scholarly journals High Speed Imaging of Flame Structure and Dynamic Processes in Swirl Stabilized Prevaporized Liquid Fuel Flames

2019 ◽  
Author(s):  
Christoph M. Arndt ◽  
Adam M. Steinberg ◽  
Jan Böhnke ◽  
Redjem Hadef ◽  
Wolfgang Meier
Keyword(s):  
High Speed ◽  
Liquid Fuel ◽  
Flame Structure ◽  
Dynamic Processes ◽  
High Speed Imaging

scholarly journals High speed imaging of dynamic processes with a switched source x-ray CT system

2015 ◽  
Vol 26 (5) ◽  
pp. 055401 ◽  
Author(s):  
William M Thompson ◽  
William R B Lionheart ◽  
Edward J Morton ◽  
Mike Cunningham ◽  
Russell D Luggar
Keyword(s):  
High Speed ◽  
Dynamic Processes ◽  
High Speed Imaging ◽  
X Ray ◽  
Ct System

Application of Proper Orthogonal Decomposition to High Speed Imaging for the Study of Combustion Oscillations

2017 ◽  
Author(s):  
Siddhartha Gadiraju ◽  
Suhyeon Park ◽  
David Gomez-Ramirez ◽  
Srinath V. Ekkad ◽  
K. Todd Lowe ◽  
...  
Keyword(s):  
Proper Orthogonal Decomposition ◽  
High Speed ◽  
Equivalence Ratio ◽  
Flame Structure ◽  
Low Frequency ◽  
Orthogonal Decomposition ◽  
Pressure Measurements ◽  
High Speed Imaging ◽  
Flame Structures ◽  
Proper Orthogonal

The flame structure and characteristics generated by an industrial low emission, lean premixed, fuel swirl nozzle were analyzed for understanding combustion oscillations. The experimental facility is located at the Advanced Propulsion and Power Laboratory (APPL) at Virginia Tech. The experiments were carried out in a model optical can combustor operating at atmospheric pressures. Low-frequency oscillations (<100 Hz) were observed during the reaction as opposed to no reaction, cold flow test cases. The objective of this paper is to understand the frequency and magnitude of oscillations due to combustion using high-speed imaging and associate them with corresponding structure or feature of the flame. Flame images were obtained using a Photron Fastcam SA4 high-speed camera at 500 frames per second. The experiments were conducted at equivalence ratios of 0.65, 0.75; different Reynolds numbers of 50K, 75K; and three pilot fuel to main fuel ratios of 0%, 3%, 6%. In this study, Reynolds number was based on the throat diameter of the fuel nozzle. Since the time averaged flame images are not adequate representation of the flame structures, proper orthogonal decomposition (POD) was applied to the flame images to extract the dominant features. The spatiotemporal dynamics of the images can be decomposed into their constituent modes of maximum spatial variance using POD so that the dominant features of the flame can be observed. The frequency of the dominant flame structures, as captured by the POD modes of the flame acquisitions, were consistent with pressure measurements taken at the exit of the combustor. Thus, the oscillations due to combustion can be visualized using POD. POD was further applied to high-speed images taken during instabilities. Specifically, the instabilities discussed in this paper are those encountered when the equivalence ratio is reduced to the levels approaching lean blowout (LBO). As the equivalence ratio is reduced to near blowout regime, it triggers low-frequency high amplitude instabilities. These low-frequency instabilities are visible as the flapping of the flame. The frequencies of the dominant POD modes are consistent with pressure measurements recorded during these studies.

Simulation of the Ignition Process in an Annular Multiple-Injector Combustor and Comparison With Experiments

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Maxime Philip ◽  
Matthieu Boileau ◽  
Ronan Vicquelin ◽  
Thomas Schmitt ◽  
Daniel Durox ◽  
...  
Keyword(s):  
High Speed ◽  
Burning Velocity ◽  
Flame Structure ◽  
Combustion Model ◽  
Ignition Process ◽  
High Speed Imaging ◽  
Flamelet Model ◽  
Swirl Injectors ◽  
Eddy Simulation ◽  
Annular Combustor

Ignition is a problem of fundamental interest with critical practical implications. While there are many studies of ignition of single injector configurations, the transient ignition of a full annular combustor has not been extensively investigated, mainly because of the added geometrical complexity. The present investigation combines simulations and experiments on a complete annular combustor. The setup, developed at EMC2 (Energétique Moléculaire et Macroscopique Combustion) Laboratory (Mesa, AZ), features sixteen swirl injectors and quartz walls allowing direct visualization of the flame. High speed imaging is used to record the space time flame structure and study the dynamics of the light-round process. On the numerical side, massively parallel computations are carried out in the large eddy simulation (LES) framework using the filtered tabulated (F-TACLES) flamelet model. Comparisons are carried out at different instants during the light-round process between experimental data and results of calculations. It is found that the simulation results are in remarkable agreement with experiments provided that the thermal effects at the walls are considered. Further analysis indicate that the flame burning velocity and flame front geometry are close to those found in the experiment. This investigation confirms that the LES framework used for these calculations and the selected combustion model are adequate for such calculations but that further work is needed to show that ignition prediction can be used reliably over a range of operating parameters.

Simulation of the Ignition Process in an Annular Multiple-Injector Combustor and Comparison With Experiments

2014 ◽  
Author(s):  
Maxime Philip ◽  
Matthieu Boileau ◽  
Ronan Vicquelin ◽  
Thomas Schmitt ◽  
Daniel Durox ◽  
...  
Keyword(s):  
High Speed ◽  
Burning Velocity ◽  
Flame Structure ◽  
Combustion Model ◽  
Ignition Process ◽  
High Speed Imaging ◽  
Flamelet Model ◽  
Swirl Injectors ◽  
Geometrical Complexity ◽  
Annular Combustor

Ignition is a problem of fundamental interest with critical practical implications. While there are many studies of ignition of single injector configurations, the transient ignition of a full annular combustor has not been extensively investigated, mainly because of the added geometrical complexity. The present investigation combines simulations and experiments on a complete annular combustor. The setup, developed at EM2C laboratory, features sixteen swirl injectors and quartz walls allowing direct visualization of the flame. High speed imaging is used to record the space time flame structure and study the dynamics of the light-round process. On the numerical side, massively parallel computations are carried out in the LES framework using the Filtered Tabulated (F-TACLES) flamelet model. Comparisons are carried out at different instants during the light-round process between experimental data and results of calculations. It is found that the simulation results are in remarkable agreement with experiments provided that the thermal effects at the walls are considered. Further post-processings indicate that the flame burning velocity and flame front geometry are close to those found in the experiment. This analysis confirms that the LES framework used for these calculations and the selected combustion model are adequate for such calculations but that further work is needed to confirm that ignition prediction can be used reliably over a range of operating parameters.

Dynamics of Lean Blowout in Premixed Combustion With Hydrogen Addition

2012 ◽  
Author(s):  
Shengrong Zhu ◽  
Sumanta Acharya
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Flame Structure ◽  
Fuel Mixture ◽  
Premixed Combustion ◽  
Fluorescence Measurement ◽  
Extinction Time ◽  
High Speed Imaging ◽  
Lean Premixed Combustion ◽  
Hydrogen Addition

An experimental study of lean premixed combustion in a swirl-stabilized combustor is undertaken to characterize the dynamics and time scales close to Lean Blow Out (LBO) conditions. Due to the recent interest in syngas fuels, the effect of hydrogen addition on LBO is studied. In present study, both confined and unconfined turbulent methane air premixed flames have been examined with different hydrogen levels during the extinction transition with high speed imaging of OH* chemiluminescence at 2 KHz. Planar laser induced fluorescence measurement of OH is also performed for studying the flame structure. The blowout conditions are approached by reducing the flow rate of fuel mixture or the equivalence ratio with constant air flow rate. The estimated extinction times from high speed imaging and corresponding flame structures are analyzed and compared between confined and unconfined flames with different hydrogen blends. The extinction time scale and the heat release fluctuations show inverse trends with hydrogen addition for the confined and unconfined flames, and are indicative of different stabilization and blow out mechanisms for the two configurations. These mechanisms which involve heat losses from the flame, inner- and corner recirculation zones and unsteady flame dynamics are described in the paper.

scholarly journals The influence of pilot injection on high-temperature ignition processes and early flame structure in a high-speed direct injection diesel engine

2017 ◽  
Vol 19 (6) ◽  
pp. 668-681 ◽  
Author(s):  
Cheolwoong Park ◽  
Stephen Busch
Keyword(s):  
High Temperature ◽  
Diesel Engine ◽  
High Speed ◽  
Direct Injection ◽  
Flame Structure ◽  
High Speed Imaging ◽  
Spatially Resolved ◽  
Flame Development ◽  
Main Injection ◽  
Peak Release

Simultaneous high-speed natural luminosity and OH* chemiluminescence imaging is used to characterize high-temperature ignition processes in conventional diesel combustion with a pilot-main injection strategy in a single-cylinder, light-duty optical diesel engine. High-speed imaging provides temporally and spatially resolved information in terms of high-temperature ignition processes and flame structure during the combustion. Using these imaging measurements, the high-temperature inflammation and the diffusion flame development processes are analyzed. The chemiluminescence signal shows a hot, reactive mixture, which gradually decreases after the peak release of the pilot combustion and lasts long after the apparent heat release has ended. Therefore, when the reactive pilot mixture exists near the main injection jets, the high-temperature ignition of the main injection is apparently initiated through interactions with the reactive pilot mixture. High-temperature autoignition, another process by which ignition of the main injection occurs, is observed in main injection plumes where the chemiluminescence signal of the reactive pilot mixture becomes very weak or is absent at the start of main injection. As the reaction of the main injection continues, the non-premixed main injection jet structure is developed and the high-temperature reacting region expands throughout the jet.

Experimental Measurement of In-Plane Rolling Nonpneumatic Tire Vibrations Using High-Speed Imaging

2019 ◽  
Vol 47 (3) ◽  
pp. 196-210
Author(s):  
Meghashyam Panyam ◽  
Beshah Ayalew ◽  
Timothy Rhyne ◽  
Steve Cron ◽  
John Adcox
Keyword(s):  
High Speed ◽  
Image Correlation ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
High Speed Imaging ◽  
Correlation Algorithm ◽  
Mode Decomposition ◽  
Series Of Experiments ◽  
Plane Deformations ◽  
Dominant Frequencies

ABSTRACT This article presents a novel experimental technique for measuring in-plane deformations and vibration modes of a rotating nonpneumatic tire subjected to obstacle impacts. The tire was mounted on a modified quarter-car test rig, which was built around one of the drums of a 500-horse power chassis dynamometer at Clemson University's International Center for Automotive Research. A series of experiments were conducted using a high-speed camera to capture the event of the rotating tire coming into contact with a cleat attached to the surface of the drum. The resulting video was processed using a two-dimensional digital image correlation algorithm to obtain in-plane radial and tangential deformation fields of the tire. The dynamic mode decomposition algorithm was implemented on the deformation fields to extract the dominant frequencies that were excited in the tire upon contact with the cleat. It was observed that the deformations and the modal frequencies estimated using this method were within a reasonable range of expected values. In general, the results indicate that the method used in this study can be a useful tool in measuring in-plane deformations of rolling tires without the need for additional sensors and wiring.

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