Research on the Combustion Characteristics of Small-Scaled Ethanol Pool Fire of Different Aspect Ratios

2011 ◽  
Vol 347-353 ◽  
pp. 1161-1165
Author(s):  
Cui Peng Kuang ◽  
Yuan Zhou Li ◽  
Shi Zhu ◽  
Shao Hua Mao
Keyword(s):  
Temperature Distribution ◽  
Aspect Ratio ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Pool Fire ◽  
Aspect Ratios ◽  
Fire Experiment ◽  
The Difference ◽  
Experimental Values ◽  
Centerline Temperature

Four groups of small-scaled ethanol pool fire experiment with different aspect-ratio(s) is undertaken, to gauge the mass loss rate of fuel as well as the plume centerline temperature distribution. Comparison of plume centerline temperature is made between the theoretical values estimated by Heskestad plume model and experimental results, which indicates that: with the increasing of s, the difference between theoretical values and experimental values tend to grow greater; and when s≈1, theoretical values and experimental values cohere well.

Evolution of pool fire plume characteristics during the depressurization process of an aircraft cargo compartment

2018 ◽  
Vol 36 (4) ◽  
pp. 362-375 ◽  
Author(s):  
Cong Li ◽  
Rui Yang ◽  
Yina Yao ◽  
Zhenxiang Tao ◽  
Hui Zhang
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Ambient Air ◽  
Pool Fire ◽  
Flame Height ◽  
Fire Plume ◽  
Activation Effect ◽  
Centerline Temperature ◽  
Ventilation Factor

This article presents an experimental investigation on the pool fire plume characteristics in a full-scale depressurized aircraft cargo compartment. The effects of decreasing pressure and vent flow rate on the fire characteristics such as flame shape, flame puffing, flame height, and centerline temperature were analyzed. The results show that during the depressurization process, the ventilation had an activation effect on the mass loss rate, and its increment had a linear relationship with the dimensionless ventilation factor. In addition, the larger depressurized rate caused the larger dimensionless ventilation factor and further resulted in the larger increment of mass loss rate. The flame puffing frequency was determined by the ratio of the gas density in the flame area of that in the ambient air, which increased with the drop of pressure. For flame centerline temperature, there was a counteraction area in the flame intermittent region, where the centerline temperature had almost no difference before and after the depressurization. The conclusions could provide the theoretical base and reference materials for the fire disaster in the cargo compartment of real aircrafts.

scholarly journals Experimental Study on the Cyclic Performance of Reinforced Concrete Shear Walls Exposed to Fire

2020 ◽  
Vol 14 (1) ◽  
Author(s):  
Eunmi Ryu ◽  
Heesun Kim ◽  
Yeongsoo Shin
Keyword(s):  
Temperature Distribution ◽  
Aspect Ratio ◽  
Failure Mode ◽  
Failure Modes ◽  
Shear Walls ◽  
Lateral Loads ◽  
Cyclic Performance ◽  
Concrete Wall ◽  
Aspect Ratios ◽  
Heated Area

AbstractThe purpose of this study was to investigate the thermal and cyclic behaviors of fire-damaged walls designed with different failure modes, aspect ratios and heated areas. These cyclic behaviors include temperature distribution, maximum lateral load, stiffness, ductility, and energy dissipations, etc. Toward this goal, the concrete wall specimens were exposed to heat following an ISO 834 standard time–temperature curve and the cyclic loading was applied to the fire-damaged walls. The test results showed that exposure to fire significantly reduced the cyclic performance of the RC walls. Especially, it was observed that heated area, designed failure mode, and aspect ratio have influences on maximum lateral loads, stiffness, and ductility of the fire-damaged walls, while almost no effects of the heated area, designed failure mode, and aspect ratio on temperature distribution and energy dissipation were found.

scholarly journals Environmental Influence on Stellar Evolution: The Horizontal Branch of NGC 1851

1996 ◽  
Vol 174 ◽  
pp. 357-358
Author(s):  
I. Saviane ◽  
G. Piotto ◽  
M. Capaccioli ◽  
F. Fagotto
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Environmental Influence ◽  
Mass Loss Rate ◽  
Bimodal Distribution ◽  
Age Difference ◽  
Horizontal Branch ◽  
Cluster Area ◽  
The Difference ◽  
Red Clump

The bimodal nature of the horizontal branch (HB) of NGC 1851 is known since Stetson (1981). In order to better understand the properties of its HB, we collected a set of data at the ESO-NTT telescope, which provides a full coverage of the cluster area. Additional archive images from the HST-WFPC camera have been used in order to study the central region. The resulting c-m diagram (CMD) for 20500 stars is presented in Fig. 1 (left). Despite its metallicity ([Fe/H]=−1.3), NGC 1851 presents a well defined blue HB tail, besides the expected red clump. The observed CMD has been compared with the synthetic ones. The bimodal HB can be reproduced assuming that there are two stellar populations in the cluster, with an age difference of ∼ 4 Gyr, hypothesis not supported by other properties of the CMD. On the other side, if we assume that the stars in NGC 1851 are 15 Gyr old (as suggested by the difference between the HB and the TO luminosities), only a bimodal mass loss can reproduce the HB morphology: only stars with higher than standard mass loss rate are able to populate the blue-HB (BHB) tail (Fig. 1,left). There are no observational evidences for a bimodal distribution of other parameters (He, CNO, etc.).

Experimental investigation of infrared signal characteristics in a micro-turbojet engine

2019 ◽  
Vol 123 (1261) ◽  
pp. 340-355 ◽  
Author(s):  
S. M. Choi ◽  
S. Kim ◽  
R. S. Myong ◽  
W. Kim
Keyword(s):  
Temperature Distribution ◽  
Aspect Ratio ◽  
Fuel Consumption ◽  
Engine Performance ◽  
Gas Temperature ◽  
Fuel Consumption Rate ◽  
Aspect Ratios ◽  
Turbojet Engine ◽  
Signal Characteristics ◽  
Cone Type

ABSTRACTInfrared signal measurements from a micro-turbojet engine are conducted to understand the characteristics of the engine performance and the infrared signal by varying the exhaust nozzle configuration. A cone type nozzle and five rectangle type nozzles whose aspect ratios vary from one to five are used for this experimental work. As a result, it is confirmed that the thrust and the fuel consumption rate of the engine do not change greatly by varying the exhaust nozzle shape. In the case of the aspect ratio of 5, the specific fuel consumption of the engine is increased by about 3% compared to the reference cone nozzle, but the infrared signal can be reduced by up to 14%. As a result of measuring the temperature distribution of the plume gas, the correlation of infrared signal with plume gas temperature distribution can be understood. In the case of a cone shape, the distribution of plume gas formed to circular shape, and the high-temperature core region of plume gas continued to develop farther to the downstream. However, the temperature distribution was maintained in the rectangular shape as the aspect ratio increased, and the average temperature decreased sharply. As the aspect ratio increases, the plume spreads more widely.

scholarly journals Dust Size Effect On IR Colors Of AGB Stars

2008 ◽  
Vol 4 (S252) ◽  
pp. 263-264
Author(s):  
Huan Wang ◽  
B. W. Jiang ◽  
R. Szczerba
Keyword(s):  
Size Effect ◽  
Loss Rate ◽  
Near Infrared ◽  
Mass Loss Rate ◽  
Mie Theory ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Agb Stars ◽  
Ir Sources ◽  
The Difference

AbstractWith the Mie theory and the radiative transfer model, we studied the effect of dust size on the infrared color indexes concerning special filters used in the space infrared missions and typical filters in the near-infrared, of AGB stars with typical oxygen-rich and carbon-rich dust shells. It is found the most affected bands are the near-infrared bands JHK and the Spitzer IRAC bands, meanwhile the wavebands with reference wavelength longer than 10 μm is little affected. The effect increases fast with the mass loss rate. We also discussed the potential to distinguish the O-rich and C-rich dusts, and the difference in IR colors between the AGB stars and other IR sources like YSOs and galaxies.

Design guidelines to mitigate distortion in material jetting specimens

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Kamran Kardel ◽  
Ali Khoshkhoo ◽  
Andres L. Carrano
Keyword(s):  
Aspect Ratio ◽  
Layer Thickness ◽  
Design Guidelines ◽  
Geometrical Parameters ◽  
Content Type ◽  
Build Orientation ◽  
Aspect Ratios ◽  
Wide Range ◽  
The Difference ◽  
Part Thickness

Purpose The purpose of this paper is to investigate the effects of layer thickness, aspect ratio, part thickness and build orientation on distortion to have a better understanding of its behavior in material jetting technology. Design/methodology/approach Specimens with two layer thicknesses (14 and 28 µm) were printed in two aspect ratios (2:1) and (10:1), four thickness values (1, 2, 3 and 4 mm) and three build orientations (45d, XY and YX) and scanned with a wide-area 3D surface scanner to quantify distortion. The material used to build the test specimens was a commercially available resin, VeroWhitePlus RGD835. Findings The results of this study showed that all printed specimens by material jetting 3D printers had some level of distortion. The 1-mm thickness specimens, for both layer thicknesses of 14 µm and 28 µm, showed a wide range of anomalies including reverse coil set (RCS), reverse cross bow (RCB), cross bow (CB), wavy edge (WE) and some moderate twisting (T). Similar occurrences were observed for the 2-mm thickness specimens as there were RCS, WE, RCB and T anomalies that show the difference between the thinner specimens (1- and 2-mm) with the thicker ones (3- and 4-mm). In both 3- and 4-mm thickness specimens, there was more consistency in terms of distortion with mainly RCS and RCB anomalies. In total, six different types of flatness anomalies were found to occur with the following incidences: reverse coil set (91 specimens, 63.19%), reverse cross bow (50 specimens, 34.72%), wavy edge (23 specimens, 15.97%), twist (19 specimens, 12.50%), coil set (11 specimens, 7.64%) and cross bow (7 specimens, 4.86%). Originality/value This study expands the research on how the preprocess parameters such as layer thickness and build orientation and the geometrical parameters such as part thickness and aspect ratio cause dimensional distortion. Distortion is a pervasive consequence of the curing process in photopolymerization and explores one of the most common defects that come across in polymeric-based additive manufacturing. In addition to the characterization of the type and magnitude of distortion, the contributions of this work also include establishing the foundation for design guidelines aiming at minimizing distortion in material jetting.

Combustion of Bio-Coke (Highly Densified Biomass Fuel) Block in High-Temperature Air Flow

2011 ◽  
Author(s):  
Hiroyuki Ito ◽  
Yuto Sakai ◽  
Tamio Ida ◽  
Yuji Nakamura ◽  
Osamu Fujita
Keyword(s):  
High Temperature ◽  
Temperature Distribution ◽  
Mass Loss ◽  
Air Temperature ◽  
Degradation Rate ◽  
Loss Rate ◽  
Ignition Delay Time ◽  
Mass Loss Rate ◽  
Air Flow ◽  
Air Flow Rate

Bio-coke (BIC, highly densified biomass briquette), a newly developed biomass fuel as an alternative to coal coke which utilized in blast furnace, is employed in this study. This fuel is manufactured in highly compressed and moderate temperature conditions and has advantages in its versatility of biomass resources, high volumetric calorific value and high mechanical strength. Japanese knotweed is chosen as a biomass resource and is shaped into cylinder (48 mm in diameter and 85 mm in length). One of the most important characteristics of BIC is its high apparent density (1300 kg/m3; twice or more than that of an ordinary wood pellet). In the present study, combustion characteristics of a single BIC fuel in high temperature air flow (473–873 K, 550–750 NL/min.) are investigated. Air is preheated and blown to the bottom surface of the BIC. Ignition and subsequent combustion behavior are observed with monitoring gas temperature near the BIC, surface and inside the BIC temperature, and time dependent mass loss of the BIC is measured. In the case with low air temperature, low heat flux from the fuel surface leads to the broad temperature distribution inside the BIC accompanied by the increase in ignition delay time and, then, once ignition takes place degradation rate becomes larger than the case with high temperature air. On the other hand, mass loss rate for the case of solid surface combustion in the high temperature air does not depend on the air temperature but does depend on the air flow rate, which is a result of reduced degradation rate relating to narrow temperature distribution in depth caused by short ignition delay time. Consequently, it is suggested that the history of preheating, i.e. the preheated condition which is determined by air temperature and air flow rate, is an essential factor to determine the ignition mode in the early stage of BIC combustion and the mass burning velocity in the period of main combustion with flame. It is found that the mass loss rate of BIC in the gas-phase combustion period increases with decrease in supplied air temperature in this study.

Finite Aspect Ratio Effects on Vortex Shedding Behind Two Cylinders at Angles of Incidence

1995 ◽  
Vol 117 (2) ◽  
pp. 219-226 ◽  
Author(s):  
D. M. Rooney ◽  
J. Rodichok ◽  
K. Dolan
Keyword(s):  
Wind Tunnel ◽  
Aspect Ratio ◽  
Vortex Shedding ◽  
Reynolds Numbers ◽  
Tip Vortex ◽  
Circular Cylinders ◽  
Aspect Ratios ◽  
Present Aspect ◽  
Shedding Frequency ◽  
The Difference

Wind tunnel tests were undertaken at subcritical Reynolds numbers to determine the vortex shedding characteristics behind a pair of finite circular cylinders at distances from one to six diameters apart and at all angles to one another. In addition, individual finite cylinders with aspect ratios 0.67 ≤ L/D ≤ 11.33 were examined to determine the effect of aspect ratio on shedding frequency, and to measure the frequency of the tip vortex when it is present. Aspect ratio was found to be a significant factor in the difference between shedding frequencies of the two cylinders at oblique angles. It was also found that “lock-on” of the two frequencies occurred when longer aspect ratio cylinders were upstream of shorter ones, but not in the reverse case.

scholarly journals Invariant Image-Based Currency Denomination Recognition Using Local Entropy and Range Filters

Entropy ◽  
2019 ◽  
Vol 21 (11) ◽  
pp. 1085 ◽  
Author(s):  
Hafeez Anwar ◽  
Farman Ullah ◽  
Asif Iqbal ◽  
Anees Ul Ul Hasnain ◽  
Ata Ur Ur Rehman ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Recognition Rate ◽  
Local Entropy ◽  
Aspect Ratios ◽  
Current Series ◽  
Step Procedure ◽  
Average Recognition Rate ◽  
Single Feature ◽  
Currency Note ◽  
The Difference

We perform image-based denomination recognition of the Pakistani currency notes. There are a total of seven different denominations in the current series of Pakistani notes. Apart from color and texture, these notes differ from one another mainly due to their aspect ratios. Our aim is to exploit this single feature to attain an image-based recognition that is invariant to the most common image variations found in currency notes images. Among others, the most notable image variations are caused by the difference in positions and in-plane orientations of the currency notes in images. While most of the proposed methods for currency denomination recognition only focus on attaining higher recognition rates, our aim is more complex, i.e., attaining a high recognition rate in the presence of image variations. Since, the aspect ratio of a currency note is invariant to such differences, an image-based recognition of currency notes based on aspect ratio is more likely to be translation- and rotation-invariant. Therefore, we adapt a two step procedure that first extracts a currency note from the homogeneous image background via local entropy and range filters. Then, the aspect ratio of the extracted currency note is calculated to determine its denomination. To validate our proposed method, we gathered a new dataset with the largest and most diverse collection of Pakistani currency notes, where each image contains either a single or multiple notes at arbitrary positions and orientations. We attain an overall average recognition rate of 99% which is very encouraging for our method, which relies on a single feature and is suited for real-time applications. Consequently, the method may be extended to other international and historical currencies, which makes it suitable for business and digital humanities applications.

Natural Convection Heat Transfer Through Inclined Longitudinal Slots

1984 ◽  
Vol 106 (4) ◽  
pp. 824-829 ◽  
Author(s):  
J. G. Symons ◽  
M. K. Peck
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Aspect Ratio ◽  
Convective Flow ◽  
Convection Heat Transfer ◽  
Flow Measurements ◽  
Transfer Rates ◽  
Isothermal Surface ◽  
Aspect Ratios ◽  
The Difference

The convective rates of heat transfer through inclined longitudinal slots is studied for the case where heat is transferred from a lower heated isothermal surface, through the slots, to an upper cooled isothermal surface. Experimental data are given for longitudinal slots having aspect ratios from 6–12, slot heights of 25–60 mm, inclinations from horizontal to vertical, and Ra < 107. Data are also given for a transverse slot of aspect ratio 6, for inclinations from horizontal to vertical, and Ra < 107. It is shown that convective heat transfer rates are essentially independent of slot orientation for inclinations up to 15 deg from the horizontal, but longitudinal slots are more effective in suppressing natural convection than transverse slots with the same aspect ratio, for inclinations from 24 to 75 deg from the horizontal. The difference in heat transfer rates for longitudinal and transverse slots inclined between 24 and 75 deg from the horizontal are shown to be due to different convective flows occurring in each slot. The heat flow measurements are supported by convective flow visualization experiments which demonstrate the modes of convective flow within slots.

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