High Accuracy Fuel Flowmeter, Phase 1

Technology related to aircraft fuel mass - flowmeters was reviewed to determine what flowmeter types could provide 0.25%-of-point accuracy over a 50 to one range in flowrates. Three types were selected and were further analyzed to determine what problem areas prevented them from meeting the high accuracy requirement, and what the further development needs were for each. A dual-turbine volumetric flowmeter with densi-viscometer and microprocessor compensation was selected for its relative simplicity and fast response time. An angular momentum type with a motor-driven, spring-restrained turbine and viscosity shroud was selected for its direct mass-flow output. This concept also employed a turbine for fast response and a microcomputer for accurate viscosity compensation. The third concept employed a vortex precession volumetric flowmeter and was selected for its unobtrusive design. Like the turbine flowmeter, it uses a densi-viscometer and microprocessor for density correction and accurate viscosity compensation

Experimental and analytical studies of a true airspeed sensor

A true airspeed sensor based on the precession of a vortex whistle for sensing airspeeds up to 321.9 km/hr (200 mph). In an attempt to model the complicated fluid mechanics of the vortex precession, three dimensional, inviscid, unsteady, incompressible fluid flow was studied by using the hydrodynamical linearized stability theory. The temporal stability approach was used to derive the relationship between the true airspeed and frequency response. The results show that the frequency response is linearly proportional to the airspeed. A computer program was developed to obtain the numerical solution. Computational results for various parameters were obtained. The designed sensor basically consisted of a vortex tube, a swirler, and a transducer system. A microphone converted the audible tone to an electronic frequency signal. Measurements for both the closed conduit tests and wind tunnel tests were recorded. For a specific flow rate or airspeed, larger exit swirler angles produced higher frequencies. For a smaller cross sectional area in the precessional flow region, the frequency was higher. It was observed that as the airspeed was increased the Strouhal number remained constant

Liquid Turbulence and Its Measurement

This paper covers several principles which have been successfully developed over the past few years and used in the measurement of liquid flows. In particular, ultrasonics, electro-magnetics, thermal heat transfer and optical light transmission will be discussed. Each concept will be covered by basic definitions and laws, theory of operation and application where measurement parameters will be highlighted, thus allowing the user to choose the best instrument to fit his experimental needs

Acoustic Streaming as a Mechanism of the Ranque-Hilsch Effect

The Ranque-Hilsch effect or the vortex tube effect is a striking phenomenon observed in swirling flows where air injected tangentially into a single pipe, separates spontaneously into two streams; the colder stream near the tube centerline and the hotter stream near its periphery. In spite of the simplicity of the Ranque-Hilsch tube, the mechanism of the total temperature separation, in the absence of any apparent external work, has not satisfactorily been resolved. Previously the mechanism has been purported to be due to the turbulent motion. However, if this were the mechanism, one could not explain why, in other turbulent swirling devices, the turbulence does not separate the total temperature in the same manner. Here experiments are conducted to substantiate a theory that acoustic streaming induced by the pure tone, a spinning wave present in swirling flows, deforms the base Rankine vortex into a forced vortex, resulting in total temperature separation in the radial direction. To verify this, acoustic suppressors of organ pipe type, tuned to the frequency of the vortex whistle, are installed on the Ranque-Hilsch tube. When the pitch of the vortex whistle, which increases as the flow through the tube is increased, hit the tuned frequency, the sound level suddenly tumbled, changing from a shrill whistle to a muffled hiss. At that very instant, the centerline temperature, which had gone down as low as -58° F immediately leapt upwards to +1° F corresponding to a sudden drop of temperature separation equal to 59° F; the temperature near the tube periphery plummeted by 10° F. This attests the theory that the vortex whistle is indeed the main cause of the Ranque-Hilsch effect

Development of test bench with airflow for resonator acoustic performance measurement

Acoustic properties of resonators installed in vehicle intake system are influenced by the high-speed airflow passing through, which causes errors between practical application and bench tests. In this paper, a test bench with airflow for measuring the resonator transmission loss is developed based on the principle of two-load method. Equipment types are selected and parameters calculation is presented. Effects of sound source protection devices on the performance of sound source are studied experimentally. A resistance resonator and several dissipative mufflers are mounted at the outlet of the vortex air pump to reduce airflow noise and verified to be effective. Finally, the transmission loss of a multi-chamber perforated resonator is measured with the developed test bench and effects of airflow on resonator acoustic properties are analyzed

Aircraft vortex marking program

A simple, reliable device for identifying atmospheric vortices, principally as generated by in-flight aircraft and with emphasis on the use of nonpolluting aerosols for marking by injection into such vortex (-ices) is presented. The refractive index and droplet size were determined from an analysis of aerosol optical and transport properties as the most significant parameters in effecting vortex optimum light scattering (for visual sighting) and visual persistency of at least 300 sec. The analysis also showed that a steam-ejected tetraethylene glycol aerosol with droplet size near 1 micron and refractive index of approximately 1.45 could be a promising candidate for vortex marking. A marking aerosol was successfully generated with the steam-tetraethylene glycol mixture from breadboard system hardware. A compact 25 lb/f thrust (nominal) H2O2 rocket chamber was the key component of the system which produced the required steam by catalytic decomposition of the supplied H2O2

Study and development of a holdingchamber for inhalation

Tese de Doutoramento em Engenharia MecânicaAsthma is a respiratory disease that causes chronic airway inflammation. Affecting more than 300 million individuals worldwide, it is a growing public health hazard. Inhalation therapy is the preferred strategy for medication delivery. This therapy is executed through specific delivery devices, whereas the pressurized Metered-Dose Inhaler (pMDI) is one of the most preferred. However, the pMDI efficiency is highly dependent on a correctly executed inhalation procedure. For children under 5 years old (or elderly individuals), it is advisable to use the pMDI coupled with an add-on device (i.e. spacer). Within the spacers, the Valved Holding Chamber (VHC) is the mostly used, due to its good capacity to reduce the pMDI spray coarse fraction and the oral-pharyngeal deposition ( 80%). Additionally, the VHC’s one-way valve allows the patient to maintain his tidal breathing during treatment. The VHC typically delivers a Fine Particle Mass (FPM) that is 20% of the labelled dose. Several design characteristics dictate the VHC performance, such as, the dimensions and the materials. The study herein focus on the assessment of eight commercial VHCs, through experimental and numerical methods. An experimental setup was developed, allowing the evaluation of the devices at constant flow rate (30 L/min and 60 L/min) and at variable flow (sine breath pattern). The waveform was obtained through a breathing simulator specially developed for this purpose, based in a cam-follower mechanism. The salbutamol sulphate (i.e. Ventolin) was collected using a cascade impactor (i.e. MSLI), and assessed by UV-Vis spectrophotometry analysis. Several metrics, regarding VHC performance, were calculated. Results have shown that the VHC capacity reduce the oral-pharyngeal deposition (64% - 94%), which is deeply related with the VHC valve design. It was observed that the VHC reduces the plume coarse fraction ( 70%), keeping the FPM bioequivalent to the pMDI solo. A correlation between the fine particle fraction and the volume of air passing through the VHC was proposed. Patient relevant metrics were suggested to classify the VHC devices upon quantitative and qualitative characteristics. A Computational Fluid Dynamics (CFD) model was developed where the air flow (i.e. 60 L/min)) was calculated along with the pMDI spray modelling as a discrete phase. The spray particle-wall interaction was modelled using different approaches and compared against literature and experimental data. This study, shed some light upon the spray evaporation process inside the VHC, showing that the efficiency of evaporation process is related with the VHC volume. A new VHC design, based in CFD dimensional optimisation of the VHC body is proposed, which shows an improvement of the FPM delivered.A asma é uma doença respiratória que causa a inflamação crónica das vias aéreas. Mundialmente, afeta mais de 300 milhões de indivíduos e é um problema crescente de saúde publica. A terapia de inalação é a estratégia preferida para administrar a medicação de controlo ou de alívio. Esta terapia é executada através de dispositivos específicos, entre os quais o Inalador Pressurizado com Válvula Doseadora (IPVD) é o mais usual. Contudo, a eficiência do IPVD é dependente de uma técnica de inalação correta. Para crianças com menos de 5 anos (ou idosos), é recomendável o uso do IPVD acoplado a um espaçador. Entre os espaçadores, a Câmara Expansora (CE) é a mais utilizada, devido à sua boa capacidade de redução das partículas grandes do aerossol do IPVD, e da redução da deposição orofaringeal ( 80%). Adicionalmente, a válvula de sentido único da CE, permite que o paciente mantenha a sua respiração normal durante o tratamento. A CE emite, tipicamente, uma massa de partículas finas (MPF) que é 20% da dose calibrada do IPVD. Este estudo foca-se na avaliação de oito CEs, através de uma metodologia experimental e numérica. Uma instalação experimental foi projetada para a avaliação dos dispositivos a fluxo constante (30 L/min e 60 L/min) e variável (um padrão respiratório sinusoidal). A onda foi obtida através de um simulador respiratório especialmente desenvolvido para este propósito, o qual foi baseado num mecanismo cam-seguidor. O sulfato de salbutamol (Ventilan HFA) foi recolhido utilizando um impactor em cascata em vários estágios (Aparelho C da Farmacopeia Portuguesa), e quantificado por espetrofotometria UV-Visivel. Foram calculadas várias métricas sobre o desempenho das CEs. Os resultados demonstram a capacidade da CE para reduzir a deposição orofaringeal (64% - 94%), a qual está intrinsecamente relacionada com o design da válvula do dispositivo. Foi observado que a CE reduz a fração de partículas grandes na pluma ( 70%), mantendo a MPF bioequivalente à emitida pelo IPVD. Foi proposta uma correlação entre a fração de partículas finas e o volume de ar que atravessa a CE. Foram também sugeridas métricas com relevância para o paciente, que classificam as CEs de forma quantitativa e qualitativa. Foi desenvolvido um modelo de Dinâmica Computacional de Fluidos (DCF), onde o fluxo de ar (a 60 L/min) foi calculado juntamente com o aerossol do IPVD, tendo sido este modelado como uma fase discreta. A interação entre partícula e parede foi modelada utilizando diferentes aproximações matemáticas, sendo posteriormente comparadas com a literatura e dados experimentais. Este estudo contribui com um melhor conhecimento do processo de evaporação das gotas do aerossol dentro da CE, onde se verificou que este processo está relacionado com o volume da CE. Foi proposto em novo design para CE, baseado numa otimização das dimensões do corpo da CE, que demonstra melhoria da MPF emitida

LOW COST FLOW SENSING FOR FIELD SPRAYERS

Precisely measuring the flow rate in sprayers is a key technology to precision agriculture. With the development of advanced technologies, the demand for the ability to measure flow rate of individual nozzle has become more important and urgent. This paper investigates the possibility of developing a low-cost flow rate measurement technique. The technique is based on analyzing the acoustic signal from a microphone placed near the nozzle tip. A comparison between acoustic signal and vibration signal was made to study the relations between them. Then several possible locations of the microphone for measuring flow rate were tested and compared, and one has been chosen as the best location. After that, two methods of analyzing data were proposed, one that could better describe the original curve was chosen. With all of that work done, further experiments were conducted on a variety of nozzle tips. The results showed that an acoustic sensor could be used as an indicator of flow rate from a nozzle, but that unique calibrations for different nozzle tips would be necessary

Design of experimental apparatus for generation and measurement of an aerosol

Dr. Jacob A. McFarland, Thesis Supervisor.This work is done as a requirement for the master's degree. In this work, a system for generating aerosol delivery into shock tube for interface creation and a method to measure aerosol is developed. In chapter 1, a brief introduction of hydrodynamic instabilities later focussing on shock driven multiphase instabilities (SDMI) and its importance is presented. SDMIs have similar flow morphology to the Richtmeyer-Meshkov Instability (RMI), however, the driving force that induces instability is different. Current methods of aerosol production and measurement with pros and cons are given to justify the adaption of the selected method for our system. Chapter 2 discusses about the theory of ultrasonic atomization and evidence of faraday instability for atomization. Later setup of aerosol delivery system with two different set of atomizers is presented. In chapter 3, Laser interferometry principle and apparatus used for the measurement of aerosol with the consideration of various factors is given. To avoid Mie scattering theory's intense use of calculations Geometrical optics approximation method is used which agrees well with the Mie theory for all the particles above 1µm. Chapter 4 presents experimental results of measurement which includes particle size distribution, density measurement of aerosol. Later it presents the experimental results when the aerosol is used for the study of SDMI. Two different cases, one with the low effective Atwood number and the other with higher effective Atwood number are investigated. In the case of low effective Atwood number the instability evolved is more like RMI rather than SDMI which is due to domination of Gas Atwood number over effect Atwood number. Last case with higher effective Atwood number of 0.03 with shock wave of Mach 1.66 is investigated, to find out that flow morphologies are in good agreement with literature and simulations. Chapter 5 gives conclusion of the research studies and future research.Dr. Jacob A. McFarland, Thesis Supervisor.Includes bibliographical references (pages 49-55)