Problem statement: Rotating turbine ventilators were generally found in most countries. They were simple in structure, light in weight and cheap to install. It was quite surprising that, the aerodynamics of this common device had not been numerically examined and the design process of most of these ventilators had developed progressively through trial and error methods. Approach: This study was concerned with performing simulation of airflow using CFD technique code name FLUENT so as to visualize the flow behavior around and within a rotating turbine ventilator in addition to determining the aerodynamic forces acting on this device during its operation. To achieve that, the realizable k-ε and RSM turbulence models were used by taking advantage of moving mesh method to simulate the rotation of turbine ventilator and the consequent results were obtained through the sequential process which ensured accuracy of the computations. Results: The results confirmed that, the realizable k-ε model can exhibit a reasonable performance, however not as competence as the RSM model, but of much less computation time. Conclusion/Recommendations: Results from this study, besides ensuring the reliability of utilizing the CFD method in design process of future turbine ventilators, would lead us to a conspicuous progress on increasing the efficiency at reduced cost of wind driven ventilators and similar devices

The advantages of labyrinth-honeycomb seals in turbomachines are widely increasing the usage of them. In this investigation, a numerical study has been done to simulate a labyrinth-honeycomb seal which is commonly used in rotor blade tip. Three-dimensional simulation has been performed by ANSYS-CFX. Simulation results show good agreements with experimental data. To have better understanding of flow behavior within the labyrinth-honeycomb seal, a set of sensitivity analyses on geometry parameters has been carried out. First, a smooth plate has been replaced with honeycomb and sensitivity analyses on geometry parameters have been performed. Then the sensitivity analyses of full model with honeycomb on the geometry parameters are done. The sensitivity analysis is done on: (i) gap between labyrinth and smooth plate or honeycomb, (ii) thickness of labyrinth fins, (iii) height of labyrinth fins, (iv) height of honeycomb cells (only for the honeycomb model), and (v) the effect of different fin thicknesses and their combinations. The results show that as the height of labyrinth rises, there would be much more vortices in the flow field and consequently the overall loss would increase and mass flow rate decreases. In addition, the width of labyrinth fins in small gaps has an important role on the mass flow rate. In small gaps, as the width of labyrinth fin decreases, the mass flow of smooth model decreases, but the mass flow of honeycomb model increases. Furthermore, in large gaps, the existence of smooth plate or honeycomb has minor influence on the flow field. In addition, larger cell depth of honeycombs leads to increasing loss. In this paper, a model with straightforward labyrinth is also investigated and the results have been compared with the stepped labyrinth.

This paper describes the procedure for developing a new airfoil family. This airfoil family applies to heavy-duty, industrial, and aero-derivative gas turbine compressors ranging from subsonic to transonic flow regimes. The airfoil family is generated by filling a database with optimized airfoil geometries. This database is structured in six dimensions, called design space parameters, including inlet Mach number, inlet flow angle, outlet flow angle, axial velocity density ratio, maximum thickness to chord ratio, and solidity. This six-dimensional space includes all compressor blades used in stationary gas turbine compressors. Each set of these design space parameters is related to an optimal geometry produced by the optimization system. The optimization system includes a parametrized airfoil generator, an accurate, fast blade-to-blade flow solver, and an evolutionary optimization algorithm. Airfoils of different stationary gas turbine compressor types are investigated to cover the required design space. Four hundred thirty airfoils, denoted as reference airfoils, are used to define design space borders. Comparing the newly optimized airfoils with reference airfoils revealed superior performance throughout the entire design space. They incorporate these optimized airfoils into a surrogate model, resulting in a fast, optimized airfoil generator (airfoil family). The transonic rotor of the existing multistage compressor has been redesigned according to the developed airfoil family. 3D computational fluid dynamics showed a 2% efficiency improvement for optimized blade row over the original design. Integrating this airfoil family and a streamline curvature code as part of a compressor design system is the main application of this advanced airfoil family.

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To achieve at a more precise designing procedure in axial-compressors as well as a higher pressure ratio value, a comprehensive understanding on the flow aerodynamics and the governing phenomena is required. Existence of these complicated phenomena e.g., simultaneous production of supersonic and subsonic flows, shock-boundary layer interaction, unique incidence phenomenon, etc, makes it difficult to analyze the flow in the transonic compressors. One of the methods which is useful in the modeling of the phenomena occur in the compressors is investigating the flow in the blade to blade passage. In this paper, employing the simultaneous solution of the full Navier-Stokes equations (using the Roe-FDS numerical method) and turbulence equations (using the K–w (SST) model) the flow has been simulated in the blade to blade passage of a transonic compressor. In the following, in order to comparison the predicted results with experimental data, required adjustments and conditions have been taken into account. After passing through the first transonic compressor stages, the flow becomes remarkably compressed. In such conditions, the Reynolds number considerably changes compared to the inflow Reynolds number. In the present work, it is intended to numerically investigate the effects of the inflow Reynolds number on the unique incidence, flow losses, deviation angle, and also shock position changes, in three different important states of “Minimum loss” and “Choked flow” in started conditions and “Stall operation” in unstarted conditions.