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-   -   2-cycle engine modeling (http://www.cfd-online.com/Forums/main/4004-2-cycle-engine-modeling.html)

Roy Perryman October 15, 2001 14:25

2-cycle engine modeling
 
What CFD packages are available that will accurately model the combustion and scavenging processes (for 1 complete crank rotation) of a piston-ported 2-cycle engine? Ease of use is important, as I have never used a CFD program before. Also, any literature suggestions will be greatly appreciated.

Thank you in advance for your input.

King Tut October 15, 2001 16:24

Re: 2-cycle engine modeling
 
you best bet is KIVA.

John C. Chien October 15, 2001 19:37

Re: 2-cycle engine modeling
 
(1). Good Grief! Can't you just visit the sponsor's websites? or type "two-stroke engine cfd simulation" into the search engine?

John C. Chien October 16, 2001 02:00

Re: 2-cycle engine modeling,a short comment.
 
(1). There is no future for CFD, as long as CFD is interpreted as code development and code running. (2). After reading one book on FrontPage three times last couple of weeks, and begining to read another FrontPage reference book, I think, item-1 is going to be my conclusion based on my observation. (you don't have to follow my comment) (3). The obvious difference is: in the FrontPage case, I can get exactly what I want, by following the instruction. And it really helps me a lot, even though I know how to use HTML. (4). Based on my experience with the commercial CFD codes or in-house CFD codes, life was really miserable in running the so-called CFD codes in real life. (5). In other words, using FrontPage, you get happiness out of using it, while using CFD codes, you get more un-answered problems and questions. Your question reflects this kind of fear, which is rather common in the running-CFD-code environment. (6). So, if this can be called the current approach, then it is fundamentally wrong related to CFD field. (7). The two-stroke engine is a complex problem. It is transient, moving boundary, compressible, turbulent and reacting flow. In this case, it would be easier to take the experimental approach, that is trial-and-error approach. And I had used a two-stroke engine lawn mower for over ten years. It is simple and reliable. (8). The best we can do today is, simple turbulent flows with favorable pressure gradient. With the adverse pressure gradient, most turbulence models will give wrong solutions. With moving boundary, and reacting flows, you probably need a super-computer of your own. (9). I still think that CFD is a death trap. The trouble is, you are pretending that you know how to solve the problem and that all you need is a CFD code. In reality, to solve a simple square cavity with a moving wall alone(3-D) is easily a PhD dissertation subject. Even if it is very accurate, who is going to hire you? to do what? (10). I am sure that there are special cases. So, if you are one of them, then you are the exception. Even in aircraft aerodynamic design, the CFD results are largely used to confirm the huge data base of testing. (in other words, it is extra work to show that testing is all right.) I am sure that there are ways to do it right, but that is something else. If you need a CFD code to run, you can not go very far at all. You will get stuck. Anyway, I will have to stop here and go back to do more reading about the FrontPage.

bala October 16, 2001 05:37

Re: 2-cycle engine modeling,a short comment.
 
hi John! I totally agree with you. Now nearly every engineering student pretends that s/he knows how to solve a fluid mechanics' problem and all that is needed is a CFD code. Using a CFD code is taught on undergraduate course in the name of teaching CFD. The students acquire little or no knowledge of basic fluid mechanics and fluid dynamics. They can't see that for many problems they can use analytical solutions of simplified variations of N-S =ns and don't need to solve full set of =ns.

I don't know if computational solid mechanics codes are propagated in a same manner.



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