Release Notes 2021 R2

Virtual ICE Development - Durability and NVH

Updates and improvements to AVL’s simulation solution

Committed to our customers, always having the global automotive markets and trends as well as the current legal guidelines in mind, we at AVL are constantly working on the future development of our solutions, services and methods. With our second release 2021, we are again launching new highlights in the field of ICE Durability an NVH, which we would like to present to you here.

Lubricated Sliding Contact Analysis

Slider Bearing Internal Thermal Analysis

Extended Thermal Boundary Condition Options

To further improve the accuracy of the calculated local structure and oil temperatures, the possibilities to define initial and boundary conditions are extended. For the internal used boundary structure (ring) of each connected body, e.g. shell and journal, used by the approach, you can now define individual boundary conditions for the ring surfaces. These boundary conditions can be either of the type "Fixed temperature", "Fixed heat flux", "Heat transfer coefficient" or "Adiabatic". Input are temperature, heat flux or heat transfer coefficient (HTC) profiles.

Figure 1: Structural temperature result using enhanced thermal boundary conditions

Temperature Equilibrium as Initialization Step

In case structural heat up should not be calculated until the thermal stationary state is given, a new option is provided which allows you to obtain mechanical results that are unaffected by any temperature changes.
The structure heat up is now treated as a thermal initialization step. The initialization phase ends either when thermal stationary conditions are converged out, or new – a predefined number of heat cycles – is reached.
The thermal conditions reached are then used for a final standard dynamics calculation of a few engine cycles at stationary temperature conditions.

Piston Ring Analysis – Additional Ring End Gap Designs

Two new ring end gap designs have been introduced, the 'Stepped' and the 'Double Sealed' end gap.
For both designs, the dynamic axial displacements of the ring ends are considered when using the 3D ring model, and for the double sealed design, the radial displacement is also taken into account.
The gas flow coefficient for the ring end gap has been replaced by three separate gas flow coefficients, one for each throttle at the ring end gap. This allows you to adjust the model to even more demanding geometric designs that are not directly covered by the general designs.

Figure 2: Sketch of stepped and double sealed ring end gap designs


Valve Train Analysis

Overhead Valve (OHV) Trainwith Swing Arm

The OHV train templates available in AVL EXCITE™ Power Unit and AVL EXCITE™ Valve now support swing arm configuration in addition to the tappet configuration already available. The contact between lever and pushrod is considered by a ball/pen contact. If necessary, hydraulic lash adjuster insets can be used at the pushrod-side lever arm. Other configuration options, such as multi-valve actuation with and without bridges, are also possible with the new configuration.

Figure 3: Overhead valve train configuration with swing lever



AVL EXCITE™ Power Unit - Interface to Model.CONNECT™

The new "Model.CONNECT Element" component has been implemented in EXCITE Power Unit, providing an interface for co-simulations via AVL’s neutral model integration and co-simulation platform that connects virtual and real components. This enables you to co-simulate EXCITE with a wide range of tools accessible through Model.CONNECT, e.g. AVL CRUISE™ M, MATLAB®/Simulink® and Python scripts.
The EXCITE interface is similar to the already existing MATLAB® and FMU interfaces with the main difference - EXCITE is just one client in the co-simulation, started and controlled by Model.CONNECT.
With this release version, the interface supports applications that require motion quantities of bodies and sensors provided by EXCITE and receive forces and moments from tools connected via Model.CONNECT. The data is exchanged in EXCITE time steps for time-based simulations.

Figure 4: Example – AVL EXCITE™ model with several Model.CONNECT™ elements


Concept Analysis

Torsional Vibration Damper Analysis

Rubber TVD Durability – Geometry-Based Stiffness and Stress Calculation

Using an additional geometry input, you can calculate the dynamic shear stress by AVL EXCITE™ Designer as a result of the torsional vibration analysis. Furthermore, the geometry can be used together with the rubber shear modulus to determine the torsional stiffness of the TVD.
Three basic design variants are implemented: flat, cylindrical, or TVD with conical rubber layer. In case of strongly deviating designs, the moment of resistance to torsion and/or the gap dimensional factor can be adjusted manually.

TVD Temperature Calculation – Option for Calibration

The TVD temperature calculation App provides now two more result curves, outer surface and maximum temperature.
In order to better consider the influence of real TVD design and surrounding air boundary conditions by the simplified model, as well as to achieve a higher accuracy, especially regarding amplitudes, the simulation results can be calibrated be measurement data.
Based on the additional input of the measured temperature on the TVD outer surface for a certain engine speed, a temperature correction factor is determined.

Figure 5: TVD temperature vs speed before (left) and after calibration (right)