scholarly journals Thermal Characteristics of Positive Leaders under Different Electrode Terminals in a Long Air Gap

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4024 ◽  
Author(s):  
Du ◽  
Tang ◽  
Li ◽  
Zou ◽  
Ma ◽  
...  
Keyword(s):  
High Speed ◽  
Thermal Characteristics ◽  
Video Camera ◽  
Air Gap ◽  
Radius Of Curvature ◽  
Gas Temperature ◽  
Gas Density ◽  
Interference Fringes ◽  
High Speed Video Camera ◽  
The Difference

The thermal characteristics of the positive leader discharges occurring under the different electrode terminals in a 1 m rod-plate air gap were studied quantitatively using Mach–Zehnder interferometry and a high-speed video camera. When disturbed by the discharge channel, the interference fringes are distorted because of the change in the refractive index of air, which is related to the gas density. Therefore, the gas temperature and gas density distribution in the leader channel can be retrieved from the offset of the interference fringes. Based on these results, the thermal characteristics of the leader channel were studied under different electrode terminals with a radius of curvature of 2.5 mm and 5 mm for cone electrodes and a diameter of 40 mm for a spherical electrode. The results show that the gas temperature in the leader channel increased while the gas density decreased as the radius of curvature of the electrode terminal decreased. Additionally, a smaller radius of curvature leads to a larger thermal diameter, but the difference in the thermal diameter is not obvious; for the terminals used in this paper, the difference is within 2 mm.

Effect of a Transition in a Fuel Species Fraction on the Behavior of a Bunsen-Type Premixed Flame

2017 ◽  
Author(s):  
Takuya Ishibashi ◽  
Takuya Tomidokoro ◽  
Takashi Suzuki ◽  
Shuichi Umezawa ◽  
Takeshi Yokomori ◽  
...  
Keyword(s):  
High Speed ◽  
Volume Fraction ◽  
Fuel Mixture ◽  
Video Camera ◽  
Transition Time ◽  
Flame Height ◽  
High Speed Video Camera ◽  
Two Component ◽  
The Difference ◽  
Fuel Components

Effect of transient variation in the fraction of components in the multi-component fuels on the characteristics of a Bunsen-type burner has been investigated experimentally. Methane/ethane/propane three-component fuel, methane/ethane two-component fuel and methane/propane two-component fuel were used. The flame motion under the linear transition from one fuel mixture to another was examined. The transition time was varied from 1 s to 10 s, keeping the flow velocity and the equivalence ratio constant at 0.8 m/s and 0.85 respectively. The variation in the flame height was measured, using high speed video camera at 125 fps. Experimental results showed the overshoot of the flame height in an upward or downward direction during the transition. The magnitude of the overshoot was larger for shorter transition time and for larger difference of volume fraction of fuel components. The difference in diffusion coefficient of each fuel is supposed to play an important role for the overshoot.

Auto Ignition and Knocking Phenomena in Stratified Mixture of Lean Condition

2007 ◽  
Author(s):  
Tadayoshi Ihara ◽  
Xiaojian Qin ◽  
Takafumi Tanaka ◽  
Kazunori Wakai
Keyword(s):  
Combustion Chamber ◽  
High Speed ◽  
Equivalence Ratio ◽  
Burning Velocity ◽  
Video Camera ◽  
Auto Ignition ◽  
High Speed Video Camera ◽  
The Difference ◽  
Ignition And Combustion ◽  
Bottom To Top

Experimental study has been conducted on auto ignition and knocking phenomena of stratified mixture using a rapid compression machine (RCM) in order to investigate the effects of fuel concentration gradient on the auto ignition and combustion characteristics in the condition that mean equivalence ratio is lean. N-heptane is used as a fuel and mean equivalence ratio is 0.6, 0.8 and 1.0 in the combustion chamber. In the chamber, the lower the vertical location is, the richer the concentration of the mixture is. The difference of the equivalence ratio from bottom to top in the chamber is varied from 0 to 1.4. Mixture has no gradient in horizontal direction. Initial temperature of the mixture is 290K and pressure is 0.1MPa before compression. The diameter of the combustion chamber is 65mm and the compression ratio is 10.5. High-speed video camera is set in front of chamber so that direct images of mixture from cylinder axis direction can be obtained. A pressure transducer is used to obtain pressure histories of chamber, from which ignition delay, pressure rising rate and knocking intensity are determined. The results show that: 1. Flame speed of stratified mixture obtained from direct flame images is much faster than that of calculated laminar burning velocity for corresponding mixture, thus, rapid spread of flame in the experiment is caused not by flame propagation but by consecutive auto ignition. 2. Ignition delays of stratified mixture, not depending on the gradient of mixture, are constant as far as mean equivalence ratio is same and decrease with the decrease of mean equivalence ratio. 3. Pressure rising rate of stratified mixture combustion increases with the decrease of the gradient of mixture at 0.4≤φ≤1.0. 4. In homogeneous condition, knocking intensity of smaller mean equivalence ratio is smaller. 5. With slight gradient, knocking intensities of same mean equivalence ratio are similar to that of homogeneous mixture. In excess of certain value of the gradient, knocking intensity is smaller as the gradient is larger.

scholarly journals Detonation effects of shallow buried explosive in sandy soil on target plate acceleration in a small-scale blast test

2018 ◽  
Vol 192 ◽  
pp. 02028
Author(s):  
Hassan Zulkifli Abu ◽  
Ibrahim Aniza ◽  
Mohamad Nor Norazman
Keyword(s):  
Sandy Soil ◽  
High Speed ◽  
Early Stage ◽  
Time History ◽  
Video Camera ◽  
Small Scale ◽  
Target Plate ◽  
Air Blast ◽  
High Speed Video Camera ◽  
The Impact

Small-scale blast tests were carried out to observe and measure the influence of sandy soil towards explosive blast intensity. The tests were to simulate blast impact imparted by anti-vehicular landmine to a lightweight armoured vehicle (LAV). Time of occurrence of the three phases of detonation phase in soil with respect to upward translation time of the test apparatus were recorded using high-speed video camera. At the same time the target plate acceleration was measured using shock accelerometer. It was observed that target plate deformation took place at early stage of the detonation phase before the apparatus moved vertically upwards. Previous data of acceleration-time history and velocity-time history from air blast detonation were compared. It was observed that effects of soil funnelling on blast wave together with the impact from soil ejecta may have contributed to higher blast intensity that characterized detonation in soil, where detonation in soil demonstrated higher plate velocity compared to what occurred in air blast detonation.

In Situ Observation Method for Quantitative Evaluation of Solidification Phenomena and Solidification Cracks during Welding

2014 ◽  
Vol 782 ◽  
pp. 3-7
Author(s):  
Kenji Shinozaki ◽  
Motomichi Yamamoto ◽  
Kohta Kadoi ◽  
Peng Wen
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Solidification Cracking ◽  
In Situ Observation ◽  
High Speed Video Camera ◽  
Varestraint Test ◽  
Solidification Cracks ◽  
Observation Method ◽  
Solidification Crack

Solidification cracking during welding is very serious problem for practical use. Therefore, there are so many reports concerning solidification cracking. Normally, solidification cracking susceptibility of material is quantitatively evaluated using Trans-Varestraint test. On the other hand, local solidification cracking strain was tried to measure precisely using in-situ observation method, called MISO method about 30 years ago. Recently, digital high-speed video camera develops very fast and its image quality is very high. Therefore, we have started to observe solidification crack using in site observation method. In this paper, the local critical strain of a solidification crack was measured and the high temperature ductility curves of weld metals having different dilution ratios and different grain sizes to evaluate quantitatively the effects of dilution ratio and grain size on solidification cracking susceptibility by using an improved in situ observation method.

Study on Magnetic Barrel Machine Equipped with Three-Dimensional Arrangement of Magnets

2007 ◽  
Vol 329 ◽  
pp. 761-766 ◽  
Author(s):  
Y. Zhang ◽  
Masato Yoshioka ◽  
Shin-Ichiro Hira
Keyword(s):  
High Speed ◽  
Permanent Magnets ◽  
Three Dimensional ◽  
Video Camera ◽  
High Speed Video ◽  
High Speed Video Camera ◽  
The Media ◽  
Set Up

At present, a commercially available magnetic barrel machine equipped with permanent magnets has some faults arising from constructional reason. That is, grinding or finishing ability is different from place to place in the machining region, resulting in the limitation on the region we can use in the container of workpieces. Therefore, in this research, authors made the new magnetic barrel machine equipped with three dimensional (3D) magnet arrangement to overcome these faults. The grinding ability of the new 3D magnetic barrel machine converted was experimentally examined, and compared with that of the traditional magnetic barrel machine. As a result, it was shown that we can use much broader region in the new 3D machine. It was also shown that the grinding ability became higher. The distribution of barrel media in action was recorded by means of a high speed video camera. It was clarified that the media rose up higher and were distributed more uniformly in the container by the effect of the magnet block newly set up. It was supposed that this must be the reason for the above-mentioned improvement of grinding ability.

Grease soap particles passing through an elastohydrodynamic contact under side slip conditions

2000 ◽  
Vol 214 (4) ◽  
pp. 317-325 ◽  
Author(s):  
P Eriksson ◽  
V Wikström ◽  
R Larsson
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Previous Investigation ◽  
Video Camera ◽  
Slip Conditions ◽  
High Speed Video ◽  
Elastohydrodynamic Contact ◽  
High Speed Video Camera ◽  
Pure Rolling ◽  
Minimum Film Thickness

In a previous investigation, grease thickener fibres were tracked as they passed through an elastohydrodynamic (EHD) contact in pure rolling using interferometry in a standard ball-and-disc apparatus. In order to capture single thickener fibres, a high-speed video camera was used. Here, the experiments have been repeated introducing different amounts of side slip for different rolling speeds and a faster video camera capable of capturing 4500 frames/s. The contact was lubricated with a continuous supply of grease. Two greases, based on the same synthetic poly(α-olefin) but thickened with Li-12-OH and lithium complex soap respectively, were studied. It was observed that the thickener fibres were stretched both before entering the contact and as they passed through it. Fibres seem to avoid the minimum film thickness regions and, if they enter, the film is restored immediately after passage.

Biomechanical Analysis of a World Record Javelin Throw: A Case Study

1985 ◽  
Vol 1 (1) ◽  
pp. 73-77 ◽  
Author(s):  
Robert J. Gregor ◽  
Marilyn Pink
Keyword(s):  
High Speed ◽  
Video Camera ◽  
The United States ◽  
Track And Field ◽  
Biomechanical Analysis ◽  
World Record ◽  
High Speed Video ◽  
High Speed Video Camera ◽  
Ongoing Project

As part of an ongoing project to evaluate elite track and field throwers in the United States, the javelin competition was filmed during the 1983 Pepsi Invitational Track Meet. A high-speed video camera (Spin Physics SP2000) was positioned orthogonal to the javelin runway to record the release of all throws. During this competition, Tom Petranoff’s world record (99.72 m) was filmed at 200 fields per second. Subsequent frame-by-frame digitization yielded results consistent with reports in the literature. Release velocity was 32.3 m/s and represents one of the highest values ever reported. Angle of release was .57r, javelin attitude at release was .64r» and angle of attack was .07r. While optimum values for these release parameters, in light of published results, remain open to discussion, the results presented here represent unique information on a world record performance and can serve as a basis of comparison for future performances.

Liquid Sheet Disintegration and Atomization Process on a Simplified Airblast Atomizer

1993 ◽  
Vol 115 (3) ◽  
pp. 461-466 ◽  
Author(s):  
G. Lavergne ◽  
P. Trichet ◽  
P. Hebrard ◽  
Y. Biscos
Keyword(s):  
High Speed ◽  
Swirling Flow ◽  
Video Camera ◽  
Frequency Instability ◽  
Liquid Sheet ◽  
Processing Unit ◽  
Spray Formation ◽  
High Speed Video Camera ◽  
The Mean ◽  
Component Phase

Liquid sheet break-up in coflowing shear flow is the mean by which liquids are atomized in practical injectors for gas turbine combustors. The present study explores experimentally the mechanisms of liquid sheet instabilities and spray formation. Experiments are conducted on four airblast geometries. A high-speed video camera associated with an image processing unit was used to study the liquid sheet instabilities. A microphone and a frequency analyzer were used to track the disintegration frequency. Instability amplitude and disintegration length of the liquid sheet were measured. A two-component Phase Doppler Particle Analyzer was used to characterize the resultant spray. The spatial distribution of the particle size is influenced by the swirling flow field. These experimental results will be used to assess models of fuel sheet instabilities and disintegration.

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