Automotive Formulas For Engine Cylinder Perssure

[xxChrisxx]

I'm afraid not. The answer is zero; no moment arm, no torque. Can you see why?

 

[Jason Louison]

I'm afraid not. The answer is zero; no moment arm, no torque. Can you see why?

does it have to do with the fact that the crank angle is zero?

 

[xxChrisxx]

It does indeed. You are still applying the force on the piston though.

If it's not making torque what is it doing?

 

[Jason Louison]

well I know this:

When you generate torque on a static (non-moving/no velocity of any kind) Object, You are still indeed applying torque, but you are not generating any WORK. Correct?

 

[xxChrisxx]

The force is bending the crank. The thing to take away from this is that for every crank angle. The force acting vertically down resolved into a bending component and a turning component.

Much in the same way that gravity on an inclined plane resolves into a normal and perpendicular force.

 

[Dr.D]

There are inertial terms arising from both the piston acceleration and the connecting rod (linear and angular) acceleration. These are not constants, and are phased to be associated with each cylinder in turn.

This difficulty with the slider-crank machine is largely due to the kinematics. If you have a good device to handle the kinematics, then the correct equation for every cylinder is easily written using energy methods. This will have every cylinder moving in its proper phase, with the associated terms due to piston and connecting rod motion. To try to cobble together torque functions, etc. on an ad hoc basis is just asking for trouble.

 

[Jason Louison]

Yeah, the equations support this. Now, what I'm TRYING to figure out is how to get from (atm*mm^3+kg*degree/mm) to Newton Meters.
I'm sorry I'm probably frustrating you a lot.


*Note: the above graph is an approximation.

 

[Work Hard Play Hard]

Jason,

Thanks for the msg and I'll be answering soon but Chris and others will be helping you from here on.
Remember Newton's 3 laws of motion. You're dealing with rotational or angular analogs but they still apply. Body at rest, body in motion stuff. What happens at TDC?
It's also time to take off your "physics" hat and put on your "ME" hat with this project of yours. In physics, torque and moment are interchangeable terms. They are not to an ME. Wikipedia even covers this because it's so often misused.
Torque = (moment of inertia) x (angular acceleration)
Newton gave us this.
Furthermore remember equilibrium or here, "Rotational Equilibrium." At a steady velocity, steady can be zero mph or 100 mph, the net external forces of torque equals zero or the sum of all external torque's equals zero. You are going to have to start breaking things down and putting what you are looking for into context to properly organize and then understand it. But that's alright. It's what makes all this fun and you're doing well. As it was once put also, Chris and others are doing you a solid.
By the way, the compression ratio of your engine is 10:1 or 10.5:1 with VV.
----not everything was here when I wrote this----

 

[Randy Beikmann]

View attachment 114636

Yeah, the equations support this. Now, what I'm TRYING to figure out is how to get from (atm*mm^3+kg*degree/mm) to Newton Meters.
I'm sorry I'm probably frustrating you a lot.


*Note: the above graph is an approximation.

Before you get too far trying to convert this result, check the dimensions of your terms. The first part has atm*mm^3, or pressure x volume. This correctly gives you work units.

However, the second part, in kg*degree/mm, is in mass/distance, which does not make physical sense here.

I would go back and redo the problem, putting everything into SI units, and track the units every step of the way.

 

[Jason Louison]

Hi guys, Iv'e been SUPER busy the past few weeks so I didn't think about posting for a while. The spreadsheet has gone through a series of MASSIVE updates, But I won't put in multi-cylinder engine support until a few roadblocks are cleared up. For now, I will post this screenshot and upload the spreadsheet for you guys to check out!

 

[Jason Louison]