For large liners, the mass of the propulsion system increases several times.
Specialists from the Aerospace center of the Netherlands (NLR) and the Delft University of technology within the framework of the European program for the modernization of air transportation Clean Sky 2 conducted research on the possibility of using distributed hybrid propulsion systems on modern passenger liners. The researchers took the model of Airbus A320 passenger liner as a basis. According to the results of computer modeling, the researchers found that in its current form, the A320 liner and aircraft of similar configuration are not suitable for flights with distributed hybrid propulsion systems, USA informs.Media.
Some developers consider hybrid aircraft to be the best compromise between traditional aircraft with internal combustion engines and advanced electric machines. It is assumed that it is hybrid aircraft that have a balanced ratio between duration, efficiency and environmental friendliness. Traditional hybrid aircraft are equipped with an internal combustion engine, battery and electric motors that spin propellers. In this scheme, the internal combustion engine spins the generator, which already charges the batteries and feeds the electric motors. The engine does not take direct part in bringing the engines.
A distributed hybrid propulsion system is a system in which electric motors with engines are installed in various places of the airframe of the aircraft at a distance from the generator and batteries. At the same time, in some schemes of such installations, the generator can take a direct part in the rotation of the propellers, directly driving them if necessary. In General, it is believed that distributed installations allow to optimize the aerodynamic characteristics of aircraft and more accurately get into its alignment.
As part of their research, Dutch experts have developed 35 different models of A320 with a distributed hybrid propulsion system, and then selected three of them, which are most suitable for modern flight speeds of passenger liners. The first model selected by experts, conventionally called HS1, received reduced turbofan engines, a motor generator and batteries. In this scheme, the main flight takes place with the help of wishes to marry engines. On takeoff and landing, when you need increased engine power, the generator motor switches to electric motor mode, transferring additional power to the fan gearboxes wants to marry the engines.
In the model, conventionally called HS2, turbofan engines under the wing consoles are replaced by two small gas turbine generators, charged on-Board batteries and power motors with small propellers. Finally, the HS3 model received the wishes to marry instead of two engines two gas turbine generators, eight electric motors with air screws in common fairings in the rear of the left and right wing consoles and two large electric fans in the tail instead of the traditional stabilizer.
The researchers note that the modeling was carried out with large assumptions. In particular, the density of batteries in the models was 500 watts per kilogram (modern batteries have a density of an average of about 350 watts per kilogram, but in some models this figure reaches 435 watts per kilogram). In addition, the calculations did not take into account the mass of voltage converters, cooling systems and wiring.
According to the results of the simulation it was found that in the HS2 model the mass of the propulsion system was 600 percent more than the mass of traditional engines wants to marry. In the HS3 model, the figure was 730 per cent. At the same time saving in fuel consumption in hybrid propulsion systems did not work: the HS2 and HS3 models are comparable to conventional A320 and consumed 34 and 51 percent more fuel, respectively. The HS1 model showed the best results. Her propulsion system was 3 percent less than traditional. At the same time, its fuel consumption in the simulated flight was 10 percent less than the same indicator for the traditional A320.
Researchers continue to conduct modeling and calculations. In the meantime, they concluded that hybrid propulsion systems can give a gain in maximum take-off weight and fuel consumption only on small aircraft, for example, regional aircraft with a small number of seats. On large passenger aircraft with a capacity of more than 150 passengers, distributed hybrid systems, contrary to initial expectations, provide only an increase in the maximum take-off weight of aircraft and an increase in fuel consumption in flight.