Rotary Unions

Today Rotary Unions have come into their own, rotary unions are being commercially manufactured which are capable of containing pressures of 10,000 psi and rotational speeds of up to 20,000 rpm. just a few years ago the maximum rotational speeds for rotary unions sealing in air or other gases was a few hundred rpm! Further, apart from this a very simple modification to the rotary union can assure the RPJ of an air-tight seal at virtually any rpm and a long service time before it is replaced. Below is another diagram of a rotary union with two channels.

The Rotary Pulse Jet engine utilises just such a rotary union so that fuel can be injected into the compressed air stream at the appropriate moment. Thus the fuel line and the compressed air lines are kept separate until they enter the channel in the rotor leading to the combustion chambers. The combustion chambers are sealed by a poppet valve that can be operated by a solenoid or mechanically, the poppet valve stem is sealed by an 'o' ring. 'O' rings are used in the space shuttle and are capable of resisting high pressure and temperatures. The rotary union connects directly into the main shaft of the Rotary Pulse Jet Engine, while the shaft rotates the rotary union and the fuel line and compressed air line that are attached to it remain stationary. Thus the combustion chamber is absolutely air-tight, there are no leaks, the combustion chamber has only two openings, one to allow air inside via a poppet valve and the other to release the hot gases of combustion through the CDN valve.  The piezoelectric spark plug is  easy to seal.

Further by using a slightly more complicated design it might be possible to actually provide a flow of water through a rotary union to cool the engine, but air cooling should be more than sufficient, since the whole engine rotates and it works intermittently. If water cooling of the engine is an option, compression ignition might be implemented. See the section on cooling of the engine.