Experimental Validation of Methods Providing Boundary Conditions to Simulate the Evaporation Process of Water Injected Into High Speed Air Flow

2013 ◽  
Author(s):  
P. S. Nagabhushan ◽  
A. Rossetti ◽  
B. Barabas ◽  
J. P. Schnitzler ◽  
A. Kefalas ◽  
...  
Keyword(s):  
Experimental Data ◽  
Boundary Conditions ◽  
Gas Turbines ◽  
High Speed ◽  
Air Flow ◽  
Computational Cost ◽  
Spray Angle ◽  
Diameter Distribution ◽  
Particle Injection ◽  
Lagrange Approach

Water injection into a high speed air flow has been recently investigated by many scientists and is still an important field of research in gas turbine technology. To study the behavior of droplets in gas turbines, expensive experimental tests and their validation with analytical and Computational Fluid Dynamics (CFD) models are necessary. The Euler-Lagrange approach can be used to tackle these problems due to their capability in tracking particles along the domain, relative ease in formulating and applying them to the current industrial problems in terms of acceptable computational cost. However, providing spray boundary conditions using Euler-Lagrange approach is quite challenging because the spray pattern depends upon various parameters like spray angle, velocity, diameter distribution etc. In this paper, to obtain these parameters, two different approaches are described. The first approach depends on an analytical model for velocity and spray angle injection conditions and the second approach depends on an Euler free surface simulation. For diameter distribution, Rosin Rammler distribution function and experimental data are used. When combined together these lead to four particle injection conditions. The results achieved from all the four cases are compared with the experimental data of water droplet evaporation in a high speed air flow obtained from a hot air test rig operating at conditions of real gas turbines.

Development and Validation of a Three-Dimensional Multiphase Flow CFD Analysis for Journal Bearings in Steam and Heavy Duty Gas Turbines

2012 ◽  
Author(s):  
Stephan Uhkoetter ◽  
Stefan aus der Wiesche ◽  
Michael Kursch ◽  
Christian Beck
Keyword(s):  
Experimental Data ◽  
Multiphase Flow ◽  
Gas Turbines ◽  
High Speed ◽  
Three Dimensional ◽  
Air Entrainment ◽  
Journal Bearings ◽  
Heavy Duty ◽  
Present Contribution ◽  
Two Phase

The traditional method for hydrodynamic journal bearing analysis usually applies the lubrication theory based on the Reynolds equation and suitable empirical modifications to cover turbulence, heat transfer, and cavitation. In cases of complex bearing geometries for steam and heavy-duty gas turbines this approach has its obvious restrictions in regard to detail flow recirculation, mixing, mass balance, and filling level phenomena. These limitations could be circumvented by applying a computational fluid dynamics (CFD) approach resting closer to the fundamental physical laws. The present contribution reports about the state of the art of such a fully three-dimensional multiphase-flow CFD approach including cavitation and air entrainment for high-speed turbo-machinery journal bearings. It has been developed and validated using experimental data. Due to the high ambient shear rates in bearings, the multiphase-flow model for journal bearings requires substantial modifications in comparison to common two-phase flow simulations. Based on experimental data, it is found, that particular cavitation phenomena are essential for the understanding of steam and heavy-duty type gas turbine journal bearings.

Role of Inlet Boundary Conditions on Fuel-Air Mixing at Supercritical Conditions

2020 ◽  
Author(s):  
Zachary Harris ◽  
Joshua Bittle ◽  
Ajay Agrawal
Keyword(s):  
Experimental Data ◽  
Boundary Conditions ◽  
Gas Turbines ◽  
Alternative Fuels ◽  
Fuel Injection ◽  
Fluid Dynamic ◽  
Supercritical Conditions ◽  
Complex Interactions ◽  
Significant Research ◽  
Air Mixing

Abstract Advanced engine design and alternative fuels present the possibility of fuel injection at purely supercritical conditions in diesel engines and gas turbines. The complex interactions that govern this phenomenon still need significant research for reliable modeling efforts. Boundary conditions for fuel injection are critical to accurate simulation. However, the flow inside the injector itself is often omitted to reduce the computational efforts, and thus, velocity, mass flux, or total pressure is specified at the injector exit (or domain inlet), often with an assumed top hat profile and assumed turbulence levels. Past studies have shown that such simplified inlet boundary treatment has minimal effects on the results for fuel injection in the compressed liquid phase. However, the validity of this approach at supercritical fuel injection conditions has not been assessed so far. In this study, comprehensive real-gas and binary fluid mixing models have been implemented for computational fluid dynamic (CFD) analysis of fuel-air mixing at supercritical conditions. The model is verified using prior CFD results from the literature. Next, the model is used to investigate the effects of the shape of axial velocity and mass fraction profiles at the inlet boundary with the goal to improve the comparison of predictions to experimental data. Results show that the boundary conditions have a significant effect on the predictions, and none of the cases match precisely with experimental data. The study reveals that the physical location of the inlet boundary might be difficult to infer correctly from the experiments and highlights the need for high-quality, repeatable measurements at supercritical conditions to support the development of relevant high-fidelity models for fuel-air mixing.

ROLE OF INLET BOUNDARY CONDITIONS ON FUEL-AIR MIXING AT SUPERCRITICAL CONDITIONS

2021 ◽  
pp. 1-22
Author(s):  
Zachary Harris ◽  
Joshua Bittle ◽  
Ajay Agrawal
Keyword(s):  
Experimental Data ◽  
Boundary Conditions ◽  
Gas Turbines ◽  
Alternative Fuels ◽  
Fuel Injection ◽  
Fluid Dynamic ◽  
Supercritical Conditions ◽  
Complex Interactions ◽  
Significant Research ◽  
Air Mixing

Abstract Advanced engine design and alternative fuels present the possibility of fuel injection at purely supercritical conditions in diesel engines and gas turbines. The complex interactions that govern this phenomenon still need significant research, particularly the boundary conditions for fuel injection are critical for accurate simulation. However, the flow inside the injector itself is often omitted to reduce the computational efforts, and thus, velocity, mass flux, or total pressure is specified at the injector exit (or domain inlet), often with simplified velocity profiles and turbulence levels. This simplified inlet boundary treatment has minimal effects on results for conventional fuel injection conditions, however, the validity of this approach at supercritical conditions has not been assessed. Comprehensive real-gas and binary fluid mixing models have been implemented for computational fluid dynamic (CFD) analysis of fuel-air mixing at supercritical conditions. The model is verified using prior CFD results from the literature. The model is used to investigate the effects of the shape of axial velocity and mass fraction profiles at the inlet boundary with the goal to improve the comparison of predictions to experimental data. Results show that the boundary conditions have a significant effect on the predictions, and none of the cases match precisely with experimental data. The study reveals that the physical location of the inlet boundary might be difficult to infer correctly from the experiments and highlights the need for high-quality, repeatable measurements at supercritical conditions to support the development of relevant high-fidelity models for fuel-air mixing.

scholarly journals Experimental Study of the Precessing Vortex Core Impact on the Liquid Fuel Spray in a Gas Turbine Model Combustor

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Antoine Renaud ◽  
Sébastien Ducruix ◽  
Laurent Zimmer
Keyword(s):  
Vortex Core ◽  
Gas Turbines ◽  
High Speed ◽  
Large Scale ◽  
Air Flow ◽  
Dynamic Mode Decomposition ◽  
Pollutant Emissions ◽  
Fuel Spray ◽  
Dynamic Mode ◽  
Precessing Vortex Core

Abstract Despite being good candidates for the reduction of pollutant emissions from gas turbines, burners operating in lean premixed prevaporized regimes often face stability issues and can be sensitive to perturbations. The swirling flow used to aerodynamically stabilize the flame can also lead to the appearance of a large-scale coherent flow structure known as the precessing vortex core (PVC). In this study, a swirl-stabilized combustor fed with liquid dodecane is studied at a globally lean operating condition with the help of high-speed diagnostics and dynamic mode decomposition (DMD) as the main postprocessing method. It is shown that the trace of a PVC originating inside the injector is still present in the fuel spray at the entrance of the chamber even though the aerodynamical structure itself is not detectable anymore. The perturbation of the fuel spray is then transmitted to the flame through local equivalence ratio fluctuations. It is observed that the PVC trace on the spray and thus on the flame can be suppressed by air flow modulations generated by a siren device. The suppression of this trace is shown to come from a decay of the aerodynamical structure itself rather than by a change in fuel mixing or vaporization. Analysis of the characteristic frequency of the PVC shows a frequency spread indicating a loss of coherence of the structure with the high-amplitude air flow rate fluctuations.

Experimental Investigation of a Hollow Cone Spray Using Laser Diagnostics

2013 ◽  
Author(s):  
Mithun Das ◽  
Souvick Chatterjee ◽  
Swarnendu Sen ◽  
Achintya Mukhopadhyay
Keyword(s):  
Gas Turbines ◽  
High Speed ◽  
Laser Diagnostics ◽  
Laser Sheet ◽  
Droplet Diameter ◽  
Injection Pressure ◽  
Diameter Distribution ◽  
Hollow Cone ◽  
Wide Range ◽  
Hollow Cone Spray

Atomization of fuel is a key integral part for efficient combustion in gas turbines. This demands a thorough investigation of the spray characteristics using innovative and useful spray diagnostics techniques. In this work, an experimental study is carried out on commercial hollow cone nozzle (Lechler) using laser diagnostics techniques. A hollow cone spray is useful in many applications because of its ability to produce fine droplets. But apart from the droplet diameter, the velocity field in the spray is also an important parameter to monitor and has been addressed in this work. Kerosene is used as the test fuel which is recycled using a plunger pump providing a variation in the injection pressure from 100psi to 300psi. An innovative diagnostic technique used in this study is through illumination of the spray with a continuous laser sheet and capturing the same with a high speed camera. A ray of laser beam is converted to a planer sheet using a lens combination which is used to illuminate a cross section of the hollow cone spray. This provides a continuous planar light source which allows capturing high speed images at 285 fps. The high speed images, thus obtained are processed to understand the non-linearity associated with disintegration of the spray into fine droplets. The images are shown to follow a fractal representation and the fractal dimension is found to increase with rise in injection pressure. Also, using PDPA, the droplet diameter distribution is calculated at different spatial and radial locations at wide range of pressure.

scholarly journals Mixed Euler–Lagrange approach to modeling fiber motion in high speed air flow

2005 ◽  
Vol 29 (3) ◽  
pp. 253-261 ◽  
Author(s):  
Y.C. Zeng ◽  
J.P. Yang ◽  
C.W. Yu
Keyword(s):  
High Speed ◽  
Air Flow ◽  
Fiber Motion ◽  
Lagrange Approach

Unified approach for conjugate heat-transfer analysis of high speed air flow through a water-cooled nozzle

2016 ◽  
Vol 120 (1224) ◽  
pp. 355-373
Author(s):  
F. I. Barbosa ◽  
E. L. Zaparoli ◽  
C. R. Andrade
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
High Speed ◽  
Conjugate Heat Transfer ◽  
Cold Water ◽  
Transfer Problem ◽  
Air Flow ◽  
Heat Transfer Analysis ◽  
Bulk Temperature ◽  
Unified Approach

ABSTRACTThis article presents a unified approach to solve steady-state conjugate heat-transfer problem including simultaneously gas, liquid and solid regions in just one 3D domain, distinguished by their particular properties. This approach reduces approximation errors and the time to solve the problem, which characterise iterative methods based on separated domains. The formulation employs RANS equations, realisablek-ε turbulence model and near-wall treatment model. A commercial CFD code solves the pressure-based segregated algorithm combined with spatial discretisation of second order upwind. The problem consists of a convergent-divergent metallic nozzle that contains cooling channels divided in two segments along the wall. The nozzle wall insulates the high-speed hot air flow, dealt as perfect gas, from the two low-speed cold water flows, dealt as compressed liquid, both influenced by transport properties dependent of the local temperature. The verification process uses three meshes with increasing resolutions to demonstrate the independence of the results. The validation process compares the simulation results with experimental data obtained in high-enthalpy wind tunnel, demonstrating good compliance between them. Results for the bulk temperature rise of the water in the second cooling segment of the nozzle showed good agreement with available experimental data. Numerical simulations also provided wall temperature and heat flux for the gas and liquid sides. Besides, distribution of temperature, pressure, density and Mach number were plotted along the nozzle centerline showing a little disturbance downstream the throat. This phenomenon has been better visualised by means of 2D maps of those variables. The analysis of results indicates that the unified approach herein presented can make easier the task of simulating the conjugate convection-conduction heat-transfer in a class of problems related to regeneratively cooled thrust chambers.

scholarly journals Experimental Study of the Precessing Vortex Core Impact on the Liquid Fuel Spray in a Gas Turbine Model Combustor

2019 ◽  
Author(s):  
Antoine Renaud ◽  
Sébastien Ducruix ◽  
Laurent Zimmer
Keyword(s):  
Vortex Core ◽  
Gas Turbines ◽  
High Speed ◽  
Large Scale ◽  
Air Flow ◽  
Dynamic Mode Decomposition ◽  
Pollutant Emissions ◽  
Fuel Spray ◽  
Dynamic Mode ◽  
Precessing Vortex Core

Abstract Despite being good candidates for the reduction of pollutant emissions from gas turbines, burners operating in Lean Premixed Prevaporized regimes often face stability issues and can be sensitive to perturbations. The swirling flow used to aero-dynamically stabilize the flame can also lead to the appearance of a large-scale coherent flow structure known as the Precessing Vortex Core (PVC). In the present study, a swirl-stabilized combustor fed with liquid dodecane is studied at a globally lean operating condition with the help of high-speed diagnostics and Dynamic Mode Decomposition (DMD) as the main post-processing method. It is shown that the trace of a PVC originating inside the injector is still present in the fuel spray at the entrance of the chamber even though the aerodynamical structure itself is not detectable anymore. The perturbation of the fuel spray is then transmitted to the flame through local equivalence ratio fluctuations. It is observed that the PVC trace on the spray and thus on the flame can be suppressed by air flow modulations generated by a siren device. The suppression of this trace is shown to come from a decay of the aerodynamical structure itself rather than by a change in fuel mixing or vaporization. Analysis of the characteristic frequency of the PVC shows a frequency spread indicating a loss of coherence of the structure with the high amplitude air flow rate fluctuations.

Experimental Investigation of a Hollow Cone Spray Using Laser Diagnostics

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Mithun Das ◽  
Souvick Chatterjee ◽  
Achintya Mukhopadhyay ◽  
Swarnendu Sen
Keyword(s):  
Gas Turbines ◽  
High Speed ◽  
Laser Diagnostics ◽  
Laser Sheet ◽  
Droplet Diameter ◽  
Injection Pressure ◽  
Diameter Distribution ◽  
Hollow Cone ◽  
Wide Range ◽  
Hollow Cone Spray

Atomization of fuel is a key integral part for efficient combustion in gas turbines. This demands a thorough investigation of the spray characteristics using innovative and useful spray diagnostics techniques. In this work, an experimental study is carried out on a commercial hollow cone nozzle (Lechler) using laser diagnostics techniques. A hollow cone spray is useful in many applications because of its ability to produce fine droplets. But apart from the droplet diameter, the velocity field in the spray is also an important parameter to monitor and has been addressed in this work. Kerosene is used as the test fuel, which is recycled using a plunger pump providing a variation in the injection pressure from 100 to 300 psi. An innovative diagnostic technique used in this study is through illumination of the spray with a continuous laser sheet and capturing the same with a high speed camera. A ray of a laser beam is converted to a planer sheet using a lens combination which is used to illuminate a cross section of the hollow cone spray. This provides a continuous planar light source which allows capturing high speed images at 285 fps. The high speed images thus obtained are processed to understand the nonlinearity associated with disintegration of the spray into fine droplets. The images are shown to follow a fractal representation and the fractal dimension is found to increase with rise in injection pressure. Also, using PDPA, the droplet diameter distribution is calculated at different spatial and radial locations at a wide range of pressure.

Analysis of Supersonic Turbulent Boundary Layers Over Rough Surfaces Using the K-Omega and Stress-Omega Models

2005 ◽  
Author(s):  
Guanghong Guo ◽  
M. A. R. Sharif
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Rough Surfaces ◽  
Computational Cost ◽  
Reynolds Stress Model ◽  
Surface Boundary ◽  
Mean Flow ◽  
Surface Boundary Conditions ◽  
The Mean ◽  
Layer Flow

In this study, the influence of surface roughness in the prediction of the mean flow and turbulent properties of a high-speed supersonic (M = 2.9, Re/m = 2.0e7) turbulent boundary layer flow over a flat plate is performed using the k-ω and the stress-ω models. Six wall topologies, including a smooth and five rough surfaces consisting of three random sand-grain plates and two uniformly machined plates were tested. Experimental data are available for these configurations. It is observed that, for smooth surface, both k-ω and stress-ω models perform remarkably well in predicting the mean flow and turbulent quantities in supersonic flow. For rough surfaces, both models matched the experimental data profiles fairly well for lower values of the roughness height. Overall, the k-ω model performed better than the stress-ω model. The stress-ω model did not show any strong advantages to make up for the extra computational cost associated with a Reynolds stress model. The simulation results indicated that the prescription for the surface boundary conditions for ω in both models, especially for the stress-ω model, need to be refined encountering high roughness numbers and reconsidered to include the geometric factor.

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