GB2101224A

GB2101224A - Marine gas turbine propulsion plant

Info

Publication number: GB2101224A
Application number: GB08117401A
Authority: GB
Inventors: David Eyre Williams
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1981-06-06
Filing date: 1981-06-06
Publication date: 1983-01-12
Also published as: GB2101224B

Abstract

The plant has a gas generator (16) the gases from which drive a power turbine (20) which in turn drives a propellor (24) via a shaft (28). Some of the heat in the power turbine exhaust is recovered by passing at least some of this exhaust to a combustor (32) the gases from which drive a turbine (34) which exhausts through a cooler (40) and a compressor (36) driven by the turbine (34). The drive shaft (38) of the turbine (34) may be used to drive the shaft (28) via a combining gear box (26) or the latter may be omitted in which case a large mass of pressurized gas is produced at the compressor (36). <IMAGE>

Description

SPECIFICATION Marine gas turbine propulsion plant This invention relates to gas turbine engine propulsion plant for marine vessels, and is concerned with the recovery of some of the heat in the gases which are exhausted to atmosphere.

The invention proposes the use of an exhaust gas cycle, rather than a steam cycle, in which at least some of the exhaust gases from the gas generator of the propulsion plant pass through a re-heat combustor to an inverted gas turbine in which useful work is generated.

The inverted gas turbine comprises in flow series a turbine, a cooler, and a compressor on the same shaft as the turbine. Such an arrangement has the same efficiency as that of a conventional cycle at the same ratio of absolute temperatures before compression and expansion. The supply of hot gas at atmospheric pressure is expanded in the secondary turbine to a pressure substantially below atmospheric and is then cooled and recompressed by the secondary compressor, to atmospheric or higher pressure.

If all the exhaust gases from the gas generator pass through the re-heat combustor and the inverted gas turbine and the secondary compressor re-compresses the gases to atmospheric pressure, then the useful work will appear at the shaft of the inverted gas turbine in the form of torque. This torque can then be combined with the torque from the output shaft of the gas generator through a combining gearbox to the propeller shaft of the marine vessel.

In another arrangement, only a proportion of the exhaust gas flows through the re-heat combustor to the inverted gas turbine, the shafts of the gas turbine are not connected, and the useful work appears as a higher pressure delivery from the secondary compressor.

The re-heat combustor may comprise an arrangement similar to an aero-engine re-heat system, e.g. a duct having a set of annular gutters for flame stabilisation, with fuel injection upstream of the gutters and an igniter.

The cooler may comprise a chamber which receives the gases from the secondary turbine, a supply of sea-water which contacts the gases directly and an outlet to the secondary compressor. Such a cooler is shown and described in U.K. patent specifications nos. 1272480 and 1284335.

As there may be a degree of sea-water carry over to the secondary compressor, this compressor may be provided with water manifolds having a common drain which is pumped out by a jet pump powered by a high pressure air delivery from the compressor of the gas generator.

U.K. patent specification no. 1 272480 discloses a gas turbine marine propulsion plant in which all the exhaust from the gas generator passes to an inverted gas turbine, and the propeller of the marine vessel is driven via a gearbox from the shaft of the inverted gas turbine.

In this arrangement, there is no provision for reheating the exhaust gases from the gas generator, and the inverted gas turbine is not used to provide useful work in the ways proposed in the present application.

The present invention will now be more particularly described with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of one form of gas turbine marine propulsion plant according to the present invention, Figure 2 is a diagram of a cooler which forms part of the inverted gas turbine shown in Figure 1, Figure 3 is a schematic diagram of a further form of gas turbine marine propulsion plant and, Figure 4 shows the compressor of the inverted gas turbine shown in Figure 1.

Referring to the Figures, a gas turbine marine propulsion plant 10 includes a gas turbine 12 which comprises a compressor 14, combustion equipment 16, a compressor driving turbine 18, and a power turbine 20 having an output shaft 22.

The torque transmitted by the shaft 22 is transmitted to a propeller 24 by a combining gearbox 26 and a drive shaft 28.

The exhaust gases from the power turbine 20 pass to an inverted gas turbine 30 via a re-heat combustor 32, the inverted gas turbine comprising a secondary turbine 34 and a secondary compressor 36, both being mounted on a common shaft 38. The torque from the shaft 38 is also transmitted to the drive shaft 28 through the combining gearbox 26. A cooler 40 (Figure 2) is located in the flow line between the secondary turbine and compressor and comprises a chamber 42 containing one or more water sprays 44 which are connected to an inlet below the water line in the hull of the vessel, the water being removed by a pump 46. The chamber has an inlet for the gas to be cooled and an outlet for the cooled gas.

The re-heat combustor 32 is in the form of a reheat system used in aero-engine applications and comprises a duct in which are located a number of annular flame stabilisers and fuel injectors positioned upstream of the gutters.

In use, the exhaust gases from the power turbine 20 flow to the inverted gas turbine 30 via the re-heat combustor 32 which does not operate until a pre-determined mass flow on the working line of the secondary compressor 36 has been reached. Up to this point only waste heat is being utilised and the gas from the power turbine is expanded in the secondary turbine to a pressure substantially below atmospheric, is then cooled by direct sea water spray in the cooler 42 and is recompressed in the secondary compressor 36 back to atmospheric. The work extracted by this cycle is transmitted by the shaft 38 to the propeller shaft 28 through the combining gear box 26.

Above this point, fuel is burnt in the rye heat combustor to produce a further and large increase in power.

When the re-heat is not in use, the maximum continuous power available can be increased with a reduction in specific fuel consumption, and when the re-heat is in use, the maximum continuous power available can be increased significantly with a less than proportional increase in specific fuel consumption.

The removal of water droplets from the gases in the cooler 40 is carried out by a filter 48 and in the event of a significant carry over of water droplets to the compressor 36, the compressor can be modified as shown in Figure 4.

Figure 4 shows the compressor 36 with a number of drain manifolds 50 located adjacent the stator stages of the compressor. The manifolds drain into common drain 52 and the sea water is drawn off by suction generated by an ejector 54 which is powered by a flow of high pressure air tapped from the compressor 14 of the gas generator.

In the arrangement shown in Figure 3, the useful work in the exhaust gases is used in the inverted gas turbine to produce a large mass flow of gas at a pressure greater than atmospheric.

Only a minority of the power turbine exhaust is re heated in the combustor 32, and the inverted gas turbine operates as described above to produce a large flow of gas from the delivery of the secondary compressor 36 at a pressure greater than atmospheric.

Claims

1. A gas turbine marine power plant comprising a gas generator, a power turbine arranged to drive a load and arranged to be driven by the exhaust from the gas generator, a combustor arranged to receive at least a proportion of the exhaust from the power turbine and a supply of fuel, and an inverted gas turbine comprising in flow series a turbine, a cooler and a compressor driven by the turbine, the turbine being driven by the gases from the combustor.

2. A power plant as claimed in claim 1 in which the whole of the power turbine exhaust passes to the combustor and a gear box has inputs from the power turbine and the inverted gas turbine, and an output arranged to drive the load.

3. A power plant as claimed in claim 1 in which a proportion of the power turbine exhaust is exhausted to atmosphere, and the remaining power turbine exhaust passes to the combustor to drive the inverted gas turbine.

4. A power plant as claimed in claim 1 in which the combustor comprises a duct having a flame stabilising gutters, fuel injectors upstream of the gutters and an igniter.

5. A power plant as claimed in claim 1 in which the cooler comprises a chamber having an inlet for the gases from the turbine of the inverted gas turbine, a supply of sea water to contact directly the gases, and outlet for the cooled gases to the compressor of the inverted gas turbine.

6. A power plant as claimed in claim 1 in which the compressor of the inverted gas turbine has one or more manifolds arranged to receive water, the manifolds being connected to a common drain, the drain having a jet pump driven by a supply of air from the compressor of the gas generator.

7. A gas turbine marine vessel power plant constructed and arranged for use and operation substantially as herein described, and with reference to fig. 1 and fig. 3, each combined with either or both of figs. 2 and 4.