GB2531629A

GB2531629A - A device to suppress contrail formation

Info

Publication number: GB2531629A
Application number: GB1513782.1A
Authority: GB
Inventors: Latif Qureshi Masood
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-08-04
Filing date: 2015-08-04
Publication date: 2016-04-27
Anticipated expiration: 2035-08-04
Also published as: GB201513782D0; GB2531629B

Abstract

A mechanical device C, with no moving parts, that can be externally attached to the exhaust port of a combustion engine, specifically an aircraft gas turbine engine, to suppress contrail formation. The combusted gases are inputted into the device and deflected by stator vanes A1, A2, A3, which causes the gases to rotate in order to centrifugally separate moisture from the gases. A central shaft S of the device may be coaxial with a low-pressure shaft of the engine. Water in the gases may condense on soot particles, the soot particles acting as nucleation centres for further precipitation. A surface P of the device may be coated with a condensation inducing metal, e.g. silver. The device may comprise a centrifuge vessel V, with cooling fins A4 on an outer surface thereof. Water condensed from the gases may be collected in a drain D, and subsequently drained out of the device.

Description

Descriptions

Introduction and background to the invention

[0001]. This invention aims to reduce the environmental impact of contrails that are formed in the atmosphere due to aircraft exhaust gas emissions. Contrails is a word coined from condensation trails. The combustion products of any hydrocarbon fuel are carbon dioxide and water. When H2O and CO2 are created in the combustor, they are in the gaseous form. When the exhaust exits into the cold atmosphere at altitudes, the H2O component cools and condenses to form vapour particles. In the case of flying aircraft, the atmospheric conditions at certain temperature, pressure and altitude could become favourable to further the condensation of moisture. At some distance behind the aircraft, the vapour trail then condenses sufficiently to become visible to the naked eye (Figure 1). This is the condensation trail. Natural breeze then disperses this contrail to form cirrus clouds. The cirrus clouds reflect heat back to Earth and, thus, contribute to global warming. Considering the ever increasing number of aircraft flying, the magnitude of these cirrus clouds is having an adverse effect on the atmosphere, especially above high density airports. The cirrus clouds reflect heat back to the Earth, thus contributing to global warming. The scope of this invention is to reduce contrail formation.

[0002]. Contrail suppression is a field that has had a renewed interest due to environmental awareness. The prior art shows attempts to suppress contrails using one of the three approaches, namely: a) Chemical Additives b) Electromagnetic radiation c) Heat exchangers None of the patents claimed so far, nor the available literature employs the concept of the centrifugal effect to rotate the exhaust gases in order to selectively cool and separate the moisture out of the exhaust gases.

[0003]. In this device C, (Figure 2) the exhaust gases from engine E are thrust into a static turbine T. The turbine blades are used to deflect the linear energy of the exhaust gases to travel in a helical path. A helix has a circular component and a linear component. The circular component creates the centrifugal effect, wherein the heavier particles are thrown outwards to traverse a larger radius, and the other lighter particles are squeezed inwards to traverse a smaller radius. The outer periphery of the exhaust gases in the centrifugal device contains moisture, and under the pressure generated by the centrifugal effect, condenses into water. This water is then drained out and can be further processed for disposal.

Description of Drawings:

[0004]. The present invention will be described by the accompanying drawings to illustrate the different aspects of design and workings.

Figure 1: Shows the moisture in the exhaust cools at a distance behind the engines to form contrails.

Figure 2: Shows the invention of the centrifugal device C fitted to a high bypass turbine engine E. A feature of this invention is that no modification of any existing engine needs to be done, and the device is an external attachment C. Figure 3: Description of a cut away drawing of a, state of the art, high bypass 3-shaft turbine aero-engine.

Figure 4: Description of a block diagram of a, state of the art, high bypass 3-shaft turbine engine also shown in figure 3 above, with intercooler IC, recuperator REC, combustion chamber CC and Nozzle N. The shafts HPS, IPS and LPS are coaxial.

Figure 5: Description of the phase diagram of water. Region of interest is for the water state to move from the critical point C to the liquid phase in order to reach a design point within this region. (www.chemguide.co.uk) Figure 6: The invention: Block diagram of the working of the device and the heat dissipation only from ILO to the cold airflow Fl.

Figure 7: The invention: Conceptual example of the path of a volume of flow F2 input to the device, its linear energy deflected into flow F3, the energy causing further deflection into rotational flow F5, its split into circular flows F6 and F8. The flow F6 condenses into a moisture laden flow F7 collecting into a rotating water ring and is drained out, while the residual rotational flow F8 is straightened out to exit as linear flow F9 with some residual thrust.

Figure 8: The invention: A simplified example of a cut-away drawing of the device, showing the apertures of the vessel, the location of the aero-foils, and the air-flows, as claimed.

Description of a turbine engine:

[0005]. Illustrations in Figure 3 and Figure 4 describes the workings of a turbofan or a turboshaft engine: A simple turbofan engine comprises of a fan enclosed in a nacelle, this splits into a main bypass flow and a small part of the flow is fed into a Low Pressure Compressor LPC, an intermediate Pressure Compressor IPC, a High Pressure Compressor HPC, a combustor or Combustion Chamber CC, a High Pressure Turbine IIPT, an Intermediate Pressure Turbine IPT and a Low Pressure Turbine LPT. The exhaust F2 exits through a nozzle N. [0006]. Such turbine engines 10005] are also called three shaft engines. The LP compressor is driven by the LP turbine through the LP shaft (LPS). The IP compressor is driven by the IP turbine through the IP shaft (IPS), and the HP compressor is driven by the HP turbine through the HP shaft (TIPS) The bypass fan (shown as FAN in Fig 4) is geared to the LPS. All three shafts are co-axial.

[0007]. Some turbine engines are two shaft engines, with one less compressor, shaft and turbine. That is, the IPC, IPT and IPT shaft are not included. This invention can be attached to both the two shaft and three shaft turbine engines.

0006], [0008]. Some turbine engines, in addition to the above [ also can possibly insert an intercooler IC between the LP compressor and the HP compressor. This is in order to cool the compressed gas so as to allow further compression. The location of IC is shown in the flowchart in Figure 4.

[0009]. In addition to]0008] above, some engines can also possibly insert a recuperator (shown as REC) in Figure 4 between the HPC compressor and the combustor CC. This is done in order to preheat the compressed gas before the gas is combusted. The source of this heat is usually from the LP turbine's exhaust F2.

Description of Combustion Chemistry:

[0010]. In the description of combustion chemistry, the role of nitrogen is simplified here. Nitrogen enters the engine cold, and leaves the engine at the exhaust temperature. The percentage that forms NOx is negligible, though its corrosive effects are considerable. However, in the aspects of this invention, the chemical reactions shown are for the combustible reactants only.

[0011]. Combustion: the hydrocarbon fuel reacts with oxygen in the following stoichiometric ratio if complete combustion takes place as shown: C.H2n+2 + ((3 n+ 1)/2)(02±4N2) = nCO2 + (n+ 1)H20 + 2(3 n+ 1)N2 (Equation 1) This basic equation is only descriptive and not exhaustive, and does not include all the contaminants, nor does it include the larger molecules of fuel.

Now specifically for kerosene, where n=12, we have: Ci2H26 + 18.5(02+4N2) -12CO2 + 13H20 + 74N2 (Equation 2) As seen in Equation 2 above, for every Ci2H26 molecule burnt, there are 13 molecules of H2O produced. That is, the molar ratio of kerosene to water is 1:13.

Volume of Kerosene = Molar Mass of Kerosene / Density of Kerosene Volume of Water (13 as in Eq.2), Volume Ratio = (12*12 + 26)/ 0.82 = 207 cm3 = Molar Mass of Water/Density of Water = 13*(2+16) / 1 = 234 cm3 = Volume of Kerosene: Volume of Water (Equation 3) = 207: 234 = 1: 1.13 [0012]. The Equation 3 approximation shows that the volume of water in the kerosene engine's exhaust relates 1.13 times the volume of fuel carried by the aircraft. That is, the engine produces more water than the kerosene it burns.

[0013]. In some turbine engines, some water is injected into the combustor in order to lower the flame temperature in order to prevent the formation of NOx. This injected water also adds to the water content of the exhaust.

[0014]. Thus the water at exhaust consists of combustion by-product [0012J and the water injected in the combustor F00131 This water exists in the exhaust in the form of vapour at high temperature and pressure.

[0015]. The present invention intends to trap the water in the exhaust as in "141.

Description of the Centrifugal Effect:

[0016]. The centrifugal effect works on the basic principle of the dynamics of fluids. When mixtures of two fluids of dissimilar densities, contained in a vessel, are rotated on a common axis, the fluids tend to be thrown outwards due to the centrifugal force. Of the two fluids, the denser fluid is thrown outwards the farthest. As a consequence, a void is created in the centre, and the rarer fluid is thus squeezed centre-wards to fill the void. The lighter fluid and heavier fluid can then be extracted separately.

[0017]. However, in the aspect of this invention, we are interested in the extraction of the denser fluid. The denser fluid is supposed to be water in the mixture of H2O, CO2 and N2.

[0018]. It should be appreciated that when both H2O, CO2 and N2 are in the gaseous state, the heavier CO2 would spin at the farthest radius, hence, in order to prevent this, a certain amount of pre-cooling is required to convert H2O from the gaseous state to the nucleation state before introduction into the centrifugal vessel. This pre-cooling would make the water vapour denser than the carbon dioxide gas.

[0019]. According to the phase diagram of CO2 and N2, from available literature, it can be inferred that CO2 and N2 will continue to exist in the gaseous state at an exhaust temperature of 400 ° C and a pressure of 0.5 atm. Once the water has been removed, the Density of CO2 at the exhaust temperature and Pressure can be calculated according to the equation below: P = pRT (Equation 4) Where, for CO2: P CO2 = mole fraction of CO2 x exhaust pressure = 0.121 x 50000 Pa R = Universal gas constant = exhaust temperature P cot = 0.121 x 50000 / 673 x 287 Similarly, for N2 PN2 = mole fraction of N2 x exhaust pressure R = Universal gas constant = exhaust temperature PN2 = 0.747 x 50000 / 673 x 287 = 287J / kgK = 673 °K = 0.031 kg/m3 = 0.747 x 50000 Pa = 287J / kgK = 673 °K = 0.1934 kg/m3 [0020]. At the given temperature and pressure CO2 and N2 exist beyond their critical points and will always exist in the gaseous form irrespective of the change in temperature and pressure within the operating range of the invention device.

[0021] Water on the other hand lies below its critical point and can therefore condense into liquid water due a decrease in temperature or due to an increase in pressure. This is illustrated in the Phase diagram of water in Figure 5.

Description of Water Physics:

[0022]. The exhaust mixture of H2O and CO2 follows the Dalton's Law of partial pressure. The partial pressure exerted by water is proportional to the number of moles of water in the mixture of the exhaust gases.

This can be worked out from Equation 2 where the reaction products are: 12CO2 + 13H20 +74N2 Molar ratio of Water = 13 / (12+13+74) = 0.131 Molar ratio of CO2 = 12 / (12+13+74) = 0.121 Molar ratio of N2 = 74 / (12+13+74) = 0.747

Description of Contrails

[0023]. If the pressure of the exhaust mixture of H2O, CO2 and N2 is greater than the saturated vapour pressure at that temperature, then the water condenses into liquid water. The particle size of the condensate is determined by the Kelvin equation.

In (P/Po) = 27V in Ir RT (Equation 5) where: P = actual vapour pressure Po = saturated vapour pressure = surface tension of water Vin = molar volume = radius of droplet = gas constant = temperature.

[0024]. The H2O molecule in the gaseous state is of atomic size, however, as the molecules coagulate to achieve a minimum size of the order of 0.02 microns, then these particles can behave as condensation nuclei. Further coagulations until the particles achieve a minimum size of the order of 20 microns, then these particles behave as water vapour and further coagulations to about 1000 microns and larger, the particles are proper raindrops.

Claims

Claims I A mechanical device C with no moving parts that can be externally attached to the exhaust port of a combustion engine E wherein the combusted gases F2 are input into the said device, the thrust energy of the said gases deflected by stator turbines to rotate the said gases in order to centrifugally separate moisture from the combusted gases F2 so as to selectively dissipate thermal energy from the moisture alone thus condense the said moisture, allowing the other combustion products to exit the device without thermal dissipation.
2. The Device as claimed in claim 1 wherein the shaft S of the centrifuge mechanism is coaxial with the Low Pressure Shaft of the said engine E, operates when the said engine is also operating, by the engine E forcing the exhaust gases F2 into the said device.
3. The Device as claimed in claim 1 wherein the stator turbine aero-foils Al deflects the combusted gases air-flow F2 into air-flow F3.
4. The Device as claimed in claim I and claim 3 wherein the stator turbine aero-foils A2 further deflects the combusted gases air-flow F3 into radial air-flow F5.
5. The Device as claimed in claim I wherein the circular air-flow F5 splits into a dense moisture laden, air-flow F6 rotating circumferentially and the rarer moisture free airflow F8, rotating closer to the centre of the rotational axis.
6. The Device as claimed in claim 1 and claim 5 wherein the temperature and pressure of a small percentage of the molecular H2O in air-flow F6 initially drops to a liquid phase, condenses on to the soot particles, the soot particles acting as nucleation centers for further precipitation.
7 The Device as claimed in claim I wherein the surface P is coated with a condensation inducing metal, one example being silver coating.
8. The Device as claimed in claim 1 and claim 6 wherein the outer surface of the centrifuge vessel V with external cooling air fins A4, is subject to the cold bypass-airflow Fl from the engine E, thus cooling the airflow F6.
9. The Device as claimed in claim 1 and claim 8 wherein the bypass airflow Fl is utilized, without let or hindrance, to absorb some thermal energy from the airfoils A4 externally of the vessel V without disturbing the airflow Fl.
10. The Device as claimed in claim 1 and claim 7 wherein the H2O component in air-flow F6 portion in contact with the inner periphery P of the vessel V is cooled sufficiently to condense into additional water droplets.
11. The Device as claimed in claim I, claim 7 and claim 8 wherein the centrifugal force further forces the airflow F6 against the cold inner surface P of the vessel V, further condenses H2O to a liquid state F7.
12. The Device as claimed in claim 1 and claim 11 wherein the liquid flow F7 collects in the drain D, and is subsequently drained out.
13. The Device as claimed in claim 1 and claim 12 wherein the residual heat in the drained out flow F7 is partially recovered by the requirements of thermal energy, possibly by the utilities in the aircraft cabin, the leading edges, the engine, before the water F7 is disposed off 14. The Device as claimed in claim 1 wherein the diameter of the centrifuge vessel V is enlarged to enhance the centrifugal effect created by the stator turbine T, finally converging back into the exit nozzle N creating back-pressure.Device as claimed in claim 1, and claim 12 wherein after the flow F7 in condensed form of H2O is extracted, the residual airflow F8 mainly contains the un-cooled gases CO2 and N2.16. The device as claimed in claim 1 and in claim 12 wherein the stator aero-foils A3 straighten the radial flow F8 to exit the centrifuge C through nozzle N as linear airflow F9.17. The Device as claimed in claim 1 and claim 15 wherein the linear airflow F9 contains the residual gases consisting mainly of CO2 and N2 are released, un-cooled, into the atmosphere.18. Device as claimed in claim 1 and all the above claims wherein the air-flow F9 released into the atmosphere does not contain sufficient moisture to create contrails.Claims 1. A mechanical device C with no moving parts that can be externally attached to the exhaust port of any aircraft gas turbine engine E operating at an exceptionally high temperature, wherein the combusted gases F2 are input into the said device, containing a vessel V, the thrust energy of the said gases deflected by stator vanes to rotate the said gases in order to centrifugally separate moisture from the combusted gases F2, the cold bypass airflow Fl absorbing some of the heat, so as to selectively dissipate thermal energy from the moisture alone, thus, condense the said moisture on the vessel V's inner surface P, the resulting water collected in drain D, finally allowing the other combustion products to exit the device without thermal dissipation.2. The Device as claimed in claim 1 wherein the shaft S of the centrifuge mechanism may be coaxial with the Low Pressure Shaft of the said engine E, operates when the said engine is also operating, by the engine E forcing the exhaust gases F2 into the vessel V of the said device.(r) 3. The Device as claimed in claim 1 wherein the stator turbine aero-foils Al deflects the combusted gases linear air-flow F2 into helical air-flow F3.4. The Device as claimed in claim 1 and claim 3 wherein the stator turbine aero-foils A2 further deflects the combusted gases helical air-flow F3 into radial air-flow F5.CO5. The Device as claimed in claim 1 wherein the radial au-flow F5 splits into a dense, moisture laden, circular air-flow F6 rotating circumferentially and the rarer moisture free air-flow F8, rotating closer to the centre of the rotational axis.6. The Device as claimed in claim I and claim 5 wherein the temperature and pressure of a small percentage of the molecular H2O in air-flow F6 initially drops to a liquid phase, condenses on to the soot particles, the soot particles acting as nucleation centers for further precipitation.7. The Device as claimed in claim 1 wherein the inner circumference surface P of vessel V, can be coated with any condensation inducing metal.8. The Device as claimed in claim 1 and claim 6 wherein the outer surface of the centrifuge vessel V with external cooling air fins A4, is subject to the cold bypass-airflow Fl from the engine E, thus cooling the airflow F6.9. The Device as claimed in claim 1 and claim 8 wherein the bypass airflow Fl is utilized, without let or hindrance, to absorb some thermal energy from the airfoils A4 externally of the vessel V without disturbing the bypass airflow Fl.10. The Device as claimed in claim 1 and claim 7 wherein the H2O component in air-flow F6 portion in contact with the inner periphery P of the vessel V is cooled sufficiently to condense into additional water droplets.11. The Device as claimed in claim 1, claim 7 and claim 8 wherein the centrifugal force further forces the airflow F6 against the cold inner surface P of the vessel V, further condenses H2O to a liquid state F7.12. The Device as claimed in claim 1 and claim 11 wherein the circular liquid flow F7 collects in the drain D, and is subsequently drained out.13. The Device as claimed in claim I and claim 12 wherein the residual heat in the drained out flow F7 is partially recovered by the requirements of thermal energy, possibly by the utilities in the aircraft cabin, the leading edges, the engine, before the water F7 is disposed of.
14. The Device as claimed in claim 1 wherein the diameter of the centrifuge vessel V is enlarged to enhance the centrifugal effect created by the stator turbine T, finally converging CO hack into the exit nozzle N creating back-pressure.
15. Device as claimed in claim 1, and claim 12 wherein after the flow F7 in condensed form of H2O is extracted, the residual airflow F8 mainly contains the un-cooled gases CO2 and 1\1,.
16. The device as claimed in claim 1 and in claim 12 wherein the stator aero-foils A3 straighten the radial flow F8 to exit the centrifuge device C through nozzle N as linear air-flow F9.
17. The Device as claimed in claim 1 and claim 15 wherein the linear thrust airflow F9 contains the residual gases consisting mainly of CO2 and N., are released, un-cooled, into the atmosphere.
18. Device as claimed in claim 1 and all the above claims wherein the air-flow F9 released into the atmosphere does not contain sufficient moisture to create contrails.