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Article
Publication date: 14 March 2020

Guiyue Kou, Xinghu Li, Yan Wang, Mouyou Lin, Chunsen Tan and Mingfei Mou

The purpose of this paper is to enhance film stiffness and control seal leakage of conventional spiral groove dry gas seal (S-DGS) at a high-speed condition by introducing a new…

Abstract

Purpose

The purpose of this paper is to enhance film stiffness and control seal leakage of conventional spiral groove dry gas seal (S-DGS) at a high-speed condition by introducing a new type superellipse surface groove.

Design/methodology/approach

The steady-state performance and dynamic characteristics of superellipse groove dry gas seal and S-DGS are compared numerically at a high-speed condition. The optimized superellipse grooves for maximum steady-state film stiffness and dynamic stiffness coefficient are obtained.

Findings

Properly designed superellipse groove dry gas seal provides remarkable larger steady-state film stiffness, dynamic stiffness coefficient and lower leakage rate at a high-speed condition compared to a typical S-DGS. The optimal values of first superellipse coefficient for maximum steady and dynamic stiffness are 1.3 and 1.4, whereas the optimal values of second superellipse coefficient for which are 1.4 and 2.0, respectively.

Originality/value

A new type of molded line, namely, superellipse curve, is proposed to act as the boundary lines of surface groove of dry gas seal, as an alternative of typical logarithm helix. The conclusions provide references for surface groove design with larger stiffness and lower leakage rate at a high-speed condition.

Details

Industrial Lubrication and Tribology, vol. 72 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 10 August 2021

Zehba Raizah and Abdelraheem M. Aly

The purpose of this paper is to perform numerical simulations based on the incompressible smoothed particle hydrodynamics (ISPH) method for thermo-diffusion convection in a…

Abstract

Purpose

The purpose of this paper is to perform numerical simulations based on the incompressible smoothed particle hydrodynamics (ISPH) method for thermo-diffusion convection in a hexagonal-shaped cavity saturated by a porous medium and suspended by a nano-encapsulated phase change material (NEPCM). Here, the solid particles are inserted into a phase change material to enhance its thermal performance.

Design/methodology/approach

Superellipse rotated shapes with variable lengths are embedded inside a hexagonal-shaped cavity. These inner shapes are rotated around their center by a uniform circular velocity and their conditions are positioned at high temperature and concentration. The controlling equations in a non-dimensional form were analyzed by using the ISPH method. At first, the validation of the ISPH results is performed. Afterward, the implications of a fusion temperature, lengths/types of the superellipse shapes, nanoparticles parameter and time parameter on the phase change heat transfer, isotherms, isoconcentration and streamlines were addressed.

Findings

The achieved simulations indicated that the excess in the length of an inner superellipse shape augments the temperature, concentration and maximum of the streamlines in a hexagonal-shaped cavity. The largest values of mean Nusselt number are attained at the inner rhombus shape with convex (n = 1.5) and the largest values of mean Sherwood number are attained at the inner rectangle shape with rounded corners (n = 4).

Originality/value

The ISPH method is developed to emulate the influences of the uniform rotation of the novel geometry shapes on heat/mass transport inside a hexagonal-shaped cavity suspended by NEPCM and saturated by porous media.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 32 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 February 1992

JOHN R. WILLIAMS and ALEX P. PENTLAND

This paper discusses advances in interactive discrete element simulation for use in computer‐aided concurrent design. We highlight the computational problems of creating a…

Abstract

This paper discusses advances in interactive discrete element simulation for use in computer‐aided concurrent design. We highlight the computational problems of creating a ‘virtual world’ populated by objects which behave much as real world objects and propose a system based on a new class of volumetric models, called superquadrics. These functions have significant advantages for calculating multibody interactions, and by coupling volumetric representation to a modal decomposition method for the physical dynamics we have been able to gain up to two orders of magnitude in efficiency. The modal method allows us to trade off high order modes for improved stability, time step magnitude, temporal aliasing and speed of response, and so provide almost real time feedback to the designer. We believe that virtual manufacturing systems will be especially useful in conceptual design, in design for manufacture and in the new thrust in concurrent design.

Details

Engineering Computations, vol. 9 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 19 December 2022

Darya Loenko, Hakan F. Öztop and Mikhail A. Sheremet

Nowadays, the most important challenge in mechanical engineering, power engineering and electronics is a development of effective cooling systems for heat-generating units. Taking…

Abstract

Purpose

Nowadays, the most important challenge in mechanical engineering, power engineering and electronics is a development of effective cooling systems for heat-generating units. Taking into account this challenge, this study aims to deal with computational investigation of thermogravitational energy transport of pseudoplastic nanoliquid in an electronic chamber with a periodic thermally producing unit placed on the bottom heat-conducting wall of finite thickness under an influence of isothermal cooling from vertical side walls.

Design/methodology/approach

The control equations formulated using the Boussinesq approach, Ostwald–de Waele power law and single-phase nanofluid model with experimentally based correlations of Guo et al. for nanofluid dynamic viscosity and Jang and Choi for nanofluid thermal conductivity have been worked out by the in-house computational procedure using the finite difference technique. The impact of the Rayleigh number, nanoadditives concentration, frequency of the periodic heat generation from the local element and thickness of the bottom solid substrate on nanoliquid circulation and energy transport has been studied.

Findings

It has been found that a raise of the nanoadditives concentration intensifies the cooling of the heat-generating element, while a growth of the heat-generation frequency allows reducing the amplitude of the heater temperature.

Originality/value

Mathematical modeling of a pseudoplastic nanomaterial thermogravitational energy transport in an electronic cabinet with a periodic thermally generating unit, a heat-conducting substrate and isothermal cooling vertical surfaces to identify the possibility of intensifying heat removal from a heated surface.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 3 July 2023

Hakan F. Oztop, Muhammed Gür, Fatih Selimefendigil and Hakan Coşanay

The purpose of this study is to do a numerical analysis of the jet to a body filled with phase change material (PCM). The melting of the PCM filled body was investigated by the…

Abstract

Purpose

The purpose of this study is to do a numerical analysis of the jet to a body filled with phase change material (PCM). The melting of the PCM filled body was investigated by the hot jet flow. Four different values of the Reynolds number were taken, ranging from 5 × 103 = Re = 12.5 103. Water, Al2O3 1%, Al2O3 2% and hybrid nanofluid (HNF; Al2O3–Ag mixture) were used as fluid types and the effects of fluid type on melting were investigated. At 60 °C, the jet stream was impinged on the PCM filled body at different Reynolds numbers.

Design/methodology/approach

Two-dimensional analysis of melting of PCM inserted A block via impinging turbulent slot jet is numerically studied. Governing equations for turbulent flow are solved by using the finite element method via analysis and system fluent R2020.

Findings

The obtained results showed that the best melting occurred when the Reynolds number increased and the HNF was used. However, the impacts of using alumina-water nanofluid were slight. At Re = 12,500, phase completion time was reduced by about 13.77% when HNF was used while this was only 3.93% with water + alumina nanofluid as compared to using only water at Re = 5,000. In future studies, HNF concentrations will change the type of nanoenhanced PCMs. In addition, the geometry and jet parameters of the PCM-filled cube can be changed.

Originality/value

Effects of impinging jet onto PCM filled block and control of melting via impinging hot jet of PCM. Thus, novelty of the work is to control of melting in a block by impinging hot jet and nanoparticles.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 10
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 9 December 2022

Fernando Tejero, David MacManus, Jesús Matesanz García, Avery Swarthout and Christopher Sheaf

Relative to in-service aero-engines, the bypass ratio of future civil architectures may increase further. If traditional design rules are applied to these new configurations and…

Abstract

Purpose

Relative to in-service aero-engines, the bypass ratio of future civil architectures may increase further. If traditional design rules are applied to these new configurations and the housing components are scaled, then it is expected that the overall weight, nacelle drag and the effects of aircraft integration will increase. For this reason, the next generation of civil turbofan engines may use compact nacelles to maximise the benefits from the new engine cycles. The purpose of this paper is to present a multi-level design and optimisation process for future civil aero-engines.

Design/methodology/approach

An initial set of multi-point, multi-objective optimisations for axisymmetric configurations are carried out to identify the trade-off between intake and fancowl bulk parameters of highlight radius and nacelle length on nacelle drag. Having identified the likely optimal part of the design space, a set of computationally expensive optimisations for three-dimensional non-axisymmetric configurations is performed. The process includes cruise- and windmilling-type operating conditions to ensure aerodynamic robustness of the downselected configurations.

Findings

Relative to a conventional aero-engine nacelle, the developed process yielded a compact aero-engine configuration with mid-cruise drag reduction of approximately 1.6% of the nominal standard net thrust.

Originality/value

The multi-point, multi-objective optimisation is carried out with a mixture of regression and classification functions to ensure aerodynamic robustness of the downselected configurations. The developed computational approach enables the optimisation of future civil aero-engine nacelles that target a reduction of the overall fuel consumption.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 May 1998

Caroline Hogue

When simulating the behaviour of granular assemblies and multi‐body systems using a discrete element analysis, the shape representation of the bodies and the contact detection…

1569

Abstract

When simulating the behaviour of granular assemblies and multi‐body systems using a discrete element analysis, the shape representation of the bodies and the contact detection algorithm greatly influence the flexibility, accuracy and efficiency of the simulation. Several geometrical shape descriptors of two and three dimensional arbitrary rigid bodies are reviewed and a flexible 3‐D descriptor introduced. The aim is to identify appropriate shape descriptors which allow a variety of types of bodies to be investigated while ensuring accurate and efficient detection of inter‐particle contacts. Polygons/polyhedrons, and continuous and discrete function representations are examined. The investigation favours discrete representations due to their efficiency and flexibility, but illustrates the elegance and efficiency of using a continuous function representation, e.g. a superquadric, to generate the discrete representation and simplify the contact detection process.

Details

Engineering Computations, vol. 15 no. 3
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 30 November 2021

Yuan Chen, Hao Shang, Xiaolu Li, Yuntang Li, Bingqing Wang and Xudong Peng

The purpose of this paper is to investigate the influence rule and mechanism of three degrees of freedom film thickness disturbance on the transient performance of spiral groove…

Abstract

Purpose

The purpose of this paper is to investigate the influence rule and mechanism of three degrees of freedom film thickness disturbance on the transient performance of spiral groove, upstream pumping spiral groove dry gas seal (UP-SDGS) and double-row spiral groove dry gas seal (DR-SDGS).

Design/methodology/approach

The transient performance of spiral groove, UP-SDGS and DR-SDGS are obtained by solving the transient Reynolds equation under different axial and angular disturbance coefficients. The transient and steady performance of the above-mentioned DGSs are compared and analyzed.

Findings

The film thickness disturbance has a remarkable impact on the sealing performance of DGS with different structures and the calculation deviations of the leakage rate of the UP-DGS will increase significantly if the film thickness disturbance is ignored. The axial and angular disturbance jointly affect the film thickness distribution of DGS, but there is no significant interaction between them on the transient sealing performance.

Originality/value

The influence mechanism of axial disturbance and angular disturbance on the transient performance of typical SDGSs behavior has been explained by theory. Considering small and large disturbance, the interaction between axial disturbance and angular disturbance on the transient performance have been studied.

Details

Industrial Lubrication and Tribology, vol. 74 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

Open Access
Article
Publication date: 25 October 2021

Junjie Lu

This study aims to study the gas film stiffness of the spiral groove dry gas seal.

Abstract

Purpose

This study aims to study the gas film stiffness of the spiral groove dry gas seal.

Design/methodology/approach

The present study represents the first attempt to calculate gas film stiffness in consideration of the slipping effect by using the new test technology for dry gas seals. First, a theoretical model of modified generalized Reynolds equation is derived with slipping effect of a micro gap for spiral groove gas seal. Second, the test technology examines micro-scale gas film vibration and stationary ring vibration to determine gas film stiffness by establishing a dynamic test system.

Findings

An optimum value of the spiral angle and groove depth for improved gas film stiffness is clearly seen: the spiral angle is 1.34 rad (76.8º) and the groove depth is 1 × 10–5 m. Moreover, it can be observed that optimal structural parameters can obtain higher gas film stiffness in the experiment. The average error between experiment and theory is less than 20%.

Originality/value

The present study represents the first attempt to calculate gas film stiffness in consideration of the slipping effect by using the new test technology for dry gas seals.

Details

Industrial Lubrication and Tribology, vol. 73 no. 10
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 17 March 2022

Lioua Kolsi, Fatih Selimefendigil and Mohamed Omri

The purpose of this study is to explore the phase change (PC) dynamics in a T-shaped ventilated cavity having multiple inlet and outlet ports during nanofluid convection with…

Abstract

Purpose

The purpose of this study is to explore the phase change (PC) dynamics in a T-shaped ventilated cavity having multiple inlet and outlet ports during nanofluid convection with phase change material (PCM) packed bed-installed system.

Design/Methodology/Approach

Finite element method was used to analyze the PC dynamics and phase completion time for encapsulated PCM within a vented cavity during the convection of nanoparticle loaded fluid. The study is performed for different Reynolds number of flow streams (Re1 and Re2 between 300 and 900), temperature difference (ΔT1 and ΔT2 between −5 and 10), aspect ratio of the cavity (between 0.5 and 1.5) and nanoparticle loading (between 0.02% and 0.1%).

Findings

It is observed that phase transition can be controlled by assigning different velocities and temperatures at the inlet ports of the T-shaped cavity. The PC becomes fast especially when the Re number and temperature of fluid in the port vary closer to the wall (second port). When the configurations with the lowest and highest Re number of the second port are considered up to 54.7% in reduction of complete phase transition time is obtained, while this amount is 78% when considering the lowest and highest inlet temperatures. The geometric factor which is the aspect ratio has also affected the flow field and PC dynamics. Up to 78% reduction in the phase transition time is obtained at the highest aspect ratio. Further improvements in the performance are achieved by using nanoparticles in the base fluid. The amounts in the phase transition time reduction are 8% and 10.5% at aspect ratio of 0.5 and 1.5 at the highest nanoparticle concentration.

Originality/Value

The thermofluid system and offered control mechanism for PC dynamics control can be considered for the design, optimization, further modeling and performance improvements of applications with PCM installed systems.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 32 no. 11
Type: Research Article
ISSN: 0961-5539

Keywords

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