This experimental study focuses on fluid-structure interaction (FSI) for a thin compliant panel under a shock/boundary layer interaction (SBLI) generated by a 2D compression ramp in a Mach 2 wind tunnel. In previous work, we have studied the FSI for this configuration using simultaneous fast-response pressure-sensitive paint (PSP) and digital image correlation (DIC). Simultaneous PSP/DIC allows for examination of the relationship between the dynamic panel displacement and surface pressure loading, respectively. Spectral analysis showed that pressure fluctuations within the interaction region and shock-foot unsteadiness tend to lock to the first mode resonant frequency of the compliant panel. The current study aims to utilize synchronous high-speed stereoscopic PIV (25 kHz) and DIC (5 kHz) techniques to better understand the coupling between the flow field and the panel displacement field. The PIV is obtained in a streamwise-spanwise plane located at 15% of the boundary layer height. Thin compliant polycarbonate panel with thicknesses of 1 mm is utilized, which has a first-mode vibrational frequency of 407 Hz. The 1 mm panel out-of-plane displacement amplitude was up to 15% of the boundary layer thickness. The analysis includes low-pass and band-pass filtering of the velocity data, including the surrogate separation line, and cross-correlation analysis betweenmore »
20 kHz dual-plane stereo-PIV measurements on a swirling flame using a two-legged burst-mode laser
Dual-plane stereoscopic particle image velocimetry (PIV) is capable of quantifying the flow field in terms of three-component (3C) flow vectors and 3C vorticity vectors simultaneously. Here, we present a test rig to carry out the 20 kHz dual-plane stereo PIV measurements on a premixed swirling flame by using a two-legged burst-mode laser. Other than the traditional methods employing the laser polarization direction and the two-color separation methods, two same-color laser sheets with a 100 ns delay were adopted to separate the imaging processes for the two pairs of cameras using the image straddling method. Each laser sheet with the same wavelength of 532 nm has a pulse cyclic frequency of 20 kHz within each burst generated by the high-repetition-rate burst-mode laser. 3C velocity vectors of a swirling flame were obtained based on the sequential particle images for each laser sheet. In spite of non-perfect simultaneous flow measurements on the two spatially separated laser sheets, the velocity error caused by the 100 ns delay on top of a 50 μs duration, which was used for the velocity vector calculation, is negligible. This short-delay separation method significantly simplifies the experimental setup for dual-plane stereo PIV measurements, especially for low-speed flows.
- Publication Date:
- NSF-PAR ID:
- 10197763
- Journal Name:
- Optics Letters
- Volume:
- 45
- Issue:
- 20
- Page Range or eLocation-ID:
- Article No. 5756
- ISSN:
- 0146-9592; OPLEDP
- Publisher:
- Optical Society of America
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Many industrial combustion systems, especially power generation gas turbines, use fuel-lean combustion to reduce NOx emissions. However, these systems are highly susceptible to combustion instability, the coupling between combustor acoustics and heat release rate oscillations of the flame. It has been shown in previous work by the authors that a precessing vortex core (PVC) can suppress shear layer receptivity to external perturbations, reducing the potential for thermoacoustic coupling. The goal of this study is to understand the effect of combustor exit boundary condition on the flow structure of a swirling jet to increase fundamental understanding of how combustor design impacts PVC dynamics. The swirling jet is generated with a radial-entry, variable-angle swirler, and a quartz cylinder is fixed on the dump plane for confinement. Combustor exit constriction plates of different diameters are used to determine the impact of exit boundary condition on the flow field. Particle image velocimetry (PIV) is used to capture the velocity field inside the combustor. Spectral proper orthogonal decomposition, a frequency-resolved eigenvalue decomposition that can identify energetic structures in the flow, is implemented to identify the PVC at each condition in both energy and frequency space. We find that exit boundary diameter affects both the structuremore »
-
Combustion instability, which is the result of a coupling between combustor acoustic modes and unsteady flame heat release rate, is a severely limiting factor in the operability and performance of modern gas turbine engines. This coupling can occur through different coupling pathways, such as flow field fluctuations or equivalence ratio fluctuations. In realistic combustor systems, there are complex hydrodynamic and thermo-chemical processes involved, which can lead to multiple coupling pathways. In order to understand and predict the mechanisms that govern the onset of combustion instability in real gas turbine engines, we consider the influences that each of these coupling pathways can have on the stability and dynamics of a partially-premixed, swirl-stabilized flame. In this study, we use a model gas turbine combustor with two concentric swirling nozzles of air, separated by a ring of fuel injectors, operating at an elevated pressure of 5 bar. The flow split between the two streams is systematically varied to observe the impact on the flow and flame dynamics. High-speed stereoscopic particle image velocimetry, OH planar laser-induced fluorescence, and acetone planar laser-induced fluorescence are used to obtain information about the velocity field, flame, and fuel-flow behavior, respectively. Depending on the flow conditions, a thermoacoustic oscillationmore »
-
Abstract Combustion instability, which is the result of a coupling between combustor acoustic modes and unsteady flame heat release rate, is a severely limiting factor in the operability and performance of modern gas turbine engines. This coupling can occur through different pathways, such as flow-field fluctuations or equivalence ratio fluctuations. In realistic combustor systems, there are complex hydrodynamic and thermo-chemical processes involved, which can lead to multiple coupling pathways. In order to understand and predict the mechanisms that govern the onset of combustion instability in real gas turbine engines, we consider the influences that each of these coupling pathways can have on the stability and dynamics of a partially premixed, swirl-stabilized flame. In this study, we use a model gas turbine combustor with two concentric swirling nozzles of air, separated by a ring of fuel injectors, operating at an elevated pressure of 5 bar. The flow split between the two streams is systematically varied to observe the impact on the flow and flame dynamics. High-speed stereoscopic particle image velocimetry, OH planar laser-induced fluorescence, and acetone planar laser-induced fluorescence are used to obtain information about the velocity field, flame, and fuel-flow behavior, respectively. Depending on the flow conditions, a thermoacoustic oscillation modemore »
-
A novel, double hole film cooling configuration is investigated as an alternative to traditional cylindrical and fanshaped, laidback holes. This experimental investigation utilizes a Stereo-Particle Image Velocimetry (S-PIV) to quantitatively assess the ability of the proposed, double hole geometry to weaken or mitigate the counter-rotating vortices formed within the jet structure. The three-dimensional flow field measurements are combined with surface film cooling effectiveness measurements obtained using Pressure Sensitive Paint (PSP). The double hole geometry consists of two compound angle holes. The inclination of each hole is = 35°, and the compound angle of the holes is = ± 45° (with the holes angled toward one another). The simple angle cylindrical and shaped holes both have an inclination angle of = 35°. The blowing ratio is varied from M = 0.5 to 1.5 for all three film cooling geometries while the density ratio is maintained at DR = 1.0. Time averaged velocity distributions are obtained for both the mainstream and coolant flows at five streamwise planes across the fluid domain (x/d = -4, 0, 1, 5, and 10). These transverse velocity distributions are combined with the detailed film cooling effectiveness distributions on the surface to evaluate the proposedmore »
