Interesting Australian Studied Diesel Article

[thefullback]

interesting article

http://www.drive.com.au/Editorial/ArticleDetail.aspx?ArticleID=40556&vf=7

any comments

[gldgti]

typical howard government and traditional australian aversion to diesels. pathetic. ask anyone in the government where we look to for good policy, and they say europe..... except for transport issues!

its true - particulates can be bad for your health (smoking kills y'all).

its true, diesels produce NOx. so do petrol cars.

lets consider something that our government DOES NOT consider:

the average diesel car uses about 60% as much fuel as its petrol counterpart in its lifetime. so even if the emissions of smoke and NOx are higher, do we ignore the fact that it uses less net fuel?

the answer is YES, if you are in government now. for the rest of us who have any SENSE, the logic is clear.

just my $0.03

[hiho]

I was at a presentation by Ray Kearny (quoted in the article) on urban pollution and he was far more critical of PM2.5 than PM10. PM10 is particulates less than 10 micron in diameter, which abound in diesel exhausts and have been considered the big bad urban health pollutant for decades. Now there is a scientific shift of the finger pointing the blame at PM2.5 (particles less than 2.5 micron in diameter), which are abundant in petrol vehicle exhaust emissions. The reason for the higher toxicity is due to the penetration into the lungs of the smaller particles, their partially oxidised composition and that they are far more mobile in the atmosphere (heavy particles will settle out, stokes law). Because you cant see them its harder to mobilise fear against them. Also, using about 10% ethanol signifigantly reduces PM2.5 emissions from petrol cars, as using larger percentages of biodiesel will do for PM10 in diesel exhaust emissions. If the australian govnmt was serious about urban pollution there would be mandated 10% ethanol in all petrol and excise exemption status for all on road use of biodiesel. Just shows what we are dealing with in this country.

[hiho]

And another thing, only a tiny percentage of diesel fuel burned in urban areas is in passenger cars. Mostly its trucks. Once again, if the government was serious about urban pollution....

[hiho]

Also, if the governments were serious about urban pollution it would have mandated ultra low sulphur diesel years ago. Sulphur acts as a nucleus for the deposition of carbon, forming the visible soot in the exhaust under rich burn conditions (under load/acceleration). Removing it is generally a good idea, however it is a handy lubricant for injector pumps. Worth noting is that Germany has used 5% bidiesel to replace sulphur as a lubricant in all diesel fuel.

I cant help but feel that this report (as well as keeping modern diesels out of Australia with archaic fuel standards) is about protecting the australian auto manufacturing industries which, as far as i know, dont make diesel engines or components. Maybe the sentiment will change when we have an Australian made diesel falcon, commodore or hatchback.

Urban pollution is as much a congestion issue. We are building urban roads and motorways at an alarming rate, and once built, all they do is congest. The same investment is not reflected in public transport. People cant use pt because either the services are not available or they are already overcrowded. If there were fewer cars on the road, road transport would become more efficient with fewer stops and starts. For diesels this means less soot producing high load conditions.

[hiho]

Bear with me here, this article says more than it first appears.

"The fuels produce roughly the same amount of hydrocarbons, toxic air pollutants and carbon monoxide but diesel produces significantly more oxides of nitrogen (NOx) and particulate matter."

So both petrol and diesel produce the same amount of hydrocarbons/toxic air pollutants in their exhaust. The hydrocarbons are partially oxidised fuel that exit the exhaust either as individual molecues or form conglomerates of molecules, aka, particles. If petrol and diesel produce the same amount (mass) of hydrocarbon emissions, then petrol must produce several orders of magnitude more ultra fine paricles of hydrocarbon, so small that they are either gasses or considered as gasses because they remain suspended in the air we breath ("So small they escape the current vehicle emission and air quality proceedures!!").

"Kearney says ultra-fine particles are dangerous because they can dissolve in the lungs. They also attract toxins, including cancer-causing chemicals, to their surface, giving them a "piggyback" ride deep into the lung tissue, where they travel beyond the lung's natural ability to expel them.

Because they are so small, they can also escape the current vehicle emission and air quality measuring procedures, which are based on weight rather than outright numbers and surface area, Kearney says.

Ultra-fine particle emissions weigh very little but have a relatively enormous surface area when compared with larger coarse particles. A billion ultra-fine particles can weigh the same as one coarse particle, yet have 1000 times the surface area."

The contradiction is glaring. Petrol and diesel produce roughly the same mass of partially oxidised hydrocarbon emissions. In diesels this manifests as large, coarse particles, in petrol, ultra fine particles (1000000000 ultrafine to 1 coarse for the same mass!). If you were to ask Kearney, he would agree. The article lies by omission.

On NOx i have to agree, Diesels produce more oxides of nitrogen due to the higher combustion pressures and temperatures.

[gldgti]

thanks hiho, you have informed us well and said what i wanted to say but dont have time to ;-) (study, urg)

[dieseldude]

So what can be done about the NOx? Would I be right in saying that I think ive seen a device of some sort that almost eliminates the NOx?

Cheers

[gldgti]

there are many methods to reduce NOx emissions, the main one is lowering cylinder maximum pressures, or in other words detuning the engine. playing with timing, ignition delay and charge timing and turbulence all affect NOx production. its hard to get a diesel to produce lots of power without producing NOx when just running it on diesel alone, but the usage of other fuels has been shown to help. it all comes back to having the engine tuned to run on a particular fuel or mixture of fuels.

form memory, LPG injection reduced NOx production because it changes the combustion reactions somewhat.

to give you a short answer, the engineers of this world are working on it.... me included.

[phaeton]

I skimmed through article.

Anyway current range with DPFs

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