Effect of operating conditions on gearbox noise

Low contact ratio spur gears were tested in the NASA gear noise rig to study the noise radiated from the top of the gearbox. The measured sound power from the gearbox top was obtained from a near field acoustic intensity scan taken at 63 nodes just above the surface. The sound power was measured at a matrix of 45 operating speeds and torque levels. Results are presented in the form of a spectral speed map and as a plot of sound power versus torque (at constant speed) and as sound power versus speed (at constant torque). Because of the presence of vibration modes, operating speed was found to have more impact on noise generation than torque level. A NASA gear dynamics code was used to compute the gear tooth dynamic overload at the same 45 operating conditions used for the experiment. Similar trends were found between the analytical results for dynamic tooth overload and experimental results for sound power. Dynamic analysis may be used to design high quality gears with profile relief optimized for minimum dynamic load and noise

Limited operating conditions of the jet mill injector

Наведено три критичні режими роботи інжектору струминного млина та показано умови їх виникнення. Знайдено коефіцієнти інжекції щодо розглянутих критичних режимів.Представлены три критических режима работы инжектора струйной мельницы и показаны условия их возникновения. Найдены коэффициента инжекции, соответствующие рассмотренным критическим режимам.Представлены три критических режима работы инжектора струйной мельницы и показаны условия их возникновения. Найдены коэффициента инжекции, соответствующие рассмотренным критическим режимам

Optimal operating conditions of an entangling two-transmon gate

We identify optimal operating conditions of an entangling two-qubit gate realized by a capacitive coupling of two superconducting charge qubits in a transmission line resonator (the so called "transmons"). We demonstrate that the sensitivity of the optimized gate to 1/f flux and critical current noise is suppressed to leading order. The procedure only requires a preliminary estimate of the 1/f noise amplitudes. No additional control or bias line beyond those used for the manipulation of individual qubits are needed. The proposed optimization is effective also in the presence of relaxation processes and of spontaneous emission through the resonator (Purcell effect).Comment: 12 pages, 5 figure

Performance of the ATLAS Precision Muon Chambers under LHC Operating Conditions

For the muon spectrometer of the ATLAS detector at the large hadron collider (LHC), large drift chambers consisting of 6 to 8 layers of pressurized drift tubes are used for precision tracking covering an active area of 5000 m2 in the toroidal field of superconducting air core magnets. The chambers have to provide a spatial resolution of 41 microns with Ar:CO2 (93:7) gas mixture at an absolute pressure of 3 bar and gas gain of 2?104. The environment in which the chambers will be operated is characterized by high neutron and background with counting rates of up to 100 per square cm and second. The resolution and efficiency of a chamber from the serial production for ATLAS has been investigated in a 100 GeV muon beam at photon irradiation rates as expected during LHC operation. A silicon strip detector telescope was used as external reference in the beam. The spatial resolution of a chamber is degraded by 4 ?m at the highest background rate. The detection efficiency of the drift tubes is unchanged under irradiation. A tracking efficiency of 98% at the highest rates has been demonstrated

Torrefaction of biomass: influence of operating conditions on products and grindability

Biomass is a renewable fuel, increasingly considered as an important resource for alternative fuels with significant environmental advantages. Thermo-chemical conversion of biomass is a mean to produce energy and to reduce greenhouse gases. Rapid gasification of biomass at high temperature is one of the most promising technologies for the syngas production and can be achieved in several seconds in an entrained flow reactor. At high temperature (1400°C), it is possible to obtain a syngas (CO, H2 and CO2) containing very small amounts of residual hydrocarbons and solid carbon (char). Heat and mass transfers are very effective in this kind of reactor, but the biomass must be dried and ground to particles measuring several hundreds of micrometers prior to injection. These preliminary steps, especially grinding, consume large amounts of energy and represent obstacles that need to be overcome in order to expand the use of biomass in thermo-chemical processes. Torrefaction is a technology which allows moisture and low weight organic volatile components of biomass to be removed, producing a hydrophobic solid residue with an increased energy density (on a mass basis) and greatly reduced grinding energy consumption compared to fresh biomass1. Electricity requirements for size reduction of torrefied wood are 50 to 85 % smaller in comparison with fresh wood2. In this work, a specially designed crossed fixed-bed reactor was used to characterise influence of operating conditions on torrefied biomass properties. Condensable species were recovered thank to a cooling device afterwards the crossed fixed bed; gaseous species were continuously quantified by a ?GC. Mass balance was evaluated by quantification of the biomass mass loss and species released. The nature of biomass (wood, straw) was considered. For each sample of torrefied biomass, mass loss, proximate analysis and lower heating value were quantified. The torrefied wood grindability was evaluated thank to the energy consumption of a specific grinder. (Texte intégral

Determination of the Joint Confidence Region of Optimal Operating Conditions in Robust Design by Bootstrap Technique

Robust design has been widely recognized as a leading method in reducing variability and improving quality. Most of the engineering statistics literature mainly focuses on finding "point estimates" of the optimum operating conditions for robust design. Various procedures for calculating point estimates of the optimum operating conditions are considered. Although this point estimation procedure is important for continuous quality improvement, the immediate question is "how accurate are these optimum operating conditions?" The answer for this is to consider interval estimation for a single variable or joint confidence regions for multiple variables. In this paper, with the help of the bootstrap technique, we develop procedures for obtaining joint "confidence regions" for the optimum operating conditions. Two different procedures using Bonferroni and multivariate normal approximation are introduced. The proposed methods are illustrated and substantiated using a numerical example.Comment: Two tables, Three figure

Droplet size and morphology characterization for diesel sprays under atmospheric operating conditions

The shape of microscopic fuel droplets may differ from the perfect sphere, affecting their external surface area and thus the heat transfer with the surrounding gas. Hence there is a need for the characterization of droplet shapes, and the estimation of external surface area, in order to enable the development of physically accurate mathematical models for the heating and evaporation of diesel fuel sprays. We present ongoing work to automat-ically identify and reconstruct the morphology of fuel droplets, primarily focusing in this study on irregularly-shaped, partially-deformed and oscillating droplets under atmospheric conditions. We used direct imaging tech-niques based on long-working distance microscopy and ultra-high-speed video to conduct a detailed temporal investigation of droplet morphology. We applied purpose-built algorithms to extract droplet size, velocity, vol-ume and external surface area from the microscopic ultra-high-speed video frames. High resolution images of oscillating droplets and a formation of a droplet form ligament, sphericity factors, volume as well as external surface area are presented for 500 bar injection pressure in the near nozzle region (up to 0.7 mm from nozzle exit) under atmospheric conditions. We observed a range of different liquid structures, including perfectly spher-ical, non-spherical droplets and stretched ligaments. We found that large droplets and ligaments exceeding the size of the nozzle hole could be found at the end of injection. In order to estimate droplet volume and external surface area from two-dimensional droplet information, a discrete revolution of the droplet silhouette about its major centroidal axis was used. Special attention was paid to the estimation of actual errors in the prediction of volume and surface characteristics from a droplet silhouette. In addition to the estimation of droplet volume and external surface area, the actual shape reconstruction in 3D coordinates from a droplet silhouette was performed in order to enable future numerical modelling studies of real droplets

Experimental tests of the operating conditions of a micro gas turbine device

The aim of this work is to analyze the performance of a commercial micro gas turbine, focusing on the analysis of the fuel consumption and the outlet compressor and turbine temperature at various rpm, and to evaluate and compare the efficiency of the device. A test bench has been assembled with the available equipment in the laboratory of the department of mechanical and aerospace engineering in Roma. By using the software supplied by the manufacturer, the evaluation of the operating performance of the device at different speeds has been performed, obtaining all the values of interest

Accurate Extraction of Noise Source Impedance of an SMPS Under Operating Conditions

An accurate measurement method to extract the common mode (CM) and the differential mode (DM) noise source impedances of a switched mode power supply (SMPS) under its operating condition is developed and validated. With a proper pre-measurement calibration process, the proposed method allows extraction of both the CM and the DM noise source impedances with very good accuracy. These noise source impedances come in handy to design an electromagnetic interference (EMI) filter for a SMPS systematically with minimum hassl