Publications

Work on rotating stall and its related disturbances have been in progress since the Second World War. During this period, certain "hot topics" have come to the fore-mostly in response to pressing problems associated with new engine designs. This paper will take a semihistorical look at some of these fields of study (stall, surge, active control, rotating instabilities, etc.) and will examine the ideas which underpin each topic. Good progress can be reported, but the paper will not be an unrestricted celebration of our successes because, after 75 years of research, we are still unable to predict the stalling behavior of a new compressor or to contribute much to the design of a more stall-resistant machine. Looking forward from where we are today, it is clear that future developments will come from CFD in the form of better performance predictions, better flow modeling, and improved interpretation of experimental results. It is also clear that future experimental work will be most effect

The present study aims to investigate the interaction between a last-stage steam turbine blade row and diffuser. This work is carried out using computational fluid dynamics (CFD) simulations of a generic last-stage low-pressure (LP) turbine and axial–radial exhaust diffuser attached to it. In order to determine the validity of the computational method, the CFD predictions are first compared with data obtained from an experimental test facility. A computational study is then performed for different design configurations of the diffuser and rotor casing shapes. The study focuses on typical flow features such as effects of rotor tip leakage flows and subsequent changes in the rotor–diffuser interactions. The results suggest that the rotor casing shape influences the rotor work extraction capability and yields significant improvements in the diffuser static pressure recovery.

In this paper, we present an extensive numerical study on the interaction between the downstream fan and the flow separating over an intake under high incidence. The objectives of this investigation are twofold: (a) to gain qualitative insight into the mechanism of fan–intake interaction and (b) to quantitatively examine the effect of the proximity of the fan on the inlet distortion. The fan proximity is altered using the key design parameter, L/D, where D is the diameter of the intake, and L is the distance of the fan from the intake lip. Both steady and unsteady Reynolds-averaged numerical simulations (RANS) were carried out. For the steady calculations, a low-order fan model has been used, while a full 3D geometry has been used for the unsteady RANS. The numerical methodology is also thoroughly validated against the measurements for the intake-only and fan-only configurations on a high bypass ratio turbofan intake and fan, respectively. To systematically study the effect of fan on t

This paper presents a low-order model applying the immersed boundary method on smeared geometry. It is thus able to represent the effect of turbomachinery within a complex system. Assessment of this model on the NASA rotor 67 has been made under clean flow conditions. Good agreement has been achieved between the immersed boundary method on smeared geometry model, experiments, and a high-fidelity computational fluids dynamics model. For high-speed conditions, about within 0.5, 1, and 1% agreements are achieved on the pressure ratio, efficiency, and choking flow, respectively, between immersed the boundary method on smeared geometry model and the experiment. The capability of the model capturing the fan’s behavior under inlet distortion has also been assessed under the flow with a level of 10% distortion of the total pressure, which covers a 120 deg sector. The nonuniform work input of the fan, which is one of the key features of the fan–distortion interaction, has been captured by the i