Heat and Mass Transfer Characteristics of Water Droplets in Wet Compression Process

2017 ◽  
Author(s):  
Chunlei Liu ◽  
Xiang Li ◽  
Hai Zhang ◽  
Qun Zheng
Keyword(s):  
Fluid Dynamics ◽  
Mass Transfer ◽  
Computational Fluid Dynamics ◽  
Gas Turbine ◽  
Heat And Mass Transfer ◽  
Rotor Blades ◽  
Compressor Stage ◽  
Water Droplets ◽  
Motion Parameters ◽  
Wet Compression

Wet compression technology is an economic and effective approach to improve the performance of gas turbine. In the process of wet compression, the gas turbine engine will ingest a certain amount of water, which can influence the overall performance of the engine. Thermodynamic process and performance of compressor are influenced significantly by heat and mass transfer of the injected water droplets. This study is a new research of investigating theoretically the water droplets effects on the heat and mass transfer characteristics. It focuses on the aerodynamic and thermodynamic effects of the two-phase flow in the compressor stage. The application of Computational Fluid Dynamics (CFD) is the basic method to examine the details of the flow in an axial compressor stage and how it is affected by the presence of water, especially by the water droplets. The computation of water droplets characteristics, are provided by a simulation model of the code named CFX. Considering the change in aerodynamics and thermodynamics feature due to the water droplets, the compressor stage’s performance variations are analyzed. The movement and the evaporation of the water droplets in a compressor stage are simulated and analyzed by using unsteady numerical methods under different water injecting conditions in this paper. The movement characteristics of water droplets in compressor passage are investigated to understand the flow mechanisms responsible for wet compression formation process. The investigation of water droplets in compression can help to understand some phenomenons by using wet compression technology. The flow of water droplets between rotor blades are analyzed by using computational fluid dynamics method. Full coupling between gas and water droplets are adopted, allowing gas and water droplets to affect each other. Many motion parameters of water droplets are researched, such as slip velocity, Weber number and Reynolds number. The forces acting on water droplet are also discussed. Aerodynamic breakup of water droplets and interactions between water droplets and wall are taken into consideration at the same time. The results indicate that: (1) The motion of water droplets in compression areor mainly controlled by drag force. The motion parameters of water droplets changes mostly at the entrance of flow passage between rotor blades, and the turbulence intensity and breakup strength of water droplets reaches their maximum at the entrance. (2) The flow angle of water droplets is bigger than gas in rotor region due to their inertia, which can explain why water droplets have bigger separation degree and are easier to flow toward blade pressure surface. (3) The motion of water droplets in stator region is also important to be investigated for wet compression, and the motion analysis of single water droplets between blades is still needed to be developed, so more investigation will be carried out.

Modelling heat and mass transfer of a broiler house using computational fluid dynamics

2015 ◽  
Vol 136 ◽  
pp. 25-38 ◽  
Author(s):  
Fernando Rojano ◽  
Pierre-Emmanuel Bournet ◽  
Melynda Hassouna ◽  
Paul Robin ◽  
Murat Kacira ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Mass Transfer ◽  
Computational Fluid Dynamics ◽  
Heat And Mass Transfer ◽  
Broiler House

Formation Process of Water Film and Performance Effect on Compressor Stage

2016 ◽  
Author(s):  
Hai Zhang ◽  
Xiaojiang Tian ◽  
Xiaojun Pan ◽  
Jie Zhou ◽  
Qun Zheng
Keyword(s):  
Gas Turbine ◽  
Formation Process ◽  
Water Injection ◽  
Water Film ◽  
Compressor Stage ◽  
Blade Surface ◽  
Water Droplets ◽  
Compression Process ◽  
Turbine Performance ◽  
Wet Compression

In process of wet compression, gas turbine engine will ingest a certain amount of water, which can influence the overall performance of the engine. This phenomenon is particularly significant in the cleaning process of industrial gas turbine and water injection of aero-engine. When the quantity of water ingestion is quite large, the performance of gas turbine will appear deterioration and may lead to flameout, power reduce or even shutdown of the engine, causing accidents. Water droplets will be accumulated on the blade surface where water films could be formed on pressure surface in the wet compression process. The effects of water film on gas turbine engines are aerodynamic, thermodynamic and mechanical. The above-mentioned effects occur simultaneously and be affected by each other. Considering the above effects and the fact that they are time dependent, there are few gas turbine performance researches, which take into account the water film phenomenon. This study is a new research of investigating theoretically the water film effects on a gas turbine performance. It focuses on the aerodynamic and thermodynamic effects of the phenomenon on the compressor stage. The computation of water film thickness, which frequently be formed on the surface of compressor blade, its movement and extra torque demand, are provided by a simulation model of the code. Considering the change in blade’s profile and the thickness feature of the water film, the compressor stage’s performance deterioration is analyzed. In addition to this, movement and the formation of the water film on a compressor stage are simulated and analyzed by using unsteady numerical methods under different water injecting conditions in this paper. The movement characteristics of water droplets in compressor passage are investigated to understand the flow mechanisms responsible for water film formation process. The forming and the tearing process of water film on blade surface are analyzed at different injection conditions. For simulating the real situation, The maximum quantity of injected water can reach 12%. The results indicate that continuity and region of the water film on the blade surface will be developed with the increment of droplet size and injection rate. It is also found that the flow losses near blade surface increases with the tearing process of water film due to the increment of surface roughness.

Application of Computational Fluid Dynamics to Protective Clothing System Evaluation

2000 ◽  
Author(s):  
Phillip W. Gibson ◽  
Majid Charmchi
Keyword(s):  
Fluid Dynamics ◽  
Mass Transfer ◽  
Computational Fluid Dynamics ◽  
Phase Change ◽  
Heat And Mass Transfer ◽  
Protective Clothing ◽  
Phase Changes ◽  
Nonlinear Material ◽  
Physical Factors ◽  
Hydrophilic Polymer

Abstract Convection, diffusion, and phase change processes influence heat and mass transfer through textile materials used in clothing systems. For example, water in a hygroscopic porous textile may exist in vapor or liquid form in the pore spaces or in bound form when it has been absorbed by the solid phase, which is typically some kind of hydrophilic polymer. Phase changes associated with water include liquid evaporation/condensation in the pore spaces and sorption/desorption from hydrophilic polymer fibers. Certain materials such as encapsulated paraffins may also be added to textiles; these materials are designed to undergo a solid-liquid phase change over temperature ranges near human body temperature, which influences the perceived comfort of clothing. Additional factors such as the swelling of the solid polymer due to water imbibition, and the heat of sorption evolved when the water is absorbed by the polymeric matrix, can all be incorporated into the appropriate conservation and transport equations describing heat and mass transfer through clothing layers. These physical factors, nonlinear material properties, and complex multiphase flows make the task of modeling and predicting levels of protection and comfort of various clothing designs difficult and elusive. Computational fluid dynamics (CFD) has proven to be useful at several levels of material and system modeling to evaluate and design protective clothing systems and material components. This paper summarizes current and past work aimed at utilizing CFD techniques for protective clothing applications.

Computational Fluid Dynamics Simulations of Convective Pure Vapor Condensation Inside Vertical Cylindrical Condensers

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Huali Cao ◽  
Jun-De Li
Keyword(s):  
Fluid Dynamics ◽  
Mass Transfer ◽  
Heat Flux ◽  
Computational Fluid Dynamics ◽  
Heat And Mass Transfer ◽  
Vapor Condensation ◽  
Operating Pressure ◽  
Condenser Tube ◽  
Cfd Simulations ◽  
Condensate Film

This paper presents the results from computational fluid dynamics (CFD) simulations of heat and mass transfer of pure vapor flowing and condensing in a vertical cylindrical condenser system at various inlet temperatures, mass flow rates, and operating pressure for the case where the vapor condensation is not completed inside the condenser tube. The heat and mass transfer inside the condenser tube is simulated as single phase flow, and the thin condensate film on the condensing surface is replaced by a set of boundary conditions that couple the CFD simulations inside the condenser tube and the coolant channel. The CFD results are compared with the experimental results, and good agreement has been found for the various measured temperatures. It is found that both the wall temperature and the heat flux vary significantly along the condenser tube, and it is necessary to consider the conjugate problem that consists of the whole condenser system (condenser plus coolant flow) in predicting the pure vapor condensation in a condensing system. The CFD results show that the heat flux along the condenser tube can be increasing for counter-flow condenser, and the condensate film may not be the main limiting factor in the pure vapor condensation. The results from the CFD simulations also show that the estimation of the interface shear stress cannot be based on the bulk velocity of the water vapor alone.

scholarly journals Numerical Simulation of Heat and Mass Transfer in Air-Water Direct Contact Using Computational Fluid Dynamics

2017 ◽  
Vol 205 ◽  
pp. 2537-2544 ◽  
Author(s):  
Xing Wei ◽  
Bingbing Duan ◽  
Xuejun Zhang ◽  
Yang Zhao ◽  
Meng Yu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Mass Transfer ◽  
Computational Fluid Dynamics ◽  
Heat And Mass Transfer ◽  
Direct Contact

A Fully Integrated Approach to Component Zooming Using Computational Fluid Dynamics

2004 ◽  
Vol 128 (3) ◽  
pp. 579-584 ◽  
Author(s):  
Vassilios Pachidis ◽  
Pericles Pilidis ◽  
Fabien Talhouarn ◽  
Anestis Kalfas ◽  
Ioannis Templalexis
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Turbine ◽  
Engine Performance ◽  
Integrated Approach ◽  
High Fidelity ◽  
Performance Simulation ◽  
Fully Integrated ◽  
Engine Component ◽  
Simulation Strategy

Background . This study focuses on a simulation strategy that will allow the performance characteristics of an isolated gas turbine engine component, resolved from a detailed, high-fidelity analysis, to be transferred to an engine system analysis carried out at a lower level of resolution. This work will enable component-level, complex physical processes to be captured and analyzed in the context of the whole engine performance, at an affordable computing resource and time. Approach. The technique described in this paper utilizes an object-oriented, zero-dimensional (0D) gas turbine modeling and performance simulation system and a high-fidelity, three-dimensional (3D) computational fluid dynamics (CFD) component model. The work investigates relative changes in the simulated engine performance after coupling the 3D CFD component to the 0D engine analysis system. For the purposes of this preliminary investigation, the high-fidelity component communicates with the lower fidelity cycle via an iterative, semi-manual process for the determination of the correct operating point. This technique has the potential to become fully automated, can be applied to all engine components, and does not involve the generation of a component characteristic map. Results. This paper demonstrates the potentials of the “fully integrated” approach to component zooming by using a 3D CFD intake model of a high bypass ratio turbofan as a case study. The CFD model is based on the geometry of the intake of the CFM56-5B2 engine. The high-fidelity model can fully define the characteristic of the intake at several operating condition and is subsequently used in the 0D cycle analysis to provide a more accurate, physics-based estimate of intake performance (i.e., pressure recovery) and hence, engine performance, replacing the default, empirical values. A detailed comparison between the baseline engine performance (empirical pressure recovery) and the engine performance obtained after using the coupled, high-fidelity component is presented in this paper. The analysis carried out by this study demonstrates relative changes in the simulated engine performance larger than 1%. Conclusions. This investigation proves the value of the simulation strategy followed in this paper and completely justifies (i) the extra computational effort required for a more automatic link between the high-fidelity component and the 0D cycle, and (ii) the extra time and effort that is usually required to create and run a 3D CFD engine component, especially in those cases where more accurate, high-fidelity engine performance simulation is required.

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