Mitja Mori

HEAT TRANSFER EVALUATION METHOD IN COMPLEX ROTATING ENVIRONMENTS EMPLOYING IR THERMOGRAPHY AND CFD

This article presents a measuring method for determination of convective heat transfer in rotating environments. The method is used to obtain temperature and Nusselt number distributions on optically accessible objects inside real operating environments, without the need for implementation of complex surface heat flux measurements. Temperature maps of the observed surfaces are acquired non-intrusively by infrared (IR) thermography, whereas heat flux data is computed numerically by computational fluid dynamics (CFD) tools. The method was employed on a rotating hollow blade, heated internally by secondary air flow. Experimental and numerical results for the observed blade side are compared in terms of surface temperature 2D distributions. Temperature distributions are further statistically evaluated and show good agreement, which is the basic precondition for combining experimental and numerical data by the method. Results are presented in terms of combined experimental-numerical Nusselt number shown as two-dimensional distribution on the blade pressure side.

Numerical Modeling of Heat Transfer and Flow Phenomena in an Axial Rotating Rotor Cascade

This paper presents a study of heat transfer in a rotating axial rotor. The study was done on the basis of computational fluid dynamics simulations and validated with an infrared thermocamera experimental setup. The influence of full turbulence vs. Menters boundary layer method was studied in terms of heat transfer and flow phenomena. Additionally it was found out that a thin paint layer has a major influence on heat transfer phenomena and acts as insulation. For comparison of numerical results with experimental, a model of the actual rotor was established. Results were found to be in good agreement, so the effect of rotation on heat transfer was studied. Results are presented in terms of Nusselt number distribution and an empirical model of heat transfer.

A Single-Stage Centripetal Pump—Design Features and an Investigation of the Operating Characteristics

In this paper, we present an experimental and numerical investigation of a single-stage centripetal pump (SSCP). This SSCP is designed to operate in the pump regime, while forcing the working media through impeller-stator flow channels in the radial inward direction. The measured performance curves are characterized by a hysteresis, since the throttle-closing performance curves do not correspond to the throttle-opening performance curves throughout the whole operating range. A computational fluid dynamics (CFD) model was developed to establish these throttle-closing and throttle-opening performance curves. The flow conditions obtained with the CFD simulations confirm that the hydraulic behavior of the SSCP is influenced by the partial circumferential stall that occurs in the impeller-stator flow channels. It was shown that the inflow conditions to the impeller-stator assembly considerably influence the flow rate of the stall cessation, the size of the hysteresis, and the head generated during part-load operations.