11 INTERNATIONAL CONFERENCE

IN MECHANICAL INDUSTRY

Volume 1

Editor: Predrag V. Dasic

15-18. September 2011 Sokobanja, Serbia

fjaTCIP

C-5. Bosnjak M.S., Petkovic D.Z., Simonovic M.A., Milovancevic D.M., Milenovic Lj.l. 450 (Belgrade - Serbia) S T R U C T U R A L A N D C O N T A C T STRENGTH OF THE REVOLVING D R Y E R

С-6. Ciortan S., Podaru G., Birsan I.G. (Galati - Romania) 456 N E U R A L N E T W O R K B A S E D A N A L Y S I S OF FRICTION C O E F F I C I E N T EVOLUTION IN STUFFING BOX SEALS

0-7. Cajetinac S., Todorovic M., Aleksandrov S. (Trstenik - Serbia), Novakovic M. 460 (Belgrade - Serbia) M O D E L L I N G AND SIMULATION O F PNEUMATIC A C T U A T O R

C-8. Damnjanovic Z.. Strbac N., Pantovic R. (Bor - Serbia), Stojkovic Z. ( Z a j e c a r - 465 Serbia) N U M E R I C A L M E T H O D S IN T E R M A L TESTING OF BUILDING M A T E R I A L S USING IR T H E R M O G R A P H Y

C-9. Damnjanovic Z.. Strbac N. ( B o r - S e r b i a ) , Velimirovic N. (Nis - Serbia). 472 Mladenovic-Ranisavljevic I. (Leskovac - Serbia) AN A L G O R I T H M S FOR IR T H E R M O G R A M S FOR D I A G N O S T I C S A O B J E C T S

C-10. Denic B.D.. Miljkovic S.G., Lukic R.J., Simic M.M. (Nis - Serbia) 481 SERIAL C O D E READING C O R R E C T N E S S DETECTION APPLIED T O P S E U D O R A N D O M A B S O L U T E E N C O D E R S

С-11. Eric M.D. ( C a c a k - Serbia), Mandic V. (Kragujevac- Serbia), Markovic S. ( C a c a k - 489 Serbia) I N T E G R A T E D SYSTEMS IN THE D E V E L O P M E N T OF C O N C E P T O F C O N C U R R E N T ENGINEERING

0-12. Eric-Obucina J., Todorovic M., Cajetinac S., Jevremovie V. (Trstenik - Serbia) 494 KINEMATIC A N A L Y S I S A N D A N I M A T I O N OF MOTION OF THE M E C H A N I S M CONSISTING OF ROD AND SLIDER

C-13. Gorbach E.V., Sereda V.G., Palamarchuk V.A. ( k r a m a t o r s k - Ukraine) 499 R E S E A R C H A N D PERFECTION O F T E C H N O L O G IC A L PROCESS OF T A N G E N T I A L ROLLING OF PIPES BY FRICTION TOOL

0-14. Gospodinov D.. Hadjiiski V., Stefanov S. (Plovdiv - Bulgaria) 507 USING OF THE FINITE E L E M E N T M E T H O D FOR STUDYING ТІ IE EFFECT OF THE BASIC G E O M E T R I C P A R A M E T E R S OF THE C O R R U G A T E D P A P E R B O A R D OVER ITS C O M P L E X M E C H A N I C A L PROPERTIES

0-15. HladnikJ . , Resman F., Jerman B. (Ljubljana - Slovenia) 513 FINITE E L E M E N T A N A L Y S I S OF C R O S S - C O U N T R Y SKIING B O O T TORSION STIFFNESS

0-16. Kazimierska-Grebosz M. (Lodz - Poland) 520 THE RESEARCH OF ACOUSTIC S C R E E N S IN ANECHOIC R O O M A N D IN REAL C O N D I T I O N S

0-17. Kegl M., Harl B. (Maribor - Slovenia) 526 T O P O L O G Y OPTIMIZATION USING DESIGN E L E M E N T S A N D A LEVEL SET FUNCTION

0-18. Litovchenko I., Shpak M. (Kviv - Ukraine), Stefanov S., Hadjiiski W. (Plovdiv - 533 Bulgaria) MIXER'S DESIGN M E T H O D WITH C O M P U T E R MODELING

0-19. M i k h o v M . R . (Sofia - B u l g a r i a ) 539 PERFORMANCE ANALYSIS OF A BRUSHLESS DC M O T O R DRIVE FOR MECHANICAL INDUSTRY

O-20. Milicevic I., Boskovic N., Slavkovic R., Golubovic D., Ducic N. (Cacak - Serbia) 545 DESIGN A N D SIMULATION OF A U T O M A T I O N C O N T R O L S Y S T E M FOR M E C H A T R O N I C SYSTEM P R O T O T Y P E FOR PRODUCTION O F W I R E D PROFILES WEDGE SHAPED

0-21. Morovic L., Peterka J., Kovac M. (Trnava - Slovakia) 550 DIGITIZATION OF BALL NOSE END MILLS BY OPTICAL 3D S C A N N E R

XI I I

Sokobanja і

і Serbia •

11th International Conference "Research and Development in Mechanical Industry"

RaDMI 2011 15 - 18. September 2011, Sokobanja, Serbia

MIXER S DESIGN METHOD WITH COMPUTER MODELING

Igor Litovchenko1, Maxim Shpak1, Stefan Stefanov2, Wilhelm Hadjiiski2

! National University of Food Technology, Kyiv, U K R A I N E * University of Food Technologies, Plovdiv. BULGARIA, E-mail: s tvstcfanpv'a vahoo.com

Summary: The paper demonstrated the possibility of applying c omputer modeling to analyze and optimize the design parameters and operating modes of the equipment for kneading in the food industry. Based on the earlier model was made to simulate the process of kneading dough. Studied are the effects of various factors affecting the process. Are certain functional dependence of the power used by the number of w orking bodies, their size, speed, etc.. The proposed methodology allows determining the optimal performance of equipment.

Keywords: computer modeling, kneading, dough, mixing process.

I. I N T R O D U C T I O N

At research of the existing technological equipment of the food-processing industry in the operation [1], and also during design of new items there is a number of processes which are difficult to be described by existing methods from mathematical apparatus. It is possible to include mixing to such processes for which it is difficult to present and describe behavior of a viscous fluid in mixing dish and thus to obtain such data, as velocity distribution on all points of the volume, intensity of a dissipation of a kinetic energy, power indexes of specific work and power. For example, at presence, due to large variety of constructions of dough organs, the designer is not able reasonably to present the shape of working organ, which would be an optimum for a specific dough type (grain, confectionery, wheaten, rye and other). Very often the choice is made intuitional, and the next step is performing of experimental researches, which require many resources, efforts and time. It is proposed to use an integrated approach to take into account the interrelated key factors that effect on the quality of the end result during the work with a new design of mixing equipment. Here they are: - Searching ol the working bodies" optimal shape and the kneading capacity; - Kinematic parameters of the mixture motion analysis and their effects on the rheological properties of the product; - The nonlinearity changes the properties of the dough as non-Newtonian fluids during mechanical treatment; - Determine the effect iveness of mixing of the components - to achieve adequate uniformity of distribution of components in the volume of the mixture; - Determine the optimal intensity of mechanical impact on the various process steps. The main practical ways of the project realization is a statement of physical experiments and computer simulation. Base on that we are able to predict and visualize process of mixing of a product on all its extent, receiving all necessary hydrodynamic and power indexes. The software package for personal computers «Flow Vision» has been used for the process research of the dough kneading. T h e p rogram

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is developed for simulation of hydrodynamic processes and also visualization of these processes by methods of a computer drawing. When different turbulent models arc used it is possible complex movements of the fluid to be simulated, such as currents with a strong twisting and a free surface. We illustrate an integrated approach for design of illustrative examples of computer simulation.

2. EXPOSE

2.1. Searching of the optimum shape of workings organs and kneading capacity

The task of this method is to find the optimum shape of the kneading organs which ensure high product quality at small power expenditures. Modeling process of the dough flow around working organs with different cross sectional profile, it is possible to determine in which case the product turbulence is the highest and what is the energy consumption in this case. Fig. 1 shows as a isolines these areas where the speed of product deformation during movement of working organ in dough mass.

1 2

1 2

b

с Figure 1: Figure caption. Speeds isolines (2) in a cross-section of the dough organs (1) w ith

different shapes: a - rectangular; b - cylindrical; с - triangular

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Analyzing the achieved graphic results, we are able to define geometrical parameters of the working areas, where a high-speed mixing is, and also the preferred shape of a working element. This choice is already in connection to a preset speed of its movement and rheological parameters of the prepared mixture (viscosity, density, temperature). 2.2. Research of the mix tu re movement k inemat ic p a r a m e t e r s and their inf luence over the p roduc t rheological p roper t ies Most of the food products are non-Newtonian fluids and their viscosity depends on the deformation rate gradient (Fig. 2). Researching of the influence of kinematic parameters on the rheological properties of the viscous mass is also possible to recreate with the help of computer simulation.

u. Pa s * 160-

110

60

0 600 1200 1800 • C - 1 У і b

Figure 2: Dependence of bread dough viscosity from the deformation speed

The chart shows that the dependence between the dough viscosity and the speed of deformation is nonlinear. During researches was determined functional connection between these parameters, which looks like the following:

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If considered this dependence when modeling mixing process it is possible to obtain the graphic and numerical data about changes of product viscosity in different points of the mixing capacities (Fig. 3). The areas with the lowest indexes of viscosity in this case also arc the areas of the most effective mixing. On a Fig. 3 is shown the area of the dough viscosity distribution in a mixing dish with a value 100 P a s .

Figure 3: The viscosity areas of 100 Pa-s at the motion of working bodies of rectangular (a) and spiral (b) form.

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2.3. Reading of the nonlinearity dough properties change as a non-Newtonian fluid during mechanical treatment

In modern dough mixers mechanical impact over the dough could occur in a wide range of product deformations velocity. It inevitably influences a dough rheological property, sometimes on 1... 2 orders changing them. During the analysis of dependence between shear stress of the grain dough and deformation velocity, it has been determined that for the description of behavior of viscous thixotropy equation Hershel -Baklcy is appropriate, where the flow index n is included, essentially influencing a mixing process:

(2) Г = г 0 + k - y n

For determination of a flow index n. the technique proposed by Mettsner-Ridom was used. It is based on usage of a Mooney-Rabinovich ratio for definition of tension that creates friction forces on a wall. Further step is definition of a flow index, which is done using the following formula:

d In Г 11

d ІП 7 (3) In a graphic aspect dependence is presented on Fig. 4.

ил

0 4 rO

Figure 4: Dependence of a flow index from deformation velocity

The given dependence numerically is described by the formula:

0.539 и = • 0.13!

7 < 4 ) . During modeling of dough mixing process, the achieved dependence allows studying the change of flow index inside the dish (Fig. 5). It is possible to achieve integral characteristic of the variable. which is average on a dish section. As a result of simulation it has been determined, that in calculation of power of mixing process, for low-speed dough mixers it has to be usedan index n = 0,6, and for high-speed mixers - n = 0.53.

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The described method of the precise reading of specific behavior of the dough during the deformat ion of its working organs al lows increasing the accuracy of the mixing process description.

Kigure 5: Isolines of the f low index change in a dough dish. 1 - a working body, 2- isolines

2.4. Determination of the component distribution equability in the volume during mixing

Possibility to present behavior of the two-phase mixtures, consisting components with different rheological indexes is an additional advantage of computer simulation. As an example, process of primary mixing together of components of the baking dough (a f lour and water) on different t ime intervals (Fig. 6) f rom the process beginning is displayed.

Figure 6: the distribution of mixture density in a dough dish: a - 16 sec after process beginning; b -21 sec after process beginning

From the analysis of images is visible how quantity and surface of area (1) gradually decreases, where uniformity of components in the mixture are still significantly different. It gives a chance to def ine sufficient duration of mixing process f rom a point of view of reaching the suff icient homogenei ty of the product.

2.5. Determination of opt imum intensity of mechanical impact on the different stages of the mixing process

During complex research of mixing process, simultaneously with rheological and hydrodynamic parametcrs def ining there is a possibility of definition of power indexes of the process. It a l lows calculation of the necessary drive power. One of the advantages of this method is the velocity of a dissipation of a kinetic energy determinat ion (Fig. 7) which significantly impacts the energy consumed by a drive and, hence, on its power .

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If dependence between viscosity and construction parameters arc preset, it is possible to calculate energy loses for different condit ions f rom dough mixing process. It was defined functional dependence between power consumption and number of working organs, their sizes, velocities of their movements , dynamic viscosity of the mixture, width of a boundary layer (a clearance between a wall of the dish and working organs). The proposed method allows to calculate drive power of a dough mixer precisely.

3. C O N C L U S I O N

Using computer simulation helps us to reduce the t ime and resources which are needed to study the processes occurring during the mixing of viscous liquids. An integrated approach to model ing makes it possible to determine the optimal form of mixers and power required for mixing, considering rheology changes.

R E F E R E N C E S

[1] Litovchenko I.. I. Mihaylov. S. Stefanov. Modeling of some processes of filling of mince with one type of spiral feeding mechanism. In: Proceedings of l()'h International Conference "Research and Development in Mechanical Industv - RaDMI 2010", Donii Milanovac. Serbia. 16 - 19. September 2010. Edited by Predrag DaSic. Trstenik: High Technical Mechanical School, 2010. pp. 34-45. ISBN-13 978-86-83803-20-0.

[2] Litovchenko I., M. Shpak, St. Stefanov. V. Hadzhijski. Modeling of technology processes in the creation of equipment for food industry. Proceedings of International conference of University of Ruse "Angel Kanchev" volume 49. book 9.2, pp. 50-55.

[3] Litovchenko I.. M. Shpak. St. Stefanov. Oprcdelenie potrebliaemoi mostnosti pri zamese testa na osnove ucheta sil soprotivlenii. Innovacionnie technologii v proizvodstve I prerabotke selskohoziaistvennoi produkcii: dokladi megdunarodnoi nauchno-prakticheskoi konferencii: Minsk, 14-15 april 201 l./pod obsht. Red. V.B.Lovkisa. A.A. Brencha. B.M. Pozdniakova.-V 2 ch. Ch. 2=Minsk: BGATU, 2011.-288 s. ISBN 978-985-519-363-1. Str. 64-67.

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