The Practical Design of Turbocharger Turbines Using a Throughflow-Based Optimisation Process

Abstract

The modern trends in automotive turbocharger applications are towards the boosting of smaller internal combustion engines and more advanced systems including two-stage, turbo-compounding and hybrid electric-motor assist. Off-the-shelf turbochargers will become a smaller share of the market and the choice of major parameters for the compressor and turbine, e.g. speed and diameter, will fall outside of the manufacturer’s knowledge base. The selection of the compressor and turbine may even be independent. The only certainty is that the turbomachinery will have to be small, cheap and efficient. To provide some guidance to the turbine designer, this paper presents the results of a study in which practical designs have been generated to cover the range of conceivable parameters, presented in non-dimensional terms to provide general applicability. All the designs are generated using a throughflow-based optimisation system in which the candidate geometries are assessed against mechanical as well as aerodynamic and inertia targets. Analysis of the results gives clues to the form of the basic empiricism that would be of use in the preliminary design of automotive turbocharger turbines.

3D Numerical Modeling of Zeotropic Mixtures and Pure Working Fluids in an ORC Turbo-Expander

“…) should be close to 0.7 for most efficient turbines, where C0, the spouting velocity, is the velocity of a jet if the gas was expanded isentropically through a nozzle, and equals √2 ℎ (see Cox [21]). …”

“…Table 1 provides physical properties, safety, and environmental data of the candidate working fluids. There are several recommended optimal boundaries that should be fulfilled in order to operate radial turbines efficiently in the cycle [4]: ) lies in the range 0.5-0.7 for automotive turbocharger turbines, while the value of tip Mach number is increased to 1, and choking must be considered for low-temperature turbines (refrigerant expander) (see Cox [21]). …”

“…(b) The upper limit of the tip speed must be within 370 m/s [4]. (f) The tip Mach number M U = U 2 a 2 lies in the range 0.5-0.7 for automotive turbocharger turbines, while the value of tip Mach number is increased to 1, and choking must be considered for low-temperature turbines (refrigerant expander) (see Cox [21]). (g) The blade speed ratio (…”