Wankel Engine Design

Go to google and type wankel engine. The images that will appear will tell you better that I could do.

Ideally, no leakage in the engine seals is desired, as occurs in the current piston engines in our cars. It enters in the "efficiency" coeficient of the engine, it's a natural loss.

Additionally adding to poor efficiency of the Wankel is the unfavorable surface to volume ratio of the chamber formed by the rotor and housing for combusion. In that respect, the pistion engine is much better, especially long stroke, small bore engines.

Bernie Katz

I suggest you look for info on the evolution of the RX-7 / RX-8. Bernie is right about the poor efficiency of the Wankel. They just aren't able to achieve the levels of compression that a conventional piston engine can. However low compression means these are perfect candidates for turbos with lots and lots of boost.

Apparently the new naturally aspired engine used in the RX-8 has been vastly improved in regards to efficiency and performance. A Google search could probably provide the specific info as to why.

Tip and side seals have always been a problematic area for Wankel engines. You'll need to do extensive research into these and many other areas to retain the essential geometries of a Wankel, but to improve upon what Mazda has already done. You might look into the early Wankels used in NSU autos, too. Perhaps by seeing the turns that they took with the design, versus those taken by Mazda, you can come up with yet another direction.

The Wankel engine has not lived up to expectations in automotive use. Because the rotors do not have a simple circular motion, imbalance still occurs, so they don't have much advantage there. (And imbalance in modern engines is a small issue -- few people complain of rough engines these days, and some are so smooth, you'd hardly know they are running.) So where is the advantage? They have obvious thermodynamic limitations and have never been demonstrated to be as efficient, let alone more efficient than piston engines (in terms of BSFC). Their real virtue is compactness, and reasonably light weight, so in some aviation applications they may have promise (see http://www.moller.com/).

With current side and tip seals, I'd guess leakage around those seals is a very minor issue (until, of course, they wear out), just as blow by is an almost insignificant problem on a piston engine in good condition. As engines continue to improve in efficiency and emission control, variable valve timing becomes more worthwhile. With a Wankel, the equivalent is not easy to achieve.

I'd suggest searching all the Wankel and rotary engine patents as a starting point.