Simulation of ICE Lubricated Sliding Contacts - Large Engines
Simulation of ICE Lubricated Sliding Contacts
The design and optimization of lubricated contacts in modern engines presents engineers with new challenges. On the one hand, it is vital for the reliability of the engine to ensure the durability of plain bearings, pistons and piston rings cylinder liner contacts. It must be taken into account that, in addition to the increase of specific power density, operating conditions such as start-stop, cylinder deactivation also the special operating conditions in hybrid systems lead to higher mechanical and thermal loads. These must ultimately be carried by the lubricated contacts.
On the other hand, the lubricated sliding contacts can contribute to further enhance the efficiency of IC-engines by measures to reduce their frictional losses, e.g. by using ultra low-viscosity oils. However these measures carry the risk of durability issues.
To determine the optimal balance between durability and efficiency, you can use simulation models that represent the real physical behavior of these contacts.
Elastohydrodynamic Contact Models Tightly Integrated in Multi-Body Dynamics
The solution we have developed at AVL uses Elastohydrodynamic (EHD) models for various sliding contacts in the ICE. These models incorporate the interaction of structural elasticity with the oil film and are integrated with a strong numerical coupling into our multi-body dynamics software AVL EXCITE™. This guarantees you best possible result accuracy and high calculation efficiency.
To support you in today's analysis tasks, a variety of additional functionalities are important. By using the Average Reynolds approach, influences such as of the contact surface roughness, the roughness orientation on hydrodynamics and mixed lubrication are taken into account. Using an included pre-processing tool, you can derive necessary model parameters from measured roughness of small surface patches.
Lubricated Contact Thermal Behavior
There are several approaches you can use to analyze and investigate the transient thermal behavior of lubricated contacts. These approaches consider the heat generated in the contact by friction, the heat flow between the oil film and the surrounding structure as well as the structural thermal deviations.
Wear and Failure Investigation
During engine running-in phase or in highly loaded regions, wear of the surface material can occur. This can lead to a change in contact behavior or, in serious cases, even to engine failure. You can calculate the cumulative wear by using various wear models and an easy-to-use wear analysis process. In the process, the profiles in the contact area are updated automatically.
This comprehensive solution can be used by you to optimize the design, ensure the durability of the radial/axial bearings of the cranktrain, the camshaft as well as the contacts of the piston and the piston rings with the cylinder liner. It is the first choice in case of failures, to investigate issues such as excessive wear, overheating, seizure and specific issues like bearing shell fretting and fatigue.
You can also use the same models for wear analysis of sliding contacts in valve trains, such as the valve seat and the valve guide contact. Even special bearings like floating bushing bearings of turbochargers can be analyzed in this way in detail, e.g. to verify the ring speed or the oil flow through the bores in the bushings, to compare full and semi-floating designs.
Friction Reduction to Improve Efficiency of Your IC-Engine
Since the EHD contact models calculate both hydrodynamic and asperity contact friction, they are ideal for supporting your design analyses goal to improve the efficiency of the ICE by reducing friction losses.
Via an interface, the friction losses depending on engine speed and load are exported directly to our drive cycle simulation solution. This allows you to directly calculate the influence of design measures on fuel consumption and emissions and thus verify their effectiveness.
AVL offers an excellent solution for the design and failure analysis of IC-engine lubricated contacts. Key functionalities are:
- High computational efficiency and accuracy
- Surface contact parameters optionally based on measurements
- Several options for thermal contact analysis
- Automated wear analysis workflow