The relative humidity on airplanes is purposely kept low—frequently below 20%—to prevent condensation from building up in the cabin and on the fuselage. Now, a vortex ring generator developed by the Fraunhofer Institute for Building Physics (IBP) will direct humidified air to passengers. The device may boost their comfort without causing cabin humidity to increase appreciably.

The generator produces small vortex rings of humid air, like the rings sometimes expelled by smokers. The vortex effect keeps the rings stable over a specific distance while it prevents them from mixing too much with the surrounding air.

Plans are to integrate the generator into the back of airplane seats. Image credit: Pixabay.The device resembles an air pump, with pistons driven by a linear motor. Initial tests have paired the prototype with a dummy equipped with an artificial nose that draws in and analyzes the air. This helps the researchers pin down the system’s basic settings, such as the size of the rings and the pace and rate at which they are expelled.

The generator is designed so that the vortex rings make contact with the passengers’ upper torso; body heat then causes them to rise toward the nose and mouth. Since the chest area is typically covered by clothing, it is less sensitive than the face would be to the light airflow. The aim is to double the air humidity in the breathing zone from 15% to around 30%.

In addition to humidified air, Fraunhofer says an additional application could be to use vortex rings to channel fragrances increasingly used in ventilation systems. However, because this could also reach people with allergies, it would have to be in minimal doses and only at the request of the passenger.

According to Thomas Kirmayr, group manager at Fraunhofer IBP, current plans are to integrate the generator into the back of seats. "However, the certification process in the aviation industry is extremely long, and it will be some time before the system is employed in aircraft,” he says.