Unmanned Systems Technology 016 | Hydromea Vertex AUV | Power management systems | Unmanned Space Vehicles | Continental CD-155 turbodiesel | Swift 020 UAV | ECUs | DSEI 2017 Show report

59 Continental Motors CD-155 I4 turbodiesel | Dossier dual-mass flywheel is bolted to the end of the crankshaft, while the outer side has a female spline to accept the gearbox input shaft. The two sides are connected by a pair of long springs that permit a certain amount of radial displacement (relative to the crankshaft axis). Thus is resolved the conflict between, on one side, the harsh torque spikes inherent in diesel engine operation (which sees cylinder pressure go as high as 180 bar), and on the other side the high inertia associated with the propeller. Moreover, the dual-mass flywheel protects the engine from damage in the event of a prop strike. The propeller is driven at a fixed ratio of 1:1.69 (such that a 3890 rpm crankshaft speed equates to a 2300 rpm propeller speed) by a gearbox that contains just three gears. The first is driven by the input shaft from the dual- mass flywheel, the second is a small intermediate idler while the third powers the output shaft, to which the propeller is directly attached. This arrangement puts the short propeller shaft at camshaft rather than crankshaft height. For use in an unmanned craft there is a version of the gearbox that has an additional power output shaft, driven by the idler gear. This is to drive a generator since the standard alternator cannot cope with the electrical requirements of a large (about 17 m wingspan) UAV or comparable rotor craft with high power demand payload. The generator provision is application-specific. As standard, the CD-155 is used in a tractor configuration, as per a conventional light aircraft. However, it is recognised that a pusher variant will extend potential UAV applications, so that is under development. The only major change is the angle of the helical gears in the gearbox. The standard helical angle creates a directional force that counteracts the force in the other direction caused by propeller operation, to the benefit of the propeller shaft bearings. If the engine is switched so as to have the propeller at the back, the ‘pushing’ force created by the helical angle will be reinforced by the pushing force of the propeller instead of acting counter to it. Performance While maximum plenum pressure is 2.35 bar absolute, cruise charge pressure is typically 1.93 bar absolute. The engine has 3890 rpm crankshaft as the take- off/maximum continuous power speed, with 3380 rpm as typical cruising power speed. Given the former, the output is 114 kW (155 hp DIN); given the latter it is 70 kW, with respective fuel consumption of 32.1 and 18.5 l/h. At 3890 rpm the crankshaft provides 280 Nm of torque, the propeller 473 Nm. The CD-155 runs for 100 hours before servicing is required; that is the interval at which the oil should be changed. At the 2100-hour TBR the engine will actually be replaced rather than overhauled. Mundt points out that rival engine overhauls often replace almost everything except the plate with the engine’s serial number. In replacing the entire engine, Technify will recycle many of the components (if only as scrap metal) so this approach is not as wasteful as it sounds. The CD-155 is certified to run with automotive diesel fuel and a range of aviation jet fuels. Having been designed to run purely on diesel, no compromise of the 18:1 compression ratio was necessary for it to accept jet fuel. It was necessary only to specify alternative injectors and modify the high- and low- pressure mechanical fuel pumps using some alternative materials and Unmanned Systems Technology | October/November 2017 The CD-155’s exhaust primary with integral turbine housing CD-155 thinwall sump