Opposed Piston Diesel Engine

Half-baked idea.

I've been looking at Opposed-piston_engines and I'm interested in them, particularly the M4+2. I really like this one and this too. This is my try at designing one.

A different approach: http://www.gizmag.com/duke-engines-axial/33631/ or this: https://www.youtube.com/watch?v=aZB0Go3Kj-k

Goals

The goal of the engine is to simplify design. With a focus on fewer parts and easier to fix. Because of CNC manufacturing, the solid parts can be complex and precise, so long as replacing them is simple.

Pistons

The pistons are opposed in a single chamber. To be lighter, the pistons should sort of cup shaped.

The pistons have 3 rings, the outer two consisting of permanent magnets with opposing poles. I'll probably make the core out of steel to help with the magnetic field. This design allow for acceleration powering the windings like this:

 ---NNSS
 --NNSS-
 -NNSS--
 NNSS---

I'd like to see if the pistons can be machined with enough precision to not need rings. A v2 improvement would be looking at ways to reduce friction with something like fluid bearings.

Cylinder

The outside of the cylinder will be steel pipe. I'll make an inner core of wound enable copper wire, with several stages (I'd guess 6). The inner layer will be smoothed with high temperature epoxy. I think the best approach is to make a wax cylinder the exact size of the piston, and then melt it out after the epoxy has set.

Valves and Air Flow

There are 4 air states; closed (CL) high pressure (HP), atmosphere out (AO) and atmosphere in (AI). High pressure goes to air tank, though I need to look at this because the exhaust may be too dirty to use directly.

There are two valves, one inside (I) the pistons, with the two outer (O) sections connected together to a single valve. The outer valves are located just past the last winding, but a gap is left beyond that with will turn into a high pressure spring if the pistons over shoot.

Atmosphere In is separate for I and O. For I, fuel is fed at a constant rate (constant with result to engine timing, but adjustable overall).

Combustion Operation

Intake

I:AI/O:AO

The windings are used to drive the pistons apart, drawing and air fuel mixture from atmosphere in.

Compression

I:CL/O:HP

The windings plus the high pressure air is used to drive the pistons together. This initiates diesel combustion.

Combustion

I:CL/O:HP

The windings are used to gather generated energy. I need to consider how this is wired. By leaving O connected to HP, we recover the pressure loss from driving the pistons and provide an air brake to prevent the pistons from slamming into the ends of the cylinder.

Exhaust

I:AO/O:CL

The outside of the piston will be at high pressure, so the windings can be used to collect energy at this stage.

Cooling?

I:HP/O:AO

This may not be necessary, but a cooling stage may help efficiency. By using I:HP, we should get a lot of cooling from the pressure drop. Also, we can use this to get two more power strokes.

Compression Ratio

This design provides a lot of control over the pressure ratio. How far the pistons are separated during intake, how much energy is put into the driving coils.

Compressor

The engine can be used as an air compressor by using the windings and disabling the fuel injector.

Inner Compression

I:HP/O:AI

Outer Compression

I:AI/O:HP

Generator

This mode uses the compressed air to generate electricity

Stroke 1

I:HP/O:AO

Stroke 2

I:AO/O:HP

Electronic Control

I'd really like it if this could be controlled by an AT-Tiny-85, 6 IO pins. I'd use one IO pin, with the ADC to choose the mode. I need to map this out, but the idea is that it's hooked up the battery it's charging and a pressure sensor and it will feed back it's mode so that if the battery is low and the tank is full, it will run as a generator, if the tank is low and the battery is full, it will run as a compressor, if both are high, it will be off and if both are low it will run as an ICE.

The rest of the pins would be used to Charlie-plex the valve solenoids.

States:

1. I:AI/O:AO
2. I:AI/O:HP
3. I:AO/O:HP
4. I:AO/O:CL
5. I:HP/O:AI
6. I:HP/O:AO
7. I:CL/O:HP

I'll need to pin this out, but I'm sure I can do it with 4, I may be able to do it with 3.

That leaves either 1 or 2 pins. It looks like the At-Tiny-85 has 2 or 3 ADCs which means I can use one of them to set the compression ratio.