Design and Optimization of Crankshaft Torsional Vibration Damper for a 4-Cylinder 4-Stroke Engine 2008-01-1213
The problem of crankshaft torsional vibrations is inherent to the reciprocating internal combustion engines. Till date, in multi-cylinder internal combustion engines torsional vibrations which increases vibratory torque is the major reason for the failures of crankshaft due to raised fillet stresses. The torque applied to crankshaft is not constant in time, but it varies in a complex manner as a function of crankshaft position for each cylinder. The excitation that causes torsional vibrations of crankshaft is the Gas firing pulse phasing in the cylinders of an engine. The Crankshaft natural frequencies get excited several times through out the operating speed of engine by different components of firing pulse harmonics, called orders of an engine. The vibration amplitudes at these critical speeds are commonly high enough, so that the crankshaft as well as any accessory coupled to the crankshaft may fail.
The study refers to design of optimum torsional vibration damper in size and weight. The parametric study is carried out to study the effects of damper ring inertia, damper stiffness and damping on attenuation of torsional vibration amplitudes. Also revealed here is the use of Damper Characterization Curve (DCC) and Normalized DCC to select optimum damper.
Based on numerical prediction of the crankshaft torsional vibrations and safety factors, optimised parameters for the ring inertia, hub inertia and elastomer properties are arrived at. Controlling the temperature and vibratory torques is critical aspect in designing the TVD (Torsional vibration damper).
The final configuration is tested on an engine dynamometer test bed for verification of performance. A good correlation is obtained between the test and the calculated values for the crankshaft torsional vibrations.