visibility dusty terrains and will replace present mechanical fuel injection systems in the battle tank. Modelling of a turbocharger is of interest to the engine designer as the work developed by the turbine can be used to drive a compressor coupled to it. This positively influences charge air density and engine power to weight ratio. Variable geometry turbocharger (VGT) additionally has a controllable set of nozzles which through a ring is normally electropneumatically actuated by the engine control unit (ECU). This additional degree of freedom offers efficient matching of the effective turbine area for a wide range of engine mass flow rates. At the design point, nozzle less turbine is generally 7 per cent less efficient than the turbine with nozzle blades whereas at off design points it performs better than turbine with nozzle blades 1 . Using VGT, this loss in efficiency can be reduced by matching incidence gas flow angle at the turbine rotor entry to the optimum incidence angle thereby reducing incidence loss which is a major loss at off design operation as proven by experimental studies in 2 . Hence, a CR DI engine with electronic control and VGT offers the advantage of closely matched engine-turbocharger coupled operation at all operating points. But multivariable nature of this control problem makes the system complex and makes control strategies and controller design complicated. In the conventional approach, a map of boost pressure as a function of engine speed and throttle Simulation of a diesel engine with Variable Geometry turbocharger and Parametric Study of Variable Vane Position on engine PerformanceAnand Mammen Thomas #,* , Jensen Samuel J. Modelling of a turbocharger is of interest to the engine designer as the work developed by the turbine can be used to drive a compressor coupled to it. This positively influences charge air density and engine power to weight ratio. Variable geometry turbocharger (VGT) additionally has a controllable nozzle ring which is normally electropneumatically actuated. This additional degree of freedom offers efficient matching of the effective turbine area for a wide range of engine mass flow rates. Closing of the nozzle ring (vanes tangential to rotor) result in more turbine work and deliver higher boost pressure but it also increases the back pressure on the engine induced by reduced turbine effective area. This adversely affects the net engine torque as the pumping work required increases. Hence, the optimum vane position for a given engine operating point is to be found through simulations or experimentation. A thermodynamic simulation model of a 2.2l 4 cylinder diesel engine was developed for investigation of different con...

Numerical Simulation of Two-Stage Variable Geometry Turbine

“…Such an approach does not require any cost and can provide reliable results. A steady-stage 1D simulations include a discretization of the main components of turbocharger flow passage [12][13][14][15]. The lack of experimental data can be overcome by assuming the fictitious compressor map [16].…”

A novel variable geometry turbine achieved by elastically restrained nozzle guide vanes

“…In recent years, the influence of different turbocharging systems on engine performance has been demonstrated extensively using 1D simulation. 25–29…”

“…In recent years, the influence of different turbocharging systems on engine performance has been demonstrated extensively using 1D simulation. [25][26][27][28][29] In this paper, a novel VNT is proposed that it uses elastically restrained guide vanes to adjust the turbine inlet mass flow rate. The rotation of guide vane is driven by the pressure difference between its suction surface and the pressure surface.…”