Simulation of a Vane-type Oil Pump Transient Computation with Morphing Thomas Fischer, Daimler AG, Berlin Plant, ES Dr. Ulrich Stubbemann, Daimler AG, Berlin Plant, ES Jan Fischer, Daimler AG, Berlin Plant, EV/T Kai Fellmann, Daimler AG, Berlin Plant, EH
Outline 1. Introduction • Structure and Function of the Vane-type Pump • Assignment for the CFD Simulation with STAR-CCM+ 2. Construction of the Simulation Model in STAR-CCM+ 3. Selected Results of the Simulation 4. Summary 2 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
Introduction Structure and Function of the Vane-type Pump Assignment for the CFD Simulation with STAR-CCM+ 3 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
1. Introduction Structure and Function of the Vane-type Pump Pressure Translation Rotation delivery side Intake side The fluid is sucked in and displaced by the change in volume of the chambers. Motions •Rotation of the pump rotor and the vanes •Translation of the vanes in the pump rotor 4 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
1. Introduction / Assignment for the CFD Simulation Pressure Pulsation of the Vane-type Pump 12 ] r Graph of the pressure in a delivery a b 10 [ e r 8 u s s chamber versus the time e 6 r p 4 2 Measure 0 The pressure curve is governed by the -2 -4 Inlet Outlet 67.5 67.51 67.52 67.53 67.54 67.55 connection of the chamber with the 14 ] r a b 12 [ inlet or outlet. e r 10 u s s e 8 r p 6 This pressure change is called 4 1D Simulation 2 0 pressure pulsation. -2 7.52 7.528 7.536 7.544 7.552 7.56 time [s] Assignment for the CFD Simulation with STAR-CCM+ • How high is the dynamic component stress because of the pressure pulsation? • Can the effect of modifying the geometry on the pulsation be assessed without elaborate measurements? 5 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
1. Introduction / Assignment for the CFD Simulation Cavitation Damage at the Set Collars The endurance test yields cavitation damage at the set collars of the vane-type oil pump. Assignment for the CFD Simulation with STAR-CCM+ • What mechanism causes the implosion of the gas bubbles at this position? • Can the effectiveness of geometrical modifications be assessed without elaborate endurance testing? 6 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
1. Introduction / Assignment for the CFD Simulation Pressure Activation of the Vanes The vane must lie on the contact surface of the set collar in each operating state. Pressure activation of The vanes are therefore activated by the vanes pressure at the undersides. Assignment for the CFD Simulation with STAR-CCM+ • How must the oil feed be arranged in order to obtain an optimal pressure distribution in the interior of the rotor? • What pressure (force) is actually applied to the undersides of the vanes? 7 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
Construction of the Simulation Model in STAR-CCM+ Construction of the model Preparation of the simulation Sequential control 8 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
2. Model Construction Basic Settings for the Mesh and Physical Continua Fixed Geometry Mesh region regions Morphed region Interfaces Physical continuum Segregated flow User-defined density (compressible fluid) Implicit unsteady Mesh continuum Polyhedral mesher Prism layer mesher Surface remesher 9 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
2. Model Construction Definitions of the Regions and Motions in STAR-CCM+ •Splitting of the moving region into boundaries •Assignment of the motions to the individual boundaries Morpher: Motion Rigid motion: Rotation Incremental displacement: Table with local coordinate system 10 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
2. Model Construction Definitions of the Regions and Motions in STAR-CCM+ 10° 18° •The mesh quality deteriorates as the rotational angle increases. Remeshing occurs if impermissible cells emerge. •The boundaries are deformed. The deformation of the boundaries is retained in the remeshing. To keep the deformation within acceptable limits, new meshes must be imported. 11 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
2. Model Construction Preparation of the Parametrized Surface Model in CAD •The boundaries are generated in the CAD model - Splitting and naming the boundaries is not required in STAR-CCM+. - Meshes can be automatically generated with little effort for fixed positions. • The CAD model is parameterized - The positions of the geometry can be easily generated in the parameterized CAD model. 12 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
2. Model Construction Preparation of the Control Point Tables • Analytical computation of the control point coordinates from the geometry data of the pump • Computed are tables for the translation of the vanes and the rotation of the chamber • The number of control points is critical; to be weighed is the geometrical distortion compared with the CPU time for the morphing • For the rotational range of the fluid, control points for 1° rotational angle and 1 mm chamber depth are computed ~8300 points • In addition for the vane displacement, one point for each vane and each time increment 13 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
2. Model Construction Sequential Control via JavaScript Start Yes > 5 turns? End Reset history Morphing No < 1 turn? Yes Remeshing Error? Read prepared Mesh Simulation step < 10°? Yes 14 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
2. Model Construction Motion of the Mesh Assessment of the mesh quality by means of a test calculation. 15 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
Selected Results of the Simulation 16 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
3. Results Flow Rates in Selected Levels Section plane in the area of the observed cavitation damage The area of the observed cavitation damage is characterized by a directed flow. 17 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
3. Results Flow Rate Distribution in the Selected Section Plane and Pressure Distribution at the Set Collar Section plane in the area of the observed cavitation damage The area of the observed cavitation damage is characterized by a directed flow. 18 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
3. Results Average Pressures at Selected Surfaces Pressure Distribution 10 9 T=120 °C n=3300 rpm 8 7 6 pressure [bar] pressure pump 5 outlet 4 pressure vane top side 3 pressure vane bottom side 2 1 pressure vane front side 0 0,00E+00 4,55E-03 9,09E-03 1,36E-02 1,82E-02 time [s] The pressures averaged at the surfaces yield the component stress due to the pressure pulsation. The pressure activation of the vanes is computationally optimized, significantly reducing the testing labor. 19 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
4. Summary Summary • The presented procedure requires about 14 days for constructing the CFD model and calculating an operating point. • The coupled preparation of the meshes in the CAD system and in STAR-CCM+, combined with the specified morpher settings, allows good mesh quality of the moving region. • The results of the computation provide answers to the questions raised: - The dynamic component stress due to pressure pulsation is computed as a surface integral. - The pressure activation of the vanes is computed and optimized. - Flow phenomena leading to cavitation damage become visible. - Geometrical variations can be assessed computationally. • The transient CFD computation of the pumps significantly reduces testing labor. • The computation was introduced as a standard in the pump development. 20 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
Thank you for your attention 21 Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012
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