2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Some options for installing a distributed hybrid propulsion system on the A320, including with a change in the airframe of the aircraft
Experts from the Netherlands Aerospace Center (NLR) and the Delft University of Technology, as part of the Clean Sky 2 pan-European air transport modernization program, have investigated the possibility of using distributed hybrid propulsion systems on modern passenger liners. According to Aviation Week, the researchers took the model of the Airbus A320 passenger airliner as a basis. Based on the results of computer simulations, the researchers found that in its current form the A320 liner and aircraft of this configuration are unsuitable for flights with distributed hybrid propulsion systems.
Hybrid aircraft are considered by some developers to be the best compromise between traditional combustion engine aircraft and future electric vehicles. It is assumed that it is the hybrid aircraft that have a balanced balance between durability, efficiency and environmental friendliness. Traditional hybrid aircraft are powered by an internal combustion engine, battery, and electric motors that spin the propellers. In such a scheme, the internal combustion engine spins the generator, which already recharges the batteries and powers the electric motors. The engine does not directly participate in bringing the propellers.
A distributed hybrid propulsion system is a system in which electric motors with propellers are installed in different places on the airframe of the aircraft, away from the generator and batteries. Moreover, 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 make it possible to optimize the aerodynamic characteristics of aircraft and more accurately get into its centering.
As part of their research, the Dutch specialists developed 35 different A320 models with a distributed hybrid propulsion system, after which they selected three of them that are most suitable for modern flight speeds of passenger liners. The first model selected by experts, tentatively called the HS1, received smaller turbofan engines, a motor generator and batteries. In this scheme, the main flight is carried out using turbofan engines. During takeoff and landing, when increased engine power is required, the motor-generator switches to electric motor mode, transferring additional power to the fan gearboxes of turbofan engines.
In the model, provisionally called the HS2, the turbofan engines under the wing consoles are replaced by two small gas turbine generators that charge the onboard batteries and power the electric motors with small propellers. The latter are installed in five on the leading edges of the left and right wing consoles. Finally, the HS3 model received two gas turbine generators instead of two turbofan engines, eight electric motors each with propellers in common fairings at the rear of the left and right wing consoles, and two large electric fans in the tail section instead of the traditional stabilizer.
The researchers note that the modeling was carried out with large assumptions. In particular, the density of rechargeable batteries in the models was 500 watts per kilogram (modern batteries have an average density 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 weight of the voltage converters, cooling system and wiring.
Simulations revealed that the HS2 had a propulsion system weighing 600 percent more than conventional turbofan engines. For the HS3, this figure was 730 percent. At the same time, the hybrid propulsion systems did not save in fuel consumption: in the HS2 and HS3 models, they consumed 34 and 51 percent more fuel compared to the conventional A320, respectively. The HS1 has shown the best results. Its propulsion system turned out to be 3 percent less than the traditional one. At the same time, its fuel consumption in a simulated flight turned out to be 10 percent less than that of a traditional A320.
Researchers continue to conduct simulations and calculations. In the meantime, they have come to the conclusion that hybrid propulsion systems can only give a gain in maximum takeoff weight and fuel consumption 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 installations, contrary to initial expectations, only give an increase in the maximum take-off weight of aircraft and an increase in fuel consumption in flight.
Earlier it became known that the European helicopter holding Airbus Helicopters will begin flight tests of the promising high-speed rotorcraft RACER (Rapid and Cost-Effective Rotorcraft, fast and cost-effective rotorcraft) in 2020. The first prototype, which is also being developed as part of the Clean Sky 2 program, will be powered by a hybrid powertrain from the French company Safran, consisting of two turboshaft engines and one auxiliary electric motor. It is assumed that during cruise flight, one of the helicopter's two turboshaft engines will be turned off. If necessary, for example, when landing, the electric motor will quickly spin up the stopped engine until it starts and runs at operating speed.
During takeoff, landing and emergency operation, the electric motor will transfer some of the power to the rotor shaft, reducing the load on the engines. It is assumed that the new helicopter in flight will consume less fuel of modern machines comparable in take-off weight and passenger capacity.