Experimental and Numerical Study of Orifice Discharge Coefficients in High-Speed Rotating Disks

1996 ◽  
Vol 118 (2) ◽  
pp. 400-407 ◽  
Author(s):  
S. Wittig ◽  
S. Kim ◽  
R. Jakoby ◽  
I. Weißert
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Tangential Velocity ◽  
Laser Doppler Velocimeter ◽  
Rotating Disks ◽  
Complex Flow ◽  
Local Flow ◽  
Discharge Coefficients

Experimental and numerical results of the flow through orifices in rotating disks are presented, with emphasis on basic physical phenomena. It is shown that rotational effects strongly influence the massflow discharged, a phenomenon that cannot be modeled by a stationary setup. The study includes the determination of discharge coefficients under variation of the length-to-diameter ratio, pressure ratio, and rotational speed. The pressure ratio covers low as well as critical values, the maximum rotational speed is 10,000 rpm, which is equivalent to a tangential velocity of 110 m/s. In order to understand the flow structure, local flow velocities were measured by means of a two-dimensional Laser-Doppler Velocimeter. Phase-resolved measurements have been carried out in front of and behind the orifices. A three-dimensional Finite-Volume Code with body-fitted coordinates in a rotating frame of reference is employed for the numerical analysis and the verification of its possibilities and limitations. The results reveal a very complex flow field, which is dominated by high velocity gradients in close vicinity to the orifices. The comparison of the computational solutions with the experimental data shows good agreement. Based on the measurements in combination with the numerical solution, a detailed insight into the physical properties of the flow is achieved.

Experimental and Numerical Study of Orifice Discharge Coefficients in High Speed Rotating Disks

1994 ◽  
Author(s):  
S. Wittig ◽  
S. Kim ◽  
R. Jakoby ◽  
I. Weißert
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Tangential Velocity ◽  
Laser Doppler Velocimeter ◽  
Rotating Disks ◽  
Complex Flow ◽  
Local Flow ◽  
Discharge Coefficients

Experimental and numerical results of the flow through orifices in rotating disks are presented, with emphasis on basic physical phenomena. It is shown, that rotational effects strongly influence the massflow discharged, a phenomenon which cannot be modelled by a stationary setup. The study includes the determination of discharge coefficients under variation of the length to diameter ratio, pressure ratio and rotational speed. The pressure ratio covers low as well as critical values, the maximum rotational speed is 10000 rpm which is equivalent to a tangential velocity of 110 m/s. In order to understand the flow structure, local flow velocities were measured by means of a 2D Laser-Doppler-Velocimeter. Phase-resolved measurements have been carried out in front of and behind the orifices. A 3D Finite-Volume-Code with bodyfitted coordinates in a rotating frame of reference is employed for the numerical analysis and the verification of its possibilities and limitations. The results reveal a very complex flow field, which is dominated by high velocity gradients in close vicinity to the orifices. The comparison of the computational solutions with the experimental data shows good agreement. Based on the measurements in combination with the numerical solution, a detailed insight into the physical properties of the flow is achieved.

scholarly journals Numerical Study for Optimizing Heat Transfer in High Speed Rotating Components

1998 ◽  
Vol 4 (3) ◽  
pp. 151-161 ◽  
Author(s):  
S. Wittig ◽  
S. Kim ◽  
Th. Scherer ◽  
I. Weissert
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
High Speed ◽  
Numerical Study ◽  
Rotating Disks ◽  
Rotating System ◽  
Local Flow ◽  
Flow Through ◽  
Air Flows ◽  
Cooling Air

Cooling of high speed rotating components is a typical situation found in turbomachinery as well as in automobile engines. Accurate knowledge of discharge coefficients and heat transfer of related components is essential for the high performance of the whole engine. This can be achieved by minimized cooling air flows and avoidance of hot spots. In high speed rotating clutches for example aerodynamic investigations improving heat transfer have not been considered in the past. Advanced concepts of modern plate design try to reduce thermal loads by convective cooling methods. Therefore, secondary cooling air flows have to be enhanced by an appropriate design of the rotor stator system with orifices. CFD modelling is used to improve the basic understanding of the flow field in typical geometries used in these systems.The computational results are obtained by a 3-D-finite-volume-code based on body fitted structured grids. The Navier Stokes equations are solved by a pressure-correction method combined with the standard k-e-turbulence model. Considering the rotation of orifices in disks or shafts, the frame of reference has to be changed to the rotating system. The flow through orifices in high speed rotating disks can be calculated with a high level of accuracy in comparison with experiments as shown in Wittig et al. [1994].Numerical results of the flow in a high speed rotating system are presented with emphasis on geometrical variations. Calculations are carried out in order to find an optimum design in terms of position and size of the orifices in the housing. These variations induce different physical phenomena. Special consideration is directed towards the basic problems of the flow through orifices in high speed rotating disks and shafts and the flow inside rotor-stator systems. As expected, the very complex flow fields are dominated by rotational effects. In addition it is shown that differences occur between the configuration of optimized mass flow rate and the geometry with a maximum of total heat transfer. Obviously, optimization procedures are dependent on the knowledge of the local flow field and cannot be performed without advanced CFD-methods. It is demonstrated that the approach presented here is suitable for these tasks.

Effect of Tip Clearance on the Aeroelastic Stability of a Wide-Chord Fan Rotor

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Xu Dong ◽  
Yingjie Zhang ◽  
Ziqing Zhang ◽  
Xingen Lu ◽  
Yanfeng Zhang
Keyword(s):  
High Speed ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Influence Coefficient ◽  
Pressure Amplitude ◽  
Aeroelastic Stability ◽  
Local Flow ◽  
Blade Loading ◽  
Unsteady Pressure ◽  
Aerodynamic Damping

Abstract This research presents a series of simulations that investigate the effects of tip clearance on the aeroelastic stability of a wide-chord high-speed transonic fan rotor. The results show that the stall margin and the total pressure ratio decreases as the tip clearance increases. The effect of tip clearance on the blade loading can extend to 30% span. The phase of the influence coefficient without tip clearance is different from that with clearance, which causes the most unstable aerodynamic damping to shift in the nodal diameter. As the clearance increases from 0.25 mm to 2 mm, the damping decreases. The nonmonotonic behavior found by other researchers was not observed in this study. We conclude that the tip clearance affects the aeroelastic stability in two ways. The first is to change the blade loading so that the amplitude of the unsteady pressure increases or decreases, while the phase hardly changes, resulting in changes in aerodynamic damping. The second is to change the local flow so that the unsteady pressure amplitude and the phase change locally.

Microturbine Rotational Speed Selection

2013 ◽  
Author(s):  
C. Rodgers
Keyword(s):  
Permanent Magnet ◽  
Output Power ◽  
Thermal Efficiency ◽  
Rotational Speed ◽  
High Speed ◽  
Mechanical Design ◽  
Pressure Ratio ◽  
Direct Drive ◽  
Power Turbine ◽  
Speed Selection

This paper delves upon the Aero-Thermodynamic performance and Mechanical design aspects of microturbines comprising a single shaft radial compressor driven by a single stage radial inflow turbine with a combustor and recuperator sized to directly drive a permanent magnet type high speed generator with an output power in the 5–10KW bracket and commensurate rotational speeds in the 100–200 krpm range. It is initially shown that stipulation of a cycle design point output power, turbine inlet or exit temperatures, and compressor pressure ratio delivering optimum thermal efficiency inherently confines rotational speed selection, and that independent rotational speed choice away from those identified optimum speed regimes may result in cycle thermal efficiency compromises. Confining the cycle analysis within temperature limits of cost competitive superalloys and foil materials reveals that the achievement of optimum thermal efficiency is more dependent on temperature at the turbine exit rather than at inlet. Albeit the choice of rotational speed is of particular importance in the compressor and turbine design it moreover is dominant in the mechanical design of the rotating assembly in terms of high speed bearing life and shaft dynamic stability. As a consequence rotating assembly and bearing design options suitable for direct drive permanent magnet generators are reviewed and recommendations offered as to the prime candidate assemblies for future microturbines in the 5.0 to 10.0 kW power output range.

Modeling of Tarbela Reservoir and Water Flow Simulation Through Its Spillways

2010 ◽  
Author(s):  
Muhammad Abid ◽  
Muftooh Ur Rehman Siddiqi
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Discharge Rate ◽  
Flow Simulation ◽  
Maximum Velocity ◽  
Warming Trend ◽  
Height Distribution ◽  
Complex Flow ◽  
Local Flow ◽  
Buoyant Force

This numerical study is performed to predict the flow patterns and characteristics in Tarbela dam which is a multipurpose dam during the summer season the flow of the dam reaches to its design capacity or near flooding due to weather changes resulting from the global warming trend. A 3D model was made in Pro-Engineer® and meshed in ICEM CFD®. Commercially known software, ANSYS CFX®, was applied to numerically solve the Navier-Stokes equations for solution domain. The calculated results such as pressure, velocities, flow rate, surface height, and water buoyant force were compared with the actual data where available. The numerical calculations show uneven discharge through each gate due to the complex flow pattern just upstream of the weir. Maximum velocity was observed along the spillways outlet. In conclusion, the results from numerical simulation are generally well agreed with the existing data, the flow information such as flow field patterns at increased flow, local flow disturbances, discharge rate and surface height distribution obtained used for the behavior of existing dam and can be used for engineering design purpose of future dams.

Blade Tip Carving Effects on the Aero-Thermal Performance of a Transonic Turbine

2013 ◽  
Author(s):  
C. De Maesschalck ◽  
S. Lavagnoli ◽  
G. Paniagua
Keyword(s):  
High Speed ◽  
Thermal Stresses ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Geometrical Parameters ◽  
Complex Flow ◽  
Turbine Rotor Blade ◽  
Blade Tip ◽  
Transonic Turbine

Tip leakage flows in unshrouded high speed turbines cause large aerodynamic penalties, induce significant thermal loads and give rise to intense thermal stresses onto the blade tip and casing endwalls. In the pursuit of superior engine reliability and efficiency, the turbine blade tip design is of paramount importance and still poses an exceptional challenge to turbine designers. The ever-increasing rotational speeds and pressure loadings tend to accelerate the tip flow velocities beyond the transonic regime. Overtip supersonic flows are characterized by complex flow patterns, which determine the heat transfer signature. Hence, the physics of the overtip flow structures and the influence of the geometrical parameters on the overtip flow require further understanding to develop innovative tip designs. Conventional blade tip shapes are not adequate for such high speed flows and hence, potential for enhanced performances lays in appropriate tip shaping. The present research aims to quantify the prospective gain offered by a fully contoured blade tip shape against conventional geometries such as a flat and squealer tip. A detailed numerical study was conducted on a modern transonic turbine rotor blade (Reynolds number is 5.5 × 105, relative exit Mach number is 0.9) by means of three-dimensional Reynolds-Averaged Navier-Stokes calculations. The novel contoured tip geometry was designed based on a 2D tip shape optimization in which only the upper 2% of the blade span was modified. This study yields a deeper insight into the application of blade tip carving in high speed turbines and provides guidelines for future tip designs with enhanced aerothermal performances.

Centrifugal Compressor of a 100 kW Microturbine: Part 2 — Numerical Study of Impeller-Diffuser Interaction

2003 ◽  
Author(s):  
E. Benini ◽  
A. Toffolo
Keyword(s):  
Fluid Dynamics ◽  
High Speed ◽  
Numerical Study ◽  
Compressor Stage ◽  
Complex Flow ◽  
Vaned Diffuser ◽  
3D Geometry ◽  
Rotor Stator Interaction ◽  
Unsteady Simulation ◽  
Unsteady Behavior

The interaction between impeller and diffuser blades in high-speed centrifugal compressors is thought to have a significant influence on the flow within the diffuser. In this part, Computational Fluid Dynamics is exploited to simulate, visualize and analyze the complex flow generated by the interaction, with particular emphasis on the unsteady behavior of the vaned diffuser of the microturbine compressor studied in part 1. For this purpose, the 3D geometry of the compressor stage is studied by performing a fully unsteady simulation of rotor-stator interaction. The results of the unsteady calculation regarding the diffuser performance are then averaged in time and compared with those obtained with a fully steady and decoupled computation in order to highlight the main difference between the two approaches.

Numerical Study on the Effects of Blade Leading Edge Shape to the Performance of Supersonic Rotor

2003 ◽  
Author(s):  
Kicheol Park
Keyword(s):  
Rotational Speed ◽  
Pressure Loss ◽  
Total Pressure ◽  
Performance Test ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Total Pressure Loss ◽  
Manufacturing Cost ◽  
Blade Leading Edge

Recently, it is required to design a fan and compressor with higher stage pressure ratio while maintaining adiabatic efficiency high also. To increase the stage pressure ratio, blade rotational speed or diffusion factor should be increased. In the case of increased rotational speed, relative speed of flow at blade leading edge is well supersonic. With supersonic rotor blade, total pressure loss is mainly due to leading edge shock waves and the thickness should be thin enough to minimize this. As a result, the blade is like to be week in terms of mechanical strength and the manufacturing cost would be increased because high-precision NC machining is required. Furthermore, it is one of the biggest hurdles to maintain proper level of thickness while one making small stages. In this paper, aerodynamic performance of supersonic rotor blades with different leading edge thickness and shapes are calculated using the finite volume method. The effects of blade leading edge shape and thickness to the performance are investigated especially in terms of total pressure loss and the already known loss correlations of leading edge thickness are examined. Subsequently this will be verified by performance test on rig.

Performance Desensitization for a High-Speed Axial Compressor

2018 ◽  
Author(s):  
Yassine Souleimani ◽  
Huu Duc Vo ◽  
Hong Yu
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Lower Sensitivity ◽  
Tip Leakage Flow ◽  
Stall Margin ◽  
Casing Treatment ◽  
Compressor Rotor

The increase in compressor tip clearance over the lifespan of an aero-engine leads to a long-term degradation in its fuel consumption and operating envelope. A highly promising recent numerical study on a theoretical high-speed axial compressor rotor proposed a novel casing treatment to decrease performance and stall margin sensitivity to tip clearance increase. This paper aims to apply and analyze, through CFD simulations, this casing treatment concept to a representative production axial compressor rotor with inherently lower sensitivity to tip clearance increase and complement the explanation on the mechanism behind the reduction in sensitivity. Simulations of the baseline rotor showed that the lower span region contribute as much to the pressure ratio sensitivity as the tip region which is dominated by tip leakage flow. In contrast, the efficiency sensitivity is mainly driven by losses occurring in the tip region. The novel casing treatment was successfully applied to the baseline rotor through a design refinement. Although the casing treatment causes some penalty in nominal performance, it completely reversed the pressure ratio sensitivity (i.e. pressure ratio increases with tip clearance) and reduced the efficiency sensitivity. The reversed pressure ratio sensitivity is explained by a rotation in the core flow in the lower span region indirectly induced by the flow injection from the casing treatment. The lower efficiency sensitivity comes from a reduction in the amount of fluid that crosses the tip clearance of two adjacent blades, known as double leakage. The casing treatment’s beneficial effect on stall margin sensitivity is less obvious because of the stall inception type of the baseline rotor and its change in the presence of the casing treatment.

Blade Tip Carving Effects on the Aerothermal Performance of a Transonic Turbine

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
C. De Maesschalck ◽  
S. Lavagnoli ◽  
G. Paniagua
Keyword(s):  
High Speed ◽  
Thermal Stresses ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Geometrical Parameters ◽  
Complex Flow ◽  
Leakage Flows ◽  
Blade Tip ◽  
Exit Mach Number

Tip leakage flows in unshrouded high speed turbines cause large aerodynamic penalties, induce significant thermal loads and give rise to intense thermal stresses onto the blade tip and casing endwalls. In the pursuit of superior engine reliability and efficiency, the turbine blade tip design is of paramount importance and still poses an exceptional challenge to turbine designers. The ever-increasing rotational speeds and pressure loadings tend to accelerate the tip flow velocities beyond the transonic regime. Overtip supersonic flows are characterized by complex flow patterns, which determine the heat transfer signature. Hence, the physics of the overtip flow structures and the influence of the geometrical parameters require further understanding to develop innovative tip designs. Conventional blade tip shapes are not adequate for such high speed flows and hence, potential for enhanced performances lays in appropriate tip shaping. The present research aims to quantify the prospective gain offered by a fully contoured blade tip shape against conventional geometries such as a flat and squealer tip. A detailed numerical study was conducted on a modern rotor blade (Reynolds number of 5.5 × 105 and a relative exit Mach number of 0.9) by means of three-dimensional (3D) Reynolds-averaged Navier–Stokes (RANS) calculations. Two novel contoured tip geometries were designed based on a two-dimensional (2D) tip shape optimization in which only the upper 2% of the blade span was modified. This study yields a deeper insight into the application of blade tip carving in high speed turbines and provides guidelines for future tip designs with enhanced aerothermal performances.

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