Multilevel plate-type acoustic metamaterials with level-to-level modal antiresonance for sound insulation

With the goal of engineering applications, the scalability of the plate-type acoustic metamaterials (PAMs) is significant. However, most of the designed large-scale PAMs are formed by extending a single PAM cell to an array of cells, which will inevitably introduce the vibroacoustic behavior of the entire array structure, resulting in the decay of the sound transmission loss (STL) performance in certain frequency bands. To overcome this weakness, we present a new conceptual design of multilevel PAM to enhance STL performance again by considering level-to-level modal antiresonance. The modal antiresonance of the second-level PAM, which manifests itself as the coupling through out-of-plane vibration of the first- and second-level PAMs, is analyzed to reveal the physical mechanisms. In addition, we also find that the STL profile of the second-level PAM has different dependence on the masses placed on the PAM cell and PAM array. We theoretically design and experimentally demonstrate the sound insulation properties of the proposed second-level PAM. Since the configuration of the multilevel PAM can be easily and flexibly designed in accordance with actual application requirements, it has broad application prospects including but not limiting to submarine shells, aircraft cabins, transformer rooms.

Design concept of onboard air purification system for commercial aircraft

The purpose of the article is to discuss methods of air disinfection in passenger aircraft cabins during flight. In the course of the study, a comparative analysis of modern methods of cleaning and disinfecting air in closed rooms was carried out. The efficiency, mass characteristics and energy consumption of UV sources are compared. The use of photocatalytic filters based on the phenomenon of oxidation of organic substances under the influence of sunlight in the presence of a catalyst is proposed. As a result, the authors compare the efficiency of disinfection and energy consumption when using various methods of air purification. In addition, the authors draw conclusions about the prospects of the proposed method of air disinfection using photocatalytic filters in relation to the cabins of passenger aircrafts. The schemes of rational placement of UV sources are proposed, which allow obtaining the maximum efficiency of air disinfection.

Ultrafine particle levels measured on board short-haul commercial passenger jet aircraft

Background Airline crew members report adverse health effects during and after inhalation exposure to engine oil fumes sourced to the air supply system onboard commercial and military aircraft. Most investigations into the causal factors of their reported symptoms focus on specific chemical contaminants in the fumes. The adverse health effects reported in aircrew exposed to the aircraft air supply, bled unfiltered off the engine or Auxiliary Power Unit (APU) may be related to particulate exposures, which are widely known to effect health. While oil contaminates the aircraft air supply, some suggest that this will only occur when there is a bearing seal failure, others document that there is low level oil contamination of the air supply during normal engine operation. This brief pilot study explores whether particulate exposure may be associated with the normal engine/APU and air supply operation and to therefore increase the understanding that UFP exposures may have on crew and passengers. Methods An ultrafine particle counter was utilised by an experienced airline captain in the passenger cabin of four short-haul commercial passenger aircraft. All flights were under 90 min on aircraft from two different carriers ranging from 7 months to 14 years old. Results UFP concentrations showed maximum concentrations ranging from 31,300 to 97,800 particles/cm3 when APU was selected on as a source of air on the ground and with engine bleed air and the air conditioning packs selected on during the climb. In 2 of the 4 flights the peaks were associated with an engine oil smell. Increases in UFP particle concentrations occurred with changes in engine/APU power and air supply configuration changes. Conclusions This study identified increases in UFP concentrations associated with engine and APU power changes and changes in air supply configuration. These results correlated with times when engine and APU oil seals are known to be less effective, enabling oil leakage to occur. The concentrations reached in the passenger cabins exceeded those taken in other ground-based environments. UFP exposures in aircraft cabins during normal flight indicates there will be health consequences for long serving aircrew and some passengers.

Effect of Personal Space Invasion on Passenger Comfort and Comfort Design of an Aircraft Cabin

Passenger comfort is becoming an important issue with the recent increase in air travel. A common cause of passenger discomfort and distress is the invasion of the passenger’s personal space. This paper presents the results of two studies addressing the environmental psychological characteristics of passengers during personal space invasion (PSI) and how PSI affects cabin comfort design. In study 1, our survey shows that PSI has different effects on the comfort of passengers with different genders, ages, education levels, and interpersonal relationships. From these survey data, we extracted 14 factors of PSI. In study 2, a Decision-Making Trial and Evaluation Laboratory (DEMATEL) model was established, with passenger comfort as the target layer, to determine the interrelation between 14 PSI factors. The causal relationships between the 14 factors were visualized by a causal diagram. We established a priority ranking of the 14 aircraft interior design indexes based on the corresponding relationships between the indexes and PSI factors. The findings of this study contribute to the understanding of how PSI impacts passenger comfort and offer strategies to improve the comfort design of aircraft cabins.

Jet Engines – Bearings, Seals and Oil Consumption

Purpose of this review is to understand how to find values for three input values for the calculation of the oil concentration in aircraft cabins. These are the number of bearings of the jet engine and the number of them upstream of the bleed air ports as well as the oil consumption per hour. ---Methodology is an Internet review of related facts. ---Findings: Jet engine schematics are available online and can be interpreted to find the number of bearings.Values for the CFM56 engine are 5 bearings with 3 of them upstream of the bleed port. Oil consumption should be assumed to be 0.3 L/h for the CFM56 engine.Rates for selected other engines are also given. ---Research limitations are due to the fact that detailed company data is not available and own measurements can not be made on passenger jets.