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 nantoine@stanford.edu

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…

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

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 2.2 85% Approach 4.0 30% Taxi/Idle 26.0 7% 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…

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…

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…

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…

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…

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…

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: Ambient @ 35,000 ft B: Jet Exhaust

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: Ambient @ 35,000 ft B: Jet Exhaust C: Ambient @ 25,000 ft

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…

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

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 31,000 26,000 Cruise Mach: 0.82 0.75 0.65 Diverging Requirements - Competing Objectives

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…

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

“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

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…