Numerical Simulation on the Infrared Radiation Characteristics of S-Shaped Nozzles

2013 ◽  
Vol 482 ◽  
pp. 282-286 ◽  
Author(s):  
Xiang Gao ◽  
Qing Zhen Yang ◽  
Hong Zhou ◽  
Jian Nan He
Keyword(s):  
Infrared Radiation ◽  
Exhaust System ◽  
Reverse Monte Carlo ◽  
Axisymmetric Nozzle ◽  
Radiation Characteristics ◽  
Turbofan Engine ◽  
Infrared Intensity ◽  
Shaped Nozzle ◽  
Reverse Monte Carlo Method ◽  
Eccentric Distance

Infrared stealth is of great importance to increase the survival ability of the aircraft. The exhaust system is the main radiation source of the aircraft at the rare hemisphere. A program using reverse Monte-Carlo method was developed to calculate the infrared radiation intensity of afterburning turbofan engine under non-afterburning condition, and simulate axisymmetric nozzle and three S-shaped nozzles with different relative eccentric distances. The results demonstrate that: the infrared intensity of S-shaped nozzle is much lower than that of axisymmetric nozzle; S-shaped nozzle can effectively reduce the maximum of IR intensity in the rear hemispheric space; the S-shaped nozzle with the relative eccentric distance of 0.5 can reduce the intensity of infrared radiation in critical detection directions effectively.

Numerical Simulation on the Infrared Radiation Characteristics of Ejector Nozzle Based on RMCM

2011 ◽  
Vol 138-139 ◽  
pp. 879-885
Author(s):  
Li Hai Chen ◽  
Qing Zhen Yang ◽  
Jin Hui Cui
Keyword(s):  
Flow Field ◽  
Infrared Radiation ◽  
Exhaust System ◽  
Three Dimension ◽  
Radiation Characteristics ◽  
Lateral Direction ◽  
Average Temperature ◽  
System A ◽  
Infrared Intensity ◽  
Ejector Nozzle

Based on the numerical calculation of three-dimension flow field of the exhaust system, a code is developed by the reverse Monte-Carlo method (RMCM) to simulate the infrared radiation characteristics of the aeroengine exhaust system and the plume. A ray-tracing method (RTM) is introduced to seek the meshes of the flow field which the ray travels through to avoid the trouble of interpolation. The infrared radiation characteristics of a certain turbo-fan engine’s ejector nozzle in the waveband of 3-5μm is simulated at non-afterburning condition. The results of the simulation show that : (1)Because of the introduction of the secondary flow, the average temperature of the ejector nozzle’s core plume is 20K lower than the baseline one’s.(2) The infrared intensity for the ejector nozzle is most reduced relatively by 44.5% in comparison with the baseline nozzle along lateral direction.(3) The ejector nozzle has a better performance of infrared stealth.

An Improved Reverse Monte Carlo Method for the Investigation of Aerodynamic and Infrared Radiation Characteristics of a Flying Wing UAV

2020 ◽  
Author(s):  
Xiang Gao ◽  
Qingzhen Yang ◽  
Huicheng Yang ◽  
Jin Bai ◽  
Yubo He
Keyword(s):  
Monte Carlo ◽  
Ray Tracing ◽  
Infrared Radiation ◽  
Exhaust System ◽  
Aerodynamic Performance ◽  
Spectral Radiance ◽  
Reverse Monte Carlo ◽  
Carbon Dioxide Absorption ◽  
Lateral Direction ◽  
Shaped Nozzle

Abstract Using the improved ray tracing method to improve the reverse Monte Carlo (RMC) method, which is used to analyze the infrared radiation (IR) characteristics of the exhaust system, can greatly improve the computational efficiency and accuracy, and the calculation accuracy is improved by more than 8% compared with the RMC using ray tracing algorithm. For a flying wing unmanned aerial vehicle (UAV), the influence of the geometry of the double S-shaped nozzles and the single S-shaped nozzles on the internal flow field were analyzed, then the influence of the internal and external flow on the aerodynamic performance of the S-shaped exhaust system, and the IR characteristics of the aircraft with different inlet and exhaust system in the 3μm-5μm and 8μm-14μm bands were studied. The aerodynamic performance of the S-shaped nozzles are studied by numerical simulations. The IR characteristics of the rear hemisphere on the single S-shaped nozzles and the double S-shaped nozzles were obtained, those nozzles have the similar engine matching performance. The double S-shaped nozzle, resulting in a decrease of the radiation intensity of the nozzle by at least 65%, compared to the single S-shaped nozzle in the 3μm-5μm band. The aerodynamic characteristics of the flying wing UAV with the two S-shaped exhaust systems are also compared, and the changes in lift and resistance are analyzed. The forward IR intensity of the flying wing UAV is significantly lower than that of the backward direction, and the upper direction IR intensity is higher than that of the lateral direction and the downward direction. Compared to the flying wing UAV with the single S-shaped exhaust system, the flying wing of the double S-shaped exhaust system has a lower IR intensity, for the peak intensity of the rear hemisphere in the 3μm-5μm band is reduced at least 80%, the maximum value of the locked distance is reduced to 25% of the UAV using the single S curved exhaust system. The ratio of the amount of aircraft skin radiation to the total radiation increases from 30% in the 3μm-5μm band to more than 70% in the 8μm-14μm band. From the results of spectral analysis of UAV from 13μm-14μm, the spectral radiance of the carbon dioxide absorption and emission band in the detector image is significantly less than that of the UAV with a single S-shaped nozzle.

The influence of nozzle deflection on fluid dynamic and infrared characteristics of a two-dimensional convergent–divergent vectoring exhaust system

2019 ◽  
Vol 233 (12) ◽  
pp. 4646-4662
Author(s):  
Hao Wang ◽  
Honghu Ji ◽  
Haohao Lu
Keyword(s):  
Mass Flow ◽  
Infrared Radiation ◽  
Deflection Angle ◽  
Thrust Force ◽  
Fluid Dynamic ◽  
Dynamic Performance ◽  
Exhaust System ◽  
Two Dimensional ◽  
Radiation Characteristics ◽  
Significant Information

Superior maneuverability and good infrared stealthy properties are two key points of the future aircraft. A two-dimensional convergent–divergent (2D-CD) vectoring exhaust system can improve the maneuverability of aircrafts and has been widely applied to the latest generation aircrafts. Understanding fluid dynamic and infrared radiation characteristics of the 2D-CD vectoring exhaust systems under different conditions of the nozzle deflection is very crucial, which can provide significant information for the suppression of the infrared radiation property of the 2D-CD vectoring exhaust system. In this paper, by means of computational fluid dynamics, the fluid dynamic and infrared radiation characteristics of the 2D-CD vectoring exhaust system are studied at subsonic cruise status with nozzle deflection angles from 0 to 20°, and the results are compared with those of the baseline axisymmetric exhaust system. The results indicate that the fluid dynamic performance of a properly designed 2D-CD vectoring exhaust system is equivalent to the fluid dynamic performance of the baseline axisymmetric exhaust system. When the nozzle deflection angle is less than 5°, the mass flow and thrust force of the 2D-CD vectoring exhaust system are almost unchanged, and with the increase of the nozzle deflection angles, the mass flow and thrust force decrease rapidly. The thrust force deflection angles lag behind the nozzle deflection angles all the time, and as the nozzle deflection angle increases, the difference between them decreases. The direction of the maximum infrared radiation of the 2D-CD vectoring exhaust system deflects with the deflection of the nozzle, and the mean integrated infrared radiation intensity of the exhaust system decreases with the increase of nozzle deflection angles.

Impact of Background Radiation on the Long Wave Infrared Radiation Characteristics of Aircraft at High Altitude

2016 ◽  
Vol 66 (1) ◽  
pp. 51 ◽  
Author(s):  
Wei Huang ◽  
Hong-hu Ji
Keyword(s):  
Infrared Radiation ◽  
Horizontal Plane ◽  
Background Radiation ◽  
Reverse Monte Carlo ◽  
Radiance Temperature ◽  
Radiation Characteristics ◽  
Long Wave ◽  
The Impact ◽  
Long Wave Infrared ◽  
Tracing Method

<p class="maintext">Reflected background infrared radiation is an important contributor to the aircraft total infrared radiation. A reverse Monte Carlo ray tracing method to compute the infrared radiation signature of aircraft was introduced. The impact of atmospheric and ground radiation on the long wave infrared radiation signature of aircraft at the altitude of 11 km is analysed. The flight speed is Mach 0.8. The horizontal detection directions, downward detection directions and upward detection directions are considered. The results show that in the horizontal plane, the ratio of reflected background infrared radiation to self infrared radiation is about 10 per cent in summer, and 7 per cent in winter; the ratio values distributed in the front and side of the aircraft are bigger than that in the rear; and the existence of atmospheric and ground infrared radiation makes the apparent radiance temperature of the lower part of the aircraft higher than that of the upper part of the aircraft.</p><p class="maintext"><strong>Defence Science Journal, Vol. 66, No. 1, January 2016, pp. 51-56, DOI: http://dx.doi.org/10.14429/dsj.66.8090</strong></p>

Study on the Influence of Film Cooling on the Flow Field and Infrared Radiation Characteristics in the Divergent Section of a Nozzle

2020 ◽  
Author(s):  
Haoqi Yang ◽  
Qingzhen Yang ◽  
Saile Zhang ◽  
Huicheng Yang ◽  
Yubo He
Keyword(s):  
High Temperature ◽  
Flow Field ◽  
Infrared Radiation ◽  
Film Cooling ◽  
Exhaust System ◽  
Line Pattern ◽  
Radiation Characteristics ◽  
Core Zone ◽  
The Core ◽  
Significant Difference

Abstract As the last part of the convergent divergent nozzle, the divergent section is exposed to high temperature and high-speed airflow and thus, it is more easily to be detected by the infrared detector. It is one of the main sources of the infrared radiation in the exhaust system. Film cooling is applied to protect the wall from hot flow and reduce the infrared radiation. In this paper, the study is conducted on a nozzle with spherical convergence flap in a turbofan engine exhaust system. The effect of film cooling on the internal flow and infrared radiation characteristics of the exhaust system in the divergent section was studied by numerical simulations. The k-ω SST turbulence model was used to simulate the flow field, and the Reverse Monte Carlo Method was employed to calculate the infrared radiation characteristics of the nozzle. Four different kinds of film hole arrangements are involved, they are cylindrical film holes in an in-line pattern, cylindrical film holes in a staggered pattern, converging-expanding film holes in an in-line pattern and converging-expanding film holes in a staggered pattern. The cylindrical film hole and the converging-expanding film hole have a round shape inlet, with an equivalent diameter of d = 5mm on the projection surface perpendicular to the axial direction. Angles between each film hole and the wall surface are 35°. The impact of the heat conduction on the wall was taken into account. The results show that with the given mass flow rate of the coolant, the lengths of the high temperature core zone of the four models with different film cooling structures are slightly shorter than the core zone of the model without cooling structures. However, no significant difference can be found for the length of the core zone of the four models. The average temperature of the wall in the divergent section decreases significantly by using film cooling. No significant difference can be found in the wall temperature distribution for the four models. In the 3∼5μm and 8∼14μm bands, the cooling technique barely affects the infrared radiation of the main exhaust jet flow, while it significantly reduces the infrared radiation of the solid wall in the divergent section, and the decreasing amplitude is from 45% to 51%. Different film hole arrangements result in similar effects on the infrared radiation of the nozzle. Overall, the usage of film cooling in the divergent section of the nozzle effectively reduces the averaged wall temperature and substantially suppresses the solid infrared radiation on the wall. However, the shape and arrangement of the film holes have no significant influence on the infrared radiation intensity and temperature of the wall in the divergent section.

Numerical Simulation of Supersonic Aircraft Surface Aerodynamic Heating and Infrared Radiation Characteristics

2013 ◽  
Vol 444-445 ◽  
pp. 1234-1238
Author(s):  
Pei Ran Su ◽  
Qi Tai Eri ◽  
Xi Xi Li
Keyword(s):  
Infrared Radiation ◽  
Aerodynamic Heating ◽  
Cruise Missile ◽  
Surface Emissivity ◽  
Atmospheric Attenuation ◽  
Environmental Radiation ◽  
Radiation Characteristics ◽  
Supersonic Aircraft ◽  
Volume Method ◽  
Reverse Monte Carlo Method

The aerodynamic heating and infrared radiation characteristics of BrahMos supersonic cruise missile were investigated. The aerodynamic heating was simulated using finite volume method, and the infrared radiation characteristics were simulated by reverse Monte Carlo method. Infrared radiation characteristics of missile surface were analyzed in different surface emissivity and flight altitudes, and the effects of environmental radiation and atmospheric attenuation were considered. The results show 8~14μm and 3~5μm environment radiation were approximately 10% and 2.4% of total radiation respectively, when the surface emissivity is 0.3. The proportion of environmental radiation reduces nearly half when the surface emissivity increases by 0.2.

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