Unmanned Systems Technology 002 | Scion SA-400 | Commercial UAV Show report | Vision sensors | Danielson Trident I Security and safety systems | MIRA MACE | Additive manufacturing | Marine UUVs

55 don’t want to disclose anything further until we have patented it.” In addition there is a clutch located ahead of the gearbox, on the DLC-coated propeller shaft. This is a centrifugal clutch, so it operates automatically, and it is intended only to assist starting and to help protect the powertrain in the event of a propeller strike. Danielson offers an optional variable-pitch propeller that uses either electric or hydraulic actuation and has carbon fibre composite blades. Performance Weighing 70 kg dry, the 100 TD2 comes in with an installed weight of 90 kg. Its quoted maximum crankshaft speed of 3600 rpm is a nominal figure – Hubschwerlen says the engine can tolerate a significant overspeed, to at least 4000 rpm. Hubschwerlen notes that some customers want to use a fixed-pitch propeller, and consequently need to constantly vary its speed and with that the engine speed. Others will use the optional variable-pitch propeller, allowing them to operate the engine within a more consistent rpm band. In the case of helicopter deployment, the engine can normally run at a constant speed. At low altitude the stage one (initial pressurisation) turbocharger provides only about 10% of the total charge pressure increase. However, as the air thins with rising altitude the situation changes, to the extent that at high altitude the situation is closer to 50-50. Hubschwerlen remarks that the critical altitude, at which the turbos share the work evenly and maximum power is produced, is 14,000 ft. Above that the thinning of the air saps power, to the extent that it is only 54% of maximum at the designed operational ceiling of 30,000 ft. Maximum cylinder pressure is about 160 bar; maximum torque is made at 3200 rpm, maximum power at 3600 rpm. By design, that speed corresponds to the normal required operating speed of the propeller. Torque rises steadily from 50 Nm (about 37 lb-ft) at 1300 rpm propeller speed through to its peak of 260 Nm (about 192 lb-ft). Maximum torque of 260 Nm implies a brake mean effective pressure of 29.7 bar. Power naturally echoes the torque curve, rising from just under 10 kW (10.4 bhp) at 1300 rpm propeller speed to a maximum of 75 kW (100 bhp) at 2750, a figure sustained for almost 1000 rpm. Reflecting its multi-fuel capability, the 100 TD2 can accept fuels within a wide cetane rating range. Cetane rating is on a scale of 0-100, and typically it is around 50 in the case of roadside diesel. “It runs perfectly with fuel from 36 and up,” Hubschwerlen says. “99% of fuel is above 36. If the cetane rating is below that it will just be more difficult to start the engine. The cetane rating can be as high as 70, but when it is that high there will be a marginal loss due to its burning characteristics, as we have had to design the engine for a lower rating.” With rising engine speed, specific fuel consumption in g/kW/h falls to 260 at 12 kW (16 bhp) and continues falling to a low of 230 at 35 kW (47 bhp), a figure sustained through to 45 kW (60 bhp) before climbing again, still to less than 250 at 75 kW. Overall fuel consumption is quoted as 0.38 lb (172.37 g) per bhp per hour. “That is comparable to an automotive engine using a common rail system with electronic control,” Hubschwerlen says. “Compared to a comparable current Wankel UAV engine, we cut fuel burn in half.” That emphasises why DAS has opted for CI rather than SI. Of course, SI engine manufacturers would have their own opinion but clearly there is a good case for the turbodiesel in this context. Unmanned Systems Technology | Spring 2015 Danielson was established in the mid-1970s as a motor racing team with engine and chassis engineering capability. In recent years it has concentrated on engine engineering, with race engine involvement accounting for only a small part of its turnover and no other competition activity. Its current operation embraces automotive, defence and aerospace powertrain work, and it has the capability to design, manufacture, build, test and develop engines. Its manufacturing capability includes an in-house aluminium and magnesium foundry. In recent years Danielson has become a compression-ignition specialist, reflecting the popularity of diesel over petrol cars in the French market, and the company does a lot of specialist work for the likes of Renault and Peugeot-Citroen in the roadcar sphere. It produces a number of prototype engines each year, primarily for road use although increasingly for aerospace applications. About Danielson This device stores energy during each combustion stroke and gives it back during the compression stroke, providing a very smooth drive