Jet noise has been a growing concern in recent years due to the costs associated with hearing loss of United States service members. Jet noise is also becoming more of a concern due to the rise of civilian complaints regarding the noise of jets near civilian and military air stations. One source of noise generation is from packets of air called eddies, which move with a convection velocity Uc. The current work seeks to expand upon the understanding of jet noise by collecting data using Time-resolved Doppler global velocimetry (TR-DGV) from regions of the jet known to produce high levels of acoustic radiation. Past experiments in studying convection velocity are reviewed based on the technique for obtaining the velocities. To add to these experiments, the current work analyzes data obtained using TR-DGV applied to a perfectly expanded Mach 1.65 flow with total temperature ratio (TTR) equal to 1. Additional measurements were obtained on a Mach 1.5 nozzle operated at a slightly over expanded condition and at TTR = 2. The cold jet flow is compared to the past experiments on unheated jets and demonstrates good agreement with respect to normalized convection velocities based on the jet exit speed. The data is then compared to past experiments conducted on the same nozzle at heated conditions. Shadowgraph imaging is used as a qualitative tool to locate shock cells within the jet plume. TR-DGV data from near the lipline (r = 0.5D) is axially aligned with the shadowgraph images to demonstrate that the shock structure within the potential core causes detectable variations in the scalar convective velocity. Additionally, it is shown that in the heated and unheated Mach 1.65 jet and the over expanded heated Mach 1.48 jet that the convection velocity does increase beyond the potential core. The Mach 1.48 jet is also compared to mean velocities obtained using Particle Image Velocimetry and found that the convective and mean velocities were only similar in some regions of the jet. A discussion is provided on suggestions of future work on where to obtain data within the jet plume and how to collect the data using current capabilities. Suggestions are also provided for improving data quality in future experiments, as well as ideas for future investigations into convection velocity along the length of the jet plume using TR-DGV. / Master of Science / Jet noise has been a growing concern in recent year due to the costs associated with hearing loss of United States service members. Additionally, many civilians complain about the noise of aircraft flying both out of military facilities and commercial airports. One source of noise generation is from packets of air called eddies which move with a convection velocity. Researchers have identified that by affecting the convection velocities of these eddies, there is a larger benefit than other traditional methods such as engine chevrons. The current work summarizes techniques used to investigate convective velocity as well as to provide evidence for other unconfirmed theories. This study focuses on using a laser-based technique to obtain data within the flow of an unheated supersonic jet. An unheated jet is studied to allow for easy comparison to other experiments that have used different diagnostic techniques. Additionally, this case is studied to complete a set of experiments that were previously conducted on the same nozzle so that there is a true base-line or “control” case for future work. Later in this paper, analysis will be done to show how shocks within the jet affect the convective velocity. A combination of both quantitative and qualitative efforts are performed to accomplish this. Additionally, it will be shown that after the potential core of the jet breaks down, there is an increase in the local convective velocity in this region immediately after the potential core. Finally, a brief summary will be given and suggestions for future work will be presented.

Neste trabalho foi realizado um estudo para verificar as melhores condições de vazão das atuais lanças supersônicas utilizadas no forno elétrico a arco 3 da Siderúrgica Riograndense. Também foi realizado um teste comparativo entre o modelo de lança supersônica atual e um novo modelo de injetor proposto. Para determinar as melhores condições de vazão das injetoras atuais, avaliou-se parâmetros como o consumo de oxigênio, energia elétrica, teor de FeO da escória, condições de desgaste do refratário e erosão dos bicos injetores. Para os testes comparativos com o novo modelo de injetores, foram usinados dois bicos de cobre com menor diâmetro de garganta. As novas pressões e vazões de oxigênio, tanto para o trabalho no modo alta vazão como para o modo purga, foram estabelecidas com base em estudos das características dos bicos utilizados atualmente. Os testes foram realizados em caráter comparativo no próprio forno 3. Nos atuais modelos de injetores utilizados, verificou-se que a pressão no modo purga deve variar entre 0,9 e 1,1 kgf/cm2 na rede de oxigênio. Assim, a vazão de O2 varia entre 65 e 75 Nm3/h, intervalo no qual foi observada a melhor eficiência na operação, considerando principalmente o controle do FeO da escória e a ocorrência de entupimento dos bicos supersônicos. Na alta vazão foram definidas pressões entre 9,0 e 9,5 kgf/cm2, onde as vazões variam entre 350 e 375 Nm3/h por bico. Estes valores foram definidos avaliando-se principalmente o controle do consumo de refratário na região do injetor e o desgaste dos bicos causado por jato subacelerado. Os injetores com diâmetro de garganta menor possibilitaram a operação com vazões de O2 menores na purga em relação ao modelo atual. Assim, foi possível operar com vazão em torno de 50 Nm3/h a uma pressão de 0,9 kgf/cm2, sem a ocorrência de entupimentos. Porém no modo alta vazão, para garantir a vazão mínima de 350 Nm3/h, a pressão no bico foi elevada para 12,5 kgf/cm2. Com este novo modelo de injetor, os consumos médios de oxigênio e de energia elétrica reduziram 0,8 Nm3/t e 12,9 kWh/t, respectivamente, em relação ao injetor atual, e verificou-se o aumento de 0,92% no rendimento metálico. / In this work, a study to verify the best conditions of oxygen flow to operate the supersonic injectors currently used in the Electric Arc Furnace 3 (EAF 3) of Siderúrgica Riograndense was carried out. Also, a comparative study between the supersonic injector model currently used and a new proposed model was made. To determine the best flow conditions of current injectors, parameters such as oxygen and electricity consumption, and slag FeO content were evaluated. Moreover, refractory wear conditions and copper lance tips erosion were analyzed. For the comparative tests with the new model, two copper lance tips have been machined, with a smaller throat diameter. The new oxygen pressure and oxygen flow (high and low flow operating modes) were established based on studies of features of the currently used lance tips. The tests were carried out comparatively in the same EAF 3. For the currently used injector models, it was verified that the pressure in the low flow mode must be kept between 0.9 and 1.1kgf/cm2 in the oxygen system. Thus, the O2 flow varies between 65 and 75 Nm3/h, interval in which the best efficiency in the operation was observed, considering mainly the control of FeO of the slag, and the occurrence of clogging of the supersonic lance tips. High flow pressures were defined between 9.0 and 9.5 kgf/cm2, where the flow varies between 350 and 375 Nm3/h per lance tip. These values were defined evaluating mainly the control of the refractory wear in the region of the injector, and the erosion of the lance tips caused by under-blown jet. The new lance tips with smaller throat diameter made it possible to operate with smaller O2 flow, 50 Nm3/h with pressure of 0.9 kgf/cm2, without clogging in low flow steps. However, in the high flow, to guarantee the minimum flow of 350 Nm3/h, the pressure in the lance tips was raised to 12.5 kgf/cm2. With this new model of injector, the average consumption of oxygen was lowered by 0.8 Nm3/h compared to the current injector and an increase of 0.92% was verified in the metallic yield. Furthermore, there was a reduction of 12.9 kWh/t in the consumption of electric energy.

Neste trabalho foi realizado um estudo para verificar as melhores condições de vazão das atuais lanças supersônicas utilizadas no forno elétrico a arco 3 da Siderúrgica Riograndense. Também foi realizado um teste comparativo entre o modelo de lança supersônica atual e um novo modelo de injetor proposto. Para determinar as melhores condições de vazão das injetoras atuais, avaliou-se parâmetros como o consumo de oxigênio, energia elétrica, teor de FeO da escória, condições de desgaste do refratário e erosão dos bicos injetores. Para os testes comparativos com o novo modelo de injetores, foram usinados dois bicos de cobre com menor diâmetro de garganta. As novas pressões e vazões de oxigênio, tanto para o trabalho no modo alta vazão como para o modo purga, foram estabelecidas com base em estudos das características dos bicos utilizados atualmente. Os testes foram realizados em caráter comparativo no próprio forno 3. Nos atuais modelos de injetores utilizados, verificou-se que a pressão no modo purga deve variar entre 0,9 e 1,1 kgf/cm2 na rede de oxigênio. Assim, a vazão de O2 varia entre 65 e 75 Nm3/h, intervalo no qual foi observada a melhor eficiência na operação, considerando principalmente o controle do FeO da escória e a ocorrência de entupimento dos bicos supersônicos. Na alta vazão foram definidas pressões entre 9,0 e 9,5 kgf/cm2, onde as vazões variam entre 350 e 375 Nm3/h por bico. Estes valores foram definidos avaliando-se principalmente o controle do consumo de refratário na região do injetor e o desgaste dos bicos causado por jato subacelerado. Os injetores com diâmetro de garganta menor possibilitaram a operação com vazões de O2 menores na purga em relação ao modelo atual. Assim, foi possível operar com vazão em torno de 50 Nm3/h a uma pressão de 0,9 kgf/cm2, sem a ocorrência de entupimentos. Porém no modo alta vazão, para garantir a vazão mínima de 350 Nm3/h, a pressão no bico foi elevada para 12,5 kgf/cm2. Com este novo modelo de injetor, os consumos médios de oxigênio e de energia elétrica reduziram 0,8 Nm3/t e 12,9 kWh/t, respectivamente, em relação ao injetor atual, e verificou-se o aumento de 0,92% no rendimento metálico. / In this work, a study to verify the best conditions of oxygen flow to operate the supersonic injectors currently used in the Electric Arc Furnace 3 (EAF 3) of Siderúrgica Riograndense was carried out. Also, a comparative study between the supersonic injector model currently used and a new proposed model was made. To determine the best flow conditions of current injectors, parameters such as oxygen and electricity consumption, and slag FeO content were evaluated. Moreover, refractory wear conditions and copper lance tips erosion were analyzed. For the comparative tests with the new model, two copper lance tips have been machined, with a smaller throat diameter. The new oxygen pressure and oxygen flow (high and low flow operating modes) were established based on studies of features of the currently used lance tips. The tests were carried out comparatively in the same EAF 3. For the currently used injector models, it was verified that the pressure in the low flow mode must be kept between 0.9 and 1.1kgf/cm2 in the oxygen system. Thus, the O2 flow varies between 65 and 75 Nm3/h, interval in which the best efficiency in the operation was observed, considering mainly the control of FeO of the slag, and the occurrence of clogging of the supersonic lance tips. High flow pressures were defined between 9.0 and 9.5 kgf/cm2, where the flow varies between 350 and 375 Nm3/h per lance tip. These values were defined evaluating mainly the control of the refractory wear in the region of the injector, and the erosion of the lance tips caused by under-blown jet. The new lance tips with smaller throat diameter made it possible to operate with smaller O2 flow, 50 Nm3/h with pressure of 0.9 kgf/cm2, without clogging in low flow steps. However, in the high flow, to guarantee the minimum flow of 350 Nm3/h, the pressure in the lance tips was raised to 12.5 kgf/cm2. With this new model of injector, the average consumption of oxygen was lowered by 0.8 Nm3/h compared to the current injector and an increase of 0.92% was verified in the metallic yield. Furthermore, there was a reduction of 12.9 kWh/t in the consumption of electric energy.

Neste trabalho foi realizado um estudo para verificar as melhores condições de vazão das atuais lanças supersônicas utilizadas no forno elétrico a arco 3 da Siderúrgica Riograndense. Também foi realizado um teste comparativo entre o modelo de lança supersônica atual e um novo modelo de injetor proposto. Para determinar as melhores condições de vazão das injetoras atuais, avaliou-se parâmetros como o consumo de oxigênio, energia elétrica, teor de FeO da escória, condições de desgaste do refratário e erosão dos bicos injetores. Para os testes comparativos com o novo modelo de injetores, foram usinados dois bicos de cobre com menor diâmetro de garganta. As novas pressões e vazões de oxigênio, tanto para o trabalho no modo alta vazão como para o modo purga, foram estabelecidas com base em estudos das características dos bicos utilizados atualmente. Os testes foram realizados em caráter comparativo no próprio forno 3. Nos atuais modelos de injetores utilizados, verificou-se que a pressão no modo purga deve variar entre 0,9 e 1,1 kgf/cm2 na rede de oxigênio. Assim, a vazão de O2 varia entre 65 e 75 Nm3/h, intervalo no qual foi observada a melhor eficiência na operação, considerando principalmente o controle do FeO da escória e a ocorrência de entupimento dos bicos supersônicos. Na alta vazão foram definidas pressões entre 9,0 e 9,5 kgf/cm2, onde as vazões variam entre 350 e 375 Nm3/h por bico. Estes valores foram definidos avaliando-se principalmente o controle do consumo de refratário na região do injetor e o desgaste dos bicos causado por jato subacelerado. Os injetores com diâmetro de garganta menor possibilitaram a operação com vazões de O2 menores na purga em relação ao modelo atual. Assim, foi possível operar com vazão em torno de 50 Nm3/h a uma pressão de 0,9 kgf/cm2, sem a ocorrência de entupimentos. Porém no modo alta vazão, para garantir a vazão mínima de 350 Nm3/h, a pressão no bico foi elevada para 12,5 kgf/cm2. Com este novo modelo de injetor, os consumos médios de oxigênio e de energia elétrica reduziram 0,8 Nm3/t e 12,9 kWh/t, respectivamente, em relação ao injetor atual, e verificou-se o aumento de 0,92% no rendimento metálico. / In this work, a study to verify the best conditions of oxygen flow to operate the supersonic injectors currently used in the Electric Arc Furnace 3 (EAF 3) of Siderúrgica Riograndense was carried out. Also, a comparative study between the supersonic injector model currently used and a new proposed model was made. To determine the best flow conditions of current injectors, parameters such as oxygen and electricity consumption, and slag FeO content were evaluated. Moreover, refractory wear conditions and copper lance tips erosion were analyzed. For the comparative tests with the new model, two copper lance tips have been machined, with a smaller throat diameter. The new oxygen pressure and oxygen flow (high and low flow operating modes) were established based on studies of features of the currently used lance tips. The tests were carried out comparatively in the same EAF 3. For the currently used injector models, it was verified that the pressure in the low flow mode must be kept between 0.9 and 1.1kgf/cm2 in the oxygen system. Thus, the O2 flow varies between 65 and 75 Nm3/h, interval in which the best efficiency in the operation was observed, considering mainly the control of FeO of the slag, and the occurrence of clogging of the supersonic lance tips. High flow pressures were defined between 9.0 and 9.5 kgf/cm2, where the flow varies between 350 and 375 Nm3/h per lance tip. These values were defined evaluating mainly the control of the refractory wear in the region of the injector, and the erosion of the lance tips caused by under-blown jet. The new lance tips with smaller throat diameter made it possible to operate with smaller O2 flow, 50 Nm3/h with pressure of 0.9 kgf/cm2, without clogging in low flow steps. However, in the high flow, to guarantee the minimum flow of 350 Nm3/h, the pressure in the lance tips was raised to 12.5 kgf/cm2. With this new model of injector, the average consumption of oxygen was lowered by 0.8 Nm3/h compared to the current injector and an increase of 0.92% was verified in the metallic yield. Furthermore, there was a reduction of 12.9 kWh/t in the consumption of electric energy.

No description available.

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Supersonic hot jet noise causes significant hearing impairment to the military workforce and results in substantial cost for medical care and treatment. Detailed insight into the turbulence structure of high-speed jets is central to understanding and controlling jet noise. For this purpose a new instrument based on the Doppler global velocimetry technique has been developed. This instrument is capable of measuring three-component velocity vectors over ex-tended periods of time at mean data-rates of 100 kHz. As a demonstration of the applicability of the time-resolved Doppler global velocimetry (TR-DGV) measurement technique, statistics of three-component velocity measurements, full Reynolds stress tensors and spectra along the stream-wise direction in a cold, supersonic jet at exit Mach number Mj = 1.4 (design Mach number Md = 1.65) are presented. In pursuance of extending the instrument to planar op- eration, a rapid response photomultiplier tube, 64-channel camera is developed. Integrating field programmable gate array-based data acquisition with two-stage amplifiers enables high-speed flow velocimetry at up to 10 MHz. Incor- porating this camera technology into the TR-DGV instrument, an investigation of the perfectly expanded supersonic jet at two total temperature ratios (TTR = 1.6 and TTR = 2.0) was conducted. Fourth-order correlations which have direct impact on the intensity of the acoustic far-field noise as well as convective velocities on the lip line at several stream-wise locations were obtained. Comprehensive maps of the convective velocity and the acoustic Mach number were determined. The spatial and frequency scaling of the eddy convective velocities within the developing shear layer were also investigated. It was found that differences in the radial diffusion of the mean velocity field and the integral eddy convective velocity creates regions of locally high convective Mach numbers after the potential core. This, according to acoustic analogies, leads to high noise radiation efficiency. The spectral scaling of the eddy convec- tive velocity indicates intermittent presence of large-scale turbulence structures, which, coupled with the emergence of Mach wave radiation, may be one of the main driving factors of noise emission observed in heated supersonic jets. / Ph. D.

Noise induced hearing loss is a large concern for the Department of Defense. Personnel on aircraft carriers are exposed to dangerous noise levels of noise from tactical aircraft, causing hearing damage which results in significant costs for medical care and treatment. Additionally, NASA and the FAA have begun to investigate the viability of reintroducing supersonic commercial transport in the United States and one of the largest problems to address is reducing the noise impact of these aircraft on communities. The overarching goal of jet noise research is to optimize noise reduction techniques for supersonic jets. In order to achieve this, a more complete theoretical framework which links the jet boundary conditions to the turbulence production in the jet plume and the far-field radiated noise must be established. The research presented herein was conducted on the hypothesis that introducing thermal non-uniformities into a heated supersonic jet flow can favorably alter the turbulence structure in the jet shear layer, leading to reductions in radiated noise. To investigate the impact of temperature on the turbulence development in the jet, spatially resolved three-component velocity vectors were acquired using particle image velocimetry (PIV) performed on two small-scale perfectly expanded Mach 1.5 jet flows, one with a uniform temperature profile and another containing a geometrically offset temperature non-uniformity. Using the PIV data, the mean velocities, Reynolds stresses, and correlation coefficients were obtained from both jet flows and compared to analyze changes in the mean turbulence field. Small but significant reductions in the shear layer turbulence were observed in the near nozzle region of the thermally offset jet when compared to the uniform jet case. The changes result in a thickening of the shear layer nearest the location of the cold plume which alters the integral length scales of the coherent turbulent structures in the offset jet in a manner consistent with other techniques presented in the literature that reduce jet noise. Applying quadrant analysis, a conditional averaging technique, to the jet turbulence plume revealed changes in the statistical flow field of Reynolds shear stress structures. The changes provide strong evidence of the presence of intermittent stream-wise vortical structures which serve to reduce the spatial correlation levels of turbulence in the thermally offset jet flow when compared to the uniform baseline jet. / Doctor of Philosophy / Increasingly large and powerful engines are required as the mission requirements for tactical aircraft become more advanced. These demands come at the cost of an increased production of noise which is particularly hazardous to crewpersons operating on Navy aircraft carriers during take-off and landing. Noise-induced hearing loss from extended exposure to high noise levels has become a major medical expenditure for the Navy. To address this issue in tactical aircraft engines, the sources of jet plume noise must be reduced, but doing so requires improved understanding of the connections between nozzle boundary conditions, the jet turbulence plume, and the radiated noise while keeping in consideration system constraints and performance requirements. The current study introduces a novel method for controlling supersonic jet noise induced by turbulence through the introduction of an offset non-uniform temperature perturbation at the nozzle mouth. Non-invasive flow measurements were conducted using stereoscopic particle image velocimetry to obtain high-resolution velocity and turbulence data. Analysis of the flow data indicate that an offset reduced temperature plume introduced at the nozzle exit has a first-order effect on the turbulence evolution which result in small, but significant reductions in jet noise levels. The reductions observed are attributed to a disruption in the coherence of the primary noise generating turbulence structures in the jet plume which are associated with the formation of stream-wise vortical structures induced by the cold plume.

Low density plasmas are found throughout the known universe. Therefore, accurate diagnostic methods have implications for our understanding of a variety of topics, ranging from star formation to the semi conductor industry. Low density plasmas are ubiquitous in the material processing industry. However, measurements of the electron temperature and density, two of the most fundamental plasma properties, are not straightforward. In the laboratory, we create a low density, radio frequency, helium plasma with a bi-Maxwellian electron distribution, similar to those found in the semiconductor processing industry. We use optical emission spectroscopy to perform a non invasive measurement of the plasma conditions. We compare this to measurements obtained using a Langmuir probe, a commonly used invasive diagnostic. The optical emission spectroscopy is found to be insensitive to electron density but good agreement is found between the two techniques for values of the temperature of the hot electron component of the bi-Maxwellian. Plasmas created with high-intensity lasers are able to recreate conditions similar to those found during astrophysical events. This development has led to these condi- tions being explored in laboratories around the world. An experiment was performed at the Rutherford Appleton Laboratory in Didcot, UK, investigating the properties of supersonic turbulent jets. For the first time a magneto-optic probe was used to measure the magnetic field in a low-density supersonic turbulent plasma. The results were compared to measurements taken using a magnetic-induction probe. Good agreement was found between measurements of the magnetic field strength within the plasma; however, the magnetic power spectra differ. We attribute this to the dif- ference in integration length between the two measurements. Statistical properties of the velocity field are inferred from the magnetic field measurements, which compare favourably to astrophysical observations and hydrodynamic simulations.

No description available.