# US 2021/0277839 A1 · Water injection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0277839 A1 - Document ID: US20210277839A1 - Status: Published application - Kind: A1 - Application number: 17/189,663 - Filed: 2021-03-02 - Published: 2021-09-09 - Earliest claimed: 2020-03-04 - Assignees: ROLLS-ROYCE plc - Applicants: ROLLS-ROYCE plc - Inventors: Christopher P. MADDEN; Peter SWANN - Web page: https://patentgrep.com/patent/US20210277839A1 ## CPC - F02C 7/228: Dividing fuel between various burners - F02C 9/28: Regulating systems responsive to plant or ambient parameters, e.g. temperature, pressure, rotor speed (F02C9/30 - F02C9/38, F02C9/44 take precedence) - F02C 3/30: Adding water, steam or other fluids {for influencing combustion, e.g. to obtain cleaner exhaust gases (F02C7/141, F02C7/30, F01D21/00, F01K21/04, F23D11/10 take precedence)} - F23R 3/346: {for staged combustion} - F02C 9/263: {by means of fuel metering valves} - F02C 9/40: specially adapted to the use of a special fuel or a plurality of fuels - F05D 2270/08: to produce clean exhaust gases - F05D 2270/081: with as little smoke as possible - F05D 2270/331: Mechanical loads - F05D 2270/804: Optical devices - Y02T 50/60: Efficient propulsion technologies, e.g. for aircraft - F02C: GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS (construction of turbines F01D; jet-propulsion plants F02K; construction of compressors or fans F04; generating combustion products of high pressure or high velocity F23R; using gas turbines in compression refrigeration plants F25B11/00) - F23R: GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS (fluidised bed combustion apparatus specially adapted for operation at superatmospheric pressures F23C10/16) - F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A gas turbine engine for an aircraft. The gas turbine comprises a combustor, a fuel injection system connected with a source of fuel and configured to inject fuel into the combustor, a water injection system connected with a source of water and which is configured to inject water into the combustor, and a control system. The control system is configured to identify an atmospheric condition; determine a water-fuel ratio for injection into the combustor of the gas turbine engine in response to the atmospheric condition; and control injection of fuel and water by the fuel injection system and the water injection system according to said water-fuel ratio to control an soot emissions caused by combustion of fuel therein. ## Claims ### Claim 1 A method comprising operating an aircraft gas turbine engine, the method comprising: providing a source of fuel and a source of water; identifying an atmospheric condition; determining a water-fuel ratio for injection into a combustor of the gas turbine engine in response to the atmospheric condition; injecting water and fuel according to said water-fuel ratio into the combustor to control soot emissions caused by combustion of fuel therein. ### Claim 2 (depends on 1) The method of claim 1, in which the determined water-fuel ratio reduces soot emissions compared to a dry mode of operation. ### Claim 3 (depends on 1) The method of claim 1, in which the atmospheric condition is an atmospheric condition causative of a condensation trail, optionally a persistent condensation trail. ### Claim 4 (depends on 1) The method of claim 1, in which the water-fuel ratio is determined on the basis of the time-integrated effect of a persistent condensation contrail over its lifespan given a current atmospheric condition and a predicted future atmospheric condition. ### Claim 5 (depends on 1) The method of claim 1, further comprising detecting the atmospheric condition using a direct measurement device. ### Claim 6 (depends on 1) The method of claim 1, further comprising inferring the atmospheric condition. ### Claim 7 (depends on 1) The method of claim 1, in which the water is injected upstream of a primary zone of the combustor. ### Claim 8 (depends on 7) The method of claim 7, in which the fuel is injected by one or more fuel injectors, each one of which has an associated water injector configured to co-inject water with fuel. ### Claim 9 (depends on 1) The method of claim 1, wherein the determining step comprises: identifying a condition to the effect that an optical depth of a condensation trail produced by the engine should be reduced; evaluating a water-fuel ratio that varies soot production to reduce ice particle formation. ### Claim 10 (depends on 1) The method of claim 1, wherein the determining step comprises: identifying a condition to the effect that an optical depth of a condensation trail produced by the engine should be increased; evaluating a water-fuel ratio that varies soot production to increase ice particle formation. ### Claim 11 A gas turbine engine for an aircraft, comprising: a combustor; a fuel injection system connected with a source of fuel and configured to inject fuel into the combustor; a water injection system connected with a source of water and which is configured to inject water into the combustor; a control system configured to: identify an atmospheric condition; determine a water-fuel ratio for injection into the combustor of the gas turbine engine in response to the atmospheric condition; and control injection of fuel and water by the fuel injection system and the water injection system according to said water-fuel ratio to control an soot emissions caused by combustion of fuel therein. ### Claim 12 (depends on 11) The gas turbine engine of claim 11, in which the control system is configured to determine a water-fuel ratio that reduces soot emissions compared to a dry mode of operation. ### Claim 13 (depends on 11) The gas turbine engine of claim 11, in which the atmospheric condition is an atmospheric condition causative of a condensation trail, optionally a persistent condensation trail. ### Claim 14 (depends on 11) The gas turbine engine of claim 11, in which control system is configured to determine the water-fuel ratio on the basis of the time-integrated effect of a persistent condensation contrail over its lifespan given a current atmospheric condition and a predicted future atmospheric condition. ### Claim 15 (depends on 11) The gas turbine engine of claim 11, further comprising a direct measurement device for detecting the atmospheric condition. ### Claim 16 (depends on 11) The gas turbine engine of claim 11, in which the atmospheric condition is inferred. ### Claim 17 (depends on 11) The gas turbine engine of claim 11, in which the water injection system comprises one or more water injectors located upstream of a primary zone of the combustor. ### Claim 18 (depends on 17) The gas turbine engine of claim 17, in which the fuel injection system comprises one or more fuel injectors, each one of which has an associated water injector configured to co-inject water with fuel injected by the fuel injector. ### Claim 19 (depends on 11) The gas turbine engine of claim 11, in which the control system is configured to determine the water-fuel ratio by: identifying a condition to the effect that an optical depth of a condensation trail produced by the engine should be reduced; evaluating a water-fuel ratio that varies soot production to reduce ice particle formation. ### Claim 20 (depends on 11) The gas turbine engine of claim 11, in which the control system is configured to determine the water-fuel ratio by: identifying a condition to the effect that an optical depth of a condensation trail produced by the engine should be increased; evaluating a water-fuel ratio that varies soot production to increase ice particle formation.