The Experts below are selected from a list of 216 Experts worldwide ranked by ideXlab platform

Jianjun Liu - One of the best experts on this subject based on the ideXlab platform.

  • investigations on the coupling flow between full scale last stage steam turbine and low pressure Exhaust Hood
    Proceedings of the Institution of Mechanical Engineers Part A: Journal of Power and Energy, 2015
    Co-Authors: Jianjun Liu
    Abstract:

    In a condensing steam turbine, the last-stage turbine and the condenser are connected by the low-pressure axial-radial Exhaust Hood. The Exhaust Hood has a complex geometry to make the flow change direction by 90 degrees, while guiding the flow from the turbine to the condenser. During the operation, strong flow interactions between the turbine and the Exhaust Hood cause the flow pattern to become extremely complicated. The purpose of this paper is to investigate the coupling flow between the full-scale last-stage turbine and the low-pressure Exhaust Hood of a 600MW steam turbine under actual operation conditions. The simulational calculations of the flow through the last stage turbine and the Exhaust Hood were realized by coupling calculations of turbine stage and Exhaust Hood in an external iterative manner. Equilibrium wet steam was selected as the flow medium. The coupling flow fields under different operation conditions were simulated and analyzed. It is found that the distributions of the turbine exit flow fields at different circumferential locations vary remarkably. The profiles of swirl angle and total pressure distributions at the turbine outlet change with the decrease of the mass flowrate, which further influence the flow behavior in the Hood and lead to the reduction of the performance.

  • aerodynamic optimization of the diffuser towards improving the performance of turbine and Exhaust Hood
    Volume 1B: Marine; Microturbines Turbochargers and Small Turbomachines; Steam Turbines, 2014
    Co-Authors: Jianjun Liu, Sijing Zhou
    Abstract:

    Exhaust Hood of large steam turbines is designed to recover the leaving kinetic energy of the last stage turbine while guiding the flow from the turbine to the condenser, which is of great importance to the overall performance of the steam turbine. The influences imposed by the strong flow interactions between the last stage turbine and the non-axisymmetric Exhaust Hood have not been taken into account properly in the current Exhaust Hood design approaches. The purpose of this paper is to optimize the diffuser in order to guarantee the aerodynamic performance of the turbine and the Exhaust Hood under the operational conditions. Considering the flow interactions between the turbine and the Exhaust Hood, the profiles of the diffuser end-wall were improved. The coupled turbine and Exhaust Hood calculations and the experiments were carried out to validate the effects of the optimization. It’s found that the redesigned diffuser can enhance the pressure recovery ability of the Exhaust Hood and increase the power output of the last stage turbine.Copyright © 2014 by ASME

  • unsteady interactions between axial turbine and nonaxisymmetric Exhaust Hood under different operational conditions
    Journal of Turbomachinery-transactions of The Asme, 2012
    Co-Authors: Jianjun Liu, Sijing Zhou
    Abstract:

    The Exhaust system in condensing steam turbines is used to recover leaving kinetic energy of the last stage turbine, while guiding the flow from turbine to condenser. The flows in the Exhaust system and the turbine stage are fully coupled and inherently unsteady. The unsteady flow interactions between the turbine and the Exhaust system have a strong impact on the blade loading or blade aerodynamic force. This paper describes the unsteady flow interactions between a single-stage axial turbine and an Exhaust system. The experimental and numerical studies on the coupled flow field in the single-stage turbine and the Exhaust Hood model under different operational conditions have been carried out. Unsteady pressure at the turbine rotor blade, turbine outlet, and Exhaust outcasing are measured and compared with the numerical prediction. The details of unsteady flow in the Exhaust system with the whole annulus stator and rotor blade rows are simulated by employing the computational fluid dynamics software CFX-5. Results show that for the investigated turbine-Exhaust configuration the influence of the flow field in the Exhaust system on the unsteady blade force is much stronger than that of the stator and rotor interaction. The flow pattern in the Exhaust system changes with the turbine operational condition, which influences the unsteady flow in the turbine stage further. [DOI: 10.1115/1.4003647]

  • influences of inflow condition on non axisymmetric flows in turbine Exhaust Hoods
    Journal of Thermal Science, 2008
    Co-Authors: Jianjun Liu
    Abstract:

    The complex 3D flow in a steam turbine Exhaust Hood model with different inlet swirl and inlet total pressure radial distributions has been simulated by employing CFX-5 and analyzed in this paper. It’s found that the inlet tangential flow angle at hub has a negative effect on the Exhaust Hood performance, while a negative gradient of inlet total pressure radial distribution has a positive impact on the Hood performances. It’s also numerically confirmed that a proper distribution of total pressure at Hood inlet can successfully eliminate the negative effects caused by the inappropriate inlet swirl distribution and improve the Hood aerodynamic performance.

  • experimental and numerical investigation of interaction between turbine stage and Exhaust Hood
    Proceedings of the Institution of Mechanical Engineers Part A: Journal of Power and Energy, 2007
    Co-Authors: Jianjun Liu, Sijing Zhou
    Abstract:

    AbstractThe current article describes the experimental and numerical studies on the flow field in a coupled turbine stage and Exhaust Hood model. The low subsonic stage with 22 stator blades and 30 rotor blades is especially designed for the Hood model, which is a typical design for a 300/600 MW steam turbine. Velocity distributions at the inlet, outlet, and Hood exit stages, in addition to static pressure distributions at the diffuser tip and hub end-walls and at the Hood outer casing, are measured and compared with the numerical prediction. The flow details in the Exhaust system with the whole annulus stator and rotor blade rows are simulated by employing the computational fluid dynamics software. Good agreements between numerical and experimental results are demonstrated. It is found that the swirl angle profile and total pressure profile due to the upstream turbine stage at the diffuser inlet have an unfavourable effect on the Exhaust Hood performance.

Simon Hogg - One of the best experts on this subject based on the ideXlab platform.

  • the influence of inlet asymmetry on steam turbine Exhaust Hood flows
    Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2014
    Co-Authors: Zoe Burton, Simon Hogg, Grant Ingram
    Abstract:

    It has been widely recognized for some decades that it is essential to accurately represent the strong coupling between the last stage blades (LSB) and the diffuser inlet, in order to correctly capture the flow through the Exhaust Hoods of steam turbine low pressure cylinders. This applies to any form of simulation of the flow, i.e., numerical or experimental. The Exhaust Hood flow structure is highly three-dimensional and appropriate coupling will enable the important influence of this asymmetry to be transferred to the rotor. This, however, presents challenges as the calculation size grows rapidly when the full annulus is calculated. The size of the simulation means researchers are constantly searching for methods to reduce the computational effort without compromising solution accuracy. However, this can result in excessive computational demands in numerical simulations. Unsteady full-annulus CFD calculation will remain infeasible for routine design calculations for the foreseeable future. More computationally efficient methods for coupling the unsteady rotor flow to the Hood flow are required that bring computational expense within realizable limits while still maintaining sufficient accuracy for meaningful design calculations. Research activity in this area is focused on developing new methods and techniques to improve accuracy and reduce computational expense. A novel approach for coupling the turbine last stage to the Exhaust Hood employing the nonlinear harmonic (NLH) method is presented in this paper. The generic, IP free, Exhaust Hood and last stage blade geometries from Burton et al. (2012. “A Generic Low Pressure Exhaust Diffuser for Steam Turbine Research,”Proceedings of the ASME Turbo Expo, Copenhagen, Denmark, Paper No. GT2012-68485) that are representative of modern designs, are used to demonstrate the effectiveness of the method. This is achieved by comparing results obtained with the NLH to those obtained with a more conventional mixing-plane approach. The results show that the circumferential asymmetry can be successfully transferred in both directions between the Exhaust Hood flow and that through the LSB, by using the NLH. This paper also suggests that for Exhaust Hoods of generous axial length, little change in Cp is observed when the circumferential asymmetry is captured. However, the predicted flow structure is significantly different, which will influence the design and placement of the Exhaust Hood internal “furniture.”

  • the influence of condenser pressure variation and tip leakage on low pressure steam turbine Exhaust Hood flows
    Proceedings of the Institution of Mechanical Engineers Part A : journal of power and energy 2014 Vol.228(4) pp.370-379 [Peer Reviewed Journal], 2014
    Co-Authors: Zoe Burton, Grant Ingram, Simon Hogg
    Abstract:

    This paper aims to highlight the importance of the accurate computational modelling of both the inlet and outlet Exhaust Hood boundary conditions. The computations presented are calculated using th...

  • a novel method of coupling the steam turbine Exhaust Hood and the last stage blades using the non linear harmonic method
    (2013). Proceedings of the ASME turbo expo - Turbine technical conference and exposition 2013 : presented at the ASME 2013 turbo expo - Turbine techni, 2013
    Co-Authors: Zoe Burton, Grant Ingram, Simon Hogg
    Abstract:

    The Exhaust Hood of a steam turbine is a vital area of turbomachinery research its performance strongly influences the power output of the last stage blades. It is well known that accurate CFD simulations are only achieved when the last stage blades are coupled to the Exhaust Hood to capture the strong interaction. This however presents challenges as the calculation size grows rapidly when the full annulus is calculated. The size of the simulation means researchers are constantly searching of methods to reduce the computational effort without compromising solution accuracy. This work uses a novel approach, by coupling the last stage blades and Exhaust Hood by the Non-Linear Harmonic Method, a technique widely used to reduce calculation size in high pressure turbine blades and axial compressors. This has been benchmarked against the widely adopted Mixing Plane method. The test case used is the Generic Geometry, a representative Exhaust Hood and last stage blade geometry that is free from confidentiality and IP restrictions and for which first calculations were presented at last year’s conference [1]. The results show that the non-uniform Exhaust Hood inlet flow can be captured using the non-liner harmonic method, an effect not previously achievable with single passage coupled calculations such as the mixing plane approach. This offers a significant computational saving, estimated to be a quarter of the computation time compared with alternative methods of capturing the asymmetry with full annulus frozen rotor calculations.

  • a literature review of low pressure steam turbine Exhaust Hood and diffuser studies
    Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2013
    Co-Authors: Zoe Burton, Grant Ingram, Simon Hogg
    Abstract:

    This paper summarizes the findings from research studies carried out over the last 30 years, to better understand the flows in steam turbine low pressure Exhaust Hoods and diffusers. The work aims to highlight the areas where further study is still required. A detailed description of the flow structure is outlined and the influence of the last turbine stage and the Hood geometry on loss coefficient is explored. At present, the key challenge faced is numerically modeling the three-dimensional, unsteady, transonic, wet steam Exhaust Hood flow given the impractically high computational power requirement. Multiple calculation simplifications to reduce the computational demand have been successfully verified with experimental data, but at present there is no ‘best-practice’ approach to reduce the computational time for routine design exercises. This paper highlights the importance of coupling the Exhaust Hood to the last stage steam turbine blades to capture the interaction; ensuring the total pressure and swirl angle profiles, along with the tip leakage jet are accurately applied to the diffuser inlet. The nonaxial symmetry of the Exhaust Hood means it is also important to model the full blade annulus. More studies have emerged modeling the wet steam and unsteady flow effects, but more work is required in this area to fully understand the impact on the flow structure.

  • a generic steam turbine Exhaust diffuser with tip leakage modelling and non uniform Hood outlet
    The 10th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics ETC 10 Lappeenranta Finland 15-19 April 2013 [Conference proceedings], 2013
    Co-Authors: Zoe Burton, Grant Ingram, Simon Hogg
    Abstract:

    This paper advances the work of Burton et al. (2012) to highlight the significance of the last stage blade tip leakage jet on the flow structure in the low pressure (LP) steam turbine Exhaust Hood, widely regarded as being significant in other published research. The flow structure in the Exhaust Hood is distinctly asymmetric when the leakage jet is included due to the increased swirl. This paper offers the new contribution of the effect of the condenser on the flow structure within the Exhaust Hood. It has been shown that the pressure gradient at the condenser inlet due to the heating of the cooling water reduces the asymmetry caused by the tip leakage jet. Improvements have been made to Durham University’s public domain LP Exhaust diffuser with accompanying last stage blades geometry to include the flare of the casing.

Zoe Burton - One of the best experts on this subject based on the ideXlab platform.

  • the influence of inlet asymmetry on steam turbine Exhaust Hood flows
    Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2014
    Co-Authors: Zoe Burton, Simon Hogg, Grant Ingram
    Abstract:

    It has been widely recognized for some decades that it is essential to accurately represent the strong coupling between the last stage blades (LSB) and the diffuser inlet, in order to correctly capture the flow through the Exhaust Hoods of steam turbine low pressure cylinders. This applies to any form of simulation of the flow, i.e., numerical or experimental. The Exhaust Hood flow structure is highly three-dimensional and appropriate coupling will enable the important influence of this asymmetry to be transferred to the rotor. This, however, presents challenges as the calculation size grows rapidly when the full annulus is calculated. The size of the simulation means researchers are constantly searching for methods to reduce the computational effort without compromising solution accuracy. However, this can result in excessive computational demands in numerical simulations. Unsteady full-annulus CFD calculation will remain infeasible for routine design calculations for the foreseeable future. More computationally efficient methods for coupling the unsteady rotor flow to the Hood flow are required that bring computational expense within realizable limits while still maintaining sufficient accuracy for meaningful design calculations. Research activity in this area is focused on developing new methods and techniques to improve accuracy and reduce computational expense. A novel approach for coupling the turbine last stage to the Exhaust Hood employing the nonlinear harmonic (NLH) method is presented in this paper. The generic, IP free, Exhaust Hood and last stage blade geometries from Burton et al. (2012. “A Generic Low Pressure Exhaust Diffuser for Steam Turbine Research,”Proceedings of the ASME Turbo Expo, Copenhagen, Denmark, Paper No. GT2012-68485) that are representative of modern designs, are used to demonstrate the effectiveness of the method. This is achieved by comparing results obtained with the NLH to those obtained with a more conventional mixing-plane approach. The results show that the circumferential asymmetry can be successfully transferred in both directions between the Exhaust Hood flow and that through the LSB, by using the NLH. This paper also suggests that for Exhaust Hoods of generous axial length, little change in Cp is observed when the circumferential asymmetry is captured. However, the predicted flow structure is significantly different, which will influence the design and placement of the Exhaust Hood internal “furniture.”

  • the influence of condenser pressure variation and tip leakage on low pressure steam turbine Exhaust Hood flows
    Proceedings of the Institution of Mechanical Engineers Part A : journal of power and energy 2014 Vol.228(4) pp.370-379 [Peer Reviewed Journal], 2014
    Co-Authors: Zoe Burton, Grant Ingram, Simon Hogg
    Abstract:

    This paper aims to highlight the importance of the accurate computational modelling of both the inlet and outlet Exhaust Hood boundary conditions. The computations presented are calculated using th...

  • analysis of low pressure steam turbine diffuser and Exhaust Hood systems
    2014
    Co-Authors: Zoe Burton
    Abstract:

    This thesis concerns the computational modelling of low pressure (LP) steam turbine Exhaust Hood flows. A test case for LP last stage blades (LSBs) with a full aerodynamic definition and an accompanying Exhaust Hood was developed which is representative of current industrial practice. The test case geometry is freely available allowing other researchers to build on this work and is the first of its kind. Studies on this Durham Stage and Exhaust Hood Test Case showed the geometry produces a representative flow pattern and performance metrics comparable to other published research. Using the test case, the effect of condenser cooling water pressure gradient on the Hood flow was computed for the first time. A generic boundary condition was developed to represent the transverse condenser cooling water flow and, when applied to the test case, was shown to have a larger influence on the flow asymmetry within the Hood than the tip leakage jet. This thesis describes the first application of the non-linear harmonic (NLH) method to couple the LSBs to the Exhaust Hood. This method enabled the circumferential non-uniformity which develops in the Exhaust Hood to be transferred across the interface to the stage, in half the computational demand of the full annulus frozen rotor approach. The first review of the influence of inlet circumferential asymmetry on the Hood flow field highlighted that modelling its effect is not as crucial as indicated in the literature, unless the diffuser axial length is very compact or if off-design flows are to be studied. A series of recommendations and guidelines for the CFD modelling of steam turbine Exhaust Hood flows based on this work are supplied. Experimental validation of the Durham Stage and Exhaust Hood Test Case and a comparison of full unsteady studies with the NLH method should be the next steps in this research.

  • a novel method of coupling the steam turbine Exhaust Hood and the last stage blades using the non linear harmonic method
    (2013). Proceedings of the ASME turbo expo - Turbine technical conference and exposition 2013 : presented at the ASME 2013 turbo expo - Turbine techni, 2013
    Co-Authors: Zoe Burton, Grant Ingram, Simon Hogg
    Abstract:

    The Exhaust Hood of a steam turbine is a vital area of turbomachinery research its performance strongly influences the power output of the last stage blades. It is well known that accurate CFD simulations are only achieved when the last stage blades are coupled to the Exhaust Hood to capture the strong interaction. This however presents challenges as the calculation size grows rapidly when the full annulus is calculated. The size of the simulation means researchers are constantly searching of methods to reduce the computational effort without compromising solution accuracy. This work uses a novel approach, by coupling the last stage blades and Exhaust Hood by the Non-Linear Harmonic Method, a technique widely used to reduce calculation size in high pressure turbine blades and axial compressors. This has been benchmarked against the widely adopted Mixing Plane method. The test case used is the Generic Geometry, a representative Exhaust Hood and last stage blade geometry that is free from confidentiality and IP restrictions and for which first calculations were presented at last year’s conference [1]. The results show that the non-uniform Exhaust Hood inlet flow can be captured using the non-liner harmonic method, an effect not previously achievable with single passage coupled calculations such as the mixing plane approach. This offers a significant computational saving, estimated to be a quarter of the computation time compared with alternative methods of capturing the asymmetry with full annulus frozen rotor calculations.

  • a literature review of low pressure steam turbine Exhaust Hood and diffuser studies
    Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2013
    Co-Authors: Zoe Burton, Grant Ingram, Simon Hogg
    Abstract:

    This paper summarizes the findings from research studies carried out over the last 30 years, to better understand the flows in steam turbine low pressure Exhaust Hoods and diffusers. The work aims to highlight the areas where further study is still required. A detailed description of the flow structure is outlined and the influence of the last turbine stage and the Hood geometry on loss coefficient is explored. At present, the key challenge faced is numerically modeling the three-dimensional, unsteady, transonic, wet steam Exhaust Hood flow given the impractically high computational power requirement. Multiple calculation simplifications to reduce the computational demand have been successfully verified with experimental data, but at present there is no ‘best-practice’ approach to reduce the computational time for routine design exercises. This paper highlights the importance of coupling the Exhaust Hood to the last stage steam turbine blades to capture the interaction; ensuring the total pressure and swirl angle profiles, along with the tip leakage jet are accurately applied to the diffuser inlet. The nonaxial symmetry of the Exhaust Hood means it is also important to model the full blade annulus. More studies have emerged modeling the wet steam and unsteady flow effects, but more work is required in this area to fully understand the impact on the flow structure.

Yi Wang - One of the best experts on this subject based on the ideXlab platform.

  • study on ventilation performance of lateral Exhaust Hood under the influence of two high temperature buoyant jets
    Building and Environment, 2020
    Co-Authors: Yanqiu Huang, Yi Wang, Junwei Guo, Chunxiao Zhao, Yingni Zhai
    Abstract:

    Abstract Two high-temperature buoyant jets widely exist during the pouring process of molten metal. The lateral Exhaust Hood is usually used to capture contaminated airflow considering production process. However, the current flow ratio design method for the lateral Exhaust Hood is in consideration of a single pollution source. In this study, the applicability of the current flow ratio design method for controlling two high-temperature buoyant jets is analyzed. And the performance of lateral Exhaust Hood influenced by these two buoyant jets is investigated through model experiment and numerical simulation. Investigated factors are distances between two high-temperature buoyant jets, initial velocity ratios, and initial temperature ratios. The results show that the maximum capture efficiency is less than 60% when the optimal Exhaust flow rate for controlling the single-buoyant jet is doubled to control the two buoyant jets. Besides, with the distance ratio between the two buoyant jets increasing to 0.75, the two jets merge into one jet. Then, compared with that when the velocity ratio is 0.4, the dimensionless installation height of the lateral Exhaust Hood should be increased by about 0.04 when the velocity ratio is 1.0 and by about 0.12 when the velocity ratio is 1.4. Finally, with the temperature ratio increasing, the lateral Exhaust Hood flowrate should be increased to improve the capture efficiency instead of Exhaust Hood installation heights. In summary, the obtained conclusions could help develop high-efficiency ventilation systems and reduce the energy consumption of the industrial buildings.

  • study on limit flow ratio method for a lateral Exhaust Hood above high temperature buoyant jets
    Sustainable Cities and Society, 2020
    Co-Authors: Yanqiu Huang, Yi Wang, Chuang Jiang, Lei Cao, Yang Liu
    Abstract:

    Abstract A local lateral Exhaust Hood can be used to capture the contaminated airflow in the industrial production process. For the design of the lateral Exhaust Hood, the flow ratio method is commonly adopted. However, there are three major concerns in the existing calculation formula of the limit flow ratio for the lateral Exhaust Hood: 1 The influence of the horizontal width of the Hood is not considered. 2 The influence of the installation height of the Hood is not accurately presented. 3 The influence of temperature difference between polluted air flow and environment is not considered. By analyzing the variation of the limit flow ratio of the Hood with the above three different influencing factors, the existing calculation formula of the limit flow ratio for the lateral Exhaust Hood is corrected, and the limit flow ratio correction formula is obtained when the temperature difference Δt = 0∼1200 °C. Therefore, the improved formula of the limit flow ratio for a lateral Exhaust Hood could guide a more precise design of the Exhaust system, which is significant to save energy, ensure the workers’ health, and step into sustainable development.

  • performance of constant Exhaust ventilation for removal of transient high temperature contaminated airflows and ventilation performance comparison between two local Exhaust Hoods
    Energy and Buildings, 2017
    Co-Authors: Yanqiu Huang, Yi Wang, Li Liu, Peter V Nielsen, Rasmus Lund Jensen, Xiaoni Yang
    Abstract:

    Abstract Transient high-temperature contaminated airflows generated during the pouring of high-temperature materials are widespread in Chinese industrial plants. In this study, the performance of both the local Exhaust and the general Exhaust with a constant flow rate to remove these transient contaminants was experimentally investigated, and the ventilation performance was compared between two local Exhaust Hoods. This study focused on the dispersion and removal characteristics of contaminant concentrations under the conditions of high-temperature airflows. The results showed that the cumulative contaminant concentration could be divided into four time slots and that there was a time lag between the cumulative concentration of the local and general Exhaust. Additionally, the fitting formula of time-varying concentration decay was discussed to highlight the advantages of the designed Hood performance. Finally, the dynamic evaluation index ( TCRR t ) for evaluating Exhaust Hoods on removing transient contaminants was proposed, and the connections between the proposed index and the traditional capture efficiency were illustrated. The minimu m TCRR t for the improved Exhaust Hood was invariably greater than that for the existing Hood for each Hood flow rate. This study demonstrates that increasing the containment volume of the Exhaust Hood can help to remove transient high-temperature contaminants in industrial plants.

  • study of the vortex principle for improving the efficiency of an Exhaust ventilation system
    Energy and Buildings, 2017
    Co-Authors: Zhixiang Cao, Yi Wang, Mengjie Duan, Huaxin Zhu
    Abstract:

    Abstract In both industrial and civil buildings, local Exhaust ventilation systems are widely used in pollutant control. The efficiency of such systems has an important influence on indoor air quality and energy consumption. A tornado is a type of rotating vortex with strong suction force that can lift heavy weights into the atmosphere. This article presents a novel type of artificial vortex Exhaust device (AVED) using the principle of tornado-like vortex to improve the efficiency of local Exhaust system. The formation of a tornado-like vortex requires a circular updraft fed by air possessing angular momentum with respect to the updraft center axis. To understand the flow characteristics of AVED, the velocity distribution and pressure distribution are investigated by varying the following parameters via experimental methods: radius ratio, lifting ratio, control distances, velocity of the jets and flow rate of Exhaust Hood. The experimental results indicate that increasing the velocity of the jets is beneficial to forming vortex, and the appropriate range to form an optimal vortex of the radius ratio is 1 to 2, and that of the lifting ratio is 0.127 to 0.256. Compared to the ordinary canopy Exhaust Hood, AVED has at least twice the control distance while only requiring less than half the flow rate of the Exhaust Hood.

  • reduced scale experimental investigation on ventilation performance of a local Exhaust Hood in an industrial plant
    Building and Environment, 2015
    Co-Authors: Yanqiu Huang, Yi Wang, Li Liu, Peter V Nielsen, Rasmus Lund Jensen, Fanliao Yan
    Abstract:

    Abstract Local ventilation systems are widely used in industrial production processes to capture heat release and/or gaseous/particulate contaminants. The primary objective of this study was to determine important empirical factors on local pollutant capture efficiency and characteristics of thermal stratification in the working areas of industrial plants. Investigated factors were confined airflow boundaries, flow rates of the Exhaust Hoods, source strengths, airflow obstacles and distances between sources and Exhaust Hoods. Reduced-scale experiments were conducted with a geometric scale of 1:15 corresponding to a portion of the blast furnace workshop of a steel plant. The dependency of capture efficiency on Archimedes numbers was established. The results showed that confined airflow boundaries, flow rates of the Exhaust Hoods and source strengths were important empirical factors on pollutant capture efficiency. Hood performance was also evaluated by thermal stratification heights in the plants. This study could help improve the capture efficiency of local ventilation systems used in industrial plants. Safe operation heights are recommended in the upper space of industrial plants based on the thermal stratification in the plants.

Jianwu Chen - One of the best experts on this subject based on the ideXlab platform.

  • study on flow field characteristics of the 90 rectangular elbow in the Exhaust Hood of a uniform push pull ventilation device
    International Journal of Environmental Research and Public Health, 2018
    Co-Authors: Lindong Liu, Jianwu Chen, Xiaowei Luo, Jingwen Dai
    Abstract:

    A uniform push–pull ventilation device can effectively improve indoor air quality (IAQ). The 90° rectangular elbow is an important part of the push–pull ventilation device. This paper analyzes the flow field characteristics of the 90° rectangular elbows under different working conditions. This was done by using computational fluid dynamics (CFD) simulation (Fluent). The flow lines, velocity and pressure distribution patterns of the elbow flow field are revealed in detail. The wind velocity non-uniformity and wind pressure non-uniformity of the 90° rectangular elbows with different coefficients of radius curvature R and rectangular section height h are also compared. The results show that when R ≥ 2.5 h, the wind flow traces inside the elbow are basically parallel lines. At the same time, the average wind velocity and the average wind pressure are stable. Also, the wind velocity non-uniformity and wind pressure non-uniformity decrease with the increase of R. Therefore, considering the space and material loss caused by an increase in radius of curvature, the elbow with R = 2.5 h can be used as the best design structure for the 90° rectangular elbow, which is of great significance for improving the control effect of dust and toxic pollutants in a uniform push–pull ventilation device.

  • the application of jack software in the size study of the Exhaust Hood on a welding torch
    International Conference on Man-Machine-Environment System Engineering, 2018
    Co-Authors: Jianwu Chen, Zhenfang Chen, Bin Yang, Shasha Liang, Delei Zhao, Jinhui Tao
    Abstract:

    The Exhaust Hood on the welding torch can effectively capture the welding fume, but it may affect the worker’s vision. Take the commonly used gas protect welding torch as the tool model, and take the height and weight percent of 95 China male workers as the digital model of welder in this study. The static strength of welding with squatting posture was stimulated by the Static Strength Prediction tool in Jack software, and the best arm bending position in the squat welding was obtained. The influence of three different sizes of the Exhaust Hood on the welder’s field of vision was analyzed by the Vision Analysis tool in Jack software based on the result of the arm bending position, and the suitable size of the Exhaust Hood was determined from the visual angle. The results of the research and application were also discussed.

  • research on the axial velocity change rule of desktop slot Exhaust Hood
    Industrial Health, 2018
    Co-Authors: Jianwu Chen
    Abstract:

    The desktop slot Exhaust Hood has been widely used, but it is calculated by empirical formula. Axial velocity change rule of desktop slot Exhaust Hood can effectively provide the basis of the wind speed needed in order to control the poison. According to gas motion mathematical model, the geometry model and boundary conditions of desktop slot Exhaust Hood was established, and the influence of the Hood sizes to axial velocity were analyzed by Fluent simulation. The changes of relationship between the axial velocity (V) and the distance from the Hood mouth (L), the short edge of the Hood mouth (a), the long edge of the Hood mouth (b), the equivalent diameter of the Hood mouth (d) and the square root of the Hood mouth area (√A) were comparative analyzed by dimensionless processing. The result is the V/V0 with L/d have better change rule. The axial velocity change rule of different axial velocity were also analyzed using V/V0 with L/d change rule, and the change rule of V/V0 with L/d of desktop slot Exhaust Hood was obtained, which was verified by experiment.

  • Study on Flow Field Characteristics of the 90° Rectangular Elbow in the Exhaust Hood of a Uniform Push–Pull Ventilation Device
    MDPI AG, 2018
    Co-Authors: Lindong Liu, Jianwu Chen, Xiaowei Luo, Jingwen Dai
    Abstract:

    A uniform push⁻pull ventilation device can effectively improve indoor air quality (IAQ). The 90° rectangular elbow is an important part of the push⁻pull ventilation device. This paper analyzes the flow field characteristics of the 90° rectangular elbows under different working conditions. This was done by using computational fluid dynamics (CFD) simulation (Fluent). The flow lines, velocity and pressure distribution patterns of the elbow flow field are revealed in detail. The wind velocity non-uniformity and wind pressure non-uniformity of the 90° rectangular elbows with different coefficients of radius curvature R and rectangular section height h are also compared. The results show that when R ≥ 2.5 h, the wind flow traces inside the elbow are basically parallel lines. At the same time, the average wind velocity and the average wind pressure are stable. Also, the wind velocity non-uniformity and wind pressure non-uniformity decrease with the increase of R. Therefore, considering the space and material loss caused by an increase in radius of curvature, the elbow with R = 2.5 h can be used as the best design structure for the 90° rectangular elbow, which is of great significance for improving the control effect of dust and toxic pollutants in a uniform push⁻pull ventilation device