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Sonic Boom for Supersonic Aircraft

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Ecological Aspects of the Impact of a Supersonic Civil Aircraft (SST) of the Second Generation of Environment . Methods of Reducing Sonic Boom, Community Noise and the Supersonic Civil Aircraft Impact on the Ozone Layer.

Tech Area / Field

  • SAT-AER/Aeronautics/Space, Aircraft and Surface Transportation

Status
8 Project completed

Registration date
27.06.1994

Completion date
26.08.1999

Senior Project Manager
Meyer U

Leading Institute
Central Aerodynamic Institute, Russia, Moscow reg., Zhukovsky

Collaborators

  • DaimlerChrysler Aerospace (Satellites), Germany, Friedrichshafen\nBoeing Technical Research Center, Russia, Moscow\nNational Aerospace Laboratory NLR, The Netherlands, Amsterdam\nSnecma Moteurs / Direction de Production-LAY, France, Evry\nAIRBUS Industrie, France, Blagnac

Project summary

The aim of this project is to investigate ecological problems associated with supersonic civilian aircraft, specifically the influence of exhaust air on the ozone layer, high-level noise from aircraft, and sonic boom. This project consists of 1) theoretical and experimental investigations of the acoustic characteristics of the ejector and the suppressor nozzle and theoretical simulation of optimization of noise reduction, 2) research on the effect of the aerodynamic configuration, flight regimes, and atmospheric conditions on the pressure distribution of sonic boom waves, 3) research on the minimization of the pressure intensity of sonic boom and the identification of a silence zone at the land surface using supersonic flow computer codes, 4) theoretical and numerical investigations on the droplet coagulation rate in the aircraft jet, the evolution of NOx chemisorption by droplets, and heterogeneous reactions in the porous particles, 5) the development of a theoretical base for a new method of measuring SST trace gases by remote laser measurements, and 6) research on the influence of non-equilibrium cluster formation on stratospheric photochemistry. The results from this project are expected to contribute to the improvement of the design of supersonic civilian aircraft.

The possibility of future development of supersonic transport (SST) is closely connected with solving related ecological problems like the impact of aircraft on the Earth's ozone layer, community noise during take-off and landing and the sonic boom problem.

Supersonic transport (SST) takes off and landings generate high levels of community noise, which significantly exceed noise levels of subsonic passenger aircraft. According to modern International Civil Aviation Organization (ICAO) regulations about allowable impact of civil aviation on the environment, SST community noise level may not exceed the noise requirements for modem subsonic aircraft (ICAO, Annex 16, Chapter 3). The intent of the proposed work is to investigate methods of achieving SST community noise compliance with ICAO reference requirements for subsonic civil aircraft. Another intent is elaboration of recommendations regarding powerplant noise suppressor systems which reduce jet noise with relatively low thrust losses. The project also seeks to develop recommendations on application of other SST community noise reduction methods.

During the course of wind tunnel and acoustic chamber investigations, the following phenomena are to be considered:


- effect of nozzle geometry on acoustic and thrust performance of ejector noise suppressors;
- effect of ejector air flow mixing conditions on acoustic and thrust performance of ejector noise suppressors;
- effect of sound-absorbing lining location on acoustic efficiency of ejector noise suppressor;
- effect of ejector noise suppressor application, on community noise levels in the vicinity of airports during take-off, landing and SST flight modes.

This project will lead to recommendations on powerplant ejector noise suppressor design and other of SST community noise reduction techniques. Preliminary data indicates that adoption of these recommendations could enable SST to comply with current ICAO noise requirements.

Current levels of SST sonic boom activity during acceleration and deceleration and in cruise flight make it impossible to fly over land at supersonic speeds. Even if supersonic flights over populated areas are forbidden, the problem of determining admissible flight corridors near land is dependent on the non-homogeneous atmosphere. The purpose of proposed investigations centers on the following 4 problems:

- Investigation of effects of aerodynamic configuration, flight regimes and atmospheric conditions on pressure distribution in sonic-boom waves. The computational method is based on numerical solution of three – dimensional gasdynamic equations (the Euler equations system) in the near field. Data obtained are matched with the sonic-boom theory solution (in the far field) for non-homogeneous atmospheric state, which is dependent on the altitude above the land surface.

- Development of new aerodynamic aircraft configurations which produce optimum sonic-boom pressure distributions (roof-top, for example) to minimize its magnitude on the ground.

- Minimization of intensity of sonic-boom intensity under different flight-induced limitations.

- Identification of "Zones of action" and "Zones of silence" at ground level in the presence of ray reflections and altitude-dependent atmospheric non-homogeneity.

One project goal is to evaluate the effects of high-altitude aircraft on the Earth's ozone layer, theoretical and numerical investigation of several turbulent wakes are proposed in the flow field of an aircraft trailing viscous vortices. Taking into account will be water vapour condensation, droplet growth rate and gas phase and heterogeneous chemical reactions. The main attention will be focused on the following topics:

- influence of vapour condensation on droplet growth rate;

- time evolution of NOx under the influence of chemical absorption by condensation droplets;

- turbulent viscosity tensor character in a 3D wake;

- heterogeneous reactions inside porous particles formed during condensation;

- the influence of supersonic non-equilibrium vibrational exitation on combustion products concentrations (hydrogen and carbon-hydrogen fuels). This is to be investigated in the combustion chamber of a scramjet, jet and in the wake behind the aircraft;

- the influence of complex Van-der-Waals formations ((H2O)2, (CO2)2, (H2O)–(CO2)) and higher order clusters exhaust jet and wake on hazardous emissions, both m the jet exhaust and the aircraft wake;

- the influence of non-equilibrium excited molecules and their clusters on atmospheric photo-chemistry;

- modeling of SST-2 exhaust properties and scenarios of its utilization will make it possible to assess the overall ecology effects of SST-2 operation.

Another project goal is to enhance the sensitivities and capabilities of lidar systems, which are used for remote analysis of SST exhaust gases. This requires theoretical analysis of laser beam propagation, absorption and scattering with the aim to elaborate on theoretical foundations. This work will lead to new lidar systems designs and improvements to performance of modern lidars.

The following important problems may be outlined:

- development of new methods of measuring concentrations of SST trace gases, taking into account the high speed of the lidar beam relative to the atmosphere.

- analytical and numerical investigation of nonlinear interaction of high-power laser beam with gases and aerosol in typical atmospheric conditions. It is planned to consider nonlinear (thermal, resonance, etc.) distortions of high power laser beams and nonlinear processes of simple molecule excitation by a strong infrared electromagnetic field.

- investigation of two-frequency and chirp-frequency absorption phenomena.

- numerical simulation of lidar beam propagation taking into account the atmospheric structure under SST impact; strong turbulence, high concentration of absorbing gases due to SST exhaust, strong non-homogeneity of gas temperature, etc.

- development of new methods to create artificial optical transparency windows in atmosphere, to detect SST emissions by lidar installed on a space platform.

Investigation one laser beam being amplified in the channel of another one due to strong molecule excitation. Creation reverse-reacting media with negative value of absorption coefficient.


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