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

55 Continental Motors CD-155 I4 turbodiesel | Dossier monobloc is a very sturdy approach, and this solution was initially adopted for the CD-135 and 155. However, the only major change to the specification of those engines since certification has been the removal of bedplate in favour of individual main caps and a separate windage tray. Where the bedplate extended under the side walls of the monobloc, and thus formed the base of the main structure, the separate windage tray fits only within the width of the crankcase. However, it still has half-a-dozen fasteners tying it to the bottom of the monobloc, and it incorporates three transverse strengthening ribs between those attachment points. The main caps are now individual steel ones. Aside from the two outer ones, these are now side-bolted into the monobloc. Thus each cap has two vertical bolts in the normal manner, while the three inner ones also have two horizontal bolts, one on each side. This change significantly increased the strength of the bottom end of the engine. As such, it also increased the time between replacement (TBR) from 1200 hours for the CD-155 and 1500 hours for the CD-135 to 2100 hours for both. The heart of the matter The in-house manufactured exhaust cleverly sees the four-into-one exhaust primary pipe integrate at its end the turbocharger turbine housing, saving weight and space. The wastegate is integral with the turbine housing and contains a flap that opens progressively to bypass exhaust gases as necessary from the turbine wheel. Wastegate control is closed-loop and manages plenum pressure to a maximum of 2.25 bar absolute. At ground level, charge air temperature is typically about 160 C at the exit from the compressor, and the target is to reduce it to less than 50 C at the plenum. The air-to-air charge cooler is located close to the engine, its actual position being application-specific. Since the engine is turbo- supercharged, the plenum is a straightforward envelope bolted to the side of the cylinder head at the intake port face. It has a tubular entrance for the charge air from the compressor and an exit for each cylinder; the intake porting is bifurcated within the head. The cylinder head has each fuel injector centrally positioned with a glow plug offset to the intake side. There is a low- Unmanned Systems Technology | October/November 2017 Pressurised lubricant is also sent to the cylinder head, from which there is a gravity return to the crankcase. In addition, the main gallery supplies a single oil spray jet to the underside of each piston, for cooling purposes. Oil is also sent to the turbocharger bearing housing for lubrication and cooling. The single turbocharger’s shaft runs in plain bearings. The use of an exhaust silencer, if any, is customer-dependent. Blow-by exiting the crankcase passes through a centrifugal oil-air separator, from which the oil is sent back to the wet sump. Oil pressure is 1.0 bar at idle, rising to a maximum of 6.0 bar under normal operation. The firing order is 1-3-4-2. The gearbox is attached to the front of the monobloc via an intermediate aluminium flange that incorporates one of the engine mounts. Its housing is a low-pressure aluminium sand casting that is machined in-house. It has steel gears and its own oil reservoir to ensure lubrication. Propeller pitch is set by an electronically controlled hydraulic governor incorporated into the gearbox housing. Gearbox oil is used by this system, and an increase in blade pitch is obtained through an increase in oil pressure. The FADEC controls the governor-set oil pressure through an electronic pulse valve. The CD-155 is 778 mm wide, 636 mm high and 816 mm long. The dry base engine weighs 92.9 kg, with a typical installation, including turbocharger and plenum, FADEC and wiring, starter motor, alternator, transmission, oil lines, engine mounts, radiators, ducts, fluids and propeller – in other words the complete power unit package – weighing 205.6 kg. CAD rendering of the CD-155