Test of a Fluid-Film Wave Bearing at 350°C with Liquid Lubricants

A novel fluid-film wave bearing has been run at a higher temperature (350°C) than ever before with a perfluoropolyether (PFPE)-K liquid lubricant. Additionally, the wave journal bearing (45 mm diameter and 24 mm long) completed an 8-h endurance test at the NASA Glenn Research Center. The lubricant was PFPE-K XHT 500. After being maintained at 350° C for 8 h, the bearing temperature was raised to 356°C for the last 30 min of the run. The speed was 29,000 rpm and the load ranged from 2670 to 3560 N. The bearing was perfectly stable both dynamically and thermally. The observed temperature was more than 150°C above that run with current turbine engine lubricants. The use of high-temperature bearings as tested here would allow efficiency increases of more than 5% in aero or terrestrial turbine engines.     

Void-fraction measurement with high spatial resolution in a 5×5 rod bundle by linear-accelerator-driven X-ray computed tomography over a wide pressure range

Void fraction (i.e., the volume fraction occupied by gas) is a key parameter for determining the coolability and neutron-moderating performance of a water-cooled nuclear reactor. To develop computational multi-fluid dynamics models for determining the void-fraction distribution, experimental data of comparable quality are required. We have developed a high-energy X-ray computed tomography (CT) system to acquire three-dimensional void-fraction distributions. The CT system comprises a linear-accelerator-driven high-energy X-ray source and a linear detector array. We quantified a boiling two-phase flow in a 5 × 5 heated rod bundle at high pressure, simulating a fuel-rod bundle in a boiling water reactor (BWR). Because the axial travel of the CT system is 4 m and includes the entire BWR fuel-rod bundle, we optimized the CT imaging conditions and reconstruction method for rod-bundle visualization to reduce uncertainties due to density fluctuations in the boiling flow and imaging artifacts. We conducted a boiling experiment at a low flow rate and low thermal power and acquired three-dimensional distributions of the void fraction over a wide pressure range of 0.1–7.2 MPa. The experiment provided three-dimensional void-fraction distributions with high spatial resolution, especially in subchannel regions surrounded by rods, and the results are suitable for validating three-dimensional thermal-hydraulic analysis codes.     

Numerical investigation on the installation effects of electromagnetic flowmeter downstream of a 90° elbow–laminar flow case

An electromagnetic flowmeter installed downstream of a 90° elbow to measure the flowrate of laminar flow is numerically simulated to investigate installation effects by varying the location of the electromagnetic flowmeter at a distance up to 22D from the elbow, and the angle between the electrodes plane and the symmetry plane of the elbow at ϕ=0, 45 and 90°. Effects of the curvature radius (R_c) and the Reynolds number (Re) based on a diameter D are also scrutinized in the range of 400≤Re≤1500 and R_c=1.5D and 3.0D.For the simulation of an electromagnetic flowmeter, a commercial code FLUENT(ver. 4.4) is applied for flow field analyses and a three-dimensional numerical code is developed for analyzing the magnetic field. The developed code adopts a finite volume method to solve a Poisson-type voltage equation for the magnetic field.It is found that the deviations of the flow signal due to the disturbance from the elbow is strongly dependent on the pattern of axial velocity contours. Cases for ϕ=45° are found to permit significantly better measurement accuracy in comparison with ϕ=0° and ϕ=90°, and the effect of the curvature on the optimum installation distance depends on the Reynolds number. The present numerical simulation method is found to be a useful tool for the performance analysis of the electromagnetic flowmeter.     

Numerical simulation of turbulent flow of hydraulic oil through 90° circular-sectional bend

Oil flow through pipe bends is found in many engineering applications. However, up to now, the studies of oil flow field in the pipe bend appear to be relatively sparse, although the oil flow field and the associated losses of pipe bend are very important in practice. In this paper, the relationships between the turbulent flow of hydraulic oil in a bend and the Reynolds number Re and the curvature ratio ? are studied by using computational fluid dynamics (CFD). A particular emphasis is put on hydraulic oil, which differs from air or water, flowing through 90° circular-sectional bend, with the purpose of determining the turbulent flow characteristics as well as losses. Three turbulence models, namely, RNG k-? model, realizable k-? model, and Reynolds stress model (RSM), are used respectively. The simulation results in the form of contour and vector plots for all the three turbulence models for pipe bends having curvature ratio of ??0.5, and the detailed pressure fields and total pressure losses for different Re and ? for RSM are presented. The RSM can predict the stronger secondary flow in the bend better than other models. As Re increases, the pressure gradient changes rapidly, and the pressure magnitude increases at inner and outer wall of the bend. When ? decreases, two transition points or transition zones of pressure gradient arise at inner wall, meanwhile, the transition point moves towards the inlet at outer wall of the bend. Owing to secondary flow, the total pressure loss factor k increases as the bend tightens, on the contrary, as Re increases, factor k decreases due to higher velocity heads, and the rapid change of pressure gradient on the surface of the bend leads to increasing of friction and separation effects, and magnified swirl intensity of secondary flow. A new mathematical model is proposed for predicting pressure loss in terms of Re and ? in order to provide support to the one-dimensional simulation software. The proposed research provides reference for the analysis of oil flow with higher Re in the large bends.     

An adaptive γ-ray spectrometer with a high event processing rate

A fast γ-ray spectrometer adaptable to the scintillator type is described. This spectrometer is capable of processing a γ-ray energy spectrum (with a resolution of <4% in the energy range from 20 keV to 10 MeV) in a sequence of time intervals in the real-time mode at a counting rate of up to 10⁶ cps. Digitization of the detector signals by a 14-bit ADC with a sampling rate of 64 MHz and real-time data stream processing are used to separate overlapping events and correctly generate energy spectra.     

Experimental and computational investigations of thermal modal parameters for a plate-structure under 1200 °C high temperature environment

When a hypersonic aircraft flies at a high Mach number, the plate-like attitude control structures, such as the wings and rudders, will be exposed to an extremely high-temperature environment. To obtain the thermal modal parameters of a structure that are difficult to measure, a high-temperature transient heating test system and a vibration test system were combined to establish a test system that can perform the thermal/vibration test at 1200 °C. Infrared radiation heating was employed to generate a controlled time-varying high-temperature environment, and an exciter was used to exert vibration excitation on the free end of the cantilever rectangular plate. A self-developed extension configuration of a high-temperature-resistant ceramic pole was used to transfer the vibration signals of the structure to a non-high temperature zone, and the acceleration sensors were applied to identify the vibration signals. The test data were analyzed using a time-frequency joint analysis technique, and next, the key vibration characteristic parameters of structure in a thermal-vibration coupled environment up to 1200 °C (e.g., the modal frequency and modal vibration shape) were experimentally obtained. In addition, the numerical simulation on the thermal modal characteristics of a rectangular plate was performed. The calculated results coincide favorably with the test results, verifying the credibility and effectiveness of the experimental methods. The research results can provide an important basis for the dynamic performance analysis and safety design of structure under high-temperature thermal-vibration conditions for hypersonic flight vehicles.     

Note: Fast, small, accurate 90° rotator for a polarizer

A permanent magnet stepper motor is modified to hold a dichroic polarizer inside the motor. Rotation of the polarizer by 90° ± 0.04° is accomplished within 80 ms. This device is used for measurements of the intensity ratio for two orthogonal linear polarized components of a light beam. The two selected polarizations can be rapidly alternated to allow for signal drift compensation, and the two selected polarizations are accurately orthogonal.     

An investigation of heat transfer characteristics of swirling flow in a 180° circular section bend with uniform heat flux

An experiment was performed to obtain the local heat transfer coefficient and Nusselt number in a circular duct with a 180° bend for Re=6X 10⁴, 8X 10⁴ and 1 X 10⁵ under swirling flow and non-swirling flow conditions. The test tube with a circular section was made from stainless steel having a curvature ration of 9.4. Current heat flux of 5.11 kW/m² was applied to the test tube by electrical power and the swirling motion of air was produced by a tangential inlet to the pipe axis at 180°. Measurements of local wall temperatures and the bulk mean temperatures of air were made at four circumferential positions at 16 stations. The wall temperatures showed a reduced distribution curve at the bend for the non-swirling flow, but this effect did not appear for the swirling flow. The Nusselt number distributions for the swirling flow, which was calculated from the measured wall and the bulk temperatures, were higher than that of the non-swirling flow. The average Nusselt number of the swirling flow increased by about 90-100%, compared to that of the non-swirling flow. The Nu/Nu_DB values at the 90° station for non-swirling flow and swirling flow were approximately 2.5 and 4.8 at Re=6X 10⁴ respectively. The values agree well with Said’s results for non-swirling flow.     

Detection of hand tremor in patients with Parkinson’s disease using a non-invasive laser line triangulation measurement method

Detection of hand tremor for evaluating and diagnosing early stage of Parkinson’s disease (PD) remains a challenge. The purpose of this study was to correlate hand tremors analyzed by a non-invasive method with clinical manifestations among patients with PD. Four different modes of tremor detection in patients with PD were detected individually using a laser line triangulation measurement (LLTM) method and off-line analyzed.The results showed a significant correlation between age at disease onset and tremor frequency obtained from the left hand and from the non-dominant hand. Furthermore, there was a significant positive correlation between disease duration and tremor frequency obtained from the left hand and from the non-dominant hand using different detection modes.We conclude that the laser line triangulation measurement is a non-invasive, non-contact, portable, easy-to-use and low cost method that can detect tremor early in the course of patients diagnosed with PD.     

μPIV measurement of grease velocity profiles in channels with two different types of flow restrictions

Grease is commonly used to lubricate various machine components such as rolling bearings and seals. In this paper the flow of lubricating grease passing restrictions is described. Such flow occurs in rolling bearings during relubrication events where the grease is flowing in the transverse (axial) direction through the bearing and is hindered by guide rings, flanges etc, as well as in seals where transverse flow occurs, for example during so-called breathing caused by temperature fluctuations in the bearing. This study uses a 2D flow model geometry consisting of a wide channel with rectangular cross-section and two different types of restrictions to measure the grease velocity vector field, using the method of Micro Particle Image Velocimetry. In the case of a single restriction, the horizontal distance required for the velocity profile to fully develop is approximately the same as the height of the channel. In the corner before and after the restriction, the velocities are very low and part of the grease is stationary. For the channel with two flow restrictions, this effect is even more pronounced in the “pocket” between the restrictions. Clearly, a large part of the grease is not moving. This condition particularly applies to the cases with a low-pressure drop and where high consistency grease is used. In practice this means that grease is not replaced in such “corners” and that some aged/contaminated grease will remain in seal pockets.     

Comparative study of electrostatic sensors with circular and probe electrodes for velocity measurement of pulverised coal

This paper presents recent progress on the velocity measurement of pulverised coal in pneumatic pipelines using electrostatic sensors in combination with correlation signal processing techniques.A comparative study of electrostatic sensors with circular and probe electrodes was conducted on a 94 mm bore horizontal pipeline in a 4 MW furnace.The advantages and limitations of both sensors are discussed.Experimental results demonstrate that both sensors are capable of providing pulverised coal velocity measurement with excellent repeatability and dynamic response.     

Wear test of cemented tungsten carbide at high atmospheric temperature (400°C)

Cemented tungsten carbide–cobalt (WC–Co) alloy has good mechanical properties, so it is widely used for cutting tools, wear-resistant dies and rolls, and shock-resistant punching dies. In this study, a wear test between cemented WC–Co alloy and carbon steel is carried out using a pin-on-disc wear-testing machine. The characteristics as to wear rate, coefficient of friction and surface roughness are investigated. Pin specimen and disc specimen surfaces are analyzed by a fluorescent X-ray analyzer. In addition, the wear characteristics of WC–Co alloy are confirmed by SEM observation of the microstructure of the cemented WC–Co alloy specimen. This revised version was published online in August 2006 with corrections to the Cover Date.     

2-ω and 3-ω temperature measurement of a heated microcantilever

This article describes temperature measurement of a heated atomic force microscope cantilever using the 2ω and 3ω harmonics of the cantilever temperature signal. When the cantilever is periodically heated, large temperature oscillations lead to large changes in the cantilever electrical resistance and also lead to nonconstant temperature coefficient of resistance. We model the cantilever heating to account for these sources of nonlinearity, and compare models with experiment. When the heating voltage amplitude is 17.9 V over the driving frequency range 10 Hz-34 kHz, the cantilever temperature oscillation is between 5?°C and 200?°C. Over this range, the corrected 2ω method predicts cantilever temperature to within 16% and the corrected 3ω method predicts the cantilever temperature within 3%. We show a general method for predicting the periodic cantilever temperature, sources of errors, and corrections for these errors.     

Note: Non-destructive measurement of thermal effusivity of a solid and liquid using a freestanding serpentine sensor-based 3ω technique

A non-destructive thermal effusivity characterization method described as a freestanding serpentine sensor-based 3ω technique was reported. This freestanding serpentine sensor was fabricated by the mature flexible printed circuit production technique. Expression for the temperature response of the freestanding serpentine sensor with respect to the thermal effusivity of the test sample was presented. The technique was further verified by measuring four kinds of standard samples at room temperature. Experimental results which well agree with reference values demonstrate the new technique is of great application value to thermal effusivity characterization of solids, liquids, and structures to which the conventional 3ω technique is not applicable, e.g., solids with porous surfaces.     

The European project on high temperature measurement solutions in industry (HiTeMS) – A summary of achievements

High temperature measurement in industry is subject to large uncertainties due to the non-ideal measurement conditions; for example unknown emissivity and window transmission for radiation thermometry, sensor contamination and ageing causing unpredictable drift in contact thermometry. This paper gives an overview of a European Metrology Research Programme (EMRP) project “High Temperature Metrology for Industrial Applications” (HiTeMS) whose objective was to address, on a broad front, a number of unsolved measurement challenges in the domain of high temperatures (above 1000 °C) both in non-contact and contact thermometry. It brought together a total of 15 partner organisations; National Metrology Institutes (NMIs) (10), industrial companies (4) and a Fraunhofer Institute. The project started in September 2011 and was completed August 2014. Significant progress has been made in all the temperature measurement challenges tackled.     

Studying key users’ skills of ERP system through a comprehensive skill measurement model

Given to the significant role of enterprise resource planning systems (ERP) in the current organizations, several studies have been accomplished regarding these systems. The Main reason for the present research is having a small share in enhancement of success rate of ERP systems implementation through an applied study. In this study two purposes are pursued. First, this article intends to determine the most important skills required by key users (Also called power users and super users.) of ERP system as one of the most major members of ERP implementation team. Another purpose is to examine the skills shortages of these users in organizations under study and both of these purposes are obtained based on a comprehensive model. This research includes two major parts. First, based on experts’ opinion, a model is developed to determine and measure required technical, human, and conceptual skills as well as skills shortages of those involved in ERP implementation such as key users. Then, in second part, based on the above model and by means of a field study and studying thirteen Iranian organizations, the desirable amount (Amount of skill that key users expected to have.) and existing amount (Amount of skill that key users have at present.) of skills of key users are measured in each one of the technical, human, and conceptual categories. Then in order to determine and evaluate skill shortages, the difference between these two amounts in each category is examined. In this paper, human and conceptual skills are determined as the most important skills of key users in ERP implementation. Also, results confirm that key users have skills shortages in three kinds of main skills (i.e., technical, human, and conceptual) in the organizations under study. Moreover, key users in large companies suffer more from skills shortages than ones in SMEs.     

Stability and dynamics of rotor system with 45° slant crack on shaft

Crack on a shaft is one of the common damages in a rotor system. In this paper, transverse vibrations are calculated to compare the influences of transverse crack and slant crack on the rotor system. Results show that the vibration amplitude of the rotor system with a 45° slant crack on the shaft is larger than that with a transverse crack when the two types of crack have the same depth and the rotor system runs in the same condition. Stability and dynamic characteristics of the rotor system with a 45° slant crack on the shaft under torsional excitation are analyzed by considering opening and closing of the crack. It is shown that the instability of the transverse vibration of the rotor system increases with increasing difference between the bending stiffness in two main directions, and the vibration is stable when the two bending stiffness are identical. The spectrum analysis of the steady-state response reveals that the gravity and the eccentricity produce different frequency components, and when the two bending stiffness are identical, the multiple frequency components of the torsional excitation disappear. Further investigation shows that the vibration amplitudes in combined frequencies increase rapidly in transversal, torsional, and axial vibration with increasing slant crack depth. The results are helpful for the understanding the dynamic behavior of a rotor system with a slant crack on a shaft and can be used for the detection of the slant crack on a shaft.     

Development of a Stereolithography File Interface with ArtCAM™

This paper presents the technique used for converting a 3D ArtCAM™ relief file into the stereolithography (STL) format. This 3D file is obtained from a 2D picture using a 3D CNC engraving software called ArtCAM™. The problem is to convert the 3D relief files into an STL format without compromising the accuracy and details of therelief. This paper discusses the size of the files which have been converted, and steps taken to reduce the file size by reducing the number of triangles or facets in the STL file. The discussion involves the verification of the converted model by comparing it with the original relief. The problems associated with the reduction of triangles when the file has been converted to STL format are also discussed.