Mechanics, Friction & Noise
Vibrations in the piston conrod lead to unwanted noise in modern combustion engines with self-ignition. The diesel knock or rattle is the best-known example. The aim of this project was to identify the causes of noise and to derive measures to prevent it. To this aim, numerous metrological investigations were carried out to stimulate the crankcases over the piston swing as well as to stimulate and transfer combustion noise over the piston con-rod. The newly developed simulation model formed the contact forces and the component vibrations in the crank drive and in the piston/cylinder contact and also considered transient thermal conditions. With the help of this model, the causes for noise could be identified and the effect of constructive alternatives determined. In addition, the simulation tool was used for elasto-hydrodynamic coupled multi-body systems.
» We have gained a comprehensive understanding of the dynamic of the piston conrod. With this knowledge, the FVV makes a great contribution to the development of acoustically-optimised engines. «
The project focus was on analysing the dynamic-elastic behaviour of the piston-pin-conrod assembly.
Natural vibration forms of the examined cylinder's rotor assembly components.
Applied measurement for determining component temperatures and cable suspension for recording connecting rod length vibrations in fired operation.
Modern self-ignition combustion engines show fast conversion rates with high-pressure gradients in certain operating points. Interfering noise is created as a result, known for example as diesel knock or rattle. The problem is exacerbated through the use of new design concepts in engine engineering such as downsizing and lightweight construction. The project aims to identify the noise sources and to depict the vibration behaviour in the crank drive in the corresponding transient models.
The stimulation of the crankcase over the piston swing as well as the stimulation and transfer of combustion noise over the piston connecting rod were the focus of the technical investigations. A modal analysis for cranktrain components and assemblies, such as the connecting rod for example, provides information about the system's natural vibration behaviour. On the test stand, the stationary and transient thermal conditions were also determined. They were included as input variables in the simulation model. The newly developed model shows the contact forces and the component vibrations in crank operation and in piston/cylinder contact. It also considers the thermal effects in the lubrication gap and the heat distribution in the engine components.
On the basis of the project results it is possible to describe the dynamic contact and vibration behaviour, especially under thermal variable conditions in the piston con-rod. That includes an experimentally validated simulation model of a modern car’s diesel engine. Moreover, it means that the design of acoustically optimised rotor assembly components is already possible in the digital development process. The user is capable of identifying sources for noise emission and can derive constructive countermeasures (e.g. alternative materials, dimensions and patterns).
Piston Conrod Dynamics I | Measurement and CAE Analysis of the dynamic-elastic behaviour of piston-pin-conrod assembly. The investigation should focus on noise issues, caused by high pressure gradients and on its contribution on disturbing noises on knock-control systems | Project No. 1023 | AiF Funding ID: 15699 N
Piston Conrod Dynamics II | Calculation and technical verification of dynamic contact forces between pistons and cylinder considering transient thermal boundary conditions | Project No. 1174 | AiF Funding ID: 17983 N
Piston Conrod Dynamics - Verification Measurement Piston Travel | Extension of the project "Piston Conrod Dynamics" in order to measure the piston movement to validate the calculations performed with PIMO3D | Project No. 3210
Public & FVV Funding
2009-12-01 to 2012-07-31 I
2010-12-01 to 2011-06-30 Verification Measurement
2014-04-01 to 2016-12-31 II
Dr.-Ing. Harald Stoffels
John Andrews Research Centre | Ford-Werke GmbH
1 | Chair in Automotive Powertrains | Institute for Internal Combustion Engines and Automotive Engineering (IVK) | University of Stuttgart
Head of Research:
Prof. Dr.-Ing. Michael Bargende
I | Dipl.-Ing. Daniel Hrdina
II | Dipl.-Ing. Wolfgang Gross
2 | Department of Machine Elements and Engineering Design | Institute for Powertrain and Automotive Technology (iaf) - University of Kassel
Head of Research:
Prof. Dr.-Ing. Adrian Rienäcker
I | Dipl.-Ing. Florian Felbinger
II | Ahmad Rabanizada, MSc
Konstantin Markstädter, MSc
Research & Technology Performers
Research Association for Combustion Engines eV
Lyoner Strasse 18
60528 Frankfurt am Main
T +49 69 6603 1345