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1 – 10 of 577
Article
Publication date: 25 July 2019

Mehdi Bidabadi, Sadegh Sadeghi, Pedram Panahifar, Davood Toghraie and Alireza Rahbari

This study aims to present a basic mathematical model for investigating the structure of counter-flow non-premixed laminar flames propagating through uniformly-distributed organic…

Abstract

Purpose

This study aims to present a basic mathematical model for investigating the structure of counter-flow non-premixed laminar flames propagating through uniformly-distributed organic fuel particles considering preheat, drying, vaporization, reaction and oxidizer zones.

Design/methodology/approach

Lycopodium particles and air are taken as biofuel and oxidizer, respectively. Dimensionalized and non-dimensionalized forms of mass and energy conservation equations are derived for each zone taking into account proper boundary and jump conditions. Subsequently, to solve the governing equations, an asymptotic method is used. For validation purpose, results achieved from the present analysis are compared with reliable data reported in the literature under certain conditions.

Findings

With regard to the comparisons, although different complex non-homogeneous differential equations are solved in this paper, acceptable agreements are observed. Finally, the impacts of significant parameters including fuel and oxidizer Lewis numbers, equivalence ratio, mass particle concentration, fuel and oxidizer mass fractions and lycopodium initial temperature on the flame temperature, flame front position and flow strain rate are elaborately explained.

Originality/value

An asymptotic method for mathematical modeling of counter-flow non-premixed multi-zone laminar flames propagating through lycopodium particles.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Content available
Article
Publication date: 1 April 2003

39

Abstract

Details

Microelectronics International, vol. 20 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 27 March 2008

Maher M. Abou Al‐Sood and Madjid Birouk

The purpose of this paper is to develop a three‐dimensional (3D) numerical model capable of predicting the vaporization rate of a liquid fuel droplet exposed to a convective…

Abstract

Purpose

The purpose of this paper is to develop a three‐dimensional (3D) numerical model capable of predicting the vaporization rate of a liquid fuel droplet exposed to a convective turbulent airflow at ambient room temperature and atmospheric pressure conditions.

Design/methodology/approach

The 3D Reynolds‐Averaged Navier‐Stokes equations, together with the mass, species, and energy conservation equations were solved in Cartesian coordinates. Closure for the turbulence stress terms for turbulent flow was accomplished by testing two different turbulence closure models; the low‐Reynolds number (LRN) kε and shear‐stress transport (SST). Numerical solution of the resulted set of equations was achieved by using blocked‐off technique with finite volume method.

Findings

The present predictions showed good agreement with published turbulent experimental data when using the SST turbulence closure model. However, the LRN kε model produced poor predictions. In addition, the simple numerical approach employed in the present code demonstrated its worth.

Research limitations/implications

The present study is limited to ambient room temperature and atmospheric pressure conditions. However, in most practical spray flow applications droplets evaporate under ambient high‐pressure and a hot turbulent environment. Therefore, an extension of this study to evaluate the effects of pressure and temperature will make it more practical.

Originality/value

It is believed that the numerical code developed is of great importance to scientists and engineers working in the field of spray combustion. This paper also demonstrated for the first time that the simple blocked‐off technique can be successfully used for treating a droplet in the flow calculation domain.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 18 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 June 2001

B. Sorli, F. Pascal‐Delannoy, A. Foucaran, A. Giani and A. Boyer

This article describes a new humidity sensor using the technique of differential thermal analysis (DTA). The energy of water vaporisation is estimated via the measurement of the…

Abstract

This article describes a new humidity sensor using the technique of differential thermal analysis (DTA). The energy of water vaporisation is estimated via the measurement of the Seebeck voltage of miniature thermocouples used in differential mode on a Peltier module causing condensation from the ambient air. This sensor uses the sensitivity of alloys V2VI3 containing [Bi, Te, Sb, Se], 400‐440μV.K–1. Experimental measurements have been performed in a climatic chamber at constant temperature. The time variation of the differential Seebeck voltage with relative humidities HR varying from 10 to 90 per cent makes it possible to identify with precision the point of water evaporation. For each value of the relative humidity, it is directly a function of the condensate mass. The integration of these curves over time makes it possible to calculate the energy of vaporisation and the condensate mass.

Details

Sensor Review, vol. 21 no. 2
Type: Research Article
ISSN: 0260-2288

Keywords

Article
Publication date: 1 October 2018

Kaiwen Pang, Yaojun Li, Wei Yang and Zhuqing Liu

This study aims to develop and validate a new cavitation model that considers thermodynamic effects for high-temperature water flows.

Abstract

Purpose

This study aims to develop and validate a new cavitation model that considers thermodynamic effects for high-temperature water flows.

Design/methodology/approach

The Rayleigh–Plesset equation and “B-factor” method proposed by Franc are used to construct a new cavitation model called “thermodynamic Zwarte–Gerbere–Belamri” (TZGB) by introducing the thermodynamic effects into the original ZGB model. Furthermore, the viscous term of the Rayleigh–Plesset equation is considered in the TZGB model, and the model coefficients are formulated as a function of temperature. Cavitating flows around the NACA0015 hydrofoil under different water temperatures (25°C, 50°C and 70°C) at the angle of attack of 5° are calculated.

Findings

Results of the investigated temperatures show good agreement with the available experimental data. Given that the thermodynamic and viscosity effects are included in the TZGB model and the model coefficients are treated as a function of temperature, the TZGB model shows better performance in predicting the pressure coefficient distribution and length of cavity than the original ZGB cavitation model and other models do. The TZGB model aims to determine the thermodynamic and viscosity effects and perform better than the other models in predicting the mass transfer rate, particularly in high-temperature water.

Originality/value

The TZGB model shows potential in predicting the cavitating flows at high temperature and the computational cost of this model is similar to that of the original ZGB model.

Details

Engineering Computations, vol. 35 no. 6
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 29 September 2021

Yaasin Abraham Mayi, Alexis Queva, Morgan Dal, Gildas Guillemot, Charlotte Metton, Clara Moriconi, Patrice Peyre and Michel Bellet

During thermal laser processes, heat transfer and fluid flow in the melt pool are primary driven by complex physical phenomena that take place at liquid/vapor interface. Hence…

456

Abstract

Purpose

During thermal laser processes, heat transfer and fluid flow in the melt pool are primary driven by complex physical phenomena that take place at liquid/vapor interface. Hence, the choice and setting of front description methods must be done carefully. Therefore, the purpose of this paper is to investigate to what extent front description methods may bias physical representativeness of numerical models of laser powder bed fusion (LPBF) process at melt pool scale.

Design/methodology/approach

Two multiphysical LPBF models are confronted: a Level-Set (LS) front capturing model based on a C++ code and a front tracking model, developed with COMSOL Multiphysics® and based on Arbitrary Lagrangian–Eulerian (ALE) method. To do so, two minimal test cases of increasing complexity are defined. They are simplified to the largest degree, but they integrate multiphysics phenomena that are still relevant to LPBF process.

Findings

LS and ALE methods provide very similar descriptions of thermo-hydrodynamic phenomena that occur during LPBF, providing LS interface thickness is correctly calibrated and laser heat source is implemented with a modified continuum surface force formulation. With these calibrations, thermal predictions are identical. However, the velocity field in the LS model is systematically underestimated compared to the ALE approach, but the consequences on the predicted melt pool dimensions are minor.

Originality/value

This study fulfils the need for comprehensive methodology bases for modeling and calibrating multiphysical models of LPBF at melt pool scale. This paper also provides with reference data that may be used by any researcher willing to verify their own numerical method.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 32 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 15 July 2020

Wenbin Gao, Weifeng Huang, Tao Wang, Ying Liu, Zhihao Wang and Yuming Wang

By modeling and analyzing the two-phase mechanical seal of the fan-shaped groove end face, which is prone to phase change, an effective method to study the flow field of the…

Abstract

Purpose

By modeling and analyzing the two-phase mechanical seal of the fan-shaped groove end face, which is prone to phase change, an effective method to study the flow field of the mechanical seal when both cavitation and boiling exist simultaneously is found.

Design/methodology/approach

Based on the finite volume method, a fluid model was developed to investigate a two-phase mechanical seal. The validity of the proposed model was verified by comparing with some classical models.

Findings

By modeling and analyzing the two-phase mechanical seal of the fan-shaped groove end face, which is prone to phase change, the analysis of the gap flow field of the mechanical seal was realized when cavitation and boiling existed simultaneously.

Originality/value

Based on the model proposed for different conditions, the pressure and phase states in the shallow groove sealing gap were compared. The phase change rate between the mechanical seal faces was also investigated.

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2019-0537/

Details

Industrial Lubrication and Tribology, vol. 72 no. 10
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 1 April 1996

M. Glasmacher and H.‐J. Pucher

Laser Beam Micro Welding represents an alternative joining technique to the well known soldering processes. Hereby the leads are welded directly to the conducting tracks of the…

356

Abstract

Laser Beam Micro Welding represents an alternative joining technique to the well known soldering processes. Hereby the leads are welded directly to the conducting tracks of the circuit board. The advantages such as high temperature strength, reduced manufacturing time and simplified material separation at the end of the life‐cycle can be used successfully, if the drawbacks such as sensitive process behaviour are well controlled. To obtain this objective, the basic principles of laser beam heating and characteristic process stages of different micro welding scenarios are discussed. Applying simplified solutions of the equation of heat conduction, good parameter sets can be found for different welding applications. These examples show the potential of laser beam welding in the field of microelectronics.

Details

Microelectronics International, vol. 13 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 4 February 2014

Zhang Guoyuan and Yan Xiu-Tian

A hybrid bearing of advanced cryogenic rocket engine turbopump is designed. For cryogenic fluid propellants (such as liquid oxygen) as the lubrication of bearing, bearings…

Abstract

Purpose

A hybrid bearing of advanced cryogenic rocket engine turbopump is designed. For cryogenic fluid propellants (such as liquid oxygen) as the lubrication of bearing, bearings operating close to liquid-vapor region (near the critical point or slightly sub-cooled) are likely to develop a two phase flow region. The paper aims to discuss these issues.

Design/methodology/approach

In this paper, an all liquid, liquid-vapor mixture, and all vapor, i.e. a continuous vaporization bulk flow model of density and viscosity for mixture fluid, is presented, and the general Reynolds equation and energy equation with two phase flow as lubricants is solved. The static and dynamic performance of a 50-mm-radius hybrid bearing are obtained under 20,000 rpm speed and 10 MPa supply pressure.

Findings

The results show that the variations of performance of bearing operating under cryogenic liquid oxygen are not bounded by the all liquid and all vapor cases in the liquid-vapor mixture range. There behaviours are attributed to the large change in the compressibility character of the flow.

Research limitations/implications

For validating the correctness of analytical model, an experimental study on the liquid-vapor nitrogen mixture lubricated hybrid journal bearings is being carried out where low-viscosity nitrogen was selected as the lubricant for the sake of safety. Soon after, the authors will discuss the results and publish them in the new papers.

Originality/value

An all liquid, liquid-vapor mixture, and all vapor, i.e. a continuous vaporization bulk flow model of density and viscosity for mixture fluid, is presented. The static and dynamic performance of hybrid bearings with two phase flow as lubricants are obtained.

Details

Industrial Lubrication and Tribology, vol. 66 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 1 December 1963

1963—the year of reports. When looking back there is a tendency to associate a particular year with a specific occurrence or happening. Some years are easy to label in this way;…

Abstract

1963—the year of reports. When looking back there is a tendency to associate a particular year with a specific occurrence or happening. Some years are easy to label in this way; for example, 1939 was the year of the war, 1945 the year of the peace and so on. What about 1963? We have already labelled it in our mind as ‘the year of the reports’. Admittedly they have been sandwiched into the latter half of the year but we are beginning to feel that life without either discussion of a presented report or expectation of a new report is not normal.

Details

Anti-Corrosion Methods and Materials, vol. 10 no. 12
Type: Research Article
ISSN: 0003-5599

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