Optimization of burning process of hydrocarbon fuels with varying specific heat of combustion

© Published under licence by IOP Publishing Ltd. This article explores the combustion of gaseous fuel in the case of an abrupt change of the specific heat of combustion. Analyzes the changes in the rate of heat when the fuel and air flows are constant. Defines the conditions for which retained the initial rate of heat release and optimal fuel-air ratio

Inspection of riveted connections by free oscillation technique.Inspection of riveted connections for “riveted wheel blades” at the production stage

© 2016, International Journal of Pharmacy and Technology. All rights reserved.The article presents the results of the production testing of the diagnostic system for quality instrumentation inspection for riveted connections with free oscillations technique. The test program consisted of four stages. In the first stage we selected guide cases which were new and spent a part of their resource having characteristic defects of riveted connections. In the second stage we formed reference spectra of inspected connections. At the third stage we established the relation between the numerical value of the Spearman correlation coefficient and the shear force of a blade. In the fourth stage, all tested connections were sent to additional riveting. Following the inspection with the free oscillations technique and on shear force, we have determined that shear force momentis constant and defective riveted connections were absent upon established rejectable quality levelis 0.75 of Spearman correlation coefficient. According to the tests results it is recommended to set the rejectable quality limit with regard to evaluation of Spearman correlation coefficient at 0.75that corresponds to 10 N m shear force moment of a blade. The developed inspection technique allows grading of riveted connection as “defected” and “fit” without unproductive manual inspection. Application of the technique allows quickly and with a high degree of certainty to reveal defective riveted connections in GTE guide cases what increases engine reliability and allows saving time and costs to determine the technical condition of gas turbine plants. The instrumental technique is implemented in the non-destructive inspection complex where the positioning of the inspected product, recording, analysis of vibro-acoustic signal and making conclusion on the conditions of a product is performed automatically, without operator intervention, that eliminates subjectivity in the decision-making

Testing method for riveted connections using the free oscillation technique. Numerical simulation

© 2016, International Journal of Pharmacy and Technology. All rights reserved.The article presents the results of studies on the development of methods and diagnostic system for instrumental quality control of riveted connections using the automated free oscillation technique. Based on the analysis of the known non-destructive testing methods of a riveted connection, it has been concluded that application of the free oscillation technique is very promising for quality control in the manufacture and repair of the gas turbine engine’s stators in order to identify different types of defects. The free oscillation technique (FOT) relies on excitation of freely damped elastic oscillations in a test object or part thereof and analysis of parameters of these oscillations. The FOT informative parameter is the change in the spectrum of free elastic oscillations of test objects. In order to accelerate the development of certain testing methods, the numerical experiments were carried out to determine the natural frequencies of suitable and defective riveted connections. Following the numerical simulation results, the optimal method of attaching a test disc to blades and informative frequency ranges were determined; they indicate that some defects of riveted connections are available

Control for riveted connections by free oscillation technique. Hardware and software system. Evaluation of measurement error

© 2016, International Journal of Pharmacy and Technology. All rights reserved.The paper presents the results of studies on the development of techniques and diagnostic suite for instrumentation control for quality of riveted joints by the free oscillation technique in automatic mode. The suite consists of a recording system and a signal processing system. The registration system includes a device for positioning the inspected articles. Excitation of oscillations in an inspected article is carried out with a calibrated strike. Signal processing system is composed of a hexadecimal analog-to-digit converter and a digital computer. Acoustic signals of vane vibrations are recorded on the hard disk, and their processing is performed with a software package. The description of DetectFault software created in LabVIEW environment. The software controls the movement of a guide wheel and a striker bar, ensures registration and transformation of signals from analog to digital form with the set number of samples and sampling interval value. The control algorithm is described. Acceptance or rejection of a riveted connection is made depending on the results of comparison of a reference and the current spectrum for the Spearman correlation coefficient and the rejectable level (higher - passed, below - rejected). To classify a riveted connection as “fit” or “defective”, an approach should be used that is specific to procedures on rejection of anomalies by a confidence interval. A robust weighting algorithm is used when forming the reference spectrum. The error estimation of the measurement results was carried out. The results of reproducibility of the data during the monitoring of riveted joints

Method of assessing the thermal state of the heat transfer surfaces

© 2018 Institute of Physics Publishing. All rights reserved. One of methods of increase in efficiency of the heat exchange equipment is timely detection of a sludge formation and scum on heat exchange surfaces. Deposits of salts and products of corrosion from technical water on the surface of heating of heat exchange devices reduce coefficient of a heat transfer and efficiency of heat exchange that leads to a considerable overexpenditure of energy carriers, overheating of surfaces of heating of coppers, decrease in service life, increase in costs of service and repair of the heat exchange equipment. Reliable methods and control devices of intensity of formation of deposits in the heat exchange equipment don't exist now. In work the method the express of control of thickness of deposits on heat exchange surfaces allowing to make control of a thermal condition of heat exchange surfaces is offered and in due time to carry out washing of devices

Evaluation of heat transporting losses due to changes of insulation properties during operation

© 2018 Institute of Physics Publishing. All rights reserved. The need for measuring the thermal conductivity of various materials exists in different fields of science and industry. First of all, it relate to constructing and power engineering. Thermal control allows evaluating the thermal insulation properties of the structure, identifying problem areas and assessing the energy efficiency of the pipeline. The paper assesses the transporting heat losses taking into account the actual operating conditions of the pipelines and the heterogeneity of the thermal insulation properties. A number of experiments were carried out. Experiments have shown that the destruction of insulation properties depends on such factors as the surface temperature of the pipe, the humidity of the environment, the service life

Heat and mass transfer processes caused by natural thermal convection in oil-containing media

Copyright 2017, Society of Petroleum Engineers. This article presents the results of experimental modeling of heat and mass transfer processes in oil-containing media caused by natural thermal convection. In this research we designed the laboratory setup and obtained experimental data for single- and two-component liquids medium with different permeability. It was shown that the dynamic of the media heating and the value of the oil recovery coefficient obtained experimentally and numerically by using the CMG STARS program coincides well. It was found that the processes of heat and mass transfer occur most intensively when the temperature of the medium near the heater reaches the value equals to the boiling point of water. The heating of the zone around the heater occurs faster, if a medium has a lower permeability. The oil recovery coefficient reached 55% with an initial water saturation coefficient of 0.52 and other conditions which corresponded to Ashalchinskoye oil field, Republic of Tatarstan, Russian Federation. This result is in a good agreement with the numerical result calculated by the CMG STARS program

Analysis of the heavy oil production technology effectiveness using natural thermal convection with heat agent recirculation method in reservoirs with varying initial water saturation

© Published under licence by IOP Publishing Ltd.The method of natural thermal convection with heat agent recirculation (NTC HAR) in oil reservoirs is described. The analysis of the effectiveness of this method for oil reservoir heating with the values of water saturation from 0 to 0.5 units is conducted. As the test element Ashalchinskoye oil field is taken. CMG STARS software was used for calculations. Dynamics of cumulative production, recovery factor and specific energy consumption per 1 m3 of crude oil produced in the application of the heat exchanger with heat agent in cases of different initial water saturation are defined and presented as graphs

Heating of heavy oil reservoirs using high-temperature heat agent recirculation

© Published under licence by IOP Publishing Ltd.The prospects of using high-temperature heat for heating oil reservoirs are estimated. Considered one of the possible schemes of heat agent recirculation flow implementation. The conditions of the developed scheme practical using are analyzed

Systematic search for VHE gamma-ray emission from X-ray bright high-frequency BL Lac objects

All but three (M87, BL Lac and 3C 279) extragalactic sources detected so far at very high energy (VHE) gamma-rays belong to the class of high-frequency peaked BL Lac (HBL) objects. This suggested to us a systematic scan of candidate sources with the MAGIC telescope, based on the compilation of X-ray blazars by Donato et al. (2001). The observations took place from December 2004 to March 2006 and cover sources on the northern sky visible under small zenith distances zd < 30 degrees at culmination. The sensitivity of the search was planned for detecting X-ray bright F(1 keV) > 2 uJy) sources emitting at least the same energy flux at 200 GeV as at 1 keV. In order to avoid strong gamma-ray attenuation close to the energy threshold, the redshift of the sources was constrained to values z<0.3. Of the fourteen sources observed, 1ES 1218+304 and 1ES 2344+514 have been detected in addition to the known bright TeV blazars Mrk 421 and Mrk 501. A marginal excess of 3.5 sigma from the position of 1ES 1011+496 was observed and has been confirmed as a source of VHE gamma-rays by a second MAGIC observation triggered by a high optical state (Albert et al. 2007). For the remaining sources, we present here the 99% confidence level upper limits on the integral flux above ~200 GeV. We characterize the sample of HBLs (including all HBLs detected at VHE so far) by looking for correlations between their multi-frequency spectral indices determined from simultaneous optical, archival X-ray, and radio luminosities, finding that the VHE emitting HBLs do not seem to constitute a unique subclass. The absorption corrected gamma-ray luminosities at 200 GeV of the HBLs are generally not higher than their X-ray luminosities at 1 keV.Comment: 15 pages, 7 figures, 5 tables, submitted to ApJ (revised version