In-Situ Measurements of the Piston and Connecting Rod Dynamics Correlated with TEHL-Simulation Techniques

Paper #:
  • 2017-24-0157

Published:
  • 2017-09-04
Abstract:
High combustion pressure in combination with high pressure gradient, as they e.g. can be evoked by high efficient combustion systems and e.g. by alternative fuels, acts as broadband excitation force which stimulates natural vibrations of piston, conrod and crankshaft during engine operation. Starting from the combustion chamber the assembly of piston, conrod and crankshaft and the main bearings represent the system of internal vibration transfer. To generate exact input and validation values for simulation models of structural dynamic and elastohydrodynamic coupled multi-body systems, experimental investigations are done. These are carried out on a 1.5-l inline four cylinder Euro 6 Diesel engine. The modal behavior of the system was examined in detail in simulation and test as a basis for the investigations. In an anechoic test bench combustion pressure, airborne and structure-borne noises are measured to identify the engine´s vibrational behaviour. To understand the behaviour of the conrod as the key component in more detail its elongation, using semiconductor strain gauges at the conrod shank and a linkage system, is also measured. Furthermore temperature measurements of piston and liner under fired conditions, allows the determination of their warm contours for a better geometrical description. Variation of injection timing and conrod stiffness allows the basic adjustment of the simulation model. In a further step the simulation model is calibrated by the results of the measurement of the qualitative oil content in the gap between the liner and the piston. For this purpose a combined gap measurement system with specifically developed and mechanically treated sensors after installation is used. Finally the elastohydrodynamic simulation model is extended by a new software component to a so called thermo elastohydrodynamic coupled multi-body system. This leads, especially on Diesel engines, to an improved robustness of the NVH versus emission trade-off.
Also in:
  • SAE International Journal of Engines - V126-3EJ
  • SAE International Journal of Engines - V127-3EJ
  • SAE International Journal of Engines - V126-3
  • SAE International Journal of Engines - V127-3
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