Epicyclic Gearing for Gas Turbine Main Propulsion

The success of epicyclic gears in marine main propulsion has been well established. Their small size and weight has led to their introduction in many types of vessel. Epicyclic gears were used in many of the very early naval gas turbine powered vessels and, indeed since then, nearly 250 gears have been supplied for use with a marinized version of the “Proteus” gas turbine. The construction of this and other gas turbine propulsion gears is discussed in some detail to illustrate the basic concepts and design of the gearing. Because of the difficulties in providing astern power in a gas turbine powered ship without the use of a C.P. propeller, there has been interest in the use of a high power reversing gear. Here epicyclic gearing shows a definite advantage over the equivalent alternatives and indeed was used in the naval vessels referred to earlier. Some of the parameters relating to large reversing epicyclic gears are described and the future role of reversing gears is discussed. The description of recently delivered merchant marine triple reduction epicyclic gears is given. The gears transmit 8200 kw from an industrial type of gas turbine and are each installed in a 45,000 tons bulk carrier. Epicyclic gears have played a significant role in the development of gas turbine ship’s propulsion and their future role is discussed in relation to present and projected requirements.