Measured and Predicted Secondary Flows in a Centrifugal Impeller

Howard, J. H. G.; Lennemann, E.

doi:10.1115/1.3445380

Cited by 8 publications

(4 citation statements)

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“…Johnson and Moore (1980) considered the equation governing the development of the streamwise vorticity for incompressible inviscid flow which was originally derived by Smith (1957). Howard (1966) later developed a secondary flow model for compressible flow and Lakshminarayana and Horlock (1973) introduced the generalized expressions for secondary vorticity. -pr2& (2)…”

Section: Stationary Unsteadinessmentioning

confidence: 99%

Experimental Investigation of the Steady and Unsteady Relative Flow in a Model Centrifugal Impeller Passage

Abramian¹,

Howard

1993

Volume 3C: General

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The behaviour of the relative flow in centrifugal turbomachines is extremely complex due to the existence of various fluid dynamic phenomena and their interaction. At design and off-design operating conditions, the relative flow is subject to stationary unsteadiness which includes flow separation and wakes associated with passage pressure gradients, secondary flows, and boundary layer stability. It may also be subject to periodic unsteadiness such as is the rotating stall and cyclic flow phenomena induced by the casing. This paper describes detailed measurements of the relative velocity field in a very low specific speed centrifugal pump impeller (Ns=515). Measurements were conducted by means of a recently developed rotating laser-Doppler anemometry system. Detailed quantitative description of the mean and fluctuating components of the primary and secondary velocity fields are presented for an impeller without volute at design, 50% design and shut-off conditions. The flow pattern in this low specific speed impeller with high blade loading is dominated by the relative eddy (a phenomenon also present in potential flow) which has suppressed suction side separation. When the impeller was fitted with a volute, the cyclic variation of the impeller exit flow, induced by the volute at low flow rates, is also presented.

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Section: Stationary Unsteadinessmentioning

confidence: 99%

Experimental Investigation of the Steady and Unsteady Relative Flow in a Model Centrifugal Impeller Passage

Abramian¹,

Howard

1993

Volume 3C: General

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“…Ellis [18] experimentally and analytically studied the induced vorticity in a centrifugal compressor. Krain [19], Moore and Moore [20], Eckardt [1], Howard and Lennemann [21], and Brun et al [12] experimentally determined the secondary flows in mixed-flow centrifugal impellers. Finally, Johnson and Moore [22] determined secondary flow mixing losses in a centrifugal impeller from pressure probes installed in the rotating impeller.…”

Section: Background and Review Of Relevant Literaturementioning

confidence: 99%

Analysis of Secondary Flows in Centrifugal Impellers

Brun

Kurz²

2005

International Journal of Rotating Machinery

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Secondary flows are undesirable in centrifugal compressors as they are a direct cause for flow (head) losses, create nonuniform meridional flow profiles, potentially induce flow separation/stall, and contribute to impeller flow slip; that is, secondary flows negatively affect the compressor performance. A model based on the vorticity equation for a rotating system was developed to determine the streamwise vorticity from the normal and binormal vorticity components (which are known from the meridional flow profile). Using the streamwise vorticity results and the small shear-large disturbance flow method, the onset, direction, and magnitude of circulatory secondary flows in a shrouded centrifugal impeller can be predicted. This model is also used to estimate head losses due to secondary flows in a centrifugal flow impeller. The described method can be employed early in the design process to develop impeller flow shapes that intrinsically reduce secondary flows rather than using disruptive elements such as splitter vanes to accomplish this task.

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“…This served to make possible various flow visualization and special velocity measurement methods. In the past, both locally traversed hot-film probes and laser-Doppler velocimetry has been used to measure velocities in the impeller passage (Howard and Lennemann (1971), Howard eta!. (1980)), and the volute ).…”

Section: Experimental Apparatus Test Rigmentioning

confidence: 99%

A Rotating Laser-Doppler Anemometry System for Unsteady Relative Flow Measurements in Model Centrifugal Impellers

Abramian¹,

Howard

1993

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery

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The behaviour of the relative flow in centrifugal turbomachines is extremely complex due to the existence of various fluid dynamic phenomena and their interaction. At design and off-design operating conditions, the relative flow is subject to stationary unsteadiness which includes the flow separation and wakes associated with passage pressure gradients, secondary flows, and boundary layer stability. It is also subject to periodic unsteadiness from the rotating stall and the cyclic flow phenomena induced by the casing. This paper describes the mechanical and optical design of a rotating laser-Doppler anemometry system which allows direct measurement of the relative flow by means of an optical de-rotator. By isolating the impeller rotational frequency from the sampling frequency, it allows direct time-average measurements of the stationary behaviour of the relative flow along with the ensemble (phase)-average measurements of its periodic behaviour. Its success is demonstrated with measurements conducted in a low specific speed centrifugal impeller fitted with a single volute. Sample results of the time-averaged blade-to-blade variation of total relative velocities along with their associated turbulence intensities are reported. The (periodic) cyclic variations of the impeller exit flow, induced by the volute at low flow rates, are also presented for the suction and pressure sides.

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Measured and Predicted Secondary Flows in a Centrifugal Impeller

Cited by 8 publications

References 0 publications

Experimental Investigation of the Steady and Unsteady Relative Flow in a Model Centrifugal Impeller Passage

Experimental Investigation of the Steady and Unsteady Relative Flow in a Model Centrifugal Impeller Passage

Analysis of Secondary Flows in Centrifugal Impellers

A Rotating Laser-Doppler Anemometry System for Unsteady Relative Flow Measurements in Model Centrifugal Impellers

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