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Michael M James - One of the best experts on this subject based on the ideXlab platform.
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propagation of crackle containing Jet noise from high performance engines
Noise Control Engineering Journal, 2016Co-Authors: Tracianne B Neilsen, Michael M James, Alan T. Wall, Micah J Downing, Richard L MckinleyAbstract:Crackle, the impulsive quality sometimes present in supersonic Jet noise, has traditionally been defined in terms of the pressure waveform skewness. However, recent work has shown that the pressure waveform time derivative is a better quantifier of the acoustic shocks believed to be responsible for crackle perception. This paper discusses two definitions of crackle: waveform asymmetry versus shock content and crackle as a source or propagation-related phenomenon. Data from two static military Jet Aircraft tests are used to demonstrate that the skewed waveforms radiated from the Jet undergo significant nonlinear steepening and shock formation, as evidenced by the skewness of the time derivative of the pressure waveforms. To the extent that crackle is caused by the presence of shock-like features in the waveform, crackle's perceived quality is likely to be heavily influenced by propagation through the geometric near field and into the far field.
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acoustic intensity near a high powered military Jet Aircraft
Journal of the Acoustical Society of America, 2015Co-Authors: Trevor A Stout, Tracianne B Neilsen, Alan T. Wall, Michael M JamesAbstract:The spatial variation in vector acoustic intensity has been calculated between 100 and 3000 Hz near a high-performance military Aircraft. With one engine of a tethered F-22A Raptor operating at military power, a tetrahedral intensity probe was moved to 27 locations in the geometric near and mid-fields to obtain the frequency-dependent intensity vector field. The angles of the maximum intensity region rotate from aft to sideline with increasing frequency, becoming less directional above 800 Hz. Between 100 and 400 Hz, which are principal radiation frequencies, the ray-traced dominant source region rapidly contracts and moves upstream, approaching nearly constant behavior by 1000 Hz.
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intensity analysis of peak frequency region in noise produced by a military Jet Aircraft
Journal of the Acoustical Society of America, 2013Co-Authors: Trevor A Stout, Tracianne B Neilsen, Alan T. Wall, Michael M JamesAbstract:Acoustic intensity measurements of the F-22A Raptor are analyzed as part of ongoing efforts to characterize the noise radiation from military Jet Aircraft. Data were recorded from a rig of microphones and an attached tetrahedral intensity probe at various locations to the sideline and aft of the Aircraft. Recently, techniques such as coherence, similarity spectra analyses, and near-field acoustical holography have indicated a peak-frequency region comprised of two maxima that have very different radiation directionalities. Acoustic vector intensity is analyzed as a function of frequency to further assess the behavior of this double-peak phenomenon, which is not accounted for by current Jet noise models. The results thus far confirm the discrete nature of the peaks and their directionalities.
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on the evolution of crackle in Jet noise from high performance engines
AIAA CEAS Aeroacoustics Conference, 2013Co-Authors: Kent L. Gee, Tracianne B Neilsen, Michael M James, Alan T. Wall, Micah J Downing, Michael B Muhlestein, Blue Ridge, Richard L MckinleyAbstract:Crackle, the impulsive quality sometimes present in supersonic Jet noise, has traditionally been defined in terms of the pressure waveform skewness. However, recent work has shown that the pressure waveform time derivative is a better quantifier of the acoustic shocks believed to be responsible for its perception. This paper discusses two definitions of crackle, waveform asymmetry versus shock content, and crackle as a source or propagation-related phenomenon. Data from two static military Jet Aircraft tests are used to demonstrate that the skewed waveforms radiated from the Jet undergo significant nonlinear steepening and shock formation, as evidenced by the skewness of the time derivative. Thus, although skewness is a source phenomenon, crackle’s perceived quality is heavily influenced by propagation through the near field and into the far field to the extent that crackle is caused by the presence of shock-like features in the waveform.
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spectral characterization in the near and mid field of military Jet Aircraft noise
AIAA CEAS Aeroacoustics Conference, 2013Co-Authors: Tracianne B Neilsen, Michael M JamesAbstract:Spatial dependence of levels and spectral characteristics of the near-field noise spectra from the afterburning F-22A Raptor and their transition toward far-field behavior are described. It is shown that the measured spectra in the vicinity of the Aircraft show relatively good agreement with overall shape of large and fine-scale similarity spectra, with two exceptions. First, the measured spectral shapes have shallower slopes at high frequencies than the similarity spectra at most downstream locations. The variation in high-frequency slope with downstream distance is quantified and, in the vicinity of the maximum radiation direction, approaches the !/! ! limit associated with shock formation. This measured slope agrees with some previous laboratory and full-scale measurements of supersonic Jet noise. Second, the spectra at downstream distances corresponding to the region of maximum radiation exhibit a double peak, a characteristic not predicted by the similarity spectra nor seen in laboratory-scale measurements. In addition, the maximum in the peak-frequency region does not vary continuously with downstream distance, but rather exhibits discrete frequency jumps, with relative contributions of the different peaks varying as a function of downstream distance. These observations have implications in finding ties between the noise from high performance, full-scale engines and laboratory-scale experiments and computational modeling efforts. Furthermore, they indicate the limitations in applying the present similarity spectra models to full-scale engine noise.
U. Schumann - One of the best experts on this subject based on the ideXlab platform.
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in situ observations of particles in Jet Aircraft exhausts and contrails for different sulfur containing fuels
Journal of Geophysical Research, 1996Co-Authors: U. Schumann, R Busen, Johan Strom, Robert Baumann, Klaus Gierens, M Krautstrunk, F Schroder, J StinglAbstract:The impact of sulfur oxides on particle formation and contrails is investigated in the exhaust plumes of a twin-engine Jet Aircraft. Different fuels were used with sulfur mass fractions of 170 and 5500 ppm in the fuel, one lower than average, the other above the specification limit of standard Jet-Al fuel. During various phases of the same flight, the two engines burnt either high- or low-sulfur fuel or different fuels in the two engines. Besides visual, photographic, and video observations from close distance, in situ measurements were made within the plumes at plume ages of 20 to 30 s, at altitudes between 9 and 9.5 km, and temperatures between −49 and −55°C, when the visible contrail was about 2 km long. The data include particle number densities for particles larger than 7 nm, 18 nm, 120 nm, and 1 μm in diameter, together with wind, temperature and humidity measurements. The observations show visible and measurable differences between contrails caused by the different sulfur levels. At ambient temperatures 5 K below the threshold temperature for contrail onset, the plume became visible about 10 m after the engine exit for high sulfur content, but 15 m after the engine exit for low sulfur content. The higher sulfur emission caused a larger optical thickness of the contrail shortly after onset, with slightly brown-colored contrail when the Sun was behind the observer, and more contrast when viewed against the Sun. The high-sulfur contrail grew more quickly but also evaporated earlier than the low-sulfur contrail. At plume ages of about 20 s, each engine plume was diluted to an effective diameter of 20 m. The plumes contained many sub visible particles. Peak number densities were 30,000 cm−3 for particles of diameter above 7 nm and 15,000 cm−3 above 18 nm. The latter is a little larger than the estimated number of soot particles emitted. The high-sulfur plume shows more particles than the low-sulfur plume. The differences are about 25% for particles above 7 nm and about 50% above 18 nm. The results indicate that part of the fuel sulfur is converted to sulfuric acid which nucleates with water vapor heterogeneously on soot or nucleates acid droplets homogeneously which then coagulate partly with soot. During descent through the level of contrail onset, the high-sulfur contrail remained visible at slightly lower altitude (25 to 50 m) or higher temperature (0.2 to 0.4 K). At least for average to high sulfur contents, Aircraft generate an invisible aerosol trail which enhances the background level of condensation nuclei, in particular in regions with dense air traffic at northern latitudes and near the tropopause.
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particle formation in Jet Aircraft exhausts and contrails for different sulfur containing fuels
Nucleation and Atmospheric Aerosols, 1996Co-Authors: U. SchumannAbstract:Publisher Summary This chapter discusses the process that leads to a visible contrail within 0.2 s plume age for the first experimental case with rather low sulfur contents. A series of experiments has been performed observing contrail formation of twin-engine Jet Aircraft (ATTAS-VFW 614 and Airbus A310-300) running with different sulfur containing fuels on the two engines at the same time. The fuel sulfur mass content was varied from 2–5500 ppm. The results suggest that contrail particles form mainly from soot particles. The higher the sulfur content the more of the soot particles are activated as condensation nuclei. Particles start condensing in the liquid phase but have to freeze quickly, and the water vapor mass accommodation coefficient must be larger than about 0.2, both for liquid and ice particles to form a visible contrail within 25 m after the Aircraft as observed.
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visible contrail formation from fuels with different sulfur contents
Geophysical Research Letters, 1995Co-Authors: R Busen, U. SchumannAbstract:As a test for postulated influences of sulfur emissions on nucleation, the contrail formation from a two-engine Jet Aircraft was investigated using fuels with different sulfur contents for the two engines during the same flight. The sulfur mass fractions in the fuels were about 2 and 250 ppm, respectively, typical for aviation fuels. Other engine and fuel parameters were about the same for both engines. Contrail formation was observed visually from distances as close as 100 m and documented by video and photos. The flight took place at 302 hPa (9 km altitude), at ambient temperatures of about −50°C, and relative humidity for liquid water of about 34 %. Short contrails formed about 30 m after the engines. No visible differences were detected in the contrails forming from the two engines. The observed conditions for contrail formation are close to those predicted by Appleman [1953] if the propulsion efficiency of the Aircraft/engine combination during flight is taken into account.
H Schlager - One of the best experts on this subject based on the ideXlab platform.
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no x emission indices of subsonic long range Jet Aircraft at cruise altitude in situ measurements and predictions
Journal of Geophysical Research, 1997Co-Authors: P Schulte, H Schlager, H Ziereis, Ulrich Schumann, S L Baughcum, F DeidewigAbstract:In the course of the Commissions of the European Communities project “Pollution From Aircraft Emissions in the North Atlantic Flight Corridor (POLINAT)”, in situ measurements of NO, NOx , and CO2 volume mixing ratios in the near-field exhaust plumes of seven subsonic long-range Jet Aircraft have been carried out by using the research Aircraft Falcon of the Deutsche Forschungsanstalt fur Luft- und Raumfahrt (DLR). For three additional Aircraft, only NO and CO2 were measured. Plume ages of 50 s to 150 s have been covered, with maximum observed exhaust gas enhancements of 319 parts per billion by volume and 51 parts per million by volume for Δ[NOx] and Δ[CO2], respectively, in relation to ambient values. Aircraft cruising altitudes and Mach numbers ranged from 9.1 to 11.3 km and from 0.77 to 0.85, respectively. These measurements are used to derive NOx emission indices for seven of the individual Aircraft/engine combinations. The NOx emission indices derived range from 12.3 g/kg to 30.4 g/kg. They are compared with predicted emission index values, calculated for the same Aircraft engine and the actual conditions by using two newly developed fuel flow correlation methods. The calculated emission indices were mostly within or close to the error limits of the measured values. On average, the predictions from both methods were 12% lower than the measured values, with an observed maximum deviation of 25%. The ratio γ = [NO2]/[NOx] found during the present measurements ranged from 0.06 to 0.11 for five daytime cases and was around 0.22 for two nighttime cases. By use of a simple box model of the plume chemistry and dilution these data were used to estimate the initial value γ0 present at the engine exit plane. We found γ0 values between 0 and 0.15. These were applied to estimate the corresponding NO2 for the three cases in which only NO was measured.
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in flight measurements of cruise altitude nitric oxide emission indices of commercial Jet Aircraft
Geophysical Research Letters, 1996Co-Authors: P Schulte, H SchlagerAbstract:Simultaneous in-situ NO and CO2 measurements on board the DLR Falcon research Aircraft in the exhaust plumes of commercial short to medium range Jet Aircraft are used to determine lower limits for the NOx emission indices EI(NOx) for cruising conditions. Concentration enhancements for NO and CO2 of 9 to 33 ppbv and 4 to 14 ppmv, respectively, relative to ambient background concentrations were observed in the exhaust trails 40 s to 130 s after emission. The derived EI(NOx)-limits range between 6.4 to 11.7 g/kg. Though the NO2 fraction in the exhaust plumes has not been measured during these pilot investigations, arguments are given that the derived lower limits represent a close approximation to the EI(NOx) values. Within the present uncertainties they are in agreement with predictions based on ground-based engine test data.
Yasin Korkmaz - One of the best experts on this subject based on the ideXlab platform.
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Computation of the pressure altitude using adaptive neuro fuzzy inference system for Air Data Computer in Aircrafts
2011 IEEE 19th Signal Processing and Communications Applications Conference (SIU), 2011Co-Authors: Ilke Turkmen, Yasin KorkmazAbstract:For a safe flight and accurate air navigation, the key data are calculated using Air Data Computer (ADC). Altitude information is one of the important parameter computed by the ADC. According to Aircraft type, accuracy of the altitude corrected using tables or charts showing the actual corrections in altitude information special to the Aircraft. This correction is important in any high performance and Jet Aircraft. In this paper, adaptive neuro fuzzy system (ANFIS) are used to calculate altitude information more easily and accurately using data obtained from tables formed under standard atmosphere conditions. The pressure altitude values obtained using proposed ANFIS model don't need to correction.
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Uçaklardaki Hava Veri Bilgisayarinda Basinç İrtifasinin Bulanik Mantik Sistemine Dayali Uyarlanir Ağ İle Hesaplanmasi Computation of the Pressure Altitude Using Adaptive Neuro Fuzzy Inference System for Air Data Computer in Aircrafts
2011Co-Authors: Yasin KorkmazAbstract:For a safe flight and accurate air navigation, the key data are calculated using Air Data Computer (ADC). Altitude information is one of the important parameter computed by the ADC. According to Aircraft type, accuracy of the altitude corrected using tables or charts showing the actual corrections in altitude information special to the Aircraft. This correction is important in any high performance and Jet Aircraft. In this paper, adaptive neuro fuzzy system (ANFIS) are used to calculate altitude information more easily and accurately using data obtained from tables formed under standard atmosphere conditions. The pressure altitude values obtained using proposed ANFIS model don’t need to correction. 1. GIRIŞ
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the pressure altitude computation using artificial neural network for air data computer
International Symposium on Signal Processing and Information Technology, 2010Co-Authors: Ilke Turkmen, Yasin KorkmazAbstract:Air Data Computer (ADC) calculates the key data necessary for performing a safe flight and accurate air navigation. Altitude information is one of the important parameter computed by the ADC. Accuracy of the altitude corrected using tables or charts showing the actual corrections in altitude information special to Aircraft type. This correction is important in any high performance and Jet Aircraft. In order to correct these imperfections, certain calibrations need to be made within the ADC. In this paper, artificial neural networks (ANNs) are used to calculate altitude information more easily and accurately using data obtained from tables formed under standard atmosphere conditions.
Tracianne B Neilsen - One of the best experts on this subject based on the ideXlab platform.
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propagation of crackle containing Jet noise from high performance engines
Noise Control Engineering Journal, 2016Co-Authors: Tracianne B Neilsen, Michael M James, Alan T. Wall, Micah J Downing, Richard L MckinleyAbstract:Crackle, the impulsive quality sometimes present in supersonic Jet noise, has traditionally been defined in terms of the pressure waveform skewness. However, recent work has shown that the pressure waveform time derivative is a better quantifier of the acoustic shocks believed to be responsible for crackle perception. This paper discusses two definitions of crackle: waveform asymmetry versus shock content and crackle as a source or propagation-related phenomenon. Data from two static military Jet Aircraft tests are used to demonstrate that the skewed waveforms radiated from the Jet undergo significant nonlinear steepening and shock formation, as evidenced by the skewness of the time derivative of the pressure waveforms. To the extent that crackle is caused by the presence of shock-like features in the waveform, crackle's perceived quality is likely to be heavily influenced by propagation through the geometric near field and into the far field.
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acoustic intensity near a high powered military Jet Aircraft
Journal of the Acoustical Society of America, 2015Co-Authors: Trevor A Stout, Tracianne B Neilsen, Alan T. Wall, Michael M JamesAbstract:The spatial variation in vector acoustic intensity has been calculated between 100 and 3000 Hz near a high-performance military Aircraft. With one engine of a tethered F-22A Raptor operating at military power, a tetrahedral intensity probe was moved to 27 locations in the geometric near and mid-fields to obtain the frequency-dependent intensity vector field. The angles of the maximum intensity region rotate from aft to sideline with increasing frequency, becoming less directional above 800 Hz. Between 100 and 400 Hz, which are principal radiation frequencies, the ray-traced dominant source region rapidly contracts and moves upstream, approaching nearly constant behavior by 1000 Hz.
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intensity analysis of peak frequency region in noise produced by a military Jet Aircraft
Journal of the Acoustical Society of America, 2013Co-Authors: Trevor A Stout, Tracianne B Neilsen, Alan T. Wall, Michael M JamesAbstract:Acoustic intensity measurements of the F-22A Raptor are analyzed as part of ongoing efforts to characterize the noise radiation from military Jet Aircraft. Data were recorded from a rig of microphones and an attached tetrahedral intensity probe at various locations to the sideline and aft of the Aircraft. Recently, techniques such as coherence, similarity spectra analyses, and near-field acoustical holography have indicated a peak-frequency region comprised of two maxima that have very different radiation directionalities. Acoustic vector intensity is analyzed as a function of frequency to further assess the behavior of this double-peak phenomenon, which is not accounted for by current Jet noise models. The results thus far confirm the discrete nature of the peaks and their directionalities.
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on the evolution of crackle in Jet noise from high performance engines
AIAA CEAS Aeroacoustics Conference, 2013Co-Authors: Kent L. Gee, Tracianne B Neilsen, Michael M James, Alan T. Wall, Micah J Downing, Michael B Muhlestein, Blue Ridge, Richard L MckinleyAbstract:Crackle, the impulsive quality sometimes present in supersonic Jet noise, has traditionally been defined in terms of the pressure waveform skewness. However, recent work has shown that the pressure waveform time derivative is a better quantifier of the acoustic shocks believed to be responsible for its perception. This paper discusses two definitions of crackle, waveform asymmetry versus shock content, and crackle as a source or propagation-related phenomenon. Data from two static military Jet Aircraft tests are used to demonstrate that the skewed waveforms radiated from the Jet undergo significant nonlinear steepening and shock formation, as evidenced by the skewness of the time derivative. Thus, although skewness is a source phenomenon, crackle’s perceived quality is heavily influenced by propagation through the near field and into the far field to the extent that crackle is caused by the presence of shock-like features in the waveform.
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spectral characterization in the near and mid field of military Jet Aircraft noise
AIAA CEAS Aeroacoustics Conference, 2013Co-Authors: Tracianne B Neilsen, Michael M JamesAbstract:Spatial dependence of levels and spectral characteristics of the near-field noise spectra from the afterburning F-22A Raptor and their transition toward far-field behavior are described. It is shown that the measured spectra in the vicinity of the Aircraft show relatively good agreement with overall shape of large and fine-scale similarity spectra, with two exceptions. First, the measured spectral shapes have shallower slopes at high frequencies than the similarity spectra at most downstream locations. The variation in high-frequency slope with downstream distance is quantified and, in the vicinity of the maximum radiation direction, approaches the !/! ! limit associated with shock formation. This measured slope agrees with some previous laboratory and full-scale measurements of supersonic Jet noise. Second, the spectra at downstream distances corresponding to the region of maximum radiation exhibit a double peak, a characteristic not predicted by the similarity spectra nor seen in laboratory-scale measurements. In addition, the maximum in the peak-frequency region does not vary continuously with downstream distance, but rather exhibits discrete frequency jumps, with relative contributions of the different peaks varying as a function of downstream distance. These observations have implications in finding ties between the noise from high performance, full-scale engines and laboratory-scale experiments and computational modeling efforts. Furthermore, they indicate the limitations in applying the present similarity spectra models to full-scale engine noise.