Aircraft Exhaust Plumes Research Articles

Integrated Infrared Radiation Characteristics of Aircraft Skin and the Exhaust Plume.

Infrared radiation (IR) characteristics are important parameters for detecting, identifying, and striking military targets in the context of systematic countermeasures. Accurate calculation of IR characteristics for aircraft is significant for the simulation of war situations and the designation of combat strategy. In this work, integrated IR characteristics of aircraft skin and exhaust plume and their interaction are investigated by considering the reflection based on a bi-directional reflectance distribution function and various influence factors such as solar irradiation, ground reflection, aerodynamic heating, and projection radiation from the background. Combined with infrared emission and reflection characteristics of the skin, omnidirectional IR intensity distributions of 3-5 μm and 8-14 μm at different Mach numbers are obtained. The exhaust plume IR characteristic for different waves and wavebands are also investigated by considering the presence or absence of base and the difference in nozzle inlet temperature. On this basis, integrated IR characteristics between the skin and exhaust plume are investigated. Results show that aircraft IR characteristics of 3-5 μm are concentrated in the exhaust plume and high-temperature skin near the exhaust plume, while the signals of 8-14 μm are concentrated in the skin. The research results are expected to supply guidance for better detection and identification of typical flight targets.

Review: Particulate Matter Emissions from Aircraft

The contribution of aircraft operations to ambient ultrafine particle (UFP) concentration at and around airports can be significant. This review article considers the volatile and non-volatile elements of particulate matter emissions from aircraft engines, their characteristics and quantification and identifies gaps in knowledge. The current state of the art emission inventory methods and dispersion modelling approaches are reviewed and areas for improvement and research needs are identified. Quantification of engine non-volatile particulate matter (nvPM) is improving as measured certification data for the landing and take-off cycle are becoming available. Further work is needed: to better estimate nvPM emissions during the full-flight; to estimate non-regulated (smaller) engines; and to better estimate the emissions and evolution of volatile particles (vPM) in the aircraft exhaust plume. Dispersion modelling improvements are also needed to better address vPM. As the emissions inventory data for both vPM and nvPM from aircraft sources improve, better estimates of the contribution of aircraft engine emissions to ambient particulate concentrations will be possible.

Particle Layer Effects on Flowfield and Infrared Characteristics of Aircraft Exhaust Plume

Most existing plume infrared (IR) suppression techniques are difficult to apply to an already established aircraft system and cannot be applied in an active way. As an alternative solution, the present study explores an active technique for shielding IR signals by injecting particles into the engine exhaust plume. A Eulerian–Lagrangian-based discrete phase method was used to calculate a multiphase flow composed of exhaust gas and injected particles. To analyze the characteristics of thermal flow and particle distribution under flight conditions, a cruise condition of Mach number 0.7 at an altitude of 20,000 ft was considered. Water droplets and carbon particles with diameters of 5 and were considered, and placed randomly within the particle layer. To analyze the shielding effect according to particle size, material type, and distribution pattern, the transmittance of IR electromagnetic waves of wavelength was analyzed using a Maxwell multilevel fast multipole method. When the total mass was kept the same, water droplets in wavelength bands below , and water droplets or carbon particles in wavelength bands above were more effective for shielding. If the single-layer transmittance information obtained in the present study is extended to actual particle layers of several tens of centimeters, it is expected that the shielding effect will be significantly higher.

Large eddy simulation of aerosol particle dispersion mechanism in aircraft exhaust plume

Aerosol Infrared Stealth Technology is a novel method to suppress the infrared by releasing aerosol particles around the hot exhaust plume. However, the Infrared Radiation (IR) suppression rate is much lower in flight tests, which is caused by the unclear particle dispersion mechanism in high-speed non-isothermal shear flow. Hence, the large eddy simulation (LES) and particle discrete phase model (DPM) are coupled to solve the turbulent shear flow and the aerosol particle motion. The effects of aircraft flight speed on the turbulent flow characteristics and particle motion behaviors are systematically studied. It is found that the Mach rings appear in flight conditions, and they are getting blurry when increasing the flight speed. Both γ-like vortex and horseshoe-like vortex are observed when Ma < 1, and the horse-like could disappear when Ma > 1. The aerosol particle distribution is closely related to the turbulent gas vortices. The particle lateral dispersion is obviously restricted with the rising flight speed. Besides, the drag force plays a dominant role, the Saffman force and the thermophoretic force are of the same order of magnitude, all of these three forces are much greater than the gravity.

Characteristics of sub-10 nm particle emissions from in-use commercial aircraft observed at Narita International Airport

Abstract. The characterization of ultrafine particle emissions from jet aircraft equipped with turbofan engines, which are commonly used in civil aviation, is an important issue in the assessment of the impacts of aviation on climate and human health. We conducted field observations of aerosols and carbon dioxide (CO2) near a runway at Narita International Airport, Japan, in February 2018. We used an ultrafine condensation particle counter (UCPC) and a condensation particle counter (CPC) with unheated and 350 ∘C heated operation modes to investigate the contributions of sub-10 nm size ranges to the total and the non-volatile particle number concentrations. The performance of the 350 ∘C heated mode was tested in the laboratory to verify the consistency with existing methods for non-volatile particle measurements. We also used a scanning mobility particle sizer with unheated and 350 ∘C heated modes and an engine exhaust particle sizer for the measurements of particle number size distributions. Spiked increases in the particle number concentrations and CO2 mixing ratios were observed to be associated with the directions of wind from the runway, which can be attributed to diluted aircraft exhaust plumes. We estimated the particle number emission indices (EIs) for discrete take-off plumes using the UCPC, CPC, and CO2 data. The median values of the total and the non-volatile particle number EIs for diameters larger than 2.5 nm as derived from the UCPC data were found to be 1.1×1017 and 5.7×1015 kg per fuel, respectively. More than half the particle number EIs were in the size range smaller than 10 nm for both the total and the non-volatile particles in most of the cases analyzed in this study. The significance of sub-10 nm size ranges for the total particles in the diluted plumes was qualitatively consistent with previous studies, but that for the non-volatile particles was unexpected. Possible factors affecting the similarities and differences compared with the previous findings are discussed.

Optimal calculation method of aircraft infrared physical imaging simulation

In order to meet the needs of high-precision simulation images in the development process of infrared imaging detection system, the infrared physical imaging radiation transmission model for aircraft was established, and the ray tracing method was used to realize the simulation calculation of radiance image. Aiming at the difference between the reflection characteristics of the aircraft skin and the distribution characteristics of the radiation source, an optimization method for skin radiance calculation using direct lighting multi-importance sampling was proposed. Aiming at the characteristics of strong emission ability and weak extinction ability of aircraft exhaust plume, an optimization method for exhaust plume radiance calculation using combining integration was proposed. The correctness and effectiveness of the physical imaging model and calculation optimization method were verified through simulation experiments. The relative error of the skin radiation calculation is better than 0.05%, and the relative error of the tail flame radiation calculation is better than 0.1%. Compared with the traditional ray tracing method, the calculation optimization method has a faster convergence speed and stronger adaptability. Infrared imaging simulation and radiation characteristics analysis of stealth aircraft were carried out. The simulation results show that infrared stealth technology can reduce the radiation intensity in the mid-waveband and long-waveband, and increase the reflected radiation intensity in the short-waveband.

A narrow-band k-distribution model with single mixture gas assumption for radiative flows

In the present study, the narrow-band k-distribution (NBK) model parameters for mixtures of H2O, CO2, and CO are proposed by utilizing the line-by-line (LBL) calculations with a single mixture gas assumption. For the application of the NBK model to radiative flows, a radiative transfer equation (RTE) solver based on a finite-volume method on unstructured meshes was developed. The NBK model and the RTE solver were verified by solving two benchmark problems including the spectral radiance distribution emitted from one-dimensional slabs and the radiative heat transfer in a truncated conical enclosure. It was shown that the results are accurate and physically reliable by comparing with available data. To examine the applicability of the methods to realistic multi-dimensional problems in non-isothermal and non-homogeneous conditions, radiation in an axisymmetric combustion chamber was analyzed, and then the infrared signature emitted from an aircraft exhaust plume was predicted. For modeling the plume flow involving radiative cooling, a flow-radiation coupled procedure was devised in a loosely coupled manner by adopting a Navier-Stokes flow solver based on unstructured meshes. It was shown that the predicted radiative cooling for the combustion chamber is physically more accurate than other predictions, and is as accurate as that by the LBL calculations. It was found that the infrared signature of aircraft exhaust plume can also be obtained accurately, equivalent to the LBL calculations, by using the present narrow-band approach with a much improved numerical efficiency.

Aviation Emissions Impact Ambient Ultrafine Particle Concentrations in the Greater Boston Area.

Ultrafine particles are emitted at high rates by jet aircraft. To determine the possible impacts of aviation activities on ambient ultrafine particle number concentrations (PNCs), we analyzed PNCs measured from 3 months to 3.67 years at three sites within 7.3 km of Logan International Airport (Boston, MA). At sites 4.0 and 7.3 km from the airport, average PNCs were 2- and 1.33-fold higher, respectively, when winds were from the direction of the airport compared to other directions, indicating that aviation impacts on PNC extend many kilometers downwind of Logan airport. Furthermore, PNCs were positively correlated with flight activity after taking meteorology, time of day and week, and traffic volume into account. Also, when winds were from the direction of the airport, PNCs increased with increasing wind speed, suggesting that buoyant aircraft exhaust plumes were the likely source. Concentrations of other pollutants [CO, black carbon (BC), NO, NO2, NOx, SO2, and fine particulate matter (PM2.5)] decreased with increasing wind speed when winds were from the direction of the airport, indicating a different dominant source (likely roadway traffic emissions). Except for oxides of nitrogen, other pollutants were not correlated with flight activity. Our findings point to the need for PNC exposure assessment studies to take aircraft emissions into consideration, particularly in populated areas near airports.

복사 데이터베이스를 활용한 항공기 배기 플룸 IR 신호 해석

복사 데이터베이스를 활용한 항공기 배기 플룸 IR 신호 해석

Measurements of a micro gas turbine plume and data reduction for the purpose of infrared signature modeling

An important issue concerning numerical simulation of gas turbine-propelled aircraft in infrared scenarios (usually in military applications) is the radiometric emission properties of the aircraft exhaust plume. In this paper, a detailed description of the experimental setup and the measurement results of the infrared signature properties of a micro turbine engine plume at ground level (with an altitude of approximately 1500 m above sea level) are presented. The main instruments used were a midwave (3-6 μm) infrared camera and a spectroradiometer (0.8-5.5 μm). The wideband emission properties were investigated with the camera as a function of the aspect angle between the camera's field of view and the plume's longitudinal axis, while maintaining a fixed engine rotational speed, as well as a function of the engine rotational speed for a fixed aspect angle of 90°. The spectral emission was investigated with the spectroradiometer as a function of three regions along the plume for a small instrument field of view and fixed engine setting. These measurements comprise the radiometric characterization of a micro gas turbine exhaust plume that, after data reduction, allows numerical modeling of this type of plume in a computer simulation. Such measurements, or the model based on it, are useful in conceptual studies regarding the infrared signatures of a turbine gas plume. It is in principle also possible to construct an infrared radiometric model of a larger-scale turbine engine's plume based on these characteristics.

The microphysical pathway to contrail formation

AbstractA conceptual framework to predict microphysical and optical properties of contrail particles within a wingspan behind the source aircraft is developed. Results from two decades of contrail observations and numerical simulations are reviewed forming the basis of theoretical model development. The model utilizes cloud theory applied to the dynamics and thermodynamics of jet aircraft exhaust plumes in upper tropospheric conditions. Droplet nuclei include soot particles emitted from aircraft engines and atmospheric particles entrained into the plume. These precursor particles activate into copious homogeneously freezing water droplets as the plume relative humidity rises beyond liquid water saturation. A unimodal size spectrum of ice particles develops wherein ice particles grow to micrometer mean sizes. Contrail particle formation is analyzed over a wide range of soot emissions relating to conventional jet fuels as well as to alternative aviation fuels producing much less soot and volatile particle emissions. For current aviation fuels and propulsion technology, the number of contrail ice particles scales roughly in proportion to the number of emitted soot particles that act as water condensation nuclei despite their poor hygroscopicity. Close to the contrail formation threshold, only few plume particles can be water activated and freeze. Implications for effects of alternative fuels on contrails, an arena for future scientific exploration, are outlined.

항공기 배기 플룸의 파장별 IR 신호 해석

Infrared signature of aircraft exhaust plume is the critical factor for aircraft survivability. To improve the military aircraft survivability, the accurate prediction of infrared signature for the propulsion system is needed. The numerical analysis of thermal fluid field for nozzle inflow, free stream flow, and plume region is conducted by using the in-house code. Weighted Sum of Gray Gases Model based on Narrow Band with regrouping is adopted to calculate the spectral infrared signature emitted from aircraft exhaust plume. The accuracy and reliability of the developed code are validated in the one-dimensional band model. It is found that the infrared radiant intensity is relatively more strong in the plume through the analysis, the results show the different characteristic of the spectral infrared signature along the temperature, the partial pressure, and the species distribution. The continuous spectral radiant intensity is shown near the nozzle exit due to the emission from the nozzle wall.

Dimension of aircraft exhaust plumes at cruise conditions: effect of wake vortices

Abstract. The dispersion of aircraft emissions during the vortex phase is studied using a 3-D LES model with Lagrangian particle tracking. The simulations start with a fully rolled-up vortex pair of a type B747/A340 airplane and the tracer centred around the vortex cores. The tracer dilution and plume extent is studied for a variety of ambient and aircraft parameters until aircraft-induced effects have ceased. For typical upper tropospheric conditions, the impact of stratification is more dominant compared to turbulence intensity or vertical wind shear. Moreover, the sensitivity to the initial tracer distribution was found to be weak. Along the transverse direction, the tracer concentrations can be well approximated by a Gaussian distribution, along the vertical a superposition of three Gaussian distributions is adequate. For the studied parameter range, the vertical plume expansion ranges from 400 m to 550 m and cross-sectional area from 4.0 × 104 m2 to 6 × 104 m2 after six minutes. For validation, selected simulations were compared to an alternative LES model and to in-situ NO-measurements.

Uptake of HNO3 on Aviation Kerosene and Aircraft Engine Soot: Influences of H2O or/and H2SO4

The uptake of HNO3 on aviation kerosene soot (TC-1 soot) was studied in the absence and presence of water vapor at 295 and 243 K. The influence of H2SO4 coating of the TC-1 soot surface on HNO3 uptake was also investigated. Only reversible uptake of HNO3 was observed. HONO and NO2, potential products of reactive uptake of HNO3, were not observed under any conditions studied here. The uptake of nitric acid increased slightly with relative humidity (RH). Coating of the TC-1 soot surface with sulfuric acid decreased the uptake of HNO3 and did not lead to displacement of H2SO4 from the soot surface. A limited set of measurements was carried out on soot generated by aircraft engine combustor (E-soot) with results similar to those on TC-1 soot. The influence of water on HNO3 uptake on E-soot appeared to be more pronounced than on TC-1 soot. Our results suggest that HNO3 loss in the upper troposphere due to soot is not significant except perhaps in aircraft exhaust plumes. Our results also suggest that HNO3 is not converted to either NO2 or HONO upon its uptake on soot in the atmosphere.

Impact of aircraft plume dynamics on airport local air quality

Air quality degradation in the locality of airports poses a public health hazard. The ability to quantitatively predict the air quality impacts of airport operations is of importance for assessing the air quality and public health impacts of airports today, of future developments, and for evaluating approaches for mitigating these impacts. However, studies such as the Project for the Sustainable Development of Heathrow have highlighted shortcomings in understanding of aircraft plume dispersion. Further, if national or international aviation environmental policies are to be assessed, a computationally efficient method of modeling aircraft plume dispersion is needed. To address these needs, we describe the formulation and validation of a three-dimensional integral plume model appropriate for modeling aircraft exhaust plumes at airports. We also develop a simplified concentration correction factor approach to efficiently account for dispersion processes particular to aircraft plumes. The model is used to explain monitoring station results in the London Heathrow area showing that pollutant concentrations are approximately constant over wind speeds of 3–12 m s−1, and is applied to reproduce empirically derived relationships between engine types and peak NOx concentrations at Heathrow. We calculated that not accounting for aircraft plume dynamics would result in a factor of 1.36–2.3 over-prediction of the mean NOx concentration (depending on location), consistent with empirical evidence of a factor of 1.7 over-prediction. Concentration correction factors are also calculated for aircraft takeoff, landing and taxi emissions, providing an efficient way to account for aircraft plume effects in atmospheric dispersion models.

비행조건에 따른 항공기 배기플룸의 IR 신호 특성

기술 수준에 의해 그 우위가 결정되는 현대 전장에서 항공기 플룸과 복사저부가열은 항공기의 생존성에 관련된 중요한 요인이다. 항공기의 생존성을 향상시키기 위해서는 저부가열, 그리고 항공기 플룸으로부터 방사되는 IR 신호가 감소되어야 한다. 본 연구에서는 IR 신호와 복사저부가열 특성을 고도 5km에서 마하수 0.9와 1.6의 조건으로 설정하여 플룸 내 유동 및 열복사 특성을 고찰하였다. 이를 통해 플룸에서의 IR 신호는 <TEX>$H_2O$</TEX>와 <TEX>$CO_2$</TEX>의 영향으로 인한 높은 방사특성을 확인하였다. 그리고 마하수가 높고 거리가 가까울수록 저부면에서의 복사열유속이 증가됨을 확인하였다. The IR signature and radiative base heating from an aircraft plume have been important factors for aircraft survivability in modern battle fields. In order to enhance the aircraft survivability and reduce the base heating, infrared signatures emitted from an aircraft exhaust plume should be determined. In this work, therefore, IR signatures and radiative base heating characteristics are examined in the plume exhausted from the aircraft with operating at altitude of 5 km in M=0.9 and 1.6, respectively. As a result, it is found that the particular wavelength IR signature has high spectral characteristics because of <TEX>$H_2O$</TEX> and <TEX>$CO_2$</TEX> gases in the plume, and the radiative heat flux coming into the base plane increases with higher Mach number and shorter distance.

입자에 의한 항공기 플룸의 열복사 가열에 관한 연구

유한체적법을 이용하여 설정된 가상의 노즐 조건에 따라 비행체 배기플룸의 SE와 PE에 의한 열복사 저부가열 해석 연구를 수행하였다. 저부면에서의 복사열유속을 얻기 위해 배기플룸은 흡수, 방사 및 산란하는 매질을 고려하였다. 저부면은 차가운 흑체이고 비회색가스와 입자의 복사 물성치는 회색가스가중합법(WSGGM)을 사용하였다. 후방 몬테카를로 방법을 사용한 기존의 연구와 비교하여 검증한 후, 입자의 농도, 온도, 그리고 등방성 또는 이방성 산란에 따른 복사저부가열을 해석하였다. 그 결과, 복사열유속은 노즐 출구와의 거리가 멀어지거나 비행 고도가 증가할수록 감소하고 입자의 온도가 높아질수록 복사열유속은 증가한다. 또한 전방산란은 PE를 증가시키고 후방산란은 SE를 증가시켰다. The finite volume method for radiation is applied for the analysis of radiative base heating by SE and PE of the aircraft exhaust plume. The exhaust plume is considered as an absorbing, emitting, and scattering medium, while the base plane is assumed to be cold and black. The radiative properties of non-gray gases are obtained through the WSGGM, and the particle is modelled as spheres. The present method is validated by comparing the results with those of the backward Monte-Carlo method and then the radiative base heating characteristics are analyzed by changing such various parameters as particle concentration, temperature, and scattering phase function. The results show that the radiative heat flux coming into the base plane decreases with altitude and distance, but it increases as the particle temperature increases. The forward scattering of particles increases PE while it decreases SE.

Measurements of HONO, NO, NOyand SO2in aircraft exhaust plumes at cruise

Measurements of gaseous nitrogen and sulfur oxide emissions in young aircraft exhaust plumes give insight into chemical oxidation processes inside aircraft engines. Particularly, the OHA¢Â�Â�induced formation of nitrous acid (HONO) from nitrogen oxide (NO) and sulfuric acid (H2SO4) from sulfur dioxide (SO2) inside the turbine which is highly uncertain, need detailed analysis to address the climate impact of aviation. We report on airborne in situ measurements at cruise altitudes of HONO, NO, NOy, and SO2 in 9 wakes of 8 different types of modern jet airliners, including for the first time also an A380. Measurements of HONO and SO2 were made with an ITCIMS (Ion Trap Chemical Ionization Mass Spectrometer) using a new ionA¢Â�Â�reaction scheme involving SF5 A¢Â�Â� reagent ions. The measured molar ratios HONO/NO and HONO/NOy with averages of 0.038 A�± 0.010 and 0.027 A�± 0.005 were found to decrease systematically with increasing NOx emissionA¢Â�Â�index (EI NOx). We calculate an average EI HONO of 0.31 A�± 0.12 g NO2 kgA¢Â�Â�1. Using reliable measurements of HONO and NOy, which are less adhesive than H2SO4 to the inlet walls, we derive the OHA¢Â�Â�induced conversion fraction of fuel sulfur to sulfuric acid with an average of 2.2 A�± 0.5 %. also tends to decrease with increasing EI NOx, consistent with earlier model simulations. The lowestHONO/NO,HONO/NOy and was observed for the largest passenger aircraft A380.

The effects of aircraft on climate and pollution. Part I: Numerical methods for treating the subgrid evolution of discrete size- and composition-resolved contrails from all commercial flights worldwide

This paper provides and evaluates mass conservative, positive-definite, unconditionally-stable, and non-iterative numerical techniques for simulating the evolution of discrete, size- and composition-resolved aerosol and contrail particles in individual aircraft exhaust plumes in a global or regional 3-D atmospheric model and coupling the subgrid exhaust plume information to the grid scale. Such treatment represents a new method of simulating the effects of aircraft on climate, contrails, and atmospheric composition. Microphysical processes solved within each plume include size-resolved coagulation among and between aerosol and contrail particles and their inclusions, aerosol-to-hydrometeor particle ice and liquid nucleation, deposition/sublimation, and condensation/evaporation. Each plume has its own emission and supersaturation, and the spreading and shearing of each plume’s cross-section are calculated as a function of time. Aerosol- and contrail-particle core compositions are tracked for each size and affect optical properties in each plume. When line contrails sublimate/evaporate, their size- and composition-resolved aerosol cores and water vapor are added to the grid scale where they affect large-scale clouds. Algorithm properties are analyzed, and the end-result model is evaluated against in situ and satellite data.

Parameterization of subgrid plume dilution for use in large-scale atmospheric simulations

Abstract. A new model of plume dynamics has been developed for use as a subgrid model of plume dilution in a large-scale atmospheric simulation. The model uses mean wind, shear, and diffusion parameters derived from the local large-scale variables to advance the plume cross-sectional shape and area in time. Comparisons with a large eddy simulation of aircraft emission plume dynamics, with an analytical solution to the dynamics of a sheared Gaussian plume, and with measurements of aircraft exhaust plume dilution at cruise altitude show good agreement with these previous studies. We argue that the model also provides a reasonable approximation of line-shaped contrail dilution and give an example of how it can be applied in a global climate model.