Ensuring that oil does not pass by valve stem seals in more than the allowed quantities is a critical design element for ensuring the quality and reliability of vehicle engines. This function of the valve stem seal is called “oil metering.” Design engineers must evaluate oil flow against hydrodynamic pressure while taking into account the lubrication of the valve stem. If there is too much oil, it will cause unwanted emissions and deposits on the parts; if there is too little oil, it will cause excessive wear of the valve seat, face, and guide. Engineers in the Sealing Products Group at Dana Holding Corporation used FlowVision-HPC from Capvidia combined with Abaqus FEA software from SIMULIA to simulate oil leakage flow via the valve stem seal at different engine operation conditions and investigate changes in characteristics due to the aging process. The unique capabilities of FlowVision-HPC, combined with Abaqus FEA, enable engineers to solve heavily coupled fluid-structure interaction problems.
In this example, the oil flow in the valve stem seal was calculated and the oil metering was represented as a function of time, engine speed, and rubber aging. The coupled simulation leveraged the Sub-Grid Geometry Resolution (SGGR) method used in FlowVision for grid generation. The SGGR method provided a natural link between the CFD grid and FEA mesh. The FlowVision Clearance Model was then used to simulate the flow in the thin channel between the stem and the seal. Step pressures were transferred to Abaqus, which calculated the resulting deformation of the seal. The coupled fluid-structure interaction analysis enabled Dana engineers to identify design modifications to improve sealing performance. 
| Fluid-Structure Interaction occurs in the zone of large seal deformation contacting the oscillating valve stem through a thin oil film. On each FSI iteration, step pressure calculated in FlowVision is transferred as a new load case to Abaqus, which calculates resulting deformation of the rubber seal.
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“The coupled Abaqus-FlowVision simulation mimics exactly the physics and experimental setup, giving us faster results at significantly lower cost,” stated Frank Popielas, Manager of Advanced Engineering for Dana’s Sealing Products Group. “We can simulate the use of new materials and design configurations to evaluate their characteristics and overall performance. Comparative studies such as ranking can be performed to get better insight of the performance in different operation conditions and design variants.”
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