CC BY
94
DOI: http://dx.doi.org/10.20534/AJT-17-1.2-51-54
Maslov Ivan Vasilevich, Don State Technical University, master's degree student of the Department of Welding Engineering, Rostov-on-Don, Russia E-mail: deagls666@mail.ru
Numerical simulation of underwater curtain welding with various configurations of water nozzle
Abstract: The article tells about the unsteady numerical simulation of hydrodynamic characteristics of underwater welding with water curtain nozzle. The simulation is based of CAD-models with various configurations of water nozzle exit. The simulations are performed with the help of the software package computational fluid dynamics ANSYS CFX.
Keywords: water curtain welding, local cavity, underwater welding, computational fluid dynamics, finite element method (FEM).
Technology of underwater mechanized solid wire welding with a water curtain nozzle is known from the beginning of the 1970s [1; 2]. This welding method is implemented by means ofburner with two concentrically arranged nozzles (fig. 1), a shielding gas is fed into the welding zone from the inner nozzle, and water at the angle to the workpiece surface is fed from the outer nozzle. A highspeed water flow forms the water curtain at the exit from the nozzle, which provides shielding of the welding zone from exposure to the aqueous environment. The initial laboratory tests of the welding process have been carried out in Japan (Government Industrial Research Institute, Shikoku), later in Germany (Laboratorium für Werkstoffkunde und Schweißtechnik, Hamburg), South Korea and other countries [3]. This technology of local protection of the welding zone allows realizing the underwater electric arc and laser beam welding [1; 4].
The numerical study [5] of the hydrodynamic characteristics of a water curtain at various configurations of the water nozzle exit has been performed. The simulation has been performed without the shielding gas in a stationary setting with a closed local protection zone area. It was found that at configurations A and B (fig. 2) of water nozzle exit, the water curtain has similar hydro-dynamic characteristics that justify the practicability of simulation to the shielding gas in the unsteady setting. The purpose of this work is the numerical simulation of underwater welding process with a water curtain nozzle, in order to determine the optimal configuration of the water nozzle exit.
Fig. 1. Diagram of local dry cavity formed by water curtain
Fig. 2. Structure and size of water curtain nozzle
Obtaining of accurate hydrodynamic characteristics of this process is complicated by the inhomogeneity of the environment, between which the streams of water curtain flow, the pressure difference in the local protection zone and the aquatic environment, as well as the
impact of the shielding gas flow on the curtain. In order to track the impact of the water nozzle exit location on the process the high resolution capability visualization is required, which can be implemented in CFD-packages. The simulations are performed with the help of the software package computational fluid dynamics ANSYS CFX. The geometrical parameters of the burners, used to generate the CAD-models of the computational domain, are shown in fig. 2.
Settlement areas are part of the pie geometry angle 6°. The numerical integration of differential Navier-Stokes equations is carried out by finite volume method.
Calculated fields are split (discretized) into non-crossing volumes so that each junction point is contained in a finite volume. The differential equation is integrated under each finite volume, at that, the piecewise constant functions are used, describing the behavior of the dependent variable between junctions. At the result we have a discrete analogue of the solved equation. The grid models are presented by tetrahedral elements and have thickenings in the area of the boundary layer on the surface of the welded workpiece, as well as in the channels and exits of the nozzles (fig. 3). The total number of nodes in the computational grids >320 000, elements >1 770 000.
Fig. 3. Computational grid
In this case, the water curtain is a free submerged jet of viscous fluid directed to the planar obstacle at an angle of 45°. By interacting with the obstacle, the free jet forms the wall-adjacent jet which spreads radially from the burner axis. In this regard, in order to get the quality results, both in the flow core and the wall-adjacent, the turbulence model is necessary that describes well both free and near-wall flows. Until recently, the most popular among differential turbulence models were the two-parameter turbulence models, based on the examination of the kinetic energy of turbulent fluctuations k. Either equation of energy dissipation rate e transfer, or specific energy dissipation rate w [6] are used as the second equation. The drawback of k-e-model is a low accuracy in simulation of flows with separation from smooth surfaces, but Wilcox k-w models do not have such drawback. Based on the fact that the turbulence model of k-e type with a high degree of reliability describes the shear flow at a distance from the wall, and models of k-w type have the advantage in the simulation of near-wall flows, Men-ter in 1993 proposed the SST (Shear Stress Transport) model [7], combining the best features of these models.
After the CAD-models of calculation area have been coated with the grid control volumes the calculation model was established by imposing initial and boundary conditions, parameters of the simulated processes and tasks of the solver settings. First of all, this is the set of equations that needs to be solved:
Navier-Stokes equation:
d ( — \ d
Fit
(U )+ -(uu )=-
dt
+-
dx.
M
eff
dx
dU. dU. — +—
dx. dx.
dx{
2 dUtS:
Meff— &
3
dx.
Continuity equation:
dp d — +-
dt dx..
K ) =
Energy equation:
d / d ( tti\ ÔP TT ÔP
- t ... ■
dU. dQj
dx..
dt dx. dt 1 dx. 1 dx.
1 1 1 1
Equation of state:
P = pRT.
The SST-model of turbulence was used as the final equation:
pk d , . dv *
-p pa>k +
dpk +^(pv.k ) dx yH ! }
dt
dx.
+
d_ dx..
dk_ dx..
dp(D d
+
dt dx.
—(pvtrn) = —
Y dv{
v
dx.
+
+
dx,
da
( Vr )— 1 + 2p(! - F1K
1 dk da a dx, dx..
a
d
The computation has been carried out for the follow- surrounding aqueous environment and the water en-ing parameters: depth — 0.5 m, volumetric feeding of tering into the local protection area is periodic. The
C02-60 l/min, water — 60 l/min. In the initial moment of time all the volume of the computed region was filled with water. Arrangement and main values of the boundary conditions are presented in the Table 1.
This mode of water and shielding gas feeding does not ensure the stable weld zone protection from the
water is displaced from the area inside the water curtain at the initial moment of time, and then the water curtain begins to deviate from the axis of the water nozzle and the water penetrates into local protection area. The results of C02 volume fraction simulation are presented in the fig. 4.
Table 1. - Used boundary conditions for the equation system
REGION (Fig. 3) TYPE SETTINGS
AB INLET (CO2) mass flow rate 0.032946 g/s
EF INLET (water) mass flow rate 16.667 g/s
H-J OPENING relative pressure 0.0 Pa
B-E, F-H, JK WALL wall roughness smooth wall
remaining surfaces SYMMETRY
DEFAULT DOMAIN
C02 at STP, water material library
reference pressure 1.05 atm
buoyancy reference density 1000 kg/m3
gravity Y component -9.81 m/s 2
ANALYSIS TYPE/SOLVER CONTROL
analysis type transient
total time 0.6 s
timesteps 0.001 s
min./max. coefficient loop iteration 3
Fig. 4. CO2 volume fraction. Left configuration A, the right configuration B
Fig. 5. The pressure at points A and B on time
The water jet focusing is directly dependent on the shape of the water nozzle exit. Improvement of focus increases the rigidity of the jet, which in turn improves the stability of the process. The rigid jet is also capable of holding increased pressure in the local protection area. The pressure charts for the points A and B were constructed for analysis of the pressure change in local protection area on time (see fig. 5).
It may be noted that the chart for the point A has long intervals with the stable pressure and sudden changes have the periodic nature. The average pressure for the point A at a given interval of time has the more value — 1321.056 Pa, against 1234.910 Pa. for the
point B, indicating the greater rigidity of the jet in the first case. This, in turn, is explained by the fact, that at the configuration A at the angle 45° the water nozzle exit in longitudinal section is axisymmetric.
From the overall image of the results, we can conclude that the configuration A of the water nozzle outlet contributes to a more sustainable water jet, which in turn improves the stability of the process. In this case the ability of a water curtain to hold the greater pressure in the local protection area also shows that in this configuration the less water consumption is required to maintain the non-aqueous environment in the welding zone.
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References:
Hamasaki M. and Sakakibara J. Studies on the Underwater CO2 Arc Welding Method with a Curtain Nozzle//J. Japan Weld. Society. - 1973. - Vol. 42, No. 9. - P. 897 (in Japanese).
Mitsubishi Jukogyo. Welding Torch for Underwater Welding [P]. USA:4029930. 1977-06-14. Maslov I. V., Rogozin D. V. The numerical investigation of shielding gas flow at the underwater welding with water curtain of a nozzle. UNIVERSUM: Technical Sciences. - 2017. - 1 (34)//[Electronic resource]. - Available from: http://7universum.com/ru/tech/archive/item/4197 (in Russian).
Zhang X. D., Ashida E., Shono S., Matsuda F. Effect of shielding conditions oflocal dry cavity on weld quality in underwater Nd: YAG laser welding// J. Mater. Process. Technol. - 2006. -No. 174. - P. 34-41. Rogozin D. V., Maslov I. V., Koronchik D. A. Numerical calculation ofhydrodynamic parameters for underwater welding with water curtain nozzles//Young Researcher of the Don. - 2017. - № 1 (4)//[Electronic resource]. -Available from: http://mid-journal.ru/upload/iblock/5b2/94_100.pdf (in Russian).
Hitryh D. P. Turbomachinery Design: review of turbulence models//ANSYS Advantage. Russian edition. -2005. - № 1 (1). - P. 9-11 (in Russian).
Menter F. R. Zonal two equation k-w turbulence models for aerodynamic flows. In: 24th Fluid Dynamics Conference, Florida, USA, 6-9 July 1993. - Paper No. AIAA 93-2906.
Economic calculation of efficiency of introduction of the gauge of deterioration and temperature in the car engine
DOI: http://dx.doi.org/10.20534/AJT-17-1.2-55-58
Salahov Timur Zufarovitch, Ufa state aviation technical university, postgraduate student, the Faculty of aviation technologic system E-mail: Tim-DoctorD@yandex.ru Migranov Mars Sharifullovitch, Ufa state aviation technical university, professor, the Faculty of aviation technologic system Nigmatullin Rashit Gajazovich, Manager of Company "Himmotolog", Ufa state aviation technical university, professor, the Faculty of aviation technologic system Hamidullin Ruslan Galeevitch, director of Company "GasAutoCentre-Ufa"
Economic calculation of efficiency of introduction of the gauge of deterioration and temperature in the car engine
Abstract: The deterioration and temperature gauge allows:
- to reveal lacks at an early stage;
- to supervise temperature in oil-filled units;
- to supervise deterioration under the maintenance of particles of deterioration in oil-filled units;
- to fix a current condition of knots of a friction;
- to store in memory of the computing block the information in the form of tables and schedules of concentration of particles of deterioration depending on time;
- to predict and give out recommendations about terms of replacement of greasing and to carrying out of repair work;
- to save the finance.
Keywords: economic calculation, deterioration, a friction, the analysis of oil, an expenditure of labour, engine repair.
Introduction The gauge of products of deterioration has already
The analysis of a technical condition of the equip- proved the efficiency: during tests the raised maintenance ment is based on equipment diagnostics under the anal- of particles of iron in a distributing box that has proved ysis of lubricant working in it [1]. In article economic to be true results of the analysis трансмиссионного oils calculation of cost of introduction of the gauge of de- on spectrometer OSA MetalLab has been revealed. The terioration and temperature in the engine of the car the device is patented, has successfully passed bench tests, Gazelle and its comparison with existing service in the and also operational tests for car «Gazelle». conditions of real use is resulted. Research technique
Question condition For economic benefit calculation used the formula:
Data from the device on wireless communication ЕЕ = Е- Е- C, (1)
у у nc f 4 '
BlueTooth are transferred to phone or a tablet where where: Ey — annual economy, or results which are
the owner can see data on a current condition of knots reached as a result of concrete activity; of a friction, schedules of concentration of particles of Enc — standard effectiveness ratio; a constant which
deterioration depending on time, the forecast and rec- depends on a concrete field of activity (0.15); ommendations about terms of replacement of greasing C — expenses for concrete activity for which eco-
and to carrying out of repair work. nomic benefit is counted up.
