CFD Analysis of a Large Marine Engine Scavenging Process

The scavenging process is an important part of the two-stroke engine operation. Its efficiency affects the global engine performance such as power, fuel consumption, and pollutant emissions. Slow speed marine diesel engines are uniflow scavenged, which implies inlet scavenging ports on the bottom of the liner and an exhaust valve on the top of the cylinder. A CFD model of such an engine process was developed with the OpenFOAM software tools. A 12-degree sector of the mesh was used corresponding to one of the 30 scavenging ports. A mesh sensitivity test was performed, and the cylinder pressure was compared to experimental data for the analyzed part of the process. The scavenging performances were analyzed for real operation parameters. The influence of the scavenge air pressure and inlet ports geometric orientation was analyzed. The scavenging process is analyzed by means of a passive scalar representing fresh air in the cylinder. Isosurfaces that show the concentration of fresh air were presented. The variation of oxygen and carbon dioxide with time and the axial and angular momentum in the cylinder were calculated. Finally, the scavenging performance for the various operation parameters was evaluated by means of scavenging efficiency, charging efficiency, trapping efficiency, and delivery ratio. It was found that the scavenging efficiency decreases with the engine load due to the shorter time for the process. The scavenging efficiency increases with the pressure difference between the exhaust and scavenging port, and the scavenging efficiency decreases with the increase in the angle of the scavenging ports. It was concluded that smaller angles than the industry standard of 20° could be beneficial to the scavenging efficiency. In the investigation, the charging efficiency ranged from 0.91 to over 0.99, the trapping efficiency ranged from 0.54 to 0.83, the charging efficiency ranged from 0.78 to 0.92, and the delivery ratio ranged from 1.21 to 2.03.

Optimizing Regenerative Braking: A Variational Calculus Approach

We begin by analyzing, using basic physics considerations, under what conditions it becomes energetically favorable to use aggressive regenerative braking to reach a lower speed over “coasting” where one relies solely on air drag to slow down. We then proceed to reformulate the question as an optimization problem to find the velocity profile that maximizes battery charge. Making a simplifying assumption on battery-charging efficiency, we express the recovered energy as an integral quantity, and we solve the associated Euler–Lagrange equation to find the optimal braking curves that maximize this quantity in the framework of variational calculus. Using Lagrange multipliers, we also explore the effect of adding a fixed-displacement constraint.

An Intelligent Wireless Charger Based on the Internet of Things

With the development of the times and the progress of science and technology, people continue to explore new possibilities; the leap from wired to wireless is one of them, breaking the limitations. Similar to wireless mice and wireless microphones, this paper aims to study an Internet of Things-based smart wireless charger that, by using mathematical analysis and wireless charging technology, requires experiments to include wireless charging stations, associated chip areas, and home gateways that are used in combination with them. In the experiment, the control circuit, transmit circuit, and reception circuit of wireless charger are studied, and the wireless charging system is analyzed and calculated in detail, and a wireless charger is designed. Electromagnetic field sensing, radio wave transmission, and resonance methods are applied to achieve the shortest charging time and the best quality in order to prevent the charger from heating and burning during charging. Experimental data show that this Internet of Things-based smart wireless charger can fully replace wired chargers for 99% of small appliances; the charging efficiency of large electrical appliances such as desktop computer is also 1.4 to 1.6 times increased. Experimental data show that this Internet of Things-based smart wireless charger can efficiently and conveniently charge electrical appliances; however it is relatively expensive; the required technology is relatively complex but can make charging more efficient. It can be seen that wireless charging has a major breakthrough in the concept of future charging.

Charging device for wearable electromagnetic energy-harvesting textiles

The study aims to develop charging devices for wearable electromagnetic energy harvesting textiles (WEHT). Electromagnetic energy through human movement can be easily and naturally generated and is not significantly affected by environmental factors, however, the electric current generated by the electromagnetic method of human movement is difficult to efficiently charge. Three charging circuits for use with wearable electromagnetic energy-harvesting textiles were developed. The three types of charging circuits developed are rectifier, voltage doubler, and voltage quadrupler circuits. The performances of the developed circuits were evaluated in comparison with a normal storage circuit, in which the generated energy is stored immediately. The results show that storage energy was generated from the WEHT in all the developed circuits, and the charging efficiency improved as the simulated walking frequency increased. Energy generated from wearable electromagnetic energy harvesting textiles has the highest storage efficiency when charged with a rectifier circuit. The rectifying circuit method showed a charging rate twice that of a normal storage circuit. The charging speed of the rectifier circuit was faster to reach 3.7 V, the nominal maximum barrier voltage of the single-cell lithium-ion batteries used in portable devices, than the normal charging circuit. In the voltage multiplier circuit, the voltage drop generated in the circuit was large, so the charging efficiency was not superior to the normal circuit or rectifier circuit. In conclusion, it is most effective to use a rectifier circuit for charging portable electronic devices using the energy harvested by wearable electromagnetic energy harvesting textiles.

Marine diesels mechanical charging driving improvement through overrunning-safety clutch application

Article deals with marine diesels mechanical charging driving protecting problem. On the base of marine diesel EMD 710G overrunning clutch construction analysis its disadvantages were highlighted. Main of them is the principle of working load transfer by friction forces. That is the reason of clutch skidding in operation and charging efficiency degradation. A new design of the safety-overrunning clutch for marine diesels mechanical charging driving, based on the principle of engagement is proposed. In new overrunning-safety clutch construction, which protected by patent, the overrunning and safety parts are mutually integrated. Clutch operations on the overrunning and overload modes are described. On the basis of ball acting forces on steady motion description expressions for its static balance are obtained. Those static balance expressions were the basis for coupling nominal working torque ratios receiving. On the next stage ball forces balance on the overload mode was analyzed. As a result of those stage studies expressions for calculating overload spring deformation, torques of the beginning and ending of its operation are obtained. On the basis of clutch nominal torque, torques of beginning and ending operation the ratios for assessing the main operational characteristics of the coupling when operating in overload mode are obtained - coefficients for exceeding the nominal torque, response accuracy and sensibility.

Characterization of a non-thermal plasma source for use as a mass specrometric calibration tool and non-radioactive aerosol charger

In this study the charging efficiency of a radioactive and a non-radioactive plasma bipolar diffusion charger (Gilbert Mark I plasma charger) for sub-12 nm particles has been investigated at various aerosol flow rates. The results were compared to classic theoretical approaches. In addition, the chemical composition and electrical mobilities of the charger ions have been examined using an atmospheric pressure interface time-of-flight mass spectrometer (APi-TOF MS). A comparison of the different neutralization methods revealed an increased charging efficiency for negatively charged particles using the non-radioactive plasma charger with nitrogen as the working gas compared to a radioactive americium bipolar diffusion charger. The mobility and mass spectrometric measurements show that the generated bipolar diffusion charger ions are of the same mobilities and composition independent of the examined bipolar diffusion charger. It was the first time that the Gilbert Mark I plasma charger was characterized in comparison to a commercial TSI X-Ray (TSI Inc, Model 3088) and a radioactive americium bipolar diffusion charger. We observed that the plasma charger with nitrogen as the working gas can enhance the charging probability for sub-10 nm particles compared to a radioactive americium bipolar diffusion charger. As a result, the widely used classical charging theory disagrees for the plasma charger and for the radioactive chargers with increased aerosol flow rates. Consequently, in-depth measurements of the charging distribution are necessary for accurate measurements with differential or scanning particle sizers for laboratory and field applications.

Investigations on the Triboelectrostatic Charging Behaviour and the Triboelectrostatic Sortability of Different Oxides

In the course of this study, several test series were carried out to investigate the triboelectrostatic charging behaviour of various oxides. At the beginning, the influence of the degree of aging and the influence of the sample storage on the charging efficiency of the oxide samples was analysed. For this purpose, two oxide samples were stored under different environmental conditions and then sorted using triboelectrostatic belt separation. Results of a previous series of tests showed that an increased feed temperature has a negative effect on the charging behaviour of calcium and magnesium oxide. Therefore, the effects of a reduced feed temperature were also examined. For these experiments, samples were stored at 8 °C under exclusion of air. In addition, a series of tests was carried out with a gradual increase of the voltage on the triboelectrostatic belt separator in order to determine possible differences in the charging efficiency of calcium oxide and magnesium oxide and to subsequently use them for the separation.

A Safe Charging Algorithm Based on Multiple Mobile Chargers

A safe charging algorithm in wireless rechargeable sensor network ensures the charging efficiency and the electromagnetic radiation below the threshold. Compared with the current charging algorithms, the safe charging algorithm is more complicated due to the radiation constraint and the mobility of the chargers. A safe charging algorithm based on multiple mobile chargers is proposed in this paper to charge the sensor nodes with mobile chargers, in order to ensure the premise of radiation safety, multiple mobile chargers can effectively complete the network charging task. Firstly, this algorithm narrows the possible location of the sensor nodes by utilizing the charging time and antenna waveform. Secondly, the performance of non-partition charging algorithm which algorithm allow chargers to charge different sensors sets in a different cycle is evaluated against the one of partition charging which does not allow for charging different ones. The moving distance of the charger node will be reduced by 18%. It not only improves the safety level which is inversely proportional to electromagnetic radiation but also expands the application scope of the wireless sensor nodes.