loading Loading please wait....
Login

If you are a registered, please log in. If not, please click here to register.

ENGINE UPDATE - EMISSIONS

A look at engine emissions- fossil fuels- contrails and noise. There has been a pervasive force active near the perimeters of the aviation industry- and if it wasn’t for the global economic recession- it would have already become the biggest issue of our time. It won’t be long before it does dominate us all- then the question that begs an answer is- “Are we ready?”So far only the airlines (mainly outside of the United States) have been forced to parry with this ...

AvBuyer   |   1st July 2009
print
Back to articles
The Greening Of Aviation
A look at engine emissions- fossil fuels- contrails and noise.


There has been a pervasive force active near the perimeters of the aviation industry- and if it wasn’t for the global economic recession- it would have already become the biggest issue of our time. It won’t be long before it does dominate us all- then the question that begs an answer is- “Are we ready?”

So far only the airlines (mainly outside of the United States) have been forced to parry with this gathering force. We in Business and General Aviation have- thus far- managed to remain aloof from this mêlée of discontent. The gathering force of which I speak is the Green Movement and its accusation that the aviation industry is a scourge- due to its alleged destruction of the so-called global atmospheric environment.

The phrases ‘Global Warming’- ‘Climate Change’- ‘Greenhouse Gasses’- ‘Carbon Dioxide Emissions’- ‘Carbon Footprint’- and ‘Nitrogen Oxides’ have all been injected into our everyday vocabulary. Yet the world’s population remains divided on the validity and the intent of these phrases. The purpose of this article is not to debate- or take sides- but to report how sectors of our industry are pretty well advanced in grappling this ‘Green’ issue in an attempt to meet the calls for action ‘head-on’ now- before the entire industry is demonized without the right of reply.

First let us lay a foundation of understanding of what the individual issues are which are being lobbied about by the Green crusade. These issues fit into four distinct categories:

1. Emissions: The production of greenhouse gasses like Carbon Dioxide- Carbon Monoxide- Nitrogen Oxides- Acids- Soot- etc.

2. Fossil Fuels: The dependency by aviation on a non-renewable energy source.

3. Contrails: The production of artificial ice-crystal clouds in the stratosphere which in turn create the formation of cirrus clouds.

4. Noise: The level of intrusive sound that an arriving or departing aircraft produces.

More on these later… First let’s now grasp who all of the main players are in this ‘Opera for the New Millennium’. At the beginning we have the Green Movement which consists of the United Nations Framework Convention on Climate Change (UNFCC) and its 1997 Kyoto Convention Protocol; Albert Gore- founder and chairman of the Alliance for Climate Protection; the World Meteorological Organization and United Nations Environment Program- Intergovernmental Panel on Climate Change; the European Union and its Carbon Trading Programs; the Australian Government’s Carbon Pollution Reduction Program; and the Global Green Network.

Next we have various scientific and regulatory groups that are studying and guiding governmental policies to tackle the four environmental issues which are attributable to aviation: the International Civil Aviation Organization (ICAO); the National Aeronautics and Space Administration (NASA); the Environmental Protection Agency (EPA); and the U.S. Air Force (USAF).

Lastly we have those that are attempting to grasp the issues early so that our industry is not blindsided- and forced into an over-reactive protocol that may put us all out of business. These important players are: Boeing and Airbus; BMW/Rolls-Royce; Pratt & Whitney Canada; General Electric; Honda; Sir Richard Branson and Virgin Airlines; New Zealand Airlines; and NetJets.

EMISSIONS
Today the sustained combustion process of a conventional Gas Turbine Aero Engine (GTAE) results in various organic compounds (chemical reactions to the surrounding ambient air mixture and the compounds in the kerosene blend that is being burnt)- Carbon (C)- Carbon Monoxide (CO)- Carbon Dioxide (CO2)- Nitrogen Oxide (NO)- Sulfur (S)- Argon (AR) and Water (H2O) to be formed and emitted into the stream of the jet exhaust.

Additionally- any un-burnt fuel (Hydro Carbons (HC)) mixed with any leaking- bearing lubricants- and failing metal coatings- also add to this cocktail mixture of pollutants that exit the GTAE into the atmosphere.

Even though the air that surrounds us contains a plethora of chemical elements- whenever a complex compound of foreign particles is introduced- an imbalance occurs with far-reaching effects. One example is the creation of Sulfuric Acid that causes great damage at the earth’s surface when ‘acid rain’ falls. It is universally agreed that all un-used man-made compounds- if they are unguarded- will eventually end up in our fresh water supply or at the bottom of our oceans.

The intense heat and pressure that is produced by a GTAE metamorphosizes the chemical compounds that come into contact with it- and since no GTAE is 100% efficient- a small part of the man-made combustion mixture is not processed. Traces of these compounds are now being found in our water supplies.

The Green Movement has singled out CO2 as the largest cause of the Global Warming phenomenon today. Unfortunately CO2 is a natural by-product of any combustion or decomposition process. It is the pre-requisite compound required for photosynthesis to occur in all plant life- and it is the main building block compound that enables life-forming and life-giving sugars and proteins to form.

Its properties are such that it allows high frequency light to transmit through its invisible form- and yet it is efficient at blocking and storing low-frequency light (infra-red) hence it is being labeled as the worst ‘Greenhouse Gas.’

It has been proven globally that aviation contributes approximately 2% of all greenhouse gas emissions. The U.S. Department of Transportation has asserted that aviation domestically contributes 10% of greenhouse gas emissions caused by all transportation in the US- and 3% of the nation’s combined greenhouse gas emission by all sectors (non-transportation).

Both ICAO and the EPA have created GTAE certification standards that govern and limit the emissions of NO- CO- unburned HC- smoke- and vented fuel that all new engine designs have to meet. However- the issue of controlling the level of CO2 production by GTAEs has not yet been addressed by any of these agencies.

Most of the major companies that manufacture GTAEs around the world have embraced these new emission limits- by developing their engines into something that are much ‘Greener’ than is currently required by mandate.

Both GE and Rolls-Royce almost stand shoulder-to-shoulder regarding their ground-breaking technologies that tackle both issues of emission and fuel efficiency. GE engineers have developed a Twin Annular – Premixing Swirler (TAPS) combustor- which provides the core to their new GEnx Jet Engine. Additionally- this new engine utilizes a fully composite (non-metallic) front fan case and fan blade set. The TAPS system burns the fuel-air mixture more efficiently than conventional GTAE- thus effectively cutting emissions and saving fuel; while the use of composites reduces weight thus improving the power-to-weight ratio (power and efficiency).

Finally- the new composite fan blades that are installed on the GEnx engine are stronger and more flexible than metal blades thus allowing the size of the blades to increase- while the number of blades are reduced resulting in the lowest noise levels ever achieved on any GE produced legacy GTAE.

The GEnx is destined for both Boeing’s 787 Dreamliner and also for the next generation Airbus A350. GE also has a joint project with Honda to produce the HF120 engine destined for the HondaJet. Again GE engineers have concentrated on the combustor section to derive environmental benefits.

This engine features a high pressure ratio design with a reverse-flow combustor. Noise figures are predicted to be 20 dB below the latest Stage-4 requirement- while its emissions will be two-thirds less than current new-engine standards.

Rolls-Royce is achieving similar gains with its monster engines destined for airline service. The real story in my opinion- though- lies with its smaller engines that are being built for the mid-size airliner and business jet markets. The current BR700 series engine which provides the power for the Gulfstream V and the Boeing 717- already delivers a 20% improved fuel efficiency over its nearest competitor.

The BR725 which will power the Gulfstream G650- will improve on all of the gains delivered by its earlier siblings. In addition to producing more available take-off thrust and an even leaner fuel burn- this engine will be 4 dB quieter than its peers- while delivering 21% fewer emissions. Most of these gains are achieved by massive aerodynamic contour improvements to all of the compressor and turbine blades. The combustion chamber has also been redesigned with resultant emission reductions.

And Pratt & Whitney Canada- the company that produces the most prolific number of GTAEs utilized by business and general aviation today- is developing its PurePower series of engines. This new series incorporates major improvements in materials- fan- compressor- and turbine design. All of the design changes are billed to deliver double-digit fuel consumption improvements- 35-50% reductions in various emission gases- while achieving lower smoke and HC emissions.

FOSSIL FUELS
Excluding vegetable and animal oils- nuclear fission- and the combustion of natural renewable materials like wood and grass- virtually all other fuels that are used by combustion engines are derived from underground deposits of fossil fuel.

Coal powered the industrial revolution of the 1760s- mainly thanks to the Scotsman- James Watt and Englishman- Matthew Boulton’s invention of the industrial steam engine. But it wasn’t until the useful application of petroleum oil as a replacement for coal along with the subsequent refinement of the early internal combustion engine- before air transportation became possible.

This occurred at around the same time as Gugliemo Marconi’s communication revolution was underway with his invention of wireless telegraphy. Up until the present day- all subsequent non-military transportation systems have been entirely powered by a non-renewable fossil fuel.

Many pundits and politicos have screamed to the world that the planet has already surpassed the critical fossil fuel milestone concept of ‘peak oil’ (the point at which maximum petroleum oil production/extraction has been reached- whereby all continued production/ extraction shall see the supply dwindle to complete exhaustion). This coupled with the environmental issues at hand- is gradually pushing both governments and industry into a new conservationist policy of increasing efficiency and/or reducing consumption of fossil fuels by existing internal technology.

There is now also what appears to be a desperate search for both a renewable form of petroleum-like fuel product- and other alternative energy sources. Ethanol distilled from cellulose rich materials like corn- sugar cane- beets- and grasses- etc. is taking up some of the slack found in a diminishing oil supply- but unfortunately this distillate does not contain sufficient calorific value to keep the industrial and transportation engines running at the same pace at which fossil fuels afford them. Scientists continue to seek out the best form of renewable ‘bio-fuel’ for the future.

Many experiments with palm oil- soybeans- algae- nuts- animal fat- and other crops have proven successful and yet none of the resulting fuels have emerged as the ‘silver bullet’ answer to the problem.

The USAF- NASA- Boeing- Rolls-Royce- GE- Sir Richard Branson- and New Zealand Airlines along with the top engineering and research universities around the world are working on this problem. The USAF in conjunction with NASA is working on a synthetic fuel (Bio-Jet) produced from coal (coal gas). The original process was developed by the Nazis during World War II- in-part because their fuel supply lines were being pounded by the Allied Forces.

So far the U.S. version of this synthetic fuel when used in GTAEs has only been successful when it is burnt in a 50/50 ratio of conventional jet fuel to Bio-Jet.

Before Sir Richard Branson- owner of Virgin Airlines amongst other enterprises- inked his order for 15 Boeing 787 Dreamliner aircraft- he made Boeing pledge in conjunction with the engine supplier General Electric- that all of the aircraft would be delivered capable of operating on his Virgin Fuels division Bio-Diesel derivatives. These are produced from various renewable sources including Algae- or the nuts from the Brazilian Babassu palm tree. Likewise- in the Southern Hemisphere Air New Zealand is working in co-operation with Rolls-Royce to encourage the production and use of an Algae-derived Bio-Jet fuel.

CONTRAILS
The formation of a contrail- behind a GTAE flying within the troposphere- is largely dependent upon the level of humidity in the air. When the air is dry- the water vapor- one of the by-products of combustion- more readily assimilates into the atmosphere without having an excess that forms into the ice-crystals that are manifested in the appearance of a contrail. On wet days- contrails abound.

The properties of a contrail- when formed in still air- shows that one contrail has a natural affinity towards another- whereby a four-contrail stream will be observed to form-up into one larger diameter contrail only within a couple of hundred feet behind its creator aircraft. If the contrail bearing air remains smooth with no mechanic disturbance- eventually the contrail will spread itself out wider to as many as 20 miles. By then the contrail has taken on most of the properties of a cirrus cloud.

This blanketing effect is what the Green Movement is mainly rallying against- viewing this man-made cloud formation as a global warming contributor which traps the surface-radiated solar energy stored from the sun- just like a greenhouse.

At present- other than the classified methods of contrail suppression perfected by the U.S. Defense Department- there is no civilian program that I know of- that is tackling this environmental issue. However- it is important- for the sake of perspective- to realize that the naturally occurring dust created by volcanic eruptions and by storms over the Sahara- Gobi- and other deserts- eventually finds its way into the troposphere and higher- and is far more damaging to the environment through its greenhouse effect- than contrails will ever be.

NOISE
If you listen only to the Federal Aviation Administration (FAA)- you could easily be lead to believe that the issue of noise has been conquered. The FAA asserts in a 2003 noise study report that: “…between 1975 and 2000- the number of people exposed to significant noise had dropped by 90%...” adding that “…industry may have done all it can with hush kits and technology; future gains may require residential soundproofing or relocation…”

For many people- the environmental noise impact caused by aircraft is still very much in the forefront of their complaints. This is mainly due to the widespread- continued operation of pre-noise-rules-legacy aircraft that have little or no high-bypass airflow design incorporated into their GTAEs. Just like the collapsing turbulent airflow that follows in the wake of a sonic wave that produces a man-made thunder clap- an untreated jet exhaust stream will smash its way into the ambient air worse than a coach-load of drunken soccer fans!

Fortunately with the development of more efficient air-mixing nacelles and enlarged fan rotors- it has been possible to create high-bypass airflow that sheaths- insulates- and ultimately slows down- and mixes the hot and turbulent exhaust air stream- which results in a smaller and quieter noise footprint.

Contrary to the FAA’s 2003 report- many of the GTAE manufacturers find that they are making radical improvements in noise reduction as a by-product from the technology that they are employing to cut down on the emissions from their engines.

IN CLOSING…
We may never see a GTAE powered aircraft match the low noise and emission levels produced by a gas-balloon- but as technology continually develops within this relatively new area of the greening of our industry- we are well on the way to achieving all of this.

During my research for material for this article- I was flabbergasted to learn the world’s second largest civil aircraft operator- NetJets- is an old hand at attempting to appease the Green Movement. In addition to the Carbon Credit and Off-Set program administered by Oxford- England based Eco-Securities (one of the originators of carbon credit trading) NetJets is employing in Europe- NetJets recently assembled an environmental advisory board in both its European and U.S. markets. The American board consists of six members who bring an impressive array of skills and knowledge to aid NetJets in its desire to become a ‘Carbon Neutral’ company sometime in the near future.

There is much more that will be written and talked about regarding this issue- and this topic is still very much in its infancy. The developments that are in the making within the field of engine efficiency and renewable fuel technology are nothing but great- both economically and environmentally.

I just hope that everyone keeps their cool when the full force of public opinion focuses its attention on our aviation industry; especially here in the U.S.

The Salem witch trials seemed necessary to everyone involved (except for the ill-fated witches- of course). But those events have long-since been proven to have been driven entirely by ignorance- corrupt politics and superstition. Let’s hope that the Green Movement doesn’t mirror these same ideals.

If you have any questions regarding this article- or would like to receive some free advice- you are welcome to contact Jeremy at JetBrokers- Inc. at +1.636.449.2833- or email: jcox@jetbrokers.com

Related Articles