One-dimensional engine model
A one-dimensional model has been developed to predict the performance of a radial-inflow turbine submitted to instable flow conditions. Different from other approaches before, the turbine has been simulated by separating the effects of casing and rotor on the unsteady flow and by modeling the multiple rotor entries from the volute.
It is a simple and effective way to represent the turbine volute by a network of one-dimensional pipes, in order to capture the mass storage effect due to the system volume, as well as the circumferential variation of fluid dynamic conditions along the volute, responsible for variable admittance of mass into the rotor through blade passages. The method developed is described, and the accuracy of the one-dimensional model is shown by comparing predicted results with measured data, achieved on a test rig dedicated to the investigation of automotive turbochargers.
Two-stage turbocharging
The major advantage of two-stage turbocharging comes from the fact that two machines of normal pressure ratio and efficiency can be used. High overall pressure and expansion ratios may be developed using conventional turbochargers. The primary disadvantages are the increased cost of the additional turbocharger plus intercooler and manifolding.
Additionally, Interstage intercooling is a complication, but the reduction in temperature at the inlet of the HP compressor has the additional advantage of reducing the HP compressor work for a given pressure ratio, since this is a function of compressor inlet temperature. This increases the effective over-all efficiency of the turbocharging system. The turbines also benefit from the lower expansion ratio per stage. At lower expansion ratios, the turbines can operate much more efficiently than would be the case with a single-stage system. The two-stage systems, through greater turbocharger system efficiency, provides a higher boost pressure, greater specific air consumption and therefore lower exhaust valve and turbine inlet temperature.
Reference
A detailed one-dimensional model to predict the unsteady behavior of turbocharger turbines for internal combustion engine applications. Federico Piscaglia, Dec 2017.
Efficiency improvement and NOx emission reduction potentials of two-stage turbocharged Miller cycle for stationary natural gas engines. Ugur Kesgin, 189-216, 2005.
A simplified turbocharged diesel engine model, M P Ford, Vol201
Post time: Oct-26-2021