04-10-2017, 11:29 AM
High power density, low weight, compact dimensions, high efficiency and reliability are key factors in the design and dimensioning of piston engines for general aviation and UAVs. Despite the new technologies available, conventional solutions still struggle to meet all these requirements simultaneously. The new concept basically consists of using a patented rotary valve to control flow through a set of input ports, allowing supercharging and achieving extremely high power densities compared to conventional solutions. The sweeping is performed using an external pump, constituted by an additional cylinder, whose piston is connected to the same crank. The piston pump allows the crankcase to be used as a conventional oil manifold, and greatly improves the crank balance. Valves or camshafts must not be installed, as the flow is driven by piston controlled ports and by two sets of blade valves. The engine can adopt two types of combustion system: Direct Fuel Injection (GDI) for SI operations, and Common Rail direct injection cycle for diesel.
The application of the 2-stroke diesel concept to aircraft engines is anything but a novelty: as a single example, Junkers built a very successful series of these engines in the late 19-30, called JUMO. The main advantage of an engine of this type is fuel efficiency; even in 1938, the JUMO engine was capable of a specific consumption of fuel brakes of 213 g / kWh, an impressive figure even by modern standards. It should be noted that fuel consumption is very important for the performance of the aircraft, since a significant portion of the total weight of the aircraft (sometimes up to 50%) is due to fuel storage. The main reason for the excellent fuel economy of 2-stroke diesel engines is the high mechanical efficiency resulting from the 2-cycle cycle; in addition to the possibility of having no valves and associated drive system, mechanical friction losses over the cycle are reduced by half compared to a four stroke engine having the same crank and piston and crankcase design thanks to the double cycle frequency. Another interesting feature of the two-stroke cycle is the high power density at low crankshaft speed, allowing the designer to connect the engine to the propeller without a reduction drive (which is cumbersome and costly, and penalizes fuel economy) .
The application of the 2-stroke diesel concept to aircraft engines is anything but a novelty: as a single example, Junkers built a very successful series of these engines in the late 19-30, called JUMO. The main advantage of an engine of this type is fuel efficiency; even in 1938, the JUMO engine was capable of a specific consumption of fuel brakes of 213 g / kWh, an impressive figure even by modern standards. It should be noted that fuel consumption is very important for the performance of the aircraft, since a significant portion of the total weight of the aircraft (sometimes up to 50%) is due to fuel storage. The main reason for the excellent fuel economy of 2-stroke diesel engines is the high mechanical efficiency resulting from the 2-cycle cycle; in addition to the possibility of having no valves and associated drive system, mechanical friction losses over the cycle are reduced by half compared to a four stroke engine having the same crank and piston and crankcase design thanks to the double cycle frequency. Another interesting feature of the two-stroke cycle is the high power density at low crankshaft speed, allowing the designer to connect the engine to the propeller without a reduction drive (which is cumbersome and costly, and penalizes fuel economy) .