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

53 AIE 225CS UAV rotary | Dossier Compact SPARCS Bailey says, “Keeping the rotor and its bearings cool is the key to the longevity of the rotary engine. Everyone thinks apex seal wear is the most crucial aspect, but that problem is a thing of the past thanks to modern ceramic apex seals. If your rotor is too hot then your oil doesn’t function correctly, so your lubrication breaks down and you get substantial wear. So keeping the rotor – which is not very accessible since it is in the middle of the engine – cool is the key challenge these days.” The oil to act as lubricant is fed into the SPARCS loop under pressure from a remote reservoir. For redundancy two oil pumps are used, each doing half the work. They are electric pumps controlled by the ECU according to rpm (AIE calls this “digitally optimised lubrication”), and are submerged in the oil tank. So that they don’t have to overcome the pressurisation of the internal SPARCS cooling flow, against which the oil supply must enter the loop, the oil tank is pressurised. A line from the engine pressurises the oil tank to the same level as the engine, balancing the system. In the case of Compact SPARCS Unmanned Systems Technology | April/May 2016 The outer rotor section is also machined to form the combustion chamber reliefs and the apex and side seal grooves, including drillings to take the seal corner bolts. The three apex seals are sprung, as are the corner bolts flanking them, unlike the side seals (of which there are three on each side). Situated beyond the non-drive side shaft bearing, the combined fan, counterweight and timing wheel assembly is formed of three separate items that are bolted together as one unit. The impeller is located closest to the rotor, with the trigger wheel having perpendicular outward-facing spokes forming a basket within which the counterweight rotates. The impeller draws gas from the centre of the rotor through the adjacent endplate and centrifuges it out circumferentially through its top into a duct formed in the upper section of that same endplate. It is then ducted to the heat exchanger integrated into the top of the rotor housing and thence back through ducting in the endplate on the drive side to complete the loop. The liquid cooling circuit, into which the SPARCS heat exchanger is incorporated, is powered by an electric pump. The oil and fuel pumps are likewise electric, and are likewise controlled by the ECU, which also operates the ignition coils, the injector and the throttle. The ignition coils are mounted off the twin plugs, close to the ECU. The toothed timing wheel has a tooth missing for the sensor to use as a reference for crankshaft position using a Hall effect sensor. Other inputs to the ECU are throttle position (which it sets), oil and water temperature, oil and fuel pressure and SPARCS pressure (which it measures at a specific point). In addition, readings are taken of fuel and oil flow using turbine-type sensors. The 225CS has four mounting points on top, which are designed to carry brackets that attach to two points on the airframe. It also has two mounting points at the bottom, which are designed to attach to two points on the airframe. The engine is 274 mm high, 339 mm long (including the spark plugs) and 213 mm wide. The core engine (without ECU and with only the exhaust stub) weighs 10 kg. To strip and rebuild a 225CS takes around three hours. Some suppliers to the AIE 225CS Casting: Brooks Crownhill Patternmakers Machining: Tata Steel Advanced Machining Centre Trochoid surface coating: Poeton Throttle body: Jenvey Dynamics Injectors: Bosch Engine control unit: GEMS Seals: Precision Ceramics Bearings: INA Water pump: Bosch Oil pump: Dellorto Fluid line: Samco Fuel Pump: TCS Machine tools: Mazak Rapid Prototyping: Z Corporation CMM: Quality Control Technology CAD Software: Solidworks CAM Software: Edge Cam Dynos: Land & Sea Keeping the rotor and its bearings cool is the key to a rotary engine’s longevity. If the rotor is too hot, the oil doesn’t function correctly and you get wear