OXIDATION CATALYST AFTERTREATMENT

[Awesome!]

http://www.locophotos.com/PhotoDetails.php?PhotoID=93730

Does anyone have heard of this aftertreatment? Does it gives more HP?

[WSOR 3801]

It is for emissions compliance.  Similar to a catalytic converter on an automobile.  It might take power away.  There could be a lot more of these systems installed, especially in California.

[edbenton]

Heaven help the RR's if the CARB people mandate those on the locomotives.  They mandated those on trucks for 2008 models and OTR trucks lost 1 MPG and also saw their maintance costs almost DOUBLE.  That and when they regenarate they throw more smoke than an ALCO.

[Awesome!]

It is for emissions compliance.  Similar to a catalytic converter on an automobile.  It might take power away.  There could be a lot more of these systems installed, especially in California.

Do you know how much horsepower is affected?

[rvos1979]

If I heard the news correctly, most, if not all, the truck engine makers will be using Selective Catalytic Reduction to meet the new emissions regs for 2010, citing fuel economy, EGR is burning too much fuel for everyones tastes, and many engine makers are having problems with the particulate filters not regenerating when they're supposed to, the SCR should clean everything up.

It's not that the horsepower is affected, as the throttle response suffers, I don't like waiting 30 seconds after mashing the pedal on the highway to feel the power come on.......

[Awesome!]

Good point!!!!!!

[ndbprr]

I've often wondered why the railroads crossing the rockies didn't consider oxygen injection into the air stream for the climb up. If they increased the oxygen to sea level it would increase HP and speed considerably as anyone who has driven a car over a mountain pass can attest.  It would only take a small tank on the engine and a filling station before asecending.   

[fredswain]

That's really all that a turbo does. Aside from any specific boost pressure, all it is doing is increasing the amount of air in an engine. Diesel engines run with an excess of air anyways so more isn't necessarily going to help them. There is a time and place where it can though. Typically a turbo diesel engine can have it's boost pressure raised and hence the amount of air entering it yet power won't really be affected. However increasing fuel will supply ill increase power to the point where it finally needs more air. A downside to too much fuel (or too little air) in a diesel is increased smoke levels. This was also true in steam engines when they spewed black smoke at times, such as working hard, as they couldn't get enough air into the firebox to completely burn off everything cleanly.

A catalyst or even a muffler does not need to be restrictive to do their jobs properly. Whether or not what actually gets used is restrictive or not is another matter though. If they just increased air into a diesel engine it could help clean up emissions somewhat but it's not going to be a power benefit. More power from the generator really isn't an issue if you can't put it to the ground anyways but that's another subject. You need to remember that a car is driven by an internal combustion engine that is directly coupled to the wheels through a transmission and drivetrain. A locomotive is not. It's internal combustion engine spins a generator and an electric motor uses this power to move the train.

You do run into other emissions issues with running too much air into the engine as opposed to fuel. Just as running too rich is dirty, running too lean can also be dirty. There are just different things that get burned off effectively. If you have too much air, your exhaust will end up being too cold to effectively burn off some harmful emissions. A catalyst needs to hit a certain temperature to work properly and some in fact do need extra air injected into them to complete conversion. A diesel already has the disadvantage of having a relatively cool exhaust in relation to gasoline engines which leads to certain emissions issues.

Catalyst aftertreatment doesn't HAVE to be a bad thing. What it WILL be remains to be seen.

[ndbprr]

Not really the same thing. A turbo does boost the air amount but if the air is thinner at altitude it starts from a lower atmospheric presure than 14.7#/ inch squared.  With the use of oxygen the emission levels are reduced and the need for the turbo is reduced.  The primary forms of emissions are sulfur dioxide from the sulfur in the fuel and NOx from the nitrogen in the air.  Sulfur has been addressed by federal regulation and lowering in diesel fuel. NOx comes from the nitrogen in the air. By increasing the oxygen content it reduces the amount of nitrogen which is normally 79% of air by volume. If the oxygen were increased to say 40% of the volume the nitrogen would be reduced to 60% resulting in less NOx per cubic foot of stack gas. Currently I am involved with the use of 100% oxygen to replace air in combustion processes. This has the advantage of reducing the stack gas to 20% of the normal volume and consists of CO2 and water with some SOx from the fuel in the sulfur.  Partial pressurization strips the water and washs out the SOx in the form of very dilute sulfuric acid leaving only CO2 which can then be captured and sequestered or used in process streams requiring CO2.  No reason why this would not work on diesel engines also.  The big factor as always with the railroads is, "We've never done that before".  It would boost he power available considerably over using straight pressureized air.

[JonathanS]

Not really the same thing. A turbo does boost the air amount but if the air is thinner at altitude it starts from a lower atmospheric presure than 14.7#/ inch squared.  With the use of oxygen the emission levels are reduced and the need for the turbo is reduced.  The primary forms of emissions are sulfur dioxide from the sulfur in the fuel and NOx from the nitrogen in the air.  Sulfur has been addressed by federal regulation and lowering in diesel fuel. NOx comes from the nitrogen in the air. By increasing the oxygen content it reduces the amount of nitrogen which is normally 79% of air by volume. If the oxygen were increased to say 40% of the volume the nitrogen would be reduced to 60% resulting in less NOx per cubic foot of stack gas. Currently I am involved with the use of 100% oxygen to replace air in combustion processes. This has the advantage of reducing the stack gas to 20% of the normal volume and consists of CO2 and water with some SOx from the fuel in the sulfur.  Partial pressurization strips the water and washs out the SOx in the form of very dilute sulfuric acid leaving only CO2 which can then be captured and sequestered or used in process streams requiring CO2.  No reason why this would not work on diesel engines also.  The big factor as always with the railroads is, "We've never done that before".  It would boost he power available considerably over using straight pressureized air.

At 40% Oxygen you might end up with more NOx rather than less.  Since the fuel would burn hotter and the NOx reaction is endothermic kinetics would push the mix to a higher nitrogen oxides levels.  A high oxygen level in the combustion gas would introduce other problems.  Some of the current gasketing material would need to be replaced with something more inert.  The steel capped aluminum pistons might need to be replaced by all steel pistons.  And any blow by of the 40% oxygen gas into the crankcase will cause a fire if you are lucky or an explosion if you are not. 

I agree with you in principle that oxygen enrichment has the potential to reduce total emissions and perhaps increase efficiency.  However it will not be a simple change, and it introduces other problems and dangers.

[CSSHEGEWISCH]

I'm not an engineer so please excuse me if I appear to be off base.  The technique described by ndbprr appears to require a dedicated oxidizer source, be it 100% oxygen as he mentioned or even only 40% oxygen.  A dedicated source may be practicable on a stationary or marine application where space is available but it would not be practicable on a railroad application since there's nowhere onboard to put the source and an entire infrastructure would have to be built alongside fueling facilities to refill the oxidizer source.

[ndbprr]

You are correct and it would not be done in that manner.  An oxygen plant (probably VPSA type) would be located next to the track.  A tank on the engine would be pressurized with oxygen of sufficient quantity to satisfy the grade and distance requirement.  Pure oxygen (in this case 95% oxygen) could be bled into the incoming air stream to enrich the oxygen content.  An oxygen sensor in the air stream would regulate the oxygen bleed valve.  40% content would not suffcicently raise the internal temperatures but that is my opinion based on my knowledge of running 100% oxygen systems which do significantly.