1. AA241B: Aircraft Emissions
Good afternoon
My name is Nicolas Antoine and today I’m going to be talking about the research I am working on with Professor Kroo, namely optimizing aircraft and operations for minimum noise.
Nicolas Antoine
Stanford University

2. Introduction
Commercial aircraft generate 13% of CO2 emissions by transportation sources.
Aircraft engine emissions, just like noise, are regulated by the FAA.
Only “local emissions” (around airports) are regulated.
Low-emissions combustion is key area in engine design.
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…

3. Jet Fuel Combustion CnHm + S + N2 + O2 → CO2 + H2O + N2 + O2
+ NOx + CO + SOx + Soot + UHC
Products of
ideal combustion
Fuel
Air
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…
Products of
non-ideal combustion
NOx: Affects ozone (O3) concentration
CO2: Absorbs outgoing infrared radiation
CO: Toxic
Soot: Visible

4. Emissions Regulations
Only Soot, UHC, CO, and NOx are regulated.
The ICAO/FAA regulations are based on a simulated landing-takeoff (LTO) cycle:
Takeoff 0.7 minutes 100% Thrust
Climb %
Approach %
Taxi/Idle %
Emissions = EI (g emissions/kg fuel) * Fuel Flow (kg/s)* Time in Mode (s)
Note: EI is the Emissions Index
Maximum allowable values depend on thrust, overall pressure ratio (OPR)
See ICAO Environmental Protection Annex 16
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…

5. Cruise Emissions
No regulations yet, but expected in the near future (legal aspects of international airspace are difficult to resolve).
Subsonic aircraft operate in the tropopause, a particularly vulnerable region of the atmosphere.
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…

6. Contrails Formed as water from engine exhaust freezes.
Contrails promote cirrus formation
May hamper atmosphere heating/cooling schedule
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…

7. Reducing Emissions Enormous progress since the 1960s
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…
Convair 880 “Old Smokey” – 1960
Boeing 777 – 1995
But continuous growth and increasing public awareness mean this is not enough…

8. Reducing Emissions
International push to reduce emissions above and beyond current regulations (e.g. Kyoto Agreement).
Cannot demand reductions without understanding:
The reduction mechanisms.
The interrelationships between various emissions.
The impact on aircraft design.
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…

9. Reducing Emissions
Detail design of the combustor is the most obvious method of decreasing emissions (by reducing the Emissions Index)
For NOx, reducing residency time is beneficial.
Various new combustors are under development featuring thermodynamic and chemical methods of reducing emissions.
May not be sufficient. What can be done at the aircraft and overall engine level?
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…

10. Reducing Contrails
Decrease cruise altitude (to increase ambient temperature)
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…
A: 35,000 ft
B: Jet Exhaust

11. Reducing Contrails
Decrease cruise altitude (to increase ambient temperature)
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly… C
A: 35,000 ft
B: Jet Exhaust
C: 25,000 ft

12. Reducing Fuel-Related Emissions
Increasing combustion temperature and pressure promotes more complete combustion, resulting in reduced fuel flow.
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…

13. Reducing NOx Emissions
Temperature and pressure are catalysts in the dissociation of N2 and O2 and the formation of NOx
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…
Generally, changing operating conditions or combustor configuration
to reduce NOx emissions increases fuel consumption and related emissions

14. Optimized Designs Minimum Cost Minimum Fuel Minimum NOx
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…
Cruise Altitude: 32, , ,000
Cruise Mach:
Diverging Requirements - Competing Objectives

15. Trading Emissions TRADE: 30% NOx Reduction for 6% Fuel Increase
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…

16. What about noise?
Recall Tuesday presentation: increasing BPR is beneficial
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…
INCREASE NOx PRODUCTION
INCREASE FUEL CONSUMPTION

17. “Green” Airplane: a compromise
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…
Airbus

18. Conclusions Emissions are only regulated during takeoff and landing.
But increasing concern will mandate cruise regulations in the near future.
Conflicting requirements depending on emissions to be reduced (NOx vs. Fuel Consumption vs. Noise).
While trend towards larger turbofans has improved fuel efficiency and decreased noise, it is a challenge to reduce NOx emissions.
Open problem!
The commercial aircraft of the future might well be:
“Slower, Lower, Greener”
- Motivation: increasingly severe noise restrictions placed on airlines, a consequence of growing world air fleet and an increasing number of people living near airports.
- Number of noise-related airport restrictions doubled in 30 years.
- In fact, noise has become such a serious issue that it has practically made the construction of new airports impossible, further aggravating the situation.
New noise certification requirements to be introduced in 2006
Individual countries and airports adopting their own, even stricter policies, most notably at London Heathrow.
- Restrictions are having an effect on the design of new aircraft before they even fly…