Jet Engine Exhaust Research Articles

Resistance of Concrete with Various Types of Coarse Aggregate to Coupled Effects of Thermal Shocks and Chemicals.

Rigid pavements at military airfields experience surface deterioration within 6-18 months of construction. The cause of this degradation is mainly due to combined exposure to repeated heat shocks from jet engine exhaust and spilled aviation oils (hydrocarbons). Surface degradation occurs in the form of disintegration of aggregates and cement paste into small pieces that pose severe risks of physical injury to maintenance crews or damage to an aircraft engine. Since coarse aggregates typically occupy 60-80% of the concrete volume, aggregates' thermal properties and microstructure should play a crucial role in the degrading mechanism. At high temperatures, concrete with lightweight aggregates is reported to have better performance compared to concrete with normal-weight aggregate. Thus, the present study carried out a detailed investigation of the mechanical and thermal performance of lightweight aggregate concrete exposed to the combined effects of high temperatures and hydrocarbon oils simultaneously. To replicate harsh airfield operating conditions, standard-sized concrete cylinders were exposed to elevated temperatures using an electric oven. Additionally, a mixture of equal parts of aircraft engine oil, hydraulic oil, and kerosene was applied before each exposure to high temperatures. To identify the resistance of different concrete with various lightweight coarse aggregates, pumice, perlite, lytag (sintered fly ash), and crushed brick were used as lightweight coarse aggregates in concrete. Also, basalt aggregate concrete was used as a reference. After curing, cylinders were tested for the ultimate strength. Later, after every 20 cyclic exposures, three cylinders from each aggregate type were tested for residual comprehensive strength, thermal, chemical, and microstructural (SEM) properties. Overall, concrete with crushed brick aggregate and lytag used in this study showed superior resistance to the simulated airfield conditions. The findings of this study will provide valuable insights to select an appropriate coarse aggregate type for military airfield pavement construction, aiming to effectively minimize surface spalling.

Propagation Characteristics of a Partially Coherent Gaussian Schell‐model Array Vortex Beam in the Joint Turbulence Effect of a Jet Engine and Atmosphere

AbstractThis work investigates the joint effects of jet engine exhaust‐induced turbulence and atmospheric turbulence on the propagation of a partially coherent Gaussian Schell‐model Array (GSMA) vortex beam. Using the two‐process propagation method, analytical formulae are derived for the cross‐spectral density, spectral density, degree of coherence, and beam width of the considered beam. The results show that the considered beam takes different shapes; when the spatial coherence is large, the spectral density of the GSMA vortex beam takes an elliptical shape, whereas when the spatial coherence is smaller, the spectral density remains a Gaussian shape. The evolution profile of the degree of coherence weakens gradually when the propagation distance, topological charge, and turbulence strength increase. Moreover, the profile of the degree of coherence takes the Gaussian profile when the propagation distance is longer or turbulence atmospheric is stronger. Furthermore, the results reveal that the corresponding beam spreads faster with a larger propagation distance, lower spatial coherence, and high‐strength turbulence. This study also concludes from the results that the beam is affected more when its propagation is near the jet engine exhaust, which means that this latter has a significant impact.

Laser Beam Quality of Airy Beam in the Jet Engine Exhaust Induced Turbulence

Theoretical predictions of laser beam interactions with jet-engine-exhaust-induced turbulence are of importance for optimization of various optical systems, including LIDARs and airborne laser measurement systems. This paper is based on the extended Huygens–Fresnel diffraction integral and the Wigner distribution function, combined with the recently proposed power spectral density function of atmospheric turbulence induced by jet engine exhaust, to derive the formula for the quality factor of a partially coherent Airy beam in turbulent media induced by jet engine exhaust. Numerical calculations based on the analytical formula show that the smaller the structure constant and outer scale of the atmospheric turbulence induced by jet engine exhaust, the smaller the quality factor of a partially coherent Airy beam, indicating better laser beam quality. At the same time, the larger the generalized parameter and inner scale of the jet-engine-exhaust-induced turbulence and the longer the wavelength of the laser beam, the smaller the corresponding quality factor. The numerical results also show that reducing the coherence length of a partially coherent Airy beam and increasing its characteristic width are beneficial for reducing the quality factor in the atmospheric turbulence induced by jet engines. However, the numerical results show that increasing the coherence length of a partially coherent Airy beam and reducing its characteristic width are beneficial for reducing the quality factor in vacuum. This situation demonstrates significant differences between the interaction mechanisms of an Airy beam in vacuum and in the jet-engine-exhaust-induced turbulence. The results of our discussion contribute to clarifying the mechanism of interaction between an Airy laser beam and random media, as well as the application of a curved Airy laser beam in practical situations.

Propagation of Gaussian Schell-Model Array Beams through a Jet Engine Exhaust

Here a Gaussian Shell Model Array (GSMA) beam is used to investigate the propagation characteristics in the jet engine exhaust region. It has great significance to improve various optical systems for wide application in trapping cold atoms, creating gratings, and atmospheric optical communication. We calculate analytical formulas for the spectral density (SD) and the propagation factors Mx2 and My2 of a GSMA beam. The influence of inner scale of turbulence in the jet engine exhaust region on its power spectrum has been also analyzed. According to these results, the influence of turbulence in a jet engine exhaust on a GSMA beam has been reduced by changing the parameters of light source and turbulence. For example, it is an excellent tool for mitigation of the jet engine exhaust-induced anisotropy of turbulence to increase the source coherence length, the root-mean-squared (rms) beam width, the wavelength or reduce the outer scale of turbulence.

EXPERIMENTAL STUDY OF THE ACOUSTIC INTERACTION OF A SUBSCALE ROCKET NOZZLE EXHAUST JET AND DIFFERENT GUIDE TUBES

The noise emission of rocket engine test facilities and their impact on the environment comes more and more into focus. The key drivers are the engine exhaust jet itself, and its interaction or even coupling with a subsequent guide tube. To increase understanding of the interaction, and in preparation of future test facility design, a cold gas subscale test campaign was conducted with a reference guide tube. It was found that the main influencing parameter is the distance between the nozzle exit and guide tube inlet. This article is published with the permission of the authors granted to 3AF - Association Aéronautique et Astronautique de France (www.3AF.fr) organizer of the Space Propulsion International Conference.

A study of effects of a turbulent jet engine exhaust on partially coherent Laguerre-Gaussian Schell model vortex beam

In this study, based on the generalized Huygens-Fresnel principle, the evolution properties, such as spectral density, degree of coherence, and beam width of the propagation of partially coherent Laguerre-Gaussian Schell model vortex beam (PCLGSMvB) in jet engine exhaust are studied. Our results show that the spectral density of the corresponding beam can change their form shape during its propagation as the source coherence varies. When the source coherence width is high, the profile of PCLGSMvB changes from initially dark hollow into two spot beams at short propagation distances. If the source coherent width is very small, the shape of PCLGSMvB is converted to a Gaussian shape and keeps its form upon propagation. Also, we found that the spreading of PCLGSMvB is related with their initial parameters, and it will be spread faster with smaller source coherence width, larger mode order n, and longer wavelength. Furthermore, the beam width of the PCLGSMvB increasing as the structural constant increases and it means that the beam can resist to stronger fluctuation of turbulence. Outputs of this study has potential application on deriving the requirements of optical systems on aircrafts like laser range finder, laser designator, optical communication systems and directed infrared countermeasure (DIRCM).

Elemental analysis of aircraft engine smoke number filter samples with micro-PIXE

To extract information on elemental components and PM characteristics from smoke number (SN) filter paper, we were performed elemental analysis by micro-PIXE. As a result of elemental analysis of the SN filter, information on the elemental composition of jet engine exhaust PM was obtained. Regarding the SN filter, jet engine exhaust PM have been collected for each difference in engine thrust of various aircraft engines at aircraft turbine engines test cells around the world. By periodically analyzing the elemental composition of such the SN filter, it is possible to grasp the characteristics of the emission PM of each aircraft engine and the transformation of the elemental composition of the emission PM with the passage of time of the jet engine. This was thought to lead to the evaluation of jet engine.

Comparative Study of Uniform and Graded Meshes for Solving Convection-Diffusion Equation with Quadratic Source

Due to its fundamental nature, the problems of convection-diffusion are discussed in various aviation, science and engineering applications. Among major applications are in the study of the dynamics of aircraft wake vortex and its interaction with turbulent jet which is a very serious hazard in aviation. Other applications include those in the investigation of intrusive sampling of jet engine exhaust gases, and the effectiveness of hot fluid injection in the removal of ice on aircraft wings. The numerical solutions of convection-diffusion require propermeshing schemes. Among major meshes in computational fluid dynamics are those of uniform, piecewise-uniform, graded, and hybrid over which the solutions of discretized governing equations are found. Bad solutions as spurious fluctuations, over-or under-predictions, and excessive computation time might be the results of unwitting application of the meshes. Accentuating comparative effectiveness of two meshes, namely uniform mesh and graded mesh with mesh expansion factor, this paper takes the solution of aconvection-diffusion equation with quadratic source term into account. The problem is solved by assigning several values of mesh expansion factor to graded mesh, while mesh number is kept constant. The factors are calculated based on the generalization oftheir logarithmically linear relationship with low Peclet numbers derived in previous work. Based on the values of Peclet number, five test cases are considered. Graded mesh is proven relatively more robust, particularly due the solution on the mesh beingfree from spurious fluctuation. Furthermore, the accuracy level of the solution of up to two order of magnitude higher is obtained. The mesh expansion factor therefore contributes to a stable and highly accurate solution corresponding to all interested Peclet numbers.

Partially coherent laser beams propagating in jet engine exhaust induced turbulence

Partially coherent laser beams propagating in jet engine exhaust induced turbulence

The Effects of the Use of Algae and Jatropha Biofuels on Aircraft Engine Exhaust Emissions in Cruise Phase

Due to environmental pressure and the prevailing political and economic situation in the world, alternatives to traditional fossil fuels are being sought. The use of bio-derived fuels may reduce the emission of pollutants present in jet engine exhausts. The presented research investigates the possibility of replacing the conventional fuel, which is kerosene, with plant-derived fuels from marine algae and jatropha. During the analysis, based on the available data, the emission indices of pollutants were computed, and then, for the adopted aircraft and route, the emissions for kerosene and alternative fuels were determined. A significant reduction in the emission of most analyzed compounds (even by 40% for CO) was achieved compared to the emission for kerosene. The obtained results are discussed in the conclusion section.

Propagation of Bessel-Gaussian Shell-model beam through a jet engine exhaust turbulence

Propagation of Bessel-Gaussian Shell-model beam through a jet engine exhaust turbulence

Experimental and numerical investigation on the effect of turboprop engine exhaust gas impingement on pusher aircraft

Abstract Turboprop engines require an exhaust nozzle or stub to duct the engine exhaust flue gas outboard of the aircraft. The design of these exhaust stubs are dictated primarily by the aircraft’s configuration. In pusher aircraft, the exhaust stubs are designed to minimize the exposure of the flue gases from the engine exhaust on the propeller blades and fuselage. A fluid-thermal-structure coupling analysis is performed to understand the thermal effects of the engine exhaust jet flow on the thermo-mechanical behavior of pusher configured light transport aircraft propeller and structure. The steady thermal flow field of the aircraft with forward and reverse thrust, in which propeller blade angle variations were analyzed for different aircraft speed. The present work investigates a three-dimensional analysis of flow around the nacelle-airframe and the effect of exhaust flue gas impingement on the propeller blade surface. Based on the insights from the numerical results, the designed exhaust duct was integrated on the aircraft and carried out ground static and flight testing for various flight operating conditions in which propeller blade and fuselage surface temperature were measured. Numerical and experimental results are compared and validated for certain flight conditions and found satisfactory.

Propagation of the Laguerre-Gaussian correlated Shell-model beams through a turbulent jet engine exhaust

Propagation of the Laguerre-Gaussian correlated Shell-model beams through a turbulent jet engine exhaust

Corrections to “Propagation Properties of Gaussian Schell-Model Beam Array in the Jet Engine Exhaust Induced Turbulence” [Dec 20 Art no. 6501113

We correct a few typographical errors in the original manuscript.

Information on elemental and ionic components obtained from aircraft engine smoke number filter sample

To extract information on elemental and ionic species components and particulate matter (PM) characteristics from smoke number (SN) filter paper, we were performed elemental analysis by micro-PIXE and ion component analysis by ion chromatography. As a result of elemental and ionic species component analysis of the SN filter, information on the chemical composition of jet engine exhaust PM was obtained. Regarding the SN filter, jet engine exhaust PM was collected for each difference in engine thrust of various aircraft engines at aircraft turbine engine test cells around the world. By periodically analyzing the chemical composition of the SN filter, it is possible to identify the characteristics of the emission PM of each aircraft engine and the transformation of the chemical composition of the emission PM with the passage of time. This was thought to lead to the evaluation of jet engines.

Propagation Properties of Gaussian Schell-Model Beam Array in the Jet Engine Exhaust Induced Turbulence

The effects of the jet engine turbulence on a Gaussian Schell-Model (GSM) beam array propagating in a jet engine plume are studied theoretically. The analytical expressions of the cross-spectral density (CSD) function, the spectral degree of coherence (DOC) and the mean-squared beam width for a GSM beam array propagating through a jet engine plume region are derived based on the extended Huyens-Fresnel integral. It is found that the profile of spectral density and the DOC of a GSM beam array gradually transfer to an elliptical shape as the propagation distance increases, and the elliptical degree becomes greater with increasing source coherence length. Besides, as the source coherence length decreases, the effect of the jet engine turbulence on the beam broadening is smaller and the profile of the DOC appears sidelobes at short distance. It is also found that the values of effective coherence width nearly remain the same for different values of source coherence length after propagating a certain distance. Furthermore, the effects of the number of beamlets on the beam width and effective coherence width are investigated in detail.

MODEL OF EMISSION OF EXHAUST COMPOUNDS OF JET AIRCRAFT IN CRUISE PHASE ENABLING TRAJECTORY OPTIMIZATION

Nowadays, air transport is the most modern and the most dynamically developing branch of transport. This intensive development of air transport causes the continuous increase in emissions of pollutants, mainly greenhouse gases, leading to the deepening of the greenhouse effect, which in turn leads to irreversible global climate change. In order to optimize air communication and make it even more economical and environmentally friendly, such activities as e.g. SESAR project are undertaken. One of the parts of this project is the research on minimizing fuel consumption and emissions of pollutants in jet engine exhausts. The paper presents a developed model of emission and main pollutants (NOx, CO, HC and CO2) in the exhausts of jet engines of a passenger aircraft during a cruise phase. Applying simple optimization tools, such as e.g. the Dijkstra’s algorithm, this model was verified by the optimization of a trajectory of a jet aircraft in a cruise phase on an exemplary route in terms of minimizing emission of selected harmful compounds in jet engines exhausts. To meet the aim of the research, it was necessary to develop a computer program that determines a two-dimensional grid graph, assigns its appropriate weights to its edges and passing along these edges, determines the optimal trajectory of a given flight between two indicated start and end vertices. The developed research methodology is universal and can be applied for any jet passenger aircraft.

Propagation of Gaussian Schell-model beams through a jet engine exhaust.

Theoretical predictions of light beam interactions with jet engine exhaust are of importance for optimization of various optical systems, including LIDARs, imagers and communication links operating in the vicinity of aircrafts and marine vessels. Here we extend the analysis previously carried out for coherent laser beams propagating in jet engine exhaust, to the broad class of Gaussian Schell-Model (GSM) beams, being capable of treating any degree of coherence in addition to size and radius of curvature. The analytical formulas for the spectral density (SD) and the spectral degree of coherence (DOC) of the GSM beam are obtained and analyzed on passage through a typical jet engine exhaust region. It is shown that for sources with high coherence, the transverse profiles of the SD and the DOC of the GSM beams gradually transition from initially circular to elliptical shape upon propagation at very short ranges. However, such transition is suppressed for sources with lower coherence and disappears in the incoherent source limit, implying that the GSM source with low source coherence is an excellent tool for mitigation of the jet engine exhaust-induced anisotropy of turbulence. The physical interpretation and the illustration are included.

Analysis of the Impact of Changes in Flight Speed and Altitude on Emission Indexes of Pollutants in Jet Engine Exhausts

Abstract In currently implemented international aviation strategies and programs, including those realised under the European Union policy, such as Clean Sky, SES, SESAR and, CORSIA, the environmental aspect is particularly prominent – reducing the emission of all gaseous pollutants, and from 2020 also particulate matter. Therefore, it is important to know how the change in flight parameters (altitude, speed) affects the emission of pollutants in jet engine exhausts. Such information will enable to adjust the flight altitude of the aircraft when ecological aspect is taken into consideration. In addition to the operating condition (altitude, flight speed, range of power or thrust), the amount and type of pollutants emitted depends on the type of aircraft, its aerodynamic characteristics, engine type and as well as on the type of fuel used. The impact of changes in aircraft flight parameters (speed and altitude) on the performance of a bypass jet engine and the emission of pollutants in its exhausts is analysed in the paper. For this purpose, the speed-altitude characteristics of such an engine were determined. Next, the emission indexes (EI) for the LTO phase taken from the ICAO database were used to determine the emission indexes corresponding to given parameters of both the engine operation and the aircraft flight. For selected speeds and cruising altitudes, the value of thrust required for the flight of the aircraft was determined and to this value, the engine operation range was assigned as well the corresponding pollutant emission indexes. This allowed to calculate the mass of pollutants emitted per unit of time for given flight parameters. The results obtained are presented in the graphs and discussed.

Analysis of the Wind Dependent Duration of the Cruise Phase on Jet Engine Exhaust Emissions

Analysis of the Wind Dependent Duration of the Cruise Phase on Jet Engine Exhaust Emissions