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Article
Publication date: 8 July 2019

Mirosław Seredyński and Jerzy Banaszek

Proper selection of the stability parameter determines the accuracy of dendrite tip kinetics at a single crystal scale. Recently developed sophisticated phase field…

Abstract

Purpose

Proper selection of the stability parameter determines the accuracy of dendrite tip kinetics at a single crystal scale. Recently developed sophisticated phase field modelling of a single grain evolution provides evidence that this parameter is not constant during the process. Nevertheless, in the commonly used micro-macroscopic simulations of alloy solidification, it is a common practice to use a constant value of the stability parameter, resulting from the marginal stability theory. This paper aims to address the issue of how this inaccuracy in modelling crystal growth kinetics can influence numerically predicted zones of columnar and equiaxed dendrites and the macro-segregation formation.

Design/methodology/approach

Using the original authors’ micro-macroscopic computer simulation model of binary alloy solidification, the calculations have been performed for the Kurz-Giovanola-Trivedi (KGT) crystal growth kinetics with two different values of the stability parameter, and for two different compositions of Al-Cu alloys. The computational model is based on single domain-based formulation of transport equations, which are discretized on control-volume mesh. To identify zones of different grain structures, developing within the two-phase liquid-solid region, an envelope of columnar dendrite tips is tracked on a fixed non-orthogonal, triangular control volume grid. The models of porous and slurry media are used, along with the concept of the switching function, to account for diverse flow resistances in the columnar and equiaxed crystal zones. The numerical predictions are carefully studied to address the question of how the chosen stability parameter influences macroscopic structures of a cast, the most important issue from the engineering point of view.

Findings

The carried-out comprehensive numerical analysis shows that the value of the stability parameter of the KGT-constrained dendrite growth model does not have a direct significant impact on the macrosegregation formation. It, however, visibly influences the undercooling along the front, separating different dendritic structures and the size of the undercooled melt region where the equiaxed grains can develop. It also affects the amount of eutectic phase created.

Originality/value

To the best of the authors’ knowledge, this is the first attempt at estimating the influence of some inaccuracies, caused by possible ambiguities in choosing the stability constant of the KGT law, on numerically predicted macroscopic fields of solute concentration, the developing zones of columnar and equiaxed crystals and the macrosegregation patterns.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 2 May 2017

Mirosław Seredyński, Sara Battaglioli, Robin P. Mooney, Anthony J. Robinson, Jerzy Banaszek and Shaun McFadden

Numerical models of manufacturing processes are useful and provide insight for the practitioner; however, model verification and validation are a prerequisite for…

Abstract

Purpose

Numerical models of manufacturing processes are useful and provide insight for the practitioner; however, model verification and validation are a prerequisite for expedient application. This paper aims to detail the code-to-code verification of a thermal numerical model for the Bridgman solidification process of alloys in a two-dimensional axisymmetric domain, against an established commercial code (ANSYS Fluent); the work is considered a confidence building step in model development.

Design/methodology/approach

A grid sensitivity analysis is carried out to establish grid independence, and this is followed by simulations of two transient solidification scenarios: pulling rate step change and ramp input; the results of which are compared and discussed.

Findings

Good conformity of results is achieved; hence, the non-commercial model is code-to-code verified; in addition, the ability of the non-commercial model to deal with radial heat flow is demonstrated.

Originality/value

The ability of the home made model for Bridgman furnace solidification to deal with cases where significant radial heat transfer occurs in the sample was demonstrated. The introduction of front tracking to model the macroscopic growth of dendritic mush and the region of undercooled liquid is identified as the next step in model development.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 29 April 2014

Miroslaw Seredyński and Jerzy Banaszek

The purpose of this paper is to endorse the idea of using a special post-calculating front tracking (FT) procedure, along with the enthalpy-porosity front tracking (EP-FT…

Abstract

Purpose

The purpose of this paper is to endorse the idea of using a special post-calculating front tracking (FT) procedure, along with the enthalpy-porosity front tracking (EP-FT) single continuum model, in order to identify zones of different dendritic microstructures developing in the mushy zone during cooling and solidification of a binary alloy.

Design/methodology/approach

The 2D and 3D algorithms of the FT approach along with different crystal growth laws were implemented in macroscopic calculations of binary alloy solidification with the identification of different dendrite zones developing during the process.

Findings

Direct comparison of results predicted by the FT model with that based on the concept of the critical value of the solid volume fraction shows the sensitivity of the latter on an arbitrary assumed value of the dendrite coherency point (DCP). Moreover, for a carefully chosen DCP value the second model provides results that are close to those given by the FT-based approach. It is also observed that the macro-segregation pattern obtained by the proposed method is hardly influenced by chosen dendrite tip kinetics.

Originality/value

To the best authors’ knowledge, for the first time the 3D FT model has been used along with the enthalpy porosity approach to simulate the development of zones of different dendrite morphology during binary alloy solidification. And, a weak influence of assumed different dendrite tip kinetics on the macro-segregation pattern has been proved, what justifies this underlying assumption of the EP-FT method.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 24 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 22 May 2008

Piotr Furmański and Jerzy Banaszek

This paper aims to tackle the problem of some ambiguity of the momentum equation formulation in the commonly used macroscopic models of two‐phase solid/liquid region…

Abstract

Purpose

This paper aims to tackle the problem of some ambiguity of the momentum equation formulation in the commonly used macroscopic models of two‐phase solid/liquid region, developing during alloy solidification. These different appearances of the momentum equation are compared and the issue is addressed of how the choice of the particular form affects velocity and temperature fields.

Design/methodology/approach

Attention is focused on the ensemble averaging method, which, owing to its stochastic nature, is a new promising tool for setting up the macroscopic transport equations in highly inhomogeneous multiphase micro‐ and macro‐structures, with morphology continuously changing in time when the solidification proceeds. The basic assumptions of the two other continuum models, i.e. based on the classical mixture theory and on the volume‐averaging technique, are also unveiled. These three different forms of the momentum equation are then compared analytically and their impact on calculated velocity and temperature distribution in the mushy zone is studied for the selected test problem of binary alloy solidification driven by diffusion and thermal natural convection in a square mould.

Findings

It is found that a chosen appearance of the momentum equation mildly affects temporal velocity/temperature, and shapes of the phase interface at longer times of the solidification.

Research limitations/implications

This mainly results from small variations of the liquid fraction across the mushy zone and from a low solidification rate, and it may change drastically when anisotropic properties of the mushy zone, solutal convection, different phase densities and cooling conditions are considered. Therefore, further comprehensive study is needed.

Originality/value

The paper addresses how the different focus of the momentum equation for liquid flow is compared.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 18 no. 3/4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 29 April 2014

Piotr Łapka, Mirosław Seredyński, Piotr Furmański, Adam Dziubiński and Jerzy Banaszek

The purpose of this study is to developed a simplified thermo-fluid model of an engine cowling in a small airplane. An aircraft engine system is composed of different…

Abstract

Purpose

The purpose of this study is to developed a simplified thermo-fluid model of an engine cowling in a small airplane. An aircraft engine system is composed of different elements operating at various temperatures and in conjunction with the composite nacelle creates a region with high intensity of heat transfer to be covered by the cooling/ventilation systems. Therefore a thermal analysis, accounting for the complex heat transfer modes, is necessary in order to verify that an adequate cooling is ensured and that temperatures of the nacelle are maintained within the operating limits throughout the whole aircraft's flight.

Design/methodology/approach

Simplified numerical simulations of conductive, convective and radiative heat transfer in the engine bay of the small airplane I-23 in a tractor arrangement were performed for different air inlet and outlet configurations and for varying conditions existing in air inlets during the flight. The model is based on the control volume approach for heat and fluid flow as well as for thermal radiation and on k-ɛ turbulence model.

Findings

The flow and temperature distributions inside the cowling were determined, and high-temperature spots on the internal side of the nacelle and on other airplane systems located close to the turboprop engine and the exhaust system were found. The thermal radiation was found to play the key role in heat transfer inside the engine bay. The optimal configuration of air inlets and outlets was determined.

Practical implications

The obtained results will help in future studies on ventilation and cooling systems and will contribute to the selection of materials for parts of the engine bay and the nacelle as well as in developing solutions for reducing the temperature inside the cowling of the airplane I-23.

Originality/value

A complete simplified thermo-fluid model of heat transfer inside the engine bay of the airplane I-23 was developed. Additionally, influence of the thermal radiation on temperature distribution at the nacelle was investigated.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 86 no. 3
Type: Research Article
ISSN: 0002-2667

Keywords

Article
Publication date: 7 March 2016

Andrzej Iwaniuk, Witold Wiśniowski and Jerzy Żółtak

The purpose of this paper is to present application of multidisciplinary design optimisation (MDO) in redesign of a small composite aircraft. The redesign process was…

Abstract

Purpose

The purpose of this paper is to present application of multidisciplinary design optimisation (MDO) in redesign of a small composite aircraft. The redesign process was integration of the turboprop engine in a small composite aircraft. The process requires cooperation of specialists from many disciplines and definition of their tasks. For selected tasks, the authors present results of the calculation.

Design/methodology/approach

The authors used collaborative optimisation (CO) algorithm to solve the problem. They decomposed this complex process into a set of tasks in different engineering/research disciplines and used techniques and methods specific for each task (research/engineering discipline) to find a proper solution. The computer-aided design (CAD), computational fluid dynamics (CFD) and computational structural mechanics (CSM) commercial software were used as common tools as well as intentionally developed computer programmes were used as basic tools in some tasks, in particular, for aerodynamic optimisation, calculation of load and stability of aircraft. The exchange of data between separate tasks allowed achieving the main goal of complex design process.

Findings

Selected optimisation algorithm, CO, proved efficient for the authors’ purposes. The effectiveness of multidisciplinary optimisation depends as much on organisational parameters as it does on technical and technology parameters.

Practical implications

Multidisciplinary optimisation needs to be an integral part of analysis and design process. The successful optimisation results allowed to meet the requirements and to proceed to the next phase of work – preparing technical documentation for manufacturing the components necessary for integration of the airplane with the new engine.

Originality/value

Presented results of design process are a valuable example of how to achieve the final goal in an ongoing project.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 88 no. 2
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 29 April 2014

Wieńczysław Stalewski and Jerzy Żółtak

The purpose of this paper is to present the results of the preliminary design and optimization of the air-intake system and the engine nacelle. The work was conducted as…

Abstract

Purpose

The purpose of this paper is to present the results of the preliminary design and optimization of the air-intake system and the engine nacelle. The work was conducted as part of an integration process of a turboprop engine in a small aircraft in a tractor configuration.

Design/methodology/approach

The preliminary design process was performed using a parametric, interactive design approach. The parametric model of the aircraft was developed using the PARADES™ in-house software. The model assumed a high level of freedom concerning shaping all the components of aircraft important from the point of view of the engine integration. Additionally, the software was used to control the fulfillment of design constraints and to analyze selected geometrical properties. Based on the developed parametric model, the preliminary design was conducted using the interactive design and optimization methodology. Several concepts of the engine integration were investigated in the process. All components of the aircraft propulsion system were designed simultaneously to ensure their compliance with each other.

Findings

The concepts of the engine integration were modified according to changes in the design and technological constraints in the preliminary design process. For the most promising configurations, computational fluid dynamics (CFD) computations were conducted using commercial Reynolds-averaged Navier–Stokes solver FLUENT™ (ANSYS). The simulations tested the flow around the nacelle and inside the air-delivery system which consists of the air-intake duct, the foreign-particles separator and the auxiliary ducts delivering air to the cooling and air-conditioning systems. The effect of the working propeller was modeled using the Virtual Blade Model implemented in the FLUENT code. The flow inside the air-intake system was analyzed from the point of view of minimization of pressure losses in the air-intake duct, the quality of air stream delivered to the engine compressor and the effectiveness of the foreign particles separator.

Practical implications

Based on results of the CFD analyses, the final concept of the turboprop engine integration has been chosen.

Originality/value

The presented results of preliminary design process are valuable to achieve the final goal in the ongoing project.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 86 no. 3
Type: Research Article
ISSN: 0002-2667

Keywords

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