Mitglied der Helmholtz-Gemeinschaft Thermo-mechanical analysis of a concept of mirror assembly R. Voinchet, O. Neubauer, Y. Krasikov, L. Krasikova, A. Panin 18. Oktober 2011 R. Voinchet
Abstract Our project is aimed to develop core CXRS diagnostic for a nuclear reactor (ITER). This diagnostic is composed of a interferometer getting a light from the interaction between a neutral beam and the plasma to analyze. This light is reflected via a set of seven mirrors. The first mirror ( M1) is the most stressed from electro-magnetic, thermal and particle loads. Moreover, the surface and position of the mirrors have to be stable. The thermo-mechanical analysis shown in this presentation aims to test the acceptability of a M1 concept assembly from a stability point of view. 18. Oktober 2011 Folie 2
Core CXRS Hinges Adjusting tie rod Holder Mesh M1 Overholder Subholder 18. Oktober 2011 Folie 3
Plan Introduction; General assumptions; First estimation: analysis of the mirror temperature and deformation with variation of the fluid parameters and cooling channel; Second estimation: analysis of the mirror tilting during operation (α) as function of the contacts and cooling temperature of the support; Third estimation: α and thermal analysis as function of the interfaces at hinges; Fourth estimation: analysis of the chosen model; Conclusion. 18. Oktober 2011 Folie 4
Introduction The thermo-mechanical analysis of the M1 assembly has been performed to: compare cooling channel options, analyze the thermal effect of the holder material, coolant pressure and velocity, analyze the M1 tilting during operation (α) as function of: the contact conductance between components, the cooling temperature of the support, the interfaces hinges/holder, determine the fluid parameters for the M1 thermal conditioning, calculate the consecutive M1 local curvature radius, distortion and tilting (α and RT*/operation). Conditioning phase (heating by fluid) Operation phase (cooling by fluid) α *RT: room temperature 18. Oktober 2011 Folie 5
HTC (W/m².K) General assumptions: correlations for the fluid calculations: HTC vs fluid velocity (Helium) HTC vs fluid velocity (Pfluid = 30bar) 2000 1900 1800 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0 Nusselt Gnielinski Petuklov, Kirillov and Popov 8 16 24 32 40 Mean fluid velocity (m/s) Nusselt correlation taken into account 18. Oktober 2011 Folie 6
General assumptions: conductance vs contact pressure for a papyex mesh Conductance at contact of papyex with CuCrZr [1]: As the difference of rigidity between papyex and CuCrZr is large compared to those between SS and CuCrZr, the graph on side, as first estimation, is used assuming SS instead of CuCrZr. 17 M8 screws of SS 316 LN admissible preload P: 80%*F (F S mb *A n [5]) = 34000N (17*2000N) Mesh area: 0.0306m² Contact pressure mesh/holder-mirror: 1.1MPa On the simplified model (ANSYS): 1.1*0.0306/0.031677 = 1.07MPa 10000W/m².K 18. Oktober 2011 Folie 7
General assumptions: thermal modeling details Support temperature applied on surface Thermal elements: SOLID87/90 Neutron loads applied on volumes Fluid elements: FLUID116 18. Oktober 2011 Folie 8
General assumptions: structural modeling details Support: fixed Z Structural elements: SOLID186/187 Y Cylindrical support X α obtained by creation of 2 volumes from deformed nodes: 1 at conditioning 1 at operation α = angle between the 2 volumes Cylindrical contacts at hinges: no-separation type/pure penalty formulation (pivot links); All other contacts: bounded type/pure penalty formulation. 18. Oktober 2011 Folie 9
First estimation: analysis of the mirror temperature and deformation with variation of the fluid parameters and cooling channel Model: Neutron loads: 0.3W/cm 3 for M1, 0.24W/cm 3 for the other parts Holder material: full SS and SS/CuCrZr; All hinges considered of SS; Fluid: Helium; Fluid pressure: 30 and 40bar, inlet temperature: 250 C; Fluid velocity: 8, 16 and 24m/s (503, 867 and 1192W/m².K, respectively); Temperature of the support: 100 C; Cooling channel (reference (Ref_CC) and alternative (Alternative_CC)): Ref_CC Alternative_CC 18. Oktober 2011 Folie 10
First estimation: results of the thermal analysis There is no important contribution from a subholder (mirror side) of CuCrZr on the M1 cooling; M1 temperature is not changed with alternative CC; A helium pressure of 30bar is sufficient in combination with high velocity: 24m/s (the higher the velocity is, the closer the cooling performance is from the 40bar s one). 18. Oktober 2011 Folie 11
First estimation: cooling channel comparison - local curvature radius Average distance between 2 node samples: 5mm Advantage for the reference cooling channel option: local curvature radius generally higher 18. Oktober 2011 Folie 12
First estimation: cooling channel comparison - distortion Distortion comparable for both cooling channels 18. Oktober 2011 Folie 13
Second estimation: analysis of the M1 tilting during operation (α) as function of the contacts and cooling temperature of the support Model: Neutron loads: 0.3W/cm 3 for M1, 0.24W/cm 3 for the other parts Conductance*: low, 500W/m².K, and real, calculated from the contact pressure at links [7] considering: cylindrical contact surfaces: Ra = 0.8µm, flat contact surfaces: Ra = 1.6µm, Fluid: helium; Fluid pressure: 30bar, inlet temperature: 300 C; Fluid velocity: 24m/s (HTC of 1175W/m².K); Material: SS for the holder and subholder, inconel 718 for the adjusting tie-rod and hinges; Temperature of the DSM coolant: 100 C and 70 C; Cooling channel: *For all contacts excepted those with mesh 18. Oktober 2011 Folie 14
Second estimation - conductance from contact pressure Contact pressures calculated from the M8 bolt preload of 400MPa [6]: Tool I created to calculate the contact conductance from the contact pressure [7]: 18. Oktober 2011 Folie 15
Second estimation - definition of the conductance at each contact (1) At the adjusting tie rod (1-2/3 link): 3 1 2 For a M16 inconel 718 screw (preload F is 80% of the admissible load): Admissible load: S mb *A n = 56kN [5] F = 44kN Resulting pressure between engaged threads [5]: Real thread contacts Ansys thread equivalent contacts Where N = 44000N, p = 2mm, d = 16mm, D = 13.835mm, Le = 8mm (short nut), 14mm (long nut); p fn = 216MPa (short nut), 123MPa (long nut); Equivalent between the cylinder in contact (Ansys interpretation): 216*203/402 = 109MPa (short nut) 123*355/704 = 62MPa (long nut) 9910W/m².K [7] 7050W/m².K [7] 18. Oktober 2011 Folie 16
Second estimation - definition of the conductance at each contact (2) At the adjusting tie rod (2-3 link): 1 2 Preload: 44kN; S(2/3 link) = π*(24²-16.433²)/4 = 240mm² Contact pressure: 183MPa 13600W/m².K [7] 3 18. Oktober 2011 Folie 17
Second estimation: α - analysis of cooling temperature at support For plasma operation, the cooling temperature of the support would be reduced from 100 C to 70 C. Impact of this reduction on the α angle: Impact negligible. 18. Oktober 2011 Folie 18
Second estimation: α - analysis of the contact conductance The M1 tilting during operation (α angle) has been analyzed considering, at the hinge contacts, low conductance of 500W/m².K ( low ) and calculated [7] from the contact pressure [6] taking into account the bolt preload of 400MPa ( real ): Relatively important impact The contact conductance between part is a critical parameter for the α angle. 18. Oktober 2011 Folie 19
Third estimation: α and thermal analysis as function of the interfaces at hinges Model: Neutron loads: 0.3W/cm 3 for M1, 0.24W/cm 3 for the other parts Conductance at hinges considering contact pressure with: contacts {1,2,3}: inc.718/ss (case 1), contacts {1,2,3}: Cu/SS (case 2), Conductance at mesh: 10000W/m².K; Fluid: helium; Fluid pressure: 30bar, inlet temperature: 300 C; Fluid velocity: 24m/s (HTC of 1175W/m².K); Material: SS for the holder and subholder, inconel 718 for the adjusting tie-rod and hinges; Temperature of the support coolant: 70 C; Cooling channel: 3 2 1 18. Oktober 2011 Folie 20
Third estimation - temperature distribution and helium overheating 2 1 3 Case 1: contacts {1,2,3}: Inc718/SS Case 2: contacts {1,2,3}: SS/Cu Maximal temperature at M1: 345 C; Slightly lower temperature for the case 2; 18. Oktober 2011 Folie 21 Helium overheating for both cases: 24 C.
Third estimation: α analysis of the interfaces at hinges 2 1 3 From thermal and α angle point of view, the copper interlayer at contacts {1,2,3} doesn t have interest, but may have from thermal stresses point of view. 18. Oktober 2011 Folie 22
Fourth estimation: analysis of the chosen model Model: Neutron loads: 0.3W/cm 3 for M1, 0.24W/cm 3 for the other parts Conductance at hinges considering contact pressure with Inc.718/SS interfaces (case 1 of the third analysis), Conductance at mesh: 10000 and 500W/m².K; Fluid: helium; Fluid pressure: 30bar, inlet temperature: 300 C and 260 C; Fluid velocity: 24m/s (HTC of 1175W/m².K); Material: SS for the holder and subholder, inconel 718 for the adjusting tie-rod and hinges; Temperature of the support coolant: 70 C; Cooling channel: 18. Oktober 2011 Folie 23
Fourth estimation: M1 local curvature radius, distortion and tilting Model with copper interlayer at contacts {1,2,3} 2 1 3 Minimum curvature radius: 900m, distortion: 5µm, M1 tilting (α): 0.57mrad, M1 tilting (RT/operation): 1.024mrad. 18. Oktober 2011 Folie 24
Fourth estimation: low conductance at mesh In case of low conductance at mesh (500W/m².K), the maximal temperature at mirror increases to 384 C. In this case the coolant inlet temperature has to be redefined. Coolant inlet temperature to get 350 C as maximal M1 temperature: 260 C Resulting temperature distribution: 18. Oktober 2011 Folie 25
Conclusions The parametric analysis of the M1 showed that a helium pressure of 30bar with a velocity of 24m/s is suitable; The reference cooling channel showed a slight advantage for the local curvature radius than the alternative one; The contacts (low or real) have important impact on the α angle (mirror tilting); The impact of the support cooling reduction from 100 C to 70 C on the α angle is negligible; For a helium inlet temperature of 300 C, the maximal M1 temperature is 345 C with a helium overheating of 24 C; The copper interlayer insertion at heel/holder contacts has no influence on the α angle, but reduces slightly the temperature at hinges; For the chosen parameters, minimum curvature radius of the M1: 900m; distortion: 5µm, M1 tilting: 0.57mrad (α) and 1.024mrad (RT/operation); The helium inlet temperature should be between 260 C (pessimistic conductance at mesh: 500W/m².K) and 300 C (likely conductance at mesh: 10000W/m².K); The interest of copper interlayer insertion at hinges has to be checked from thermal stress point of view. 18. Oktober 2011 Folie 26
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