The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform

Jung-yeop Lee - One of the best experts on this subject based on the ideXlab platform.

  • Characteristics of ventilating flow generated by a rotating swirler in a vortex vent
    Journal of Fluids and Structures, 2011
    Co-Authors: Y.b. Lim, S.m. Lee, Jung-yeop Lee
    Abstract:

    Abstract A vortex ventilation system with a rotating annular disk installed coaxially with the Exhaust Inlet is a very effective local ventilator. A swirling flow generated by a rotating swirler makes the ventilation flow concentrated around the axis of rotation, which can increase the ventilation depth by a factor of five compared to a conventional Exhaust hood. Despite the well-documented excellent ventilation performance of such a system, detailed flow characteristics are not well understood. In this study, the swirling flow field in the vortex vent was tested, and a number of peculiar flow characteristics were observed. When the rotational speed was varied, a series of different flow patterns appeared, and the changes in the flow pattern showed rapid transition, hysteresis, and flow instability similar to the vortex. The transition of the flow pattern could be explained based on the ratio of the centrifugal force to Exhaust pressure. Hysteresis of the flow transition occurred in an unstable equilibrium mode between the two forces, and an unstable flow pattern occurred when the secondary recirculating flow was located beneath the swirler. A formula for the critical rotational speed was derived, which showed satisfactory agreement with experimental observation.

Jiang Xue-peng - One of the best experts on this subject based on the ideXlab platform.

  • Study on Effect of Configuration of Exhaust Inlets on Central Extraction with Top Exhaust System in Tunnel Fire
    Highway Engineering, 2013
    Co-Authors: Jiang Xue-peng
    Abstract:

    In order to obtain effect of configuration of Exhaust Inlets on central extraction system in tunnel fire,combing with fire smoke control engineering practice of a large underwater tunnel,the scale of fire was set and the array tunnel fire conditions were designed according to the tunnel actual traffic conditions.At the same time,tunnel model with the central Exhaust system was built by using the fire dynamics simulation software FDS.The smoke extraction effect index such as visibility at a distance of 2 m above the ground along the tunnel,smoke spreading distance and efficiency of smoke extraction was analyzed quantitatively.And then,the influence laws of the smoke extraction effect of configuration of Exhaust Inlets such as size of the single Exhaust Inlet,spacing,the opening number and shape of the single Exhaust valve on central extraction under uni-directional smoke Exhaust mode and bi-directional smoke Exhaust mode were obtained.The results showed that: the three factors of size of the single Exhaust Inlet,spacing and the number of opening Exhaust Inlet influence collectively smoke extraction effect whether uni-directional or bi-directional smoke Exhaust mode.The approach of blindly improving the effect of smoke extraction through the increase or decrease of a factor is not feasible;the smoke spreading distance under uni-directional smoke Exhaust mode is smaller than that under bi-directional smoke Exhaust mode.However,the total efficiency of the Exhaust Inlets is below that of the bi-directional smoke Exhaust when the same configuration of Exhaust Inlets such as size of the single Exhaust Inlet and spacing as well as the number of opening Exhaust Inlets is used.Simultaneously,the effect of smoke extraction is better when the shape of a single Exhaust is rectangle.

  • Optimization on smoke control in tunnel with lateral central extraction system
    Fire Science and Technology, 2013
    Co-Authors: Jiang Xue-peng
    Abstract:

    Lateral central extraction system was applied in a super long immersed road tunnel.For the smoke control engineering practice,temperature distribution,2 m height visibility conditions,smoke spread range,as well as Exhaust efficiency and other smoke effect indicators were quantitatively analyzed by FDS.The results showed that: when the fire source is located in-3% slope segment,fire power as 50 MW,reasonable longitudinally induced velocity is 2.5 m/s and the reasonable Exhaust Inlets opening solution is 1 upstream Exhaust Inlet / 4 downstream Exhaust Inlets.When the fire source is located in 0% slope segment,reasonable Exhaust program is two-way balanced smoke Exhaust,and 2 upstream opened Exhaust Inlets / 3 downstream opened Exhaust Inlets.At the same time the reasonable longitudinally induced velocity is 1.5 m/s.When the fire source is located in 3% slope segment,reasonable Exhaust program is one-way smoke Exhaust towards the downward,and 2 upstream opened Exhaust Inlets / 3 downstream opened Exhaust Inlets.At the same time the reasonable longitudinally induced velocity is 1 m/s.

  • Analysis of the affecting factors of the longitudinally induced velocity on the smoke control in highway tunnels
    Applied Mechanics and Materials, 2012
    Co-Authors: Jiang Xue-peng
    Abstract:

    The present paper is aimed at reporting our analysis results of the affecting factors of the longitudinally induced velocity on the smoke control in highway tunnels.For our research purpose,first of all,we have introduced the engineering practice that the central smoke extraction system to be used in a highway tunnel and ways on how to identify the reasonable longitudinally induced velocities under the likely-to-be induced fire scenarios,so as to establish a numerical analysis model of the highway tunnel based on the fire dynamics simulation software FDS.And,next,we have designed an array of the corresponding fire simulation conditions and ways to determine the fire size in a tunnel according to the actual tunnel traffic flow,the vehicle types,and the highway grades.As we know,the visibility at a distance of 2m above the ground along the tunnel,the smoke spreading distance in the longitudinal direction of the tunnel,and the smoke extraction efficiency of the Exhaust valves are but a few moat essential factors to be taken into account as the key evaluation indexes,except for the different longitudinally induced velocities to be taken into consideration in case of the tunnel fire involving the central smoke extraction system.Moreover,in such fire cases,it is necessary to come into mind how to deal with the problems,such as two-way balanced smoke or one-way smoke Exhaust towards the upward one-way or the downward one-way Exhaust,respectively.Take a 50 MW tunnel fire for example,different locations are to be taken into account if the fire is located in the central part of a tunnel,or 1 upstream Exhaust Inlet/5 downstream Exhaust Inlets or 2 upstream Exhaust Inlets/4 downstream Exhaust Inlets of the opened Exhaust Inlets.Based on such accounts,it would be possible to identify the reasonable longitudinally induced velocities according to the simulation results among the many choices.The results of the simulated conditions show that:the influence of different longitudinally induced velocities on the smoke control under the central smoke extraction system is of great significance.Moreover,under the specific size of fire,reasonable longitudinal induced velocities may have little difference if different Exhaust modes are respectively taken or when the fires are located in different spots.

Derek B. Ingham - One of the best experts on this subject based on the ideXlab platform.

Gary R. Hunt - One of the best experts on this subject based on the ideXlab platform.

  • The fluid mechanics of the Aaberg Exhaust hood
    1994
    Co-Authors: Gary R. Hunt
    Abstract:

    In this thesis an investigation of the fluid mechanics of the Aaberg Exhaust hood is presented. The Aaberg Exhaust hood is unique in its design as the speed of the air flow towards the Exhaust Inlet is enhanced by the entrainment of fluid into the hood's jet flow. The complex air flow pattern of the hood is governed by the Navier-Stokes equations. However, in this thesis modelling techniques have been developed in order to reduce the complexity of determining the fundamental air flow pattern. The modelling procedure adopted considers the hood's overall air flow to be composed of three component flows, namely, (i) the flow in the jet region, (ii) the jet-induced flow and (Ui) the suction flow. In practice the fluid flow pattern generated by the hood is such that the Reynolds number is very large, and hence the suction and jet-induced flows are modelled as potential flows with the boundary conditions governing the jet-induced flow coming from the solution of the shear-layer equations. This solution procedure enables the parameters which govern the hood's air flow to be identified and their effect on the flow produced by the hood may then be determined. Both two-dimensional and three-dimensional axisymmetric Exhaust designs have been examined and for the latter case a new numerical model for the axisymmetric radial flow of a fluid from the space between two identical concentric discs, for laminar and turbulent flows, has been developed. Agreement between the turbulent radial jet model developed and the results of numerous other established theoretical and experimental investigations is very good. The inviscid models for the overall air flow have been developed in terms of the stream functionand. except for in the simplest case considered where an analytical solution is possible. the equations of motion which govern the fluid flow in the region of interest have been solved numerically using finite-difference techniques. The models developed illustrate all of the flow phenomena observed experimentally and comparisons made between the predictions of both the two-dimensional and three-dimensional axisymmetric mathematical models and (i) the available experimental data and (ii) the commercially available CFD code FLUENT. which solves the full turbulent Navier-Stokes equations. show good agreement. thereby confirming the credibility of the cost-effective modelling approach adopted in this thesis.

  • Effects of Exhaust Inlet size on the fluid flow patterns created by an Aaberg Exhaust hood
    Journal of Aerosol Science, 1992
    Co-Authors: Gary R. Hunt, Derek B. Ingham
    Abstract:

    Abstract The aim of this paper is to investigate the effects of the size of the Exhaust Inlet on the fluid flow patterns created by an Aaberg Exhaust hood. Streamlines and lines of constant speed modelling those created by an Aaberg hood are used to examine the effect of the Inlet size on the size and profile of the hood's effective suction area.

J.m. Gonzalez - One of the best experts on this subject based on the ideXlab platform.

  • Development of a zirconia-mullite based ceramic for recuperator applications. DOE/ORNL Ceramic Technology Project
    1992
    Co-Authors: J.m. Gonzalez
    Abstract:

    GTE Products Corporation developed a compact ceramic high temperature recuperator for recovering heat from relatively clean Exhaust gases at temperatures up to 2500F. The DOE program allowed GTE to improve the technical and economic characteristics of the recuperator and stimulate industrial acceptance of the recuperator as an energy-saving technology. From January 1981 to December 1984, 561 recuperators were installed by GTE on new or retrofitted furnaces. With over 1200 units sold commercially between 1981 and 1990, GTE has documented the effect (long and short term) of corrosive attack from alkalies and lead. One objective of this contract was to develop Z-1000 a zirconia-mullite mixed oxide ceramic for use in ceramic recuperator applications susceptible to corrosion. To first and second pass of the ceramic recuperator would utilize the current cordierite-mixed-oxide ceramic. A Z-1000 matrix element would be used in the preheated air side`s third pass (Exhaust Inlet). Thermal stresses on Z-1000 cross flow module could be minimized by selecting appropriate heat transfer surface areas for each pass. A large surface area for first and second pass (cordierite section) could provide for sufficient heat transfer for 50% effectiveness. A surface area that generates minimal heat transfer in the third pass (Z-1000) sectionmore » is envisioned. Heat transferred in this section reduces the differential temperature across the matrix and the thermal stresses. Hence, thermal shock resistance of the material in the third pass becomes less critical; however, its corrosion resistance must be sufficient to withstand corrosive attack. This modular design could utilize a field repairable, disposable matrix. This report is concerned with process technology development for fabricating such a matrix, and a series of corrosion tests that established the potential corrosion resistance of the Z-1000 ceramic.« less

  • Development of a zirconia-mullite based ceramic for recuperator applications
    1992
    Co-Authors: J.m. Gonzalez
    Abstract:

    GTE Products Corporation developed a compact ceramic high temperature recuperator for recovering heat from relatively clean Exhaust gases at temperatures up to 2500F. The DOE program allowed GTE to improve the technical and economic characteristics of the recuperator and stimulate industrial acceptance of the recuperator as an energy-saving technology. From January 1981 to December 1984, 561 recuperators were installed by GTE on new or retrofitted furnaces. With over 1200 units sold commercially between 1981 and 1990, GTE has documented the effect (long and short term) of corrosive attack from alkalies and lead. One objective of this contract was to develop Z-1000 a zirconia-mullite mixed oxide ceramic for use in ceramic recuperator applications susceptible to corrosion. To first and second pass of the ceramic recuperator would utilize the current cordierite-mixed-oxide ceramic. A Z-1000 matrix element would be used in the preheated air side's third pass (Exhaust Inlet). Thermal stresses on Z-1000 cross flow module could be minimized by selecting appropriate heat transfer surface areas for each pass. A large surface area for first and second pass (cordierite section) could provide for sufficient heat transfer for 50% effectiveness. A surface area that generates minimal heat transfer in the third pass (Z-1000) sectionmore » is envisioned. Heat transferred in this section reduces the differential temperature across the matrix and the thermal stresses. Hence, thermal shock resistance of the material in the third pass becomes less critical; however, its corrosion resistance must be sufficient to withstand corrosive attack. This modular design could utilize a field repairable, disposable matrix. This report is concerned with process technology development for fabricating such a matrix, and a series of corrosion tests that established the potential corrosion resistance of the Z-1000 ceramic.« less