Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2024-03-26
Abstract: In this short letter, we report an experimental investigation on the integration of film cooling for thermal protection in a 72-mm cylindrical rotating detonation engine (RDE). The cooling scheme involves injection of cooling air through a series of cat-ear-shaped film cooling holes densely distributed along the outer wall of the cylindrical combustor. Our findings reveal the successful initiation of the RDE and sustained propagation of the rotating detonation wave (RDW) when film cooling is activated and the outflow reaches a supersonic state. Experimental observations corroborate the numerical simulations, indicating a lateral expansion tendency of the cooling jet under the influence of the high-frequency RDW.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2024-01-06
Abstract: With the continuous progress of industrial technology, deep learning, as an important branch of artificial intelligence, has brought new possibilities to various fields. In this paper, the optimal location of diesel engine vibration monitoring is studied, focusing on the problem of data overlap and mutual interference in vibration monitoring. By discussing the best position and number of sensors on diesel engine, a method of sensor layout optimization based on graph pool neural network is proposed. In this method, the sensor points are regarded as the nodes of the graph, and the adjacency matrix is processed by the convolution layer of the graph, and the eigenvector of each node is obtained. The feature vectors are screened and sorted by information entropy and independence methods, and the representative feature vectors are selected as important nodes. Finally, classification and screening are carried out in the pooling layer, taking into account factors such as coverage and cost, so as to determine the optimal sensor placement and number.
The experimental results show that the proposed graph pool network model can effectively optimize the layout of sensor measuring points, and has high accuracy and stability. This method is not only suitable for diesel engine vibration monitoring, but also can be extended to other problems requiring sensor layout optimization.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2024-01-06
Abstract: With the promotion of "Industry 4.0" and "Intelligent Manufacturing 2025", intelligent equipment is becoming the future development direction of high-end equipment. In this process, the fault diagnosis and identification system, as an important research field, can suppress the unbalanced vibration of machinery in real time, so as to realize the autonomous health of equipment. Such a system can not only improve the operational efficiency and productivity of the equipment, but also reduce the cost and risk of equipment maintenance. Therefore, the research and development of such systems is of great significance to promote the development of intelligent manufacturing and high-end equipment manufacturing.
Condition monitoring and fault diagnosis of large rotating machinery is a necessary means for the production management of modern enterprises, through scientific monitoring and diagnosis, the efficient, safe and reliable operation of the equipment can be realized, and the sustainable development of the enterprise can be provided with a strong guarantee. This project takes the typical vibration faults of the rotor system of rotating machinery as the main body of research, considers the analysis of them, and establishes an intelligent identification system for the diagnosis of typical faults of the rotor system of rotating machinery. The main research contents and conclusions of this paper are as follows:
(1) This paper summarizes and explores the current mechanical intelligent fault diagnosis algorithm and the research method of using neural network for fault classification by consulting relevant literature, and finally decides to choose RBF neural network for fault diagnosis and classification.
(2) PCA dimensionality reduction technology is used to reduce the dimension of the data after extracting features, so as to reduce the dimension of the data to solve the problem of "dimensionality disaster" and make the data more reliable;
(3) The fault classification software is established by using the radial basis neural network in the artificial neural network, and the fault is identified by the classifier and verified by relevant experiments to complete the classification software design;
(4) A test bench was set up to collect data for relevant experimental verification, and the experiment showed that the diagnostic accuracy reached more than 85%.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2024-01-05
Abstract: Many key equipment rely heavily on the high-powered medium to high speed diesel engine, which has a broad range of applications in areas such as ships and nuclear power. Due to the complex mechanical structure and ever-changing working environment, diesel engine equipment accidents occur frequently, and mechanical failures and equipment damage are becoming increasingly prominent. Frequent failures have become a major challenge for the operation of these equipment. The occurrence of malignant faults in diesel engines often leads to serious economic losses and casualties. Therefore, using reasonable methods to obtain fault characteristics, researching fault detection and early diagnosis methods for diesel engines, achieving early warning and timely diagnosis of diesel engine faults, plays an important role and value in improving the stability of high-power, medium and high-speed diesel engine operation, equipment safety, and enterprise economy.
This article extracts 22 vibration characteristics of diesel engines in the angular domain, time domain, and frequency domain to form a feature set. In response to the diverse and complex operating conditions of diesel engines, with only a small number of operating samples, this article uses neural networks to map the relationship between operating conditions and key parameters in the Markov space, and constructs a healthy baseline for diesel engines under variable operating conditions.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Electrical Engineering Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2022-04-10
Abstract:
Exergy is an index to measure energy quality, which reveals the essence of work capacity loss in the process of energy transfer. In order to study the dynamic evolution mechanism of exergy in time-varying energy networks, the constitutive relations between physical quantities in energy networks are listed based on the energy network theory, and the generalized expressions of exergy are given, including the generalized description and loss equation of exergy based on the second law of thermodynamics, and the energy level factor is introduced to evaluate the energy quality. The dynamic evolution process of different forms of exergy in the energy transfer tube (line) is analyzed, including electric exergy, thermal exergy and pressure exergy, and the output equation and efficiency calculation method of exergy are given. The dynamic evolution process of exergy in energy conversion equipment is analyzed, and the loss, storage and efficiency of exergy are calculated. Finally, the dynamic evolution process of exergy in an integrated energy system is simulated by a specific example. The study of this paper can fully tap the energy efficiency potential of the integrated energy system, and lay a solid theoretical foundation for better realization of energy cascade utilization.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: For the temperature measurement of high- temperature furnaces with window glass. how to overcome the effects of the window glass has been a problem. This paper describes a method of using the a same window glass, 2 times (referred to as ) measurement method, in order to achieve the impact of the elimination of window glass. By theoretical analysis, numerical simulation, experimental verification shows that the method is feasible. By radiation temperature calibration of a high-temperature blackbody and of a high-temperature radiation thermometer, these application examples to prove that radiation thermometry method overcoming the window glass is a scientific, rational, simple, convenient and practical. For radiation temperature measurement of the furnaces with window glass , high-temperature radiation thermometer value transfer and other applications, is instructive.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: Three vaned diffusers for a high-pressure-ratio centrifugal compressor are designed, and the effects of inlet blade angle and blade profile of diffuser on the stage performance are investigated by the experiment and numerical simulations. The results show that, the decrease of inlet blade angle makes the performance curve move towards the low flow rate side, and the little drops of the peak stage efficiency and pressure ratio can be detected. The low-solidity airfoil diffuser can enlarge the operating range of stage, but decreases the stage efficiency and pressure ratio remarkably. The further flow analysis show that, decreasing the inlet blade angle leads to the spread of flow separation zone, the blockage of flow channels and the increase of losses. The large-scale flow separation is more likely to generate when the low-solidity airfoil diffuser is adopted.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: For a complex system, the reciprocal function of the particles constituting the system decides its energy state. Schr鰀inger equation which describes the particles moving rule will vary in different potential field. In this paper, based on the mathematic model in Hamilton harmonic oscillator researched before, Morse potential energy function which replace the harmonic oscillator potential model is introduced to study sound propagation in the one-dimensional gas molecule chain. From the standpoint of energy, the problem about sound propagation is converted into the problem of the harmonic wavelet function and the energy Eigen values. The relationship between the partition function and the thermodynamics quantity is built and sound propagation model based on oscillator model of Morse potential energy functions is used to get sound pressure and sound energy. Finally the one-dimensional sound pressure results got by quantum oscillator model agree well with classical approach results.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: This paper presents a flow control method using micro-cylinder installed in front of the blade leading edge and invests the aerodynamic performance of the VAWT equipped with micro-cylinders. Numerical results suggest that the flow separation is effectively controlled by setting a micro-cylinder in front of the blade leading edge when the blade works at large attack angle. Meanwhile, the VAWT equipped with micro-cylinders has higher efficiency than regular VAWT under small tip speed ratio.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: Full cavitation model、mixture and standardκ-εmodel were used to investigate cavitation flow in a centrifugal pump with slope volute. Performance of model pump at cavitation and non-cavitation conditions were obtained, and cavitation bubbles distribution in blade surface and channel were discussed. The results show that: at high flow rate, cavitation easily occurs in model pump. When static pressure at pump inlet decreases, cavitation bubbles firstly appear in suction pressure side of blade inlet. With pressure reducing further, cavitation region expands to impeller outlet, and head of model pump is affected obviously. Then cavitation regions transforms to blade pressure side, and the whole impeller channel are filled with cavitation bubbles leading to pump performance dropping rapidly. At full cavitation condition, steady operating status of model pump is destroyed. Under different NPSH working conditions, pressure amplitude at blade passing frequency differs, and pressure amplitude almost reaches minimum value at critical NPSH.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: For the characteristics of one-target focus type of the heliostats in the tower solar power system, the distribution of the heat flux of the solar cavity receiver is non-uniform and concentrated on the certain heat panels of the cavity receiver, which causes the deterioration of the flow rate distribution, thermal deviation and the flow reliability, and also affects the stability and security of the whole system. Thus, based on the study under one-target focus type of the heliostats, the flow rate distribution, thermal deviation and the flow reliability under the multi-target focus type of the heliostats field is developed to provide general guidance for the security operating and the optimal control strategy of the hydrodynamic characteristics of the solar power tower system.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: A series of catalysts supported on Al2O3 with different loadings of metals were studied for the low-temperature selective catalytic reduction (SCR) of NO with ammonia. Effects of amounts of metal oxides, the concentration of O2, calcined temperature and GHSV on NO conversions were investigated. The results show that the catalyst 8Fe-2Ce/Al2O3 yield nearly 94% NO conversion at 240℃, better than 8Fe/Al2O3. In addition, the loading of Ce promotes not only the low temperature catalytic activities but also good resistance to SO2. Catalysts made via deposition are better than via impregnation, and the calcined temperature of catalyst at 450℃ is better than 550℃. Both the concentration of O2 and GHSV have considerable influences on the catalytic activity。
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: Severe slugging is undesired in offshore pipeline-riser system and riser topside choking is an effective method for the elimination of severe slugging. Flow patterns and transitions induced by riser topside choking on severe slugging were studied experimentally. It is found that the pressure drop across the choke increases with the decrease of the valve opening. The pressure of the gas trapped in the pipeline is counteracted and therefore the expansion of the gas is suppressed. As a result, the gas penetrates into the riser in the form of individual bubbles, leading to the formation of slug flow and bubbly flow. The stability boundary accounting for the prediction of the behavior of gas-liquid flow in a pipeline-riser system in the process of riser topside choking is also proposed. The predictions are tested against experimental results, showing a reasonable agreement.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: The available experimental data of heat transfer for water and the empirical correlations which are used to predict heat transfer at supercritical pressure in vertical upward tubes are extensively collected. The calculated values of these experimental correlations are compared with the experimental value of the heat transfer deterioration, errors and accuracy analyses for these correlations arrived are presented. The heat transfer experimental data in vertical upwards tubes are fitted to get a new heat transfer correlation. An error analysis for the new correlation is presented which works well with heat transfer deterioration.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: The experiment was made of boiling heat transfer of FC-72 on micro-pin-finned chips with submerged jet impingement. The experimental conditions cover two different liquid subcoolings (25, 35 K), three different jet velocities (Vj = 0.5, 1.0, 1.5 m/s) in the direction perpendicular to chip surface. The dimension of the silicon chips is 10 mm × 10 mm × 0.5 mm (length × width × thickness) on which micro-pin-fins with the two dimensions of 50 × 50 × 60 μm3 (width × thickness × height, named PF50-60) and 50 × 50 × 120 μm3 (named PF50-120) were fabricated using the dry etching technique. For micro-pin-fins, the critical heat flux qCHF increases with jet velocity and liquid subcooling. Increasing liquid subcooling and jet velocity can decrease the size of bubbles’ separation, increase the detachment frequency and thus decrease the wall superheat and increase the critical heat flux. The heat transfer process is dominated by the forced convection in single-phase heat transfer region, and the heat flux increases linearly with increasing wall superheat. In the nucleate boiling region, the heat transfer is affected by both the forced convection and nucleate boiling heat transfer. The slope of nucleate boiling curve is larger than that in single-phase region when the jet velocity is small, indicating better heat transfer performance of boiling.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: Bubble plate heat exchanger is a new type heat exchanger. The influence of the plate geometric parameters on the flow and heat transfer is unclear so far. Based on the principle of multi-field synergy, the influence of the plate geometric parameters on the flow and heat transfer is studied numerically. It is find that when the unit length increases or the width decreases, the friction factor f decreases, performance evaluation parameters PEC increases; when the inclination angle of the unit body relative to the main flow direction is 90 � the factor f obtain the minimum value, PEC obtain the maximum value. The results can be applied to the optimization of the bubble plate heat transfer element and the plate design.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: A novel counterflow flame apparatus that can meet the requirement of heterogeneous combustion of pulverized coal particles was developed. A new micro-scale powder feeding system was developed based on the fundamental of deagglomeration by particle-wall impaction, achieving a perfect dispersion and stable feeding rate of coal particles in low carrier flows. With the advanced ICCD optical technology, the behavior of coal particles across the counterflow flame was observed. Results show that the particle heat rate can reach as high as 105 K/s, while flame temperature and particle residence time are the dominant factors that influence the ignition mechanism in the post-flame zone.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: Alkali metal chloride vapor released from biomass combustion will condense on the heating surface, and react with gases like SO2, H2O, and O2 in the flue gas, which can relieve the corrosion of alkali metal on the heating surface. Aiming at the heterogeneous sulfation of KCl, fixed bed is used to investigate the influence of sulfation temperature, residence time and the concentration of SO2, O2, H2O on the sulfation of KCl. Results show that the sulfation rate of KCl increases with the concentration of SO2, O2, and H2O. And it increases linearly with residence time, and increases exponentially with sulfation temperature.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: Hydrocarbons in coal pyrolysis gas can interferes the continuous mercury analyzer. A pretreatment method with high temperature oxygen carrier was proposed to eliminate the interference. The results showed that hydrocarbons have a big impact on continuous mercury analyzer. After being treated by the high temperature oxygen carrier, the mercury concentration in coal pyrolysis gas can be accurately continuous measured. The XRD analysis of oxygen carrier also verified this result.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: Development of sodium-based solid sorbents for decreasing CO2 emission from coal-fired power plants is receiving爉ore燼nd more燼ttention. Its carbonation behaviors have been studied recently, and it is understood that its primary downfall is the slow reaction with CO2 during adsorption process. TiO2 is examined as a potential dopant for sodium-based solid sorbent based CO2 capture process in a bubbling fluidized-bed. SEM, XRD and Nitrogen Adsorption characterizations of Na2CO3/Al2O3 doped with TiO2 indicate that TiO2 is stable within the temperature range necessary for such a process. More importantly, TiO2 has a positive effect on the carbonation of Na2CO3 and the reaction rate, as well as the CO2 uptake, is observed to increase obviously. Carbonate reaction products are NaHCO3 and Na5H3(CO3)4. TiO2 has little effect on the regeneration of sorbent.Despite this, the loading of TiO2 should be limited, because too much TiO2 doped may block the microstructure of sorbent which is unfavourable to carbonate reaction.