Unmanned Systems Technology 003 | UAV Solutions Talon 120 | Cable harnesses | Austro Engine AE50R and AE300 | Autonomous mining | AUVSI 2015 show report | Transponders | Space systems

46 Summer 2015 | Unmanned Systems Technology Specifications Wankel-type Single rotor Effective displacement 294 cc Naturally aspirated Avgas fuel (or unleaded gasoline) Aluminium structure Nickel silicon carbide coated working surface Roller main bearing Steel eccentric shaft Steel rotor Twin plugs, single injector Engine management system Peripheral port Maximum rpm, 7750 The AE50R is naturally aspirated and peripheral ported. The charge air passes through a filter then a throttle body-cum-injector housing and then the porting, which is formed in the rotor housing. With this porting, Austro Engine’s chief operating officer Peter Lietz remarks that the aim is to create a laminar flow into the combustion chamber, ideally as smooth as possible; the action of the rotor creates more than enough turbulence. The relief in the rotor face that determines the shape of the combustion chamber was changed with the switch from carburation to port injection, and there are subtle differences between engines for different customers and their varying requirements. The throttle body-cum-injector housing is connected directly to the rotor housing, and it accepts a single injector nozzle, located just downstream of the butterfly throttle. The fuel system is non-return, with an electric pump constantly delivering fuel at a pressure of 3.5 bar to the injector. Rather than constant flow, the injector is of the solenoid type and is pulsed by the ECU. The ignition is distributorless. Two spark plugs are used, located side by side, thus each (at the same instant) igniting its side of the chamber. Each plug has its own coil that is directly operated by the ECU. As with a two-stroke, the design of the exhaust is crucial in terms of the timing of reflected pressure waves that assist charging and scavenging. In the past, there have been instances of customers going their own way on exhaust design and losing performance in the process. Lietz notes that there is also an ongoing silencer development programme, as noise minimisation is a priority for some customers. Running next to the side plate on the power take-off side (Austro Engine dubs it the ‘front housing’) is a counterbalance weight. Outside the other side (‘rear housing’) plate is the flywheel/starter ring gear, which also acts as the crank trigger wheel. Beyond that is the fan, from which air is ducted over the ring gear and into the top of the rear housing. It follows that the starter motor and cooling air filter are located on this side of the engine, as are the oil pump and the water pump. The eccentric shaft and the rotor with which it interacts are both steel. The rotor is left uncoated while the rotor housing and the side plates are cast in aluminium, machined and then coated by IPT. What is described by Lietz as “an innovative nickel silicon carbide coating” is used for the working surface, with a more routine coating for the working face of the side plates. Interestingly, the original nickel silicon carbide coating, Mahle Nikasil, was specifically designed for the original NSU Wankel rotary engine. The rotor is one piece – a new development – having previously been manufactured in two parts owing to its complexity. Rotor preparation consists only of grinding and centring its bore. Twin apex seals, running in tandem, are used. “Those tip seals are the key to engine performance,” remarks Lietz. The metal from which the apex, corner and side seals are made is undisclosed; all Lietz will say is that ceramic seals have not been embraced and that all the seals are of the same metal, and all are plain rather than coated. The seals are all pre-loaded using steel springs. Lietz adds that for the past few years all the seals have been CNC machined, increasing the accuracy of their manufacture. The seals are retained by push-in steel corner bolts. Each corner bolt contains a groove into which the apex seal seats (extending its groove), and there is a small spring washer to help locate the corner bolt. The eccentric shaft spins in a roller main bearing and in a plain bearing within the stationary gear housing. Located on the output side, the 63 mm diameter main bearing has steel rollers in a steel housing. Lietz notes that during assembly it is crucial to match the main bearing to the eccentric shaft to the rotor – all the tolerances must be correct, and Austro Engine has a selection of shafts and rotors to ensure they do all match up. The engine has a combination of through-the-rotor air cooling and Anatomy of the AE50R