GB2497778A

GB2497778A - Reducing aero-engine emissions within an airport

Info

Publication number: GB2497778A
Application number: GB1121999.5A
Authority: GB
Inventors: Uyioghosa Leonard Igie; Pericles Pilidis; Paul Lambart; Riti Singh
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-12-21
Filing date: 2011-12-21
Publication date: 2013-06-26
Also published as: GB201121999D0

Abstract

A method of reducing aero-engine emissions within an airport, during taxiing, take-off and landing, by water or liquid injection 5 in to the engine intake 8, emanating from the nozzles 6 embedded in the runway 7. As the aircraft approaches, motion sensors 3 sends signals to the control unit 4, which decides the nozzles 6 to be activated.

Description

I

A Method of Reducing Aero-Engine Emissions within an Airport during Taxiing, Take-off and Landing

Background

Aero-engines produce emissions resulting from fossil fuel combustion which is a concern to airport operators, airliners and original equipment manufacturers. Over the years there has been an effort from all stake holders in the aircraft industry to reduce emissions, particularly NOx which is linked to high temperature oxidation of diatomic nitrogen, emitted as an exhaust gas during combustion. An investigation by Zurich airport suggest that 80% of NOx emitted around the vicinity of an airport is attributed to air traffic. However, the study indicates that this finding should not be considered as a metric to quantify actual impacts.

The gas turbine engine industry has seen a very significant advancement in the combustion technology over the past 5oyears, now providing more tuel efficient engines. This advancement has been met with an increase in air flights mainly due to more affordable low-cost airlines in developed countries and an increasing consumer population in the developing world. With legislations from governments aimed at reducing environmental footprint in general, some airport operators are now introducing emission-based landing fees that are specific to the engines fitted to an aircraft. This scheme is largely used to reduce government pressure on emissions and improve public perception, generate revenue and to genuinely improve the environmental quality for passengers and the neighbourhood.

Water injection into the compressor from previous practices has proven to increase the density of the engine core flow, thereby improving mass flow and thrust. This reduces the specific fuel consumption that extends the creep life of the turbine blades due a reduced turbine inlet temperature and consequently lower exhaust gas emissions. The reduction in fuel burn is particularly important during take-off, when the demand for fuel and combustion temperature peaks. This method also provides an opportunity for compressor blade washing that generally optimises the performance of the engine, ensuring that the engine operates closer to its optimal condition. Some studies including NASAICR-2004-212957 suggest that water misting through injection could reduce the noise level in the low pressure compressor by 0.61db. This is mainly attributed to the increased core mass flow that reduces the jet velocity required to sustain the same level of thrust.

There are two known methods of reducing NOx emissions from aero-engines. Joint studies by NASA and Boeing (NASA/CR-2004-212957, SAE Paper 2004-01-3108) indicates water misting at the low and high pressure compressor and a method of injecting water directly into the combustion chamber. These studies show that for the first method, 50% reduction of NOx is achieved during take-off, while for the latter up to 65% NOx reduction could be obtained. Despite better NOx reduction for the combustion method, water misting into the compressor was found to favourably improve the compressor efficiency as well as reduce the specific fuel consumption.

This is mainly due to mass flow and density improvement, using more water in the compressor core.

With these promising performance benefits, the major drawback of both techniques is the additional weight of the injection system that increases the payload for aircraft carriers. This also includes a reduced fuel efficiency improvement when water injection is applied, due to a heavier aircraft. The weight of the injection system for a 747-200 aircraft is estimated as 163.3kg fiom the referred studies. Additional weight of water for the compressor injection method is stated as 1136.2kg while for the combustion injection system 511.2kg is indicated. The invention revealed here introduces a method that completely eliminates the concern about additional weight as well as the problems that may arise with installations on an aircraft.

Statement of Invention

The object of this invention is a method of reducing aero-engine emissions, particularly NOx, thereby providing a cleaner and more environmentally friendly airport. This is implemented by the injection of water or liquid droplets (containing chemical additives that reduce the freezing point of water) inside the aero-engine intake during taxiing for take-off and landing. The invention embodies the installation of a liquid injection system in an airport runway or tarmac, which: 1. eradicates the need to install an additional system on the airframe, that consequently adds weight to the aircraft, increases fuel consumption and therefore diminishes the NOx emission reduction.

2. reduces the financial cost of reducing emissions since the new wash system serves multiple aircraft, as opposed to installing the wash system in every aircraft engine.

3. eliminates the complexity involved in the distribution of fluid within an airframe, which can be associated with inadequate supply of fluid at the right amount of pressure. This includes the eradication of leakages in pipe fitting and valve related problems that can easily cause delays in flight schedules.

4. fits into the existing aircraft and airport infrastructure. This includes different aero-engine design, size (including combat/tactical aircraft) and configuration for longer and shorter runways.

5. ensures a more reliable and easily maintained injection system, as the parts are more easily accessible and the servicing is independent of the aircraft operation.

Drawings The method and system installation for injecting liquid into the engine while taxiing is depicted in the figures attached: 1. Front view of an aircraft on a runway! taxiing while liquid is injected from ground nozzle into the primary core intake of the engine.

2. Side view illustrating an aircraft engine ingestion of injected liquid.

Figure 1 illustrates the front view of an approaching aircraft, in which the engine 1 hangs on the wing 2. As the aircraft approaches, the electronic motion sensor 3 detects this, sending signals to the main control 4 to activate liquid injection 5. The main control 4 consists of the electronic control unit that determines the nozzles 6 in a particular location along the runway 7 that is to be activated. Along the row in a particular location, one or more neighbouring nozzles 6 are switched on during activation. This is decided by a wind sensor coupled with the motion sensor 3 that sends signals to the main control 4 to reduce the pump pressure due to increasing wind speed. In doing so, more fluid 5 is injected towards the engine intake 8 ensuring that the liquid injection 5 is not drifted away by the wind. The function of the main control 4 is also to decide the start and stop of all activated nozzles 6 at the right and left of the fuselage 9. However the other un-activated neighbouring nozzles spray injection 10 would be turned on when an aircraft of a different size or number of engines approaches. The whole process of activating the nozzles 6 at subsequent upstream location and then the deactivation of the nozzles 6 after approach is continued until the aircraft takes off or halts at the terminal. The liquid underground pipe network 12 connected to all the nozzles 6 is also depicted. This network is channelled to the main supply pump installed with the main control 4. Similarly the sensor connections are underground, for which signals are sent through sensor cables 13 to the main control 4.

Figure 2 depicts the side view of an aircraft ingesting the injected liquid 5. The nozzles 6 implanted on the runway 7 are installed in a way that it does not protrude the runway to avoid having any destructive effect on the tyres 11 of the aircraft. The nozzles 6 alignment with the runway 7 surface is to be flat with a blunt finishing.

Claims

<claim-text>Claims 1. A method of injecting water or liquids towards the intake of an aero-engine, for which the liquid source emanates from the runway or tarmac of an airport or an air base, for the purpose of reducing emissions, improving thrust and compressor washing as the primary or secondary objective.</claim-text> <claim-text>2. A method according to claim 1, in which nozzles are embedded in the runway, placed at different locations along the runway, for which every location consists of one or more neighbouring nozzles.</claim-text> <claim-text>3. An injection system according to the preceding claims that is installed beneath an airport runway, for which water, its demineralised form mixed with anti-freeze liquid when required, is pressurised through a pipe network connection to form a spray of droplets at the exiting nozzle tips.</claim-text> <claim-text>4. An injection system according to claim 3, that forms a spray of liquid, whose droplet sizes ranges between 10 and 25Omicrons, spray angle ranges between 00 and 1000, with water-to-air intake mass flow ratio between 0.002 and 0.032 5. An injection system according to preceding claims, in which the functional nozzle during injection is determined by a control and sensing unit that also determines when to activate and stop injection.6. An injection system according to preceding claims, which is sensitive to change in ambient condition and wind direction, reducing pump injection pressure in hotter temperature or windy conditions.</claim-text>