An Investigation of Flame Expansion Speed With a Strong Swirl Motion Using High-Speed Visualization

2003 ◽  
Vol 125 (2) ◽  
pp. 485-493
Author(s):  
S. H. Joo ◽  
K. M. Chun ◽  
Y. Shin ◽  
K. C. Lee
Keyword(s):  
High Speed ◽  
Combustion Process ◽  
Flow Characteristics ◽  
Video Camera ◽  
Frame Rate ◽  
Superposition Method ◽  
Linear Superposition ◽  
Compression Stroke ◽  
Engine Cylinder ◽  
Expansion Speed

In this study, a simple linear supposition method is proposed to separate the flame expansion speed and swirl motion of a flame propagating in an engine cylinder. Two series of images of flames propagating in the cylinder with/without swirl motion were taken by a high frame rate digital video camera. A small tube (4 mm ID) was installed inside the intake port to deliver the fuel/air mixture with strong swirl motion into the cylinder. An LDV was employed to measure the swirl motion during the compression stroke. Under the assumption that flame propagates spherically from the each point of the flame front, a diameter of small spherical flames can be calculated from the two consecutive images of the flame without swirl motion in the cylinder. Using the normalized swirl motion of the mixture during the compression stroke and the spherical flame diameters, the flame expansion speed and swirl ratio of combustion propagation in the engine cylinder can be obtained. This simple linear superposition method for separating the flame expansion speed and swirl motion can be utilized to understand the flow characteristics, such as swirl and turbulence, during the combustion process.

Visualization of diesel spray and combustion from lateral side of two-dimensional piston cavity in rapid compression and expansion machine

2020 ◽  
pp. 146808742096229
Author(s):  
Chengyuan Fan ◽  
Daoyuan Wang ◽  
Keiya Nishida ◽  
Yoichi Ogata
Keyword(s):  
High Speed ◽  
Combustion Process ◽  
Video Camera ◽  
Lateral Side ◽  
Two Dimensional ◽  
Split Injection ◽  
Compression And Expansion ◽  
Color Video ◽  
Wall Interaction ◽  
Injection Strategies

Effect of spray/wall interaction in a rapid compression and expansion machine on mixture formation, ignition location, and soot generation was investigated. A two-dimensional piston cavity designed as the cross section of a reentrant piston was utilized to observe the spray and combustion process from the lateral side. The experiment was conducted at 120 MPa injection pressure under single and split injection strategies with an ambient gas of 15% O2 concentration. A shadow methodology was applied to investigate the interaction between the fuel spray and the piston cavity. Combined with the natural flame luminosity captured by a high-speed color video camera, the behaviors of the impinging spray and the combustion process were studied. The combustion characteristics of the in-cylinder pressure, heat release and combustion phase were recorded and analyzed simultaneously. The results showed that the split injection strategies effectively softened the heat release trace and promoted the onset of the main combustion. The cool-flame phenomenon was captured by using the high-speed color video camera, and the intense ignition was observed when the pilot spray was controlled to impinge on the lower lip of the piston rim. Moreover, results also showed that further extending the mixing process of the pilot spray is inclined to form a homogeneous mixture which was beneficial for the promotion of low-temperature combustion and the reduction of soot generation. This research provides a detailed investigation on the spray and combustion process and it highlights the significant effect of spray/wall interaction on the subsequent combustion process.

scholarly journals Justification of the Energy Use of Cedar Husk Waste as an Environmentally Friendly Additive for Co-Combustion with Coal

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7027
Author(s):  
Yankovsky Stanislav ◽  
Tolokol’nikov Anton ◽  
Berezikov Nikolay ◽  
Gubin Vladimir
Keyword(s):  
Ignition Delay ◽  
High Speed ◽  
Energy Use ◽  
Video Camera ◽  
Hydraulic Press ◽  
Frame Rate ◽  
Mixed Fuel ◽  
Industry Waste ◽  
Ignition Delay Times ◽  
Initial Fuel

In this paper, the properties of ignition of mixed fuel pellets formed on the basis of fairly typical energy coal and wood industry waste in the form of cedar husks are experimentally established. The technical characteristics of the initial fuel components and the mixtures based on them, the ignition delay times for different mass concentrations of biomass in coal, and the composition of flue gases formed during the thermal decomposition of these mixed fuels and their base components were determined. Pellets of mixed fuels were made by a hydraulic press. The experiments were performed in an air environment at temperatures from 600 °C to 800 °C. Recording of the processes of pellet ignition and combustion was carried out using a high-speed video camera with an image format of 1024 × 1024 pixels, and a frame rate up to 500 frames per second. The analysis of the flue gas composition was performed using a Test-1 factory gas analyzer (BONER Co.). It was found that the increase in the share of biomass up to 50% in the mixed fuel led to a significant reduction in the ignition delay time to less than 1 s and the sequestration of sulfur oxide emissions by 37.6% and of nitrogen oxides by 3.8% in the studied granular mixed fuels.

IGNITION AND STABILIZATION OF HOMOGENEOUS COMBUSTION IN HIGH-SPEED FLOW BY PULSE-PERIODIC LASER RADIATION

2020 ◽  
Author(s):  
V. N. Zudov ◽  
◽  
P. K. Tretyakov ◽  
A. V. Tupikin ◽  
◽  
...  
Keyword(s):  
Co2 Laser ◽  
High Speed ◽  
Radiation Spectrum ◽  
Combustion Process ◽  
Frame Rate ◽  
Optical Discharge ◽  
Speed Flow ◽  
Homogeneous Combustion ◽  
And Behavior ◽  
Spectrozonal Registration

The paper present the results of an experimental study of the effect of focused pulsed-periodic radiation from a CO2 laser on the initiation and development of a combustion process in subsonic and supersonic flows of homogeneous fuel-air mixtures (H2 + air and CH4 + air). The radiation from the CO2 laser propagated across the stream and was focused on the jet axis. To register the flow structure, a schlieren imaging setup with a slit and a flat knife was used. The image was recorded by a high-speed camera with exposure time of 1.5 s and frame rate of 1000 fps. At the same time, spectrozonal recording (at the wavelength of OH* and CH* radiation) and emission spectroscopy (in the wavelength range of 210-780 nm) was carried out. Stable ignition of methane and hydrogen-air mixture has been obtained at supersonic outflow into the flooded space. The results of the spectrozonal registration indicate the occurrence of combustion reactions in the wake behind the optical discharge region. The analysis of the radiation spectrum of optical discharge in a supersonic flow revealed the main types of radicals present in the plasma. Strong intensity was found in the H lines, which cannot help but affect the development of the initiation and behavior of the combustion process in the wake of the optical discharge.

The Effects of Particle Segregation on Debris Flow Fluidity Over a Rigid Bed

2020 ◽  
Vol 27 (1) ◽  
pp. 139-149
Author(s):  
Norifumi Hotta ◽  
Tomoyuki Iwata ◽  
Takuro Suzuki ◽  
Yuichi Sakai
Keyword(s):  
Shear Stress ◽  
Debris Flow ◽  
Debris Flows ◽  
High Speed ◽  
Particle Diameter ◽  
Flow Characteristics ◽  
Video Camera ◽  
Front Velocity ◽  
Flow Depth ◽  
Particle Segregation

ABSTRACT It is essential to consider the fluidity of a debris flow front when calculating its impact. Here we flume-tested mono-granular and bi-granular debris flows and compared the results to those of numerical simulations. We used sand particles with diameters of 0.29 and 0.14 cm at two mixing ratios of 1:1 and 3:7. Particle segregation was recorded with a high-speed video camera. We evaluated the fronts of debris flows at 0.5-second intervals. Then we numerically simulated one-dimensional debris flows under the same conditions and used the mean particle diameter when simulating mixed-diameter flows. For the mono-granular debris flows, the experimental and simulated results showed good agreement in terms of flow depth, front velocity, and flux. However, for the bi-granular debris flows, the simulated flow depth was less, and both the front velocity and flux were greater than those found experimentally. These differences may be attributable to the fact that the dominant shear stress was caused by the concentration of smaller sediment particles in the lower flow layers; such inverse gradations were detected in the debris flow bodies. Under these conditions, most shear stress is supported by smaller particles in the lower layers; the debris flow characteristics become similar to those of mono-granular flows, in contrast to the numerical simulation, which incorporated particle segregation with gradually decreasing mean diameter from the front to the flow body. Consequently, the calculated front velocities were underestimated; particle segregation at the front of the bi-granular debris flows did not affect fluidity either initially or over time.

Investigation of Cycle-to-Cycle Variation of In-Cylinder Engine Swirl Flow Fields Using Quadruple Proper Orthogonal Decomposition

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Penghui Ge ◽  
David L. S. Hung
Keyword(s):  
Proper Orthogonal Decomposition ◽  
High Speed ◽  
Combustion Process ◽  
Flow Characteristics ◽  
Propagation Speed ◽  
Fuel Mixture ◽  
Flow Fields ◽  
Swirl Flow ◽  
Orthogonal Decomposition ◽  
Proper Orthogonal

It has been observed that the swirl characteristics of in-cylinder air flow in a spark ignition direct injection (SIDI) engine affect the fuel spray dispersion and flame propagation speed, impacting the fuel mixture formation and combustion process under high swirl conditions. In addition, the cycle-to-cycle variations (CCVs) of swirl flow often degrade the air–fuel mixing and combustion quality in the cylinder. In this study, the 2D flow structure along a swirl plane at 30 mm below the injector tip was recorded using high-speed particle image velocimetry (PIV) in a four-valve optical SIDI engine under high swirl condition. Quadruple proper orthogonal decomposition (POD) was used to investigate the cycle-to-cycle variations of 200 consecutive cycles. The flow fields were analyzed by dividing the swirl plane into four zones along the measured swirl plane according to the positions of intake and exhaust valves in the cylinder head. Experimental results revealed that the coefficient of variation (COV) of the quadruple POD mode coefficients could be used to estimate the cycle-to-cycle variations at a specific crank angle. The dominant structure was represented by the first POD mode in which its kinetic energy could be correlated with the motions of the intake valves. Moreover, higher order flow variations were closely related to the flow stability at different zones. In summary, quadruple POD provides another meaningful way to understand the intake swirl impact on the cycle-to-cycle variations of the in-cylinder flow characteristics in SIDI engine.

scholarly journals Shear flow characteristics of densely packed granular material subjected to slow deformations

2013 ◽  
Vol 46 ◽  
Author(s):  
Subodh Dhakal
Keyword(s):  
Shear Flow ◽  
High Speed ◽  
Rotational Velocity ◽  
Flow Characteristics ◽  
Video Camera ◽  
Rotation Group ◽  
Particle Rotation ◽  
Moving Wall ◽  
High Speed Video Camera ◽  
Jammed State

The densely packed assembly of granular materials subjected to slow deformations is studied experimentally in the 2D shear flow apparatus. High speed video camera and subsequent image processing techniques help to document the positions of the particles in the flow. Effective algorithms are formulated to determine the particle rotation, group size and local particle concentrations. Experimental results depict that the consecutive cycles of solid like (jammed) and fluid like (un-jammed) states characterize the flow. The jammed state is represented by negligible mobilization of particles, whereas the un-jammed state is represented by considerable mobilization of particles. The rotational and translational kinetic energy shares their dominancy in the jammed and un-jammed states respectively. Nevertheless, rotational counterpart also increases quite high in un-jammed state. There exists clearly a gradient of translational and rotational velocity across the shear cell especially in the un-jammed state indicating the phenomenon of strain localization. The un-jammed state originates because of the breaking and buckling of few columns near to the inner moving wall as noticed by previous researchers, and the jammed state regenerates once the broken and buckled columns regrouped into new columns. The dilatation phenomenon is found to be associated with the un-jamming states indicated by the drop in the local particle concentrations.

Multi-camera object tracking system

2021 ◽  
Author(s):  
A.V. Bobkov ◽  
G.V. Tedeev
Keyword(s):  
High Speed ◽  
Tracking System ◽  
Correlation Method ◽  
Video Camera ◽  
Frame Rate ◽  
Camera Tracking ◽  
Topological Graph ◽  
Coverage Area ◽  
Background Removal ◽  
Detection Stage

The article proposes a multi-camera tracking system for an object, implemented using computer vision technologies and allowing the video surveillance operator in real time to select an object that will be monitored by the system in future. It will be ready to give out the location of the object at any time. The solution to this problem is divided into three main stages: the detection stage, the tracking stage and the stage of interaction of several cameras. Methods of detection, tracking of objects and the interaction of several cameras have been investigated. To solve the problem of detection, the method of optical flow and the method of removing the background were investigated, to solve the problem of tracking — the method of matching key points and the correlation method, to solve the problem of interaction between several surveillance cameras — the method of the topological graph of a network of cameras. An approach is proposed for constructing a system that uses a combination of the background removal method, the correlation method and the method of the topological graph of a network of cameras. The stages of detection and tracking have been experimentally implemented, that is, the task of tracking an object within the coverage area of one video camera has been solved. The implemented system showed good results: a sufficiently high speed and accuracy with rare losses of the tracked object and with a slight decrease in the frame rate.

Effects of Combustor Aerodynamics on the Ignition of Solid Fuel

1994 ◽  
Author(s):  
Jing-Tang Yang ◽  
Cliff Yuh-Yih Wu ◽  
Hung-Tsann Yang
Keyword(s):  
Turbulence Intensity ◽  
Solid Fuel ◽  
High Speed ◽  
Recirculation Zone ◽  
Reverse Flow ◽  
Flow Characteristics ◽  
Video Camera ◽  
Sudden Expansion ◽  
Ignition Process ◽  
High Speed Video Camera

A traditional and a modified backward-facing steps were designed to investigate the effects of flow characteristics on the ignition of the solid fuel slab in a sudden expansion combustor. Experiments were conducted separately in the cold flow for the turbulent flow field and in a hot oxidizing flow stream for the ignition tests. The velocity flowfield was measured by a laser-Doppler anemometer (LDA) and the ignition process was observed by a high-speed video camera. The inlet flow velocity for the cold flowfield measurements was kept at 15 m/s, but was varied for the ignition tests, whereas the step height of the backstep was 29 mm. The results show that the higher turbulence intensity in the boundary layer near the separated point did not always cause a higher turbulence intensity in the recirculation zone. However, the combustor with a modified backstep generated greater reverse flow rate, turbulence intensity and Reynolds stress in the recirculation zone. As a result, the ignition delay of solid fuel in the modified combustor was significantly reduced as compared with the traditional combustor.

Effect of High Swirl Velocity on Mixture Formation and Combustion Process of Diesel Spray

2012 ◽  
Vol 229-231 ◽  
pp. 695-699 ◽  
Author(s):  
Amir Khalid ◽  
Bukhari Manshoor
Keyword(s):  
Combustion Chamber ◽  
High Speed ◽  
Combustion Process ◽  
Video Camera ◽  
Exhaust Emissions ◽  
Ignition Process ◽  
Mixture Formation ◽  
Digital Video Camera ◽  
Swirl Velocity ◽  
Flame Development

Diesel engines generate undesirable exhaust emissions during combustion process and identified as major source pollution in the worldwide ecosystem. To reduce emissions, the improvements throughout the premixing of fuel and air have been considered especially at early stage of ignition process. Purpose of this study is to clarify the effects of swirl velocity on flow fuel-air premixing mechanism and burning process in diesel combustion that strongly affects the exhaust emissions. The effects of physical factors on mixture formation and combustion process to improve exhaust emissions are discussed in detail. This study investigated diesel combustion fundamentally using a rapid compression machine (RCM) together with the schlieren photography and direct photography methods. RCM was used to simulate actual phenomenon inside the combustion chamber with changing design parameter such as swirl velocity, injection strategies and variable nozzle concept. The detail behavior of mixture formation during ignition delay period was investigated using the schlieren photography system with a high speed digital video camera. This method can capture spray evaporation, spray interference and mixture formation clearly with real images. Ignition process and flame development were investigated by direct photography method using a light sensitive high-speed color digital video camera. Moreover, the mechanism and behavior of mixture formation were analyzed by newly developed image analysis technique. Under high swirl condition, the ignition delay is extended, the higher heat losses and unutilized high-density oxygen associated with slower initial heat recovery begins might be the explanation for the longer combustion duration, reductions of pick heat release and promote combustion and soot oxidation. The real images of mixture formation and flame development reveal that the spray tip penetration is bended by the high swirl motion, fuel is mainly distributed at the center of combustion chamber, resulting that flame is only formed at the center region of the combustion chamber. It is necessary for high swirl condition to improve fuel-air premixing.

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