Virtual ICE Development - Durability and NVH - AST Product Releases
Release 2020 R1
Virtual ICE Development - Durability and NVH
An update to the AVL simulation solution for IC engine development
The latest release of AVL’s simulation solution for IC engine development includes various new capabilities for durability and NVH analysis. It is designed for use with IC engines, ICE-based and HEV power units.
This new release focuses on further enhancing the elastohydrodynamic models for the lubricated contacts in IC engines. Other new features have been included to extend and improve applications in the field of NVH. This is a summary of the main capabilities of 2020 R1, and more details of this release can be found in the product release notes of AVL EXCITE™ 2020 R1.
Analysis of Lubricated Contacts
Enhanced Integrated Thermal Analysis Approach
AVL EXCITE™ Power Unit’s internal, integrated approach has been considerably reworked and enhanced. It now considers the frictional heat generated in elastohydrodynamic (EHD) contact models and the heat flow in the structure around radial/axial sliders.
A new feature – temperature convergence acceleration – is an automated workflow that iteratively calculates the accumulated heat flow in each joint. It does this for one cycle, and then performs a transient local structure heat-up calculation that yields structure temperatures for the next cycle.
The benefits of this new feature are:
- It is a stable and easy-to-use solution without non-physical parameters
- It is much faster -– converged temperatures are usually reached in 8-10 load cycles
- It is more accurate due to affordable calculation time until temperature convergence
Example crankshaft main bearing: convergence with new feature reached after 8 engine cycles
Bearing Fretting Evaluation
In this latest release, the EXCITE Power Unit Utility feature called ‘Fretting Analysis’ has been transferred to two more user-friendly AVL COMPOSE™ Apps – ‘Redefine Node Coordinates’ and ‘Evaluation of Results.’
The first is used to consider the hardware-applied re-machining of the bearing bore after its assembly in the simulation model. The second evaluates various fretting indicators based on the results of an Abaqus non-linear contact analysis of the bearing shell back to bore surface. For this functionality EXCITE pre-calculates the bearing oil film pressure values for use as a boundary condition.
An additional benefit of the new implementation is extended 3D post-processing. This includes a visual control of imported displacements and all fretting indicator parameters. The values which are directly imported from the Abaqus .odb file are: Fretting Damage Parameter (FDP), Fretting Indication Parameter (FIP), and Fretting Fatigue Parameter (FFP).
Additional Wear Model According to the Fleischer approach
The latest release features an optional new wear model that is based on the Fleischer approach. It operates on the assumption that a tribo-pair has a hard and a soft component in contact. Once the energy generated by the tribo-pair through friction reaches a critical value, it causes a ‘break out’ of wear particles.
The Fleischer wear model is available for all EXCITE Power Unit elastohydrodynamic joints (slider bearings and piston-liner contact) as an alternative to the Archard wear model.
Different Surface Contact Parameters for EHD Slider Bearings
To consider the influence of different local surface conditions on bearing behavior, multiple surface contact patches can be defined with different parameters. These can be applied to the Contact Model (model type and parameter), the Average Reynolds Equation, the Surface Contact Layer, and the Heat Transfer Model.
Piston Ring Tribology and Wear Analysis
More accurate results for friction and wear investigations have been enabled in the latest release, with the inclusion of new options for the piston ring top/bottom flank to piston groove contact of EXCITE Piston&Rings. The same optional asperity contact models that are used for ring running face-liner (except Average Reynolds) are now available for the following: Greenwood/Tripp, User Defined, or based on data imported from Micro-Contact Analysis.
NVH Analysis of IC Engines and Power Units
New Modeling Option for Viscous Dampers
A new viscous dampers option has been included for EXCITE Power Unit models. It uses the physical Bingham viscosity approach for cyclic-transient torsional vibration analysis. As well as viscosity, the elastic shear modulus and the shear stress limit (plastification) can also be considered with this approach.
Sound Radiation Calculation – Improved Automated Meshing
The latest version of EXCITE Acoustics keeps the so-called Block Mesher automated acoustic meshing approach, while providing a new non-Convex Mesher. Acoustic meshes using this type of mesh can lead to results that are closer to vibrating structural meshes. The benefit of this approach is a better consideration of the influence of complex structure topology on sound radiation and, furthermore, it improves the accuracy of results in the near-field close to the vibrating structure.
Example turbocharger housing: Block Mesh versus non-Convex Mesh
Enhancement of Power Unit Mount Layout Tool
In this latest release, the mount layout tool now includes the option to consider systems with two rigid bodies connected by mounts. This can used to model systems such as a power unit on a bedplate, a typical large engine configuration, or the vehicle body. For such systems the modal analysis gives 12 natural frequencies and normal modes, and static/dynamic results for each of the bodies.
Example: Power unit on a bedplate
Torsional Vibration Damper Layout
The COMPOSE App for TVD temperature calculations, based on an EXCITE Designer model, has now been enhanced. This latest version can now consider viscous damper stiffness and damping parameters that are temperature as well as frequency dependent. Further improvements include analysis of torsional stiffness and viscous damping versus engine speed. Thanks to an extension in EXCITE Designer, it can now also be used for torsional vibration analysis in order to factor in engine speed dependency, and offers considerably improved calculation performance compared to version 2019 R2.
Example: Torsional vibration analysis with engine speed dependent TVD stiffness and damping