Propane Injection

[Lextreme II]

What do u guys think of using propane as a source of cooling medium for the root style supercharger? Back in the days it was very popular for the Grand National guys to use propane. Any comments?

 

[cribbj]

Even if the engine is running full time on propane, there's not enough flow to do a good job of aftercooling a boosted motor. I had a process engineering buddy run the numbers on propane in 2005 when I was considering building a combination vaporiser/intercooler.

On the other hand, methanol injection does a great job. He ran the numbers on it, and found that with enough methanol, the charge air could even be cooled below ambient! (That's with ridiculous amounts of methanol, however.) Starting parameters are charge air at 140C, 2 bar pressure at about 25kg/min flowrate (WOT for a 1UZ).

I would expect a methanol/water combination to work also with much lower amounts of injection, but perhaps not quite as much temperature drop.

Here's the graph he came up with, using HYSYS, a high end process simulation program:

 

[Lextreme II]

John,

Is your engineer buddy still around? Perhaps if he can plot the above graph with propane.

P.S. Why you can post pictures and I can not? What setting do u have?

 

[cribbj]

David, I'd asked him to simulate flashing (vaporising) liquid LPG in the tubes of an intercooler, with charge air flowing across the tubes.

Initial conditions were the same, ie:

25 kg/min of charge air at 2 bar flowing across the tubes at 140 degrees C

1.2 kg/min of LPG at 25 degreed C, flashing to vapor

I asked him to solve for the exit temperature of the charge air.

p.s. I'm having a hella time posting pics lately too. The only way I could get these to post (after 3 tries) was to enlarge them to 1024x7xx size. Think we need to get mybrainisimmense on the case......

Here's what he said:

OBJECTIVE OF THIS CALCULATION:
FIND MINIMUM AIR OUTLET TEMPERATURE THAT CAN BE ACHIEVED

Imagine you manage to expand the LPG liquid through a valve just to the bubble point, this is to say, that starting to boil liquid can enter the exchanger. This is the best case you can have, as vaporization heat can be completely given to the other fluid (air). Normally this is desired as vaporization heat is in the order of 1000 times the equivalent non-state change heat flux

Of course, a real isenthalpic expansion through a valve will cause LPG partially to vaporize (or all LPG, because of the high amount of a single component, starting and ending boiling points are very close, near 4ºC difference).

Let’s assume we have the first case and no vaporization is found at the entrance of the exchanger. In order to be in a more optimistic case I assumed bubble point at pressure 2.75 bara (temperature -8ºC).

The pinch analysis is an easy tool to determine thermodynamic constraints within an installation. It is a comparison between the available energy of both sides of the exchanger and which is the maximum temperature (for cold fluid) and minimum (for the hot one) that can be achieved in an exchanger of infinite area an infinite residence time (this is to say, the thermodynamic limit)

As you may find in the following graph, the limit is 109 ºC. This means that, the outlet air temperature will be always over 109 ºC (this is in accordance with the HYSIS result of last days, outlet air temperature was around 130 ºC).

As heat capacities are in the same order for both air and LPG, significant difference in the slopes of the curves you can see in the graph, are due only to the ratio of mass rate (25:1). We will conclude that the mass rate of LPG is not enough to cool down the air.

Fuel composition, is 90% propane, 5% propylene, 5% butane. All physical properties are close enough to propane so as to use them for the study

Pinch Curve follows, along with a table of initial values:

 

[Anaema]

propane won't do a very good job at cooling an air charge because it's boiling point is much lower than ambient temp. that is why it always comes out as a gas in propane stoves and other such applications. I really doubt that propane will be of much help cooling anything in an engine.

the reason water, Ethanol, and Methanol cool so well is because they absorb heat very well, and have very high boiling points. so it takes a lot of heat to turn either one into a vapor. the higher the boiling point, the more heat it takes away from the air to be converted into the gas state(of matter).

propane makes a great stand alone fuel for the same reasons it makes a poor coolant; it has a low boiling point. it also has a very high octane rating, so much cooling isn't needed.

 

[badasstoyotas]

I just read this thread for the first time. I also have to disagree very strongly. propane comes out of the nozzle at -60 degrees and will not detonate with out a spark. you don't want to inject it before the I/C you want it right before the TB.I will find some of the pages that Ive read to learn and reamber the things.