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Research Papers: Jets, Wakes, and Impingment Cooling

Influence of Coolant Jet Pulsation on the Convective Film Cooling of an Adiabatic Wall

[+] Author and Article Information
Qaiser Sultan

Département Fluides, Thermique et Combustion,
Institut P'—CNRS—ISAE-ENSMA—Université
de Poitiers,
Axe Cost Téléport 2-1, Av Clément
86961 Futuroscope Chasseneuil Cedex, France
e-mail: qaiser.sultan@gmail.com

Gildas Lalizel

Département Fluides, Thermique et Combustion,
Institut P'—CNRS—ISAE-ENSMA—Université
de Poitiers,
Axe Cost Téléport 2-1, Av Clément
86961 Futuroscope Chasseneuil Cedex, France
e-mail: gildas.lalizel@isae-ensma.fr

Matthieu Fénot

Département Fluides, Thermique et Combustion,
Institut P'—CNRS—ISAE-ENSMA—Université
de Poitiers,
Axe Cost Téléport 2-1, Av Clément
86961 Futuroscope Chasseneuil Cedex, France
e-mail: matthieu.fénot@isae-ensma.fr

Eva Dorignac

Département Fluides, Thermique et Combustion,
Institut P'—CNRS—ISAE-ENSMA—Université
de Poitiers,
Axe Cost Téléport 2-1, Av Clément
86961 Futuroscope Chasseneuil Cedex, France
e-mail: eva.dorignac@isae-ensma.fr

1Corresponding author.

2Present address: House # F-2, Alfalah Housing Society, Malir Halt, Karachi 75210, Pakistan.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received April 22, 2016; final manuscript received August 31, 2016; published online October 26, 2016. Assoc. Editor: Zhixiong Guo.

J. Heat Transfer 139(2), 022201 (Oct 26, 2016) (12 pages) Paper No: HT-16-1223; doi: 10.1115/1.4034773 History: Received April 22, 2016; Revised August 31, 2016

Abstract

This study investigates the effects of sinusoidal pulsations externally imposed to an oblique round jet. The effectiveness of film coverage of an adiabatic wall onset for a thermally uniform bulk flow is presented in the perspective of gas turbine film cooling. For the injectant fluid, both the temperature and the mass flow rate are controlled prior to entrance to the periodic forcing system using a loudspeaker drive. The characteristic film cooling parameters including the blowing ratios and the temperature ratio are maintained at $M=ρiUi/ρ∞U∞$= 0.65, 1, and 1.25, and $Ti/T∞=2$ respectively. The injection fluid is pulsated to a nondimensionalized frequency of $St=f⋅d/U$= 0, 0.2, 0.3, and 0.5. In the present investigation, the impact of injectant film modulation is figured out by analyzing the velocity fields measured by a system of time-resolved particle image velocimetry (TR-PIV), as well as analyzing the adiabatic wall temperature and the convective heat transfer coefficient measured by a system of infrared thermography. The overall film-cooling effectiveness is revealed by the time-averaged analysis, in which altered time-averaged jet trajectories and wake behavior are focused. It is observed that the pulsations tend to result in lower effectiveness when the flow remained attached to the wall in steady blowing case. In steady blowing cases with jet liftoff, such as for $M=$ 1.25, rendering low-frequency pulsation helps in increasing film-cooling effectiveness due to the discharge of lower mass flow rate coolant during the significant time interval of the respective pulse cycle.

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Figures

Fig. 1

(a) Schematic diagram of injection flow system, R(0-1): pressure regulator, T0: temperature probe PT100, T(1-2) thermocouple type-K, (b) experimental arrangement for infrared thermography

Fig. 2

Heat transfer model, using a linear fit for four points

Fig. 3

Comparison of time-averaged profiles of U/U∞, lying at x/d = 3.5 and 5.5 of the hole central plane (z/d = 0), for different St (0, 0.2 0.3 and 0.5) examined under a range of M (0.65, 1 and 1.25), while M increasing columnwise and x/d increasing rowwise

Fig. 4

Steady blowing results for adiabatic effectiveness: (a) M= 0.65, (b) M= 1, (c) M= 1.25 and convective heat transfer coefficient: (d) M= 0.65, (e) M= 1, and (f) M= 1.25

Fig. 5

Film cooling at Ti/T∞=2, centerline effectiveness: (a) M= 0.65, (b) M= 1, (c) M= 1.25, and laterally averaged effectiveness: (d) M= 0.65, (e) M= 1, and (f) M= 1.25

Fig. 6

Film cooling at Ti/T∞=2, centerline heat transfer coefficient (a) M= 0.65, (b) M= 1, (c) M= 1.25, and laterally averaged heat transfer coefficient (d) M= 0.65, (e) M= 1, and (f) M= 1.25

Fig. 7

Comparison of film cooling parameters blowing at Ti/T∞=2, (a) centerline adiabatic effectiveness and (b) centerline Stanton number ratio

Fig. 8

Comparison of the laterally averaged heat transfer coefficient in the immediate downstream region

Fig. 9

Wall zone for estimating spatially averaged results

Fig. 10

Comparison of different cases of pulsation, Ti/T∞=2, (a) spatially averaged effectiveness and (b) spatially averaged heat transfer coefficient

Fig. 11

Film cooling at Ti/T∞=2, centerline NHFR (a) M= 0.65, (b) M= 1, (c) M= 1.25, and laterally averaged NHFR (d) M=0.65, (e) M= 1, and (f) M= 1.25

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