Vortices inside a single-stage axial air turbine captured by Particle Image Velocimetry

Daniel Duda,Václav Uruba,Pavel Žitek,Vitalii Yanovych,Martin Němec

doi:10.1051/matecconf/202032805002

Abstract

Particle Image Velocimetry (PIV) is an experimental method of fluid research resulting into a spatially resolved two-dimensional velocity field. We measured the velocity inside a single-stage axial test turbine at the Czech Aerospace Research Centre. We studied the axial × tangential plane just behind the rotor wheel at the tip radius under three regimes: underloaded, designed and overloaded ones. We found individual vortices in the instantaneous snapshots and we analyze their properties statistically.

Highlights

Vortex is a coherent structure typical for turbulent flows [1]
In this article we look at the vortices past a such rotor wheel, where the flow is influenced by the preceding stator wheel as well
This image pair is processed via the method “Adaptive Particle Image Velocimetry (PIV)” inside the “Dantec Dynamic Studio” software resulting into an ensemble of instantaneous velocity fields of two velocity components: the axial one denoted u and the tangential one denoted v

Summary

Introduction

Vortex is a coherent structure typical for turbulent flows [1]. Coherent relates to the motion state of macroscopic number of molecules with motion state correlated over a very large distance (in compared with molecular scale). It is not possible to count the number of molecules which the vortex consists of, because (i) the vortex influences an infinite area in an infinite fluid domain and (ii) there are always more vortices influencing the single molecule, and (iii) the vortex itself contains other vortices [3] It carries the energy, it has a finite life-time, it moves through the fluid with some non-zero velocity relative to the surrounding fluid transporting energy and momentum. The mechanical energy is “lost” to be born downstream in the form of heat This mechanism is called Richardson cascade [4] and the conservation of energy rate flowing through scales leads to the famous Kolmogorov k-5/3 law [5]. In this article we look at the vortices past a such rotor wheel, where the flow is influenced by the preceding stator wheel as well

Experiment

Data processing

Searching individual vortices

Conclusion