GB2127491A

GB2127491A - Reversible power transmission for a marine gas turbine

Info

Publication number: GB2127491A
Application number: GB08227228A
Authority: GB
Inventors: Kenneth Reginald Kelly
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1982-09-23
Filing date: 1982-09-23
Publication date: 1984-04-11
Also published as: JPS5982532A

Abstract

In order to provide reverse thrust in a marine vessel driven by a gas turbine power plant, the power turbine guide vanes (30a) are made rotatable on a disc (40) and shaft (42), both the normal power turbine rotor shaft (36) and the shaft (42) having brakes and forming the inputs to an epicyclic gear box (60), which has a single output shaft (62). In normal operation, the shaft (42) is held static and the output shaft (62) rotates anti-clockwise to propel the vessel forwardly via a propellor. To reverse the vessel the normal rotor shaft (36) is braked, and the brake on the shaft (42) is released which will drive the shaft (62) clockwise through the gear box (60). <IMAGE>

Description

SPECIFICATION Power transmission for a marine gas turbine This invention relates to a power transmission including an arrangement for reversing the propellor thrust direction in a marine vessel powered by a gas turbine engine.

A marine gas turbine usually comprises a gas generator and a power turbine driven by the gases produced by the gas generator, the power turbine then driving the propellor shaft through a speed reducing gear box. The most common methods of reversing the direction of thrust of the propeller comprise a reversing gear in the speed reducing gear box or a variable pitch propellor.

The present invention proposes an alternative method of reversing the propellor thrust direction which avoids the need for a reversing gear or a variable pitch propellor.

The power turbine usually has a ring of static guide vanes upstream of the turbine rotor blading in order to guide the energy containing gases from the gas generator onto the rotor blading at the correct angle. The present invention enables the ring of guide vanes to be rotatable on a shaft as well as the rotor blading, braking being provided for both the guide vane and rotor blade shafts, together with a gear box having a common output shaft and able to accept an input drive from either one of the guide vane or rotor blade shafts.

Accordingly, the present invention provides a power transmission for a marine vessel gas turbine engine power plant, the power plant including a power turbine having a ring of guide vanes in front of a ring of rotor blades, the ring of guide vanes being rotatable on a guide vane shaft and the ring of rotor blades being rotatable on a rotor blade shaft, each shaft having braking means to enable one of said shafts to rotate while the other shaft is held stationary, and a gear box having a common output shaft to drive a propellor, and inputs from the guide vane and rotor blade shafts, the gear box being arranged such that when the guide vane shaft is held stationary by the respective shaft braking means, the output shaft will rotate to propel the vessel in a forward direction, and when the guide vane shaft is free to rotate and the rotor blade shaft is held stationary, the output shaft will rotate to propel the vessel in an astern direction.

In a preferred arrangement, the gear box is of the epicyclic type in which the annulus gear is attached to the rotor blade shaft, the sun wheel is attached to the guide vane shaft, and the output shaft is attached to the planet wheel carrier, and the two shafts are co-axiai with the guide vane shaft internal of the rotor blade shaft.

The present invention will now be more particularly described with reference to the accompanying drawings in which, Fig. 1 shows a conventional form of gas turbine engine power plant for a marine vessel, Fig. 2 shows a power transmission according to the present invention, of a marine vessel gas turbine engine power plant, and figs. 3 and 4 are both sections on line A-A in fig. 2, but showing the different modes of power transmission operation.

Referring to the drawings, a conventional form of marine gas turbine power plant 10 comprises an air inlet 12, a gas generator 14 which itself includes compressors 1 and 1 8 driven by turbines 20 and 22 through shafts 24 and 28 respectively, and combustion chambers 28, a power turbine 30 and an exhaust duct 32. The power turbine drives a propellor 34 through a shaft 36 and a speed reducing gear box 38. The usual ways of reversing the thrust direction of the propeller 34 are either to include a reversing gear in the gear box 38, or to provide the propellor with a variable pitch mechanism for the propellor blades.

As shown in fig., the power turbine 30 has a ring of static guide vanes 30a mounted in front of a ring of rotor blades 30b which are mounted in a disc 30c attached to the shaft 36. In fig. 2, in which similar components have been given the same references as in fig. 1 ,the guide vanes 30b are also mounted for rotation, on a disc 40 which is attached to a shaft 42. The shafts are co-axial and the shaft 36 is mounted in journal bearings 44, 46 and has a thrust bearing 48, whilst the shaft 42 has a journal bearing 50 and a further journal bearing and thrust bearing in a housing 52 which is supported by radial struts 54. The housing also contains a brake for the shaft 42 and an overspeed trip, and the shaft 36 has an overspeed trip 56 and a brake 58.

The shafts 36, 42 provide the inputs to an epicyclic gear box 60 which has a single output shaft 62 driving a propellor (not shown). The gear box has an annulus gear 64 driven by the shaft 36, a sun wheel 66 driven by the shaft 42, and planet wheels 68 mounted on a planet wheel carrier 69 which drives the output shaft.

In the normal mode of operation when the marine vessel is being propelled forwardly, the brake on the shaft 42 holds the shaft stationary and the disc 40 and guide vanes 30a are static. As shown in fig. 4, the sun wheel is stationary, and the annulus gear 64 rotates anti-clockwise, as do the planet wheels 68 and carrier 69, and the output shaft 62.

When it is required to propel the vessel astern, the direction of rotation of the shaft 62 is reversed by applying the brake 58 to the shaft 36 and releasing the brake on the shaft 42.

As shown in fig. 3, the sun wheel 66 rotates clockwise, the planet wheels rotate anti-clockwise whilst the carrier 69 rotates clockwise, and the output shaft 66 rotates clockwise, driving the propellor in the reverse thrust direction. Whilst the guide vanes will not operate efficiently as rotor blades they will produce sufficient power and the inefficiency can be tolerated for the short periods of time during which the vessel requires reverse thrust. It will be necessary to keep to a minimum the radial tip clearance of the guide vanes, so that during normal operation any losses caused by the gas flowing through the clearances are minimised.

Claims

1. A power transmission for a marine vessel gas turbine engine power plant, the power plant including a power turbine having a ring of guide vanes in front of a ring of rotor blades, the ring of guide vanes being rotatable via a guide vane shaft and the ring of rotor blades being rotatable via a rotor blade shaft, each shaft having braking means to enable one of said shafts to rotate while the other shaft is held stationary, and a gear box having a common output shaft to drive a propellor and inputs from the guide vane and rotor blade shafts, the gear box having gearing enabling the output shaft to rotate in a direction to propel the vessel forwardly when the guide vane shaft is held stationary by the respective braking means, and for the output shaft to rotate in an opposite direction to propel the vessel rearwardly when the rotor blade shaft is held stationary by the respective braking means and the guide vane shaft is allowed to rotate.

2. A power transmission as claimed in claim 1 in which the two shafts are co-axial and the gear box comprises an epicyclic gear box, the guide vane shaft being arranged to drive the sun wheel, the rotor blade shaft being arranged to drive the annulus gear and the planet wheel carrier being arranged to drive the output shaft.

3. A power transmission for a marine vessel gas turbine engine power plant constructed and arranged for use and operation, substantially as herein described, and with reference to figs. 2 and 3 of the accompanying drawings.