Browsing by Author "Huang, LW"

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Droplet ignition in a high-temperature convective environment
(1997-04-01)
Huang, LW
;
Chen, CH
;
機械工程學系
;
Department of Mechanical Engineering
The behaviors of n-heptane droplet ignition in a high-temperature convective environment are studied numerically. Two cases are considered wherein one is a purely forced convection, and the other is a mixed convection. The ignition process can be divided into a heating-up evaporation, a nearly constant droplet-temperature evaporation and a constant droplet-temperature burning. During the heating-up evaporation stage, the droplet temperature rises sharply and the square of the diameter decreases slightly with time. In the next stage, the droplet remains at nearly constant temperature in a pure vaporization process. After ignition, an envelope flame appears and the droplet is in an augmented vaporization process. The d(2)-law still holds. In the mixed convection case, where the gravity effect is taken into consideration, the location of initiation of chemical reaction is closer to the droplet, the ignition takes place earlier, and the flame is subjected to more stretch. The fuel accumulation phenomenon is also identified and it results in a suppression of the fuel evaporation rate. Finally, several future extensions are proposed to further modify the combustion model. (C) 1997 by The Combustion Institute.
Film condensation of HCFC-22 on horizontal enhanced tubes
(1996-01-01)
Cheng, WY
;
Wang, CC
;
Hu, YZR
;
Huang, LW
;
機械工程學系
Experiments were conducted to study the condensation heat transfer characteristics of horizontal enhanced tubes. In the current experiment, six different enhanced tubes, including 26, 40 fpi low fin tubes and four three-dimensional-fin tubes, were tested. The working fluid used in the experiment was HCFC-22. Data were presented in the form of overall heat transfer coefficient at three working pressures, namely 1.32, 1.47 and 1.62 Mpa. In addition, the condensing heat transfer coefficients for the test tubes were obtained from the Wilson plot technique.
Numerical analysis of a burning droplet with internal circulation in a gravitational environment
(1998-07-01)
Huang, LW
;
Chen, CH
;
機械工程學系
;
Department of Mechanical Engineering
A theoretical analysis of steady burning droplets with internal circulation in the presence of normal atmosphere and gravity is presented. The normalized system governing the gas phase consists of the complete set of conservation equations in r-z coordinates and includes finite-rate global kinetics. For the liquid phase, it includes continuity and momentum conservation equations. Thermodynamic equilibrium is assumed along the gas-liquid interface, which is not stationary. A body-fitted grid generation technique is used to handle irregular boundaries. The parametric study is performed by changing droplet diameter. The induced convection flowfield is presented to demonstrate its interaction with the flame and the liquid flow motion. The predicted results show that there exists one, two, or three cells within the burning droplet, depending on its diameter. The occurrence of an extra cell is due to reverse flow in the gas phase generated by interaction of the induced flow and blowing velocity. Comparison with the case where internal flow is not considered, for a small droplet the effect of internal circulation on mass evaporation rate can be neglected. On the other hand the internal flow will increase the mass evaporation rate.
Similarity retrieval on video database based upon module operation
(1996)
Lo, CC
;
Huang, LW
;
交大名義發表
;
資訊管理與財務金融系註：原資管所+財金所
;
National Chiao Tung University
In this paper, we propose a method of retrieving videos from the video database based upon the temporal relationship among the objects in the video data. We transform each video, Vi, into a set of ordered triples, (Oi,Oj,Rij)s, where Oi and Oj are two symbolic objects and Rij is the temporal relationship between Oi and Oj. Then, we construct a hashing table from all the triples with their corresponding videos in the video database. Every ordered triple is assigned a prime number. Therefore, each video Vi can be transformed into a positive integer Pi. A query can be converted into a positive integer value Pq via the preconstructed hashing table. The answer to a query is a collection of videos, in fact a set of desired frames, such that their corresponding Pi's can be divided by Pq, i.e., the remainder of Pi/Pq is equal to 0. A video database query system is built based upon the proposed method. From complexity analysis, we notice that the query time is with order O(n), where n is the number of videos in the video database, as oppose to O(nm) of the query without module operation, where m is the average number of frames in a video.
Transient combustion of a heating droplet in a gravitational environment
(1996-06-01)
Huang, LW
;
Chen, CH
;
機械工程學系
;
Department of Mechanical Engineering
The transient combustion characteristics of a droplet suddenly exposed to the envelope flames in an atmospheric environment are studied numerically. Combustion can be divided into a droplet heating-up and a constant-droplet-temperature burning. The naturally-convective flow is not known a priori, but provided as part of the solution. During the heating-up stage, the temperature and evaporation rate of droplet increase sharply, and the square of diameter decreases slightly as time proceeds. In the following stage, the droplet temperature remains constant, the evaporation rate and droplet diameter decrease with time. The flowfield of natural convection is also presented to demonstrate its interaction with the flame and the transient process. Finally, the fuel accumulation phenomenon is identified and it results in an reduction of evaporation constant.
Transient combustion of a heating droplet in a gravitational environment
(1996-06-01)
Huang, LW
;
Chen, CH
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
The transient combustion characteristics of a droplet suddenly exposed to the envelope flames in an atmospheric environment are studied numerically. Combustion can be divided into a droplet heating-up and a constant-droplet-temperature burning. The naturally-convective flow is not known a priori, but provided as part of the solution. During the heating-up stage, the temperature and evaporation rate of droplet increase sharply, and the square of diameter decreases slightly as time proceeds. In the following stage, the droplet temperature remains constant, the evaporation rate and droplet diameter decrease with time. The flowfield of natural convection is also presented to demonstrate its interaction with the flame and the transient process. Finally, the fuel accumulation phenomenon is identified and it results in an reduction of evaporation constant.
Video retrieval using successive modular operations on temporal similarity
(2004-08-01)
Lo, CC
;
Wang, SJ
;
Huang, LW
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
A video retrieval system consists of two major subsystems for indexing and querying, respectively. In this paper, we propose a framework for retrieving video sequences using modular operations on temporal similarity. In the indexing process, the contents (objects) of a video sequence are used to build temporal triples representing temporal relationships between objects. For every temporal triple generated from different video sequences, a prime number is assigned to it by the proposed prime number assignment (PNA) algorithm. For each video sequence, a standing value is generated via its set of prime numbers. In the query process, successive modular operations (SMO) on the standing values are used to retrieve video sequences. Based on the PNA and the SMO, we built an experimental video retrieval system. From the simulation results, we notice that a query can be done in a linear time. (C) 2003 Elsevier B.V. All rights reserved.