Long story short, I need a P-V diagram or T-S diagram for the 13b.
I'm designing an intercooler spray bar for my senior elective. What I have so far is the air temperature coming out of the intercooler for various levels of air comsumption. However, I don't know how to figure out the temperature of the air after compression prior to ignition. I'm trying to see how much more boost can be added without detonation by using a water spray system. If anyone knows where I can find these charts I'd be most appreciated. I've taken a look at ideal and actual otto-cycle diagrams but I don't think the rotary technically follows those due to the rotational compressive nature. Thanks!

 

Sorry, I don't have any, nor do I know where they can be found.
Of course the manufacturer has them. Sometimes highly technical research papers are published by the SAE which are provided by engineers at the manufacturer are available to be purchased by the public.
Most times the abstract the SAE provides does does not give you enough info of what is contained in the paper so that when you purchase it you may find that the info you are looking for is not there. Sometimes it is.
Good luck. Bob

 

Try your luck here.

http://www.sae.org/technical/papers/ground_vehicle/SI

 

It shouldn't be any different then that of a four cycle piston engine that share the same intake, compression, ignition and exhaust cycles. I don't think those diagrams would be of any help to you anyway, since the ones I'm looking at in "Thermodynamics: An engineering approach" right in front of me don't show any hard numbers. Plus, the pressure and temperature of the fluid is engine-dependent, on VE and other factors, so even if the graphs did have numbers and you did find one for a 13B, its probably only valid for a given set of parameters, ie, 3000rpm, 21deg C ambient temp, 400m above sea level, etc.

I don't think this one requires a T-S or P-V diagram like you are looking for. What would help here is someone's 13B fuel map, because with that you should be able to find VE at many different points using the actual fuel requirement vs the theoretical fuel requirement.

If you have VE and intake manifold pressure (both can be found on a fuel table), you should be able to calculate actual air mass into the combustion chamber. You could also use the air/fuel mixture reading though. Given these parameters, you can use ideal gas law (ignoring that you have fuel vapor in the mix) to get an approximation of what the temperature would be using m= PV/RT and solving for T. Then using the engines compression ratio to calculate volume at TDC (volume of one chamber at BDC is 653cc or something close) you can find the pressure after compression and by using ideal gas law again, you can find temperature.

This is what I would try. I hope it works. Let me know!

 

I didn't take the time to look, but there is probably a diagram in here:
http://smrmicro.com/re-ky.pdf

 

Thanks for posting. Great information. Anything more up to date?
Sorry. I know. Never satisfied :>

Bob

 

sorry

 

Sorry, forgot to keep keep checking this thread, senior design has been killing me....


What I ended up doing was using the basic ideal gas equations and estimating the 100% isentropic compression. I know this isn't too accurate but after looking at all the different variables I figured this was my best bet. I took into account the vaporization of fuel at a given A/F ratio and the volumetric efficiencies of the 13b-rew I found in SAE paper 2004-01-1790 which was published by Mazda.

I created an air consumption spread sheet based on rpm, volumetric efficiency, and positive boost pressure. I then matched the air consumption vs boost on a compressor map to determine the isentropic efficiency of the compressor at various boost levels. This gave me an accurate way to estimate the turbo exit temperature, pressure, and density of the air. I then used a basic 80% intercooler efficiency to determine the air temp entering the engine. After doing this, I imputed these initial conditions to the ideal isentropic compression equation and subtracted the heat lost to fuel vaporization. This gave a rough estimation of the final compression temperature.

It turns out that the final temps for 20 psi were about 520F which is right around the auto-ignition temp of gasoline. This leads me to think that my data analysis is reasonable as 20psi on a 13b with pump gas without auxiliary injection is VERY prone to detonation.

I then took the heat lost to the vaporizing water on the intercooler (assuming all the water evaporates of course) and was able to determine the benefits of using an intercooler spray bar. It turns out that by spraying 0.3 lbm/min of water onto the bar, the compression temperature is reduced to 480 degrees at 25 psi and 460 at 20 psi. This is a tremendous gain. If you were to use this system for approximately 30 minutes straight, you would require 2 gallons of distilled water. Due to all the assumptions necessary to complete these calculations and since no real-world model was produced, I would take this with a grain of salt. 0.5 lbm/min might be more of a safe bet.... One thing is for sure, Subaru has used a similar setup with great success so if auxiliary injection and turning is not a possibility due to knowledge or budget, it seems that a water spraying intercooler bar would be a great alternative.

 

i use a water to air intercooler system, 4 gal. tank, pump, small radiator in brake duct. so far no detonation 93pump 19-20 boost, 420whp,, long open hyway runs tho are a little suspect, you know 10miles at 20 psi steady. i think water injection into the intake system is great for such! but its time to step up to direct chamber injection im sure mazda is R&Ding right now for rotary.