Theory for the use of foreign gas in simulating film cooling

Jones, T. V.

doi:10.1016/s0142-727x(99)00017-x

Cited by 79 publications

(21 citation statements)

References 11 publications

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“…Through the exploitation of the luminescence behaviour of these molecules, PSP can be used to measure the oxygen concentration of the atmosphere surrounding the paints, which in turn can be linked to the partial pressure of air. This property makes the paint suitable for gas concentration technique based on the heat and mass transfer analogy [72], e.g. for adiabatic effectiveness measurements.…”

Section: Adiabatic Effectiveness Measurementsmentioning

confidence: 99%

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Film Cooling Modelling for Gas Turbine Nozzles and Blades: Validation and Application

Andrei

Innocenti

Andreini

et al. 2015

Volume 5B: Heat Transfer

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The use of Computational Fluid Dynamics (CFD) for modern turbine blade design requires the accurate representation of the effect of film cooling. However, including complete cooling hole discretization in the computational domain requires a substantial meshing effort and leads to a drastic increase in the computing time. For this reason, many efforts have been made to develop lower order approaches aiming at reducing the number of mesh elements and therefore computational resources. The simplest approach models the set of holes as a uniform coolant injection, but it does not allow an accurate assessment of the interaction between hot gas and coolant. Therefore higher order models have been developed, such as those based on localized mass sources in the region of hole discharge. It is here proposed an innovative injection film cooling model (FCM), embedded in a CFD code, to represent the effect of cooling holes by adding local source terms at the hole exit in a delimited portion of the domain, avoiding the meshing process of perforations. The goal is to provide a reliable and accurate tool to simulate film-cooled turbine blades and nozzles without having to explicitly mesh the holes. The validation campaign of the proposed model is composed of two phases. During the first one, results obtained with the film cooling model are compared to experimental data and to numerical results obtained with the full meshing of the cooling holes on a series of test cases, ranging from single row to multi row flat plate, at varying coolant conditions (in terms of blowing and density ratio). Though details of the flow structure downstream of the holes cannot be perfectly captured, this method allows an accurate prediction of the overall flow and performance modifications induced by the presence of the cooling holes, with a strong agreement to complete hole discretization results. In the second phase, a complete film-cooled vane test case has been studied, in order to consider a real injection system and flow conditions. In this case, film cooling model predictions are compared to an in-house developed correlative approach and full CHT 3D-CFD results. Finally, a comparison between film cooling model predictions and experimental data was performed on an actual nozzle of a GE Oil & Gas heavy-duty gas turbine as well, in order to prove the feasibility of the procedure. The presented film cooling model proved to be a feasible and reliable tool to evaluate adiabatic effectiveness, simplifying the design phase avoiding the meshing process of perforations. Also, refining the mesh near the hole exit, FCM results well approximate the solution coming from a full CHT calculation.

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Section: Adiabatic Effectiveness Measurementsmentioning

confidence: 99%

“…Assuming valid the analogy, if a tracer gas without free oxygen (e.g. N2 or CO2) is used as coolant in the vane cooling system it is straightforward to replace the temperature definition of film cooling effectiveness by mass fractions of oxygen [72], and hence in terms of O2 partial pressure measured with PSP [74]:…”

Section: Adiabatic Effectiveness Measurementsmentioning

confidence: 99%

Film Cooling Modelling for Gas Turbine Nozzles and Blades: Validation and Application

Andrei

Innocenti

Andreini

et al. 2015

Volume 5B: Heat Transfer

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“…Using the heat and mass transfer analogy, based on works by Jones [6], the filmcooling effectiveness can be expressed as a ratio of oxygen concentrations measured by PSP and is calculated using the following equation [7]: 1 (1)…”

Section: Film-cooling Effectiveness Calculationmentioning

confidence: 99%

Influence of Coolant Density on Turbine Blade Film-Cooling With Axial and Compound Shaped Holes

Liu

Yang

Han

2014

Journal of Heat Transfer

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Adiabatic film-cooling effectiveness is examined systematically on a typical high pressure turbine blade by varying three critical flow parameters: coolant blowing ratio, coolant-to-mainstream density ratio, and freestream turbulence intensity. Three coolant density ratios 1.0,1.5, and 2.0 are chosen for this study. The average blowing ration and the turbulence intensity are 1.5% and 10.5%, respectively. Conduction-free pressure sensitive paint (PSP) technique is used to measure film-cooling effectiveness. Foreign gases are used to study the effect of coolant density. Two test blades feature axial angle and 45 deg compound-angle shaped holes on the suction side and pressure side. Both designs have 3 rows of 30 deg radial-angle cylindrical holes around the leading edge region. The inlet and the exit Mach number are 0.27 and 0.44, respectively. Reynolds number based on the exit velocity and blade axial chord length is 750,000. Overall, the compound angle design performs better film coverage that axial angle. Greater coolant-to-mainstream density ratio results in lower coolant-to-mainstream momentum and prevents coolant to lift-off.

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“…Based on the work of Jones (1999) and Kays et al (2005), the stipulation Le T ≈ 1 holds for turbulent gaseous flow fields, such as those encountered in gas turbine engines. And therefore:…”

Section: Mass Transfer Analogy For Film Cooling Effectivenessmentioning

confidence: 99%

Turbine Blade Film Cooling Using PSP Technique

Han¹,

Rallabandi²

2010

Frontiers in Heat and Mass Transfer

191

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Film cooling is widely used to protect modern gas turbine blades and vanes from the ever increasing inlet temperatures. Film cooling involves a very complex turbulent flow-field, the characterization of which is necessary for reliable and economical design. Several experimental studies have focused on gas turbine blade, vane and end-wall film cooling over the past few decades. Measurements of heat transfer coefficients, film cooling effectiveness values and heat flux ratios using several different experimental methods have been reported. The emphasis of this current review is on the Pressure Sensitive Paint (PSP) mass transfer analogy to determine the film cooling effectiveness. The theoretical basis of the method is presented in detail. Important results in the open literature obtained using the PSP method are presented, discussing parametric effects of blowing ratio, momentum ratio, density ratio, hole shape, surface geometry, free-stream turbulence on flat plates, turbine blades, vanes and end-walls. The PSP method provides very high resolution contours of film cooling effectiveness, without being subject to the conduction error in high thermal gradient regions near the hole.

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Theory for the use of foreign gas in simulating film cooling

Cited by 79 publications

References 11 publications

Film Cooling Modelling for Gas Turbine Nozzles and Blades: Validation and Application

Film Cooling Modelling for Gas Turbine Nozzles and Blades: Validation and Application

Influence of Coolant Density on Turbine Blade Film-Cooling With Axial and Compound Shaped Holes

Turbine Blade Film Cooling Using PSP Technique

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