View imageYou know, soot and stuff like that. The sort of thing that is an issue at and around airports. It hasn't been quite as thoroughly researched during a period when the focus has been on less visible and more damaging things like NOX and CO2. But it's a problem - and for airport planners and their regulators, local air quality is becoming a very big deal - just ask everyone concerned with the Heathrow expansion debate.
Anyway, you can now arm yourself with the finest stats available in the field courtesy of the US Transportation Research Board's Airport Cooperative Research Program. They've just published the results of a heavyweight study of the phenonemon using several real aircraft with engines covering about 70% of the US fleet. Landmark stuff.
Here's a flavour of it, but there's much, much more...
The following conclusions were drawn when emissions were sampled at the
exhaust nozzle:- The measured PM parameters for each engine type (i.e., JT8D, CFM56, CF6, RB211, etc.)
are unique. For example, in the case of the RB211, JT8D, and PW4158, the mass-based
emission indices measured as a function of fuel flow ranged from 0.04 to 0.70,
<0.01 to 0.32,and
<0.01 to 0.18 g/kg-fuel respectively.- The measured PM parameters for engine subtypes are also unique. For example, for the
CFM56-3B versus -7B engines, the ratio of their mass-based emission indices at takeoff was
found to be 4:1 (-3B:-7B).
- Credible inventories based on nozzle emission rates will require engine-specific data like
that measured in these studies.
- Black carbon PM (i.e., non-volatile particles) constitutes more than 80% of the mass of PM
emissions at all thrust conditions. At takeoff thrusts, more than 95% of the total PM mass
is black carbon PM.
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