BMW Turbosteamer Discussion

Back in 2005 BMW showed an interesting concept device that was designed to increase the overall efficiency of conventional ICEs. This system is dubbed the turbosteamer. It seems like an elegant way to recover energy that is otherwise wasted.

One of the better articles about the turbosteamer can be found: [URL="http://paultan.org/2005/12/11/bmw-turbosteamer/"]Here.[/URL] Another article which includes the official BMW info about the system is: [URL="http://www.autoblog.com/2005/12/09/bmw-turbosteamer-gets-hot-and-goes/"]Here.[/URL]

The system is based on the well-known and thoroughly developed technology of steam engines. Basically there are two circuits involved, a high pressure high heat circuit and a low pressure low heat circuit. The high pressure circuit uses water as the base medium and the low pressure circuit uses ethanol as the base medium.

The base engine in the prototype is BMW's N46B18 1.8L I4 that produces 115hp stock. According to the claims the system can extract over 80% of the waste heat from the exhaust. The steam system produces an extra 14hp bringing total engine output up to 129HP. Fuel consumption is reduced by 15%.

Now comes a question to be answered: [B]How efficient is the turbosteamer system???[/B]

do you mean, the system alone or the whole car equipped with that system?
Answer to the first question is difficult to say, as extracting 80% of heat without saying how much it is, doesn't give a good info on how much power it was extracted as oppsoed to the 14 bhp provided at the engine.
It surely has an 80% efficiency extracting hear :D
Answer to the second, assuming the engine is averagely efficient (25%), this system seems to boost it to... 28%?

The question applies to the system alone and in concert with the engine. Basically what I am really trying to get at is the interpretation of how the system works.

Personally I believe that the 80% recovered heat is used to power the steam system which in itself is not going to be more than 40% efficient. Given this interpretation one can calculate the total heat lost in the exhaust which is approaching roughly 50%.

However revetec has a very different interpretation that leads to a total heat loss through the exhaust of only 18%

I dunno if you know hightower, you've been arguing with revetec for ages but it seems pointless. I am fairly confident he is a scam artist.

[quote=hightower]Personally I believe that the 80% recovered heat is used to power the steam system which in itself is not going to be more than 40% efficient. Given this interpretation one can calculate the total heat lost in the exhaust which is approaching roughly 50%.[/quote]

How do you get 50% power lost through the exhaust. Based on a 40% steam system efficiency I would estimate a 27.5% power loss in the exhaust (ignoring losses through the cooling system):

14 Hp x 1/0.4 x 1/0.8 = 43.75 HP (total power loss thru exhaust)

(115 Hp + 43.75 Hp) / 43.75 Hp = 27.5%

What am I doing differently?

Kitdy: I don't think Brad (revetec) is a scam artist at all. I believe that he truly believes in his own design. However I also think that he is misrepresenting several facts and IMO shows a somewhat incorrect understanding of some basic concepts. Other than that he seems like a dedicated engineer/entrepreneur who has put all his energy into the revetec project. I consider the fact that he is willing to even participate in a public forum a bit of a gift as it supplies a great view of what it really takes to try and bring a new idea from concept to fruition.

Alastor: Bare in mind that the 40% steam system efficiency is an upper limit. Also I calculated the total loss using the relative efficiencies based on a given efficiency of the engine. I was incorrect. I actually didn't think to do the calculation that you did which seems to show the value correctly.

The steam system seems to get the majority of its input energy from exhaust heat however the cooling system is used to heat the low pressure circuit. Even assuming a 20% contribution towards output that means that roughly 11.2hp is made from exhaust heat.

The 40% steam circuit efficiency was calculated from the given temperature difference in the heat exchangers (800degC to 50degC) with the endoreversible Carnot efficiency equation: Eta=1-sqrt(Tc/Th) where Tc is the cold sink temperature in Kelvin and Th is the hot sink temperature in Kelvin. This actually gives a maximum of 45% but there are heat losses in the heat exchangers that aren't included. Hence my thinking that 40% is a probable upper limit.

It is interesting to find the turbosteamer system efficiency required to lower total heat loss through the exhaust system to 18%

Search in google

its a good investment for BMW for making such project but i dont think it is succesful. i search for the most latest article regarding this project but found none. hybrid technology is still the best up to now so i dont think they will still continue continuing the turbosteamer project because they will be having lots of changes on their [URL="http://www.partstrain.com/"][COLOR="Black"][U]car parts[/U][/COLOR][/URL].

Could this idea be improved by using another medium more effecient at transferring heat than water is?

Thanks!

Jacob Potts

I never understood the point of having all these shenanigans when you could have a 6-stroke motor? Perhaps thats why BMW hasn't unveiled any new concepts or done any development for 8 years now?

[quote=Jacob Potts;1001313]Could this idea be improved by using another medium more effecient at transferring heat than water is?

Thanks!

Jacob Potts[/quote]

Likely! However, water probably beats said material on a per unit cost!