Dielectric-Barrier Discharge Plasma Actuators for Flow Control

Numerical Analysis of the Fluid Flow in the First Stage of a Two-Stage Centrifugal Pump With a Vaned Diffuser

Nonoptical techniques currently used to measure flows in turbomachine rotors are reviewed, with particular reference to the measurement of the three-dimensional mean velocity, turbulence intensity, Reynolds stresses, static and stagnation pressures, and blade surface measurements. The high level of sophistication of rotor flow measurement techniques is demonstrated. Rotating probe measurements are well suited for low- and moderate-speed turbomachinery, while stationary quick-response probes (hot-wire and pressure probes) are applicable both in low- and high-speed turbomachines. Hot-wire probes, blade pressure transducers, and telemetry systems will provide the urgently needed basic information on steady and unsteady flow through a blade passage, including blade boundary layer, shock configuration, leakage and secondary flows.

Techniques for aerodynamic and turbulence measurements in turbomachinery rotors

A LES investigation of off-design performance of a centrifugal pump with variable-geometry diffuser

Numerical study on swirl cooling flow, heat transfer and stress characteristics based on fluid-structure coupling method under different swirl chamber heights and Reynolds numbers

A computational study
has been conducted to analyze the performance of a centrifugal compressor under
various levels of impeller-diffuser interactions. The study has been
conducted using a low solidity vaned diffuser (LSVD), a conventional vaned
diffuser (VD) and a vaneless diffuser (VLD). The study is carried out using
Reynolds-Averaged Navier- Stokes simulations. A commercial software ANSYS
CFX is used for this purpose. The extent of diffuser influence on impeller flow
is studied by keeping the diffuser vane leading edge at three different radial
locations. Detailed flow analysis inside the impeller passage shows that the
strength and location of the wake region at the exit of impeller blade is
heavily depended upon the tip leakage flow and the pressure equalization flow.
Above design flow rate, the diffuser vane affects only the last twenty percent
of the impeller flow. However, below design flow rate, keeping vane closer to
the impeller can cause an early stall within the impeller. Small negative
incidence angle at the diffuser vane is helpful in order to reduce the losses
at the impeller exit.

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Study of Secondary Flow Modifications at Impeller Exit of a Centrifugal Compressor

The effect of Gurney flap height and mounting position on the head coefficient of a centrifugal fan at different Reynolds numbers is investigated experimentally. Quarter round Gurney flap of 1.0, 1.5, 2.0 and 2.5 mm height is mounted at three different positions, S=1.00 (impeller tip), S=0.95 and S=0.90 on the pressure surface of the impeller blade tip. Performance tests are carried out on the centrifugal fan at five Reynolds numbers corresponding to five rotational speeds of 1100, 1500, 2000, 2500 and 2900 rpm respectively. From the performance curves it is found that the fan head coefficient increases significantly with Gurney flaps at low Reynolds numbers and increases marginally at high Reynolds numbers. Effect of Reynolds number on the head coefficient is considerable for the baseline fan and found to be negligible for the fan with Gurney flaps, for all combinations of Gurney flap mounting position and height. The head coefficient of the fan improves as Gurney flap height increases but the improvement is marginal after certain height of Gurney flap. The head coefficient of the fan deteriorates when Gurney flap is mounted away from the impeller blade tip.

Effect of Gurney flap Height and Mounting Position on the Performance of a Centrifugal Fan

Tip leakage flow has an important role in deciding the stable operating conditions of centrifugal compressor. It has been found from the open literature that the downstream diffuser vanes have significant impact on the tip leakage flow of the impeller. The present computational study is aimed to understand the effect of downstream diffuser vane on the tip leakage flow of a centrifugal compressor particularly in the near stall region. The study is carried out using Reynolds-Averaged Navier-Stokes simulations. A commercial software CFX is used for this purpose. The diffuser vane leading edge and solidity are varied and its effects on tip leakage flow are noted. The interaction between the tip leakage flow and the through flow is studied in detail. The leakage flow near the trailing edge region has a profound effect on the jet-wake flow structure at the impeller exit.

Nekkanti Sitaram

Papers

Study of Secondary Flow Modifications at Impeller Exit of a Centrifugal Compressor

Effect of Gurney flap Height and Mounting Position on the Performance of a Centrifugal Fan

CFD Prediction of the Blade Tip Leakage Flows of Centrifugal Compressor at Near Stall Conditions