Analysis of the Spray and Transfer Function of Swirling Spray Flames From a Multi-Jet Steam Assisted Liquid Fuel Injector

2014 ◽  
Author(s):  
Clément Mirat ◽  
Daniel Durox ◽  
Thierry Schuller
Keyword(s):  
Transfer Function ◽  
Flow Rate ◽  
Transfer Functions ◽  
Swirling Flow ◽  
Laser Doppler Anemometry ◽  
Low Frequency ◽  
Laser Doppler ◽  
Flow Rate Ratio ◽  
Fuel Injector ◽  
Spray Flames

Characterizations of the response of swirling spray flames to flow rate modulations over the entire frequency range remain scarce. This response is addressed here by determining the transfer function of spray flames stabilized on a multi-jet steam-assisted dodecane injector in a turbulent swirling flow confined by a quartz tube. This type of burner is used in some liquid fueled industrial boilers. In the absence of combustion and air flow, a phase Doppler particle analyzer is used to determine the Sauter mean diameter (SMD) of the fuel spray as a function of the atomizing gas to fuel mass flow rate ratio (GLR) injected in the nozzle. For small values of the GLR, the SMD of the generated spray decreases rapidly as the GLR increases. For GLR values above a certain threshold, the SMD reaches a constant value that is independent of the GLR. Transfer functions are measured in this second regime for swirling air flows characterized by a swirl number S = 0.92 that is determined by laser Doppler anemometry. Transfer functions defined as the normalized ratio of OH* or CH* flame chemiluminescence intensity fluctuations divided by the velocity oscillation level measured by laser Doppler velocimetry at the burner outlet are determined as a function of the forcing frequency for a small perturbation level. The response of sooty and non sooty flames at globally lean conditions are examined. Using a set of steady experiments, it is shown that the OH* signal may safely be used to confidently estimate low frequency heat release rate disturbances for both types of flames, but the CH* signal cannot be used in the sooty flame cases. The measured transfer functions of non-sooty spray flames feature many similarities with the transfer function of perfectly premixed swirling flames indicating that their dynamics is also controlled by interference mechanisms that need to be elucidated.

Changes in Carotid Artery Flow Velocities after Stent Implantation: A Fluid Dynamics Study with Laser Doppler Anemometry

2003 ◽  
Vol 10 (2) ◽  
pp. 275-284 ◽  
Author(s):  
Oliver Greil ◽  
Gottlieb Pflugbeil ◽  
Klaus Weigand ◽  
Wolfgang Weiß ◽  
Dieter Liepsch ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Flow Rate ◽  
Rate Ratio ◽  
Laser Doppler Anemometry ◽  
Flow Behavior ◽  
Laser Doppler ◽  
Flow Rate Ratio ◽  
External Carotid ◽  
Flow Profile ◽  
Separation Zones

Purpose: To study the influence of stent size and location on flow patterns in a physiological carotid model. Methods: Wallstents were positioned in silicon models of the carotid artery at various locations: 2 stents appropriately sized to the anatomy were placed in (1) the internal carotid artery (ICA) and (2) the ICA extending completely into the common carotid artery so as to cover the external carotid artery (ECA) orifice. Another 2 stents were placed in the ICA extending (1) partially and (2) completely into the bulb to simulate stent displacement and disproportion between stent size and the original vessel geometry. Measurements were performed with laser Doppler anemometry (LDA) using pulsatile flow conditions (Reynolds number=250; flow 0.431 L/min; ICA:ECA flow rate ratio 70:30) in hemodynamically relevant cross sections. The hemodynamic changes were analyzed with 1-dimensional flow profiles. Results: With the stent in the ICA, no changes of the normal flow profile were seen. For stents positioned in the ICA and extending partially or completely into the carotid bulb, the flow behavior was affected by the resistance of the stent to flow in the ECA. Hemodynamically relevant disturbances were seen in the ICA and ECA, especially in the separation zones (regions along the walls just after a bifurcation, bend, or curve). The ICA:ECA flow rate ratios shifted from 70:30 to 71.3:28.7 and from 70:30 to 75.1:24.9, respectively, in the 2 malpositioned stent models. With the stent placed in the ICA extending completely into the CCA, the ICA:ECA flow rate ratio shifted from 70:30 to 72.4:27.6. In this configuration, there were no notable flow changes in the ICA, but a clear diminishing of the separation zones in the ECA separation zones. Conclusions: Anatomically correct positioning of appropriately sized stents does not lead to relevant flow disturbances in the ICA. In the ECA, depending on the position, size, and interstices of the stent, the physiological flow was considerably disturbed when any part of the stent covered the inflow of the vessel. Disturbances were seen when the stent was positioned into the bulb. For clinical application, stent location and size must be carefully determined so that the stent covers the bifurcation completely or is in the ICA only.

Experimental Development of On-Line Flame Transfer Function Measurements for Fielded Gas Turbines

2021 ◽  
Author(s):  
Austin Matthews ◽  
Anna Cobb ◽  
Subodh Adhikari ◽  
David Wu ◽  
Tim Lieuwen ◽  
...  
Keyword(s):  
Transfer Function ◽  
Heat Release ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Transfer Functions ◽  
Full Scale ◽  
Fuel Injector ◽  
Experimental Development ◽  
On Line

Abstract Understanding thermoacoustic instabilities is essential for the reliable operation of gas turbine engines. To complicate this understanding, the extreme sensitivity of gas turbine combustors can lead to instability characteristics that differ across a fleet. The capability to monitor flame transfer functions in fielded engines would provide valuable data to improve this understanding and aid in gas turbine operability from R&D to field tuning. This paper presents a new experimental facility used to analyze performance of full-scale gas turbine fuel injector hardware at elevated pressure and temperature. It features a liquid cooled, fiber-coupled probe that provides direct optical access to the heat release zone for high-speed chemiluminescence measurements. The probe was designed with fielded applications in mind. In addition, the combustion chamber includes an acoustic sensor array and a large objective window for verification of the probe using high-speed chemiluminescence imaging. This work experimentally demonstrates the new setup under scaled engine conditions, with a focus on operational zones that yield interesting acoustic tones. Results include a demonstration of the probe, preliminary analysis of acoustic and high speed chemiluminescence data, and high speed chemiluminescence imaging. The novelty of this paper is the deployment of a new test platform that incorporates full-scale engine hardware and provides the ability to directly compare acoustic and heat release response in a high-temperature, high-pressure environment to determine the flame transfer functions. This work is a stepping-stone towards the development of an on-line flame transfer function measurement technique for production engines in the field.

Investigation into the structure of a swirling flow in a model of a vortex combustion chamber by laser doppler anemometry

2013 ◽  
Vol 39 (1) ◽  
pp. 30-32 ◽  
Author(s):  
I. S. Anufriev ◽  
Yu. A. Anikin ◽  
A. I. Fil’kov ◽  
E. L. Loboda ◽  
M. V. Agafontseva ◽  
...  
Keyword(s):  
Combustion Chamber ◽  
Swirling Flow ◽  
Laser Doppler Anemometry ◽  
Laser Doppler ◽  
Vortex Combustion

Flame Transfer Function for Swirled LPP Combustion From Experiments and CFD

2004 ◽  
Author(s):  
Carol A. Armitage ◽  
Alex J. Riley ◽  
R. Stewart Cant ◽  
Ann P. Dowling ◽  
Simon R. Stow
Keyword(s):  
Time Delay ◽  
Transfer Function ◽  
Gas Turbines ◽  
Transfer Functions ◽  
Low Frequency ◽  
Analytical Models ◽  
Delay Spread ◽  
Good Representation ◽  
Atmospheric Conditions ◽  
Spread Model

Combustion oscillations that arise in gas turbines can lead to plant damage. One method used to predict these oscillations is to analyse the acoustics using a simple linear model. This model requires a transfer function to describe the response of the heat release to flow perturbations. A transfer function has been obtained for a swirled premixed combustion system using experiments under atmospheric conditions and CFD. These results have been compared with analytical models. The experimental and computational transfer functions both indicate a low frequency zero. A time-delay spread model gives a good representation of the computational transfer function. The experimental transfer function is described well by a model that combines a time-delay spread with a constant gain.

Traceable Flow Rate Measurements With a Very Low Uncertainty Using Laser Doppler Anemometry

2017 ◽  
Author(s):  
Markus Juling ◽  
Jonas Steinbock ◽  
Andreas Weissenbrunner
Keyword(s):  
Flow Rate ◽  
Laser Doppler Anemometry ◽  
Volume Flow Rate ◽  
Primary Standard ◽  
Volume Flow ◽  
Laser Doppler ◽  
Maximum Deviation ◽  
Flow Profile ◽  
Rate Measurement ◽  
Flow Rate Measurement

Precise volume flow rate measurements are very important for various industrial applications. Here, one problem is that the service conditions of a flow meter used in the field differ significantly from the conditions present during calibration. The working conditions such as the pressure, the temperature and the flow profile greatly increase the uncertainty of the flow rate measurement. To address this problem, a new laser-optical flow rate standard (LFS) was developed at the Physikalisch-Technische Bundesanstalt (PTB) that allows flow meters to be calibrated on site, thus greatly reducing the uncertainty of the flow rate measurement. For the LFS, the velocity profile within the pipe is measured with laser Doppler anemometry (LDA). The profile is then integrated to calculate the volume flow rate. Various improvements to LDA have made it possible to measure the flow rate with an uncertainty of less than 0.15 % (k = 2). A comparison of the LFS with the primary standard for thermal energy at PTB, which has an uncertainty of less than 0.04 % (k = 2), revealed a maximum deviation of 0.07 % for Reynolds numbers from 105 to 106, thus verifying the uncertainty of the LFS.

scholarly journals Selective quantification of the cardiac sympathetic and parasympathetic nervous systems by multisignal analysis of cardiorespiratory variability

2008 ◽  
Vol 294 (1) ◽  
pp. H362-H371 ◽  
Author(s):  
Xiaoxiao Chen ◽  
Ramakrishna Mukkamala
Keyword(s):  
Nervous System ◽  
Transfer Function ◽  
Parasympathetic Nervous System ◽  
Transfer Functions ◽  
Low Frequency ◽  
Sympathetic Blockade ◽  
Nervous Systems ◽  
Autonomic Nervous ◽  
Arterial Blood ◽  
The Time Domain

Heart rate (HR) power spectral indexes are limited as measures of the cardiac autonomic nervous systems (CANS) in that they neither offer an effective marker of the β-sympathetic nervous system (SNS) due to its overlap with the parasympathetic nervous system (PNS) in the low-frequency (LF) band nor afford specific measures of the CANS due to input contributions to HR [e.g., arterial blood pressure (ABP) and instantaneous lung volume (ILV)]. We derived new PNS and SNS indexes by multisignal analysis of cardiorespiratory variability. The basic idea was to identify the autonomically mediated transfer functions relating fluctuations in ILV to HR (ILV→HR) and fluctuations in ABP to HR (ABP→HR) so as to eliminate the input contributions to HR and then separate each estimated transfer function in the time domain into PNS and SNS indexes using physiological knowledge. We evaluated these indexes with respect to selective pharmacological autonomic nervous blockade in 14 humans. Our results showed that the PNS index derived from the ABP→HR transfer function was correctly decreased after vagal and double (vagal + β-sympathetic) blockade ( P < 0.01) and did not change after β-sympathetic blockade, whereas the SNS index derived from the same transfer function was correctly reduced after β-sympathetic blockade in the standing posture and double blockade ( P < 0.05) and remained the same after vagal blockade. However, this SNS index did not significantly decrease after β-sympathetic blockade in the supine posture. Overall, these predictions were better than those provided by the traditional high-frequency (HF) power, LF-to-HF ratio, and normalized LF power of HR variability.

Uncomplicated Setting Apparatus for Measurement of Fluid Flow Rate Using Laser Doppler Technique: Physics Teaching

2013 ◽  
Vol 770 ◽  
pp. 366-369
Author(s):  
Chatchalong Apiputikul ◽  
Kheamrutai Thamaphat ◽  
Monrudee Ranusawad ◽  
Pichet Limsuwan
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Doppler Shift ◽  
Laser Doppler Anemometry ◽  
Scattered Light ◽  
Fluid Velocity ◽  
Water Flow Rate ◽  
Processing System ◽  
Laser Doppler ◽  
Single Observation

Laser Doppler velocimetry (LDV) or laser Doppler anemometry (LDA) is the technique of using the Doppler shift in a laser beam to determine the fluid velocity. In this work, dual beam mode (two incident beams, single observation location) was selected to use. A cost effective and easy module for measurement of water flow rate was designed and constructed. A He-Ne laser with a wavelength of 632.8 nm was used as a light source. The laser was passed through a beam splitter and divided into two beams with identical intensity and coherence. Subsequently, the two laser beams travelled to a focusing lens with a focal length of 100 mm and focused on a center of water flow channel in quartz cuvette with a dimension of 1 × 1 × 5 cm3. The beam angle was set at 4.96°. When the seeding particles, bubbles and microorganism in water, were moving through the intersection point of two beams, the light was scattered. The scattered light was collected by photodetector connected to processing system. The frequency of scatterred light is shifted according to the Doppler shift relations due to effect of Rayleigh scattering. The water flow rate can be calculated from Doppler shift frequency.

Study of Flame Transfer Function With Three Dimensional Calculations

2003 ◽  
Author(s):  
M. Zhu ◽  
A. P. Dowling ◽  
K. N. C. Bray
Keyword(s):  
Transfer Function ◽  
Transfer Functions ◽  
Three Dimensional ◽  
Low Frequency ◽  
Systematic Investigation ◽  
Flow Properties ◽  
Low Frequency Oscillation ◽  
Local Flow ◽  
Shape Factors ◽  
Annular Combustor

Combustors with fuel-spray atomisers are particularly susceptible to a low-frequency oscillation at idle and sub-idle conditions. For aero-engine combustors, the frequency of this oscillation is typically in the range 70–120Hz and is commonly called ‘rumble’. The mechanism involves interaction between the plenum around the burner and the combustion chamber. In our previous work, the CFD calculation has been conducted in an idealised 2D axisymmetric annular combustor to calculate unsteady combustion flow at idle conditions. In this work, in order to investigate the effects of asymmetrical geometry and flow distributions on the transfer functions of flame and shape factors, the CFD code has been extended to fully three-dimensional geometries. The results are compared with those from 2D calculations. Though the differences of the distribution local flow properties are evident, the integrated results for the 3D flow are broadly similar to those obtained in 2D. One substantial difference arises due to the more accurate modelling of the downstream contraction near the combustor exit, which is treated as a smooth contraction in our 3D calculations and as an abrupt change in the simplified 2D geometry. The gradual downstream contraction not only accelerates the fluid near the combustor exit but also unifies the flow properties. As the consequence, we can see that, near the exit, the phase of the flame transfer function increases rapidly, and the shape factors tend toward unity. This work is a further development of our systematic investigation into the ‘rumble’ phenomenon, and gives encouragement that much of the essential physics can be captured in a quasi-one-dimensional model.

scholarly journals Development of the method of laser Doppler anemometry for diagnostics of turbulent flows at high speed

2021 ◽  
Vol 2119 (1) ◽  
pp. 012110
Author(s):  
M R Gordienko ◽  
I K Kabardin ◽  
V G Meledin ◽  
A K Kabardin ◽  
M Kn Pravdina ◽  
...  
Keyword(s):  
Turbulent Flows ◽  
Flow Rate ◽  
High Speed ◽  
Velocity Vector ◽  
Laser Doppler Anemometry ◽  
Laser Doppler ◽  
Local Flow ◽  
Positioning Device ◽  
Measurement Area ◽  
Measuring Unit

Abstract The aim of the work was to develop a laser Doppler anemometry method for high-speed turbulent aerodynamic flow diagnostic. As a result, this allowed us to measure two projections of the velocity vector in the range of 0.1 - 400 m/s with a relative error not exceeding 0.5%. The measurement area was 0.1x0.1x0.5mm. The positioning device moved the measuring unit in the area of 250 x 250 x 250 mm with an accuracy of 0.1 mm. This method also provides the ability to measure local flow rate fluctuations.

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