My Yaris hybrid emits cleaner air than it inhales in terms of PM

From a crude back of the envelope calculation ...

A 1.5 liter engine, spinning at 1500 RPM, will consume or 'filter' about 0.7 cubic meter of air per kilometer. Not accounting for adjustments for Atkinization and throttling and below-ambient manifold pressure, all of which will reduce the filtered air volume. Placed in a rectangular kilometer-long box, its cross section would be a 26 mm square, barely over an inch wide. That isn't very much air. The car body itself will shove aside around 2500 cubic meters per kilometer.

Attaching a 20x20" MERV13 furnace filter on the roof, facing forward, will filter several hundred times more air than that engine.

 

Global commercial air fleet has ~10,000 aircraft aloft at any time, most moving though ~10 km atmosphere in cruising phase. this is also the highest level where atmospheric particle concentrations are high (Li et al. 2022, https://doi.org/10.1038/s43017-022-00296-7).

This global fleet inhales 24 thousand tons of ambient air and its particles per second. A large fraction I don't know goes to 'bypass' and emitted unchanged. A small fraction enters combustion, and particles emitted are not known to me. This is cruise phase.

In startup, Jet A/kerosene is burned sloppy. You have been there and smelled the volatiles. Particulate emission fluxes in this and takeoff phase are not known to me.

In landing phase, tires smoke (emit particles) and they can't not because they go from 0 to 150 promptly and under heavy loading. Particulate emission fluxes here are not known to me either.

If one could put all these unknowns together, one could know if commercial air fleet is particle emission plus or minus and by how much.

 

I just had to look up some figures:

Britannica description:
"... one finds engines with a broad spectrum of bypass ratios, including medium-bypass engines (with bypass ratios from 2 to 4), high-bypass engines (with bypass ratios from 5 to 8), and ultrahigh-bypass engines, so-called UBEs (with bypass ratios from 9 to 15 or higher). A whole generation of low- and medium-bypass engines has completely supplanted the first generation of aircraft powered by (zero-bypass) turbojet engines. ..."

Wikipedia list of particular engines:
Bypass ratio - Wikipedia

 

wondering WHY commercial airlines can't implement carbon fiber shrouds over tops of landing gear wheels - directing some 200 knots of air flowing over the tops of wheels forcing flow downward, coupled with downward flow on the bottom of the wheels - bringing wheels up to speed prior to landing & save a lot of tire replacement - not even counting all the particulate that'd be mitigated

 

Anything that could get the wheels spinning at speed would add even more drag than the gear down for the engines to counter.

Then I suspect the tire smoke is more from the sudden load onto the tires than the unbraked wheels starting to spin.

Plus there is a practical reason along the lines of why the Tesla Semi doesn't have wheel skirts. These things impede inspection of the tires and wheels.