Torsional effects of using heavy fuels in diesel power systems

The use of torsional vibration calculations for verification of a power transmission system is well known. In the United States of America certain analysis are used by people associated with diesel engine systems. Since the cost of fuel has drastically changed in the past five years, diesel engine manufacturers as well as operators of the equipment have been concentrating on reducing operating costs by reducing rotating weight, higher horsepower output per cylinder and using lower grade fuels. These changes have resulted in changing the method of approaching the torsional calculation from the view of a perfect system, uniform output per cylinder, to the condition where one cylinder has no fuel injected into the chamber (mis-fire) but the cylinder still compresses the gas. The results of these calculations and their effects on coupling selection are discussed and compared with field measurements.