Water injection
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.
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, the atmospheric condition being an atmospheric condition causative of a condensation trail;
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 the fuel therein.
2. The method of claim 1 , in which the determined water-fuel ratio reduces the soot emissions compared to a dry mode of operation.
3. The method of claim 1 , in which the water-fuel ratio is determined on the basis of a time-integrated effect of a persistent condensation trail over the lifespan of the persistent condensation trail given a current atmospheric condition and a predicted future atmospheric condition.
4. The method of claim 1 , further comprising detecting the atmospheric condition using a direct measurement device.
5. The method of claim 1 , further comprising inferring the atmospheric condition.
6. The method of claim 1 , in which the water is injected upstream of a primary zone of the combustor.
7. The method of claim 6 , in which the fuel is injected by one or more fuel injectors, each one of the one or more fuel injectors has an associated water injector configured to co-inject the water with the fuel.
8. The method of claim 1 , wherein the determining step comprises:
identifying the atmospheric condition to the effect that reducing an optical depth of the condensation trail would reduce a net warming impact of the condensation trail;
evaluating the water-fuel ratio that varies soot production to reduce ice particle formation.
9. The method of claim 1 , wherein the determining step comprises:
identifying the atmospheric condition to the effect that increasing an optical depth of the condensation trail would reduce a net warming impact of the condensation trail;
evaluating the water-fuel ratio that varies soot production to increase ice particle formation.
10. 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, the atmospheric condition being an atmospheric condition causative of a condensation trail; 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 the fuel and the water by the fuel injection system and the water injection system according to said water-fuel ratio to control soot emissions caused by combustion of the fuel therein.
11. The gas turbine engine of claim 10 , in which the control system is configured to determine the water-fuel ratio that reduces the soot emissions compared to a dry mode of operation.
12. The gas turbine engine of claim 10 , in which the control system is configured to determine the water-fuel ratio on the basis of a time-integrated effect of a persistent condensation trail over the lifespan of the persistent condensation trail given a current atmospheric condition and a predicted future atmospheric condition.
13. The gas turbine engine of claim 10 , further comprising a direct measurement device for detecting the atmospheric condition.
14. The gas turbine engine of claim 10 , in which the atmospheric condition is inferred.
15. The gas turbine engine of claim 10 , in which the water injection system comprises one or more water injectors located upstream of a primary zone of the combustor.
16. The gas turbine engine of claim 15 , 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 the water with the fuel injected by the fuel injector.
17. The gas turbine engine of claim 10 , in which the control system is configured to determine the water-fuel ratio by:
identifying the atmospheric condition to the effect that reducing an optical depth of the condensation trail would reduce a net warming impact of the condensation trail;
evaluating the water-fuel ratio that varies soot production to reduce ice particle formation.
18. The gas turbine engine of claim 10 , in which the control system is configured to determine the water-fuel ratio by:
identifying the atmospheric condition to the effect that increasing an optical depth of the condensation trail would reduce a net warming impact of the condensation trail;
evaluating the water-fuel ratio that varies soot production to increase ice particle formation.