03-07 Calculations and Models (Solidworks, MATLAB, EXCEL) cont...

Here's the video slowed down to 5 RPM's...

[ame]http://www.youtube.com/watch?v=tQP6BvfM2Qw[/ame]
 
Originally posted by TheBac....

TheBac said:
Amazing work so far. It would be exceptional if you continued the analysis like you described.
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Cummin-a-long said:
If you want to see it taken out that far, we'd have to redo the piston with the actual measurements and not just the eye-ball setup I did there. The other thing we'd need is someone that has a head and injector out on the table to get an installed protrusion depth.

After that it's just setting up the redundant calculations, which excel or matlab can do quickly. These would give you your true min/max points. You still have to calculate your mass flow rate for your air, so you can calculate what you actually need in mass flow rate for your fuel at each given point.

That's a LOT farther than I had planned on taking this setup.

Can we do it? Sure.
Can we set it up so all you have to do is plug in a few variables? Sure.
Do I really want to do that much work? Not really.....

This may be something I'd be interested in sitting down with a FEW others and breaking it down into manageable portions though. Making seperate functions, like I showed in the earlier calculations with matlab or excel, and letting those feed / call each other could make a really powerful calculator for this.

I usually don't give a crap about sharing some of the simpler tools I make but some folks get a little touchy about that.
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Please don't think I'm trying to marginalize the question, it's just a lot of work.

Here is actually what goes on in the background of something like that and this is for a MUCH simpler mechanism that doesn't have any thermo properties to worry about.

This is just the last of the 88 lines of code for the motion of a mechanism that works similar to a crank, rod and piston setup.....and this is just for the motion and forces.

Crank%20Slider.jpg
 
The more I think about this, the more I actually want to model this out fully. PLEASE do not think this is going to be something quick and easy, but I figure in the long run it saves me time anyways.

What I'm going to do is accurately model out the 0304 CR piston. I'll give you guys the Solidworks file for the piston top, as that's really the only important part for all of this anyways. It won't have any valve reliefs cut in it, it'll just be a blank piston and you can do what you want with it.

Thank you Smokem for the dimensions.

0304%20CR%20Piston.jpg


Again, this is not going to be a quick and easy project, this is gonna take me a while and my time is usually pretty short so it'll be something I do in my spare time. But, in the end the goal is to be able to enter a minimum of parameters and generate all of your fuel and timing tables based on those inputs. I'll try to set it up in Excel as most people have and can use that vs Matlab and Solidworks.
 
Here's the rendered model. This is just for the top of the piston but it will at least give an accurate model to use.

0304%20CR%20Piston%20Crown%20Preview.jpg
 
Okay, here is what I'm going to try and do....(I do have other things I ACTUALLY need to accomplish).

I'm going to try and do one part of this each day. Here is an example of how I'm trying to set this up. This is just calculations for your airflow where all you have to enter are some VERY basic parameters....your engine displacement, head efficiency (if you know it), how much boost you're making, your altitude, and the temperature.

All you'll have to do is enter the values in BOLD RED. DO NOT mess with any other cell, there are a ton of embedded formulas and you WILL screw it up.

I'll post these as actual files later once I'm happy with them, but here is what you'll be looking at.

This one is for your airflow.....

Airflow%20Calculations_zpslwkq6zkf.jpg
 
Awesome work!

Isn't .900 volumetric efficiency a little overly optimistic for these engines? Or is that assuming it is under forced induction and taking that into account?
 
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Chrisd91 said:
Awesome work!

Isn't .900 volumetric efficiency a little overly optimistic for these engines? Or is that assuming it is under forced induction and taking that into account?
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That is specifically why I put that in there as a variable that the user can edit.

Those numbers in red will be the number YOU can modify and the outputs will adjust automatically. The only numbers you need to put in for YOUR specific application are those numbers.

I had to put a number in there so the calculations wouldn't show "error". You'll be able to set those red values to whatever fits your application when I actually give you guys the finished files.

I'm just trying to set it up so that the end user needs to do very little math or know very few background equations but can produce a result that will at least get them in the ball park and not just in the state.
 
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For example....

What I'm going to do with the fuel tables is create the fuel quantities using stock injector values and the user will input their "percent over" value to get quantity in MM3's.

I'm going to try and set it up so that the user can put in EITHER pressure or duration based on those numbers and get the other value needed to meet that MM3 value.

The fuel will cross reference the air flow table to give you a specific value that you can actually support based on your airflow inputs.

Like I said, I'm going to try and make this as simple as possible for the person that has ZERO knowledge of programming, equations, thermodynamics, etc....
 
This is great! I made something like this in UG and using Excel (no longer have a licence to MatLab :-( ). I was also only doing ppump stuff, so I didn't need to log as much as you are. What I found was, I was using properties for just diesel fuel, and not taking into account that there is air mixed in (this is why pressure in a rail isn't just based on the current stroke of the pump). I never nailed it down, but because of that, and the fact that pressure will be dropping after the initial crack/pop, it threw off the results a bit. I suspect that the pulsing of the air, and heat of the fuel played a role as well.

Anyways, keep up the good work. This is pretty sweet! I'm looking forward to the finished setup.
 
Corey, you know as well as I do that you can never have enough eyes on something like this. If you see anything I'm screwing up in this, please let me know.

For example, the airflow I'm doing here is dry air, not humid air, which obviously throws it off a bit. There will certainly be some fudge factor in this as there will be infinitely many variables that people won't be able to log or even remotely correctly assume.

I'm just going to try to get it to the point that a guy building his own tunes would be able to create his own tune from nothing but zeros and get it idle correctly on the first fire and not look like a coal train going down the road.
 
I'll probably work on it a little bit tonight and get the fuel to air mass conversions done.

Ideally what I want to do is have it reference the air flow, reference the users desired stoich, get the fuel mass and then I'll try and set it up so the user needs 2 out of 3 variables (pressure, duration, or MM3) and it'll spit out what that 3rd variable is.
 
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