Engineering Abstracts 1949

Engineering Abstracts from 1949

Volume XII, No. 5, June 1949

Crankshaft Damping

The author attempts to give a correct physical explanation of natural damping by torsional vibrations, and also to obtain approximate formulae for pre-calculation of the damping in any given case. The paper describes experimental work with a single-cylinder engine driven by external power, and excited to torsional vibrations by a spring- loaded cam disk. In this way the damping from the moving parts could be investigated separately, and it was found that the damping was almost entirely due to hysteresis in the crankshaft, and oil damp­ ing, due to lateral shaft movements in the main and crankpin bearings, which was directly proportional to the bearing clearance. The paper also gives a simple and practical method for the calculation of damped vibrations in arbitrary elastic systems, and the calculation of hysteresis and bearing damping in a single-cylinder engine. Formulas are given for the total damping in multi-cylinder engines, with or without heavy flywheels, and the results are compared with the measured damping in a number of oil engines in service.—Paper P. Draminsky, read

In this paper the subject of "engine wear” has been limited to

Volume XVII, No. 6, June 1954

Large Nine-cylinder Diesel Engine

A nine-cylinder engine designed to develop 11,200 b.h.p. at 115 r.p.m. under normal conditions at sea has recendy been completed by Burmeister and Wain. It has cylinders 740 mm. in diameter with a piston stroke of 1,600 mm., and is to be installed in a tanker under construction at the Nakskov Skibsvaerft for A.P. Moller, Copenhagen. It is the highest-powered marine engine constructed by Burmeister and Wain.

The new engine is equipped with three turbochargers of the Brown-Boveri VTR-630 type, these blowers being similar to those employed in the main engines of A. P. Moller’s M.S. Dorthe Maersk and the Songkhla, Samoa and Sibonga of the East Asiatic Co. The output of the 11,200 b.h.p. engine is slightly higher than that of a corresponding 12-cylinder non-turbo-charged unit, which is about 10 feet 10 inches longer and 35 per cent heavier than the nine-cylinder turbo-charged engine. Ten nine-cylinder engines of this type are being built by Burmeister and Wain and one with 10 cylinders, for a cargo ship, at Eriksbergs Mek. Verk. developing 12,500 b.h.p. In Japan an engine has been installed in the recently completed Hanmasan Maru, a cargo ship of 10,200 tons with a service speed of 17} knots. The fuel consumption of these engines, based upon the results of similar but smaller units installed in ships now in service is expected to be 0 3341b. per b.h.p. hr., the mechanical efficiency being about 88 per cent. In normal service the mean indicated pressure is approximately 1021b. per sq. in.— The Motor Ship, March 1954; Vol. 34, p. 518.