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Modelling and simulation of hydraulic motor tribology

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Presentation on theme: "Modelling and simulation of hydraulic motor tribology"— Presentation transcript:

1 Modelling and simulation of hydraulic motor tribology
Patrik Isaksson

2 Agenda Introduction Mixed lubrication model Test rig-validation
Micro EHL Tribology modeling - Project leakage reduction

3 Introduction-tribological interfaces
Piston assembly Distributor plate Seals Rolling element bearings

4 Tribology of hydraulic motor
Wide speed and load range High loads-EHL All lubrication regimes has to be considered

5 Modelling tribology of hydraulic motors
Fluid dynamics Thin film approximation of Reynolds equation is used Structural deformation High loads Fluid property model Viscosity dependence Surface roughness -when film thickness is small

6 Mixed lubrication-modelling strategy
Separate the problem into two different scales Local scale representing surface roughness Global scale representing the piston bearing structure Deformation is calculated on both scales Local scale Global scale

7 Mixed lubrication model
Modified Reynolds equation Incorporating the effects of the local scale fluid flow through flow factors

8 Mixed lubrication model-friction calculation
Friction is calculated as the sum of friction from asperity contact and hydrodynamic friction

9 Simulation software Commercial software package-COMSOL
Based on finite element method Facilitates flexibility as a design tool Fluid dynamics and other needed equations can easily be implemented Full system solution approach

10 Test rig-validation Friction, leakage and oil film pressure is measured in the roller-piston interface

11 Validation-modeling test rig setup
Mixed lubrication model applied in roller/piston interface

12 Validation-Oil film pressure

13 Validation-Leakage

14 Validation-mixed lubrication
Movie clip

15 Lift off zone Not always very good correlation, some effect and/or input is missing

16 Micro EHL Deterministic EHL model of high pressure zone with transverse ”roughness”

17 Micro EHL Micro EHL will influence transition between full film and mixed/boundary

18 Tribology modeling - Project leakage reduction
Task: Reduce leakage in piston to 50% Keep low friction

19 Project leakage reduction-result
New piston design in production


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