Turbo Diesel Waste Heat Steam Boost Enhancer Thread
 

By popular demand I have created the Turbo Diesel Waste Heat Steam Boost Enhancer Thread.

The idea is simple. Use exhaust heat after it flows through the turbo to boil water to create steam. Feed this steam into the exhaust manifold. The additional pressure and mass will increase boost which ups efficiency of the engine.

Assuming I can get a friend I have that loves steam engines to help me, I will implement it as a closed one pass system. I will place a water reservoir below the level of the exhaust manifold. I will then run brass or copper tubing from the reservoir to the base of the downpipe of my exhaust. once there I will wrap the piping around the tubing up to the exit of the turbo. The pipe will then tee. One branch will feed into the exhaust system and the other will go back to the reservoir to equalize the pressure.

This set up will not boil as much water as it can with the heat available however it will use the water to its maximum effect. Since the water level will be below the manifold. Steam flowing through the copper or brass tubing above the water level will continue to rise in temperature until it feeds into the exhaust manifold. This will minimize the temp drop of the exhaust gasses when mixed with the lower temp steam. I will also preheat the reservoir with engine coolant.

Every thing in the system will be at exhaust manifold pressure so I figure that designing the system to withstand 70 psi will be more than enough.

Really looking forward to this!

Very cool. I can't wait to see how it works.

I can see this working somewhat, but how will the power generated be used, and will this power generated overcome efficiency loss of the additional weight that you are going to impose on the system? Good idea, let's see if it bears fruit!

Funny has a good point. Have you thought about regulating the steam usage? So you can use it more while accelerating, and save up power when cruising at low speeds?

By mounting the reservoir forward of the tubing water will slosh backwards while accelerating and thus farther up the coiled tubing. The tubing that is normally out of the water should be heated hotter than the tubing that has water in it and thus help flash the water to steam. Also burning more fuel will accelerate steam production on its own.

Braking will slosh the water forward and thus out of the tubing reducing steam.

Weight is a concern So I'll just start off with a half gallon reservoir to begin with. With the piping filled it will probably be about a gallon total.

I am investigating what it would take to top off the reservoir with another tank of water and a high pressure water pump.

The problem as I see it is the heat it takes to expand the steam will reduce the peak combustion chamber temperature and therefore efficiency.

Now if you can preheat the steam and introduce it in the precise amount necessary it may be possible to increase mileage through the expansion of superheated steam, when the expansion ratio gets very high.

The requires steam at about 8-900 degrees, temperatures that are very short lived in a diesel engine combustion event.

It should be interesting as the concept of recovering heat energy from the normally wasted exhaust gasses is technically correct, but the actual accomplishment of any improvement might require some serious work, technique, and fiddling and adjustment.

I really like the passive system concept, following the keep it simple principle, and hope you succeed, so I can try it in one of my cars.

regards
Mech

I believe hes planning on injecting the steam back into the turbocharger before the exhaust turbine, not on the intake side.

I can't see any potential for savings here. An increase in induction pressure from an increase in backpressure sounds like tail-chasing.

I reread it Daox, and if he does that it will probably destroy the turbocharger.

regards
Mech

The more air you pack into the cylinder of a diesel the more efficiently it operates. Turbo charging a diesel is already a proven way to improve its efficiency.

How?

Exhaust already has a lot of steam in it.

Exhaust leaving the cylinders contains a very small amount of superheated steam, that started out as atmospheric humidity. It has to be very hot for the oxygen sensor to work. The range of temperature is something like 900 degrees.

It's called dry stream. Superheated steam is dry steam and the type that does not impact the turbine blades with significant mass. Superheated steam is a different animal compared to the steam you see coming out of your tea kettle when it begins to boil.

The expansion ratio of superheated steam is something like 1000 times water in it's liquid state, while steam that has just begun to boil at 212 degrees F, is just beginning to become a vapor with a heck of a lot lower expansion ratio than the same water when it is superheated to 900 degrees under pressure then allowed to expand.

Regular steam like what you are talking about is not the same as the superheated atmospheric humidity that has passed through your combustion chamber where it has been subjected to peak combustion chamber temperatures of above 3200 degrees F.

The turbine blades spinning at say 75,000 RPM will, most likely suffer damage, from being subjected to non superheated steam. You could also create another issue by cooling down the exhaust portion of the turbine housing with the injected steam that is not superheated and completely vaporized.

It's just my opinion, and I did not research the numbers I threw out extensively, but I have no doubt that the potential for damage to the exhaust turbine blades exists.

regards
Mech

The exhaust also contains a lot of steam from burning the hydrogen part of hydrocarbons. I sure wouldn't worry about the impact of any gaseous input. Big turbines are designed to survive bird strikes, rather than suck air through a grille.

The way I have described the design has taken into account for the water vapor in the steam. Boiling will only occur in the lower part of the tubing up to the water level in the feed tank. All tubing after that will serve to super heat the steam thus drying it. Further more once it mixes with the exhaust gasses it will be heated even more. As long as I don't try and generate as much steam as possible it will be perfectly fine.

Is the idea of injecting steam to increase the effective cylinder compression ratio? Can't that be accomplished by other means such as different bore, stroke, or combustion chamber volumes? Isn't there potential of driving the turbo at excessively high RPM?

Sure, any of those could work... none of those options can be achieved with $30 worth of junk, though.

I say let him try... :-p

I do have my own 2 cents to throw in here. Mechanic, have you consider store the steam in a reservoir and releasing into a 2nd turbo? Something to simply raise addition compression in the diesel engine when accelerating or pulse-gliding? Basically making a momentary boost in PSI by use of a secondary air injection. Not sure if theres any efficiency to be gained, but if you could tap a few (2-4psi) extra momentarily, it may be something worth trying as well. And you won't be blowing water vapor into your motor.

Interesting - I thought you couldn't pump steam - something I was told when onsite at a Nuclear station in the early 90s.

I'm not going to pump steam (although you can just like you can pump air). I'm going to pump water that will turn into steam.

Also I might decided to go with a design change. I found I can get an electric pump that does a gallon per minute at 60 psi. I'll uses this instead of the feed tank because I can set it up to intermittently inject water into the piping. This will allow the piping to heat up more in between pulses and produce hotter steam. It also allows me to turn it off when I'm at full boost and the waste gate is open. I need to talk this over with my steam buddy to see what he thinks of this as the sudden heat changes might fatigue the piping.

EDIT: Pump http://www.northerntool.com/shop/too..._357081_357081