Aerodynamic Characteristics of Supercritical Outlet Guide Vanes at Low Reynolds Number Conditions

2006 ◽  
Author(s):  
Toyotaka Sonoda ◽  
Heinz-Adolf Schreiber
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Guide Vane ◽  
Low Reynolds Number ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Critical Conditions ◽  
Flow Solver ◽  
Low Pressure Turbine ◽  
Low Reynolds

As a part of an innovative aerodynamic design concept for a single stage low pressure turbine, a high turning outlet guide vane is required to remove the swirl from the hot gas. The airfoil of the vane is a highly loaded compressor airfoil that has to operate at very low Reynolds numbers (Re ∼ 120,000). Recently published numerical design studies and experimental analysis on alternatively designed airfoils showed that blade profiles with an extreme front loaded pressure distribution are advantageous for low Reynolds number conditions. The advantage even holds true for an increased inlet Mach number at which the peak Mach number on the airfoils reaches and exceeds the critical conditions (Mss > 1.0). This paper discusses the effect of the inlet Mach number and Reynolds number on the cascade performance for both a controlled diffusion airfoil (CDA) (called baseline) and a numerically optimized front loaded airfoil. The results show that it is advantageous to design the profile with a fairly steep pressure gradient immediately at the front part in order to promote early transition or to prevent too large laminar — even shock induced — separations with the risk of a bubble burst. Profile Mach number distributions and wake traverse data are presented for design and off-design conditions. The discussion of Mach number distributions and boundary layer behavior is supported by numerical results obtained from the blade-to-blade flow solver MISES.

Aerodynamic Characteristics of Supercritical Outlet Guide Vanes at Low Reynolds Number Conditions

2006 ◽  
Vol 129 (4) ◽  
pp. 694-704 ◽  
Author(s):  
Toyotaka Sonoda ◽  
Heinz-Adolf Schreiber
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Guide Vane ◽  
Low Reynolds Number ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Critical Conditions ◽  
Flow Solver ◽  
Low Pressure Turbine ◽  
Low Reynolds

As a part of an innovative aerodynamic design concept for a single stage low pressure turbine, a high turning outlet guide vane is required to remove the swirl from the hot gas. The airfoil of the vane is a highly loaded compressor airfoil that has to operate at very low Reynolds numbers (Re∼120,000). Recently published numerical design studies and experimental analysis on alternatively designed airfoils showed that blade profiles with an extreme front loaded pressure distribution are advantageous for low Reynolds number conditions. The advantage even holds true for an increased inlet Mach number at which the peak Mach number on the airfoils reaches and exceeds the critical conditions (Mss>1.0). This paper discusses the effect of the inlet Mach number and Reynolds number on the cascade performance for both a controlled diffusion airfoil (CDA) (called baseline) and a numerically optimized front loaded airfoil. The results show that it is advantageous to design the profile with a fairly steep pressure gradient immediately at the front part in order to promote early transition or to prevent too large laminar—even shock induced—separations with the risk of a bubble burst. Profile Mach number distributions and wake traverse data are presented for design and off-design conditions. The discussion of Mach number distributions and boundary layer behavior is supported by numerical results obtained from the blade-to-blade flow solver MISES.

On High-Performance Airfoil at Very Low Reynolds Number

2016 ◽  
Vol 28 (3) ◽  
pp. 273-285
Author(s):  
Katsuya Hirata ◽  
◽  
Ryo Nozawa ◽  
Shogo Kondo ◽  
Kazuki Onishi ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Flat Plate ◽  
High Performance ◽  
Low Reynolds Number ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Slow Flow ◽  
Low Reynolds Numbers ◽  
Low Reynolds

[abstFig src='/00280003/02.jpg' width=""300"" text='Iso-Q surfaces of very-slow flow past an iNACA0015' ] The airfoil is often used as the elemental device for flying/swimming robots, determining its basic performances. However, most of the aerodynamic characteristics of the airfoil have been investigated at Reynolds numbers Re’s more than 106. On the other hand, our knowledge is not enough in low Reynolds-number ranges, in spite of the recent miniaturisation of robots. In the present study, referring to our previous findings (Hirata et al., 2011), we numerically examine three kinds of high-performance airfoils proposed for very-low Reynolds numbers; namely, an iNACA0015 (the NACA0015 placed back to front), an FPBi (a flat plate blended with iNACA0015 as its upper half) and an FPBN (a flat plate blended with the NACA0015 as its upper half), in comparison with such basic airfoils as a NACA0015 and an FP (a flat plate), at a Reynolds number Re = 1.0 × 102 using two- and three-dimensional computations. As a result, the FPBi shows the best performance among the five kinds of airfoils.

Advanced High Turning Compressor Airfoils for Low Reynolds Number Condition: Part 2 — Experimental and Numerical Analysis

2003 ◽  
Author(s):  
Heinz-Adolf Schreiber ◽  
Wolfgang Steinert ◽  
Toyotaka Sonoda ◽  
Toshiyuki Arima
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Guide Vane ◽  
Incidence Angle ◽  
Low Reynolds Number ◽  
Aerodynamic Characteristics ◽  
Low Loss ◽  
Design And Optimization ◽  
Negative Effect ◽  
Low Reynolds

Part 1 of this paper describes the design and optimization of two high turning subsonic compressor cascades operating as an outlet guide vane (OGV) behind a single stage low pressure turbine at low Reynolds number condition (Re = 1.3×105). In the numerical optimization algorithm, the design point and off-design performance has been considered in an objective function to achieve a wide low loss incidence range. The objective of the present paper is to examine some of the characteristics describing the new airfoils as well as to prove the reliability of the design process and the applied flow solver. Some aerodynamic characteristics for the two new airfoils and a conventional controlled diffusion airfoil (CDA), have been extensively investigated in the cascade wind tunnel of DLR Cologne. For an inlet Mach number of 0.6 the effect of Reynolds number and incidence angle on each airfoil performance is discussed, based on experimental and numerical results. For an interpretation of the airfoil boundary layer behavior, results of some boundary layer calculations are compared to oil flow visualization pictures. The design goal of an increased low loss incidence range at low Reynolds number condition could be confirmed without having a negative effect on the high Reynolds number region.

scholarly journals Aerodynamic characteristics of owl like airfoil at low reynolds number.

2022 ◽  
pp. 26-34
Author(s):  
Ishfaq Fayaz ◽  
Syeeda Needa Fathima ◽  
Y.D. Dwivedi
Keyword(s):  
Reynolds Number ◽  
Separation Bubble ◽  
Low Reynolds Number ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Pressure Side ◽  
Low Reynolds Numbers ◽  
Lift Curve ◽  
Low Reynolds

The computational investigation of aerodynamic characteristics and flow fields of a smooth owl-like airfoil without serrations and velvet structures.The bioinspired airfoil design is planned to serve as the main-wing for low-reynolds number aircrafts such as (MAV)micro air vechiles.The dependency of reynolds number on aerodynamics could be obtained at low reynolds numbers.The result of this experiment shows the owl-like airfoil is having high lift performance at very low speeds and in various wind conditions.One of the unique feature of owl airfoil is a separation bubble on the pressure side at low angle of attack.The separation bubble changes location from the pressure side to suction side as the AOA (angle of attack) increases. The reynolds number dependancy on the lift curve is insignificant,although there’s difference in drag curve at high angle of attacks.Eventually, we get the geometric features of the owl like airfoil to increase aerodynamic performance at low reynolds numbers.

Advanced High-Turning Compressor Airfoils for Low Reynolds Number Condition—Part II: Experimental and Numerical Analysis

2004 ◽  
Vol 126 (4) ◽  
pp. 482-492 ◽  
Author(s):  
Heinz-Adolf Schreiber ◽  
Wolfgang Steinert ◽  
Toyotaka Sonoda ◽  
Toshiyuki Arima
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Guide Vane ◽  
Incidence Angle ◽  
Low Reynolds Number ◽  
Aerodynamic Characteristics ◽  
Low Loss ◽  
Design And Optimization ◽  
Negative Effect ◽  
Low Reynolds

Part I of this paper describes the design and optimization of two high turning subsonic compressor cascades operating as an outlet guide vane (OGV) behind a single stage low pressure turbine at low Reynolds number condition Re=1.3×105. In the numerical optimization algorithm, the design point and off-design performance has been considered in an objective function to achieve a wide low loss incidence range. The objective of the present paper is to examine some of the characteristics describing the new airfoils as well as to prove the reliability of the design process and the applied flow solver. Some aerodynamic characteristics for the two new airfoils and a conventional controlled diffusion airfoil (CDA), have been extensively investigated in the cascade wind tunnel of DLR Cologne. For an inlet Mach number of 0.6 the effect of Reynolds number and incidence angle on each airfoil performance is discussed, based on experimental and numerical results. For an interpretation of the airfoil boundary layer behavior, results of some boundary layer calculations are compared to oil flow visualization pictures. The design goal of an increased low loss incidence range at low Reynolds number condition could be confirmed without having a negative effect on the high Reynolds number region.

Effects of periodic wakes on the endwall secondary flow in high-lift low-pressure turbine cascades at low Reynolds numbers

2017 ◽  
Vol 233 (1) ◽  
pp. 354-368 ◽  
Author(s):  
Xiao Qu ◽  
Yanfeng Zhang ◽  
Xingen Lu ◽  
Ge Han ◽  
Ziliang Li ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Secondary Flow ◽  
Low Reynolds Number ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Low Reynolds ◽  
High Reynolds

Periodic wakes affect not only the surface boundary layer characteristics of low-pressure turbine blades and profile losses but also the vortex structures of the secondary flow and the corresponding losses. Thus, understanding the physical mechanisms of unsteady interactions and the potential to eliminate secondary losses is becoming increasingly important for improving the performance of high-lift low-pressure turbines. However, few studies have focused on the unsteady interaction mechanism between periodic wakes and endwall secondary flow in low-pressure turbines. This paper verified the accuracy of computational fluid dynamics by comparing experimental results and those of the numerical predictions by taking a high-lift low-pressure turbine cascade as the research object. Discussion was focused on the interaction mechanisms between the upstream wakes and secondary flow within the high-lift low-pressure turbine. The results indicated that upstream wakes have both positive and negative effects on the endwall flow, where the periodic wakes can decrease significantly the size of the separation bubble, prevent the formation of secondary vorticity structures at relatively high Reynolds numbers (100,000 and 150,000), and reduce the cross-passage pressure gradient of cascade. In addition, periodic wakes can improve the cascade incidence characteristic in terms of reducing the overturning and underturning of the secondary flow at downstream of the cascade all of which are beneficial for decreasing the endwall secondary losses, whereas more endwall boundary layer is involved in the main flow passage due to the wake transport, resulting in increased strength of the secondary flow at low Reynolds number of 25,000 and 50,000. Compared with the results without wakes, the total pressure loss for unsteady condition at the cascade exit decreases by 2.7% and 6.1% at high Reynolds number of 100,000 and 150,000, respectively. However, the secondary loss at unsteady flow conditions increases at low Reynolds number of 25,000 and 50,000.

scholarly journals Simulation of Gas Flow Over a Micro Cylinder

2009 ◽  
Author(s):  
Yuan Hu ◽  
Quanhua Sun ◽  
Jing Fan
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Drag Coefficient ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Low Reynolds Number ◽  
Pressure Drag ◽  
Low Reynolds ◽  
Rarefied Gas Effect ◽  
Gas Effect

Gas flow over a micro cylinder is simulated using both a compressible Navier-Stokes solver and a hybrid continuum/particle approach. The micro cylinder flow has low Reynolds number because of the small length scale and the low speed, which also indicates that the rarefied gas effect exists in the flow. A cylinder having a diameter of 20 microns is simulated under several flow conditions where the Reynolds number ranges from 2 to 50 and the Mach number varies from 0.1 to 0.8. It is found that the low Reynolds number flow can be compressible even when the Mach number is less than 0.3, and the drag coefficient of the cylinder increases when the Reynolds number decreases. The compressible effect will increase the pressure drag coefficient although the friction coefficient remains nearly unchanged. The rarefied gas effect will reduce both the friction and pressure drag coefficients, and the vortex in the flow may be shrunk or even disappear.

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