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Article
Publication date: 23 September 2022

Hang-Wei Wan, Yu-Quan Wen and Qi Zhang

The reaction dynamics of combustible clouds at high temperatures and pressures are a common form of energy output in aerospace and explosion accidents. The cloud explosion process…

Abstract

Purpose

The reaction dynamics of combustible clouds at high temperatures and pressures are a common form of energy output in aerospace and explosion accidents. The cloud explosion process is often affected by the external initial conditions. This study aims to numerically study the effects of airflow velocity, initial temperature and fuel concentration on the explosion behavior of isopropyl nitrate/air mixture in a semiconstrained combustor.

Design/methodology/approach

The discrete-phase model was adopted to consider the interaction between the gas-phase and droplet particles. A wave model was applied to the droplet breakup. A finite rate/eddy dissipation model was used to simulate the explosion process of the fuel cloud.

Findings

The peak pressure and temperature growth rate both decrease with the increasing initial temperature (1,000–2,200 K) of the combustor at a lower airflow velocity. The peak pressure increases with the increase of airflow velocity (50–100 m/s), whereas the peak temperature is not sensitive to the initial high temperature. The peak pressure of the two-phase explosion decreases with concentration (200–1,500 g/m3), whereas the peak temperature first increases and then decreases as the concentration increases.

Practical implications

Chain explosion reactions often occur under high-temperature, high-pressure and turbulent conditions. This study aims to provide prevention and data support for a gas–liquid two-phase explosion.

Originality/value

Sustained turbulence is realized by continuously injecting air and liquid fuel into a semiconfined high-temperature and high-pressure combustor to obtain the reaction dynamic parameters of a two-phase explosion.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 August 2016

Bingyou Jiang, Zegong Liu, Shulei Shi, Feng Cai, Jian Liu, Mingyun Tang and Baiquan Lin

The purpose of this paper is to understand a flameproof distance necessary to avoid the flame harms to underground personnel which may have great significance to the safety of…

Abstract

Purpose

The purpose of this paper is to understand a flameproof distance necessary to avoid the flame harms to underground personnel which may have great significance to the safety of underground personnel and the disaster relief of gas explosions in coal mines.

Design/methodology/approach

Through a roadway with a length of 100 m and a cross-section area of 80 mm×80 mm, the flame propagation of premixed methane-air deflagrations were simulated by using AutoReaGas software for various fuel concentrations (7, 8, 9.5, 11, and 14 percent), fuel volumes (0.0128, 0.0384, 0.064, and 0.0896 m3), initial temperatures (248, 268, 288, 308, and 328 K), and initial pressures (20, 60, 101.3, 150, and 200 kPa).

Findings

The maximum combustion rate for each point follows a changing trend of increasing and decreasing with the distance increasing from the ignition source, and it increases with the fuel volume increasing or the initial pressure increasing, and decreases with the initial temperature increasing. However, increasing the initial temperature increases the flame arrival time for each point. The flameproof distance follows a changing trend of increasing and decreasing with the fuel concentration increasing, and it linearly increases with the fuel volume increasing or the initial temperature increasing. However, the flameproof distances are all 17 m for various initial pressures.

Originality/value

Increasing initial temperature increases flame arrival time for each test point. Flameproof distance increases and then decreases with fuel concentration increasing. Increasing fuel volume or initial temperature linearly increases flameproof distance. Initial pressure has little impact on the flameproof distance.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 15 October 2018

Xin Zhao, Bo Dong and Weizhong Li

The freezing phenomenon of a falling droplet is a frequently encountered phenomenon in various applications, such as spray crystallization, hail formation and artificial…

Abstract

Purpose

The freezing phenomenon of a falling droplet is a frequently encountered phenomenon in various applications, such as spray crystallization, hail formation and artificial snowmaking. Therefore, this paper aims to understand the freezing processes of a falling droplet without and with initial horizontal velocity in a cold space.

Design/methodology/approach

The freezing processes of a falling droplet were characterized using a modified enthalpy-based lattice Boltzmann method.

Findings

The temperature field, streamlines and freezing process of the falling droplet were investigated and analyzed. The lower part of the droplet was frozen earlier than the upper part. The freezing trend slowed down in the later stage of the freezing process. The droplet shape was related to the initial vertical velocity, nucleation temperature and initial horizontal velocity.

Originality/value

A modified enthalpy-based lattice Boltzmann method is proposed. In the model, the improved pseudo-potential model is used and the radiation is considered. This method was firstly used to simulate the freezing process of a falling droplet. By examining these freezing processes in detail, the freezing trend and the effect factors of droplet deformation and freezing time were obtained, respectively.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 10
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 8 February 2016

Yan Yin, Xingming Xiao, Jiusheng Bao, Jinge Liu, Yuhao Lu and Yangyang Ji

The purpose of this study is to establish a new temperature set for characterizing the frictional temperature rise (FTR) of disc brakes. The FTR produced by braking is an…

Abstract

Purpose

The purpose of this study is to establish a new temperature set for characterizing the frictional temperature rise (FTR) of disc brakes. The FTR produced by braking is an important factor which directly affects the tribological properties of disc brakes. Presently, most existing researches characterize the FTR only by several static parameters such as average temperature or maximum temperature, which cannot reflect accurately the dynamic characteristics of temperature variation in the process of braking. In this paper, a new temperature parameter set was extracted and the influences of braking conditions on these parameters were investigated by experiments.

Design/methodology/approach

First, several simulated braking experiments of disc brakes were conducted to reveal the dynamic variation rules and mechanisms of the FTR in braking. Second, the characteristic parameter subset of the FTR was extracted with five significant parameters, namely, initial temperature, average temperature, end temperature, maximum temperature and the ratio of maximum temperature time. Furthermore, the fitting parameter subset of the FTR was constructed based on the temperature rise curve. Finally, the influence and mechanisms of initial braking velocity and braking pressure on the new temperature parameter set were investigated through braking experiments.

Findings

This paper extracted a new temperature parameter set including a characteristic parameter subset and a fitting parameter subset and revealed the influences of braking conditions on it by experiments.

Originality/value

The results showed that the new temperature parameter set extracted in this paper can characterize the dynamic characteristics of disc brake’s FTR variations more objectively and comprehensively. The research results will provide a theoretical basis for extracting the fault feature of friction properties.

Details

Industrial Lubrication and Tribology, vol. 68 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 11 November 2013

Bo Zhao

The polymer air-drawing model of spunbonding nonwovens has been established. The influence of the density and the specific heat capacity of polymer melt at constant pressure…

Abstract

Purpose

The polymer air-drawing model of spunbonding nonwovens has been established. The influence of the density and the specific heat capacity of polymer melt at constant pressure changing with polymer temperature on the fiber diameter have also been studied. The paper aims to discuss these issues.

Design/methodology/approach

TDMA method is used to solve the difference equations.

Findings

It can be concluded that a lower polymer throughput rate, a higher polymer melt initial temperature, a higher air initial temperature, and a higher air initial velocity can all produce finer fibers.

Originality/value

The results also reveal the great potential for this research in the computer-assisted design of spunbonding technology.

Details

International Journal of Clothing Science and Technology, vol. 25 no. 6
Type: Research Article
ISSN: 0955-6222

Keywords

Article
Publication date: 1 October 2005

Takao Koshimizu, Hiromi Kubota, Yasuyuki Takata and Takehiro Ito

To clarify the physical working principle of refrigeration in basic pulse tube refrigerators (BPTRs).

Abstract

Purpose

To clarify the physical working principle of refrigeration in basic pulse tube refrigerators (BPTRs).

Design/methodology/approach

A numerical simulation was performed. Transient compressible NS equation was solved utilizing the TVD scheme coupled with energy equation.

Findings

The periodic flow and temperature field were obtained. The movement of the gas particles and heat transfer between the gas particles and wall were analyzed. These numerical results explained the mechanism of surface heat pumping (SHP) which is known as the working principle of refrigeration in BPTR.

Research limitations/implications

Pulse tube refrigerator (PTR) is classified into the third generation. BPTR is the first generation. It is needed to clarify the working principle of refrigeration in the second and third generation by analyzing heat and fluid flow in the tube.

Practical implications

A very useful source of information to understand the physical working principle of refrigeration in BPTR.

Originality/value

The mechanism of SHP was shown by analyzing the heat exchange between the gas particles and pulse tube wall.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 15 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 3 April 2019

Zhaoqiang Wang, Jun Cheng, Hong Ji, Shan Hu and Hao Chen

The purpose of this paper is to study the effects of single parameters for temperature characteristics of oil film in port plate pair and the relationship of calculated results…

Abstract

Purpose

The purpose of this paper is to study the effects of single parameters for temperature characteristics of oil film in port plate pair and the relationship of calculated results and experimental results under different viscosity.

Design/methodology/approach

The paper established the mathematical model of oil film of port plate pair, calculated the energy equation of port plate pair, simulated for the oil film and temperature distribution and selected different kinds of lubricants to analyze the calculated value and the experimental value.

Findings

The results show: temperature rise of port plate pair is reduced with the increase of oil viscosity; temperature rise of port plate pair is decreased with rise of initial oil film thickness; temperature rise of port plate pair is increased with the rise of cylinder body speed, inclination angle and sealing belt width; and through the comparison of calculated value and experimental value, under the same viscosity and cylinder speed, experimental results are bigger.

Originality/value

This paper used the methods that the temperature of port plate pair was calculated numerically, and the results were consistent with experimental results, so it can get high precision.

Details

Industrial Lubrication and Tribology, vol. 71 no. 4
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 27 May 2014

Bo Zhao

The air drawing model plays an important in spunbonding. The purpose of this paper is to study the influence of the density and the specific heat capacity of polymer melt at…

Abstract

Purpose

The air drawing model plays an important in spunbonding. The purpose of this paper is to study the influence of the density and the specific heat capacity of polymer melt at constant pressure changing with polymer temperature on the fiber diameter.

Design/methodology/approach

The air drawing model of the polypropylene polymer in a spunbonding process is presented and solved by introducing the numerical computation results of the air flow field of aerodynamic device.

Findings

The model prediction of the filament fiber diameter coincides well with the experimental data. The effects of the processing parameters on the filament fiber diameter are discussed. A lower polymer throughput rate, higher polymer melt temperature, higher primary air temperature, higher venturi gap, higher air suction speed, and higher quench pressure can all produce finer filament fiber.

Originality/value

The experimental results show that the agreement between the results and experimental data are very better, which verifies the reliability of these models. The results show great prospects for this research in the field of computer assisted design of spunbonding technology.

Details

International Journal of Clothing Science and Technology, vol. 26 no. 2
Type: Research Article
ISSN: 0955-6222

Keywords

Article
Publication date: 23 January 2023

Antonio Campo, Diego Celentano and Yunesky Masip

The purpose of this paper is to address unsteady heat conduction in two subsets of ordinary bodies. One subset consists of a large plane wall, a long cylinder and a sphere in one…

Abstract

Purpose

The purpose of this paper is to address unsteady heat conduction in two subsets of ordinary bodies. One subset consists of a large plane wall, a long cylinder and a sphere in one dimension. The other subset consists of a short cylinder and a large rectangular bar in two dimensions. The prevalent assumptions in the two subsets are: constant initial temperature, uniform surface heat flux and thermo-physical properties invariant with temperature. The engineering applications of the unsteady heat conduction deal with the determination of temperature–time histories in the two subsets using electric resistance heating, radiative heating and fire pool heating.

Design/methodology/approach

To this end, a novel numerical procedure named the enhanced method of discretization in time (EMDT) transforms the linear one-dimensional unsteady, heat conduction equations with non-homogeneous boundary conditions into equivalent nonlinear “quasi–steady” heat conduction equations having the time variable embedded as a time parameter. The equivalent nonlinear “quasi–steady” heat conduction equations are solved with a finite difference method.

Findings

Based on the numerical computations, it is demonstrated that the approximate temperature–time histories in the simple subset of ordinary bodies (large plane wall, long cylinder and sphere) exhibit a perfect matching over the entire time domain 0 < t < ∞ when compared against the rigorous exact temperature–time histories expressed by classical infinite series. Furthermore, using the method of superposition of solutions in the convoluted subset (short cylinder and large rectangular crossbar), the same level of agreement in the approximate temperature–time histories in the simple subset of ordinary bodies is evident.

Originality/value

The performance of the proposed EMDT coupled with a finite difference method is exhaustively assessed in the solution of the unsteady, one-dimensional heat conduction equations with prescribed surface heat flux for: a subset of one-dimensional bodies (plane wall, long cylinder and spheres) and a subset of two-dimensional bodies (short cylinder and large rectangular bar).

Article
Publication date: 3 September 2020

Morteza Jamshidi, Heydar Dashti NaserAbadi and Mohammadreza Oliaei

The high heat induced by fire can substantially decrease the load-bearing capacity, which is more critical in unprotected steel structures than concrete reinforced structures. One…

Abstract

Purpose

The high heat induced by fire can substantially decrease the load-bearing capacity, which is more critical in unprotected steel structures than concrete reinforced structures. One of the conventional steel structures is a steel-plate shear wall (SPSW) in which thin infill steel plates are used to resist against the lateral loads. Due to the small thickness of infill plates, high heat seems to dramatically influence the lateral load-bearing capacity of this type of structures. Therefore, this study aims to provide an investigation into the performance of SPSW with reduced beam section at high temperature.

Design/methodology/approach

In the present paper, to examine the seismic performance of SPSW at high temperature, 48 single-span single-story steel frames equipped with steel plates with the thicknesses of 2.64 mm, 5 mm and 7 mm and yield stresses of 85 MPa, 165 MPa, 256 MPa and 300 MPa were numerically modeled. Furthermore, their behavioral indices, namely, strength, stiffness, ductility and hysteresis behavior, were studied at the temperatures of 20, 458, 642 and 917? The simulated models in the present paper are based on the experimental specimen presented by Vian and Bruneau (2004).

Findings

The obtained results revealed that the high heat harshly diminishes the seismic performance of SPSW so that the lateral strength is reduced even by 95% at substantially high temperatures. Therefore, SPSW starts losing its strength and stiffness at high temperature such that it completely loses its capacity of strength, stiffness and energy dissipation at the temperature of 917? Moreover, it was proved that by separating the percentage of their participations variations of the infill plate in SPSW, their behavior and the bare frame can be examined even at high temperatures.

Originality/value

To the best of the authors’ knowledge, the seismic performance of SPSW at different temperatures has not been evaluated and compared yet.

Details

Journal of Structural Fire Engineering, vol. 11 no. 4
Type: Research Article
ISSN: 2040-2317

Keywords

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