Коротаева Т.А.   Турчинович А.О.  

Numerical simulation of interaction between exhaust jets of engines and a jet blast deflector with the account of chemical reactions

Reporter: Турчинович А.О.

Every year the cargo volume and passenger number dispatched by air keeps steadily growing. According to Rosaviation information, the number of passengers serviced by Russian airports has increased by 20.4% from 2012 to 2015. The result of such intensive use of aircraft transport is pollution of the environment. Emission of engine combustion products leads to the change in composition of the atmosphere, either directly, through the emission of carbon dioxide, nitrogen oxides, water vapor, unburned hydrocarbons (benzene, propane, ethane, acetylene, methane and others.), sulfate particles and soot, or indirectly, contributing in the formation of ozone as a result of the chain of chemical reactions, similar to the formation of smog. That affects the health of staff of airports and people living nearby. That is why the estimation of pollutant level in the vicinity of airports is an extremely important problem. In most cases this estimation is carried out by simplified, engineering methods that could not permit to obtain correctly all details of complex dynamics and chemical interaction between exhausts and air.
The situation is even worse for the stage of exploitation called ground running procedure (GRP), when the interaction of high-speed and high-temperature exhausts with jet blast defense should be taken into account.
The paper presents an approach that allows defining spatial distribution of pollutant concentrations released at engine ground running procedure using full gas-dynamic models. The task is modeled in three-dimensional approximation in the framework of the numerical solution of the Navier-Stokes equations (RANS) with taking into account a kinetic model of interaction between the components of engine exhaust and air. The complex pattern of gas-dynamic flow that occurs at the four jets interact with each other, air, jet blast deflector (JBD) has been studied in the present work. The numerical technique developed for calculating the concentrations of pollutants produced at the GRP stage permits to define level, character, and area of contamination more reliable.
Conditions at the nozzle exit (mixture species, temperature, speed) correspond to the full-thrust regime. In this case the NOx concentration is high. At the same time the concentration of unburned hydrocarbons is low and we can assume that chemically active substances at complete combustion of fuel can be carbon monoxide and nitrogen that can be oxidized by atmospheric oxygen to the corresponding dioxides. Thus, the approach used takes into account both pollutant and products of oxidizing by air at their distribution and interaction with a JBD.
Conditions in the free flow are: the atmospheric pressure is of 101325 Pa, static temperature is of 17 °C, the wind direction at a speed of 5 m/s coincides with the direction of the jets.
The motion of a viscous, compressible gas described by the Navier-Stokes equations with due regard for the speed and temperature of the jets of aviation fuel combustion products. 'Density-based' solver, unsteady implicit difference scheme of the second order of approximation, and the SST k-ω turbulence model are accepted as set of options for ANSYS FLUENT (academic).
Simulation of the jets of the aircraft located on the run-ground has been carried out for a three-dimensional computational domain that includes the surfaces of the JBD and nozzle exits. The JBD can be of different design.
Simulation of the jets of the aircraft located on the run-ground has been carried out for a three-dimensional computational domain that includes the surfaces of the JBD and nozzle exits. The JBD can be of different design.
In paper [1] modelling has been carried out for the flow around an aircraft with the chemically active jet exhausts and a JBD either solid or mesh faced. Cases with different distances between the aircraft and solid faced JBD have been considered, too. Numerical simulation performed permits to define possible peculiarities of the flow, region of their influence and esteem level of pollution depending on face structure of JBD or the distance between the aircraft and JBD.
The present work is devoted to the continuation of research in this field. The results of a comparative analysis of the pollutant distribution at the interaction of exhaust gases with JBDs of various geometric configurations are presented as well as conclusions about the effectiveness of each gas deflector.

1. Korotaeva T. A. Numerical simulation of the pollution formed by exhaust jets at the ground running procedure / T. A. Korotaeva, A. O. Turchinovich // AIP Conference Proceedings. - 2016. - Vol. 1770 : 18 International conference on the methods of aerophysical research (ICMAR2016). - Art. 030070 (7 p.). - DOI: 10.1063/1.4964012.

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