Entire Load Range Research Articles

Експериментальні дослідження величини прогину пластини для корекції лійкоподібної деформації грудної клітки під впливом згинаючого навантаження

One of the leading methods of reconstruction of the funnel-shaped deformity of the chest is nonresection thoracoplasty, or Nuss surgery. For its implementation, implanted systems consisting of one or two corrective plates are used. The technique is minimally invasive, does not require large incisions and resection of ribs. But there are complications related to the insufficient strength of bone tissue, which according to the literature is defined in a very wide range. Purpose - to determine the dependence of the amount of deflection of single and double plates for the correction of sternum deformity on the amount of bending load; to develop a method of determining the corrective load that the plate exerts on bone structures during correction. Materials and methods. Experimental studies of plates for correction of sternum deformities were performed. We used 6 plates. In the first part of the experiment, each plate was tested separately. In the second part, the plates were connected in pairs, and each pair was tested for bending. In total, 3 pairs of plates were tested. The bending force was gradually increased from 0 N in increments of 50 N. At each step, the deflection of the plate was recorded. Results. The results of experimental studies of single plates showed that the deviation of deflection values did not differ statistically significantly (p>0.05) from the calculated values over the entire range of bending loads. The studies of the twin plates for the correction of sternum deformities also did not reveal statistically significant (p>0.05) differences in the deflection values of the samples obtained in the experiment from the calculated values. The results of the study made it possible to develop a methodology for calculating the force with which the plate acts on the sternum when correcting its deformation. Conclusions. A methodology has been developed for determining the force with which the plate acts on the sternum when correcting a deformation of a certain magnitude. It is confirmed that the calculated data on the deflection of the plate under the influence of bending load and the data obtained in the experiment do not differ statistically significantly. The data obtained can be useful for selecting the size of the corrective plate, the method of its attachment to the ribs, as well as for modeling the options for applying plates to correct various sternum deformities. The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local Ethics Committee of the institution mentioned in the paper. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the authors.

Efficiency optimization for LCC‐LC compensated inductive coupling power transfer system with load‐independent zero‐phase‐angle and constant voltage output

SummaryHigh‐order compensation for the inductive coupling power transfer (ICPT) system is preferred due to its high design freedom and excellent coil current harmonics suppression capability. Especially, the good harmonics suppression capability is helpful to implement the synchronous wireless transfer of energy and data with a pair of data communication coils integrated into the energy transfer coils. Thus, on basis of THD1 and THD2 comparison for different high‐order compensation topologies, the LCC‐LC compensated ICPT system with load‐independent zero phase angle (ZPA) and constant voltage output is discussed in this paper. Compared with other high‐order compensation topologies with constant voltage output such as LC‐LC, LC‐LCC, and LCC‐LCC, the LCC‐LC has the advantages of ZPA operation with zero voltage switching and less secondary‐side components. For a given magnetic coupler, infinite feasible combinations of compensation parameters can make the system accomplish ZPA and the same output characteristics. Thus, efficiency optimization of the LCC‐LC compensated ICPT system can be investigated by configuring the optimal compensation parameters. To validate the theoretical analysis, especially the efficiency improvement, the experimental platform with 270 V input and 270 V/3 kW output is designed and built. The comparative experimental results for three different the compensation parameters show the optimized system can improve greatly conversion efficiency over the entire load range, especially under light load.

A Load Adaptive Hybrid DPS Control for DAB to Secure Minimum Current Stress and Full ZVS Operation Over Wide Load and Voltage Conversion Ratio

Wide variations in voltage conversion ratio and loading are the most important parameters to consider when designing off-board EV chargers to achieve high power density and efficiency. Dual phase shift (DPS) modulation provides a better way for dual active bridge (DAB) DC-DC converter operation when load side parameter variation is utmost important. To accomplish this, conventional DPS control is modified to ensure zero voltage switching (ZVS) across the entire load range despite wide variations in voltage conversion ratio. The designed control provides ZVS of all FETs as compared to the conventional DPS control over full loading range. For this, magnetizing inductance of HF isolation transformer is utilized and designed to shape the secondary side current for getting ZVS for both active legs. The light loading performance of the converter is improved with the bidirectional conduction angle control. The hybrid utilization of DPS control is incorporated with minimum peak current stress considerations. A Karush-Kuhn-Tucker (KKT) method based on Lagrange's multipliers is used for mathematical derivation of optimized solution of both control parameters. Performance of designed control is verified using experimental results for wide variation in battery terminal voltage. For validation, a 1250 W laboratory prototype is developed. A comparison of ZVS regions among the conventional and designed modulation technique, shows the effectiveness under wide voltage and loading scenarios.

Designing of traction motor stators core

Electric drive is widely used in automotive practice. Its basis is an electric traction motor (TM), which, compared with an internal combustion engine (ICE), has such advantages as high efficiency, high overload capacity, a wide range of speed control, and the possibility of torque direct transmission to the drive wheels. The main requirements for a traction motor are high efficiency over the entire load range, ease of speed and torque control, high overload capacity, small weight and dimensions, regenerative braking capability, wide speed control range, simplicity and ease of maintenance. The most widely used as traction motors are synchronous electric machines with excitation from permanent magnets (PM). They are characterized by high torque density, efficiency and power consistency over a wide speed range. However, there are a number of problems that hinder the introduction of these electric machines in the traction drive of home cars, one of which is the lack of a methodology for choosing the design of an armature and an inductor at the stage of calculating the main dimensions of an TM with magnetoelectric excitation, taking into account the variety of schemes and methods of winding, PM placement in the inductor. The article deals with the issues of choosing electromagnetic loads for various cooling methods, the size of the non-magnetic gap, an algorithm for electromagnetic calculation based on the maximum torque, containing a number of refining cycles, is proposed. The values of inductances and design factors are determined by numerical simulation of the magnetic field. The features of the design and circuit design of the core and armature winding are considered. Distribution curves of magnetomotive forces of distributed and concentrated windings are obtained, their harmonic analysis is made, recommendations are given on the configuration of the TD armature active zone.

Assessment of Performance and Emission Characteristics of Compression Ignition Engine Using Diesel and Diesel Biodiesel Blends: Experimental and Simulation Studies with Data Analysis Techniques

Control of air pollution has more concern due to its adverse effect on health and the environment. The increase in air pollution is due to the utilization of fossil fuels to satisfy the energy demand. Exhaust emissions from internal combustion engines are one of the major contributors to environmental pollution, hence control of the same at and after the source is most important, which is the focus of the present study. This study primarily focuses on the use of biodiesel as an alternative fuel to substitute partially diesel fuel, which is one of the promising solutions to counter the adverse effects of engine emissions. The present study comprises three stages. Initially, experiments were conducted on a diesel engine (5 HP, 1500 rpm, water-cooled, and direct injection) using both diesel and biodiesel blend (B20, 80% diesel, and 20% biodiesel) to assess the performance and emission parameters at various engine loads, while maintaining an engine speed (1500 rpm) constant. In the second stage, a Simulink model was created to validate the engine performance and emission parameters obtained during the experimental study. Lastly, data analysis techniques were employed in the third stage to facilitate decision-making based on the acquired data, ensuring a certain level of confidence and accuracy. This study utilizes both univariate and bivariate data analysis techniques to interpret the experimental data obtained from the engine. From the theoretical analysis, it is observed that there is a good agreement between the experimental and predicted values of performance and emission parameters of the engine. From the data analysis it is observed that when the engine is fueled by B20 fuel, there is an increase in NOx emissions by approximately 8 ~ 11% and CO2 emissions by approximately 7 ~ 17% in comparison with diesel fuel for the entire range of engine loads. Conversely, there is a decrease in unburned hydrocarbon (UBHC) emissions by 1.27 ~ 29.6% and CO emissions by 13 ~ 42% in comparison with diesel fuel for the entire range of engine loads. Furthermore, the use of biodiesel results in a 6 ~ 17% increase in fuel consumption compared to diesel fuel while maintaining the same power output. Based on these observations, it can be concluded that biodiesel is one of the best alternative fuels for enhancing both the engine's performance and emission characteristics. Moreover, it offers a means to control vehicular air pollution effectively.

Optimization of the Control of Electromagnetic Brakes in the Stand for Tuning Internal Combustion Engines Using ID Regulators of Fractional Order

This work is aimed at developing a stand for tuning the fuel system of an internal combustion engine based on two electromagnetic retarders connected to the driving wheels of a car to simulate a load, and a microprocessor-based torque control system for each brake. In accordance with the terms of reference from the specialists of the automotive service center, such a stand should provide two main modes of operation: (1) stabilization of the speed of the drive wheels in the entire range of loads (fuel supply); (2) engine acceleration and deceleration according to linear tachograms in the range from minimum to maximum speed to determine the dependence of engine power and torque on speed. The purpose of this research is the synthesis of controllers, testing, the choice of the structural scheme, and the parameters of the control and data processing system in the stand for the precision tuning of internal combustion engines. Based on a preliminary analysis of the system, taking into account the mechanical connection of the wheels through the main gear and the car differential, the nonlinear dependence of the electromagnetic torque on the current and retarder speed, and subsequent experimental results, we obtained two types of controller—a third-order aperiodic transfer function and a fractional aperiodic transfer function of order 1.6. This made it possible to synthesize a family of controllers that ensure the operation of the stand in the required modes: synchronization of wheel speeds during engine acceleration; stabilization of the reference speed when the engine torque is changed from minimum to maximum due to fuel supply; measurement of the maximum power and torque of the internal combustion engine during the formation of a triangular tachogram with a given acceleration to compensate for the dynamic component of the torque due to mechanical inertia. The system with the PID controller configured in MATLAB in the “Tune” package has the best performance, but the smallest overshoot and the best dynamic accuracy are ensured by the PIDIγIµ fractional–integral controller, where the system is characterized by a fractional order of astaticism 1.6. Such a controller for each electromagnetic retarder serves as the basis of the microprocessor-based control, data acquisition, processing, graphical display system, and will also be used to develop a similar bench for tuning four-wheel-drive vehicles.

입력전압 및 구동주파수 변화에 따른 직렬-직렬 보상 무선전력전송회로의 성능 분석

In series-series compensated wireless power transfer, input voltage control and operating frequency control methods are used to improve the problem of output voltage change according to load variation. However, if two methods are used to maintain the output voltage, the efficiency of the circuit and the power loss of each element change. Therefore, in this paper, the characteristics, advantages and disadvantages of these methods are compared and analyzed through simulation. For this, the coil and circuit parameters are calculated using COMSOL simulator and design equations to model the circuit, and the performance of the two methods is compared and analyzed with PSIM simulator. In the simulation, when the load changes from 4.5Ω to 9Ω at an output power of 9W to 18W, the output voltage is maintained at 9V by using the input voltage or frequency control methods. As a result of the simulation, the input voltage control method produces an output voltage of 9V in the entire load range by increasing the input voltage even if the voltage gain is not sufficient, and has the maximum efficiency of 86.55% at a load of 4.5Ω. On the other hand, the frequency control method can not produce an output voltage of 9V because the voltage gain is small at a low load, and the circuit efficiency decreases due to an increase in the reactive current at a high load.

Experimental investigations on biodiesel-water emulsion as a potential fuel for early and late injection based premixed lean combustion

Low temperature combustion strategies are a suitable alternative to conventional diesel combustion to simultaneously reduce oxides of nitrogen and smoke emissions while maintaining engine performance. However, limited load range and increased unburned hydrocarbon and carbon monoxide emissions are challenges posed by these strategies. The present investigation aims to address these limitations using biodiesel-water emulsion as a potential fuel for low temperature combustion in a light-duty diesel engine. Biodiesel derived from non-edible Karanja oil and its emulsion containing 18% water was used. The surfactant employed to stabilize the biodiesel-water emulsion was the raw Karanja oil itself. Two different fuel injection strategies were explored to achieve lean premixed combustion: early/advanced injection and late injection just after the top dead centre. To implement these strategies, the mechanical fuel injection system in the production engine was replaced with an electronic injection system having complete flexibility over the injection schedule. The results are compared with conventional diesel combustion under production settings. For the early injection strategy, up to 40% load, the brake specific fuel consumption and brake thermal efficiency were on par with conventional diesel combustion for biodiesel and the emulsion. However, there was a decline in the performance for both fuels at 60% load, which was the maximum achievable load with an early injection strategy. With the late injection, the engine could be operated across its entire load range with similar reductions in oxides of nitrogen and smoke emissions. While the brake thermal efficiency and brake specific fuel consumption for biodiesel were on par with conventional diesel combustion, there was an improvement of 8 and 6%, respectively, with biodiesel-water emulsion. The emission results showed that with either injection strategies, with biodiesel and its emulsion, 85 and 80% reduction in oxides of nitrogen and smoke emissions, respectively, could be achieved compared to conventional diesel combustion. However, both strategies significantly increased hydrocarbon and carbon monoxide emissions compared to conventional diesel combustion.

SIMULATION OF WORKING MODES OF THE ELECTRICAL DRIVE OF A LIFTING CRANE WINCHES IN MATLAB

Among the most common mechanisms in the industry are lifting machines of various types and designs. They are widely used in construction and assembly, repair, warehouse and other works related to lifting and moving large and heavy loads. The main and most energy-intensive mechanism of lifting machines is the lifting winch. The electric drive of the lifting winch must meet the increased operational requirements and ensure the performance of the given speed diagram, the necessary dynamics of work and high reliability in the operating modes. The energy indicators of the electric drive of the lifting winch mainly determine the energy indicators of the machine as a whole, therefore, due attention should be paid to the issue of designing the electric drives of the lifting winches. It is worth noting that the kinematic connections of the lifting winch are not absolutely rigid, which determines the occurrence of oscillations in the system as a result of dynamic forces. It is the presence in the electromechanical system of the lifting winch of elements with high inertia that causes the appearance of elastic oscillations during any transient process in this system. The presence of elastic oscillations in the mechanical system of the electric drive distorts the speed graphs of the system and leads to force pulsations. Elastic oscillatory processes in mechanisms lead to unpredictable behavior of the system and can cause emergency situations. Thus, taking into account the elastic properties of the mechanical system during its design will improve the efficiency and reliability of its operation. The results of the research carried out in the work contain the analysis of static loads of lifting winches of lifting and transport mechanisms and a generalized mathematical model of the crane lifting winch. On the basis of the proposed mathematical model, a structural diagram of a lifting winch was developed and implemented as a computer model in the form of a Matlab Smulink PPP library block. The mathematical and computer models presented in the work allow obtaining correct results in the entire range of loads, taking into account the change in the efficiency of the mechanical transmission when the loads and the direction of transportation change, and also take into account the influence of the elastic connection between the drive motor and the actuator. The use of the proposed models will significantly simplify the process of designing the power electric drive of lifting winches of cranes.

Integration of Three-Phase LLC Resonant Converter and Full-Bridge Converter for Hybrid Modulated Multioutput Topology

A multioutput dc–dc topology based on hybrid modulation of pulse frequency modulation and the phase shift is proposed in this article. The proposed hybrid modulated multioutput converter is derived from the integration of a three-phase LLC resonant converter and the full-bridge converter. With the hybrid modulation, the multioutput is controlled independently free from cross-regulation and isolated from each other. With the three-phase interleaving operation, the resonant currents can be reduced, and thus, the efficiency will be improved. Furthermore, the output current ripple of the main output voltage is reduced; as a consequence, the lifetime of the output filter capacitor is extended, and the reliability is reinforced. What is more, the number of the power switches is reduced, and the zero-voltage switching of the power switches can be achieved within the entire load range by the proposed integrated topology. All the abovementioned features of the proposed converter will lead to a compact, efficient, and cost-effective design. Finally, a 1.4-kW triple-output laboratory prototype is built and tested to validate the feasibility and effectiveness of the proposed converter.

Effect of addition of fuel additive in diesel with hydrogen on combustion duration

Hugh energy demand in all countries caused expeditious depletion of conventional resources of energy. The adverse effect of unregulated utilization of conventional energy sources resulted into lack of stock left and the emission of harmful pollutants into the environment. There is a need for optimized utilization of these resources and to develop new alternative sources of energy to conserve them for future generation. Dual fuel technology is a prominent method to execute for efficient combustion and healthy emission compared with conventional ones. The use of fuel additives in diesel could significantly enhance the fuel properties, promote combustion and reduce harmful emissions. Hydrogen, on the other side, is a clean and carbon free source of energy. Due to its high energy share and availability, it can be utilized in dual fuel engine for optimized emissions and performance. In the present study, tri-ethylene glycol mono methyl ether (TEGMME) as a liquid fuel additive in diesel has been utilized along with hydrogen in dual fuel approach. A four stroke, single cylinder, compression ignition diesel engine was modified to operate in dual fuel mode for the experiments. A fixed speed of the engine was maintained at 1500 rpm was maintained while the compression ratio was fixed to 18. After the experimental trials for the load range of 2–70 %, the results data were analyzed. The effects of the addition of fuel additive and hydrogen on combustion duration were studied. With the substitution of TEGMME in diesel, decrement in combustion duration was observed up to 30 % of load, while combustion duration was increased with increase in load. Hydrogen substitution resulted into increment in combustion duration with increase in load, while with the increment in H2 substitution, reduction in combustion duration at each load was observed. The combined effect of substitution of TEGMME in diesel along with hydrogen was observed for the entire load range. In these cases, minor increment in combustion duration was found at low load, while at high load it was incremented considerably.

Thermodynamic analysis of operating strategies for waste heat recovery of combined heating and power systems

The multi-generation system often operates under off-design conditions due to the highly dynamic energy demand. Improving its off-design performance is crucial for energy conservation and emission reductions. To this end, this paper proposed a novel control strategy for the gas turbine cycle applied in combined heating and power (CHP) system, which effectively combines turbine inlet temperature control (TITC) and inlet air throttling control (IATC) methods, to improve system off-design performance and avoid discharging low-temperature gas. The hybrid control strategy can improve system efficiency by 3.70% on average over the traditional TITC method during the entire load range. Moreover, the maximum efficiency difference between these two methods reached 5.15% at the 30%-load factor conditions. To further showcase the effectiveness of the IAT-TITC method, the CHP system is integrated with an electric chiller and thermal refrigeration, respectively, forming four combined cooling, heating, and power (CCHP) system scenarios to supply the energy for a hotel building. Not only did the CCHP system scenarios with the IAT-TITC method show better performance, but also considering an electric chiller as an extra cooling supply machine can reduce primary energy consumption by 30.73%, 28.32%, and 11.56% in summer, transition season, and winter typical days, respectively, compared with separation system.

Computer modeling of electromechanical system of two-speed elevator

Today, elevator production in Ukraine needs innovative solutions and changes, because most of the equipment in operation was built and installed in the 70-80s of the last century. Due to the high cost of new frequency-controlled winches and the complexity of maintenance, the search for modernization and improvement of existing elevator winches remains an alternative. No less important stage of operation is diagnostics. Timely detection of damages and forecasting of future failures allow to provide high-quality work during all term of operation, and also to reduce expenses of budgetary funds for difficult repairs. Computer simulation playsan important role in the modern world both during the design of a new elevator and during operation. Thanks to fairly simple and clear programs, it is possible to reproduce not only the standard modes of operation of the mechanisms, but also to perform calculations of future possible faults. The use of visualization facilitates the perception of information for operators, engineers and other users involved. The paper presents a computer model of a two-speed elevator with an induction motor and a reduction winch. The research used Matlab / Simulink software, which is intuitive to use and, in the full sense of the word, informative. The built model of the elevator has feedback on the calculated load of the cabin. The latter is determined by the transients during engine start-up and affects the positioning accuracy at a stop. The dependences of the influence of the degree of cab loading on the positioning accuracy are found. In the second stage, the supply voltage parameter is added. A change in this parameter within ± 10% affected the previous calculations of the loading degree and deteriorated the accuracy by almost three times.At the same time, most indicators (75%) meet the requirements of international standards EN 81-20: 2014 with positioning accuracy in the range of ± 10 mm. In further studies it is planned to use the obtained results to reduce the sensitivity of the algorithm for calculating theloadingdegree of the cabin to change the supply voltage and ensure the required positioning accuracy in the entire load range of the cabin when changing the supply voltage ± 10%.

Load-Independent Push–Pull Class E$ ^2$ Topology With Coupled Inductors for MHz-WPT Applications

This article investigates the modeling and implementation of the load-independent operation for the push–pull Class E topology with coupled inductors. The analytical modeling is first presented and provides a new design methodology, which distantly improves the soft-switching performance, load regulation, and efficiency compared with the conventional inductor-coupled Class E topology. An <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC-S</i> resonant Class E <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ ^2$</tex-math></inline-formula> converter, which combines the load-independent inductor-coupled inverter and active rectifier, is proposed for MHz-wireless power transfer (MHz-WPT) applications. The active inductor-coupled Class E rectifier maintains soft switching, constant voltage gain, and zero-phase-angle input at various loads. A three-winding magnetic structure is also proposed to improve the coupled inductors by enhanced self-inductance, which features more effective harmonic suppression with lower magnetic losses and volumes. By the proposed methodology and the improved magnetic structure, the converter features negligible harmonic contents and maintains soft switching with a constant voltage conversion ratio over the entire load range. A 6.78-MHz WPT prototype was built to verify the proposed methodology with detailed parameter design and hardware implementation. The prototype realizes load-independent zero-voltage switching and maintains an approximately constant voltage gain with +5/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 4% variance from no-load to 320-W output power. The measured dc–dc efficiency reaches 89.3% at 210 W.

Tribological properties of anode-spark coatings on aluminum alloys

It is established that at present the technology of anode-spark coatings in general is well studied. However, the lack of recommendations for the choice of modes of technological processes and tribological characteristics in different operating conditions limit the widespread introduction of this technology. The task of this work was to analyze the processes of anode-spark coatings, improve technology and study the wear resistance of samples processed by this and traditional anode technology. The development of technology for the application of protective coatings on valve metals in the conditions of spark discharge included the choice of electrolyte and mode of operation of the bath: voltage, current density, hydrodynamic conditions and other parameters. Wear resistance tests were performed on a special installation. Structurally, the installation is made in two positions, which allows you to test two samples with different load conditions at a constant sliding speed. The design of the installation implements the friction scheme of the liner shaft. The study of anode-spark coatings in the mode of limiting lubrication was studied in the environment of industrial oil. The wear criterion was the weight wear of the samples according to the results of weight measurements before and after wear. It is established that prolonged electrolysis in the conditions of sparking leads to the formation of anode coatings that exceed in their properties the films obtained by non-sparking oxidation. Comparative studies of the wear resistance of anode-spark coatings and galvanic anode coatings under the same test conditions showed that the wear of anode-spark coatings is almost twice lower for the entire load range. The considered technology is recommended for increase of wear resistance of elements of devices from the aluminum alloys working in the conditions of corrosion and mechanical wear

Analysis of Electromagnetic Processes in a Traction Network in Connecting a Reactive Power Compensation and Harmonic Filtering System at a Sectioning Station

To increase the railway capacity, a controlled static reactive power generator is connected at a sectioning station. To reduce the cost indicators of the controlled installation and decrease the power losses, a combined reactive power compensation and harmonic filtering system is proposed, in which the following components are connected in parallel: an uncontrolled bank of shunt capacitive compensation with reduced cost indicators and a static reactive power generator. The total reactive power of the combined system is equal to the specified one. At low traction loads, the static generator operates in the mode of inductive power generation, due to which reactive power is smoothly regulated over the entire load range. Since the existing generator power is reduced by 2-3 times (at the same set power), the total increased power losses are also reduced. For analyzing the electromagnetic processes in the traction network, an electric rolling stock nonlinear model is developed. The article shows how the traction current higher harmonic components are filtered and demonstrates the combined system operability in terms of reactive power compensation under various traction loads by analyzing the waveforms of electromagnetic processes.

Constant and Green Mode Operation Technique in Flyback and Push-Pull DC-DC Converter

Abstract: The high frequency switching causes switching losses and reduces the efficiency of converters. Therefore, operating the DC-DC converters with lower frequencies at light loads reduces the switching losses significantly. Variable frequency switching is generally defined as Green mode operation. The green mode control method is obtained from high efficiency over the entire load range. This method is also called variable frequency control and it changes the switching frequency according to the load condition. At full load conditions, the controller increases the switching frequency to decrease switching ripple and ripple-related conduction loss. When the load decreases, the controller decrease switching frequency to diminish switching loss and increase switch life cycle. In this paper, the flyback and push-pull converter topologies are simulated using MATLAB/Simulink and the results obtained from the variable switching converter are compared with the results obtained from constant switching frequency. Keywords: Green Mode Operation, Flyback Converter, Push-Pull Converter, Variable Switching Frequency, Constant Switching Frequency.

Non-Reacting Spray Characteristics of Gasoline and Diesel With a Heavy-Duty Single-Hole Injector

Gasoline compression ignition (GCI) is a promising combustion technology that could help alleviate the projected demand for diesel in commercial transport while providing a pathway to achieve upcoming CO2 and criteria pollutant regulations for heavy-duty engines. However, relatively high (i.e., diesel-like) injection pressures are needed to enable GCI across the entire load range while maintaining soot emissions benefits and managing heat release rates. There have only been a limited number of previous studies investigating the spray characteristics of light distillates with high-pressure direct-injection hardware under charge gas conditions relevant to heavy-duty applications. The current work aims to address this issue while providing experimental data needed for calibrating spray models used in simulation-led design activities. The non-reacting spray characteristics of two gasoline-like fuels relevant to GCI were studied and compared to ultra-low-sulfur diesel (ULSD). These fuels shared similar physical properties and were thus differentiated based on their research octane number (RON). Although RON60 and RON92 had different reactivities, it was hypothesized that they would exhibit similar non-reacting spray characteristics due to their physical similarities. Experiments were conducted in an optically accessible, constant volume combustion chamber using a single-hole injector representing high-pressure, common-rail fuel systems. Shadowgraph and Mie-scattering techniques were employed to measure the spray dispersion angles and penetration lengths under both non-vaporizing and vaporizing conditions. Gasoline-like fuels exhibited similar or larger non-vaporizing dispersion angle compared to ULSD. All fuels followed a typical correlation based on air-to-fuel density ratio indicating that liquid density is the main governing fuel parameter. Injection pressure had a negligible effect on the dispersion angle. Gasoline-like fuels had slower non-vaporizing penetration rates compared to ULSD, primarily due to their larger dispersion angles. As evidenced by the collapse of data onto a non-dimensional penetration correlation over a wide range of test conditions, all fuels conformed to the expected physical theory governing non-vaporizing sprays. There was no significant trend in the vaporizing dispersion angle with respect to fuel type which remained relatively constant across the entire charge gas temperature range of 800–1200 K. There was also no discernable difference in vapor penetration among the fuels or across charge temperature. The liquid length of gasoline-like fuels was much shorter than ULSD and exhibited no dependence on charge temperature at a given charge gas pressure. This behavior was attributed to gasoline being limited by interphase transport as opposed to mixing or air entrainment rates during its evaporation process. RON92 had a larger non-vaporizing dispersion angle but similar penetration compared to RON60. Although this seems to violate the original similarity hypothesis for these fuels, the analysis was made difficult due to the use of different injector builds for the experiments. However, RON92 did show a slightly larger vapor dispersion angle than RON60 and ULSD. This observation was attributed to nuanced volatility differences between the gasoline-like fuels and indicates that vapor dispersion angle likely relies on a more complex correlation beyond that of only air-to-fuel density ratio. Finally, RON92 showed the same quantitative liquid length and insensitivity to charge gas temperature as RON60.

Regular Sparse NOMA: Ultimate Performance in Closed Form

Understanding the fundamental limits of technologies enabling future wireless communication systems is essential for their efficient state-of-the-art design. A prominent technology of major interest in this framework is non-orthogonal multiple access (NOMA). In this paper, we derive an explicit rigorous <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">closed-form</i> analytical expression for the optimum spectral efficiency, in the large-system limit, of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">regular</i> sparse (code-domain) NOMA, along with a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">closed-form</i> formulation for the limiting spectral density of the underlying input covariance matrix. Sparse NOMA is an attractive and popular instantiation of NOMA, and its ‘regular’ variant corresponds to the case where only a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">fixed and finite</i> number of orthogonal multiple-access resources are allocated to any designated user, and vice versa. Interestingly, the well-known Verdú-Shamai formula for (dense) randomly-spread code-division multiple access (RS-CDMA) turns out to coincide with the limit of the derived expression, when the number of orthogonal resources per user grows large. Furthermore, regular sparse NOMA is rigorously shown to be spectrally more efficient than RS-CDMA (viz. dense NOMA) across the entire system load range. Therefore, regular sparse NOMA may serve as an appealing means for reducing the throughput gap to orthogonal transmission in the underloaded regime, and to the ultimate Cover-Wyner bound for massive access overloaded systems. The spectral efficiency is also derived in closed form for the sub-optimal linear minimum-mean-square-error (LMMSE) receiver, which again extends the corresponding Verdú-Shamai LMMSE formula to the case of regular sparse NOMA.

A Measurement Method of Determining the Power Supply Parameters for the Optimal Operation of a Synchronous Motor

Abstract The article presents a measurement method for determining the power supply parameters for the optimal operation of a synchronous motor, i.e. operation with minimal losses in the entire load range. The measurement strategy is based on the search for the minimum sum of the power supplied to the excitation circuit and the stator circuit for the assumed load torque values. The process of searching for the minimum sum of power can be significantly shortened and simplified by using a network parameter meter. The research confirmed the usefulness of the proposed method for determining the optimal operation parameters of a synchronous motor. The tested motor was a machine with a cylindrical rotor, but the developed method will also be applicable to synchronous machines with salient pole rotors.