Shape Optimization of Valve Channel with Incompressible to Compressible Simulation for Pressure Loss Calculation

Transcription

1 5 th OpenFOAM Workshop, Chalmers, Gothenburg, Sweden, June 21-24, 2010 Shape Optimization of Valve Channel with Incompressible to Compressible Simulation for Pressure Loss Calculation Seiji KUBO (IHI Corporation) IHI Corporation

2 Introduction of IHI Works : 12 Branches and sales offices in Japan : 22 Overseas offices : 13 Head Office, Tokyo Research & Development IHI Corporation Founded : 1853 Capital : 95,762 million (780 million Euro) Consolidated net sales : 1,350,567 million (10,935 million Euro) Employees : 7,171* As of March 31,2008 1

3 Contents Section 1 Motivation of this research Background Objectives Analysis framework for optimization Section 2 OpenFOAM setup - Utilities - Incompressible to Compressible Simulation Result Conclusion 2

4 Optimization problem 3 levels 13 parameters x12= conditions Total 19,131,876 cases Need huge amount of calculations, anyway!! Utilizing Taguchi orthogonal array parameter case cases x12= 324 conditions Total cases 3

5 Motivation of this research Background How to generate the large number of meshes rapidly? How to shorten the time to solve huge amount of cases? Keywords ~ Orthogonal array ~ License fee ~ Automated procedure 4

6 Background & Objective LNG-BOG reciprocating compressor (LNG: Liquefied Natural Gas, BOG: Boil Off Gas) sheet シート スピンドル バルブプレート (VP) 閉 Valve sheet plate spring Objective inlet guide Close Fully open guide CFD Reduce the pressure loss in valve channel by optimizing the shape of valve channel ガイド 開 バッキングプレート (BP) Valve configuration Pressure loss plate 5

7 Shape optimization outline Plate Design parameter 1 ~ 設計パラメータ出力 ( 損失係数 ) 出力変動出力平均形状 x1 x2 [mm] x3 [mm] x4 [mm] x5 [mm] x6 [mm] x7 [mm] x8 [mm] y1 y2 SN 比 (db) μ 従来形状 D model Initial data OpenFOAM =19,131,876 19,131,876 cases 27 12=324 cases Orthogonal array (L27) Average of pressure loss Coefficient (-) SN ration (db) Factorial experiment Opt. Org. Ave. Original valve Optimal valve Higher lift Tapered edge 6

8 Design parameters 1 7 Plate Total 324 cases!! 3 2 Design parameters 1 Sheet inlet w 6 Plate taper 2 Plate t 7 Sealing taper Lift 4 Sealing w 5 Sheet outlet w 8 Cylinder taper 9 Cylinder hole d 7

9 The automated meshing-to-analysis framework Main flow of optimization 3D-CAD Mesh generation OpenFOAM Evaluation Optimal design Shape modification Automation area Consuming almost all the time for shape modification and its analysis setup = Automation area Focused on this area Construction of the automated meshing-to-analysis framework modefrontier: couple meshing and analysis tool Gridgen: shape modification and re-meshing OpenFOAM 1.6: CFD solver 8

10 The automated meshing-to-analysis framework modefrontier is utilized for coupling mesh-generator and OpenFOAM. Design parameters Orthogonal array (L27) CFD (OpenFOAM) Mesh generation (re-meshing) 9

11 Contents Section 1 Motivation of this research Background Objectives Optimization flow Section 2 OpenFOAM setup - Solver & Utilities - Incompressible to Compressible Simulation Result Conclusion 10

12 Incompressible to compressible simulation Calculation outline Solver for stabilization of compressible flow calculation Solver for obtaining initial outlet pressure simplefoam Control U out rhosimplefoam-u Initial P out Q in Q out =Q t Control P out Q in =Q out =Q t Initial compressible flow distribution Main solver rhosimplefoam-p Coefficient of pressure loss : Main flow : Control 11

13 Incompressible to compressible simulation Demand for this automated CFD procedure of valve channel Stability of calculation so as not to be interrupted Validity of the solution Construction of 3 calculation steps Boundary condition control on the outlet 12

14 simplefoam to rhosimplefoam-u Solver for obtaining initial outlet pressure simplefoam Target mass flow rate of simplefoam U inlet simplefoam = Q ρa t inlet Given value for design Initial P out boundaryandinternalset-1-for-ihi Control U out Q in Q out =Q t Solver for stabilization of compressible flow calculation rhosimplefoam-u Initial compressible flow distribution Outlet pressure, when Q t flows Internal epsilon, k, nut, p, phi and U Boundary condition simplefoam Inlet: VELOCITY-INLET (U in ) Outlet: OUTFLOW (P st =0 [Pa](G)) rhosimplefoam-u Inlet: Pressure-inlet (P st ) Outlet: Velocity-outlet (U out ) 13

15 rhosimplefoam-u to rhosimplefoam-p Compressible flow distribution is calculated by [rhosimplefoam-p]. But [rhosimplefoam-p] is unstable solver for valve model. Solver for stabilization of compressible flow calculation [rhosimplefoam-u] is utilized for getting initial compressible flow distribution. Control U out Q in Q out =Q t Control P out rhosimplefoam-u Initial compressible flow distribution rhosimplefoam-p Main solver boundaryandinternalset-2-for-ihi Outlet pressure, when Q t flows Internal p, phi and U Boundary condition rhosimplefoam-p Inlet: Pressure-inlet (P st ) Outlet: Pressure-outlet (P st ) Q in =Q out =Q t Coefficient of pressure loss The coefficient of pressure loss in valve is obtained!! 14

16 Incompressible to compressible simulation Boundary condition control Pressure outlet is controlled as linear sequence. Deviation of Q = (Q current -Q t )/Q t Correct dp out [Pa] x (Deviation of Q) -10 For example Residual history under P out control When deviation of Q is more than 10%, add 10 [Pa] to P out in order to decrease Q out current 15

17 Incompressible to compressible simulation Solver (OpenFOAM 1.6) Incompressible flow solver simplefoam-ihi Compressible flow solver rhosimplefoam-u-ihi rhosimplefoam-p-ihi Utilities boundaryandinternalset-1-for-ihi boundaryandinternalset-2-for-ihi Cell count: about 0.6 Mcells Fluid : CH 4 (-196 degrees) /boundary: 5( ) WALL{ type wall; nfaces 3229; startface 81840;} OUTFLOW{ type patch; nfaces 20; startface 85069;} SYMMETRY2{ type wedge; nfaces 51837; startface 85089;} SYMMETRY1{ type wedge; nfaces 51837; startface ;} VELOCITY-INLET{ type patch; nfaces 20; startface ;} 16

18 Efficiency of simulation Time for analysis System for calculation CPU Memory AMD Opteron 8350 (2.0 GHz) QuadcoreX4 DDR GB X 16 Manual/serial Automated/simultaneous Mesh generation Few hours/case 5 seconds/case CFD (324 cases) 40 days 3 days 40 days for serial calculation with general CFD. Because of open source (free of charge) Only 3 days for simultaneous 54 cases calculation with OpenFOAM 17

19 Result Optimal gas flow Original valve Optimal valve Flow direction of optimal valve becomes straight compared to original one. Smaller separation Lower pressure loss 18

20 Result Effect of improvement Comparison with ζ of original and optimal shape Coefficient of pressure loss ratio [-] Optimal Original Velocity magnitude [m/s] Coefficient of pressure loss decreases about 25 % 19

21 Conclusion In this study, we have achieved below. Construction of the automated framework, which couples mesh generator and CFD solver Consistent calculation flow of incompressible to compressible analysis Automatic control of outlet pressure so as to obtain target mass flow rate Achievement of shape optimization in 3days!! 20

22 Conclusion We can get the optimal valve shape making the study with orthogonal array depending on Taguchi method. In case of designing the industrial machinery utilizing CFD within a realistic time, the automated framework is necessary for shortening the turn-around time. As the application of OpenFOAM in industrial machinery, it can be useful for the CFD solver for optimization and large parallel/simultaneous calculation. 21