Search

Abstract In this paper, a novel Multi-loop Moving Coil Linear Compressor (M-MC-LC) is studied, in which the piston is driven by the Co-core Bilateral Reverse Coil (CBRC) in a reciprocating motion within the magnetic array. The DC excitation technique is introduced to address the phenomenon that the piston is axially offset under the influence of gas force. In order to clarify the effect of DC excitation on the performance of the moving-coil linear compressor, the compressor prototype is developed, and the dynamic performance testing test-bed and the refrigeration performance test-bed are built to qualitatively and quantitatively analyze the relevant performance parameters of the compressor from theoretical and experimental aspects. The results show that when the DC excitation accounts for less than 20% of the total input voltage, the pressure ratio increases with the increase of DC excitation; when the percentage is at 22.9%, a sudden drop in the volumetric efficiency of compressor occurs. Mass flow and COP increases first and then decreases with the increase of DC voltage excitation. The study results provide a guideline for the stable and reliable operation of the system and provide a valuable reference for the linear compressor piston offset adjustment.

This study presents a thermo-economic assessment of three low-global-warming-potential (GWP) substitutes, R1233zd(E), R1234ze(Z) and R1234ze(E), for R245fa used in organic Rankine cycle (ORC) systems, considering two models with different heat sources. The exhaust heat from a diesel generator is served as heat source of Model I, while the waste heat of exhaust and jacket cooling water are used as heat source of Model II. It is noted that the working pressure of R1234ze(E) is much higher than that of R1233zd(E), R1234ze(Z) and R245fa in a fixed evaporation-temperature range. Furthermore, the system using R1234ze(E) has the minimum net power output for Model I, while it turns into the maximum net power output for Model II. In addition, both R1234ze(Z) and R1233zd(E) can be used as good alternative working fluids for R245fa because R1234ze(Z), R1233zd(E) and R245fa have close working pressures, maximum net power outputs, and minimum levelized energy costs. Compared to Model I, LECmin of R1233ed(E) and R1234ze(Z) are reduced by 10.8 % and 9.9 % and PBmin of R1233ed(E) and R1234ze(Z) are reduced by 11.5 % and 10.1 %, respectively, in Model II. However, R1233zd(E) has the highest minimum payback period for both Model I and Model II among the four working fluids investigated.

Due to the increasing demand for low carbon fuels, ammonia is considered a viable option. Considering the problems associated with the combustion of ammonia, such as its narrow flammability range, it has been suggested to use it together with other fuels, such as methane. Following previous studies, which mainly focus on the emission of this fuel mixture in burners and simplified chambers, this research attempts to conduct an experimental and numerical study with a greater emphasis on performance parameters and pollution in an actual microturbine combustion chamber. The study investigates the effect of a mixture of ammonia with methane and its fraction on the combustion performance of the combustor and its emissions (NOx, CO) in two different thermal powers. The results showed that flame temperature decreased as the fraction of ammonia in the fuel increased, and the flame moves away from the injector. It also appeared that adding ammonia to the fuel increased the amount of NOx produced in the combustor without reducing CO significantly. Also, the combustor outlet temperature remained almost unchanged, but the combustion efficiency of the combustor decreased as the ammonia fraction increased. • Investigated performance and emissions of microturbine combustor with ammonia/methane fuel mixture. • Stable combustion achieved up to 50% mixing ratio, without altering combustor configuration. • Lowering reaction rate delays ignition and hampers chamber performance. • Ammonia in methane reaction reduces complete combustion, causing elevated CO and NOx emissions. • Higher ammonia ratio reduces combustor efficiency, raises pattern factor, with constant output temperature. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present paper presents a multilayer hybrid model for sensorless measurement of pump operating status, with the objective of enabling safe and stable operations while reducing energy losses. The model takes easily measurable variables such as rotational frequency and valve opening as input features to predict the performance parameters of the centrifugal pump. By integrating just-in-time learning (JITL) with Gaussian process regression (GPR) and leveraging the unique probability features of GPR, a just-in-time-learning GPR (JGPR) is developed to extract valuable feature information. The JGPR sequentially predicts the flow rate, coefficient for dynamic head, and shaft power. The predicted values are extended to other input features, which can accurately capture the characteristics of the centrifugal pump and effectively replace the process of acquiring process parameters through sensors. Finally, the mechanism model is integrated into the multilayer JGPR model to calculate the performance parameters of centrifugal pump. The validation results indicate a strong agreement between predicted and experimental results, with predicted meeting performance parameters all engineering requirements. Compared to a single model, the multilayer hybrid model significantly improves the reliability of predictions, demonstrating the feasibility of using this approach to predict performance parameters. This research provides valuable insights into the measurement of sensorless pump operating states, enabling safe and efficient operation in complex conditions. [ABSTRACT FROM AUTHOR]

The increasing spread of ragworts is observed with concern. Ragworts like tansy ragwort (Jacobaea vulgaris Gaertn.) or marsh ragwort (J. aquatica) contain pyrrolizidine alkaloids (PA) which may induce hepatotoxic effects. Grazing animals usually avoid ragworts if their pasture management is appropriate. Preserved feed prepared from ragworts contaminated meadows may, however, lead to a significant exposure to PA. Previous studies on toxicity of PA for dairy cows revealed inconsistent results due to feeding ragwort plant material which was associated with heterogeneous PA exposure and thus failed to conclusively deduce critical PA doses. Therefore, the aim of the present study was to expose dairy cows (n = 4 per group) in a short-term scenario for 28 days with increasing PA doses (PA1: 0.47 mg PA/kg body weight (BW)/day (d); PA2: 0.95 mg PA/kg BW/d; PA3: 1.91 mg PA/kg BW/d) via oral administration by gavage of a defined PA-extract. While group PA3 was dosed with the PA-extract alone, groups PA2 and PA1 received PA-extracts blended in similar volumes with molasses to provide comparable amounts of sugar. Additionally, two control groups were treated either with water (CONWater) or with molasses (CONMolasses) to assess the effects of sugar without PA interference. While clinical traits including dry matter intake, milking performance, rectal body temperature, ruminal activity and body condition score (BCS) were not influenced by PA exposure, activities of enzymes indicative for liver damages, such as gamma-glutamyltransferase (GGT), aspartate aminotransferase (AST) and glutamate dehydrogenase (GLDH), increased significantly over time at an exposure of 1.91 mg total PA/kg BW/d. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present work has discussed the following characteristics like performance, combustion and emission characteristics of blends of aluminum (Al), zinc oxide (ZnO) and its mixture of nanoparticles at different ratios with diesel tested on a stationary direct injection compression ignition (CI) engine at five different loads. The fuels have been made by blending of nanoparticles with diesel at different concentrations. The results have shown that the Nano fuels have given lower brake specific fuel consumption (BSFC), higher brake thermal efficiency (BTE) and air-fuel ratio when compared with diesel. In combustion analysis, the Nano fuels have given higher heat release rate, crank angle 50 (CA50) and lower ignition delay when compared with diesel. In emission analysis, the Nano fuels have given higher nitrogen oxides (NO x ) and lower carbon monoxide (CO), hydrocarbons (HC) and smoke emissions when compared with diesel. The fuel properties of nano fuels have shown that the kinematic viscosity, calorific values have been higher and flash point, fire point, density have been lower when compared with diesel.

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The key performance parameters of spinning frame are difficult to be indentified and the performance degradation model is difficult to be established. To solve the problem, a reliability evaluation method for multiple performance degradation process of spinning frame is proposed. The relationship between the performance parameters of the spinning frame was analyzed, and the subjective and objective comprehensive weight identification method was used to screen the monitored performance parameters. The parameters with comprehensive weight greater than 0.5 were selected as the characterization parameters of the performance degradation of the spinning frame. The Wiener process was used to fit the multiple parameter degradation failure track. The Copula function was used to analyze the correlation of multiple parameter degradation failure process, and the Gibbs algorithm was used to estimate the parameters. The application results show that the proposed reliability evaluation method is in line with the actual production, and has high accuracy, which is helpful to improve the reliability level of spinning frame performance.

There are various static var compensator configurations are available and listed in the literature. Their performances are evaluated based on their voltage support, dynamic response, losses, cost, and additional filter requirement, if any. In this paper, efforts are made to improve the dynamic performance parameter such as rise time, settling time, and peak overshoots. A new topology with an adaptive controller is presented, in which capacitor and reactor banks are divided in their binary values and connected in the shunt. Capacitor and reactor banks are operated by thyristorised switches. Both these banks are operated in closed-loop form as a cascade control. Amongst these, capacitor bank operates as coarse control, and reactor bank acts as fine control. For the performance enhancement, a model reference adaptive controller is used. The system identification toolbox is used to evaluate the mathematical model of the plant with Matlab. The model's performance was analyzed deeply by the adaptive controller with different reference models such as critical, under, and overdamped. The performance parameters such as rise time, settling time, and peak overshoot in the form of reactive power swings, are evaluated and plotted for different adaptive gains using MIT rules. Abbreviations: $ {\textrm{m}_\textrm{p}} $ : Peak overshoot; $ {\textrm{Q}_\textrm{C}} $ : Reactive power of capacitor; $ {\textrm{Q}_\textrm{L}} $ : Reactive power of inductor; $ {\textrm{Q}_{\textrm{TBSC}}} $ : Reactive power of TBSC bank; $ {\textrm{Q}_{\textrm{TBSR}}} $ : Reactive power of TBSR bank; $ {\textrm{t}_\textrm{r}} $ : Rise time; $ {\textrm{t}_\textrm{s}} $ : Settling time; e: Error; Gc(s): Transfer function of TBSC plant; Gl(s): Transfer function of Disturbance plant; Gr(s): Transfer function of TBSR plant; SVC: Static VAR Compensator; t:time; TBSC: Thyristor binary switched capacitor; TBSR: Thyristor binary switched reactor; TSC: Thyristor switched capacitor; TSR: Thyristor switched reactor; u(t): System input; v(t): System disturbance; y(t): System output; Ym: Reference model output; Yp: Plant output; γ: Adaptive gain; θ: Theta

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To meet increasingly stringent emission regulations, diesel engines must be equipped with DOC, DPF and SCR. Five performance parameters including system back pressure, HC conversion efficiency, conversion efficiency of NO to NO2, passive regeneration rate, and conversion efficiency of NO to N2 are very important for DOC+DPF+SCR system. Nine structural parameters including rDOC, rDPF, rSCR, σDOC, σDPF, σSCR, δDOC, δDPF, and δSCR directly affect the five performance parameters, this paper has carried out a detailed study on it. First, a simulation model of DOC+DPF+SCR system was established, and calibrated by experiment. Then, simulation was performed on the five performance parameters under different values of the nine structural parameters. Subsequently, a novel model using random forest algorithm was established to analyze the correlation between the performance parameters and the structural parameters. The results show that σDPF has the greatest influence on system backpressure, followed by rDPF. The rDOC has the greatest influence on HC conversion, followed by σDOC. The rDOC has the greatest influence on conversion of NO to NO2, followed by σDOC. The rDPF has the greatest influence on DPF passive regeneration rate, followed by rDOC. The rSCR has the greatest influence on conversion of NO to N2, followed by rDOC. [ABSTRACT FROM AUTHOR]

The present work has discussed the following characteristics like performance, combustion and emission characteristics of blends of aluminum (Al), zinc oxide (ZnO) and its mixture of nanoparticles at different ratios with diesel tested on a stationary direct injection compression ignition (CI) engine at five different loads. The fuels have been made by blending of nanoparticles with diesel at different concentrations. The results have shown that the Nano fuels have given lower brake specific fuel consumption (BSFC), higher brake thermal efficiency (BTE) and air-fuel ratio when compared with diesel. In combustion analysis, the Nano fuels have given higher heat release rate, crank angle 50 (CA50) and lower ignition delay when compared with diesel. In emission analysis, the Nano fuels have given higher nitrogen oxides (NOx) and lower carbon monoxide (CO), hydrocarbons (HC) and smoke emissions when compared with diesel. The fuel properties of nano fuels have shown that the kinematic viscosity, calorific values have been higher and flash point, fire point, density have been lower when compared with diesel. [ABSTRACT FROM AUTHOR]

This paper designs a new internal meshing twin-screw pump (new twin-screw pump). To study the new twin-screw pump in the principle, performance parameters, and contact characteristics of the differences with the single-screw pump, the mathematical method of motion conversion is used to convert the planetary motion of the single-screw pump into the fixed-axis rotation of the internally intermeshing twin-screw pump. It is found that the movement relationship of the two pumps is similar. When the structural parameters of the two pumps are the same, the flow per revolution of the single-screw pump is N +1 times that of the new twin-screw pump. To obtain the force transmission characteristics in the internal meshing process, a numerical method was used to analyze the structure of the new twin-screw pump statically. Due to the existence of the meshing relationship, the influence of the screw meshing fit clearance, progression, and pitch on the contact stress is further explored. The results of the study show that the internal and external rotor contact stresses show a trend of small in the middle and large at the ends, the stress distribution coefficient ξ increases with the increase of the mating clearance, and the stress distribution becomes uneven with the increase of the number of screw stages and pitch. The results of this study provide a basis for the reasonable selection of structural parameters of the new twin-screw pump. [ABSTRACT FROM AUTHOR]

Expertise and intuition of chip design engineers supplemented by a unique design objective governs the choice of routing algorithm in Network-on-Chip(NoC) based systems. However, the same choices when considered for more than one performance parameter of the network, do not yield expected results since different applications exhibit different network performances for the same routing technique. Thus, we advocate use of an application pattern driven routing approach instead of the usual static routing strategies. In this paper, we propose an application pattern driven dynamic routing approach for NoC based systems while committed to optimize desired performance parameters. Our proposed methodology serves a dual purpose of improving the network performance of the NoC based system as well as relieving the design engineers from making the complex and tedious routing decisions. A machine learning based predictive approach is employed in our approach to classifying traffic patterns and it achieves 94.78 % accuracy while our overall proposed methodology achieves significant improvement in power consumption and throughput as compared to state of art works available in literature. • Every application traffic has a distinct effect on the performance parameters of the Network-on-Chip. • Two different applications may not exhibit equal performance while targeting a specific objective for the same routing algorithm in a NoC. • It is essential to consider an application driven dynamic routing scheme for NoC architectures instead of a predetermined routing policy. Further, the routing architecture should be orchestrated to support the dynamic routing scheme. • Methodology Adopted: • Evaluation of NoC performance measures for different routing algorithms - Traffic profiling. • Determination of the most optimal routing strategy for a given application - Application Route Mapping. • Proposal for implementation of dynamic routing - Reconfigurable routing table. • Proposal to classify unknown application traffic and predict the most optimal routing algorithm for it. • ML based Route prediction for unknown traffic [ABSTRACT FROM AUTHOR]

There are various static var compensator configurations are available and listed in the literature. Their performances are evaluated based on their voltage support, dynamic response, losses, cost, and additional filter requirement, if any. In this paper, efforts are made to improve the dynamic performance parameter such as rise time, settling time, and peak overshoots. A new topology with an adaptive controller is presented, in which capacitor and reactor banks are divided in their binary values and connected in the shunt. Capacitor and reactor banks are operated by thyristorised switches. Both these banks are operated in closed-loop form as a cascade control. Amongst these, capacitor bank operates as coarse control, and reactor bank acts as fine control. For the performance enhancement, a model reference adaptive controller is used. The system identification toolbox is used to evaluate the mathematical model of the plant with Matlab. The model's performance was analyzed deeply by the adaptive controller with different reference models such as critical, under, and overdamped. The performance parameters such as rise time, settling time, and peak overshoot in the form of reactive power swings, are evaluated and plotted for different adaptive gains using MIT rules. Abbreviations: m p : Peak overshoot; Q C : Reactive power of capacitor; Q L : Reactive power of inductor; Q TBSC : Reactive power of TBSC bank; Q TBSR : Reactive power of TBSR bank; t r : Rise time; t s : Settling time; e: Error; Gc(s): Transfer function of TBSC plant; Gl(s): Transfer function of Disturbance plant; Gr(s): Transfer function of TBSR plant; SVC: Static VAR Compensator; t:time; TBSC: Thyristor binary switched capacitor; TBSR: Thyristor binary switched reactor; TSC: Thyristor switched capacitor; TSR: Thyristor switched reactor; u(t): System input; v(t): System disturbance; y(t): System output; Ym: Reference model output; Yp: Plant output; γ: Adaptive gain; θ: Theta [ABSTRACT FROM AUTHOR]

The key performance parameters of spinning frame are difficult to be indentified and the performance degradation model is difficult to be established. To solve the problem, a reliability evaluation method for multiple performance degradation process of spinning frame is proposed. The relationship between the performance parameters of the spinning frame was analyzed, and the subjective and objective comprehensive weight identification method was used to screen the monitored performance parameters. The parameters with comprehensive weight greater than 0.5 were selected as the characterization parameters of the performance degradation of the spinning frame. The Wiener process was used to fit the multiple parameter degradation failure track. The Copula function was used to analyze the correlation of multiple parameter degradation failure process, and the Gibbs algorithm was used to estimate the parameters. The application results show that the proposed reliability evaluation method is in line with the actual production, and has high accuracy, which is helpful to improve the reliability level of spinning frame performance. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In Northwest China, wind resources are especially abundant, but this area is also seriously affected by sandy environments, so any wind turbines in this area are definitely affected by the sand‐wind flow. Therefore, the shear stress transport k‐ω turbulence model and discrete phase model are both used for the simulation of an S809 airfoil to study the influence of sandy environments on the aerodynamic performance. Based on this, the modified blade element momentum theory will be used to design wind turbines that can operate in both clean air and sandy environments and study the influence of sandy environments on wind turbine performance. The results show that the influence of the sand‐wind environment on the aerodynamic performance of the airfoil is as follows. In the particle diameter range of 5 to 30 μm, as the particle diameter increases, the lift coefficient decreases, and the drag coefficient increases. However, in the particle diameter range of 30 to 100 μm, the change is just the opposite. At the same time, as the increase of particle mass concentration, the lift coefficient of the airfoil decreases, and the drag coefficient significantly increases. Also with the increase of equivalent density, the change is just the opposite. Moreover, the influence of sandy environments on the performance of wind turbines is found to be as follows. At low wind speeds, the power output of the sandy turbine is greater than that of the clean turbine when they run in a sandy environment. Also, it is found that whether wind turbines run at high or low wind speeds, the thrust of sandy turbine is less than that of clean turbine when they run in sandy environments. [ABSTRACT FROM AUTHOR]

Numerical analysis plays vital role in designing gas turbine combustors for improving its performance. It requires deep understanding of turbulent and multiphase reactive flow physics inside the combustor. Hence present work focusses on numerical investigation of turbulent flow and reactive interaction between liquid spray of aviation kerosene droplets and air for the experimentally investigated combustor configuration. The present analysis results agree well with the experimental test results. Mixture fraction based Probability Density Function flamelet combustion model is used to solve transport equations by generating the flamelet library for Jet-A fuel. The analysis provides good insight into the multiphase combustion process and the flow phenomena occurring inside the combustor. Further, combustion performance characteristics at different design point operations are investigated in the present work keeping the air fuel ratio constant. Results show rise in peak velocity by 2.5 times and pressure loss factor by 6 for design point operating at higher flow rates in comparison with the baseline design operating point.

Brines (ethylene glycol, calcium chloride, propylene glycol and potassium acetate)-based hybrid (combinations of alumina, copper oxide, silica and titania with copper nanoparticles) nanofluids have been used as a secondary refrigerant to improve the heat transfer characteristics of the plate evaporator for milk chilling. Effect of nanoparticle combination, shape and size on heat transfer area, pump work, the ratio of heat transfer coefficient to pressure drop, coefficient of performance, performance index, thermal performance factor and exergetic efficiency has been examined theoretically. Copper oxide–copper hybrid nanofluid gives superior performance, while silica–copper hybrid nanofluid performs well in terms of exergetic efficiency. The maximum decrease in effective heat transfer area (5.9%) is found for propylene glycol brine-based copper oxide hybrid nanofluid. Percentage change in heat transfer area and performance index reduces with an increase in the particle size and is maximum for alumina–copper hybrid nanofluid. However, thermal performance factor increases with particle size. Brick-shaped particles show maximum changes in heat transfer area and performance index, while platelet-shaped particles show worse performance. The study reveals that the nanoparticle shape has a strong influence on the plate heat exchanger performance due to a significant deviation in surface area-to-volume ratio. [ABSTRACT FROM AUTHOR]

Combined heat and power systems are becoming more and more important, regarding their enhanced efficiency, energy saving, and environmental aspects. In the peresent study, three configurations of combined heat and power systems are intended as an alternative to separate production plant by considering environmental aspects. First and second laws of thermodynamics are adapted to the operating data. The energy and exergy indicators, their distribution and exergy loss are evaluated. The economic analysis was done by determining the Rate of Return on Investment, Payback Period and Net Present Worth. The optimal configuration of system equipment has been determined based on economic feasibility and emission saving in view of power and steam demand. The method employed here may be applied to making a decision on the adoption of the combined plant to any separate heat and power systems.

The biomass has been the choice of the heat source for cooking purposes since ancient times. The inefficient combustion process in traditional cookstoves has its shortcomings in the form of adverse consequences on human health and pollution of the environment. Research and development of improved cookstove, for those who are yet to adopt the cleaner fuels for the cooking, has occupied the scientific community and social workers alike to improve the conditions of these people. Most people who live in urban settings are using natural/petroleum gas or electricity for cooking. On the other hand, a large section of the people living in the hinterlands continue to use traditional cookstoves, which are of low efficiency and create indoor air pollution, which leads to severe health issues. To overcome these issues, many researchers have proposed various designs for improved cookstoves. This paper summarizes the available literature related to different cookstove designs, performance and emissions. The review covers detailed discussion on various parameters to enhance the performance of biomass cookstoves. In addition to that a comparison of different types of cookstoves, different fuels used in them, their efficiency and particulate matter emissions are studied. This paper also explores the possibility of the implementation of additional accessories such as thermoelectric generators. [ABSTRACT FROM AUTHOR]

The objective of this study is to measure and analyze consumers' satisfaction of electricity users (domestic) in Kolkata and its surrounding area depending upon various factors, such as the quality of services, supply restoration time, behavior of the Meter Inspectors and the pricing policy, billing system, bill payment systems and corporate imagery and consumer relationship. The present research was conducted with the use of a specially developed website questionnaire containing thirteen questions and consumers feedbacks were collected from February to March, 2021. The results were analyzed with a Fuzzy logic based consumer satisfaction index (CSI) developed by using the data obtained from the responses of the consumer feedback. Areas of improvements have been identified and mapped on the basis of survey results and to take corrective actions accordingly as recommended to enhance consumer satisfaction and consumer loyalty, which is the main purpose of the project work. This empirical study may serve as a reference for Any electricity provider who desires to carry out similar studies in the future. [ABSTRACT FROM AUTHOR]

Heat transfer and fluid flow characteristics in roughened solar air heater duct with combined square and equilateral triangular ribs as roughness is investigated using experimental and computational fluid dynamics (CFD) approaches. Relative roughness pitch (7.14 ≤ P/e ≤ 17.86), roughness height (e/D = 0.042), Reynolds number (3800≤ Re ≤ 18,000) and heat flux (1000 W/m2) are used as operating parameters. Turbulent flow is simulated using ANSYS FLUENT code with RNG k-ɛ turbulence model. The vortices generated around the ribs and grooves are considered to be responsible for the enhancement in heat transfer rate. Thermo hydraulic performance parameter (THPP) has been evaluated for optimum configuration of the roughness element for given set of geometrical and operating parameters. A value of 1.86 has been recorded as an optimum value of THPP for the range of parameters investigated. Solar air heater with combined ribs shows better performance when compared with the individual rib performances. [ABSTRACT FROM AUTHOR]

Processing of Congou black tea usually includes five procedures: withering, rolling, fermentation, first-drying and second-drying. Water content of a tea leaf is an important indicator for the black tea processing, particularly water loss most in first-drying, from 58%-64% of the fermented leaves to 20%-25% of the first-drying leaves. With a large amount of evaporation from leaf water and a rapid rise of leaf temperature, the enzymatic reaction in the leaves can be inhibited, while a large number of violent thermochemical reactions occur, in order to promote the transformation and upgrade of quality substances, and thereby to obtain the formation of excellent aroma, taste, color and other qualities of black tea. In this paper, two leaves and a bud of Fuding Dabai species were selected as raw material to make trial production of Congou black tea, in order to explore the influence of rotary pot-hot air coupling first-drying with electromagnetic heat on first-drying characteristic and quality formation of Congou black tea. Four methods were used, including chain plate hot air first-drying (CHFD), box hot air first-drying (BHFD), rotary pot first-drying (RFD), and rotary pot - hot air coupling first-drying with electromagnetic heat (RHFD). Multiple features and indicators were compared, such as 29 kinds of non-volatile tea indexes (polyphenols, catechins, tea pigments, soluble sugar, caffeine, amino acids, et al), 114 kinds of volatile aroma indexes that tested by GC-MS/MS, 10 kinds of evaluation indexes of leaf shape and liquor color, quality evaluation of artificial sensory and performance indexes of first-drying methods (production efficiency, energy cost, thermal efficiency, etc.). Partial least squares-discrimination analysis (PLS-DA) was then used to analyze the influence of first-drying methods on the taste, liquor color, and aroma quality formation of high-quality Congou black tea, finally to obtain the typical features of difference compounds. The results show that: 1) in RHFD treatment, the contents of tea polyphenols and total amount of catechins were the lowest, and the contents of total simple catechins, thearubigins, soluble sugar, TDE and 10TFRB were the highest, whereas the effect of first-drying methods on the content of theaflavins was not significant (P<0.05); 2) the total amount of volatile compounds was observed in the order of RHFD, RFD, BHFD, and CHFD; 3) the RHFD treatment can achieve the highest content of aromatic hydrocarbons, and terpenes. The rotary pot-hot air coupling first-drying (RHFD) method indicated some advantages, including fast heating (only 14 minutes), uniform temperature distribution and good stability, high thermal efficiency (50.0%), high production efficiency (220 kg/h), and low production cost (only 0.32 Yuan/kg). Moreover, the black tea after RHFD treatment has been significantly improved, indicating soup color brightness (La value), aroma sweetness, taste sweetness and refreshing, and the total score of sensory quality reaches the highest (88.1). PLS-DA also shows that Congou black tea can be distinguished by four kinds of first-drying methods from non-volatile (43 types obtained) and volatile (18 types obtained) compounds. The typical compounds are obtained, such as 2,4,6-tris(1,1-dimethylethyl)-4-methylcyclohexa-2,5-dien-1-one, geraniol, 3-octanone, methyl salicylate, theaflavin (TF), theabrownins (TBs), total soluble sugar (SSs), epicatechin (EC). These compounds can be used as indicators to identify the first-drying methods of Congou black tea, and then to produce “sweet fragrance aroma”, “sweet alcohol taste”, “high brightness liquor color” and other high-quality Congou black tea. This study can provide a technical reference and theoretical guidance to process much high quality of black tea. [ABSTRACT FROM AUTHOR]

This study proposes a novel curved steel plate damper to improve the seismic performance of structures. The theoretical analysis of the curved plate damper was carried out deriving formulas of key parameters of the curved plate damper including elastic lateral stiffness, yield strength, and yield displacement. Moreover, a cyclic loading test of four sets of specimens was conducted, and the hysteretic performance, ductility, energy dissipation performance, and strain of the specimens were studied. The results showed that the initial stiffness of the damper was large, no obvious damage was observed, and the hysteresis loop was full. The tested dampers had good deformation and energy dissipation performance. The stress variable rule of the damper was obtained by stress analysis, where the plastic deformation at the end of the semi-circular arc was large. The formula for various parameters of the damper was compared with experimental and numerical results; thus, the value of the adjustment coefficient was determined reasonable. Meanwhile, the rationality of the finite element model was also verified. [ABSTRACT FROM AUTHOR]

Numerical analysis plays vital role in designing gas turbine combustors for improving its performance. It requires deep understanding of turbulent and multiphase reactive flow physics inside the combustor. Hence present work focusses on numerical investigation of turbulent flow and reactive interaction between liquid spray of aviation kerosene droplets and air for the experimentally investigated combustor configuration. The present analysis results agree well with the experimental test results. Mixture fraction based Probability Density Function flamelet combustion model is used to solve transport equations by generating the flamelet library for Jet-A fuel. The analysis provides good insight into the multiphase combustion process and the flow phenomena occurring inside the combustor. Further, combustion performance characteristics at different design point operations are investigated in the present work keeping the air fuel ratio constant. Results show rise in peak velocity by 2.5 times and pressure loss factor by 6 for design point operating at higher flow rates in comparison with the baseline design operating point. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the root crop digger for digging of the potato crop at the farmer's field. The digger was tested at three levels of forward speeds (2.3, 2.8 and 3.3 kmh-1) and three levels of rake angles (170, 200, and 230). The experiment was replicated three times for the performance parameters of exposed,undug, cut, bruised percentage and the digging efficiency. The best performance of the digger was obtained at forward speed 2.3 km h-1 and blade angle 230 for potato crop at which the exposed, undug, cut, bruised percentage and the digging efficiency was found to be 90.62,2.10, 1.71, 2.48 and 97.90 per cent, respectively. About 54% savings in cost of digging could be achieved using digger compared to manual digging involving labour. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)