Model Verification of Mist/Steam Cooling With Jet Impingement Onto a Concave Surface and Prediction at Elevated Operating Conditions

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Ting Wang ◽  
T. S. Dhanasekaran
Keyword(s):  
Jet Impingement ◽  
Elevated Pressure ◽  
Operating Conditions ◽  
Model Verification ◽  
Concave Surface ◽  
Cfd Model ◽  
Cooling Performance ◽  
Cooling Enhancement ◽  
Mist Cooling ◽  
Steam Cooling

Internal mist/steam blade cooling technology is proposed for advanced gas turbine systems that use the closed-loop steam cooling scheme. Previous experiments on mist/steam heat transfer with a 2D slot jet impingement onto a concave surface showed cooling enhancement of up to 200% at the stagnation point by injecting approximately 0.5% of mist under low temperature and pressure laboratory conditions. Realizing the difficulty in conducting experiments at elevated pressure and temperature working conditions, computational fluid dynamics (CFD) simulation becomes an opted approach to predict the potential applicability of the mist/steam cooling technique at real GT operating conditions. In this study, the CFD model is first validated within 3% and 6% deviations from experimental results for the flows of steam-only and mist/steam flow cases, respectively. The validated CFD model is then used to simulate a row of multiple holes impinging jet onto a concave surface under elevated pressure, temperature, and Reynolds number conditions. The predicted results show an off-center cooling enhancement with a local maximum of 100% at s/d=2 and an average cooling enhancement of about 50%. The mist cooling scheme is predicted to work better on a concave surface than on the flat surface. The extent of wall jet and the size of 3D recirculation zones are identified as a major influencing parameter on the curvature effect on mist cooling performance. The mist enhancement from a slot jet is more pronounced than a row of round jets. The effects of wall heat flux and mist ratio on mist cooling performance are also investigated in this study.

Model Verification of Mist/Steam Cooling With Jet Impingement Onto a Concave Surface and Prediction at Elevated Operating Condition

2010 ◽  
Author(s):  
Ting Wang ◽  
T. S. Dhanasekaran
Keyword(s):  
Jet Impingement ◽  
Elevated Pressure ◽  
Operating Conditions ◽  
Model Verification ◽  
Concave Surface ◽  
Cfd Model ◽  
Cooling Performance ◽  
Cooling Enhancement ◽  
Mist Cooling ◽  
Steam Cooling

Internal mist/steam blade cooling technology is proposed for advanced gas turbine systems that use the closed-loop steam cooling scheme. Previous experiments on mist/steam heat transfer with a 2-D slot jet impingement onto a concave surface showed cooling enhancement of up to 200% at the stagnation point by injecting approximately 0.5% of mist under low temperature and pressure laboratory conditions. Realizing the difficultly in conducting experiments at elevated pressure and temperature working conditions, CFD simulation becomes an opted approach to predict the potential applicability of the mist/steam cooling technique at real GT operating conditions. In this study, the CFD model is first validated within 3% and 6% deviation from experimental results for the flows of steam only and mist/steam flow cases, respectively. The validated CFD model is then used to simulate a row of multiple holes impinging jet onto a concave surface under elevated pressure, temperature, and Reynolds number condition. The predicted results show an off-center cooling enhancement with a local maximum of 200% at s/d = 2 and an average cooling enhancement of about 150%. The mist cooling scheme is predicted to work better on a concave surface than on the flat surface. The extent of wall jet and the size of 3-D recirculation zones are identified as a major influencing parameter on the curvature effect on mist cooling performance. The mist enhancement from a slot jet is more pronounced than a row of round jets. The effects of wall heat flux and mist ratio on mist cooling performance are also investigated in this study.

Calibration of a Computational Model to Predict Mist/Steam Impinging Jets Cooling With an Application to Gas Turbine Blades

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Ting Wang ◽  
T. S. Dhanasekaran
Keyword(s):  
Gas Turbine ◽  
Working Condition ◽  
Turbulence Models ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Operating Conditions ◽  
Experimental Results ◽  
Cfd Model ◽  
Cooling Enhancement ◽  
Mist Cooling

In heavy-frame advanced turbine systems, steam is used as a coolant for turbine blade cooling. The concept of injecting mist into the impinging jets of steam was experimentally proved as an effective way of significantly enhancing the cooling effectiveness in the laboratory under low pressure and temperature conditions. However, whether or not mist/steam cooling is applicable under actual gas turbine operating conditions is still subject to further verification. Recognizing the difficulties of conducting experiments in an actual high-pressure, high-temperature working gas turbine, a simulation using a computational fluid dynamic (CFD) model calibrated with laboratory data would be an opted approach. To this end, the present study conducts a CFD model calibration against the database of two experimental cases including a slot impinging jet and three rows of staggered impinging jets. The calibrated CFD model was then used to predict the mist cooling enhancement at the elevated gas turbine working condition. Using the experimental results, the CFD model has been tuned by employing different turbulence models, computational cells, and wall y+ values. In addition, the effects of different forces (e.g., drag, thermophoretic, Brownian, and Saffman’s lift force) are also studied. None of the models is a good predictor for all the flow regions from near the stagnation region to far-field downstream of the jets. Overall speaking, both standard k-ε and Reynolds stress model (RSM) turbulence models perform better than other models. The RSM model has produced the closest results to the experimental data due to its capability of modeling the nonisotropic turbulence shear stresses in the 3D impinging jet fields. The simulated results show that the calibrated CFD model can predict the heat transfer coefficient of steam-only case within 2–5% deviations from the experimental results for all the cases. When mist is employed, the prediction of wall temperatures is within 5% for a slot jet and within 10% for three-row jets. The predicted results with 1.5% mist at the gas turbine working condition show the mist cooling enhancement of 20%, whereas in the laboratory condition, the enhancement is predicted as 80%. Increasing mist ratio to 5% increased the cooling enhancement to about 100% at the gas turbine working condition.

scholarly journals CFD Model Validation and Prediction of Mist/Steam Cooling in a 180-Degree Bend Tubes

2010 ◽  
Author(s):  
T. S. Dhanasekaran ◽  
Ting Wang
Keyword(s):  
Boundary Condition ◽  
Gas Turbine ◽  
Working Conditions ◽  
Working Condition ◽  
Cfd Simulation ◽  
Experimental Results ◽  
Cfd Model ◽  
Cooling Enhancement ◽  
Mist Cooling ◽  
Steam Cooling

To achieve higher efficiency target of the advanced turbine systems, the closed-loop steam cooling scheme is employed to cool the airfoil. It is proven from the experimental results at laboratory working conditions that injecting mist into steam can significantly augment the heat transfer in the turbine blades with several fundamental studies. The mist cooling technique has to be tested at gas turbine working conditions before implementation. Realizing the fact that conducting experiment at gas turbine working condition would be expensive and time consuming, the computational simulation is performed to get a preliminary evaluation on the potential success of mist cooling at gas turbine working conditions. The present investigation aims at validating a CFD model against experimental results in a 180-degree tube bend and applying the model to predict the mist/steam cooling performance at gas turbine working conditions. The results show that the CFD model can predict the wall temperature within 8% of experimental steam-only flow and 16% of mist/steam flow condition. Five turbulence models have been employed and their results are compared. Inclusion of radiation into CFD model causes noticeable increase in accuracy of prediction. The reflect Discrete Phase Model (DPM) wall boundary condition predicts better than the wall-film boundary condition. The CFD simulation identifies that mist impingement over outer wall is the cause for maximum mist cooling enhancement at 45° of bend portion. The computed results also reveals the phenomenon of mist secondary flow interaction at bend portion, adding the mist cooling enhancement at the inner wall. The validated CFD simulation predicts that average of 100% mist cooling enhancement can be achieved by injecting 5% mist at elevated GT working condition.

Conjugate heat transfer simulation of turbine blade high efficiency cooling method with mist injection

2014 ◽  
Vol 228 (15) ◽  
pp. 2738-2749 ◽  
Author(s):  
Yuting Jiang ◽  
Qun Zheng ◽  
Guoqiang Yue ◽  
Ping Dong ◽  
Jie Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Conjugate Heat Transfer ◽  
High Efficiency ◽  
Turbulence Models ◽  
Operating Conditions ◽  
Cooling Performance ◽  
Convective Cooling ◽  
Mist Cooling ◽  
The Impact

The idea of utilizing a finely dispersed water-in-air mixture has been proven to be a feasible technique to produce very high cooling rates. The accuracy of numerical simulation program for conjugate heat transfer methodology is verified with the Mark II transonic high pressure turbine stator which is cooled by internal convection through radial round pipes, and different turbulence models and transition models are employed to analyze the influence on results. On the basis of it, the mist cooling is simulated under typical gas turbine operating conditions for internal convective cooling to discuss the improvement of cooling performance. Though the results indicate that mist cooling can decrease the temperature of boundary layer without impact on the temperature of the mainstream and the thickness of boundary layer, the cooling capacity is limited by inadequate evaporation of mist. Considering the distribution of thermal stress and mist evaporation, a compound cooling blade of film cooling with trailing edge ejection is acquired which is modified from the blade of Mark II internal convective cooling; the effects of various parameters including mist concentration and mist diameter on the improvement of cooling performance are investigated, meanwhile the impact of curvature on cooling efficiency and mist trajectory is analyzed finally.

Validation of Mist/Steam Cooling CFD Model in a Horizontal Tube

2008 ◽  
Author(s):  
T. S. Dhanasekaran ◽  
Ting Wang
Keyword(s):  
Gas Turbine ◽  
Droplet Diameter ◽  
Turbulence Models ◽  
Horizontal Tube ◽  
Working Environment ◽  
Cfd Model ◽  
Wall Film ◽  
Cooling Enhancement ◽  
Steam Cooling ◽  
Uniform Droplets

Mist cooling concept has been considered for cooling turbine airfoils for many years. This concept has been proven experimentally as an effective method to significantly enhance the cooling effectiveness with several fundamental studies in the laboratory under low pressure and temperature conditions. However, it is not certain the same performance can be harnessed in the real gas turbine environment under the condition of elevated temperature, pressure, heat flux, and Reynolds number. This paper aims at validating a CFD model against experimental results in a circular tube and then applies the validated CFD model to simulate mist/steam cooling performance at elevated gas turbine working conditions. The results show that the standard k-ε and a RSM turbulence models are the best-suited model for this application. The mist with smaller droplet diameter is found achieving higher cooling enhancement than the flows with bigger droplets, while mist with a distributed droplet size matches the data slightest better than with uniform droplets. Both the wall-film and the reflect droplet boundary conditions are employed and their effects on the cooling result is not significant at the studied cases. The validated CFD model can predict the wall temperature within 2% in steam-only flow and 5% in the mist/steam flow. Applying the calibrated CFD model to the actual gas turbine working environment shows that the mist/steam cooling technique could harness an average 50–100% cooling enhancement.

Mist/Steam Heat Transfer With Jet Impingement Onto a Concave Surface

2003 ◽  
Vol 125 (3) ◽  
pp. 438-446 ◽  
Author(s):  
Xianchang Li ◽  
J. Leo Gaddis ◽  
Ting Wang
Keyword(s):  
Stagnation Point ◽  
Heated Surface ◽  
Leading Edge ◽  
Jet Impingement ◽  
Future Generation ◽  
Heat Fluxes ◽  
Concave Surface ◽  
Surface Cooling ◽  
Cooling Enhancement ◽  
Confined Channel

Internal mist/steam blade cooling technology is proposed for the future generation of Advanced Turbine Systems (ATS). Fine water droplets about 5 μm were carried by steam through a slot jet onto a concave heated surface in a confined channel to simulate inner surface cooling at the leading edge of a turbine blade. Experiments covered Reynolds numbers from 7500 to 22,000 and heat fluxes from 3 to 21 kW/m2. Results indicate that the cooling is enhanced significantly near the stagnation point by the mist, decreasing downstream. Unlike impingement onto a flat target where the enhancement vanished at six jet diameters downstream, the cooling enhancement over a concave surface prevails at all points downstream. Similar to the results of the flat surface, the cooling enhancement declines at higher heat fluxes. Up to 200 % cooling enhancement at the stagnation point was achieved by injecting approximately 0.5 % of mist.

A Transient 3D CFD Model of a Progressive Cavity Pump

2016 ◽  
Author(s):  
K. R. Mrinal ◽  
Md. Hamid Siddique ◽  
Abdus Samad
Keyword(s):  
Oil And Gas ◽  
Complex Geometry ◽  
Transient Behavior ◽  
Oil And Gas Industry ◽  
High Viscosity ◽  
Solid Content ◽  
Operating Conditions ◽  
Cfd Model ◽  
Ansys Fluent ◽  
Flow Variables

A progressive cavity pump (PCP) is a positive displacement pump and has been used as an artificial lift method in the oil and gas industry for pumping fluid with solid content and high viscosity. In a PCP, a single-lobe rotor rotates inside a double-lobe stator. Articles on computational works for flows through a PCP are limited because of transient behavior of flow, complex geometry and moving boundaries. In this paper, a 3D CFD model has been developed to predict the flow variables at different operating conditions. The flow is considered as incompressible, single phase, transient, and turbulent. The dynamic mesh model in Ansys-Fluent for the rotor mesh movement is used, and a user defined function (UDF) written in C language defines the rotor’s hypocycloid path. The mesh deformation is done with spring based smoothing and local remeshing technique. The computational results are compared with the experiment results available in the literature. Thepump gives maximum flowrate at zero differential pressure.

Fully Parametric High-Fidelity CFD Model for the Design Optimisation of the Cyclic Stagger Pattern of a Set of Fan Outlet Guide Vanes

2009 ◽  
Author(s):  
Andrea Milli ◽  
Olivier Bron
Keyword(s):  
Complex Geometry ◽  
Single Point ◽  
Sensitivity Study ◽  
Operating Conditions ◽  
High Fidelity ◽  
Cfd Model ◽  
Design Optimisation ◽  
Guide Vanes ◽  
High Loss ◽  
Design Variables

The present paper deals with the redesign of cyclic variation of a set of fan outlet guide vanes by means of high-fidelity full-annulus CFD. The necessity for the aerodynamic redesign originated from a change to the original project requirement, when the customer requested an increase in specific thrust above the original engine specification. The main objectives of this paper are: 1) make use of 3D CFD simulations to accurately model the flow field and identify high-loss regions; 2) elaborate an effective optimisation strategy using engineering judgement in order to define realistic objectives, constraints and design variables; 3) emphasise the importance of parametric geometry modelling and meshing for automatic design optimisation of complex turbomachinery configurations; 4) illustrate that the combination of advanced optimisation algorithms and aerodynamic expertise can lead to successful optimisations of complex turbomachinery components within practical time and costs constrains. The current design optimisation exercise was carried out using an in-house set of software tools to mesh, resolve, analyse and optimise turbomachinery components by means of Reynolds-averaged Navier-Stokes simulations. The original configuration was analysed using the 3D CFD model and thereafter assessed against experimental data and flow visualisations. The main objective of this phase was to acquire a deep insight of the aerodynamics and the loss mechanisms. This was important to appropriately limit the design scope and to drive the optimisation in the desirable direction with a limited number of design variables. A mesh sensitivity study was performed in order to minimise computational costs. Partially converged CFD solutions with restart and response surface models were used to speed up the optimisation loop. Finally, the single-point optimised circumferential stagger pattern was manually adjusted to increase the robustness of the design at other flight operating conditions. Overall, the optimisation resulted in a major loss reduction and increased operating range. Most important, it provided the project with an alternative and improved design within the time schedule requested and demonstrated that CFD tools can be used effectively not only for the analysis but also to provide new design solutions as a matter of routine even for very complex geometry configurations.

Performance Characterization of a Twin Scroll Volute for Turbocharging Applications

2018 ◽  
Author(s):  
Carlo Cravero ◽  
Mario La Rocca ◽  
Andrea Ottonello
Keyword(s):  
Experimental Data ◽  
Scientific Literature ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Automatic Design ◽  
Cfd Model ◽  
Radial Turbine ◽  
Wide Range ◽  
Partial Admission

The use of twin scroll volutes in radial turbine for turbocharging applications has several advantages over single passage volute related to the engine matching and to the overall compactness. Twin scroll volutes are of increasing interest in power unit development but the open scientific literature on their performance and modelling is still quite limited. In the present work the performance of a twin scroll volute for a turbocharger radial turbine are investigated in some detail in a wide range of operating conditions at both full and partial admission. A CFD model for the volute have been developed and preliminary validated against experimental data available for the radial turbine. Then the numerical model has been used to generate the database of solutions that have been investigated and used to extract the performance. Different parameters and indices are introduced to describe the volute aerodynamic performance in the wide range of operating conditions chosen. The above parameters can be used for volute development or matching with a given rotor or efficiently implemented in automatic design optimization strategies.

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