Non-linear dynamics of engine mechanisms with a flexible connecting rod

Abstract

The present study investigates the dynamic response of single-cylinder reciprocating engines. In particular, simpli ed models of the classical slider-crank mechanism are examined, which take into account the exibility of the connecting rod. Moreover, a main new feature of these models is that both the driving and the resisting moments are expressed as functions of the crankshaft motion, instead of prescribing the rotation of the crank. The equations of motion are rst derived by application of Hamilton's principle. These equations are then discretized geometrically and put in their nal form by applying Galerkin's method. Owing to the large rotations exhibited by the mechanism members and the form of the driving and the resisting moments, the resulting equations of motion involve strong non-linearities. As a consequence, their solution is obtained in both the time and the frequency domain by employing appropriate numerical methodologies. In particular, these methodologies include either determination of transient response by employing direct integration techniques or direct determination of complete branches of periodic steady state response by applying suitable methodologies. The rst set of numerical results refers to the special case where the angular velocity of the engine crank can be considered as virtually constant. This case can be analysed more easily and provides valuable insight into some important aspects of the system dynamics. Then, the emphasis is shifted to the general case, corresponding to non-ideal forcing conditions. In all cases, the attention is focused on examining the in uence of the parameters of the system on its dynamics during intervals with transient (run-up or run-down) or under periodic steady state conditions.

Dynamics of the cutting mechanism with flexible support and non-ideal forcing

“…Most of the investigation refers to mechanisms with rigid members whose crankshaft is supported rigidly and rotates with a constant angular velocity (see for example [2]). Most of these studies are analytical or numerical and investigate various mechanical aspects of the dynamical response and stability of slider-crank mechanism [3]. In the papers [4] and [5] the extension of the problem is done by including the non-ideal forcing and flexible supporting of the crankshaft.…”

“…Direct integration technique gives the description of the run-up and close-down response of the mechanism. Steady-state periodic Mechanism and Machine Theory 58 (2012) [1][2][3][4][5][6][7][8][9][10][11][12] motions are obtained numerically, but also analytically for some special cases. Motion is compared with that for the case of ideal forcing when the angular velocity of the input element is constant.…”

Dynamic effects of the power-conversion module in a reciprocating engine

“…Analytical studies on slider-crank mechanisms with flexible connecting rods of constant geometry have been carried out by Goudas [11] and Fung [12]. However, both did not study the effect of the sharpness of excitation on the response of the system, and considered piston and pin as rigid parts.…”

On the impact of the pressure rise rate on piston and connecting rod dynamics in internal combustion engines

“…In addition, Goudas did a similar investigation while carrying out parametric studies for different engine speeds and length of the connecting rod. He investigated a flexible connecting rod of a constant rectangular profile, studying the first bending mode of the connecting rod, and the response at different speeds and for different length of the connecting rod [21]. The slider-crank mechanism was investigated theoretically in a similar way by Fung, who also considered transverse and longitudinal vibratory effects of the connecting rod [22].…”