Numerical assessment of miniaturized cold spray nozzle for additive manufacturing

2019 ◽  
Vol 29 (7) ◽  
pp. 2277-2296 ◽  
Author(s):  
Gus Nasif ◽  
R.M. Barron ◽  
Ram Balachandar ◽  
Julio Villafuerte
Keyword(s):  
Heat Transfer ◽  
Additive Manufacturing ◽  
Mach Number ◽  
Compressible Flow ◽  
Cold Spray ◽  
Thermal Characteristics ◽  
Spray Nozzle ◽  
Content Type ◽  
Adiabatic Approach ◽  
Scaling Down

Purpose Application of cold spray technology may exhibit significant benefits for the additive manufacturing process, particularly for producing intricate objects. To ascertain the feasibility of such an application, this paper aims to present a numerical investigation of the effect of scaling down a convergent-divergent (de Laval) nozzle, which is typically used in the cold spray industry, on the compressible flow parameters and thermal characteristics. Design/methodology/approach The Navier–Stokes equations and energy equation governing compressible flow are numerically solved using a finite volume method with a coupled solver. The conjugate heat transfer technique is used to couple fluid and solid heat transfer domains and predict the local heat transfer coefficient between the solid and fluid. The use of various RANS turbulence models has also been investigated to quantify the effect of the turbulence model on the simulation. Findings The numerical results reveal that the flow and thermal characteristics are altered as the convergent-divergent nozzle is scaled down. The static pressure and temperature profiles at any section in the nozzle are shifted toward higher values, while the Mach number profile at any section in the nozzle is shifted toward a lower Mach number. The turbulent kinetic energy at the nozzle exit increases with the scaling down of the nozzle geometry. This study also provides convincing evidence that the adiabatic approach is still suitable even though the temperature of the nozzle wall is extremely high, as required for industrial application. Results indicate that it is feasible to use the available capabilities of the cold spray technology for additive manufacturing after scaling down the nozzle. Originality/value The idea of adopting cold spray technology for additive manufacturing is new and innovative. To develop this idea into a viable commercial product, a thorough understanding of the flow physics within a cold spray nozzle is required. The simulation results discussed in this paper demonstrate the effect that scaling down of a convergent-divergent nozzle has on the flow characteristics in the nozzle.

Numerical study of heat transfer characteristics in positional wire and arc additive manufacturing

2020 ◽  
Vol 26 (9) ◽  
pp. 1627-1635
Author(s):  
Dongqing Yang ◽  
Jun Xiong ◽  
Rong Li
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Additive Manufacturing ◽  
Temperature Distribution ◽  
Finite Element Model ◽  
Heat Dissipation ◽  
Element Model ◽  
Heat Transfer Characteristics ◽  
Content Type ◽  
Thin Walled

Purpose This paper aims to fabricate inclined thin-walled components using positional wire and arc additive manufacturing (WAAM) and investigate the heat transfer characteristics of inclined thin-walled parts via finite element analysis method. Design/methodology/approach An inclined thin-walled part is fabricated in gas metal arc (GMA)-based additive manufacturing using a positional deposition approach in which the torch is set to be inclined with respect to the substrate surface. A three-dimensional finite element model is established to simulate the thermal process of the inclined component based on a general Goldak double ellipsoidal heat source and a combined heat dissipation model. Verification tests are performed based on thermal cycles of locations on the substrate and the molten pool size. Findings The simulated results are in agreement with experimental tests. It is shown that the dwell time between two adjacent layers greatly influences the number of the re-melting layers. The temperature distribution on both sides of the substrate is asymmetric, and the temperature peaks and temperature gradients of points in the same distance from the first deposition layer are different. Along the deposition path, the temperature distribution of the previous layer has a significant influence on the heat dissipation condition of the next layer. Originality/value The established finite element model is helpful to simulate and understand the heat transfer process of geometrical thin-walled components in WAAM.

scholarly journals An Experimental Study to Compare the Naphthalene Sublimation With the Liquid Crystal Technique in Compressible Flow

1995 ◽  
Author(s):  
M. Häring ◽  
A. Hoffs ◽  
A. Bolcs ◽  
B. Weigand
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Crystal ◽  
Mach Number ◽  
Transfer Coefficient ◽  
Compressible Flow ◽  
Test Facility ◽  
Number Range ◽  
Naphthalene Sublimation ◽  
Sublimation Technique

The naphthalene sublimation and the liquid crystal technique are two methods being used for measurements of the heat transfer coefficient on turbine airfoils. In this paper the results obtained with the two methods for the same compressible flow conditions are compared. The measurements were performed in a free jet test facility on a flat plate and a cylinder. The free stream Mach number ranged from M=0.4 to 0.8. The naphthalene sublimation technique was applied to obtain the local Nusselt number, based on the Sherwood number, applying a new analogy function (Häring, Weigand (1995)). These results were compared with measurements on the same test arrangement using the transient liquid crystal technique. A good agreement between the two measurement techniques and correlations was found for the entire Mach number range. An application of both techniques on a turbine airfoil confirmed this observation. The sublimation technique was also applied to measure the local heat transfer coefficient on a turbine vane at exit Mach numbers up to M=0.9 and exit Reynolds numbers up to Re=1.8e6. The experimental results were compared with the two dimensional boundary layer code TEXSTAN (Crawford, 1986).

Heat transfer in lattice structures during metal additive manufacturing: numerical exploration of temperature field evolution

2020 ◽  
Vol 26 (5) ◽  
pp. 911-928 ◽  
Author(s):  
David Downing ◽  
Martin Leary ◽  
Matthew McMillan ◽  
Ahmad Alghamdi ◽  
Milan Brandt
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Additive Manufacturing ◽  
Future Research ◽  
Local Geometry ◽  
Lattice Structures ◽  
Content Type ◽  
Additional Heat ◽  
Metal Additive Manufacturing ◽  
Metal Additive

Purpose Metal additive manufacturing is an inherently thermal process, with intense localised heating and for sparse lattice structures, often rapid uneven cooling. Thermal effects influence manufactured geometry through residual stresses and may also result in non-isotropic material properties. This paper aims to increase understanding of the evolution of the temperature field during fabrication of lattice structures through numerical simulation. Design/methodology/approach This paper uses a reduced order numerical analysis based on “best-practice” compromise found in literature to explore design permutations for lattice structures and provide first-order insight into the effect of these design variables on the temperature field. Findings Instantaneous and peak temperatures are examined to discover trends at select lattice locations. Insights include the presence of vertical struts reduces overall lattice temperatures by providing additional heat transfer paths; at a given layer, the lower surface of an inclined strut experiences higher temperatures than the upper surface throughout the fabrication of the lattice; during fabrication of the lower layers of the lattice, isolated regions of material can experience significantly higher temperatures than adjacent regions. Research limitations/implications Due to the simplifying assumptions and multi-layer material additions, the findings are qualitative in nature. Future research should incorporate additional heat transfer mechanisms. Practical implications These findings point towards thermal differences within the lattice which may manifest as dimensional differences and microstructural changes in the built part. Originality/value The paper provides qualitative insights into the effect of local geometry and topology upon the evolution of temperature within lattice structures fabricated in metal additive manufacturing.

Experimental verification of computational and sensitivity analysis on substrate deformation and plastic strain induced by hollow thin-walled WAAM structure

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Keval P. Prajadhiana ◽  
Yupiter H.P. Manurung ◽  
Alexander Bauer ◽  
Mohd Shahriman Adenan ◽  
Nur Izan Syahriah ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Sensitivity Analysis ◽  
Additive Manufacturing ◽  
Plastic Strain ◽  
Equivalent Plastic Strain ◽  
Transfer Coefficients ◽  
Content Type ◽  
Heat Transfer Coefficients ◽  
Adjusted Model ◽  
Wire Arc Additive Manufacturing

Purpose This paper aims to numerical and experimental analysis on substrate deformation and plastic strain induced by wire arc additive manufacturing. Design/methodology/approach The component has the form of a hollow, rectangular thin wall consisting of 25 deposition layers of SS316L on an SS304 substrate plate. Thermo-mechanical finite element analysis was applied with Goldak’s double-ellipsoidal heat-source model and a non-linear isotropic hardening rule based on von Mises’ yield criterion. The layer deposition was modelled using simplified geometry to minimize overall pre-processing work and computational time. Findings A new material modelling of SS316L was obtained from the chemical composition of the evolved component characterized by scanning electron microscope/energy dispersive X-ray and further generated by an advanced material-modelling software JMatPro. In defining heat-transfer coefficients, transient thermometric analysis was first performed in the bead and on the substrate, which was followed by an adjustment of the heat-transfer coefficients to reflect the actual temperature distribution. Based on the adjusted model and boundary conditions, sensitivity analysis was conducted prior to the ultimate simulation of substrate deformation and equivalent plastic strain. Furthermore, this simulation was verified by conducting a series of automated wire + arc additive manufacturing tests using robotic gas Metal arc welding with distortion measured by coordinate-measurement machine and equivalent plastic strain measured by optical three-dimensional-metrology measurements (Gesellschaft für Optische Messtechnik). Originality/value It can be concluded that a proper numerical computation using the adjusted model and property-evolved material exhibits a similar trend with acceptable agreement compared to the experiment by yielding an error percentage up to 30% for deformation and up to 21% for equivalent plastic strain at each individual measurement point.

scholarly journals Skin Friction in the Laminar Boundary Layer in Compressible Flow

1949 ◽  
Vol 1 (2) ◽  
pp. 137-164 ◽  
Author(s):  
A. D. Young
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Mach Number ◽  
Flat Plate ◽  
Skin Friction ◽  
Compressible Flow ◽  
Laminar Boundary Layer ◽  
Momentum Equation ◽  
Forward Movement ◽  
Semi Empirical

SummaryFrom an analysis of the work of Crocco and others, semi-empirical formulae are derived for the skin friction on a flat plate at zero incidence with a laminar boundary layer. These formulae arefor the general case of heat transfer, andwhen there is no heat transfer.The problem of heat transfer and the effect of radiation are discussed in the light of these formula;. The second formula is then utilised in the development of an approximate method for solving the momentum equation of the boundary layer on a cylinder without heat transfer. The method indicates that with increase of Mach number there is a marked forward movement of separation from a flat plate in the presence of a constant adverse velocity gradient.

High-Speed Subsonic Compressible Lubrication

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Florence Dupuy ◽  
Benyebka Bou-Saïd ◽  
John Tichy
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Mach Number ◽  
Compressible Flow ◽  
High Speed ◽  
Transfer Number ◽  
Flow Equations ◽  
Foil Bearings ◽  
Basic Studies ◽  
Bearing Number

The present study extends the scope of compressible lubrication theory (CLT) by considering a more complete formulation of compressible flow in a thin film. A one-dimensional (1D) approximation is obtained, which is common in basic studies of compressible flow. A dimensionless formulation of the thin film compressible flow equations (continuity, momentum, energy, and perfect gas) is derived. There are three dimensionless governing parameters, the Mach number M, the compressibility or bearing number Λ, and a heat transfer number H (a sort of inverse Péclet number). The classical theory assumes isothermal conditions (a consequence of a large heat transfer number) and implicitly assumes low Mach number conditions. It turns out that neither of these conditions are met in high-speed applications such as foil bearings. Results are calculated by varying M and H in a parametric fashion. We find that the influence of Mach number is small (at least up to M = 0.5) but the influence of heat transfer is large: the classical predicted results are in error by a factor of four or so. The improved theory predicts much greater load than the traditional. This means that high-speed air bearing design based on CLT would function satisfactorily, as born out by their successful application; however, such bearings would be significantly over-designed.

Darcy-Forchheimer flow of nanofluid in a rotating frame

2018 ◽  
Vol 28 (12) ◽  
pp. 2895-2915 ◽  
Author(s):  
Tasawar Hayat ◽  
Arsalan Aziz ◽  
Taseer Muhammad ◽  
Ahmed Alsaedi
Keyword(s):  
Heat Transfer ◽  
Thermal Characteristics ◽  
Random Motion ◽  
Hybrid Nanofluid ◽  
Porous Space ◽  
Optimal Homotopy Analysis Method ◽  
Content Type ◽  
Surface Mass ◽  
Flow And Heat Transfer ◽  
Special Cases

Purpose The aim of this study is to elaborate three dimensional rotating flow of nanoliquid induced by a stretchable sheet subject to Darcy–Forchheimer porous space. Thermophoretic diffusion and random motion aspects are retained. Prescribed surface heat flux and prescribed surface mass flux conditions are implemented at stretchable surface. Convergent series solutions have been derived for velocities, temperature and concentration. Design/methodology/approach Optimal homotopy analysis method is implemented for the solution development. Findings The current solution demonstrates very good agreement with those of the previously published studies in the special cases of regular fluid and nanofluids. Graphical results are presented to investigate the influences of the titania and copper nanoparticle volume fractions and also the nodal/saddle indicative parameter on flow and heat transfer characteristics. Here, the thermal characteristics of hybrid nanofluid are found to be higher in comparison to the base fluid and fluid containing single nanoparticles, respectively. An important point to note is that the developed model can be used with great confidence to study the flow and heat transfer of hybrid nanofluids. Originality/value To the best of the authors’ knowledge, no such consideration has been given in the literature yet.

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