Design and testing of a highly loaded mixed flow turbine

A method of designing a new generation of highly loaded mixed flow turbines for turbocharger application is described. A review of the published work concerning radial turbines and closely related to mixed flow turbines is presented. A 1-D design method was developed. It is used to define the over all turbine dimensions and to analyse its performance at the off design conditions. The method is applicable to both radial and mixed flow turbines. A series of designs had been produced and then analysed by the off design performance prediction method. The effects of several geometrical parameters on the performance of the designs were investigated. This had led to the selection of an optimum rotor design for further analysis. An analytical method based on the Bezier polynomials is used to define the three dimensional blade geometry . The rotor geometry is optimised by means of a quasi­ three-dimensional method for the flow analysis. The effect on the flow inside the rotor of three factors influencing the blade geo metry has been investigated. These consist of the rotor blade angle variation along the leading edge, the rotor length and the blade curvature. Two mixed flow turbine prototype s have been manufactured and experimentally tested. These differ mainly in the rotor inlet, which is a constant blade angle in one case, and a notionally constant incide nce ang le at design conditions in the other case. The former turbine showed significantly higher efficiencies across the operating range, and possible reasons for this are discussed. The experimental analysis concerns the measurement of the turbine overall performance, the pressure distribution along the rotor shroud and the flow field downstream of the rotor exit.Open Acces

Comparison between numerical models and CHENSI with experimental data (MUST) within the case of the 0° approach flow.

The MUST wind tunnel data set served as a validation case for obstacle-resolving micro-scale models in the COST Action 732 “Quality Assurance and Improvement of Micro-Scale Meteorological Models”.The code used for the numerical simulation is code CHENSI, simulations carried out showed a certain degree of agreement between the experimental results and those of the numerical simulation, they highlight the need for proceeding to an experimental campaign but with more measurements and the need for having a good control of determining factors in the exploitation of its results. The aim is to explain the experimental data obtained by atmospheric wind on the physical model. The site company of Mock Urban Setting Test (MUST) was selected to be simulated by the code CEN CHENSI developed by the team of Dynamique of l’atmosphere Habitee of LME/ECN. The code was based on (K- ε) model of (Launder and Spalding). For the integration of the PDE (Potential Dimensional equations) constitute the mathematical model, the finite volume method of (Ferziger and Peric) was used within the decade disposition of unknowns MAC of (Harlow and Welck) for the discretisation of PDE terms. The boundary conditions were imposed according to the wall laws (In ground and on buildings) or within Dirichlet condition (Inlet boundary) or of Newman (Outlet boundary or top limit). The numerical domain used was comparable to the one of the atmospheric wind experiences within a three-dimensional Cartesian mesh. Numerical results presented in this study for the mean flow field, turbulent kinetic energy in the direction of wind incidence 0°. For an objective comparison of the CHENSI model performances within other European codes used for MUST configuration simulation. The results obtained by the numerical modelling approach are presented in this paper

Performance prediction of a mixed flow turbine

Turbochargers are widely used in Diesel engines as a means of increasing the output power. Most of them are fitted with radial or mixed flow turbines. In applications where high boost pressure is required, radial turbines are replaced with mixed flow turbines with positive rotor inlet blade angle so that they can achieve a maximum efficiency at a lower value of blade speed to isentropic expansion velocity ratio than the usual 0.7 (for radial turbines). This study, performed with the ICEM and CFX softwares of ANSYS, presents a numerical performance prediction of a mixed flow turbine for a wide range of rotational speeds and pressure ratios. The influence of the clearance between the rotor tip blades and the casing on the turbine performances is also investigated. A simulation of the turbine under pulsed inlet flow conditions is also presented