Film Cooling Effectiveness and Heat Transfer Coefficients for Slot Injection at High Blowing Ratios

Bittlinger, G.; Schulz, Achmed; Wittig, Sigmar

doi:10.1115/94-gt-182

Cited by 19 publications

(5 citation statements)

References 16 publications

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“…Taslim et al (1992) investigated the effect of parameters like density ratio, lip thickness to ejection slot height ratio (t/s), slot width to height ratio (w/s) and injection angle on the adiabatic effectiveness distribution downstream of a simplified trailing edge model in a non accelerating flow. Bittlinger et al (1994) studied the injection through a slot at high blowing conditions on a similar model varying both the lip thickness and the slot height. Martini et al (2005a) measured g downstream of a cutback trailing edge model (t/s = 1.0), for three internal cooling configurations, at low and constant mainstream velocity.…”

Section: Cutback Trailing Edge Studiesmentioning

confidence: 99%

Experimental investigation of the effects of blowing conditions and Mach number on the unsteady behavior of coolant ejection through a trailing edge cutback

Barigozzi¹,

Armellini²,

Mucignat³

et al. 2012

International Journal of Heat and Fluid Flow

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Section: Cutback Trailing Edge Studiesmentioning

confidence: 99%

Experimental investigation of the effects of blowing conditions and Mach number on the unsteady behavior of coolant ejection through a trailing edge cutback

Barigozzi¹,

Armellini²,

Mucignat³

et al. 2012

International Journal of Heat and Fluid Flow

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“…When heat transfer coefficients are required, the surface temperature and the heat flux must be measured. Thermocouples or resistance thermometers positioned at specific positions along the surface are commonly used for temperature measurements [5,6]. However, the ready accessibility of easy-to-use thermography caused a paradigm shift for surface temperature measurements.…”

Section: State Of the Artmentioning

confidence: 99%

“…For heat flux measurements different steady and transient techniques exist. Steady heat flux measurements either calculate the heat flux through a material of known thermal conductivity by measuring the temperatures on both sides [6,11,12], or record the local heat flux with the help of heat flux sensors, e.g., thin-film heaters [9,10,13]. Carlomagno [18] reviewed different types of heat flux sensors and concluded that thin-film heaters are precise and effective devices.…”

Section: State Of the Artmentioning

confidence: 99%

Heat transfer and film cooling measurements on aerodynamic geometries relevant for turbomachinery

et al. 2021

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A measurement technique for recording convective heat transfer coefficient and adiabatic film cooling effectiveness in demanding environments with highly curved surfaces and limited optical access, such as turbomachinery, is presented. Thermography and tailor-made flexible heating foils are used in conjunction with a novel multistep calibration and data reduction method. This method compensates for sensor drift, angle dependence of surface emissivity and window transmissivity, heat flux inhomogeneity, and conductive losses. The 2D infrared images are mapped onto the 3D curved surfaces and overlapped, creating surface maps of heat transfer coefficient and film cooling effectiveness covering areas significantly larger than the window size. The measurement technique’s capability is demonstrated in a sector-cascade test rig of a turbine center frame (TCF), an inherent component of modern two-spool turbofan engines. The horseshoe vortices were found to play a major role for the thermal integrity of turbine center frames, as they lead to a local increase in heat transfer, and at the same instance, to a reduction of film cooling effectiveness. It was also found that the horseshoe vortices lift off from the curved surface at 50% hub length, resulting in a pair of counter-rotating vortices. The measurement technique was validated by comparing the data against flat plate correlations and also by the linear relation between temperature difference and heat flux. This study is complemented with an extensive error and uncertainty analysis. Article highlights This paper presents an accurate measurement technique for heat transfer and film cooling on 3D curved surfaces with limited optical access using flexible tailor-made heating foils, infrared thermography and a high-fidelity multistep calibration process. Graphical abstract

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“…One of the recent studies in tangential slot jet film cooling was done by Bittlinger, Schulz, and Wittig (1994). With a density ratio of unity, they conducted heat transfer coefficient experiments over a range of blowing ratios (0.55<M<3.2).…”

Section: Introductionmentioning

confidence: 99%

Jet Mixing in a Slot

Wang

Chintalapati

Bunker

et al. 1998

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration

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Jet mixing inside a slot has the potential to be applied for cooling in various components in gas turbines. Based on the premise that more uniform flow at the exit of the slot would achieve more uniform cooling downstream of the slot, an experimental program was conducted to focus on investigating the flow mixing behavior inside the slots. Various parameters including orientation angle, inclination angle, slot width, effect of primary flow and slot depth were systematically examined. An array of seven jets with a jet-to-jet spacing of five diameters and velocity ratio of unity was used in the experiment. Experiments were performed by changing the orientation angles of the jets with two inclination angles (90° and 30°). The results indicated that the flow distribution at the slot exit becomes more uniform as the orientation angle was increased from 0° to 60°. Wider slot width brought about high non-uniformity and was clearly undesirable. The optimum slot depth was found to range from 2 to 2.8 times the jet diameter for slots perpendicular to the primary flow (i.e. with 90° inclination angle). The flow field was the most uniform where the shear layers of the two adjacent jets met. Regions of low velocity and high pressure caused non-uniform velocity distribution downstream where the jets met, so deeper slots do not necessarily render better uniformity. When the orientation angle increased from 0 to 30° and 60°, the jets bent toward the wall in the inclined direction caused by the Coanda effect. The presence of the primary flow forced the jet to spread faster in the lateral direction and caused some nonuniform flow pockets at the slot exit. The compound angle configuration (60° jet orientation and 30° slot inclination angles) was discovered as the best choice with four merits: (i) The acceptable uniform flow can be reached as shallow as h/d = 1.0 (slot depth over jet diameter), (ii) The range of the acceptable uniform flow was the broadest (form y/d = 1.0 to y/d = 2.8). (iii) Flow uniformity was the best at the exit, (iv) The total pressure loss was the lowest.

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Film Cooling Effectiveness and Heat Transfer Coefficients for Slot Injection at High Blowing Ratios

Cited by 19 publications

References 16 publications

Experimental investigation of the effects of blowing conditions and Mach number on the unsteady behavior of coolant ejection through a trailing edge cutback

Experimental investigation of the effects of blowing conditions and Mach number on the unsteady behavior of coolant ejection through a trailing edge cutback

Heat transfer and film cooling measurements on aerodynamic geometries relevant for turbomachinery

Jet Mixing in a Slot

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