Showing papers on "Chamber pressure published in 2005"

Thrust Chamber Dynamics and Propulsive Performance of Single -Tube Pulse Detonation Engines

Abstract: This pape r deals with the modeling and simulation of the thrust chamber dynamics in an airbreathing pulse detonation engine (PDE). The system under consideration includes a supersonic inlet, an air manifold, a rotary valve, a single -tube combustor , and a convergent -divergent nozzle. The analysis accommodates the full conservation equations in two - dimensional coordinates, along with a calibrated one - progress -variable chemical reaction scheme for a stoichiometric hydrogen/air mixture. The combustion and flow dynamics involved in typical PDE operations are carefully examined. In addition, a flow -path based performance prediction model is established to estimate the theoretical limit of the engine propulsive performance. Various performance loss mechanisms, including refilling process, mismatch of nozzle exit flow conditions with the ambient state, nozzle flow divergence, and internal flow dynamics, are identified and quantified. The internal flow loss, which mainly arises from the shock waves within the chamber, play s a dominant role in degrading the PDE performance. The effects of engine operating parameters and nozzle configurations on the system dynamics are also studied in depth. Results indicate the existence of an optimum operating frequency for achieving a be st performance margin. For a given cycle period and purge time, the performance increases with decreasing valve close -up time in most cases. On the other hand, a larger purge time decreases the specific thrust but increases the specific impulse for a giv en cycle period and valve close -up time. The nozzle throat area affects both the flow expansion process and chamber dynamics, thereby exerting a much more significant influence than the other nozzle geometrical parameters.

Benchmark Wall Heat Flux Data for a GO2/GH2 Single Element Combustor

Abstract: Wall heat flux measurements in a 1.5 in. diameter circular cross-section rocket chamber for a uni-element shear coaxial injector element operating on gaseous oxygen (GOz)/gaseous hydrogen (GH,) propellants are presented. The wall heat flux measurements were made using arrays of Gardon type heat flux gauges and coaxial thermocouple instrumentation. Wall heat flux measurements were made for two cases. For the first case, GOZ/GHz oxidizer-rich (O/F=l65) and fuel-rich preburners (O/F=1.09) integrated with the main chamber were utilized to provide vitiated hot fuel and oxidizer to the study shear coaxial injector element. For the second case, the preburners were removed and ambient temperature gaseous oxygen/gaseous hydrogen propellants were supplied to the study injector. Experiments were conducted at four chamber pressures of 750, 600, 450 and 300psia for each case. The overall mixture ratio for the preburner case was 6.6, whereas for the ambient propellant case, the mixture ratio was 6.0. Total propellant flow was nominally 0.27-0.29 Ibm/s for the 750 psia case with flowrates scaled down linearly for lower chamber pressures. The axial heat flux profile results for both the preburner and ambient propellant cases show peak heat flux levels a t axial locations between 2.0 and 3.0 in. from the injector face. The maximum heat flux level was about two times greater for the preburner case. This is attributed to the higher injector fuel-to-oxidizer momentum flux ratio that promotes mixing and higher initial propellant temperature for the preburner case which results in a shorter reaction zone. The axial heat flux profiles were also scaled with respect to the chamber pressure to the power 0.8. The results at the four chamber pressures for both cases collapsed to a single profile indicating that at least to first approximation, the basic fluid dynamic structures in the flow field are pressure independent as long as the chamber/njector/nozzle geometry and injection velocities remain the same.

Controlled growth of gold nanoparticles on silica nanowires

Abstract: Production of gold nanoparticles with the specific goal of particle size control has been investigated by systematic variation of chamber pressure and substrate temperature. Gold nanoparticles have been synthesized on SiO2 nanowires by plasma-enhanced chemical vapor deposition. Determination of particle size and particle size distribution was done using transmission electron microscopy. Average nanoparticle diameters were between 4 and 12 nm, with particle size increasing as substrate temperature increased from 573 to 873 K. A bimodal size distribution was observed at temperatures ≥723 K indicating Ostwald ripening dominated by surface diffusion. The activation energy for surface diffusion of gold on SiO2 was determined to be 10.4 kJ/mol. Particle sizes were found to go through a maximum with increases in chamber pressure. Competition between diffusion within the vapor and dissociation of the precursor caused the pressure effect.

Apparatus and method for applying coatings onto the interior surfaces of components and related structures produced therefrom

Abstract: Provided is a methodology and system (1) for applying coatings onto the interior surfaces of components (40). The approach comprises a vapor creation device (3) (for example an electron beam or laser that evaporates a single or multiplicity of solid or liquid sources), a vacuum chamber (4) having a moderate gas pressure (between about 10-4 to about 103 Torr) and a inert gas jet (5) having controlled velocity and flow fields of gas jet. The gas jet is created by a rarefied, inert gas supersonic expansion through a nozzle (30). By controlling the carrier gas flow into a region upstream of the nozzle an upstream pressure is achieved (i.e. the gas pressure prior to its entrance into the processing chamber through the nozzle). The carrier gas flow and chamber pumping rate control the downstream (or chamber) pressure (i.e., downstream of the nozzle). The ratio of the upstream to downstream pressure along with the size and shape of the nozzle opening controls the speed of the gas entering the chamber. The carrier gas molecular weight (compared to that of the vapor) and the carrier gas speed controls its effectiveness in redirecting the vapor atoms via binary collisions towards the substrate (40). The speed and flux of the atoms entering the chamber, the nozzle parameters, and the operating chamber pressure can all vary leading to a wide range of accessible processing conditions. Vapor (15) created from a source (25) is transported into the interior regions of a component using binary collisions between the vapor and gas jet atoms (17). Under certain process conditions these collisions enable the vapor atoms to scatter onto the interior surfaces of the component and deposit.

Pulsed mass flow delivery system and method

Abstract: A system for delivering a desired mass of gas, including a chamber, a first valve controlling flow into the chamber, a second valve controlling flow out of the chamber, a pressure transducer connected to the chamber, an input device for providing a desired mass to be delivered, and a controller connected to the valves, the pressure transducer and the input device The controller is programmed to receive the desired mass from the input device, close the second valve and open the first valve, receive chamber pressure measurements from the pressure transducer, and close the inlet valve when pressure within the chamber reaches a predetermined level The controller is then programmed to wait a predetermined waiting period to allow the gas inside the chamber to approach a state of equilibrium, then open the outlet valve at time = t0, and close the outlet valve at time = t* when the mass of gas discharged equals the desired mass

Lead embedded pressure sensor

Abstract: A pressure capsule embedded in a pacemaker lead to monitor intracardiac chamber pressure is described. This pressure monitor capsule provides highly accurate pressure readings while insuring a high integrity seal against bodily fluids and tissue growth. The capsule is intended to be embedded into a pacemaker cardiac lead or a catheter with the distal (Tip) isolation diaphragm sensing pressure, coupling the pressure through an air column to a protected sensing MEMS device and providing a secure fluid seal to the lead walls. The proximal (Back) end of the capsule provides the electrical interface through the lead to the pacemaker pulse generator.

Control of sidewall slope in silicon vias using SF6∕O2 plasma etching in a conventional reactive ion etching tool

Abstract: The etching of anisotropic blind vias in silicon with diameters of 5–10μm and an aspect ratio ∼2–4 with controlled sidewall inclination is reported. The motivation for this work is the creation of a vertical, or three dimensional interconnect. Via formation by reactive ion etch (RIE) processing is the focus of this project. Arrays of vias have been etched in 125 mm diam silicon (100) wafers using a photoresist mask. A parallel plate RIE system with a SF6∕O2 gas mixture is used. The effects of O2∕(SF6+O2) gas flow ratio, electrode bias, and chamber pressure on etch rate and feature profile have been studied. Visualization of the via profiles using scanning electron microscopy is used to identify the key parameters that control the sidewall slope. This slope is important for the subsequent deposition of via lining materials before filling with Cu. Our results indicate that the O2∕(SF6+O2) ratio is a key parameter in determining the sidewall slope, however the electrode bias and chamber pressure are critical...

A Physics Based Comprehensive Mathematical Model to Predict Motor Performance in Hybrid Rocket Propulsion Systems

Abstract: A comprehensive physics based mathematical model is proposed to predict motor performance (as it relates to regression rate, combustion instabilities, and shifts in chamber pressure) in hybrid rocket propulsion systems. The model is based on an unsteady, twodomain (solid fuel and gaseous oxidizer with a moving interface) concept, where both domains are assumed to be two-dimensional. The combustion of the ablated fuel is modeled by a single reaction, three species chemical reaction equation. The gas domain is assumed to be viscous, turbulent, and compressible. The two domains are coupled through an energy balance equation at the interface that includes mass exchange due to ablation and heat exchange due to conduction and radiation. The solution procedure requires that a time and space dependent transformation is applied in the radial direction to the governing differential equations to obtain a rigid (non-moving) interface between the two domains. The transformed equations for the gas domain are solved using the CMSIP technique. The solution method is verified using two benchmark cases (driven cavity flow and flow through a channel.) Finally, the proposed comprehensive mathematical model is used to predict the unsteady temperature and pressure distributions, and the velocity field in the gas domain and the temperature distribution in the solid fuel as well the regression rate at the gas-solid interface during the ignition and burning of the solid fuel.

A Basic Experimental Study of Gasoline Direct Injection at Significantly High Injection Pressures

Abstract: In gasoline direct injection engines with stratified-combustion strategies only a short time is available for mixture preparation. Therefore, investigations are carried out to evaluate the influence of high injection pressure up to 50 MPa in order to optimize the mixture preparation. Two types of multi-hole injectors are analyzed in a pressure vessel under various pressure and temperature conditions. Laser light sheet visualization technique is applied in order to determine spray characteristics like shape, angle, penetration depth and spray width. To determine the velocity of the air surrounding the spray, a PIV (Particle Image Velocimetry) measurement technique is used. Droplet sizes and velocities are measured with a Phase Doppler Anemometer (PDA) in different positions in the spray center and at the spray edge. Spray visualization experiments show the influence of evaporation on spray propagation at higher temperatures. With increasing chamber pressure, a widening of the jet is observed, while its length remains nearly constant. PIV-measurements show a torus-like flow at the spray front and a distinctive air entrainment into the spray, which depends on injection pressure and chamber pressure. Analyses of droplet velocity and diameter with PDA reveal high velocities of very small droplets at higher injection pressures. However, droplet velocity does not increase in the same dimension as does the fuel pressure.

Oxidizer Control and Optimal Design of Hybrid Rockets for Small Satellites

Abstract: The parameters that affect the design of a hybrid rocket for small satellites are highlighted, and the benefit of the oxidizer flow rate control is analyzed. A single-port circular-section polyethylene grain is considered; the oxidizer is 85% hydrogen peroxide. The engine design is optimized to search for the minimum engine mass when the initial satellite mass and the required velocity increment are assigned. First, the simplest blowdown feed system is considered. The analysis shows that the optimal design depends on a lower limit for the regression rate and sometimes on a further constraint, which is related to the occurrence of thermal choking. The initial values of the mixture ratio, the thrust level and the initial port area to the throat area ratio seem to be the most important parameters for an optimal design. As far as the oxidizer flow rate control is concerned, several control strategies, namely, constant mixture ratio, repressurization, constant combustion chamber pressure, and constant propellant tank pressure, are compared to the simplest blowdown system. The constant mixture ratio control is the worst case, as the mass and volume are similar to the blowdown case, while a large thrust variation occurs. Repressurization reduces the thrust variation. Constant pressure controls (both combustion chamber and tank pressures) guarantee a quasi-constant thrust and reduce engine dimensions, with a limited mass penalty.

Design and characteristics of a superconductor bearing

Abstract: A high-temperature superconductor (HTS) journal bearing was designed for a flywheel energy storage system. A rotor was supported at top and bottom by two HTS bearings. The rotor weight is 4 kg and the length and diameter of shaft were about 300 mm and 40 mm, respectively. Both the top and bottom bearings have two permanent magnet (PM) rings with an iron pole piece separating them. Static properties of the bearing were calculated by frozen image method and verified by experiments. The vertical stiffness of the bearing was 38.9 N/mm. The rotational drag and vibration were measured up to 8000 rpm. The loss coefficient was linear up to 8000 rpm and the final value was 7.5/spl times/E-6. The average of vibration was about 10 micrometer (zero/spl I.bar/peak) except the resonance speed range. Rotation tests were conducted over the same speed range at several chamber pressures. Chamber pressure of 0.4 mtorr is sufficiently low to minimize windage loss.

Neutral density map of Hall thruster plume expansion in a vacuum chamber

Abstract: A neutral background pressure map of the large vacuum test facility (LVTF) is presented. The LVTF is mapped at cold anode flow rates of 5.25, 10.46, and 14.09mg∕s. In addition, neutral background pressure maps are created at hot anode (i.e., discharge on) flow rates of 5.25 and 10.46mg∕s for discharge voltages of 300 and 500V, corresponding to P5 Hall thruster operating conditions ranging from 1.5to5.0kW. The chamber pressure is mapped at nominal xenon pumping speeds of 140 000 and 240000l∕s. The pressure map is performed with a rake consisting of five calibrated Bayard–Alpert hot-cathode ionization gauges. The plume expansion appears to be independent of anode flow rate and facility background pressure. Analysis of axial pressure profiles on the LVTF’s centerline shows that the plume pressure decreases from a maximum at the thruster exit plane down to the facility background pressure at approximately 2m downstream of the exit plane. Comparison of axial pressure profiles on the LVTF’s centerline shows tha...

Pressure monitor for cryoablation catheter

Abstract: A cryoablation device having a pressure monitoring system includes an elongated catheter tube that has a central lumen and is formed with a closed distal end. The distal end of a refrigerant supply line is positioned in the central lumen and distanced from the catheter tube’s distal end to establish an expansion chamber therebetween. A return line, which can be established between the supply line and the catheter tube or can include a return tube, is provided to exhaust expanded refrigerant from the chamber. First and second pressure sensors are respectively positioned in the supply line upstream from the expansion chamber and in the return line. Typically, both sensors are positioned to remain at extracorporeal locations throughout a cryoablation procedure. Measured pressures are used together with the supply and return line dimensions to analytically estimate the chamber pressure and allow the expansion of refrigerant in the chamber to be monitored.

Volume-based characterization of postocclusion surge

Abstract: Purpose To propose an alternative method to characterize postocclusion surge using a collapsible artificial anterior chamber to replace the currently used rigid anterior chamber model. Setting Fundacion Oftamologica Los Andes, Santiago, Chile. Methods The distal end of a phacoemulsification handpiece was placed inside a compliant artificial anterior chamber. Digital recordings of chamber pressure, chamber volume, inflow, and outflow were performed during occlusion break of the phacoemulsification tip. The occlusion break profile of 2 different consoles was compared. Results Occlusion break while using a rigid anterior chamber model produced a simultaneous increase of chamber inflow and outflow. In the rigid chamber model, pressure decreased sharply, reaching negative pressure values. Alternatively, with the collapsible chamber model, a delay was observed in the inflow that occurs to compensate the outflow surge. Also, the chamber pressure drop was smaller in magnitude, never undershooting below atmospheric pressure into negative values. Using 500 mm Hg as vacuum limit, the Infiniti System (Alcon) performed better that the Legacy (Alcon), showing an 18% reduction in peak volume variation. Conclusions The collapsible anterior chamber model provides a more realistic representation of the postocclusion surge events that occur in the real eye during cataract surgery. Peak volume fluctuation (mL), half volume recovery time(s), and volume fluctuation integral value (mL × s) are proposed as realistic indicators to characterize the postocclusion surge performance. These indicators show that the Infiniti System has a better postocclusion surge behavior than the Legacy System.

Experimental Study of Combustion Instabilities in a Single-Element Coaxial Swirl Injector

Abstract: *† † ‡ A single injector element liquid rocket combustion experiment was designed and conducted to provide insight into combustion dynamics and to develop an effective tool to rate the stability of injectors prior to a full-scale engine build. A gas-centered, liquid swirl coaxial injector element was selected for the study. Kerosene and a mixture of superheated water and oxygen vapor were used as the liquid fuel and gaseous oxidizer, respectively. The lengths of the oxidizer injection post and combustion chamber were tested at stabilizing and destabilizing combinations. The variable length combustion chamber was discretely varied between 25.4 and 88.9 cm. The mean chamber pressure ranged from 2.14 – 2.38 MPa. Nine of the ten tests exhibited strong instabilities with amplitudes of 0.69 to 1.38 MPa peak to peak, and wave slopes on the order of 10 9 Pa/s. The unstable frequencies ranged from 1184 Hz to 1721 Hz. A noted decrease in combustion efficiency accompanied increasing strength of the instabilities. One test, with a 25.4 cm chamber, was classically stable with pressure oscillation amplitudes less than 5% of the mean pressure. Resonant frequencies calculated from a linear model developed to solve the coupled injector-chamber acoustics were always within 6% of the measured unstable frequency. The acoustics model also indicated that there were available system resonances that were not excited by the combustion process, possibly indicating a sensitive bandwidth of the injector response.

Thermal Decomposition of Hydrogen Peroxide, Part I: Experimental Results

Abstract: Thermal decomposition is an important process in propulsion systems that use hydrogen peroxide (HP). Neither a combined vaporization-decomposition model nor a fundamental understanding of the way liquid HP vaporizes and decomposes in these rocket applications exist. Results are presented from an experimental study of the combined thermal decomposition of HP at rocket-type conditions. A liquid spray of HP is injected into a cross stream of HP decomposition products at chamber pressures ranging from 2.0 to over 5.5 MPa. Two injectors with different orifice diameters are used. Experimental parameters include flow rates of the decomposition products and liquid injectant, HP concentration, chamber geometry, and momentum ratio between the liquid injectant and the decomposition stream. A decomposition efficiency of the liquid HP is determined based on the ratio between measured chamber pressure and chamber pressure calculated by equilibrium chemistry. An analysis of the crossflow injection is used to assess the effects of spray trajectory. Decomposition efficiencies ranging between 10 and 90% were measured. The results show that decomposition efficiency is inversely proportional to the fractional amount of liquid injectant flow rate, linearly proportional to residence time, and that higher concentration HP decomposes at a faster rate.

Impact of Cubic Pin Finned Surface Structure Geometry Upon Spray Cooling Heat Transfer

Abstract: Experiments were conducted to study the effects of enhanced surface structures on heat flux using spray cooling. The surface enhancements consisted of cubic pin fins machined on the top surface of copper heater blocks. The structure height, pitch, and width were parametrically vaned. Each copper block had a projected cross-sectional area of 2.0 sq cm. Measurements were also obtained on a heater block with a flat surface for baseline comparison purposes. A 2 x 2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data were obtained under nominally degassed (chamber pressure of 41.4 kPa) and gassy conditions (chamber with N2 gas at 100.7 kPa) with a bulk fluid temperature of 20.5 C. Results for both the degassed and gassy cases show that structure width and separation distance have a dominant effect upon the heat transfer for the size ranges used. Cubic pin fin height had little impact upon heat flux. The maximum critical heat flux (CHF) attained for any of the surfaces was 121 W/sq cm, giving an enhancement of 51% relative to the flat surface case under nominally degassed conditions. The gassy case had a maximum CHF of 149 W/sq cm, giving an enhancement of 38% relative to the flat surface case.

Optimization of the freeze-drying cycle: adaptation of the pressure rise analysis model to non-instantaneous isolation valves.

Abstract: The principal aim of this study is to extend to a pilot freeze-dryer equipped with a non-instantaneous isolation valve the previously presented pressure rise analysis (PRA) model for monitoring the product temperature and the resistance to mass transfer of the dried layer during primary drying. This method, derived from the original MTM method previously published, consists of interrupting rapidly (a few seconds) the water vapour flow from the sublimation chamber to the condenser and analysing the resulting dynamics of the total chamber pressure increase. The valve effect on the pressure rise profile observed during the isolation valve closing period was corrected by introducing in the initial PRA model a valve characteristic function factor which turned out to be independent of the operating conditions. This new extended PRA model was validated by implementing successively the two types of valves and by analysing the pressure rise kinetics data with the corresponding PRA models in the same operating conditions. The coherence and consistency shown on the identified parameter values (sublimation front temperature, dried layer mass transfer resistance) allowed validation of this extended PRA model with a non-instantaneous isolation valve. These results confirm that the PRA method, with or without an instantaneous isolation valve, is appropriate for on-line monitoring of product characteristics during freeze-drying. The advantages of PRA are that the method is rapid, non-invasive, and global. Consequently, PRA might become a powerful and promising tool not only for the control of pilot freeze-dryers but also for industrial freeze-dryers equipped with external condensers.

A modified plasma arc gas condensation technique to synthesize nanocrystalline tungsten oxide powders

Abstract: In the present study, nanocrystalline tungsten oxide powders were prepared by a modified plasma arc gas condensation technique where a gas nozzle was introduced to provide blowing gas. With the aid of the blowing gases, nanocrystalline tungsten oxide powders can be prepared under various chamber pressures ranged from 4.9 to 101.3 kPa. The mean grain size and powder production rate of the as-prepared nanocrystalline WO3 powders increased with increasing chamber pressure. For an increasing chamber pressure from 4.9 to 101.3 kPa, asignificant increase in powder production rate from 0.374 to 13.658 g/h can be noticed, while the mean grain size only enlarged acceptably from 5.9 to 15.7 nm. Meanwhile, by controlling the partial oxygen pressure of the mixed gas, nanocrystalline blue tungsten oxide powders can be prepared successfully. The blowing mixed gas from the nozzle not only suppressed the nucleation and growth for powders from the gas phase, but can be used to prepare stoichiometric or nonstoichiometric tungsten oxide powders.

Linked Solid Rocket Motor Combustion Stability and Internal Ballistics Analysis

Abstract: Despite many decades of study, new solid rocket motor systems frequently experience unsteady gas motions and associated motor vibrations. This phenomenon most often occurs when a combustion chamber’s acoustic modes couple with combustion/flow processes. Current linear models of the sort used in the Standard Stability Prediction program (SSP) are designed to predict the tendency for a SRM to become unstable, but they do not provide any information on the severity of the instability (usually measured by the limit cycle amplitude of the oscillations) or on the triggerability (the tendency of an otherwise stable system to oscillate when pulsed with a sufficiently large disturbance) of the system. The goal of our present work is to incorporate a nonlinear capability into the JANNAF Solid Performance Program (SPP’04TM), a grain design and ballistics code maintained by Software and Engineering Associates, Inc. (SEA). SEA has encoded a new nonlinear model into SPP’04TM that allows for an interaction between the combustion instability and the mean internal ballistics. This approach yields both a DC shift in the mean chamber pressure and a limit in the amplitude of the oscillatory pressure. The enhanced capability of the SPP’04TM is demonstrated by comparing the experimental and numerical chamber pressure histories of a pulsed solid rocket motor.

Vacuum processing apparatus and vacuum processing method

Abstract: The downtime of a vacuum processing apparatus due to wet cleaning is reduced. In a vacuum processing apparatus that requires aging for its chamber or process container after vacuum evacuation of the apparatus and before actual processing of a workpiece, when the chamber has been opened to atmosphere for the purpose of wet cleaning or component replacement, the apparatus comprises a high precision absolute pressure gauge for use in processing, a wide range gauge capable of measuring a wide range of pressures, and a controller, wherein the controller uses a pressure trend during vacuum evacuation to determine whether the vacuum evacuation is satisfactory, and starts aging upon determining that the vacuum evacuation is satisfactory even if the actual pressure is not below a prescribed value. The controller determines relationship between an apparent flow rate (leak rate) measured by the absolute pressure gauge when the chamber is vacuum sealed, and a chamber pressure measured by the wide range gauge, and then measures only the pressure to determine whether a baseline leak rate is reached.

Firing-Tests of a Rocket Combustor for Combined Cycle Engine at various conditions

Abstract: A gaseous hydrogen / gaseous oxygen rocket chamber was designed to fit to a RocketBased-Combined-Cycle engine model, and its performances were evaluated experimentally. The rocket chamber was required to operate at a very wide operation range in terms of chamber pressure (Pc) and mixture ratio (O/F); 0.6 MPa & 6 for ‘ramjet-mode’ operation, 0.6 MPa & 0.5 for ‘scramjet-mode’ operation, and 5 MPa & 7 for ‘ejector-rocket-mode’ operation. For stable operation, both gaseous hydrogen injectors and gaseous oxygen injectors, which were aligned co-axially, had choking point and diffuser at downstream portion. The number of the oxygen injector in use could be selected. The outer hydrogen injector showed lower discharge coefficient and lower durability against back-pressure than the inner oxygen injector. The hot-firing tests with a heat-sink type combustion chamber showed stable operation with the C-star efficiency of 87% for the ramjet-mode operation and 83% for the scramjet-mode operation. The hot-firing tests with a water-cooled combustion chamber also showed stable operation with the C-star efficiency of 95% for the ejector-rocket-mode operation. The water-cooled chamber showed enough durability in the ejector-rocket-mode operation, however, serious thermal damages upon the tip of injector elements and the chamber faceplate were observed, requiring more modification in the design around the injector and the faceplate.

Luminescence lifetime response of pressure-sensitive paint to a pressure transient

Abstract: Pressure-sensitive paint (PSP) is used to acquire high-fidelity images of steads pressure distributions across surfaces. The PSP luminescence emission response to excitation light depends in a straightforward way on the oxygen concentration (hence air pressure) and the irradiance incident on the PSP lumiphores. Often, however, the phenomenon of interest is unsteady. During a rapid change in pressure. the oxygen concentration within a PSP layer varies with depth. Moreover, the excitation irradiance varies with depth as a result of attenuation, and this affects signal generation when the spatial distribution of oxygen is also changing. Prior studies have been reported on the transient response of PSP using the radiometric technique to detect pressure, we have extended the study by applying a luminescence lifetime technique. Oxygen concentration as a function of time and depth are obtained by solving the mass diffusion equation. with appropriate initial and boundary conditions. We develop a luminescence emission model that takes the spatially varying oxygen concentration and excitation absorption profile into account and relate pressure to the lifetime of the luminescence emission. Oxygen concentration is governed by mass diffusion of oxygen through a PSP layer during a rapid change in pressure, and the absorption of excitation light is governed by Beer's law. The significance of both the mass diffusivity and the optical depth of PSP are assessed. A numerical method was used to solve the mass diffusion equation that allows modeling of the oxygen concentration within the PSP given an arbitrary pressure function. We have used a double-image digital camera to acquire PSP emission lifetime data from several paint thicknesses during a rapid change in pressure. These data were compared to the results predicted by the model.

Down hole air diverter

Abstract: A down hole air diverter having a first opening in communication with the central passageway of a drillstring; a second opening in communication with the well bore annulus; and a means to control the flow of pneumatic fluid between the first opening and the second opening. The means to control the flow further includes a first sealing means and a first biasing means to control the first sealing means. The first sealing means allows communication with the well bore annulus when the well bore annulus pressure exceeds the first biasing means pressure and prevents communication when the bias pressure exceeds the bore annulus pressure. A second sealing means prevents communication with the drillstring when the pressure from the second sealing means chamber exceeds the first opening pressure and allowing communication when the first opening pressure exceeds the chamber pressure.

Ion exchange membrane-type electrolytic cell

Abstract: PROBLEM TO BE SOLVED: To solve the problem that, in a two chamber process ion exchange membrane type electrolytic cell using a gas diffusion electrode, the liquid pressure of an anode chamber is different according to liquid depth, and the liquid pressure is applied to an anode and an ion exchange membrane, and easily causes the damage and deformation of these members. SOLUTION: A cushioning material 10 is stored between the back plate 9 of a cathode gas chamber in the body 1 of the ion exchange membrane type electrolytic cell and a gas diffusion electrode 7 in such a manner that the reaction force thereof is made higher in the lower part of the cathode gas chamber than the upper part of the cathode gas chamber. By weakening the reaction force of the cushioning material as it goes to the upper part in accordance with the differential pressure between the anode chamber pressure and the cathode gas chamber pressure, the application of the excessive pressure to the ion exchange membrane is prevented, so as to prevent the generation of damage or the like. COPYRIGHT: (C)2007,JPO&INPIT

The impact of oil and sealing air flow, chamber pressure, rotor speed, and axial load on the power consumption in an aeroengine bearing chamber

Abstract: Trends in aircraft engines have dictated high speed rolling element bearings up to 3 million DN or more with the consequence of having high amounts of heat rejection in the bearing chambers and high oil scavenge temperatures. A parametric study on the bearing power consumption has been performed with a 124 mm pitch circle diameter (PCD) ball bearing in a bearing chamber that has been adapted from the RB199 turbofan engine (DN∼2 × 10 6 ) The operating parameters such as oil flow, oil temperature, sealing air flow, bearing chamber pressure, and shaft speed have been varied in order to assess the impact on the power consumption. This work is the first part of a survey aiming to reduce power losses in bearing chambers. In the first part, the parameters affecting the power losses are identified and evaluated.

Inclusion of aerodynamic non-equilibrium effects in supersonic plasma jet enthalpy probe measurements

Abstract: Low pressure plasma spraying (LPPS) is a thermal spraying technique that has found a niche for low oxidation products. It uses a low pressure environment (i.e., chamber pressure between 2 and 90 kPa) and yields supersonic plasma jets. The enthalpy probe technique is a common measurement method in plasmas. However LPPS jets are difficult to diagnose as their supersonic nature forces the apparition of a shock wave in front of any measuring device inserted in the jet. Incomplete or erroneous assumptions are usually invoked to overcome the difficulties associated with this shock wave and carry out the LPPS jet diagnosis from enthalpy probe measurements. In this work, a new device is designed to gain access to an additional physical quantity, which is needed to assess the aerodynamic non-equilibrium state of the jet. It is combined with enthalpy probe measurements, and the resulting set of experimental data is used with a numerical procedure based on gas dynamics theory, yielding free-stream supersonic plasma jet values from the measurements behind the induced shock wave. The results agree well with the phenomenology of supersonic jets in aerodynamic nonequilibrium. However this new method is restricted by the local thermodynamic equilibrium assumption, which is directly linked with the pressure and temperature conditions of the plasma jet.

Sidewall profile control of thick benzocyclobutene reactively ion etched in CF4∕O2 plasmas

Abstract: The feasibility of controlling the sidewall angle of thick benzocyclobutene (BCB) etched in a CF4∕O2 plasma using thick photoresist as an etch mask has been investigated. Sidewall angle, BCB etch rate, and BCB to photoresist selectivity as functions of chamber pressure and CF4 to O2 ratios are reported. Through the use of postdeveloped reflown photoresist, an optimum sidewall angle of less than 60° was achieved at 33mT chamber pressure and a 19% CF4∕O2 ratio. The method presented here achieves deep, residue-free etching of thick BCB with a sidewall profile suitable for e-beam evaporated and lifted metal for use in vertical interconnects.