Analysis of Tangential Combustion Instability Modes in a LOX/Kerosene Liquid Rocket Engine Based on OpenFOAM

Self-excited high frequency combustion instability (HFCI) of first-order tangential (1T) mode was observed in a staged-combustion LOX/Kerosene liquid rocket engine numerically. Two different kinds of 1T patterns, standing wave mode and traveling wave mode, were captured in the present work. In the nominal operation condition, the ratio of oxygen-to-fuel (O/F) was 2.5. Propellant was evenly distributed in all injectors and no HFCI occurred. The chamber pressure obtained from the numerical simulation and experiment showed a good agreement, which validated the numerical model. When the mass flow of fuel for two injectors was modified, severe HFCI occurred. The pressure wave node was located at a fixed diameter, showing a 1T standing wave mode. As the O/F was set 4.4 and the propellant distribution was completely uniform, the numerical result yielded a 1T wave node featured a spinning behavior, which was a traveling 1T wave mode. Once the HFCI arose, no matter what standing mode or spinning mode, the pressure and heat release oscillated totally in phase temporally and coupled spatially. The heat release from combustion was fed into the resonant acoustic mode. This was the thermoacoustic coupling process that maintained the HFCI.

Development of Integrated Electrocoagulation-Sedimentation (IECS) in Continuous Mode for Turbidity and Color Removal

The present work focused on the development and evaluation of a compact electrocoagulation (EC) reactor, combined between EC and clarifier processes in continuous modes for decolorization and turbidity removal, named the integrated electrocoagulation-sedimentation reactor (IECS). The experiments were firstly conducted in the four-liter batch column in order to optimize the EC configuration and operation condition. The removal kinetics were also investigated and predicted for kinetic correlations. After various optimization steps, the IECS reactor was conducted, consisting of EC and clarifier compartments. Liquid flow pattern in EC compartment was examined through resident time distribution technique for defining the number of EC units and divided baffles. In summary, four units of EC were placed in the EC compartment of the IECS reactor with 90% in the width of three baffles. Each EC unit had two pairs of aluminum electrode plats in monopolar arrangement with a 1.5 cm gap and required a current density of 13.5 mA/cm2. For the clarifier compartment, it was mainly designed based on the batch settling test for separating the precipitated particles. The treatment performance of the IECS reactor was tested at different liquid flows in order to reduce the pollutant to a certain level. For the individual condition, liquid flow rates of 3 and 1 L/min were defined for turbidity and color, respectively. If both pollutants are presented simultaneously, a liquid flow rate of 1–2 L/min can be used for decreasing turbidity from 250 to <20 NTU and color from 6000 to <300 ADMI.

Exsolution in La and Ni co-doped strontium titanate: a suitable anode for running SOFCs on ammonia as alternative fuel

Ammonia exhibits interesting features as fuel to feed Solid Oxide Fuel Cell. Herein, Ni and La co-doped strontium titanate was synthetized using wet chemistry route. Ni nanoparticles emerged via exsolution in reducing environment to decorate the surface. X-Ray Diffraction measurements exhibits perovskite structure was also preserved after the exsolution, as expected. H2 – Temperature Programmed Reduction highlights the great resistance of titanates in anode operation condition. Ammonia conversion in nitrogen and hydrogen were investigated by catalytic tests. It begins to decompose at 560°C and the full yield was achieved at 720°C. Electrochemical measurements were recorded at 800°C using 10% of ammonia in Ar. They were analysed though the model of equivalent circuit and two processes were attributed. Results certify Ni exsolution strongly enhances the hydrogen oxidation and the total polarisation resistance in ammonia approaches to the one in hydrogen.

Research on On-Line Monitoring System of Hydraulic Actuator of Combine Harvester

In view of the complicated hydraulic system, the many driving parts and the great load variation in the combine harvester, and on-line monitoring methods of hydraulic actuating parts such as cutting tables, conveyors and threshing drums were studied. By analyzing the working principle of the hydraulic system of the combine harvester, a mathematical model of the hydraulic system of the combine harvester was established; a simulation model for the fault diagnosis of the hydraulic system of the combine harvester was established based on AMESim. The load signal was introduced to simulate the feeding amount, and the simulation test was carried out. According to the simulation analysis results, the best position of each monitoring point was determined. The on-line monitoring system of the hydraulic actuators of the combine harvester was designed by using LabView, which can collect and display the working parameters of the main working parts of a combine harvester in real time, and alarm the user to faulty working conditions. The field experiment results show that the function and precision of the monitoring system completely meet the requirements of field operation condition monitoring of combine harvesters. The accuracy rate of the fault alarm is 96.5%, and the automatic diagnosis time of the fault alarm is less than 1 min and 18 s, which greatly improves the operation efficiency of the combine harvester.

An Overview of Digital Twin Concept for Key Components of Renewable Energy Systems

Renewable energy (RE) is green and low-carbon energy, which can not only protect the environment, promote the technological diversification of the energy supply system, accelerate the adjustment of energy structure, but also has important significance for the sustainable development of economy. With the increasing complexity of the problems of renewable energy system asset management and ensuring the operational reliability of electric power equipment, it's necessary to establish remote, online, reliable monitoring and inspection techniques for the state evaluation of electrical equipment during the full life cycle. In order to meet these demands, the digital twin is a very suitable technology. In recent years, there are numerous scientific papers demonstrating DT's capabilities in virtual simulation, condition monitoring (CM), power optimization and fault diagnosis for RE generation systems, transmission and transformation equipment and storage systems. The majority of the research focusing on product design, maintenance of operation, condition monitoring and fault decision-making has provided many valuable contributions to academia and industrial fields. Nevertheless, all this valuable information is scattered over many literatures and it is lack of systematic generalization. In this article, different applications of DT technology in RE system are analyzed, advanced methods and theories are summarized comprehensively, and the development trend of DT technology in renewable energy system in the future is introduced.

Characteristics of carbide slag slurry flow in a bubble column carbonation reactor

The direct aqueous mineral carbonation of carbide slag was investigated. The flow characteristics of carbide slag-CO2-water reaction system in a bubble column were studied, which included the bubble Sauter mean diameter, gas holdup, bubble residence time, and the gas-liquid interfacial area. Bubble flow behaviors in the reactor were characterized by analyzing the bed pressure signals. The effects of the gas velocity (U g ) and liquid to solid ratio (L/S ratio) were discussed and analyzed. The results showed that the larger bubbles were easy to form at the larger L/S ratio, which indicated that the bubble coalescence was promoted. The gas holdup was larger when increasing U g or reducing the L/S ratio. The better gas-liquid interfacial areas were found in a wide range of L/S ratio at U g = 0.082 m/s. The optimum conditions were found at U g = 0.082 m/s and L/S ratio = 15–30 mL/g for the better gas-liquid interfacial area and the higher carbide slag conversion. The work provided the theoretical basis for the direct aqueous carbonation of the carbide slag and the operation condition optimization.

Facile Synthesis of β-PbO2 Nanoparticles Range from 10-30 nm and their Application for Ozone Generation

β-PbO2 is an important high oxygen overpotential anode coating material. Further study on nanoscale β-PbO2 with higher performance and lower cost is a critical issue in order to develop the electrochemical ozone generator. Herein, an improved β-PbO2 nanoparticles synthesizing strategy based on the traditional Pb(OAc)4 hydrolysis method is proposed in this work, which is more scalable for industrial-scale production compared with existed nano β-PbO2 synthesizing methods. The possible mechanism of synthesizing β-PbO2 nanoparticles via Pb(OAc)4 hydrolysis was discussed for the first time. Based on the proposed mechanism, the size and morphology of the β-PbO2 nanoparticles were effectively controlled, and alternative raw material that can significantly reduce costs was developed. SEM, TEM, XRD, and XPS results indicate that pure phase β-PbO2 nanoparticles range from 10-30 nm were obtained. In addition, the use of alternative raw materials reduces the cost by 90%-95% compared to the traditional Pb(OAc)4 hydrolysis method. The β-PbO2 nanoparticles showed good ozone generation performances. The energy consumption per unit ozone of the β-PbO2 nanoparticles is reduced by 51.9% at the optimized operation condition than the reference PbO2 particles used for comparis

CONSIDERATION OF THE "CONDITION-BASED" ALGORITHM OF AVIATION EQUIPMENT OPERATION WITH THE USE OF GROUND MEANS OF TECHNICAL CONTROL AND ON-BOARD MEASURING SYSTEMS IN THE STATE AVIATION OF UKRAINE

The article highlights the main aspects and features of the algorithm of aviation equipment operation "condition-based" with the use of ground technical means of control and on-board measuring systems and the formation of decision- making principles for further operation of aircraft. To develop methods of technical diagnostics of any technical equipment, it is necessary to identify which parameters characterize its condition and reliability as well as to establish diagnostic criteria and limit values of the controlled parameters. Depending on the nature of the parameters being controlled, there are parametric and physical methods of diagnostics. Based on the results of the diagnostics, we must get a straight answer: whether or not it is necessary to perform repairs or maintenance of the equipment being tested, taking into account the ensuring of failure-free operation before the next diagnostics. Currently, a large number of different measuring equipment that can measure signals that meet the parameters of the object of control and diagnostics are successfully used to objectively determine the technical condition of aircraft. The use of the laboratory for technical diagnostics of aviation equipment in conjunction with on-board measuring systems will provide an opportunity to make a quality technical diagnostics and reasonable conclusion to decide on further operation of the sample of aviation equipment. The use of mentioned laboratory will also predict the occurrence of failures of aviation equipment systems and units. Only a comprehensive approach to the technical diagnostics of aviation equipment with employment of all means of technical control (ground, on-board) will prevent sudden failures of aviation equipment systems.

Not toeing the number line for simple arithmetic: Two large-n conceptual replications of Mathieu et al. (Cognition, 2016, Experiment 1)

We conducted two conceptual replications of Experiment 1 in Mathieu, Gourjon, Couderc, Thevenot, and Prado (2016, https://doi.org/10.1016/j.cognition.2015.10.002). They tested a sample of 34 French adults on mixed-operation blocks of single-digit addition (4 + 3) and subtraction (4 – 3) with the three problem elements (O1, +/-, O2) presented sequentially. Addition was 34 ms faster if O2 appeared 300 ms after the operation sign and displaced 5° to the right of central fixation, whereas subtraction was 19 ms faster when O2 was displaced to the left. Replication Experiment 1 (n = 74 recruited at the University of Saskatchewan) used the same non-zero addition and subtraction problems and trial event sequence as Mathieu et al., but participants completed blocks of pure addition and pure subtraction followed by the mixed-operation condition used by Mathieu et al. Addition RT showed a 32 ms advantage with O2 shifted rightward relative to leftward but only in mixed-operation blocks. There was no effect of O2 position on subtraction RT. Experiment 2 (n = 74) was the same except mixed-operation blocks occurred before the pure-operation blocks. There was an overall 13 ms advantage with O2 shifted right relative to leftward but no interaction with operation or with mixture (i.e., pure vs mixed operations). Nonetheless, the rightward RT advantage was statistically significant for both addition and subtraction only in mixed-operation blocks. Taken together with the robust effects of mixture in Experiment 1, the results suggest that O2 position effects in this paradigm might reflect task specific demands associated with mixed operations.

A CMOS PSR Enhancer with 87.3 mV PVT-Insensitive Dropout Voltage for Sensor Circuits

A new power supply rejection (PSR) based enhancer with small and stable dropout voltage is presented in this work. It is implemented using TSMC-40 nm process technology and powered by 1.2 V supply voltage. A number of circuit techniques are proposed in this work. These include the temperature compensation for Level-Shifted Flipped Voltage Follower (LSFVF) and the Complementary-To-Absolute Temperature (CTAT) current reference. The typical output voltage and dropout voltage of the enhancer is 1.1127 V and 87.3 mV, respectively. The Monte-Carlo simulation of this output voltage yields a mean T.C. of 29.4 ppm/°C from −20 °C and 80 °C. Besides, the dropout voltage has been verified with good immunity against Process, Temperature and Process (PVT) variation through the worst-case simulation. Consuming only 4.75 μA, the circuit can drive load up to 500 μA to yield additional PSR improvement of 36 dB and 20 dB of PSR at 1 Hz and 1 MHz, respectively for the sensor circuit of interest. This is demonstrated through the application of an enhancer on the instrumentation Differential Difference Amplifier (DDA) for sensing floating bridge sensor signal. The comparative Monte-Carlo simulation results on a respective DDA circuit have revealed that the process sensitivity of output voltage of this work has achieved 14 times reduction in transient metrics with respect to that of the conventional counterpart over the operation temperature range in typical operation condition. Due to simplicity without voltage reference and operational amplifier(s), low power and small consumption of supply voltage headroom, the proposed work is very useful for supply noise sensitive analog or sensor circuit applications.