New Life for the Rotary Engine

Mazda has applied for a patent covering a direct fuel injection rotary (Wankel) engine. The rotary engine has some intriguing properties, it can produce good horsepower from a very small size and it is exceptionally smooth (based on it's rotary motion that doesn't involve the violent 'starting and stopping' motions of the connecting rods in a piston engine).

Number 15 is the direct fuel injector.

For grins, here's an animation of the rotary in motion.



It has two significant drawbacks though. One is it's difficulty in 'sealing' the rotors and the second is it's dicey pollution characteristics/fuel economy. The second problem has to do with the shape of the combustion chamber, a wide shallow space that's moving, that is difficult to do a complete burn of the fuel in. That is one reason each rotor chamber has two spark plugs, one leading ignition pulse and one trailing pulse.

The direct injection could reduce the impact of that problem by keeping the cloud of fuel very close to the ignition source (rather than having it dispersed throughout the elongated combustion chamber as has been the case until now). But it appears that they are injecting fuel before compression, which still leaves a fuel/air mixture to occupy the hard to reach edges of the combustion chamber (hard for the flame front to reach that is). Regardless, fuel economy will improve.

Hat tip to MotorAuthority.