Jump to content
Sign in to follow this  
fleebut

Aldehydes

Recommended Posts

As we know E85 fuel has better or less problem tail pipe emissions as compared to unleaded fuel. All emissions except for aldehydes.

 

E85 fuel produces a high amount of aldehydes, even higher than gasoline, when burned. Aldehydes form ozone, and ozone can cause very severe respiratory problems if it stays at a breathable level. Aldehydes concentration increases in winter months.

 

This pollution easily detected as the sweet smell when first starting car. Aldehydes not directly the problem. For example red wines contain some of this chemical and give the wine it’s distinctive character. Problem occurs when ozone created from the air borne pollutant. Must be a reaction with sunlight and aldehydes? Ozone not healthy to breathe.

 

The problem only upon startup and cold engine operation which easily produces unburned fuel vapors. Ethanol burns better at higher temperatures and suffers with low temperature engine startup. Only a fraction of fuel explodes to full burn when the engine in this condition.  The 15% gasoline does burn under this cold condition and is burdened to keep engine running for the short startup/warm up period. This is not good condition to prevent aldehyde formation.

 

So, E85 masks a weakness of ethanol when utilized as substitute fuel in conventional ICE technology. Even the flex fuel cars suffer this condition. One trick for smooth cold engine operation is to simply squirt more fuel and hope a higher percentage actually burns. 

 

May the internal combustion technology improve for ethanol if focusing on E100 engines? You know instead of focusing on unleaded fuel with ability to burn E85. The consuming public actually refers to E85 as E85 gasoline like it’s merely another grade.

 

There was a post on proponents of E100 fuel and their good arguments/reasons on why this fuel is superior. Current E85 and low blends are a good product to mix with petrol, but to propel ethanol to maximum value best to develop an E100 engine. Focus on ethanol technology directly. Solve problems and exploit strengths of this fuel. Keep petrol in a separate supply stream. Ethanol will shine brightest on its own. With current engine technology we must excuse the shortcomings of ethanol with mixtures of petrol. Not a good place to be when selling ethanol.  Current situation leaves low producer cost hydrous ethanol out of possibility. This may be a mistake.

 

Share this post


Link to post
Share on other sites

People running waste vegetable oil in their diesel cars and pickups use a two tank system--one for diesel and one for the heated vegetable oil. They start and finish on diesel. Some are elaborate enough to switch automatically while others manually make the switch when the engine is up to operating temperature and the WVO is hot. Seems hydrous ethanol E100 would work good in the same situation---start on gasoline and switch to ethanol when warmed up.

Share this post


Link to post
Share on other sites

If you recall we had a few discussions regarding heated fuel injectors which Delphi was testing and heating the fuel rail. Either of these solutions would help- as would also high compression dedicated engines, heated intake air, or a costly specialized cat converter.

Share this post


Link to post
Share on other sites

Maybe DI would help as the fuel directed into hot high compression zone (TDC) like a diesel. This momentary extremely hot zone a perfect spot to squirt ethanol even if the heat quickly squashes per cold piston and cylinders. Sure a spark plug needed still but utilize the heat of compression to ethanols advantage.

 

Increased compression would enhance the effect. Also, GM HCCI technology for practical purposes would be much more stable with ethanol as ethanol is a constant reliable fuel with predictable properties.  This HCCI ignition is more efficient than the diesel compression ignition, but only available with fully warm engine under constant load. Like highway cruising.

 

My guess if the engine was committed wholly to only ethanol fuel, the efficiency, power, and startup problems would be improved.  Ethanol would show at its best and compete on level playing field. 

Share this post


Link to post
Share on other sites

flee, I think you are really over-simplifying a pretty complex problem.  I don't have time to go into everything, but consider:

 

1. E85 and gas emit aldehydes at different rates.  Down to about freezing, the rate is roughly the same.  Only below freezing does the aldehyde production of E85 start to become more significant.

 

2. Aldehydes aren't the only component involved with ozone production.  Really, it's the whole class of volatile organic compounds VOC's.

 

3. Even VOC's don't act alone.  Nitrous oxides and sunlight (as well as several other factors) are also involved in the mix.

 

4.  The relation of VOCs and NOx  isn't linear with respect to production of ozone.  In some instances, lowering VOCs has almost no effect on lowering ozone.  In other instances, lowering NOx actually raises ozone concentration.  Google 'ozone weekend effect' and see how sometimes ozone rises when there are fewer cars on the road.

 

Consider the graph:

WFigure1.2(O3isopl).jpg

http://www-personal.umich.edu/~sillman/ozone.htm

 

You can see in certain instances of low NOx emissions, lowering VOCs by an order of magnitude hardly effects ozone at all.  In other instances of moderate VOC, lowering NOx actually raises ozone.  One thing is for sure, all the talk of hot combustion, high compression, etc sounds like a recipe for high NOx.

Share this post


Link to post
Share on other sites

Interesting the Nox chemically reacts with VOC’s on some level to cut down Ozone. You’re right on being complex, of course. EPA concerned of VOC’s emissions at every level, same with NOx. So, guess, o.k. oversimplifying for now.

 

The emission rap against ethanol is minor and very minor when comparing overall emissions of unleaded, but nonetheless often spewed and therefore a good zone to improve upon. Cold startup the primary production period and cold weather precipitates longer warm-ups. Ethanol as used in conventional unleaded fueled engine technology is handicapped even if the vehicle flex fuel.  As Outlaw mentioned simple technology that could be developed or utilized to minimize problem. My thought offered to discussion was…..auto companies not zoning in on maximizing ethanol benefits. Nor are they interested in improving the technology as this takes time and money. Auto companies merely interested in mining flex credits and satisfying good vehicle operation characteristics and reliability. These are of paramount importance to customer. Being able to utilize two fuels attractive. They can test out this new fuel to determine value and in a pinch or fuel shortage a good thing to have a backup fuel source. Unfortunately, the customer is reviewing ethanol as compared to unleaded fuel within an engine optimized primarily for unleaded. Little do they know the true potential of ethanol for all the obvious reasons we post here.

 

So, a good direction for ethanol fuel?  An E100 engine designed developed etc. to operate without petrol. Pull out the safety net. A safety net that currently allows ethanol to cohabitate under petrol engines at penalty cost to ethanol.

 

This endeavor would harden off technology to push the curve to ethanol direction, currently not much pushed.  Not to discount ethanol's attractiveness as a blend agent with petrol, just an avenue to focus upon ethanol as stand alone fuel.

 

Note: Will the natural gas alternative fuel competition optimize engine technology to burn 100% natural gas? You bet they will. 

Share this post


Link to post
Share on other sites

The main product of combustion that gets all the criticism is acetaldehyde.  This VOC/HAPs like all VOC's is the product of incomplete combustion.  Two ways to improve this emission is to put back in the ethanol sensor.  Significant amount of overfueling occurs during cold start in order that the driver has a quick start up.  The value of direct injection is that injection during the compression stroke can also reduce the amount of overfueling and multiple SAE papers have shown catalysis temp and activation occurring equal to optimized gasoline cold start.

 

I still find it interesting that though ethanol has one key emission that gets all the attention, ethanol reduces 85 gasoline VOC's to near zero by E75.  Ethanol in one study shown 10 identifiable VOC's

 

By the way, Acetaldehyde is listed as a HAP yet if you like a beer or glass of wine, your body produces Acetaldehyde and if you have fruit on your kitchen counter or grill hamburgers, you expose yourself to this compound.

Share this post


Link to post
Share on other sites

If the nose is indeed an indicator of aldehyde presence on cold start- I would agree with your conclusion that the FCS is valuable to reducing aldehydes. From the S10 in my driveway, I can never remember smelling the sweet alcohol odor on start up while the Taurus or Impala will do so. Of course besides the FCS present on the '01 S10- it is only a 4 cyl 2.2 L vs the 6 cyl 3.0 or 3.5 L of the two cars with the virtual system. Even so- this odor on the latter two lasts less than 5-15 seconds on a typical cool morning.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×