Aircraft Cabin Research Articles

Low-temperature and in-situ regenerable ozone decomposition in aircraft with zeolite-encapsulated manganese-oxo cluster catalyst

Eliminating Ozone (O3) in aircraft cabin via catalytic decomposition is of vital importance to passenger health and oil tank anti-explosion. However, commercial catalysts work constantly at high temperature and need take-out regeneration after deactivation, causing high energy consumption and tedious maintenance. Here we attempt to address this issue by developing a manganese-oxo cluster encapsulated zeolite with initial wetness impregnation and microwave drying coupled method. Time-dependent O3 decomposition test show that the efficiency on the optimized sample was kept over 95 % for 98 h at low-temperature (−5 °C) and superhigh space velocity (720000 h−1), and well reproduced after mild regeneration (180 °C by air for 1 h, the lowest temperature for reversible regeneration of O3 catalyst reported ever). Combined EXAFTS, XPS, and DFT calculations reveal the mechanism: luxuriant charge transfer path within the [Mn3O3]n+ cluster accommodated in FAU supercage facilitates the allocation of electrons released from the rate-controlling step, rendering lower barrier energy and stabilized state of manganese for O3 decomposition. An application strategy of “cold air direct-processing and periodic in-situ regeneration” was patterned by robust performance on washcoated structured catalysts. This work affords new insights for upgrading aircraft O3 decomposition and presents metal-oxo zeolite as a platform to tailor practical catalysts.

Fuselage panel structural-acoustic optimization design of civil aircraft based on numerical analysis

Abstract During the design process of civil aircraft, it is necessary to achieve a high level of cabin noise control to improve cabin comfort. In addition to controlling the intensity of the main noise sources that affect the acoustic environment in the cabin, the acoustic optimization design of the fuselage wall panel structure is also required. In this paper, acoustic analysis software ACTRAN is applied to study the acoustic characteristics of typical structures of civil aircraft cabins. Boundary conditions, material density, and material damping are analyzed from the following main aspects: fuselage panels, thickness, density, reinforced frame design, etc., to study the acoustic barrier performance of typical fuselage panel structures, put forward design suggestions for fuselage panels, and guide the acoustic optimization design of civil aircraft structures.

Review of Wavenumber-Frequency Spectrum Models of Turbulent Boundary-Layer Wall Pressure Fluctuations

Turbulent boundary layer wall pressure fluctuations are of significant concern in acoustic engineering for both high-speed airborne and underwater vehicles, and the modeling of the associated wavenumber-frequency spectra has been extensively studied. In this paper, a review of 12 models developed between 1964 and 2017 has been conducted, and both the 2D and 1D forms investigated. In this work, fundamental concepts are introduced, followed by a classification of the models into two categories, that is, Corcos-type and non-Corcos-type models. Both the 2D and 1D forms of the 12 models are individually introduced in chronological order. To evaluate these models, comparisons of the 2D and 1D wavenumber-frequency spectra at different speeds and frequencies were conducted. Unlike Corcos-type models, non-Corcos-type models are grounded in a stronger theoretical foundation, with some models accurately reflecting acoustic region characteristics. Corcos-type models exhibit good consistency, however, they require an auto-spectrum as a necessary input, which makes them semiempirical models. In addition, the models within the Corcos-type and the non-Corcos-type were also compared, respectively, and a few important conclusions were accordingly made. The research output from this paper can provide an important practical engineering reference for studies associated with acoustic engineering, such as aircraft cabin noise and submarine hydrodynamic noise.

Acoustical properties of the new sandwich structures for aircraft cabin interiors with integrated vacuum insulation

AbstractAny modern passenger aircraft must provide a high level of comfort for passengers who spend considerable time inside the cabin. The cabin's climate and interior noise levels contribute to this comfort. Vacuum insulation panels (VIP) have been explored as insulation materials to improve these factors due to their extremely low thermal conductivity. When integrating VIPs into the aircraft cabin's interior, it was discovered that the thermal conductivity of the entire sandwich structure was 3–6 times lower than conventional structures. This finding has generated much interest in using VIPs for aircraft cabin insulation. This article delves into the acoustic properties of these new structures featuring integrated VIPs. Tests were carried out to analyze the sound insulation capabilities of these structures. The results showed that the new interior structures exhibited promising acoustic properties.

The importance of different body parts for the (un-)pleasantness of whole-body vibration on an aircraft seat bench

Noise and vibration are two physical factors that can reduce the perceived comfort of passengers during a flight. To reduce the detrimental impact of seat transmitted vibration, it is necessary to understand which body parts and, thus, which corresponding seat parts are relevant for the pleasantness assessment. In this study, 40 participants (19 female, 21 male) rated the pleasantness of sinusoidal whole-body vibrations in the vertical direction while seated on a typical aircraft seat bench and listening to a synthetic broadband aircraft cabin noise over headphones. The vibration signals covered seven frequencies and four vibration levels, and pleasantness ratings were made on a verbally anchored scale. In addition, the participants separately marked those body parts that contributed significantly to their rating and those where they felt a vibration for each of the vibroacoustic stimuli. The results showed that not all body parts at which vibration were felt were also classified by the participants to reduce the ratings significantly, especially at higher vibration levels. A median split of the participants into groups of lighter and heavier participants indicates which body properties might be underlying factors for certain judgments.

Design of lightweight aircraft trim panel with a high sound transmission loss

The trim panels of aircraft cabin are frequently made up of multilayer materials including a honeycomb, typically in the form of sandwich panels, which have the advantage of being lightweight and space-saving, but lack good acoustic insulation. It has been shown that, for 10% more mass, weights arranged in a fractal pattern in the honeycomb affect the vibratory pattern of a sandwich panel by creating multiple reflections of the bending waves on the inclusions. They thus generate a phenomenon of focusing vibratory waves providing localized modes while attenuating the structure's acoustic radiation. The objectives of this paper are to describe: first, the vibro-acoustic model of an overloaded homogenized bending panel (to mimic a trim panel with a fractal pattern); second, the physical phenomena associated to this concept; third, the impact on the modal behavior and the vibratory and acoustic responses.

An efficient strategy based on proper orthogonal decomposition for rapid determination of the location and rate of water vapor humidification in aircraft cabins

Currently, the air in commercial aircraft cabins during flights routinely exhibits extremely low relative humidity. But none of the previously published studies have addressed optimization of the humidification parameters in order to, create the desired humidity distributions in aircraft cabins at minimal cost. This study proposed an efficient strategy to accomplish the task. Under this strategy, a database of various potential humidification locations for aircraft cabins is first constructed. One scenario in the database is then selected by computational fluid dynamics (CFD)-based enumeration. Next, with the humidification location as prior information, the humidification rate and the air-supply temperature from the main ventilation system can be inversely designed by proper orthogonal decomposition. The above strategy was applied to a three-dimensional aircraft cabin model for the validated CFD cases. The results showed that an appropriate humidification for the cabin might both improve the thermal comfort of passengers and increase the humidity levels in the cabin; a decrease of the air-supply temperature from the main ventilation system would be beneficial in reducing the water vapor humidification rate required for passengers and allowing a higher humidification rate to be tolerated for the cabin walls. The parameters that improved the cabin air environment without significant moisture accumulation on walls were also provided by the proposed strategy. Compared with the full CFD simulation method, the proposed strategy is capable of providing accurate ranges of parameters while reducing the computing time by more than 95%, which demonstrates its competitive prospects.

Model-based assembly process planning for flexible aircraft cabin architectures

The configuration and equipment of an aircraft cabin has a significant impact on the passenger’s flight experience. To meet the needs of passengers and improve the flight experience, airlines repeatedly demand customised adaptations to the cabin design. The implementation of these changes requires a high degree of flexibility in production and can lead to difficulties in setting up a fixed final assembly line. In addition, unforeseen events and changes in the OEMs’ supply chain require a rapid response in aircraft production to be able to deliver on time. Digitalisation in product development and production planning makes it possible to overcome these challenges and makes an important contribution to flexibility, time and cost efficiency. This paper presents a digital approach to modelling and flexible planning of assembly processes of the cabin. To this end, aircraft design data is automatically linked to the assembly system to react quickly to design changes in the assembly planning process. The integration is realised in a system architecture model depicted with the systems modelling language (SysML). The architecture model follows the formal process description defined in VDI3682. A planning algorithm then uses the production architecture parameters to optimise the assembly processes, e.g. in terms of time. The approach presented is demonstrated using the example of scheduling the pre-assembly processes of the "crown module". The latter includes all structural and functional components above the window panels, such as overhead bins, electrics and air conditioning. The results show how changes in aircraft and cabin design or in the production plant and resources can be flexibly evaluated. This allows conceptual changes to be evaluated and traded before the cabin design is frozen and transferred to real production. These advantages contribute to the time and cost optimisation of aircraft production. This work thus makes a valuable contribution to the further development of digital solutions in aircraft production.

Research on cabin VOC controlling of civil aircraft

Abstract This article outlines the main sources of VOC in civil aircraft cabins. We compared the current state of control at home and abroad in this field and found there remains a huge blank in relevant domestic standards. To further clarify the baseline of VOC levels in domestic civil aircraft cabins, the VOC contents in the cabin of a domestic aircraft were tested and analyzed by referring to relevant domestic and foreign standards, after which several control suggestions were given. This work is of great significance for establishing VOC control standards in domestic civil aircraft cabins.

Certification considerations and sound field simulation of civil aircraft cabin passenger address

Abstract In the design of a civil aircraft cabin passenger address system, it is quite necessary and very important to sufficient consider and demonstrate the system design architecture, equipment selection and arrangement to ensure that the system sound quality complies with the requirements of CCAR25.1423(c). In the design phase, the certification considerations of the passenger address system should be researched in advance to comply with CCAR25.1423(c). The cabin sound field distribution and STI of the civil aircraft cabin passenger address system should be simulated through professional tools to predict, demonstrate and judge the sound quality before the system preliminary design review (PDR). In this paper, the certification considerations of passenger address are developed and elaborated from the system equipment arrangement, automatic gain design, and inhibit method of the Larsen effect. Based on two loudspeaker arrangement options, the cabin sound field distribution and STI of the passenger address are simulated to indicate its compliance with CCAR 25.1423(c) from the proposal design level theoretically.

Investigating Intumescent Flame-Retardant Additives in Polyurethane Foam to Improve the Flame Resistance and Sustainability of Aircraft Cabin Materials

Polyurethane (PU) foam has a high flammability and is widely used in aircraft interiors, presenting a significant danger to occupants. This study analysed three composite intumescent flame-retardant (IFR) coatings for flexible PU foam; expandable graphite (EG), ammonium polyphosphate (APP) and alginate (AG). The coatings were prepared in concentrations of 5 wt%, 10 wt%, and 50 wt% with an acrylic binder. The coated samples were characterised using cone calorimetry, SEM, and mechanical testing. The findings showed peak heat release rate, total heat release, and carbon dioxide production from the 10 wt% triple-layer coating (EG:APP:AG) was 52%, 32%, and 58% less than the PU control. The char of the 10 wt% triple-layer sample effectively suppressed smoke release and inhibited the transfer of fuel and gas volatiles. Mechanical testing demonstrated a 3.4 times increase in tensile strength and a 15.4 times increase in compressive strength (50% compression) compared to the control PU with the 10 wt% triple-layer coating. A fire dynamics simulator model was developed that demonstrated large-scale flammability modelling for commercial aircraft. Future work can explore the integration of IFR coatings into computational analysis. These new bio-based coatings produced promising results for aircraft fire safety and flammability performance for PU polymers.

Knowledge-based model generation for aircraft cabin noise prediction from pre-design data

The climate targets set out in the “European Green Deal” call for the consideration and implementation of climate-friendly propulsion concepts and sustainable fuels in future aircraft configurations. This puts the use of very efficient propeller engines into the focus of aircraft design. However, these pose major challenges, especially to cabin acoustics, due to high, tonal sound pressure levels on the fuselage. The design of noise control measures requires the competence to predict the resulting interior noise as early as possible in the design process of the vehicle. This requires a high level of geometric and structural detail regarding the fuselage structure and cabin components. With increasing frequency range, the necessary structural details also increase, which have to be resolved in the simulation models due to the associated decreasing structural wavelength. Especially in the context of aircraft pre-design, there is usually not enough information available for a detailed vibro-acoustic modeling of the fuselage and cabin components, which allows a meaningful prediction of the vibrations and thus the cabin noise. Therefore, the knowledge-based tool Fuselage Geometry Assembler (FUGA) is developed for the targeted enrichment of preliminary design data with knowledge for detailed numerical analyses. This paper describes the knowledge-based geometry and model generation in FUGA, which can consider the necessary (increasing) level of detail for the vibro-acoustic prediction already in the preliminary design. For this purpose, aircraft data sets in the preliminary design data format Common Parametric Aircraft Configuration Schema (CPACS) form the modeling basis. Originating from the aircraft preliminary design, these initially describe the outer shell of the vehicle and are extended by detailed structural information that defines the geometric boundary conditions for component placement in cabin design. For the cabin components, the open-source geometry kernel Open Cascade Technology (OCCT) is used to provide geometries at the level of detail required for subsequent analyses. The geometry models are then discretized in open source (e.g. Gmsh) or commercial meshers and further used for numerical analysis. Finally, the prediction of cabin noise is demonstrated as a Proof of Concept using the example of a short-haul propeller-driven aircraft and the feasibility of the proposed method is indicated by investigating the sensitivity of resulting simulation models to the fuselage skin thickness.

The Dynamic Prediction Method for Aircraft Cabin Temperatures Based on Flight Test Data

The Dynamic Prediction Method for Aircraft Cabin Temperatures Based on Flight Test Data

Optimal Design of Assembling Robot Considering Different Limb Topologies and Layouts

Abstract A class of 5 degree-of-freedom (DoF) hybrid robots consisting of one translational and two rotational (1T2R) parallel module and 2 T serial module is presented for assembling in the aircraft cabin. The 1T2R parallel modules are with three limb topologies (PRS, RRS, and internal closed loop) and two layouts (symmetrical and “T” shape). Herein, P, R, and S denote prismatic, rotational, and spherical joints. This article presents the multi-objective optimization of the hybrid robot regarding different limb topology, limb layout, and corresponding dimensions as design variables. Considering demands from the in-cabin assembling, kinematic, linear stiffness along z-axis and total mass of the robot are the objectives. The Pareto fronts and cooperative equilibrium point (CEP) indicate that the robot with 3-PRS and 3-RRS parallel module have better performances than the one with internal closed loop. The overall performances of robot with symmetrical layout are superior than the one with “T” shape layout. In addition, two optimization methods are compared. One is to separately optimize six robots with specific topology and layout. The other is to optimize all design variables in a model. It is found that six robots have their own performance zones. Therefore, final optimums of two methods are close to each other. But optimization in one model is able to eliminate unfeasible topologies in the early stage of searching and thus is more efficient. Optimal module is 3-PRS with symmetrical layout. Experiments on the physical prototype validate performances of the optimal robot.

Optimal operations of gaspers for minimizing the exposure risks of airborne disease transmission in an economy-class aircraft cabin

Overhead gaspers with adjustable open ratios and flow directions can alter the airflow pattern in aircraft cabins and consequently influence airborne infectious diseases transmission. To achieve the optimal operations of gaspers for minimizing the passengers’ exposure risks, this study developed a Bayesian optimization method based on computational fluid dynamics (CFD). A seven-row, single-aisle, fully occupied, economy-class aircraft cabin was used for the numerical investigation. Two air distribution systems, i.e., a mixing ventilation system and a personalized displacement ventilation system, were considered. First, the open ratios of all the gaspers were optimized by the CFD-based Bayesian optimization method. The optimal operations of gaspers were determined with only 20 trials calculated by CFD using the Bayesian optimization. With the optimal open ratios of all the gaspers, the number of relatively high-risk passengers (exposure index over 0.95) was effectively reduced by at least 55% and 86% under the mixing ventilation and the personalized displacement ventilation, respectively, when compared with the results with all the gaspers turned off. Next, the optimal open ratios and flow directions of the gaspers near the index passenger were also determined by the proposed method. With the optimized operations of gaspers, the number of relatively high-risk passengers was effectively reduced by at least 50% and 67% under the mixing ventilation and the personalized displacement ventilation, respectively.

The randomness and determinacy of wall pressure fluctuations in incompressible flow

Wall pressure fluctuations caused by turbulent boundary layers have a significant impact on aircraft structural vibration and cabin noise. This study aims to investigate the mechanism of turbulence-induced pressure fluctuations by focusing on the randomness of wall pressure fluctuations, analyzed in both the time–frequency and spatial-wavenumber domains using measured data obtained from a phase array in a wind tunnel. Three roughness elements were designed and installed upstream of the plate to manipulate the turbulent boundary layer at a specific Mach number. The results of the investigation demonstrate that the disturbance strength induced by the roughness element influences the randomness of wall pressure fluctuations, in addition to the parameters utilized for data analysis. Generally, stronger turbulence fluctuations tend to decrease the randomness of pressure fluctuations. Moreover, wall pressure fluctuations also exhibit certain statistical principles that cannot be precisely calculated using mathematical expressions, highlighting their inherent randomness. Further investigation into randomness in the spatial-wavenumber domain revealed the hydrodynamic modes of turbulence fluctuations with varying convection velocity analyzed through wavenumber maps computed using the beamforming algorithm. These modes with variable convective speed significantly contribute to the generation of randomness in wall pressure fluctuations. Both the time–frequency domain and the spatial-wavenumber domain affect the randomness characteristics of wall pressure fluctuations. However, such effects are not easily discernible through a rudimentary analysis of the space–time correlation of turbulence fluctuations.

Flying to high-altitude destinations.

Every year millions of people fly to high-altitude destinations. They thereby expose themselves to specific high-altitude conditions. The hypoxic environment (low ambient oxygen availability) constitutes a major factor affecting health and well-being at high altitude. While the oxygen availability is already moderately reduced inside the aircraft cabin, this reduction becomes aggravated when leaving the plane at high-altitude destinations. Especially if not pre-acclimatized, the risk of suffering from high-altitude illnesses, e.g., acute mountain sickness, high-altitude cerebral or pulmonary edema, increases with the level of altitude. In addition, diminished oxygen availability impairs exercise tolerance, which not only limits physical activity at high altitude but may also provoke symptomatic exacerbation of pre-existing diseases. Moreover, the cold and dry ambient air and increased levels of solar radiation may contribute to adverse health effects at higher altitude. Thus, medical pre-examination and pre-flight advice, and proper preparation (pre-acclimatization, exercise training, and potentially adaptation of pharmacological regimes) are of utmost importance to reduce negative health impacts and frustrating travel experiences.

Implementation of a toolbox for the generation of flight profiles for use in simulator studies

Motion sickness is a phenomenon which can produce various symptoms in affected individuals. During development of new aircraft types and cabin layouts, it is important to consider this phenomenon early on, to reduce resulting effects. For research on this topic, German Aerospace Center uses the simulator environment Air Vehicle Simulator together with the Advanced Future Cabin. The Air Vehicle Simulator is a full flight simulator with an interchangeable cockpit module. One of those modules is the Advanced Future Cabin, a realistic replica of an aircraft cabin. Good standardization of the test conditions is required to ensure objectivity and reliability of motion sickness studies in this simulator environment. A specialized software infrastructure is used to replay pre-recorded flight profiles, which are then reproduced by the simulator’s motion, visual and audio systems. Using this replay approach, complete flight profiles can be reproduced very well. However, when parts of the flight profile need exact reproduction within a flight profile or across multiple flight profiles, the approach to record pilot-in-the-loop simulation sessions becomes problematic, as flying the exact same twice is almost impossible. As an improved approach, a toolbox has been implemented, which automates the generation of flight profiles, enabling easier and more precise research on motion sickness in the simulator. The toolbox replaces the pilot-in-the-loop simulation with an automated control of the underlying aircraft simulation model. This leads to greatly improved accuracy of inputs to the simulation model and thus very good reproducibility even of flight profile segments. In this manuscript, details of the toolbox implementation and its validation are discussed.

A Review of In-Flight Thermal Comfort and Air Quality Status in Civil Aircraft Cabin Environments

The civil aircraft cabin is enclosed and highly occupied, making it susceptible to a decline in indoor environmental quality. The environmental quality of civil aircraft cabins not only depends on objective factors such as temperature, relative humidity, and the presence of air pollutants such as carbon dioxide (CO2), carbon monoxide (CO), ozone (O3), particle matter (PM), and volatile organic compounds (VOCs) but also the subjective factors pertaining to the perceptions and health symptoms of passengers and crew. However, few studies have thoroughly examined the air quality and thermal comfort parameters that are measured during in-flight testing in airplane cabins, as well as the passengers’ subjective perceptions. In order to evaluate the in-flight thermal comfort and air quality status, this study conducted a review of the recent literature to compile data on primary categories, standard limits, and distribution ranges of in-flight environmental factors within civil aircraft cabins. Following a search procedure outlined in this paper, 54 papers were selected for inclusion. Utilizing the Monte Carlo method, the Predicted Mean Vote (PMV) distributions under different exercise intensities and clothing thermal resistance were measured with the in-cabin temperature and humidity from in-flight tests. Recommendations based on first-hand data were made to maintain the relative humidity in the cabin below 40%, ensure wind speed remains within the range of 0–1 m/s, and regulate the temperature between 25–27 °C (for summer) and 22–27 °C (for winter). The current estimated cabin air supply rate generally complies with the requirements of international standards. Additionally, potential carcinogenic and non-carcinogenic risks associated with formaldehyde, benzene, tetrachloroethylene, and naphthalene were calculated. The sorted data of in-flight tests and the evaluation of the subjective perception of the occupants provide an evaluation of current cabin thermal comfort and air quality status, which can serve as a reference for optimizing indoor environmental quality in future generations of civil aircraft cabins.

Carbon monoxide measurements in BAe 146 aircraft cabins

Carbon monoxide measurements in BAe 146 aircraft cabins