Tobias Dehne

Flight Testing of Alternative Ventilation Systems for Aircraft Cabins

Cabin displacement ventilation (CDV) has been evaluated for the first time in a real passenger aircraft cabin under flight conditions. Two ventilation systems, i.e. pure CDV and a hybrid ventilation (HV) system, which provides 30 % of the total volume flow rate through the lateral mixing ventilation outlets, were tested in an A320 aircraft. While pure CDV was found to provide low air velocities, high heat removal efficiencies and a very good dynamic performance regarding control of the air temperatures, the hybrid system, still allowing for comfortable flow velocities and good heat removal efficiencies, was shown to significantly improve the cooling and heating rates at the cabin surfaces. With both systems, the local temperature in the passenger zone is distributed very homogeneously among the investigated seat and aisle positions.

Transient temperature fields of turbulent mixed convection in an aircraft cabin caused by a local heat source

The impact of a localized, transient head load on the temperature fields in aircraft cabin air flows was investigated in the Do 728 test bed of the German Aerospace Center. Surface and fluid temperatures were analyzed using more than 340 local sensors as well as a grid of polystyrene spheres, which was imaged by an infrared camera. To simulate the impact of the real passengers, thermal passenger dummies were used. The spatial spreading of the heat released by the local source could be characterized for the state of the art mixing ventilation system (MV—mixing ventilation) and a novel ventilation system (CCDV—ceiling based cabin displacement ventilation), which provides fresh air at low momentum through the cabin ceiling. As expected, CCDV provides lower cabin temperatures due to its higher heat removal efficiency. While MV tends to accumulate the heat released by the local source in the passenger zone, warm air is able to ascend to the ceiling more easy at CCDV due to the lower inertia forces. The different amount of inertia forces in the flow between MV and CCDV has a measureable impact on the temporal behavior of the resulting flow patterns during operation of the heat source, which is well reflected in the fluctuations of the temperature elevations.

In-Flight Infrared Thermography for Studies of Aircraft Cabin Ventilation

To improve the convenience of aircraft cabins, Cabin Displacement Ventilation (CDV) was investigated during flight tests in an Airbus A320 with an automatically rotatable infrared camera. For this purpose a programmable, step motor driven infrared camera setup was developed, allowing for time resolved acquisition of the temperatures on the interior cabin surfaces during the whole flights. From the temporal development of the surface temperatures the cooling and heating performance of pure CDV as well as a hybrid system (HV), where 30 % of the fresh air was supplied through the original lateral outlets, was analyzed and characterized. Static measurements reveal a characteristic, yet homogeneous temperature distribution in the cabin for both scenarios, pinpointing to a homogeneous cooling of the heat loads in the whole cabin. In order to study the performance of CDV and HV, dedicated “pull-up” and “pull-down” scenarios, those are abrupt changes of the inflow temperature with the objective to study the heating and cooling dynamics, were conducted during the flight tests. Analysis of time resolved measurements discloses that the cooling performance of the cabin is limited by thermal diffusion of heat inside of the interior cabin materials.