Experimental and computational investigations of flow dynamics in LPP combustor

2017 ◽  
Vol 121 (1240) ◽  
pp. 790-802 ◽  
Author(s):  
Y. W. YAN ◽  
Y. P. Liu ◽  
Y. C. Liu ◽  
J. H. Li
Keyword(s):  
Recirculation Zone ◽  
Swirling Flow ◽  
Mixing Layer ◽  
Experimental Tests ◽  
Flow Dynamics ◽  
Reynolds Stresses ◽  
Lean Combustion ◽  
Low Emission ◽  
Image Velocimetry ◽  
Combustion Technology

ABSTRACTA Lean Premixed Prevaporised (LPP) low-emission combustor with a staged lean combustion technology was developed. In order to study cold-flow dynamics in the LPP combustor, both experimental tests using the particle image velocimetry (PIV) to quantify the flow dynamics and numerical simulation using the commercial software (FLUENT) were conducted, respectively. Numerical results were in good agreement with the experimental data. It is shown from the observation of the results that: there is a Primary Recirculation Zone (PRZ), a Corner Recirculation Zone (CRZ) and a Lip Recirculation Zone (LRZ) in the LPP combustor, and the exchanges of mass, momentum and energy between pilot swirling flow and primary swirling flow are contributed by the velocity gradients, and the shear flow is transformed into a mixing layer exhibiting the higher Reynolds stresses, which suggests the mixing process is strictly affected by the Reynolds stresses.

scholarly journals Investigation of unsteady combustion of methane-air flame in a model combustion chamber with swirling flow

2021 ◽  
Vol 2119 (1) ◽  
pp. 012015
Author(s):  
A S Lobasov
Keyword(s):  
Combustion Chamber ◽  
Large Scale ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Heating Temperature ◽  
Combustion Products ◽  
Flow Dynamics ◽  
Unsteady Combustion ◽  
Stereoscopic Piv ◽  
Large Scale Vortex

Abstract The present paper reports on the investigation of unsteady combustion of a methane-air mixture, including combustion at increased pressure in the combustion chamber and increased temperature of mixture heating for a model gas-turbine swirl burner based on a design by Turbomeca. To measure the velocity and OH fluorescence fields in the flows a combination of stereoscopic PIV and acetone PLIF systems is used. In all cases, the flow dynamics is associated with the movement of large-scale vortex structures in the inner and outer mixing layers and the flow structure corresponds to a swirling jet with a central recirculation zone containing combustion products. An increase in the heating temperature of the mixture and pressure in the combustion chamber leads to a periodic partial separation of the flame from the model swirl nozzle. However, the flow of fuel through the central channel will stabilize the flame.

Turbulent Combustion Properties Behind a Confined Conical Stabilizer

1992 ◽  
Vol 114 (1) ◽  
pp. 33-38 ◽  
Author(s):  
J. C. Pan ◽  
W. J. Schmoll ◽  
D. R. Ballal
Keyword(s):  
Recirculation Zone ◽  
Mixing Layer ◽  
Turbulent Heat Flux ◽  
Turbulent Heat ◽  
Reynolds Stresses ◽  
Streamline Curvature ◽  
Gradient Diffusion ◽  
Combustion Properties ◽  
Strain Interaction ◽  
Mean Strain

Turbulence properties were investigated in and around the recirculation zone produced by a 45 deg conical flame stabilizer of 25 percent blockage ratio confined in a pipe supplied with a turbulent premixed methane-air mixture at a Reynolds number of 5.7×104. A three-component LDA system was used for measuring mean velocities, turbulence intensities, Reynolds stresses, skewness, kurtosis, and turbulent kinetic energy. It was found that wall confinement elongates the recirculation zone by accelerating the flow and narrows it by preventing mean streamline curvature. For confined flames, turbulence production is mainly due to shear stress-mean strain interaction. In the region of maximum recirculation zone width and around the stagnation point, the outer stretched flame resembles a normal mixing layer and gradient-diffusion closure for velocity holds. However, and in the absence of turbulent heat flux data, countergradient diffusion cannot be ruled out. Finally, and because of the suppression of mean streamline curvature by confinement, in combusting flow, the production of turbulence is only up to 33 percent of its damping due to dilatation and dissipation.

scholarly journals PIV of Swirling Flow in a Conical Pipe with Vibrating Wall

2018 ◽  
Vol 10 (02) ◽  
pp. 1850022 ◽  
Author(s):  
Yan Xu ◽  
Yan-Yue Zhang ◽  
Franck C. G. A. Nicolleau ◽  
Zun-Ce Wang
Keyword(s):  
Particle Image ◽  
Swirling Flow ◽  
Water Channel ◽  
Swirling Flows ◽  
Industrial Processes ◽  
Reynolds Stresses ◽  
Pipe Flows ◽  
Velocity Statistics ◽  
Image Velocimetry ◽  
The Mean

Swirling flows in conical pipe can be found in a number of industrial processes, such as hydrocyclone, separator and rotating machinery. It has been found that wall oscillations can reduce the drag in water channel and pipe flows, but there is no study of a swirling flow combined with a vibrating wall in conical pipes, though there are many applications of such combination in engineering processes. A two-dimensional particle image velocimetry (PIV) is used to measure the swirling flow field in a water conical pipe subjected to a periodic vibrating wall for a Reynolds number 3800. The flow velocity statistics are studied under different vibration frequencies corresponding to Strouhal numbers from 60 to 242. The instantaneous axial and vertical velocity in one vibrating period, the mean velocities, and Reynolds stresses were obtained. The results show the existence of an intermediary recirculation cell in the middle of the pipe. They also show that the vibration improves the symmetry for the swirling flow while decreasing dramatically the velocity fluctuation.

Experimental Study on Flow Structure of Non-Premixed Swirl Burner Flows Using PIV

2011 ◽  
Vol 347-353 ◽  
pp. 2587-2592 ◽  
Author(s):  
Bing Ge ◽  
Shu Sheng Zang ◽  
Pei Qing Guo
Keyword(s):  
Flow Field ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Spatial Separation ◽  
Complex Flow ◽  
Image Velocimetry ◽  
Characteristic Modes ◽  
Swirling Flame ◽  
Development And Validation ◽  
Annular Jets

This paper focuses on investigating the characteristic modes and structures in non-premixed swirling methane/air flames. Using the Particle Image Velocimetry (PIV) technique, the experiment measured the velocity distributions of the swirling flame. Cold flow conditions have been included to provide a picture of the flow field and to demonstrate the modifications induced by combustion. The characteristic lengths, velocity vectors, streamlines, and velocity distributions are presented and discussed. The experiment shows that a large spatial separation at the exit between the central and swirling annular jets can expedite the formation of a recirculation zone. Complex flow structures are found in the recirculation zone. Moreover, the differences between cold swirling flow field and combustion swirling flow are analyzed at length. The data from this experiment is helpful for optimization of the non-premixed burner design, and can be established as benchmarks for the development and validation of combustion numerical simulations.

scholarly journals Experimental and Numerical Study of Swirling Flows and Flame Dynamics

2014 ◽  
Vol 51 (4) ◽  
pp. 25-40 ◽  
Author(s):  
M. Abricka ◽  
I. Barmina ◽  
R. Valdmanis ◽  
M. Zake
Keyword(s):  
Recirculation Zone ◽  
Swirling Flow ◽  
Numerical Study ◽  
Chemical Conversion ◽  
Reacting Flows ◽  
Flow Dynamics ◽  
Combustion Stability ◽  
Complex Flow ◽  
Air Jet ◽  
Air Supply

Abstract The effect of swirling air on the flow dynamics was investigated for the cold non-reacting flows and the flame arising at thermo-chemical conversion of biomass pellets downstream of a cylindrical channel. Under experimental and numerical investigation was the swirling flow dynamics with the primary axial air supply below a biomass layer and swirling air supply above it. The results indicate that for cold flows the swirling air jet outflow from tangential nozzles leads to the formation of a complex flow dynamics which is influenced both by upstream and downstream air swirl propagation near the channel walls, with correlating swirl-enhanced formation of the upstream and downstream axial flows close to the flow centreline depending on the swirling air supply rate. These axial flows can be completely balanced at their stagnation within the axial recirculation zone. It is shown that at equal boundary conditions for the swirling flame and the cold flows the swirling flow dynamics is influenced by the upstream air swirl-enhanced mixing of the reactants below the air swirl nozzles. This determines the formation of a downstream reaction zone with correlating development of the flow velocity, temperature and composition profiles in the downstream flame regions with improved combustion stability. The low swirl intensity in these regions prevents the formation of a recirculation zone

Flow Dynamics in a Multiswirler Model Combustor Based on Large Eddy Simulation and Proper Orthogonal Decomposition Analysis

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Weijie Liu ◽  
Huiru Wang ◽  
Qian Yang ◽  
Ranran Xue ◽  
Bing Ge ◽  
...  
Keyword(s):  
Coherent Structures ◽  
Particle Image ◽  
Swirling Flow ◽  
Flow Instability ◽  
Flow Dynamics ◽  
Main Stage ◽  
Eddy Simulation ◽  
Image Velocimetry ◽  
Large Eddy ◽  
Proper Orthogonal

Abstract Swirling flow is often employed in gas turbine combustion chambers for the sake of improving flame stability. Swirling flow induces not only recirculation zones but also large coherent structures, which show close relationship with flow dynamics and combustion instability. The flow dynamics including precessing vortex core (PVC) in simple swirlers is extensively studied, while the flow instability characteristics in a multiswirler combustor are not fully reported. In this paper, large eddy simulation (LES) of nonreacting turbulent swirling flow is conducted in a multiswirler burner, which comprises a pilot stage and a main stage. Flow dynamics in the multiswirler combustor are analyzed based on phase-averaged evolution of instantaneous flowfield. LES results are compared with particle image velocimetry (PIV) data in terms of mean and root mean square (RMS) velocities. Proper orthogonal decomposition (POD) is employed to identify the coherent structures in the multiswirling flow. Results show that LES results are in good agreement with particle image velocimetry (PIV) data. Main stage and pilot stage flow interact with each other generating highly turbulent swirling flow. PVC is successfully captured at the boundary of main recirculation zone (MRZ) in the pilot stage with a dominant frequency of 1915 Hz. The PVC leads to periodic azimuthal flow instability. POD analyses for the velocity fields show dominant high-frequency modes (modes 1 and 2) in the pilot stage. However, the dominant energetic flow is damped rapidly downstream of the pilot stage that it has little effect on the main stage flow.

scholarly journals Turbulent Combustion Properties Behind a Confined Conical Stabilizer

1990 ◽  
Author(s):  
J. C. Pan ◽  
W. J. Schmoll ◽  
D. R. Ballal
Keyword(s):  
Recirculation Zone ◽  
Mixing Layer ◽  
Turbulent Heat Flux ◽  
Turbulent Heat ◽  
Reynolds Stresses ◽  
Streamline Curvature ◽  
Gradient Diffusion ◽  
Combustion Properties ◽  
Strain Interaction ◽  
Mean Strain

Turbulence properties were investigated in and around the recirculation zone produced by a 45° conical flame stabilizer of 25% blockage ratio confined in a pipe supplied with a turbulent premixed methane-air mixture at a Reynolds number of 5.7 × 104. A three-component LDA system was used for measuring mean velocities, turbulence intensities, Reynolds stresses, skewness, kurtosis, and turbulent kinetic energy. It was found that wall confinement elongates the recirculation zone by accelerating the flow and narrows it by preventing mean streamline curvature. For confined flames, turbulence production is mainly due to shear stress-mean strain interaction. In the region of maximum recirculation zone width and around the stagnation point, the outer stretched flame resembles a normal mixing layer and gradient-diffusion closure for velocity holds. However, and in the absence of turbulent heat flux data, counter-gradient diffusion cannot be ruled out. Finally, and because of the suppression of mean streamline curvature by confinement, in combusting flow, the production of turbulence is only up to 33% of its damping due to dilatation and dissipation.

Experimental investigation of the influence of the hydraulic performance of an axial blood pump on intraventricular blood flow

2021 ◽  
pp. 039139882110130
Author(s):  
Guang-Mao Liu ◽  
Fu-Qing Jiang ◽  
Xiao-Han Yang ◽  
Run-Jie Wei ◽  
Sheng-Shou Hu
Keyword(s):  
Blood Flow ◽  
Particle Image ◽  
Swirling Flow ◽  
Blood Stasis ◽  
Systemic Circulation ◽  
Operating Conditions ◽  
Blood Pump ◽  
Image Velocimetry ◽  
Ct Data

Blood flow inside the left ventricle (LV) is a concern for blood pump use and contributes to ventricle suction and thromboembolic events. However, few studies have examined blood flow inside the LV after a blood pump was implanted. In this study, in vitro experiments were conducted to emulate the intraventricular blood flow, such as blood flow velocity, the distribution of streamlines, vorticity and the standard deviation of velocity inside the LV during axial blood pump support. A silicone LV reconstructed from computerized tomography (CT) data of a heart failure patient was incorporated into a mock circulatory loop (MCL) to simulate human systemic circulation. Then, the blood flow inside the ventricle was examined by particle image velocimetry (PIV) equipment. The results showed that the operating conditions of the axial blood pump influenced flow patterns within the LV and areas of potential blood stasis, and the intraventricular swirling flow was altered with blood pump support. The presence of vorticity in the LV from the thoracic aorta to the heart apex can provide thorough washing of the LV cavity. The gradually extending stasis region in the central LV with increasing blood pump support is necessary to reduce the thrombosis potential in the LV.

Odour and VOC confining in large enclosures using air curtains

2001 ◽  
Vol 44 (9) ◽  
pp. 165-171 ◽  
Author(s):  
M. Pavageau ◽  
E.M. Nieto ◽  
C. Rey
Keyword(s):  
Particle Image ◽  
Flow Dynamics ◽  
Leakage Flow ◽  
Experimental Facility ◽  
Tracer Gas ◽  
Air Curtain ◽  
Air Supply ◽  
Leakage Flow Rate ◽  
Image Velocimetry ◽  
Air Tightness

Experiments were conducted on a two stream air-curtain prototype designed for VOC and odour confinement in a truck unloading area. The emphasis was placed on the air supply device. Measurements using tracer gas techniques were performed to assess the effectiveness of the system in terms of air tightness. Leakage flow rate was estimated for various feeding arrangements. Flow visualisations and particle image velocimetry measurements were carried out for a better understanding of the flow dynamics. Evidence was given of the improvements brought by the herein referred to, “double flux” configuration in comparison to traditional designs. After a brief description of the experimental facility and the basic principle underlying the approach developed, the main results are reported and discussed and recommendations are drawn. Considerations about where the effort will be directed in future works are provided.

scholarly journals Particle image velocimetry measurements of induced separation at the leading edge of a plate

2016 ◽  
Vol 804 ◽  
pp. 278-297 ◽  
Author(s):  
J. P. J. Stevenson ◽  
K. P. Nolan ◽  
E. J. Walsh
Keyword(s):  
Particle Image Velocimetry ◽  
Shear Layer ◽  
Particle Image ◽  
Reverse Flow ◽  
Leading Edge ◽  
Quadrant Analysis ◽  
Bypass Transition ◽  
Reynolds Stresses ◽  
Free Stream Turbulence ◽  
Image Velocimetry

The free shear layer that separates from the leading edge of a round-nosed plate has been studied under conditions of low (background) and elevated (grid-generated) free stream turbulence (FST) using high-fidelity particle image velocimetry. Transition occurs after separation in each case, followed by reattachment to the flat surface of the plate downstream. A bubble of reverse flow is thereby formed. First, we find that, under elevated (7 %) FST, the time-mean bubble is almost threefold shorter due to an accelerated transition of the shear layer. Quadrant analysis of the Reynolds stresses reveals the presence of slender, highly coherent fluctuations amid the laminar part of the shear layer that are reminiscent of the boundary-layer streaks seen in bypass transition. Instability and the roll-up of vortices then follow near the crest of the shear layer. These vortices are also present under low FST and in both cases are found to make significant contributions to the production of Reynolds stress over the rear of the bubble. But their role in reattachment, whilst important, is not yet fully clear. Instantaneous flow fields from the low-FST case reveal that the bubble of reverse flow often breaks up into two or more parts, thereby complicating the overall reattachment process. We therefore suggest that the downstream end of the ‘separation isoline’ (the locus of zero absolute streamwise velocity that extends unbroken from the leading edge) be used to define the instantaneous reattachment point. A histogram of this point is found to be bimodal: the upstream peak coincides with the location of roll-up, whereas the downstream mode may suggest a ‘flapping’ motion.

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