A Review on Effects of Personalized Ventilation Systems on Air Quality and Thermal Comfort in Aircraft Cabin Mini-Environments

This study conducts an evaluation of air quality,dispersion of airborne expiratory pollutants and thermal comfort in aircraft cabin mini-environments using a critical examination of significant studies conducted over the last20 years.The research methods employed in these studies are also explained in detail.Based on the current literature,standard procedures for airplane personal ventilation and air quality investigations are defined for each study approach.Present study gaps are examined,and prospective study subjects for various research approaches are suggested.

Flow Characteristics of Double-Cruciform Parachute at Inflating and Inflated Conditions

The fluid-structure interaction (FSI) between the canopy and flow field on the inflating and inflated conditions is investigated based on the arbitrary Lagrange-Euler (ALE) method,in both a single-and double-cruciform parachute systems.The projection area of canopy is calculated in the inflation process.The flow field characteristics and the interaction between canopies are analyzed.Results showed that,with free stream velocity of 50m/s,overinflation phenomenon would not occur during the inflation process of the double-cruciform-parachute system,because the collision and extrusion of the two canopies during inflation obstructed the oscillation of the inner gores.Concurrently,compared with the single-cruciform parachute,the vortex motion in the wake of double-cruciform-parachute is more intense.Thus the double-cruciform parachute system oscillated at a velocity of 50 m/s with an angle of less than 6.8°.By comparison,the oscillation angle of the single-cruciform parachute was within 3.5° at the velocity of 50m/s.The results are consistent with those of the wind tunnel test.

Effects of Geometric Parameters on Performance of Rectangular Submerged Inlet for Aircraft

To improve the comfortability and safety of aircraft,the demand of rectangular submerged inlets(RSIs)with low resistance is proposed to increase the inlet flow rate of ram air. A theoretical model is built to numerically analyze the effects of geometric parameters on the inlet mass flow rate of RSIs. The geometric parameters in question here encompass the aspect ratio of 2—4,the ramp angle of 6°—7°,the characteristic parameter of the throat of 0.20 —0.30,the ramp length of 939—1 337 mm,and the cone angle of 0° —3°. Simulation results demonstrate that the mass flow rate(MFR)is positively correlated with the aspect ratio,ramp angle,ramp length,and cone angle,and negatively correlated with characteristic parameter of the throat. Within the range of the geometric parameters considered,the RSI with the aspect ratio of 3,the ramp angle of 6°,the characteristic parameter of the throat of 0.20,the ramp length of 1 337 mm,and the cone angle of 3° obtains the largest MFR value of about 2.251 kg/s.

The future and technique challenges of high-speed ground effect vehicle enrolled in maritime transportation

This paper presents a high-speed ground effect vehicle(HS-GEV)used specifically for maritime transportation.Given the limitations of current vessels,including various types of watercraft and high-speed boats,in fulfilling of needs in different maritime transportation scenarios,the HS-GEV emerges as a promising solution to address unmet requirements.To efficiently accomplish maritime transportation missions with quickness and safety,several critical features are emphasized,including short take-off on water,flight maneuverability and flight stability.The key techniques required to achieve these features,as well as recent progress highlights,are introduced.Following and promoting these crucial techniques is also suggested as a future step to improve HS-GEV performance.With its predominant features,the HS-GEV holds immense application value in enhancing a high-speed maritime transportation system that aligns with the evolving needs of the real world.

A Novel Aircraft Air Conditioning System with a Sterilization Unit by Ultra-High-Temperature Air Stream

An aircraft cabin is a narrow,closed-space environment.To keep the air quality in cabin healthy for passengers,especially during an epidemic such as SARS-CoV-2(or 2019-nCoV)in 2020,a novel aircraft air conditioning system,called the ultra-high-temperature instantaneous sterilization air conditioning system(UHTACS),is proposed.Based on the proposed system,a simulation of the UHT-ACS is analysed in various flight states.In the UHT-ACS,the mixing air temperature of return and bleed air can reach temperature up to 148.8°C,which is high enough to kill bacilli and viruses in 2一8 s.The supply air temperature of the UHT-ACS in a mixing cavity is about 12 C in cooling mode both on the ground and in the air.The supply air temperature is about 42 C in heating mode.Compared with the air conditioning systems(ACS)of traditional aircraft the supply air temperatures of the UHT-ACS in the mixing cavity are in good agreement with those of a traditional ACS with 60%fresh air and 40%return air.Furthermore the air temperature at the turbine outlet of the UHT-ACS is higher than that of a traditional ACS which will help to reduce the risk of icing at the outlet.Therefore the UHT-ACS can operate normally in various flight states.

Experimental comparison between aircraft fuel tank inerting processes using NEA and MIG

Fuel tank inerting technologies are able to reduce the fire risk by injection of inert gas into the ullage or fuel, the former called ullage washing and the latter fuel scrubbing. The Green On-Board Inert Gas Generation System（GOBIGGS） is a novel technology based on flameless catalytic combustion, and owning to its simple structure and high inerting efficiency, it has received a lot of attentions. The inert gas in the GOBIGGS is mainly comprised of CO2, N2, and O2（hereinafter, Mixed Inert Gas（MIG））, while that in the On-Board Inert Gas Generation System（OBIGGS）, which is one of the most widely used fuel tank inerting technologies, is NitrogenEnriched Air（NEA）. The solubility of CO2 is nearly 20 times higher than that of N2 in jet fuels,so the inerting capability and performance are definitely disparate if the inert gas is selected as NEA or MIG. An inerting test bench was constructed to compare the inerting capabilities between NEA and MIG. Experimental results reveal that, if ullage washing is adopted, the variations of oxygen concentrations on the ullage and in the fuel are nearly identical no matter the inert gas is NEA or MIG. However, the ullage and dissolved oxygen concentrations of MIG scrubbing are always higher than those of NEA scrubbing.

Effect of fuel type on the performance of an aircraft fuel tank oxygen-consuming inerting system

The properties of aviation fuel have a great influence on the performance of oxygenconsuming inerting systems. Based on the establishment of the catalytic inerting process, the flow relationship of each gas component flowing through the catalytic reactor was derived. The mathematical model of the gas concentration in the gas phase of the fuel tank was established based on the mass conservation equation, and the fuel tank model was verified by performing experiments.The results showed that the fuel type exerts a considerably higher influence on the performance of the oxygen-consuming inerting system compared to the corresponding influence on the hollow fiber membrane system, and the relative magnitude of the inerting rates of the four fuel types is RP5 > RP3 > RP6 > JP8. In addition, a higher catalytic efficiency or fuel load rate corresponds to a higher rate of decrease of the oxygen concentration in the gas phase, and the inerting time is inversely proportional to the suction flow rate of the fan. When different fuels are used, the amount of cooling gas and water released from the inerting system are different. Therefore, the influence of fuel type on the system performance should be extensively considered in the future.

Shock-Wave/Rail-Fasteners Interaction for Two Rocket Sleds in the Supersonic Flow Regime

Rocket sleds belong to a category of large-scale test platforms running on the ground.The applications can be found in many fields,such as aerospace engineering,conventional weapons,and civil high-tech products.In the present work,shock-wave/rail-fasteners interaction is investigated numerically when the rocket sled is in supersonic flow conditions.Two typical rocket sled models are considered,i.e.,an anti-D shaped version of the rocket sled and an axisymmetric slender-body variant.The dynamics for Mach number 2 have been simulated in the framework of a dynamic mesh method.The emerging shock waves can be categorized as head-shock,tailing-shock and reflected-shock.An unsteady large-scale vortex and related shock dynamics have been found for the anti-D shaped rocket sled.However,a quasi-steady flow state exists for the slender-body shaped rocket sled.It indicates that the axisymmetric geometry is more suitable for the effective production of rocket sleds.With the help of power spectral density analysis,we have also determined the characteristic frequencies related to shock-wave/rail-fasteners interaction.Furthermore,a harmonic phenomenon has been revealed,which is intimately related to a shock wave reflection mechanism.

Fluid structure interaction of supersonic parachute with material failure

The material damage of parachute may occur in parachutes at high speeds,and the growth of tearing may finally lead to failure of aerospace mission.In order to study the damage mechanism of parachute,a material failure model is proposed to simulate the failure of canopy fabric.The inflation process of supersonic parachute is studied numerically based on Arbitrary Lagrange Euler(ALE)method.The ALE method with material failure can predict the transient parachute shape with damage propagation as well as the flow characteristics in the parachute inflation process,and the simulated dynamic opening load is consistent with the flight test.The damage propagation mechanism of parachute is then investigated,and the effect of parachute velocity on the damage process is discussed.The results show that the canopy tears apart by the fast flow from the initial damaged area and the damaged canopy shape leads to the asymmetric change of the flow structure.With the increase of Mach number,the canopy tearing speed increases,and the tearing directions become uncertain at high Mach numbers.The dynamic load when damage occurs increases with the Mach number,and is proportional to the dynamic pressure above the critical Mach number.

Measurement of mass diffusion coefficients of O_2 in aviation fuel through digital holographic interferometry

The experimental apparatus to measure the mass diffusion coefficients of O2 in aviation fuel was constructed based on the digital holographic interferometry method. The theory of mass diffusion coefficient and interference image processing were introduced in detail. The accuracy of the experiment was verified by measuring the mass diffusion coefficient of 0.33 mol/L KCl in aqueous solution at 298.15 K. The mass diffusion coefficients of O_2 in RP3 and RP5 aviation fuels were measured at temperature from 278.15 K to 333.15 K, and the Arrhenius equation was employed to fit the experimental data. In terms of the Stokes-Einstein equation, the viscosities of these two aviation fuels were tested to estimate the correlation among mass diffusion coefficient, viscosity and temperature. A uniform polynomial calculation correlation was proposed to predict the mass diffusion coefficients of O_2 in both RP3 and RP5 aviation fuels, and its accuracy is considerably higher than that of the Stokes-Einstein equation.

Fluid structure interaction simulation of supersonic parachute inflation by an interface tracking method

An Arbitrary Lagrangian-Eulerian(ALE)approach with interface tracking is developed in this paper to simulate the supersonic parachute inflation.A two-way interaction between a nonlinear finite element method and a finite volume method is accomplished.In order to apply this interface tracking method to problems with instantaneous large deformation and self-contact,a new virtual structure contact method is proposed to leave room for the body-fitted mesh between the contact structural surfaces.In addition,the breakpoint due to the fluid mesh with negative volume is losslessly restarted by the conservative interpolation method.Based on this method,fluid and structural dynamic behaviors of a highly folded disk-gap-band parachute are obtained.Numerical results such as maximum Root Mean Square(RMS)drag,general canopy shape and the smallest canopy projected areas in the terminal descent state are in accordance with the wind tunnel test results.This analysis reveals the inflation law of the disk-gap-band parachute and provides a new numerical method for supersonic parachute design.

Theoretical study of ullage washing with mixed inert gas in a non-equilibrium state

The Mixed Inert Gas(MIG)produced by the novel Green On Board Inerting Gas Generation System(GOBIGGS)mainly consists of carbon dioxide,nitrogen and oxygen.Because of the large solubility of carbon dioxide in jet fuel compared with nitrogen,the no gas release or equilibrium model could not be employed any more.In this paper,first,a mathematical model of the ullage washing was set up to predict the variation of the oxygen concentration on ullage and in the fuel,and the gas evolution and dissolution rate were calculated by Fick's second law.Then,an experimental apparatus was constructed to verify the accuracy of the model.Finally,the numerical comparisons of ullage washing using Nitrogen Enriched Air(NEA)and MIG are presented under various flow rates and fuel loads,and the result reveals that the variation of the oxygen concentration on ullage is nearly identical whatever the inert gas is NEA or MIG.However,the variation of the oxygen concentration in the fuel is disparate,and the oxygen concentration decreases rapidly if the inert gas is MIG,especially when the fuel load is low or the flow rate of the inert gas is high.Besides,MIG could suppress the rising trend of the oxygen concentration on ullage when the aircraft ascends if the fuel tank is fully washed into an equilibrium state on ground.

Oxygen concentration variation in ullage influenced by dissolved oxygen evolution

To determine the oxygen concentration variation in ullage that results from dissolved oxygen evolution in an inert aircraft fuel tank,the CFD method with a mass transfer source is applied in the present study.An experimental system is also designed to evaluate the accuracy of the CFD simulations.The dissolved oxygen evolution is simulated under different conditions of fuel load and initial oxygen concentration in ullage of an inert fuel tank with stimulations of heating and pressure decrease.The increase in the oxygen concentration in ullage ranges from 0.82%to 5.92%upon stimulation of heating and from 0.735%to 12.36%upon stimulation of a pressure decrease for an inert ullage in the simulations.The heating accelerates the release of the dissolved oxygen from the fuel by increasing the mass transfer rate in the mass transfer source and decreasing the pressure,thereby accelerating the dissolved oxygen evolution by increasing the concentration difference between the gas and the fuel.The time constant that represents the oxygen evolution rate is independent of the initial oxygen concentration in ullage of an inert tank but depends closely on the fuel load,temperature and pressure.The time constant can be fitted using a polynomial equation relating the fuel load to temperature in the heating stimulation with an accuracy of 4.77%.Upon stimulation of a pressure decrease,the time constant can be expressed in terms of the fuel load and the pressure,with an accuracy of 5.02%.