ken-x8

Economics? That explains how he became an expert in epitrochoids with one day of study.

I'm surprised that he needed any help from his Mensa buddies.

Ken

SIPSOIL

Still here...

Interesting stuff:

Patent US5305721 - Rotary Wankel type engine - Google Patents

"Riblets are defined in the combustion face of the rotor to promote aerodynamic lateral stratified charge control to minimize atomized fuel charge loss to surface wetting before ignition."

If the riblets are angled on both sides an additional effect could be that the density of the air/fuel mixture around the center plugs is increased. There are a lot of interesting things one could do with a really wide rotor.

Cooling the rotor:

Maximize the dimensions of the lobe on the e-shaft. Helical groove(s) in the lobe is an Archimedes' screw that transfers oil along the shaft lubricating and cooling it. If the grooves spiral out from the center there will be a temperature difference between the center of the rotor and the sides, but differences in oil pressure between sides should be very low.

Engine management system:

The following setup uses a PIC32 ucontroller, shows the the basic principles (optically isolate inputs, etc) and illustrates that no knowledge of rocket-surgery is required.

Retrofit Engine Management System : Design

I think all this makes for great work-avoidance projects.

RIWWP

iTrader: (2)

Our rotors have 'riblets' that I expect is to reduce stratified charge loss as noted in the patent.

Your link is proposing a rather simple ECU that is inferior to what we already use, and is intended to retrofit engines that are pre-OBD2, i.e, engines older than 16 years old. It is also just an ECU concept that was designed as part of a contest that ended 3 years ago, with zero development since.

Doesn't really help your case.

SIPSOIL

Good luck getting your own software to run on "what we already use".

The PIC32 isn't powerful enough to run the more sophisticated algorithms I'd like to try. Sparkfun does have a PIC32 development board with all the I/O pins broken out that can be re-programmed by USB, but the beaglebone is much more suitable.

You think having to hook up some tool to read and interpret some code Pxxxx code is state of the art? The beaglebone has HDMI-out and if you can make it display the spectrum of the engine vibration on a pink background with green stars.

Missed the point. It is possible to make a custom ECU and studying the schematics and source code of one made to retrofit engines is a good starting point for anybody wanting to make a custom ECU.

RIWWP

iTrader: (2)

Yeah, I missed that point. My bad.


I just have no idea why you would want to write your own ECU. The development time for existing aftermarket ECUs is pretty telling for how complex it actually is. Presuming that you have a high paying job that exercises your Mensa brain cells, you can afford a solid aftermarket ECU with a fraction of a year's salary, vs spending years or decades on developing your own.

Doesn't sound like an efficient use of your time unless you think you can develop something that has never been thought of before.

SIPSOIL

I suck at doing crossword puzzles.

Remember that one of the problems with overlapping ports is that we'll have non-linear feedback as the condition on rotor face 1 will effect the condition of rotor face 2, which will effect rotor face 3, which will effect rotor face 1, and so on.

It is not guaranteed that this effect will dampen over time and even minute differences will amply and lead to oscillation (possibly even chaotic - in the mathematical sense), which is highly undesirable.

Now, TDNNs for example can emulate and predict mildly chaotic systems (such as Mackey-Glass), so one idea would be to see if such a network can be trained to choose a set of inputs (such as ignition and injector timing) that minimizes these feedback effects, subject to secondary conditions.

Maybe it works, maybe not. But it's certainly a lot more fun than doing crossword puzzles.

SIPSOIL

Ok, the correct keywords for the proposed solution concerning rotor lubrication and cooling are:

"Helical groove bearing"

If oil is fed through the inside of a hollow e-shaft, passes into the rotor baring, and exists through the e-shaft bearing, centrifugal forces and the action of the groove pushing oil through the bearing, might create enough pressure to eliminate all other oil pumps.

Of course, oil would need to be fed into the center of the bearing surface and the helices on either side would need to be of opposite handedness to eliminate a pressure differential on the e-shaft ends.


Edit: here's a pic, but I think the relative size of the groove would need to be much larger, as we're not only lubing the bearing, but also cooling the rotor.

RIWWP

iTrader: (2)

I found this thread that may interest you:
Anyone every thought about combining rotor housings? - RX7Club.com

This one may also be of interest, since he went a bit further than just talking about building his own engine:
4-Rotor FC Build - RX7Club.com

SIPSOIL

"[...]a non turbo 4rotor is actually about the same amount of work than this 2+2 design[...] Plus it has been done already so I know it works[...]"

Good reasons.

However, I'll argue that because we know a 4-rotor engine design that uses (mostly) stock rotors, (mostly) stock irons and (mostly) stock housings works, we don't need to talk about it at all!

Nevertheless, thank you for the constructive criticism.

The most interesting part was a link to this Patent which contained the following statement:

"The length of one side of the triangular face of the rotor is at least 2.4 times the breadth of the rotor."

Now, this is interesting. Does this mean that an over-wide rotor must have unstable combustion? Not really, because the paper assumes that there are only two plugs.

EDIT:

Having lots of pugs means lots of possible configurations and lots of opportunities if you're and optimist and lots of problems if you're a pessimist.

SIPSOIL

This is *very* interesting: Design of rotary engines from the apex seal profile (Abbr.: Rotary engine design by apex seal)

According to Kenichi Yamamoto, Mazda housings are an epitrochoid + apex seal height displacement which means the profiles of the apex seals are circular arcs. However, we can achieve better gas sealing with an apex seal profile (and corresponding housing) design that takes the varying pressure differential into account.

To do: Describe gas leakage as a function of pressure difference, apex seal profile and housing surface. Minimize the integral of this function (I'd be very surprised if this can be solved explicitly...)

[EDIT]
Found this paper: http://www.msshadloo.com/down/Analys...kel-Engine.pdf