Abstract: This study aims to determine the effect of the percentage of CO2 in the biogas to the characteristics of biogas diffusion flame. Counterflow configuration was used in this study to investigate detail structure of diffusion flame and the flame stability of biogas. The concentration of CO2 in the biogas was varied from 0% to 50% while the mass flow rate of the reactants was varied from 4 to 14 L / min. The results showed that the CO2 in the biogas fuel affect the diffusion flame characteristics, especially the area of luminous yellow flame formed in the fuel flow. In the low oxygen concentration, percentage of CO2 did not affect the diffusion flame stability. However, the flame stability was more influenced by the rate of diffusion between fuel and oxygen. Therefore, the combustion of biogas is more recommended to be done in the low oxygen concentration.
Abstract: In this study, the inert effects of CO2 on the flammability limit and flame propagation of LPG has been investigated experimentally. The observation was done using cubic combustion bomb with the dimension of 500 mm x 200 mm x 10 mm. The results showed that the lower flammability limit (LFL) of LPG-Air mixtures is found to be 2.7% (by volume) and upper flammability limit (UFL) is 8.6% (by volume) with upward propagation of flame. The CO2 dilution effects on the flammability limits have been explored, the limits of flammability was narrowed by adding CO2 and propagation flame was reduced accordingly. The results indicated that to formulate an inflammable refrigerant mixture, using CO2, with substantial hydrocarbon content is not possible.
Abstract: Flame stability of gaseous fuel inside meso-scale combustor with double wire mesh was investigated experimentally. Combustor was made from quartz glass tube with an inner diameter of 3,5 mm and an outer diameter of 5 mm. Two pieces of wire meshes were made from stainless steel inserted at 10 and 13 mm from the end of combustor. Propane was used as fuel in this research. Flame was stabilized in the region between two wire meshes. The flame has a blue luminosity, indicate no soot formation condition. However, the second wire mesh and combustor wall has red luminousity at high velocity reactant, indicate that they have high temperature and emmited heat radiation. Meso-scale combustor with double wire mesh has broader flame stability area if compared to combustor with single wire mesh. Extention of this region occured toward lower equivalence ratio for lean fuel mixture, as well as toward higher equivalence ratio for rich fuel mixture. The most important extention region of flame stability area is toward higher reactant flow rate. It was caused by existing of second wire mesh which has function to prevent occurence of blow–off at relatively high reactant flow rate, as well as to increase heat recirculation to unburnt reactant as a results of higher wall temperature.
Abstract: Presented in this article are the results of theoretical research carried out with financial support from the Ministry of Education and Science of the Russian Federation (contract ID RFMEFI57914X0026) and demonstrating the need to consider the changes in ground heat transfer properties in geothermal borehole heat modeling, due to moisture condensation/evaporation in the ground pores. It is our opinion that in GSHP systems design, the quantity of the boreholes is often overestimated and the associated parameters oversized while the extent of the ground heat transfer is underestimated. In most cases, in designing GSHP operation and performance, this is due to the incorrect assessment of the ground moisture content, which has a most tangible effect on the ground heat transfer properties. This article demonstrates the need to consider the ground moisture condensation/evaporation in GSHP systems design. Presented in the article is the mathematical simulation of the ground pore moisture condensation at the GSHP boreholes. Also presented is numerical data derived from the calculations to assess the effect of the ground pore moisture condensation on the borehole heat transfer efficiency. Through analysis and experimentation, it was determined that the ground pore moisture condensation have a substantial impact on the GSHP efficiency.
Abstract: This paper contains the results of research, carried out with financial support from the Ministry of Education and Science of the Russian Federation (contract ID RFMEFI57914X0026). For the ground source heat pump (GSHP) used as a heating system in regions with cold climate the thermal effects of ground moisture freezing-melting processes can make an essential long-term impact on GSHP performance. However, widely known models of heat transfer inside and outside GSHP borehole do not take into account such effects. In this paper, we propose a method of engineering estimation of freezing-melting latent heat in the frame of modified cylindrical source model. The key feature of the method is the definition of effective thermal conductivity of ground to "convert" the latent heat of phase transition into equivalent heat flux from outer ground. The method is validated by laboratory measurements of ground thermal conductivity during the freezing-melting process.
Abstract: This paper contains the results of research dedicated to improving the energy efficiency of Moscow subway facilities and creation of stations with "zero" external sources heat consumption. The paper presents a method of simulation of the thermal conditions for subway tunnels, which allows overcoming the difficulties associated with the informative uncertainty of baseline data, as well as difficulties associated with the approximation of the external parameters, affecting the soil's thermal conditions. Advantage of this method in comparison with the traditional approach to the modeling of thermal processes in such systems is the fact that the usage of so-called "base" experimentally obtained information about the natural soil thermal conditions in this model, can partially take into account the whole range of factors (such as presence of the groundwater, it's speed and thermal conditions, the structure and location of the soil layers, the "thermal" background from the Earth, precipitation, phase transformation of moisture in the pore space, and more), which have significant influence on the formation of the thermal regime of the tunnel but are almost impossible to be taken into account within the strict formulation of the problem today. The method has been implemented in the software package INSOLAR.GSHP.12, created by JSC "INSOLAR-INVEST".
Abstract: This paper contains the results of research, carried out with financial support from the Ministry of Education and Science of the Russian Federation and dedicated to improving the energy efficiency of Moscow subway facilities and creation of stations with "zero" external sources heat consumption. This paper vindicates the possibility and economic feasibility of creating subway facilities with "zero" external sources heat consumption, equipped with heat pump systems for heating and cooling, which improve indoor climate comfort of subway's stations and halls. The research carried out by the authors proves the efficiency of using heat pump systems for heating and cooling in the Moscow subway. The proposed technology requires lower nonrecurrent capital investments than traditional technology, as well as enables to save up to 80 % of energy. Considering the current prices for connecting to the centralized heating systems, the technology in question pays back at the stage of construction. The possibility of stabilizing thermal conditions at stations and in halls of the subway is an important advantage of this technology. Tis paper proposes schemes of heat pump equipment usage that allows reversing it for operation in cooling mode, which provide sufficient air conditioning and humidity control at stations, halls and service rooms. The authors evaluate the heat emission of passengers, that is removed with the exhaust air, to be about 0.15-0.17 billion kW*h annually. Thus the Moscow subway just dumps outside about 2.4 billion kW*h of thermal energy, including heat emitted by passengers, annually. If recycled this amount of energy is sufficient to cover all subway's requirements for thermal energy.
Abstract: To deal with the lack of accurate and efficient inspection methods in complex free-form surfaces, three-dimensional measurement method based on the optical measurement and computer image processing technology was proposed. It adopted laser scanning technology to get point clouds of free-form surface. Used rapid measurement software to inspect precision of point cloud& CAD model. What could be the cause of machining errors was analyzed. 3D deviation inspection of complex surfaces was applied by an artifact. Detected the machining error of an important section, and outputted test report. This research provides a convenient and swift method for the inspection of free-form surface and processing quality control.
Abstract: Magnetoelectric seismometer has many outstanding features, such as low cost, small size, light weight, high sensitivity, low noise, good high frequency response, and reliable operation, simple set up, so these type of seismometer is widely used in several areas. However, because the structure of magnetoelectric seismometer (inertial mass and elastic support module), there has the material and mechanical structure limitation, so the inherent frequency is around between 5 to 30Hz, hard to be lower, hence, the low frequency characteristic is poor. To extend the seismometer's range of application, post compensation is needed. The researchers from both home and aboard proposed many different method to deal with the low frequency response of this seismometer, such as “inverse filter” method, “Lippmann” method, which uses negative resistance and feedback coil. These methods have got some results separately. In this paper, we will propose a low frequency integral method to extend the seismometer's frequency response. It is accomplished through balanced integration and high precision chips to suppress the circuit drifting and noise interference. The results from vibration table shows, after integration, the seismometer's low frequency corner frequency is extended from 2 Hz to under 0.1 Hz, the sensitivity is enhanced from 200V/m·s-1 to 400V/m·s-1.
Abstract: In this study an inertial measurement unit (IMU) used in unmanned underwater vehicles has been taken into consideration.The main objective of this study is to improvethe measurements obtained from an IMU used in the position detection by minimizing the effect of its static and dynamic errors on the output. To enhance the IMU data optical computer mouse (OCM) is proposed as calibrator. The data received from the OCM is used to train an artificial neural network (ANN) which would improve the IMU outputs by trying to estimate the reference data from the actual sensor outputs. The ANN performance is compared with that of classic low pass filtering methods to provide a relative performance criterion. The ANN trained with OCM data has given satisfactory results. During the training of ANNs the effects of several parameters such as neural network architecture, activation functions, training algorithm, layer and cell number have been investigated. Thus, the results, findings and insights obtained in this study can be applied in research areas where this kind of nonlinear estimators are used.