Turboshaft gas turbine engine and expansion ratio relationship

Patent metadata

Field	Value
Publication number	US-11486302-B2
Application number	US-202017060986-A
Country	US
Kind code	B2
Filing date	Oct 1, 2020
Priority date	Oct 23, 2019
Publication date	Nov 1, 2022
Grant date	Nov 1, 2022

Abstract

A turboshaft gas turbine engine comprises, in fluid flow series, a gas-generator compressor, a combustor, a gas-generator turbine, and a free power turbine. The expansion ratios of the turbines are dependent upon an outlet temperature of the combustor, and an expansion relationship between the turbines is defined as the ratio of expansion ratios of the turbines over a running range of non-dimensional power outputs of the gas turbine engine. A second derivative of the expansion relationship is from 0.6 to 1.0.

First claim

The invention claimed is:

1. A turboshaft gas turbine engine comprising:
a gas-generator compressor, the gas-generator compressor being an axial-centrifugal compressor having
at least one axial compression stage,
a final centrifugal compression stage downstream of the at least one axial compression stage, and
a design point pressure ratio in a range from 12 to 16, the design point pressure ratio being a pressure ratio of the gas-generator compressor when the turboshaft gas turbine engine is operating at a maximum rated power at International Standard Atmosphere sea level static conditions;

a combustor;
a gas-generator turbine having a design point expansion ratio in a range from 4.5 to 5.5, the design point expansion ratio being an expansion ratio of the gas-generator turbine when the turboshaft gas turbine engine is operating at the maximum rated power at the International Standard Atmosphere sea level static conditions; and
a free power turbine, wherein
the gas-generator compressor, the combustor, the gas-generator turbine, and the free power turbine are in fluid flow series, and
an expansion relationship between the turbines is defined as the ratio of the expansion ratio of the free power turbine to the expansion ratio of the gas-generator turbine (R FPT :R GG ) over a running range of power outputs of the gas turbine engine.

2. The gas turbine engine of claim 1 , wherein:
the gas-generator turbine is a single-stage turbine; and
the free power turbine is a two-stage turbine.

3. The gas turbine engine of claim 2 , in which the gas-generator turbine comprises a stator having from 14 to 30 nozzle guide vanes.

4. The gas turbine engine of claim 2 , in which the gas-generator turbine comprises a rotor having from 30 to 60 turbine blades.

5. The gas turbine engine of claim 2 , in which a ratio of the number of nozzle guide vanes in a stator to the number of turbine blades in a rotor is from 0.23 to 1.

6. The gas turbine of claim 1 , in which the gas-generator turbine and the free power turbine are arranged to contra-rotate.

Assignees

• Rolls Royce Plc
• Rolls Royce Deutschland Ltd & Co Kg

Inventors

• Stieger Rory D
• Taylor Mark D
• Janke Erik

Classifications

• F02C7/32

  Arrangement, mounting, or driving, of auxiliaries · CPC title

• F05D2240/35

  Combustors or associated equipment · CPC title

• F02C3/10 Primary

  with another turbine driving an output shaft but not driving the compressor · CPC title

• F02C7/36

  Power transmission arrangements between the different shafts of the gas turbine plant, or between the gas-turbine plant and the power user ({F02C3/107 - F02C3/13 and} F02C7/32 take precedence; couplings for transmitting rotation F16D; gearing in general F16H) · CPC title

• F02C3/103 Primary

  the compressor being of the centrifugal type · CPC title