scholarly journals A Numerical Investigation of Moment Coefficient and Flow Structure in a Rotor-Stator Cavity With Rotor Mounted Bolts

2011 ◽  
Author(s):  
Elham Roshani Moghaddam ◽  
Daniel Coren ◽  
Christopher Long ◽  
Abdulnaser Sayma
Keyword(s):  
Experimental Data ◽  
Flow Structure ◽  
Numerical Study ◽  
Research Centre ◽  
Rotating Disc ◽  
Turbine Engine ◽  
Moment Coefficient ◽  
Engine Design ◽  
Commercial Code ◽  
The Moment

This paper presents a numerical study of the effect of rotor mounted bolts on the moment coefficient and flow structure within a rotor-stator cavity representative of modern gas turbine engine design. The CFD computations are performed using the commercial code FLUENT. The simulation methodology is first validated using experimental data from plain co-rotating disc and rotor-stator cavities from the open literature. Comparisons are then made with experimental data obtained from a test rig at the Thermo Fluid Mechanics Research Centre (TFMRC), University of Sussex. Computations were performed at Reφ = 6.8 × 106, Cw = 5929 (λT = 0.35) with different numbers of bolts (0 < N < 60), and also a continuous ring, at r/b = 0.9. The study has improved the current understanding of the effect on moment coefficient and flow structure that rotor mounted protrusions have in rotor-stator systems. It is seen that the contribution of skin friction to the moment coefficient reduces as the number of bolts is increased. The size and shape of the wake created by a rotating bolt also means that the pressure loss per bolt reduces with N but the overall effect is to increase the moment coefficient because there are more bolts.

Approximate Solutions for Flow and Heat Transfer in Pre-Swirl Rotating-Disc Systems

2001 ◽  
Author(s):  
Hasan Karabay ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Swirling Flow ◽  
Approximate Solutions ◽  
Cover Plate ◽  
Rotating Disc ◽  
Reynolds Analogy ◽  
Turbine Engine ◽  
Moment Coefficient ◽  
Heated Disc ◽  
The Moment ◽  
Momentum Integral

The paper presents approximate solutions of the momentum-integral equations for swirling flow in a rotating cavity, which is used to model a cover-plate pre-swirl rotating-disc system in a gas-turbine engine. The solutions give the variation of Cm, the moment coefficient on the rotating discs, with βp, the pre-swirl ratio of the cooling air. Cm decreases from the free-disc value at βp = 0 to zero at βp = βp,crit, and becomes negative when βp > βp,crit. Using the Reynolds analogy, the theoretical distribution of Cm is used to calculate Nuav, the average Nusselt number on the heated disc. This shows that Nuav has a minimum value when βp = βp,crit. The approximate solutions of Cm and Nuav are compared with computed values obtained using an axisymmetric elliptic solver. For most of the conditions considered, the theoretical values of Cm are in good agreement with the computed values. However, unlike the approximate solutions, the computed values of Cm show some dependency on the coolant flow rate. There is reasonable agreement between the theoretical and computed distribution of Nuav provided βp < βp,crit. Near βp,crit there are discontinuities in the computed values, and for larger values of βp, where the Reynolds analogy may be invalid, the theoretical and computed variations of Nuav tend to diverge.

scholarly journals Windage Measurements in a Rotor Stator Cavity With Rotor Mounted Protrusions and Bolts

2012 ◽  
Author(s):  
C. A. Long ◽  
A. L. Miles ◽  
D. D. Coren
Keyword(s):  
Temperature Rise ◽  
Gas Turbines ◽  
Equivalent Diameter ◽  
Effective Diameter ◽  
Rotating Disc ◽  
Clear Trend ◽  
Moment Coefficient ◽  
Flow Parameters ◽  
Rotor Surface ◽  
The Moment

This paper reports an experimental investigation of the windage associated with enclosed rotor-stator systems with superposed throughflow, as commonly found in gas turbine engines. The term windage is often used to describe the viscous heating that arises from the interaction of surfaces and fluids in rotating disc systems. Since the presence of circumferentially discreet geometric features strongly alters the magnitude of Windage measured, the physical mechanisms collectively referred to as windage in this paper are separately described as part of the discussion of results. Tests have been carried out to measure windage directly in the form of shaft torque and also rotor surface temperature. Non-dimensional flow parameters are used to expand the relevance of the data obtained, which encompasses the ranges 0.17 × 107 ≤ Reφ ≤ 1.68 × 107 and 0.24 × 105 ≤ Cw ≤ 1.06 × 105 which corresponds to 0.058 ≤ λT ≤ 0.631. Data has been obtained for smooth disc geometry and also with rotor mounted protrusions of N = 3, 9 and 18; D = 10 mm, 13 mm and 16 mm diameter; H = 11 mm, high, hexagonal bolt shaped protrusions. Bi-hexagonal (twelve sided) bolts of D = 13 mm effective diameter, and height, H = 11 mm, were also tested with conditions closely matched to the 13 mm hexagonal bolts. Finally, tests with 10 mm diameter, 6 mm deep, pockets were also carried out. Over the range of conditions and geometries tested, increasing the number of bolts increases the moment coefficient and windage heating. At low values of turbulent flow parameter, λT, which correspond to rotational speeds between 8000 and 10000 rev/min, increasing the diameter of the bolts shows a clear trend for both increased windage torque and average disc temperature rise. For these conditions, there also appears to be a clear reduction in windage and temperature rise with the bi-hexagonal shaped bolts compared to the equivalent diameter hexagonal bolt form. Variation in the moment coefficient with the number and diameter of bolts is attributed to variations in form drag between the different configurations. The introduction of the recesses onto the disc has very little effect on either windage heating or moment coefficient; this is attributed to the component of windage mechanism in operation and also the relatively small size in comparison to the protrusions studied here. This work contributes to the understanding of windage in gas turbines by introducing new low uncertainty data obtained at engine representative conditions and as such is of benefit to those involved with the design of internal air systems and disc fixtures.

Numerical Investigation Into Non-Synchronous Vibrations of Axial Flow Compressors by the Resonant Tip Clearance Flow

2009 ◽  
Author(s):  
Martin Drolet ◽  
Jean Thomassin ◽  
Huu Duc Vo ◽  
Njuki W. Mureithi
Keyword(s):  
Experimental Data ◽  
Numerical Study ◽  
Axial Flow ◽  
Numerical Results ◽  
Tip Clearance ◽  
Inlet Temperature ◽  
Compressor Blades ◽  
Turbine Engine ◽  
Tip Clearance Flow ◽  
Clearance Flow

This work investigates Non-Synchronous Vibrations (NSV) encountered in a turbine engine axial flow compressor using a Computational Fluid Dynamics (CFD) approach. It has been proposed that the resonance of the tip clearance flow in compressor blades could be the physical mechanism behind NSV. This work’s emphasis is on being able to computationally capture this resonance and predict the critical NSV speed using CFD. This would considerably reduce the costs involved in future hardware design and testing. The model uses the same compressor blade geometry on which experimental validation of the proposed NSV theory was conducted. The flow interaction with blade vibratory motion is modeled using a moving mesh capability and a SAS-SST turbulence model is used for computation. A review of the proposed theory on NSV is done. The CFD model is first verified with experimental data and then characterized to ensure that the simulations are conducted at the proper NSV conditions, in order to assess the resonance of the tip clearance flow. Evidence of this resonance behavior is presented and critical NSV speeds are identified based on numerical results for two different inlet temperature cases and are validated against experimental data. Further study of the actual flow structure associated with NSV is done. Additional remarks on the numerical results are discussed. An iterative design methodology to account for NSV is also proposed based on the current numerical study.

Windage Measurements in a Rotor-Stator System With Superimposed Cooling and Rotor-Mounted Protrusions

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
Xiang Luo ◽  
Da Zhang ◽  
Zhi Tao ◽  
Guoqiang Xu ◽  
Qianshun Wang
Keyword(s):  
Flow Structure ◽  
Flow Parameter ◽  
Test Cases ◽  
Clearance Ratio ◽  
Moment Coefficient ◽  
Gap Ratio ◽  
The Difference ◽  
G Value ◽  
The Moment ◽  
Static Torque

This paper has experimentally studied the windage torque in a rotor-stator system with superimposed central inflow and rotor-mounted protrusions. A novel measurement method has been proposed, and the basic principle is to transform the torque of rotating components into static torque measured by using a static torquemeter. Compared with the previous research, the difference of the moment coefficient for the free plain disk in this paper is within 10%. The disk models used in the experiments included a plain disk and a rotor with 18 protrusions. Plain-disk results were obtained with axial clearances varying from 4.5 mm to 40.5 mm and a stator of the same diameter. Two test cases were performed: one was the case where the flow structure was dominated by the superimposed flow and the other was where rotation dominated the flow structure. For the plain-disk case, as turbulence parameter increases, the sensitivity of the torque to variations of G value also increases, leaving the moment coefficient as a function of the rotational and throughflow Reynolds number only. Comparing to the flow parameter, gap ratio and shroud-clearance ratio have weaker influence on frictional moment coefficient. The rotor with protrusions results showed that the gap ratio had negligible effect on the moment coefficient for the former case; however, the torque decreased by approximately 20% with the decrease of the gap ratio for the latter case. It was also found that, for different configurations, the deviation in the moment coefficient was attributed to variations in form drag. In addition, the moment coefficient was affected by the orientation of bolts with respect to the direction of rotation. The empirical correlations have been proposed for the windage losses of various bolt configurations, and a further discussion about minimizing the windage losses was conducted.

Computation of Heat Transfer for Two Discs Rotating at Different Speeds

2003 ◽  
Author(s):  
Muhsin Kilic ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Structure ◽  
Source Region ◽  
Angular Speed ◽  
Internal Cooling ◽  
Rotating Disc ◽  
Reynolds Analogy ◽  
Nusselt Numbers ◽  
Moment Coefficient

Computations have been conducted for the case where one rotating disc is heated and the other surfaces are adiabatic. Discs rotating at different speeds are found in the internal cooling-air systems of engines, and it is convenient to define Γ as the ratio of the angular speed of the slower (adiabatic) disc to that of the faster (heated) disc. A finite-volume, axisymmetric, elliptic, multigrid solver, employing a low-Reynolds-number k-ε turbulence model, previously used for a complementary study of the flow structure, has been validated using available heat transfer measurements for Γ = −1, 0 and +1. The effect of Γ (for the range −1 ≤ Γ ≤ +1) on heat transfer is then considered for a generic case in which the rotational Reynolds number, Reφ, is 1.25 × 106. (Although this is much lower than the values found in practice, the magnitude of the coolant flow rate was chosen to produce an engine-representative flow structure.) Theoretical values of the adiabatic-disc temperature are in reasonable agreement with computed values for Γ &gt; 0. In the source region, at the smaller radii, there is no effect of Γ on the local Nusselt numbers, Nu, which are consistent with a free-disc correlation. For the average Nusselt numbers, Nuav, the Reynolds analogy shows that the ratio of Nuav/ReφCm, where Cm is the moment coefficient, should be equal to a constant value of 0.259. For Γ ≥ 0, the computed value of this “constant” is within 7% of the theoretical value.

An Experimental and Numerical Study to Support Development of Molten Salt Breeder Reactor

2017 ◽  
Vol 3 (3) ◽  
Author(s):  
A. K. Srivastava ◽  
R. Chouhan ◽  
A. Borgohain ◽  
S. S. Jana ◽  
N. K. Maheshwari ◽  
...  
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Molten Salt ◽  
Cfd Simulation ◽  
Numerical Study ◽  
Natural Circulation ◽  
Research Centre ◽  
Numerical Studies ◽  
Natural Circulation Loop ◽  
Transient Experiments

Conceptual molten salt breeder reactor (MSBR) is under development in Bhabha Atomic Research Centre (BARC) with long-term objective of utilizing abundant thorium available in India. It is based on molten salts, which acts as fuel, blanket, and coolant for the reactor. LiF–ThF4 (77.6–22.4 mol %) is proposed as a blanket salt for Indian MSBR. A laboratory scale molten salt natural circulation loop (MSNCL) named molten active fluoride salt loop (MAFL) has been setup for thermal-hydraulic, material compatibility, and chemistry control studies. Steady-states and transient experiments have been performed in the operating temperature range of 600–750 °C. The loop operates in the power range of 250–550 W. Steady-state correlation given for natural circulation flow in a loop is compared with the steady-state experimental data. The Reynolds number was found to be in the range of 57–114. Computation fluid dynamics (CFD) simulation has also been performed for MAFL using openfoam code, and the results are compared with the experimental data generated in the loop. It has been found that predictions of openfoam are in good agreement with the experimental data. In this paper, features of the loop, its construction, and the experimental and numerical studies performed are discussed in detail.

scholarly journals Numerical study of heat transfer and flow structure over a microscale backstep

2021 ◽  
Vol 60 (3) ◽  
pp. 2759-2768
Author(s):  
Hassnia Hajji ◽  
Lioua Kolsi ◽  
Kaouther Ghachem ◽  
Chemseddine Maatki ◽  
Ahmed Kadhim Hussein ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Flow Structure ◽  
Numerical Study

scholarly journals Interpreting Locked Photographic Data: The Case of Apollo 17 Photo GPN-2000-00113

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 8
Author(s):  
Pyrrhon Amathes ◽  
Paul Christodoulides
Keyword(s):  
Experimental Data ◽  
Computer Simulations ◽  
The Moon ◽  
Geometrical Analysis ◽  
Apparent Position ◽  
Apollo Program ◽  
The Earth ◽  
Novel Approach ◽  
The World ◽  
The Moment

Photography can be used for pleasure and art but can also be used in many disciplines of science, because it captures the details of the moment and can serve as a proving tool due to the information it preserves. During the period of the Apollo program (1969 to 1972), the National Aeronautics and Space Administration (NASA) successfully landed humans on the Moon and showed hundreds of photos to the world presenting the travel and landings. This paper uses computer simulations and geometry to examine the authenticity of one such photo, namely Apollo 17 photo GPN-2000-00113. In addition, a novel approach is employed by creating an experimental scene to illustrate details and provide measurements. The crucial factors on which the geometrical analysis relies are locked in the photograph and are: (a) the apparent position of the Earth relative to the illustrated flag and (b) the point to which the shadow of the astronaut taking the photo reaches, in relation to the flagpole. The analysis and experimental data show geometrical and time mismatches, proving that the photo is a composite.

scholarly journals Experimental Comparison of Radon Domain Approaches for Resident Space Object’s Parameter Estimation

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1298
Author(s):  
Selenia Ghio ◽  
Marco Martorella ◽  
Daniele Staglianò ◽  
Dario Petri ◽  
Stefano Lischi ◽  
...  
Keyword(s):  
Experimental Data ◽  
Rotation Period ◽  
Research Topic ◽  
Experimental Comparison ◽  
Rotational Period ◽  
Space Objects ◽  
Resident Space Objects ◽  
The Moment ◽  
Inverse Radon Transform ◽  
Inverse Radon

The fast and uncontrolled rise of the space objects population is threatening the safety of space assets. At the moment, space awareness solutions are among the most calling research topic. In fact, it is vital to persistently observe and characterize resident space objects. Instrumental highlights for their characterization are doubtlessly their size and rotational period. The Inverse Radon Transform (IRT) has been demonstrated to be an effective method for this task. The analysis presented in this paper has the aim to compare various approaches relying on IRT for the estimation of the object’s rotation period. Specifically, the comparison is made on the basis of simulated and experimental data.

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