Experimental Investigation Into Unsteady Effects on Film Cooling

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Richard J. Fawcett ◽  
Andrew P. S. Wheeler ◽  
Li He ◽  
Rupert Taylor
Keyword(s):  
Film Cooling ◽  
High Speed ◽  
Particle Image ◽  
High Speed Photography ◽  
Velocity Difference ◽  
Cooling Flows ◽  
Blowing Ratio ◽  
Image Velocimetry ◽  
Mainstream Flow ◽  
Unsteady Effects

The benefits of different film cooling geometries are typically assessed in terms of their time-averaged performance. It is known that the mixing between the coolant film and the main turbine passage flow is an unsteady process. The current study investigates the forms of unsteadiness that occur in engine-representative film cooling flows and how this unsteadiness affects the mixing with the mainstream flow. Cylindrical and fan-shaped cooling holes across a range of hole blowing ratios have been studied experimentally using particle image velocimetry and high speed photography. Coherent unsteadiness is found in the shear layer between the jet and the mainstream for both cylindrical and fan-shaped cooling holes. Its occurrence and sense of rotation is found to be controlled by the velocity difference between the mainstream flow and the jet, which is largely determined by the blowing ratio.

Experimental Investigation Into Unsteady Effects on Film Cooling

2010 ◽  
Author(s):  
Richard J. Fawcett ◽  
Andrew P. S. Wheeler ◽  
Li He ◽  
Rupert Taylor
Keyword(s):  
Film Cooling ◽  
High Speed ◽  
Particle Image ◽  
High Speed Photography ◽  
Velocity Difference ◽  
Cooling Flows ◽  
Blowing Ratio ◽  
Image Velocimetry ◽  
Mainstream Flow ◽  
Unsteady Effects

The benefits of different film cooling geometries are typically assessed in terms of their time averaged performance. It is known that the mixing between the coolant film and the main turbine passage flow is an unsteady process. The current study investigates the forms of unsteadiness which occur in engine-representative film cooling flows, and how this unsteadiness affects the mixing with the mainstream flow. Cylindrical and fan-shaped cooling holes across a range of hole blowing ratios have been studied experimentally using Particle Image Velocimetry and High Speed Photography. Coherent unsteadiness is found in the shear layer between the jet and the mainstream, for both cylindrical and fan-shaped cooling holes. Its occurrence and sense of rotation is found to be controlled by the velocity difference between the mainstream flow and the jet which is largely determined by the blowing ratio.

Experimental Investigation Into the Impact of Crossflow on the Coherent Unsteadiness Within Film Cooling Flows

2011 ◽  
Author(s):  
Richard J. Fawcett ◽  
Andrew P. S. Wheeler ◽  
Li He ◽  
Rupert Taylor
Keyword(s):  
Film Cooling ◽  
High Speed ◽  
High Speed Photography ◽  
Cooling Flows ◽  
Pressure Surface ◽  
Cooling Flow ◽  
Cooling Hole ◽  
Crossflow Velocity ◽  
The Impact ◽  
First Time

It is known that the mixing of a film cooling flow with the main turbine passage flow is an unsteady process, with coherent unsteady features occurring across a range of blowing ratios. Upon an aero engine the cooling holes on a turbine blade commonly have a crossflow at the hole inlet. Previous work has shown that crossflow at the hole inlet modifies the time-mean flowfield downstream of a cooling hole compared to the case without crossflow. The current paper investigates the impact of spanwise orientated crossflow on the coherent unsteadiness within film cooling flows. Both cylindrical and fan-shaped holes, located on a blade pressure surface, are studied. The range of blowing ratios considered is 0.7 to 1.8 and the crossflow velocity is up to 0.8 times the bulk jet velocity. High Speed Photography and Hot Wire Anemometry are used to observe the presence of coherent unsteadiness, both immediately downstream of the hole exit and within the cooling hole tube. The results show that the coherent unsteadiness downstream of the hole exit is persistent and its occurrence is not significantly affected by the magnitude of spanwise crossflow. Within the cooling hole tube the existence of coherent unsteadiness is presented for the first time, inside both cylindrical and fan-shaped holes, with a Strouhal number of 0.6 to 0.8. The pattern of this in-hole coherent unsteadiness is seen to change with increasing the crossflow velocity.

A Study of Hydraulic Characteristics of Multi-Square-Hole Orifice Plates

2012 ◽  
Vol 256-259 ◽  
pp. 2470-2473 ◽  
Author(s):  
Zhi Yong Dong ◽  
Yong Gang Yang ◽  
Qi Qi Chen ◽  
Bin Shi
Keyword(s):  
High Speed ◽  
Particle Image ◽  
Three Dimensional ◽  
Hydrodynamic Cavitation ◽  
High Speed Photography ◽  
Hydraulic Characteristics ◽  
System Pressure ◽  
Image Velocimetry ◽  
Working Section ◽  
Square Hole

This paper experimentally investigated hydraulic characteristics in working section of multi-square-hole orifice plates of hydrodynamic cavitation reactor by use of three-dimensional Particle Image Velocimetry (PIV) and High Speed Photography etc. Arrangements of holes in the orifice plates can be divided into diagonal, cross and checkerboard categories. The three-dimensional velocity distribution, pressure and cavitation characteristics for each arrangement of multi-hole orifice plates were measured by PIV system, pressure data acquisition system and high speed camera, and a comparison of hydraulic characteristics of the three categories of arrangements of the multi-hole orifice plates were made.

Hydraulic Balance Ring Study and Design Using Optical Techniques

2011 ◽  
Author(s):  
Alfonso Thompson-Salinas ◽  
Martin Ortega-Bren˜a ◽  
Manuel H. De la Torre-Ibarra ◽  
Bernardino Barrientos-Garci´a ◽  
Victor J. Gonzalez-Villela
Keyword(s):  
Particle Image Velocimetry ◽  
High Speed ◽  
Particle Image ◽  
High Speed Photography ◽  
Washing Machine ◽  
Optical Techniques ◽  
New Approach ◽  
Image Velocimetry ◽  
Hydraulic Balance ◽  
Velocity Field Measurement

A new approach to understand factors that affect self-balancing devices is proposed. Experimentation was conducted to determine the influence of different factors on the performance of an automatic washing machine hydraulic balance ring fluid during transient and steady states. Two different optical techniques were used: one for visualization (high-speed photography) and another for velocity field measurement (Particle Image Velocimetry, PIV). Results were used to build a new balancer design and compared with previous findings. Important factors in balancer design were deducted.

Experimental Flow-Field Investigations Downstream a Scaled-Up Micro-Tangential-Jet Scheme Using the Particle Image Velocimetry Technique

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Othman Hassan ◽  
Ibrahim Hassan
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Field ◽  
Film Cooling ◽  
Particle Image ◽  
Material Strength ◽  
Main Stream ◽  
Base Line ◽  
Blowing Ratio ◽  
Image Velocimetry ◽  
Flow Field Characteristics

This paper presents experimental investigations of the flow-field characteristics downstream a Scaled-Up Micro-Tangential-Jet (SUMTJ) film-cooling scheme using the particle image velocimetry (PIV) technique over a flat plate. The SUMTJ scheme is a shaped scheme designed so that the secondary jet is supplied tangentially to the surface. The scheme combines the thermal benefits of tangential injection and the enhanced material strength of discrete holes’ schemes compared with continuous slot schemes. The flow-field characteristics downstream one row of holes were investigated at three blowing ratios, 0.5, 1.0, and 1.5, and were calculated based on the scheme exit area. A density ratio of unity, a Reynolds number of 1.16 × 105, and an average turbulence intensity of 8% were used throughout the investigations. The performance of the SUMTJ scheme was compared to that of the circular hole scheme, base line case case, at the same test conditions and blowing ratios. From the investigations, it was noticeable that the SUMTJ scheme jet stays attached to the surface for long downstream distances at all investigated blowing ratios. Moreover, the lateral expansion angles of the scheme help perform a continuous film from adjacent jets close to the schemes’ exits; however, they have a negative impact on the uniformity of the film thickness in the lateral direction. The vorticity strength downstream the SUMTJ scheme in the y-z plane was much less than the vorticity strength downstream the circular scheme at all blowing ratios. However, the vorticity behavior in the shear layer between the secondary SUMTJ scheme jet and the main stream was changing dramatically with the blowing ratio. The latter is expected to have a significant impact on the film-cooling performance as the blowing ratio increases.

scholarly journals Aerodynamics of manoeuvring flight in brown long-eared bats ( Plecotus auritus )

2018 ◽  
Vol 15 (148) ◽  
pp. 20180441 ◽  
Author(s):  
Per Henningsson ◽  
Lasse Jakobsen ◽  
Anders Hedenström
Keyword(s):  
Particle Image Velocimetry ◽  
Wind Tunnel ◽  
High Speed ◽  
Particle Image ◽  
Future Studies ◽  
Image Velocimetry ◽  
Mechanistic Basis

In this study, we explicitly examine the aerodynamics of manoeuvring flight in animals. We studied brown long-eared bats flying in a wind tunnel while performing basic sideways manoeuvres. We used particle image velocimetry in combination with high-speed filming to link aerodynamics and kinematics to understand the mechanistic basis of manoeuvres. We predicted that the bats would primarily use the downstroke to generate the asymmetries for the manoeuvre since it has been shown previously that the majority of forces are generated during this phase of the wingbeat. We found instead that the bats more often used the upstroke than they used the downstroke for this. We also found that the bats used both drag/thrust-based and lift-based asymmetries to perform the manoeuvre and that they even frequently switch between these within the course of a manoeuvre. We conclude that the bats used three main modes: lift asymmetries during downstroke, thrust/drag asymmetries during downstroke and thrust/drag asymmetries during upstroke. For future studies, we hypothesize that lift asymmetries are used for fast turns and thrust/drag for slow turns and that the choice between up- and downstroke depends on the timing of when the bat needs to generate asymmetries.

scholarly journals Dual-camera system for high-speed imaging in particle image velocimetry

2012 ◽  
Vol 15 (3) ◽  
pp. 193-195 ◽  
Author(s):  
K. Hashimoto ◽  
A. Hori ◽  
T. Hara ◽  
S. Onogi ◽  
H. Mouri
Keyword(s):  
Particle Image Velocimetry ◽  
High Speed ◽  
Particle Image ◽  
High Speed Imaging ◽  
Camera System ◽  
Image Velocimetry
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