Abstract
Piston impacts against the cylinder liner are the most significant sources of mechanical noise in internal combustion (IC) engines. Traditionally, the severity of impacts is reduced through the modification of physical and geometrical characteristics of components in the piston assembly. These methods effectively reduce power losses at certain engine operating conditions. Frictional losses and piston impact noise are inversely proportional. Hence, the reduction in power loss leads to louder piston impact noise. An alternative method that is robust to fluctuations in the engine operating conditions is anticipated to improve the engine's noise, vibration and harshness (NVH) performance, while exacerbation in power loss remains within the limits of conventional methods. The concept of targeted energy transfer (TET) through the use of nonlinear energy sink (NES) is relatively new and its application in automotive powertrains has not been demonstrated yet. In this paper, a TET device is conceptually designed and optimized through a series of parametric studies. The dynamic response and power loss of a piston model equipped with this nonlinear energy sink is investigated. Numerical studies have shown a potential in reducing the severity of impact dynamics by controlling the piston's secondary motion.
Highlights
The dominance of internal combustion (IC) engines in transport raises concerns about their environmental effects, such as fuel supply, air pollution and noise emissions
An alternative method that is robust to fluctuations in engine operating conditions is anticipated to improve the engine’s NVH performance, whilst exacerbation in power loss remains within the limits of conventional methods
The concept of targeted energy transfer is studied for reducing piston’s secondary motion for the first time. This analysis comprises the nonlinear dynamics of the piston and the energy absorber
Summary
The dominance of internal combustion (IC) engines in transport raises concerns about their environmental effects, such as fuel supply, air pollution and noise emissions. The influential factors are classified to those related to the engine operating conditions and those related to the geometrical and physical characteristics of the piston assembly components. Piston impacts are conventionally controlled through the geometrical and physical factors, since fluctuation in engine operating conditions is essential for vehicle’s performance. A passive control method that is robust to engine operating conditions is highly favoured to reduce the piston impact severity, whilst the friction (power) losses remain below the limits of the conventional control methods. The NES is an oscillator with essential stiffness nonlinearity possessing negligible or very small linear damping [14] This class of nonlinear systems can effectively capture transient resonances, transfer broadband vibration energy between the NES and its primary system and localise the vibrations to nonlinear normal modes of the NES [14]. Computational parametric studies are commonly exploited to identify NES design parameters such that the oscillations of the primary system are either suppressed or completely eliminated [21, 22]
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