Avoiding the problems of the Wankel engine

The most obvious comparison is with the Wankel engine. The Libralato SMART engine is a very different design which avoids the problems of the Wankel engine:

The best Wankel engines are only about 30% efficient due to a combination of low compression ratio (about 9:1) and inefficient combustion due to the very shallow elongated combustion chamber. Wankel engines also have significant issues with overheating, seal wear, high emissions and noise.

The SMART engine can operate at much higher compression ratios due its non-contact sealing which inhibits pre-ignition and due to the architecture of its two inter-locking rotors which instantly switch from compression to expansion avoiding potential damage from detonation/ engine knock. The SMART engine combustion chamber is hemispheroid in shape which promotes complete combustion of the fuel-air mixture.

The SMART engine uses ferrous bonding, abradable thermal barrier coatings and non-contact labyrinth sealing similar to a turbine. The peripheral sealing surfaces of the rotors are large and the side surfaces have a series of grooves etched into them. At pressures of <100bar and rotational speeds of 3,000 – 10,000 rpm there is not enough time for more than a small percentage of blow-by losses. This is not detrimental since it contributes to the engine internal EGR, for ultra-low emissions. Since there is no contact of mechanical seals and no lubrication oil (apart from the sealed bearing oil circuits), the SMART engine should be exceptionally durable and low maintenance.