The torsional excitation of variable intertia effects in a reciprocating engine

The effect of piston friction on the torsional natural frequency of a reciprocating engine

“…3. Drew [1] observed a much greater frequency variation (15%) in the measured values than those predicted, with the greatest discrepancies occurring when the piston was located near mid-stroke. According to Drew the discrepancies between predicted and measured results could have been due to a number of reasons.…”

“…Experiments and predictions showed that large discrepancies occur when friction is ignored; especially at low crank rotational speed. The study used the same engine as Drew [1]. Referring to Fig.…”

“…(1) will be published shortly. The well-known equation for the inertia function without friction [1] is given by Eq. (2).…”

“…Excitation at these side peaks can feed energy into the main natural frequency and cause, what in the industry is known as, 'secondary resonance'. Drew et al [1] investigated the torsional excitation of variable inertia effects in a single cylinder reciprocating engine. They used both frequency and time domain models and presented what appeared to be the first experimental verification of the theory.…”

“…A receptance model [3] was used to predict the natural frequency function. Further details regarding set-up and physical data pertaining to the rig can be found in [1].…”