Abstract
An aircraft engine incudes: a catalyst, e.g. platinum, applied to turbine blades (580c, 590c) and/or to a catalytic grid downstream of the engine's combustion chamber. An exhaust fluid additive injection system is incorporated upstream of the catalyst via a line 560, in a stator blade within the engine. The catalyst is used to reduce NOx emissions from the engine by a Selective Catalytic Reduction reaction.
Claims
1. A gas turbine engine for an aircraft, the gas turbine engine comprising: a cold pre-combustion section; a hot post-combustion section; a catalyst in the hot post-combustion section and configured to convert nitrogen oxides into diatomic nitrogen and water in presence of an exhaust fluid additive; and an outlet configured to inject exhaust fluid additive upstream of the catalyst.
2. The gas turbine engine for an aircraft according to claim 1, further comprising turbine blades in the hot post-combustion section, and wherein at least one of the turbine blades includes the catalyst.
3. The gas turbine engine for an aircraft according to claim 1, further comprising a plurality of rotating turbine blades in the hot post-combustion section, and wherein at least one of the rotating turbine blades includes the catalyst.
4. The gas turbine engine according to claim 1, wherein the catalyst is platinum.
5. The gas turbine engine according to claim 1, further comprising a core thrust region and a bypass section surrounding the core thrust region, wherein at least 90% by mass of the catalyst is in the core thrust region.
6. The gas turbine engine according to claim 1, further comprising a grid downstream of the hot post-combustion section, wherein the grid comprises at least part of the catalyst.
7. The gas turbine engine according to claim 1, further comprising a plurality of outlets configured to inject the exhaust fluid additive upstream of the catalyst, wherein the outlets are each associated with a turbine blade of the gas turbine engine.
8. The gas turbine engine according to claim 7, wherein each of the turbine blades forms part of the post combustion turbine.
9. The gas turbine engine according to claim 7, wherein each of the turbine blades forms part of a high-pressure turbine section in the hot post-combustion section.
10. The gas turbine engine according to claim 7, wherein each turbine blade associated with such an outlet is in the form of a stator.
11. The gas turbine engine according to claim 1, further comprising a tank system configured to supply the exhaust fluid additive to the outlet.
12. An aircraft comprising the gas turbine engine according to claim 1.
13. A method of reducing nitric oxides (NOx) emissions from an aircraft jet engine, the method comprising: combusting jet fuel in a combustion chamber of the aircraft jet engine wherein combustion gases generated by the combustion include NOx gases, and reacting the NOx gases with an exhaust fluid additive in presence of a catalyst, wherein the catalyst forms at least part of a surface of the jet engine downstream of an outlet into the jet engine for the exhaust fluid additive.
14. The method of claim 13, wherein the surface of the jet engine is a surface of a turbine blade in the jet engine.
15. The method of claim 13, further comprising: passing the combustion gases through a turbine section of the aircraft jet engine; and injecting an exhaust fluid additive into the combustion gases from outlets in at least one turbine blade of the turbine section, wherein the outlets are upstream of the catalyst.
16. A method of operating an aircraft engine comprising: injecting an exhaust fluid additive into a gas turbine engine upstream of a catalyst in the gas turbine engine, and reacting the exhaust fluid additive with a combustion gas generated within the gas turbine engine in presence of the catalyst.
17. The method of claim 16, further comprising: passing the combustion gases through a turbine section of the gas turbine engine; and injecting an exhaust fluid additive into the combustion gases from outlets in at least one turbine blade of the turbine section, wherein the outlets are upstream of the catalyst.
Description
SUMMARY OF THE DRAWINGS
[0040] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:
[0041] FIGS. 1a and 1b show a prior art gas turbine engine;
[0042] FIGS. 2a and 2b show a gas turbine engine according to a first embodiment;
[0043] FIGS. 3a and 3b show a gas turbine engine according to a second embodiment;
[0044] FIGS. 4 and 5 show a gas turbine engine in accordance with the second embodiment;
[0045] FIG. 6 shows two turbine blades according to a third embodiment of the invention;
[0046] FIGS. 7, 8 and 9 show schematic diagrams of the tank system of an embodiment of the invention;
[0047] FIG. 10 is a flow diagram of a method of performing an embodiment of the invention; and
[0048] FIG. 11 is an aircraft incorporating an embodiment of the invention.
DETAILED DESCRIPTION
[0049] The present disclosure is of a gas turbine engine having a catalyst and an outlet for exhaust fluid additive arranged upstream of the catalyst within the engine. The outlet sprays exhaust fluid additive so that it can be contacted on the catalyst and a selective catalytic reduction reaction can occur. The (preferably aqueous) solution sprayed from the outlet comprises anhydrous ammonia, aqueous ammonia or a urea solution. The catalyst is platinum. The catalyst can be a platinum coating on the turbine blades of the post-combustion section of the gas turbine engine and/or the catalyst can be applied to a grid/mesh downstream of the post-combustion turbine blades, within the nozzle of a central core region of the gas turbine engine. The jet engine is a turbofan engine with a bypass, and the catalyst and injection outlet are applied to the core region. There is also a tank for storing the exhaust fluid additive, housed within the wing or pylon, or within the casing.
[0050] FIGS. 1a and 1b show a prior art gas turbine engine (GTE), or turbofan, of the like used in passenger aircraft. The GTE shown in FIG. 1a comprises an air inlet 110 followed by a low-pressure compressor 140 and then downstream of the low-pressure compressor 140 there is a high-pressure compressor 150. Together, these are the cold section 101 of the GTE, where air is compressed by compressor blades (stator blades 130 and rotor blades 120) before it reaches a combustion chamber 160 for combustion. In the combustion chamber 160, the cold compressed air is combusted in the presence of jet fuel to produce the energy required for mechanical work to be done on high-pressure high-temperature turbine blades (rotor blades 190 and stator blades 180) immediately downstream of the combustion chamber. Downstream of the combustion chamber (post combustion) and high-temperature high-pressure turbine blades there is a high-temperature lower-pressure turbine which is also driven by the kinetic energy of the air from the combustion chamber. This is connected to a shaft running through the GTE and which drives the low-pressure compressor blades and the fan inlet. Beyond the low pressure turbine there is a nozzle 170, shaped to help the airflow of the hot air and exhaust gases exiting the high-temperature low-pressure turbine generate thrust. The engine has a casing 105 surrounding it. The post-combustion section of the engine is the hot section 102, and includes the high-temperature turbine blades of both higher and lower pressure, and the nozzle 170.
[0051] FIG. 1b shows a turbofan of the prior art, in which the fan blades 110b are sized and shaped to draw airflow around the core region (the central components) of the engine in a bypass. The fan blades 110b drive air between an outer casing 106 of the engine and an inner casing 105b. The air is combined with the exhaust gases of the engine at the nozzle to increase the amount of thrust generated, in comparison to a no-bypass arrangement. Modern turbofans typically have a bypass ratio of between 1:5 and 1:14, and usually about 1:10, which means that per 1 kg of air which travels through the combustion internals, 10 kg passes through the bypass.
[0052] A first embodiment of the invention is shown in FIGS. 2a and 2b. As can be seen in the figures, the pre-combustion cold section of the GTE is essentially the same as in the prior art. In the first embodiment there is a catalytic grid 200 located in the region of the nozzle 270. There is also a tank 250, containing exhaust fluid additive housed externally of the internals of the core of the turbofan, with a line to an injection outlet in a stator 280 of the post-combustion hot section of the GTE. In this arrangement, exhaust fluid additive is distributed throughout the exhaust gases within the turbulent exhaust gas airflow (which helps with distribution of the exhaust fluid additive) and is then contacted on the downstream catalytic grid. The catalytic grid provides a surface area of platinum on which the nitrogen oxides in the exhaust gases can be broken down into diatomic nitrogen and water in the presence of the exhaust fluid additive.
[0053] The catalytic grid structure 200 in this embodiment provides some resistance to the exhaust gases leaving the core portion of the engine, and therefore negatively affects the generation of thrust of the core portion. By applying it only to the core portion of a turbofan engine with a bypass, and not applying it to the bypass gases (air), it has been realised that the overall effect on the thrust produced is low (as a large proportion of the thrust is generated by the bypass gas, which does not flow through the catalytic grid), whilst enabling emission reduction on all of the exhaust gases of the core portion.
[0054] FIGS. 3a and 3b show a second embodiment of the invention with like reference numerals (separated by 100) denoting like components (e.g. the tank 250 is equivalent to the tank 350), wherein, as with the first embodiment, the pre-combustion cold section of the GTE is essentially the same as in a prior art GTE. The difference in comparison to the first embodiment is that there is no platinised grid downstream of the final turbine, and instead, at least one of the turbine blades (shown in this figure as rotor blades 390) comprises platinum on its external surface, on which exhaust fluid additive can be contacted. The inventors have realised that the post-combustion turbine blades (stator and/or rotor blades) can provide a surface area of platinum to react nitrogen oxides into nitrogen and water, without having a catalytic grid in the pathway of the exhaust gases. A catalytic grid in the pathway of the exhaust gases reduces the effective thrust produced by the core of the engine. With the second embodiment it is possible to realise at least some of the benefit of having a catalyst in contact with the exhaust fluid additive and the exhaust gases, without incurring the losses associated with a catalytic grid downstream of the hot turbine. In the same manner as the first embodiment, the second embodiment can be applied to only the core portion of a turbofan engine, with the bypass gases combining with the exhaust gases at the nozzle, downstream of the catalyst.
[0055] FIG. 4 shows a stator 480 for use in the present invention. The stator 480 includes an injection outlet 440 and an internally housed line 460 for exhaust fluid additive to travel through the stator to the injection outlet.
[0056] In FIG. 5, the stator 580 is one of multiple stators forming a stator ring arranged between the rotors 590 (between rotor rings) within the turbofan jet engine, within the core portion of the turbofan engine. As can be seen in FIG. 5, there are rotor 590c and stator rings 580c comprising catalyst. The rotor 590c and stator 580c rings comprise multiple rotor and stator blades. The rotor 590c and stator 580c rings comprising catalyst are arranged downstream of the exhaust fluid additive injector 520 which in this example is integrated into a stator blade 580. The injected exhaust fluid additive travels downstream and at least partially mixes with the exhaust gases before being contacted on the catalyst-bearing rotor and stator blades. The exhaust fluid additive travels from a tank (not shown) through a line 560 and is injected as a liquid but typically vaporises at the operating temperature of the engine. The black dots in FIG. 5 are indicative of the exhaust fluid additive travelling through the gas turbine engine. As the gases within the turbine expand and do work in the post-combustion section of the engine, the temperatures decrease. The catalyst coatings can therefore be arranged within the nozzle 570 to coincide with the temperature range which is optimal/required for SCR. This temperature range can be in the range from 700? C. to 1450? C., with the preferred range being between 850? C. and 1200? C. The low-temperature compression section 501 and the combustion section 503 are also shown in FIG. 5, to help to illustrate the flow direction within the figure.
[0057] FIG. 5 shows a possible implementation of the second embodiment. In this implementation, there is a stator (as shown in FIG. 4) upstream of platinum coated rotors 590c and stators 580c. An outlet within an upstream stator 580 is configured to inject exhaust fluid additive to the hot gaseous exhaust stream which leaves the combustion section 503. The exhaust fluid additive and exhaust gases at least partially mix and then contact the platinum-coated rotors 590c and/or stators 580c. Coating the rotors and stators downstream of the exhaust fluid additive injection outlet can maximise and/or optimise the surface area on which SCR can occur. Platinum is expensive, as well as being a rare metal, and it is therefore preferred to selectively coat the stators and rotors to optimise catalysis, for example by not coating the connection ends of the turbine blades. The efficiency gains in doing so might be such that it is optimal (from a cost/efficiency perspective) to apply a platinum coating to up to 100% of the visible surfaces of the low-pressure post-combustion turbine. In FIG. 5 the post-combustion turbine blades are shown as sequential rotors and stators, which is the standard arrangement in a turbofan jet engine. Downstream of the combustion chamber there may first be an exhaust fluid additive outlet, followed by an area of platinum catalyst.
[0058] FIG. 6 shows an embodiment wherein a high-pressure post-combustion turbine blade 615 houses (air bleed) outlets 610 for air supply to the blade, and outlets 640 for the exhaust fluid additive to enter the gaseous stream (this is shown with lines 616 to highlight the flow path of exhaust fluid additive from the turbine blade). In this embodiment the turbine blade 615 may have the air bleed outlets and/or the exhaust fluid additive outlets 640. FIG. 6 also shows a (downstream) blade 641 of the post combustion turbine coated with platinum catalyst. The platinum catalyst turbine blade is downstream of the high-pressure turbine so that the exhaust gases and the exhaust fluid additive are contacted together on the catalyst-coated blade of the turbine blades having lower pressure and temperature than the blades adjacent the combustion chamber. These rotor and stator blades can form part of a set. As can be seen in FIG. 6, the exhaust fluid additive injection can be similarly implemented to the air supply to the blade. A tank system feeds the exhaust fluid additive to the outlets within the blade. The outlets can be holes and can be multiple holes.
[0059] FIG. 7 shows an example of a tank system which can be used to supply exhaust fluid additive to the gas turbine engine. In FIG. 7 the tank 710 is housed within the structure of the wing 705. There are pumps (not shown) which drive the fluid within a line 720 (e.g. conduit, pipe) to a position within the gas turbine engine and from there to an outlet 730 within the post-combustion section of the engine.
[0060] FIG. 8 shows another example of a tank system, wherein the tank 810 is housed within a pylon 806 which joins the gas turbine engine to the wing.
[0061] FIG. 9 shows another example of a tank system, wherein the tank 910 is housed within the structure of the gas turbine engine, within the casing 907 surrounding the core region of the engine. FIG. 9 also shows the line 920
[0062] FIG. 10 shows a flow diagram of a method of reducing nitrogen oxide (NOx) emissions from an aircraft jet engine. The steps the method comprising the steps of combusting 1010 jet fuel in a combustion chamber of the jet engine to create combustion gases 1015 comprising NOx gases, and reacting 1020 the NOx gases with an exhaust fluid additive 1025 in the presence of a catalyst 1035 which forms at least part of a surface of the jet engine that is downstream of an exhaust fluid additive injection outlet. Downstream of the catalyst there is a stream 1045 comprising diatomic nitrogen, water, and unreacted exhaust gases.
[0063] FIG. 11 shows an aircraft 1100 having two gas turbine engines 1120, which in this example are turbofan jet engines in accordance with any of the embodiments described herein. The aircraft 1100 is suitable for transporting passengers and/or cargo. In the case were the aircraft is a passenger aircraft, the passenger aircraft may comprise a passenger cabin comprising a plurality of rows and columns of seat units for accommodating a multiplicity of passengers. The aircraft may have a capacity of at least 20, more preferably at least 50 passengers, and more preferably more than 50 passengers. The aircraft may be a commercial aircraft, for example a commercial passenger aircraft, for example a single aisle or twin aisle aircraft.
[0064] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.
[0065] It is possible that different embodiments can be combinedfor example the catalytic grid of the first embodiment could be used in addition to the catalyst coated turbine blades of the second embodiment. Furthermore, the turbine blades in the third embodiment could be used in conjunction with either the first and/or second embodiments.
[0066] The platinum catalyst may be coated on to rotor blades and/or stator blades downstream of the exhaust additive fluid outlet within the gas turbine engine. There may, however, be multiple outlets for exhaust fluid additive. There may be catalyst upstream and downstream of the outlets for exhaust fluid additive. The catalyst may partially or entirely cover the rotor and/or turbine blades.
[0067] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.
[0068] The term or shall be interpreted as and/or unless the context requires otherwise.
