Today’s trend of combustion engine development for cars is characterized with; high torque, low engine speed, low weight, high degree of cyclic irregularity, low excitation frequency due to fewer cylinders active e.g. 4-cylinder or less.
This implies in respect of vibrations that it is crucial to control powertrain rigid body modes and place these were they cannot be reached and induced by the low exciting harmonic frequencies for low engine speeds or idling. It is also important to control the overall flexible vibration modes.
A mathematical CAE model is created in simulation software AVL-EXCITE in order to handle the vibration phenomenon as a first step. But it is absolutely necessary to “verify” these models with real measurements in respect of NVH and if needed upgrade the CAE model if there are detected deviations. The NVH-test is done with testing tool DEWESoft.
The purpose of below paper is to do model verification on a concrete example in respect of powertrain vibrations. Volvo Cars in-line 4-cylinder VEA diesel engine in rig installation is the object for the paper of model verification.
Method of this work has been to do simultaneously NVH measurements of vibrations, torque and cylinder pressure traces during different engine load conditions. Also bump test with a modal hammer has been done in order to find rigid body mode frequencies.
The measured cylinder pressure is applied as input to the simulation model in order to have consistent input load between test and simulation. This is important when comparing the output vibrations.
Verify and compare crank angle based time domain vibrations signals from CAE model with NVH-testing on a real engine. This is the results of the work.