Various Airflow Distribution For Commercial Aircraft Cabins

Current commercial airplanes supply low-temperature air with high momentum from the ceiling diffuser and extract contaminated air at the floor exhaust in attempting to dilute the internally generated pollutants by promoting air mixing. Such mixing air system is widely criticized both in perspectives of air quality and thermal comfort. More critically, the highly mixing context may spawn airborne disease communication and thus airliner cabin environment deserves more concerns. Although many researchers tried various efforts to improve the cabin environment, the investigation shows that most passengers and air crews are still not satisfied. A healthier, more comfortable and efficient air distribution system is extremely needed. This thesis is intent to develop an under-aisle displacement air distribution system and a personal chair-armrest-embedded air system to improve the current airliner cabin environment. As a comparison, the mixing air distribution system was studied first.The proposed under-aisle air system supplies conditioned air (about 22℃) from the under-aisle perforated panels and extracts the contaminated air from the ceiling exhaust. While, the personalized system supplies the outside, warm conditioned air (about 25℃) from the rectangular chair-armrest-embedded diffuser but still keeping the under-aisle air system as the background ventilation. To evaluate the proposed air systems, a double-aisle aircraft cabin mockup containing 49 passenger seats in seven rows is constructed. The cabin mockup was designed to mimic an economy section of a Boeing 767 airplane, where inside totally 35 simplified thermal manikins that hold realistic geometric body profiles are seated. A three-dimensional ultrasonic anemometer is employed to measure the airflow and temperature distribution in a cross section and the mid-longitudinal section of the aircraft. The ventilation efficiency of the air system together with the mixing extent of the inside air is evaluated by measuring the concentration of carbon dioxide (CO2), after it is introduced to the exhalation point of the middle passenger. In addition, a computational fluid dynamics (CFD) program with the RNG k-s model is applied to simulate the air environment after the numerical program is validated against the measurement data. Finally, the personal air system is optimized by comparing different personalized air directions, flow rates, humidification amounts, and the recirculated under-aisle air supply rates using CFD.It finds that the RNG k-s model is able to provide simulated results in reasonable agreement with the experiment data. The airflow is the strongest in the mixing air system and the weakest in the under-aisle air system. The under-aisle air system has lower inhaled CO2 concentration than the mixing air system, so the ventilation is more efficient. Though there is temperature stratification in the under-aisle system, the analysis shows that it is unlikely to impose draught risk once the air supply temperature is greater than 22℃. The personalized air system can reduce the mixing extent of air since the under-aisle air system is used as the background ventilation. The personal system can maintain the breathing region at least 30% lower of pollutant concentration as compared with the mixing air system. After performance optimization, it concludes that the personalized air shall be supplied upwards in 20°-50°from the horizontal, using a proper rate of 3-4 L/s per person. The relative humidity can be increased to 18 to 30% and the under-aisle air recirculated rate shall be maintained no less than 8L/s per person. With the generally good performance, the personal chair-armrest-embedded air system is therefore recommended for future potential use on commercial airplanes.