Unmanned Systems Technology 007 | UMEX 2016 report | Navya ARMA | Launch & recovery systems | AIE 225CS | AUVs | Electric motors | Lethal autonomous weapons

57 AIE 225CS UAV rotary | Dossier cost-effective – and straightforward in operation,” remarks Bailey. “What we are trying to do with the pocket is prevent gas being trapped at the back of the combustion chamber, since that causes detonation. The pocket must be extended a certain amount to the rear. I have seen dual pockets that have been a response to a detonation problem, trying to release trapped gas from the back, but it is better to use a longer single pocket from the outset.” The rotor housing locates the intake port above the exhaust port, both situated on what we can consider to be the front of the engine, the spark plugs being on the rear. Flanked by the endplates, these three items are tied together by a ring of through-bolts, with reduced pitch between adjacent fasteners on the side subject to higher combustion pressure. Additional bolts run through the top of the structure above the heat exchanger, which is integrated into the rotor housing. Gas sealing between the rotor housing axial face and adjacent endplate is augmented by means of a sealant. The area where the side seals slide against the endplate inner wall is DLC coated. Coolant flows through the endplates and the rotor housing, and around the outer periphery of the CS heat exchanger in a single loop; the external coolant pump is driven electrically. Bailey notes that this coolant system was designed with the assistance of a CFD study. Currently the 225CS is supplied with an open exhaust. AIE is working on silencing technology for it, although Bailey notes that propeller noise is typically more dominant than engine noise in UAV applications. The 225CS has peripheral porting, which implies fixed timing, and Bailey notes that the porting is designed for high power, with the induction air having a straight run through the throttle body and thence into the chamber. The throttle body locates the single injector nozzle downstream of the butterfly, the injector itself being mounted at a shallow angle with respect to the port. Unmanned Systems Technology | April/May 2016 AIE notes that rotary engines have many advantages for range extender and series hybrid vehicle use, including small form factor, low weight, low vibration and high power density. However, historically the use of rotary engines in such applications has been limited because of the rotary’s inherently high exhaust energy, heat and emissions (particularly at low rpm and part throttle). CREEV (Compound Rotary Engine for Electric Vehicles) addresses these issues. The CREEV system follows the principle of compound steam engines of the past, by using a secondary rotor specifically to extract energy from the exhaust stream via controlled expansion of it. The shaft power it thus creates is added mechanically to the output of the eccentric shaft, resulting in around a 20% increase in overall output, according to AIE’s initial tests. By expanding exhaust gas to near atmospheric pressure, CREEV also results in a cooler and quieter exhaust emission. The system further acts as what AIE terms an “exhaust reactor” by continuing to consume unburnt exhaust products while expansion occurs in the secondary rotor stage, thus reducing overall emissions of CO 2 and NOx. CREEV Balancing the 225CS’ rotor AIE is working on silencing technology for the engine, although Bailey notes that propeller noise is typically more dominant than engine noise