Ceramic engine with 1 moving part

A radial outflow turbine has a rotor disc with rings of angled turbine blades upon it. The case has the corresponding rings of stator blades that fit radially between the rotor blades.

The rotor disc and the other side of the case have another set of blades facing the opposite way. This acts as a turbocharger. It will take in fuel-air mixture and compress it. There are holes in the middle of the rotor that let the compressed fuel pass to the combustion chamber where it is ignited. It will be ignited by the temperature of the combustion chamber and the compression of the turbocharger when the engine is hot. It may need a spark when starting from cold.

The turbine will be most efficient when running very hot at constant high speeds. If I was building one, I would make the first prototype out of inconel, like they used in early turbofans, but I would like the final thing to use kaolin, because of its high temperature and self-repair properties. People have tried making composite engines out of metal + ceramic but this leads to problems where the metal meets the ceramic. The solution would seem to be to make the whole of the high-temperature bit in one piece out of ceramic. The shapes of the rotor and stator plates allow them to be moulded. Anyone who has done china clay pottery knows you have to have a special oven, but otherwise it can use many of the same techniques as ordinary pottery.

The engine turns much too fast for a conventional gearbox. The solution would be to generate electric power, and use that to drive the wheels, propellor, or whatever, as for diesel-electric vehicles. You can get 'pancake' generators that double as motors, which will be needed to start the thing up.

The motor shaft can use a gap of (say) 50 microns to act as an air bearing. I got this figure from scaling down the corresponding gap in a turbofan engine, which is typically under 1mm. This tolerance seems possible with moulding without re-machining. The leak from each side can leak to the outer, unpressurised ring on both the turbocharger side and the engine side. We may be able to do some electric suspension from the generator side to get the system started.

Okay so far? We have air and fuel being compressed as it moves inward. At the centre, we will run at typical turbofan temperatures of 1700C. The inconel prototype would not stand this for long but kaolinite would. As the fuel ignites and rushes outward, the expansion powers the turbine. The turbine can have a compression ratio of 10:1 just because of the increasing radius. It can be increased further if the turbine blades get longer at the outside. The electric power generated is then converted to motive power. We take the power management from a conventional diesel electric system or a hybrid car. We get rid of the cooling water, the radiator, the clutch, the gearbox, and the lubrication system. And the engine has one moving part.

The engine as described should be more efficient than conventional internal combustion when running at a constant load. Short-term energy budgeting can be done by the drive electronics: you use extra power for starting and get it back when breaking. For longer-term power management, you may have several separate engine units, and use one when the vehicle is unladen, and three or four when it is pulling a heavy load.