The internal combustion engine is notoriously inefficient. Petrol engines have an efficiency of 20-25% and diesel 30-40%. They rely on intermittent explosion of the fuel/air mixture to produce mechanical energy. The major product is not transportation energy but hot water that has to be dissipated by the radiator. The convector generator may be adapted or miniaturised to produce a car engine with an efficiency that could be over 80%. At its simplest:
Combustion of fuel draws its own air. The rising combustion gases drive the rotational mechanism. The energy is conveyed to the axle which rotates the wheels. The exhaust gases would need to be dissipated at a level above the engine into the atmosphere. Combustion would be continuous, not by explosion, so it should mean less oxides of nitrogen in the exhaust.
An improvement would be to use multistage combustion and to harness energy also from incoming air. Successive layers of combustion may reduce the amount of carbon monoxide and unburnt hydrocarbons in the exhaust gases:
The cylindrical assembly depicted would be of about 10-30 cm diameter. Heat energy in the exhaust gases could be used to warm incoming air or to evaporate the fuel. Alternatively a heat exchanger could be incorporated.
If the combustion chamber was designed to allow a large excess of incoming air then the combustion gases would leave at below 500° C. These would rotate the convector generator and then surrender most of their residual energy to the incoming air in the heat exchanger. The exhaust gas would leave at 100° C. If well insulated, such an engine should achieve a heat to mechanical energy efficiency of over 80%. The rotational mechanism should have a high moment of inertia and convey rotation directly to the axle.
A radically different engine design that again depends simply on rising combustion gases causing rotation is shown below.
In the cross-section above the central rotating arms will be linked to an axle to convey rotational energy to the wheels. As the fuel burns, combustion gases rise inducing rotation of the asymmetrical arms in an anti clockwise direction. Fresh air is drawn in from the bottom – it will be pre-heated by the asymmetrical arms as it enters the combustion chamber.
There could be several layers (3 to 20) of such rotational arms to allow effective energy transfer from the rising hot gases to the rotating mechanism and from the latter to pre-heat the incoming air. If there is an abundant air supply, the central temperature could be below 500° C but will fall as we pass to outer layers ideally at 100° C. If such a design were achievable it would mean a rotary engine of over 80% efficiency.