Engine Representative Discharge Coefficients Measured in an Annular Nozzle Guide Vane Cascade

Rowbury, D. A.; Oldfield, M. L. G.; Lock, Gary

doi:10.1115/97-gt-099

Cited by 10 publications

(6 citation statements)

References 7 publications

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“…Moreover, the discharge coefficient obtained with cross flow exceeds that of the freejet (U C F = 0) for several operating conditions. Such flow behavior has been observed in [2] as well as in turbine film cooling holes [7]. For the latter case, a detailed study of the phenomenon [26] led to the conclusion that the enhanced discharge coefficient comes from the combination of a locally reduced static pressure at the hole outlet and the jet entrainment by the freestream.…”

Section: Cross Flow Effects On Pressure Lossmentioning

confidence: 55%

“…As evidenced by a recent review on JICF [5], literature on this configuration is abundant but mostly focused on the flow field downstream of the jet exit and data on pressure loss are not reported. When such data are made available, the target application is generally dedicated to the cooling of hot stages of aeronautical engines [6][7][8][9] for which the configurations are too far from the present problem to extrapolate the conclusions directly. Regarding studies on orifice plates placed in a duct, there is a greater body of work relevant to the present study.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Discharge coefficient of an orifice jet in cross flow: influence of inlet conditions and optimum velocity ratio

Berger¹,

Gourdain²,

Bauerheim³

et al. 2019

AIAA Aviation 2019 Forum

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Section: Cross Flow Effects On Pressure Lossmentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Discharge coefficient of an orifice jet in cross flow: influence of inlet conditions and optimum velocity ratio

Berger¹,

Gourdain²,

Bauerheim³

et al. 2019

AIAA Aviation 2019 Forum

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“…In real systems the effective area is a function of ⁄ and the coolant Reynolds number Re " (e.g. [3]). We write = , , , Re " .…”

Section: Capacity Theorymentioning

confidence: 99%

“…Exhausting to atmosphere typically reduces coolant Re by a factor of 4.5 compared the engine. The impact is a coolant capacity (estimated from [3]) approximately 6% lower than in the engine. This can be accounted for with a correction factor, a method which is believed to be robust since the Re mismatch affects all rows similarly (see [3]).…”

Section: Scaling Between Rig and Engine Conditionsmentioning

confidence: 99%

“…The impact is a coolant capacity (estimated from [3]) approximately 6% lower than in the engine. This can be accounted for with a correction factor, a method which is believed to be robust since the Re mismatch affects all rows similarly (see [3]). Scaling to engine conditions is not the prime topic of this paper, but the correction factor method is believed by the authors to be adequate, and is mentioned here for completeness.…”

Section: Scaling Between Rig and Engine Conditionsmentioning

confidence: 99%

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Method for Accurately Evaluating Flow Capacity of Individual Film-Cooling Rows of Engine Components

Kirollos

Povey

2017

Journal of Turbomachinery

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A laboratory experimental method and an analysis technique are presented for evaluation of individual film-cooling row flow capacity characteristics. The method is particularly suited to complex systems such as hot section nozzle guide vanes (NGV) with lossy feed system characteristics. The method is believed to be both more accurate and more experimentally efficient than previous techniques. The new analysis technique uses an experimentally calibrated network model to represent the complex feed system and replaces the need for internal loss measurements, which are both demanding and inaccurate. Experiments are performed in the purpose-built University of Oxford Coolant Capacity Rig (CCR), a bench-top, blow-down type facility with atmospheric back-pressure. The design of the CCR is informed by the requirements to assess engine-scale film-cooled components rapidly, accurately, and precisely. Improvements in the experimental method include a differential mass flow rate measurement method (which eliminates the effect of leaks and minimizes the number of rows that must be blanked, ensuring that the internal coupling is as close as possible to the engine condition) and a variable bypass flow which ensures the mass flow measurement nozzle always operates within its calibrated range. We demonstrate the method using two high-pressure (HP) NGV designs: an engine part with relatively uncoupled (in terms of internal loss) cooling rows; and a laser-sintered part with highly coupled cooling rows. We show that the individual-row flow capacity of a high-pressure nozzle guide vane (HPNGV) can be evaluated in the CCR in a single day to a 2σ precision of approximately 0.5% and a 2σ accuracy (bias) of 0.6%. The importance of performing individual-row capacity measurements is demonstrated: failure to scale flow capacity on a row-by-row basis introduces an error of 30% in the engine situation.

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A Method for Correlating the Influence of External Crossflow on the Discharge Coefficients of Film Cooling Holes

Rowbury

Oldfield

Lock

2000

Journal of Turbomachinery

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An empirical means of predicting the discharge coefficients of film cooling holes in an operating engine has been developed. The method quantifies the influence of the major dimensionless parameters, namely hole geometry, pressure ratio across the hole, coolant Reynolds number, and the freestream Mach number. The method utilizes discharge coefficient data measured on both a first-stage high-pressure nozzle guide vane from a modern aero-engine and a scale (1.4 times) replica of the vane. The vane has over 300 film cooling holes, arranged in 14 rows. Data was collected for both vanes in the absence of external flow. These noncrossflow experiments were conducted in a pressurized vessel in order to cover the wide range of pressure ratios and coolant Reynolds numbers found in the engine. Regrettably, the proprietary nature of the data collected on the engine vane prevents its publication, although its input to the derived correlation is discussed. Experiments were also conducted using the replica vanes in an annular blowdown cascade which models the external flow patterns found in the engine. The coolant system used a heavy foreign gas (SF6 /Ar mixture) at ambient temperatures which allowed the coolant-to-mainstream density ratio and blowing parameters to be matched to engine values. These experiments matched the mainstream Reynolds and Mach numbers and the coolant Mach number to engine values, but the coolant Reynolds number was not engine representative (Rowbury, D. A., Oldfield, M. L. G., and Lock, G. D., 1997, “Engine-Representative Discharge Coefficients Measured in an Annular Nozzle Guide Vane Cascade,” ASME Paper No. 97-GT-99, International Gas Turbine and Aero-Engine Congress & Exhibition, Orlando, Florida, June 1997; Rowbury, D. A., Oldfield, M. L. G., Lock, G. D., and Dancer, S. N., 1998, “Scaling of Film Cooling Discharge Coefficient Measurements to Engine Conditions,” ASME Paper No. 98-GT-79, International Gas Turbine and Aero-Engine Congress & Exhibition, Stockholm, Sweden, June 1998). A correlation for discharge coefficients in the absence of external crossflow has been derived from this data and other published data. An additive loss coefficient method is subsequently applied to the cascade data in order to assess the effect of the external crossflow. The correlation is used successfully to reconstruct the experimental data. It is further validated by successfully predicting data published by other researchers. The work presented is of considerable value to gas turbine design engineers as it provides an improved means of predicting the discharge coefficients of engine film cooling holes.

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Engine Representative Discharge Coefficients Measured in an Annular Nozzle Guide Vane Cascade

Cited by 10 publications

References 7 publications

Discharge coefficient of an orifice jet in cross flow: influence of inlet conditions and optimum velocity ratio

Discharge coefficient of an orifice jet in cross flow: influence of inlet conditions and optimum velocity ratio

Method for Accurately Evaluating Flow Capacity of Individual Film-Cooling Rows of Engine Components

A Method for Correlating the Influence of External Crossflow on the Discharge Coefficients of Film Cooling Holes

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