Propane injection (was Nitrus injectors (was Hydrothermal Biomass-Fueled Engines))

[Joe Chiasson]

> Considering how much frost is generated around a propane leak, I would
> imagine that the intake charge will be cooled considerablly.  Injecting
> the propane upstream will allow the propane to completely vaporize, and
> therefore extract as much heat as possible from the air.  (As I said
> before) you want to keep gasoline in a liquid state until it enters the
> cylinder because the gasoline vapor will just take up space.  Propane,
> however, will absorb heat  as its evaporating, and thus cool the charge. 
> We therefore want it ALL to evaporate.  That is, IF the cooling effect is
> enough to make up for the volume of the added propane.

And thats my argument,  I feel to benefit from liquid injection you want as
much as possible to enter the cylinder as a liquid.  Propane expands 272
times based on volume as it transforms from a liquid to a vapour,  tries to
chill everything around it to -44F.  Lots of displaced air if injected into
throttle, pretty much the same amount displaced by a mixer.  Granted you do
have the cooling going on in the manifold instead of a vapourizer off to
the side, taking that into account will net you more power as compared to
the mixer, but you will probably only have 87% of the power when campared
to equivalent amount of gasoline lb/lb and 79-81% of the power when
compared to liquid injection into the cylinder or near the intake valve. 
Just my opinion.

> I found a list of the properties of Propane on the web (unfortunately,
> it's at work right now).  I still need a list of the vapor pressure at
> various temperatures so that I'll know how much the vapor pressure
> changes with the temperature, and how much pressure I'll need to keep all
> of the propane in a liquid state in the tubing that will be in the hot
> engine compartment.
 
www.geocities.com/CapeCanaveral/Hangar/2179/Pres1.jpg
www.geocities.com/CapeCanaveral/Hangar/2179/Pres2.jpg
Are a pressure v. temp curve someone did up a while a go for me, and
saturation pressures of pure propane.

Also here are some properties from "Alternative Fuels Guidebook :
Properties, Storgae, Dispensing, and Vehicle Facility Modifcations" by
Richard L. Bechtold.  Note that these are for pure C3H8, and probably
differ form other sources as I have ran into on occasions.

MW = 44.09
Density, kg/L, 15/15C = 0.5 = Specific Gravity
Density, lb/gal, 60/60F = 4.2
Freezing Point = -187 C = -306 F
Boiling Point = -42 C = -44 F
Vapour Pressure, kPa @ 38C = 1303
Vapour Pressure, psi @ 100F = 189
Specific Heat, KJ/kgK = 2.48
Specific Heat, Btu/lbF = 0.592
Viscosity, mPa.s @ 20 C = .102
Latent Heat of Vapourization, KJ/Kg = 426
Latent Heat of Vapourization, Btu/lb = 183
Lower Heating Value, 1000kJ/L = 23
Lower Heating Value, 1000Btu/gal = 82.4
Flash Point = -104 C = -156 F
Flamability Limits (Vol%) = 2.1 Lower, 9.5 Higher
RON = 112
MON = 97

Most pump propane is sold as HD-5 (GPA 2140 HD-5, CAN/CGA-3.14-M88) which
simply states not less than 90 liquid volume percent propane, and not
greator than 5 liquid volume percent propylene.  For the most part Propane
90-99%, Propylene 0-5%, ethane 0-5%, butane 0-2.5%.  The farther south you
go typically you get more than the 2.5% butane, the more butane the lower
the vapour pressure of the LPG.

> That's part of what I want to determine.  I need some injecters that'll
> handle about 200PSI, and a pumnp that'll increase the pressure to 200
> PSI.  A standard in-tank fuel pump might do the trick, since it'll just
> be increasing the pressure from 150 PSI up to about 200 PSI - an increase
> of only 50 PSI.  The only trick will be to either seal or pressurize the
> motor so that it'll operate at an ambient pressure of 150 PSI.
 
Standard LPG tanks in the USA (for motor fuel) are built with a 312.5 psi
pressure relief valve.  Regualtions and guidlines recommend lines and tanks
to be able to operate at a working pressure of 312.5, with a pump in the
tank working pressure of the lines would have to be ~360 psi.  
 
> The purpose of the fuel pump is to get the pressure above the vapor
> pressure of the propane.  I plan on keeping the pressure constant, not
> varying it to control the fuel.  The standard method is to let the pump
> run wide open and restrict the fuel goinng to the return line.  That way,
> the pressure at the input of the injecters is kept at a constant value. 
> I plan on running the system at arount 200 PSI, but I need to see a table
> of the vapor pressure of propane at various temperatures before I make a
> final decision.

Restricting the fuel going to the return line is fine and dandy, however
looking at the vapour pressure curve you will realize thats its not going
to be that easy.  To pick a constant opeartion pressure wether its going to
be 100, 200, 300, 400  psi or whatever, is going to be hard to accomplish. 
Waking up in the morning after a 40 F night and your fuel pressure will be
~ 60 psi, later on in the day after it warms up and you have driven for a
while you could have 200 psi tank pressure.  

-------

Say I wanted to run 250 psi +- some factor, constantly.  I also want to run
-40 to 120 in fuel temp thus tank pressure unboosted would be from ~ 0 psig
to 230 psig.  Is there a pump that could get me boosts of 250 psi and as
little as 20 psi ( all out of the same animal  which is not much larger
than a gasoline intrank fuel pump), without by passing into another tank or
something.  Or are multiple pumps in parrallel shutting pumps off the
higher the inlet pressure gets, the only answer???


j.