This paper uses a thermal simulation model that can be applied to electromagnetic field and for the sound. Due to the symmetrical structure difuzorlui using AXI-symmetric pattern which significantly reduces computing time

Constantin D.Stanescu

Liliana Cainiceanu

Tudor Burlan

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  Fiabilitate si Durabilitate - Fiability & Durability    Supplement no 1/ 2012   Editura “Academica Brâncuşi” , Târgu Jiu, ISSN 1844 – 640X     94 EXPERIMENTAL  THERMAL  SIMULATION OF  THE HIGH AUDIO SPEAKER  Prof. ing.drd.Liliana  Cainiceanu –Universitatea   “Politehnica” Bucuresti e_mail : lili_cainiceanu@yahoo.com Prof.Univ.ing. Dr.Constantin D.Stanescu- Universitatea   “Politehnica” Bucuresti e_mail : prof_cstanescu@yahoo.com  Prof.drd.Tudor Burlan- Universitatea “Politehnica”   Bucureşti e-mail:burlan.tudor@ yahoo.com  ABSTRACT:This paper uses a thermal simulation model that can be applied to electromagnetic field and for the sound. Due to the symmetrical structure difuzorlui using AXI-symmetric pattern which significantly reduces computing time.   Key words :magnets, air gap, coil  1.INTRODUCTION  To reduce the number of elements we consider membrane for thermal analysis, a little thicker than the real one. Construction details of the frame (chassis) will also be simplified, preferably using straight line model. Model with main geometrical parameters is shown in Figure 1, and values are given in Tab.1   Fig1.The speaker used in the simulation represented with the main parameters (ambient air is presented in full)        Fiabilitate si Durabilitate - Fiability & Durability    Supplement no 1/ 2012   Editura “Academica Brâncuşi” , Târgu Jiu, ISSN 1844 – 640X     95                                                                 Table 1. Geometric parameters of the model speaker Parameters (mm) RC  HC  RPI  RPE  HM  HP  RF P100  40  20  9  27,5  10  16  50 P200  85  30  17  43,5  15  27  100 P300  125  50  25  60  20  32  150   In the mesh, special attention was paid to interior cavity where there is most important, namely the heat transfer coil. In the air gap were used rectangular elements. The discretized (with mesh) is shown in Figure 2 (a)   Fig.2 (a) The discretized., (B) 3D model made by extension symmetry due   2.MATERIALS  Material parameters used in the analysis are presented in Tab.2  Tab.2. Material properties used in analysis Mat.nr.  Materials  Thermal conductivity (W/ m ∙K) Density (Kg / m3 ) Specific heat (J/ Kg∙ K) 1  Ferrite (magnet)  3,2  4400  750 2  Soft steel (pole piece)  48  7840  450 3  Paper (membrane)  0,18  900  1340 4  Copper (coil)  380  8920  385 5  Aluminum (support coil)  180  2600  1256      Fiabilitate si Durabilitate - Fiability & Durability    Supplement no 1/ 2012   Editura “Academica Brâncuşi” , Târgu Jiu, ISSN 1844 – 640X     96 ANSYS has been used in the simulation, request that the material always be No.1 air (or fluid) and taking into account mecanisumul natural convection (buoyancy) physical properties of air to be highlighted in particular are temperature and density. Area that extends to the air must be large enough not to influence the flow of heat in the area of interest, but bear in mind the overall size of the model. Analysis performed using conjugate heat transfer process. Both areas of fluid and solids are modeled together using the same type of finite element. CFD analysis (Computational Fluid Dynamics) performs calculations necessary to satisfy the law of conservation of momentum and mass. This analysis is (fluid flow) suitable for problems involving convection cooling. The disadvantage of this method is that for materials with thermal conductivities is different the  precision is not good. Analysis was performed with a transient simulation for high enough temperature to obtain the stationary solution.  Analysis of steady state model is applied using the   initially solutiones. Coil was modeled with constant power density proportional electric power applied to the speaker.  3. RESULTS  OF  MEASUREMENTS  AND  SIMULATION  Simulations and measurements were made assuming that we have two types of speakers that we call "small", P100 and that "high", P200 frames with outer diameters of 100 mm and 200 mm respectively. Figure 3 shows the speaker P100.   Fig.3 .P100 speaker with diameter 100 mm (a) front view (b) rear view  Speakers analyzed power ratings of 20 and 100 W. The measurements were made using about 100 Hz sinusoidal signal. For temperature measurements were used based on contact measurements based on an acquisition system with thermocouple on one side and additional measurement system based on IR (infrared). We used a total of five thermocouples placed in different positions, including positions "hidden" for IR measurements. Speaker P100 was prepared in two versions with a coil made in support of a classic paper and support alumniu.Masuratorile and simulations were conducted at a power level of 16W for small speaker, 50 W respectively the largest. Measurement results are presented based thermocouples in tabele3, 4 and 5     Fiabilitate si Durabilitate - Fiability & Durability    Supplement no 1/ 2012   Editura “Academica Brâncuşi” , Târgu Jiu, ISSN 1844 – 640X     97                               Table 3. Measurement  results on loudspeaker of 10 cm coil support the paper.    Temp.termocuple(°C)   Frequency (Hz) Power (W) Tmax(IR) (°C) 1  2  3  4  5  Area graph from fig.6. 100  8       39  34,3  32,5  30,2  27,5  23,9  A 1000  8  63,8  52,8  50,3  47,1  43,7  34,2  B 100  16       74     54  50,9  45,7  35,6  25,6  C 1000  16  86,1  70,4  66,5  61,1  55,8  40,2  D 100  20  88,6  68,8  65,1  58,7  41,7  26,9  E 1000  20  92,5  75,8  71,4  65,4  59.4  41,4  F                                Table.4. Measurement results on loudspeaker of 10 cm aluminum coil support.    Tmax Infrared (°C)  Temp.termocuple(°C) Frequency (Hz) Power (W) Front  Profile  Back  1  2  3  4  5 100  8  38,8  29,6  39,5  30,7  30  27  26,8  24,2 1000  8  79,8  43,1  42,8  47  44,9  39,6  40,3  32,2 100  16  58,3  39,8  43,0  43,7  42,2  34,4  33  26,3 1000  16  109  53,5  57,6  63,6  60,1  51,9  52,2  38,6  For data interpretation is necessary to specify the position thermocouples attached speaker. For Tables 3 and 4 position thermocouples was 1-5 in Figure 5:  Figure 5 Position thermocouples the measurements contained in Table 3 and 4, Bolt central flange 2 inf. Magnet 3, 4 cavity lateral to the coil, 5 Chassis  Speaker P 200 with a diameter of 20 cm have been used only four thermocouples, thermocouples denoted by 1,2,3 and 4 in Table 5 are the positions in Figure 5, respectively as follows: 4 cavity, 2 flange. 3, magnet, 5 chassis.      Fiabilitate si Durabilitate - Fiability & Durability    Supplement no 1/ 2012   Editura “Academica Brâncuşi” , Târgu Jiu, ISSN 1844 – 640X     98             Tab.5 Results of  measurements for speaker on 20 cm with aluminum coil support    Tmax Infrared (°C)  Temp.termocuple(°C) Frequency (Hz) Power (W) Front  Profile  Back  1  2  3  4 100  20  63,7  44,5  39,3  35,1  37,7  32,6  25,5 1000  20  54,3  37,6  40,6  37,5  39,6  36,2  28,0 100  50  76  43,2  47,9  43,2  47,3  41  30,1 1000  50  101  56,1  60,3  52,1  60,8  47,8  28   Mains based on data acquisition can be represented graphically and time evolution of temperature in the 5 samples that were placed in temperature. For configuration presents search The results for configuration presents in Table 3 is shown in Figure 6    Fig.6.Evolution of temperature measurement  in the 5 point of measurement  corresponding  from Table 3.  The data in Figure 6 have estimated thermal time constant of the speaker, a value that was useful for transient simulations the choice of the final simulation time.   CONCLUSIONES Was performed thermal modeling and simulation of a permanent dynamic speaker on finite element analysis that uses fluid flow (CFD analysis) . Simulation results were accompanied by complex measurements.  For the purposes at this stage of research the results of measurements corespond with the simulation results.      Fiabilitate si Durabilitate - Fiability & Durability    Supplement no 1/ 2012   Editura “Academica Brâncuşi” , Târgu Jiu, ISSN 1844 – 640X     99 REFERENCES [1]  Otto J. , “Dynamic Simulation of  Electromechanical  System using  ANSYS and       CASPOC” ANSYS Conference ,22-24 April 2006 ,Pittsburg, USA.  [2]   Rohsenow  W.M., Hernett J.P. ,Young I., “Handbook of transfer” -3th edition , McGraw-Hill ,1998  [3]  Dodd M. , “The Application of  FEM to the analysis of  Loudspeaker  Motor Thermal behavior” ,The 112th Convention of Audio Engineering Society ,2002 May 10-13, Munich,Germany. 

EXPERIMENTAL THERMAL SIMULATION OF THE HIGH AUDIO SPEAKER

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