On the Reynolds-Number Sensitivity of Inlet Flow at Mach Numbers Beyond 7

AIAA Journal ◽  
2021 ◽  
pp. 1-5
Author(s):  
Hao Chen ◽  
Zi-Ren Wang ◽  
Qi-Fan Zhang ◽  
Xiao-Yuan Zhang ◽  
Lian-Jie Yue
Keyword(s):  
Reynolds Number ◽  
Inlet Flow ◽  
Mach Numbers

scholarly journals Investigation of Flows in Rectangular Diffusers With Inlet Flow Distortion

1982 ◽  
Author(s):  
M. M. Al-Mudhafar ◽  
M. Ilyas ◽  
F. S. Bhinder
Keyword(s):  
Experimental Study ◽  
Velocity Profiles ◽  
Pressure Recovery ◽  
Two Dimensional ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Inlet Velocity ◽  
Inlet Distortion ◽  
Mach Numbers ◽  
Inlet Flow Distortion

The results of an experimental study on the influence of severely distorted velocity profiles on the performance of a straight two-dimensional diffuser are reported. The data cover entry Mach numbers ranging from 0.1 to 0.6 and several inlet distortion levels. The pressure recovery progressively deteriorates as the inlet velocity is distorted.

Wake-Induced Unsteady Stagnation-Region Heat Transfer Measurements

1994 ◽  
Vol 116 (1) ◽  
pp. 29-38 ◽  
Author(s):  
P. J. Magari ◽  
L. E. LaGraff
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Edge Region ◽  
Isentropic Compression ◽  
Stagnation Region ◽  
Stagnation Line ◽  
Wide Range ◽  
Mach Numbers

An experimental investigation of wake-induced unsteady heat transfer in the stagnation region of a cylinder was conducted. The objective of the study was to create a quasi-steady representation of the stator/rotor interaction in a gas turbine using two stationary cylinders in crossflow. In this simulation, a larger cylinder, representing the leading-edge region of a rotor blade, was immersed in the wake of a smaller cylinder, representing the trailing-edge region of a stator vane. Time-averaged and time-resolved heat transfer results were obtained over a wide range of Reynolds number at two Mach numbers: one incompressible and one transonic. The tests were conducted at Reynolds numbers, Mach numbers, and gas-to-wall temperature ratios characteristic of turbine engine conditions in an isentropic compression-heated transient wind tunnel (LICH tube). The augmentation of the heat transfer in the stagnation region due to wake unsteadiness was documented by comparison with isolated cylinder tests. It was found that the time-averaged heat transfer rate at the stagnation line, expressed in terms of the Frossling number (Nu/Re), reached a maximum independent of the Reynolds number. The power spectra and cross-correlation of the heat transfer signals in the stagnation region revealed the importance of large vortical structures shed from the upstream wake generator. These structures caused large positive and negative excursions about the mean heat transfer rate in the stagnation region.

The Effects of Freestream Turbulence, Turbulence Length Scale, and Exit Reynolds Number on Turbine Blade Heat Transfer in a Transonic Cascade

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
J. S. Carullo ◽  
S. Nasir ◽  
R. D. Cress ◽  
W. F. Ng ◽  
K. A. Thole ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbine Blade ◽  
Surface Heat ◽  
Length Scale ◽  
Freestream Turbulence ◽  
Surface Heat Transfer ◽  
Mach Numbers ◽  
Turbulence Length ◽  
Turbulence Length Scale

This paper experimentally investigates the effect of high freestream turbulence intensity, turbulence length scale, and exit Reynolds number on the surface heat transfer distribution of a turbine blade at realistic engine Mach numbers. Passive turbulence grids were used to generate freestream turbulence levels of 2%, 12%, and 14% at the cascade inlet. The turbulence grids produced length scales normalized by the blade pitches of 0.02, 0.26, and 0.41, respectively. Surface heat transfer measurements were made at the midspan of the blade using thin film gauges. Experiments were performed at the exit Mach numbers of 0.55, 0.78, and 1.03, which represent flow conditions below, near, and above nominal conditions. The exit Mach numbers tested correspond to exit Reynolds numbers of 6×105, 8×105, and 11×105, based on true chord. The experimental results showed that the high freestream turbulence augmented the heat transfer on both the pressure and suction sides of the blade as compared with the low freestream turbulence case. At nominal conditions, exit Mach 0.78, average heat transfer augmentations of 23% and 35% were observed on the pressure side and suction side of the blade, respectively.

Requirements and Limitations of Controlling Turbine Tip Shroud Cavity Flow Mixing With Bladelets on Rotating Shroud

2015 ◽  
Author(s):  
Timothy R. Palmer ◽  
Choon S. Tan ◽  
Matthew Montgomery ◽  
Anthony Malandra ◽  
David Little ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Cavity Flow ◽  
Efficiency Gain ◽  
Turbine Stage ◽  
Loss Mechanism ◽  
Inlet Flow ◽  
Flow Asymmetry ◽  
Low Reynolds ◽  
Tip Shroud

A potential means of significantly reducing the cavity exit mixing loss, a dominant primary loss mechanism in turbine tip shroud cavity flow, is assessed. The operational constraints on the turbine stage dictate that losses may only be mitigated through configuration changes within the cavity. A configuration, known herein as the Hybrid Blade, features a shrouded main blade with a row of high aspect ratio bladelets affixed to the rotating shroud is formulated and shown to nearly eliminate the cavity exit mixing loss. However the Hybrid Blade configuration incurs a penalty associated with bladelet low Reynolds number effects, cavity inlet flow asymmetry introduced by the scalloped shroud, and a resulting mismatch with the upstream vane as well as downstream diffuser. This penalty offsets the efficiency gain from mitigating cavity exit mixing loss. For the Hybrid Blade system, it can thus be inferred that the turbine stage and the diffuser need to be reconfigured to accommodate the modified tip shroud, and the bladelets redesigned for low Reynolds number operation and cavity inlet flow asymmetry to achieve an overall benefit.

The Effects of Freestream Turbulence, Turbulence Length Scale and Exit Reynolds Number on Turbine Blade Heat Transfer in a Transonic Cascade

2007 ◽  
Author(s):  
J. S. Carullo ◽  
S. Nasir ◽  
R. D. Cress ◽  
W. F. Ng ◽  
K. A. Thole ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbine Blade ◽  
Surface Heat ◽  
Length Scale ◽  
Freestream Turbulence ◽  
Surface Heat Transfer ◽  
Mach Numbers ◽  
Turbulence Length ◽  
Turbulence Length Scale

This paper experimentally investigates the effect of high freestream turbulence intensity, turbulence length scale, and exit Reynolds number on the surface heat transfer distribution of a turbine blade at realistic engine Mach numbers. Passive turbulence grids were used to generate freestream turbulence levels of 2%, 12%, and 14% at the cascade inlet. The turbulence grids produced length scales normalized by the blade pitch of 0.02, 0.26, and 0.41, respectively. Surface heat transfer measurements were made at the midspan of the blade using thin film gauges. Experiments were performed at exit Mach numbers of 0.55, 0.78 and 1.03 which represent flow conditions below, near, and above nominal conditions. The exit Mach numbers tested correspond to exit Reynolds numbers of 6 × 105, 8 × 105, and 11 × 105, based on true chord. The experimental results showed that the high freestream turbulence augmented the heat transfer on both the pressure and suction sides of the blade as compared to the low freestream turbulence case. At nominal conditions, exit Mach 0.78, average heat transfer augmentations of 23% and 35% were observed on the pressure side and suction side of the blade, respectively.

Hot-Wire Measurements in a Plane Turbulent Jet

1965 ◽  
Vol 32 (4) ◽  
pp. 721-734 ◽  
Author(s):  
Gunnar Heskestad
Keyword(s):  
Reynolds Number ◽  
Energy Balance ◽  
Turbulent Jet ◽  
Turbulent Intensity ◽  
Turbulent Motion ◽  
Hot Wire ◽  
Reynolds Number Effect ◽  
Mach Numbers ◽  
Velocity Derivative ◽  
Flatness Factor

Results from hot-wire measurements in a plane turbulent jet of air are reported. The jet was found to be approximately self-preserving sufficiently far downstream where measurements of intermittency and data for calculating the energy balance of the turbulent motion were obtained. Measurements were also made of the effect of the jet speed (assumed equivalent to a Reynolds-number effect for the low Mach numbers used) on the centerline development of turbulent intensity and the flatness factor of the velocity derivative at a fixed downstream centerline location.

The Influence of Reynolds Number, Mach Number and Incidence Effects on Loss Production in Low Pressure Turbine Airfoils

2006 ◽  
Author(s):  
Rau´l Va´zquez ◽  
Antonio Antoranz ◽  
David Cadrecha ◽  
Leyre Arman˜anzas
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Low Pressure ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Flow Features ◽  
Mach Numbers ◽  
Turbine Airfoils ◽  
Annular Cascade ◽  
The Impact

This paper presents an experimental study of the flow field in an annular cascade of Low Pressure Turbine airfoils. The influence of Reynolds number, Mach number and incidence on profile and end wall losses have been investigated. The annular cascade consisted of 100 high lift, high aspect ratio, high turning blades that are characteristic of modern LP Turbines. The investigation was carried out for a wide range of Reynolds numbers, extending from 120k to 315k, exit Mach numbers, from 0.5 to 0.9, and incidences from −20 to +14 degrees. Results clearly indicate a significant effect of incidence and Mach number in secondary loss production; however, the Reynolds number shows it much weaker impact. It has also been found that the profile loss production is strongly influenced by both Reynolds and Mach numbers, being the impact of the incidence weaker. Finally, measured data suggest that, in order to properly reproduce the performance of these types of airfoils, annular cascades can be required as far as linear cascades may miss some essential flow features.

Engineering Extrapolation to Flight Reynolds Number for Supercritical Airfoil Pressure Distribution Based on CFD Results

2013 ◽  
Vol 444-445 ◽  
pp. 517-523
Author(s):  
Da Wei Liu ◽  
Xin Xu ◽  
Zhi Wei ◽  
De Hua Chen
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Pressure Distribution ◽  
Low Reynolds Number ◽  
Trailing Edge ◽  
Supercritical Airfoil ◽  
Short Period ◽  
Wind Tunnel Data ◽  
Mach Numbers ◽  
Low Reynolds

Pressure distribution of supercritical airfoil at flight Reynolds number could not be fully simulated except in cryogenic wind tunnel such as NTF (National Transonic Facility) and ETW (European Transonic Wind tunnel), which is costly and time resuming. This paper aimed to explore an engineering extrapolation to flight Reynolds number from low Reynolds number wind tunnel data for supercritical airfoil pressure distribution. However, the extrapolation method requiring plenty of data was investigated based on the CFD results for the reason of low cost and short period. Flows over a typical supercritical airfoil were numerically simulated by solving the two dimensional Navier-Stokes equations, with applications of ROE scheme spatial discretization and LU-SGS time march. Influence of computational grids convergence and turbulent models were investigated during the process of simulation. The supercritical airfoil pressure distribution were obtained with Reynolds numbers varied from 3.0×106to 30×106per airfoil chord, angles of attack from 0 degree to 6 degree and Mach numbers from 0.74 to 0.8. Simulated results indicated that weak shock existed on the upper surface of supercritical airfoil at cruise condition, that the shock location, shock strength and trailing edge pressure were dependent of Reynolds number, attack angles and Mach numbers. A similar parameter describing the Reynolds number effects factors was obtained by analyzing the relationship of shock wave location, shock front pressure and trailing edge pressure. Based on the similar parameter, airfoil pressure distribution at Reynolds number 30×106was obtained by extrapolation. It was shown that extrapolated result compared well with simulated result at Reynolds number 30×106, implying that the engineering method was at least promising applying to the extrapolation of low Reynolds number wind tunnel data.

Investigation of the Flow Mal-Distribution in Microchannels

2003 ◽  
Author(s):  
Jyh-Tong Teng ◽  
Jiann-Cherng Chu ◽  
Min-Sheng Liu ◽  
Chi-Chuan Wang ◽  
Ralph Greif
Keyword(s):  
Reynolds Number ◽  
Flow Rate ◽  
Test Results ◽  
Maximum Difference ◽  
Translational Velocity ◽  
Distribution Problem ◽  
Inlet Flow ◽  
Triangular Shape ◽  
Inlet Flow Rate ◽  
The Difference

This study examines the mal-distribution problem in microchannel manifolds. The tubes are of triangular shape with hydraulic diameter of 25 and 50 μm. Ranges of the Reynolds number are from 0.1 to 9. The test results indicate that the mal-distribution decreases with the rise of flow rate. For an inlet flow rate of 0.1 mL/min at the distributor inlet, the maximum difference of the translational velocity among manifolds is about 45%. The difference is reduced to 33% if the flow rate is increased to 0.153 mL/min. The maximum translational velocity inside the manifolds is located at the edge of the manifolds and the center portion has the smallest translational velocity. This is because of the spread and turn around water that helps to contribute the increase of flow rate nearby the edge.

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