Transient Operating Modes Research Articles

МАТЕМАТИЧЕСКАЯ МОДЕЛЬ ТОПЛИВНОГО НАСОСА-РЕГУЛЯТОРА ТУРБОВАЛЬНОГО ДВИГАТЕЛЯ ВЕРТОЛЕТА

This article discusses the relevance of creating a mathematical model of a hydromechanical fuel regulator as the main component of the parametric diagnostics method. To understand the processes occurring during the operation of the fuel regulator, this article provides a brief description of its operation. Based on the problems solved by the diagnostic methods and the features of the fuel regulator, the basic requirements for its mathematical model are formulated and the structure of this model is determined. Several assumptions are made (one-dimensional flow of the working fluid and its zero thermal conductivity), which make it possible to significantly simplify the structure of the model and the number of simulated parameters. The mathematical model consists of idealized elements with lumped parameters (such as pressure and flow rate of the working fluid), takes into account the compressibility of the working fluid, as well as the design features of the regulator (mechanical stops, complex profiled dosing windows of spools, relay-type switches). As an example, this article contains equations for the elements with lumped parameters, interconnected by hydraulic channels in one node. The compiled mathematical model is a system of differential-algebraic equations of the first index. To solve such a system, a special implicit solver is used. The calculation of the parameters of the mathematical model for static and transient operating modes of the fuel regulator has been made. The results of calculating the model parameters in various modes are compared with the requirements for these parameters set in the technical specifications for the simulated fuel regulator. The correspondence of the calculated parameters to the values specified in the technical documentation was ensured by the selection of input parameters (tightening of springs of elastic elements, area of throttling elements, etc.). From the results obtained, it was concluded that the model makes it possible to diagnose the technical state of the fuel regulator at the stages of adjustment during production and repair, as well as at the stage of its operation.

Choice of Parameters for the Electrodrive Diagnostic System of Hybrid Vehicle Traction

Abstract When operating a hybrid vehicle (HEV), it is important to reduce maintenance and repair costs. The HEV electric drive (ED) consists of electronic, electrical and mechanical parts and is considered a complex diagnostic model. The availability of an electrical part greatly simplifies the process of monitoring and obtaining information about the state of the system. In order to create a hybrid diesel-electric propulsion system (HDEPS), the choice of structural and functional parameters as diagnostic ones is justified, the control points are chosen, and the necessary accuracy and unambiguity of measurements are determined. Qualitative evaluations of the electrical processes occurring in the power supply circuit of ED from a high-voltage accumulator battery for the selection of diagnostic parameters according to the criteria of sensitivity, informative character, stability and manufacturability of measurements are presented. It has been revealed that during HDEPS diagnostics both stable and transient modes of operation of electric machines should be considered; for analysis of ED technical state it is necessary to have information about current mode of HDEPS load; for measurement of instantaneous values of supply voltage and consumption current it is necessary to select the sensors with short response time and linear conversion function. In terms of sensitivity to structural changes in the circuit and parametric deviations, it is necessary to choose, as diagnostic parameters, the voltage or current, depending on the mode of operation of the ED and the point of measurement of the electrical value. The obtained results are the basis for creating a new system of diagnostics of electric power supply HDEPS in this direction.

Modern Approaches For Modeling Of Structure-Borne Noise Of The Internal Combustion Engine

The article considers the structure of acoustic radiation of an internal combustion engine and modern technologies for noise research. Models of the internal combustion engine as a source of noise and methods for modeling the design and calculating the structure-borne noise of the engine at different stages of its design are described. The method of the engine structure-borne noise calculating for unsteady operation mode is presented. Differences in the working process of the engine for the transient operation mode are shown. Some results of calculations of diesel engine structure-borne noise for different operation modes using MADI methods and using the AVL EXCITE software are presented

Development of a novel rotary flow control valve with an electronic actuator and a pressure compensator valve for a gas turbine engine fuel control system

This paper presents a new rotary proportional flow control valve with Cam-Nozzle configuration. The rotating cam against the fixed nozzle changes the flow area and then can meter the fuel flow. This valve equipped with a pressure compensator plunger type valve to retaining constant pressure difference across the flow control or metering valve. The cam shaft directly coupled to an electronic servomotor type rotary actuator and then it is possible to apply digital control techniques such as pulse width modulation (PWM) in this control system. This new valve configuration is developed for an electro hydro mechanical fuel control system in a gas turbine engine. In addition to aero engine application, this type of flow metering valve can widely be used in industrial hydraulic systems. In this unit, the output flow is proportional to the cam's angular position (or throttle command) and it is not sensitive to pressure fluctuations at nozzle inlet and outlet. The aim of this new design is to modify a manual single adjusted hydro-pneumatic fuel control unit to obtain a new electro-hydraulic fuel control system for a gas turbine engine. The main innovations in the presented fuel metering unit include new design of the rotary valve opening shape (Cam-Nozzle) without metal to metal contact, use of a rotary electronic actuating mechanism and also direct coupling between the actuator and the rotating cam. The increased fuel metering precision in the new flow control valve has improved the ultimate control accuracy of system. A computer simulation software based on the proposed model, is performed to predict the steady state and transient performance and to analyze effect of important design parameters on valve outlet fuel flow and obtain the final design parameters. The validity of the proposed valve configuration is assessed experimentally in the steady state and transient modes of operation. The results show good agreement between simulation and experimental in both modes (max. 4% deviation).

The influence of control laws of frequency-regulated electric motors on electric ships’ maneuvering characteristics

Relevance. In shipbuilding, there have been trends in the use of electric motion. The most important advantages of electric vessels are the high maneuverability, which contributes to the safety of maneuvering operations. Electric propelling power plants (EPPP) are most often built on the basis of asynchronous frequency-controlled electric motors (EM). More and more attention is being paid to electric vessels with a unified electric power system. Electric propelling plant (EPP) is the largest power consumer. The transient modes of its operation significantly affect the parameters of the electric power of the ship network, which raises the requirements for the quality of transient processes in the EPP. On this basis, both the indicators of maneuverability and the quality of electric power of the ship network should be the quality indicators of the control of the EPP on maneuvers. Status of the issue under consideration. Three laws of control of frequency-regulated electric motors are used in the theory of electric motion: at a constant moment; at constant power; at quadratic load. For a real engine, deep frequency control according to one of these laws is not possible, since the motor overload capacity will either be lowered at low frequencies or overestimated in nominal mode. Constant overload capability can only be ensured if there is a variable correlation between voltage and frequency. In the case of frequency control of electric ships’ electric motors, the task becomes more difficult, since a set of indicators characterizing the ship's maneuvering characteristics, transient processes in the EPPP and the parameters of electric power of the ship network should be chosen as the criteria of regulation quality. This leads to the need to clarify the control laws. The purpose of the work is the search for frequency control laws of electric motors that are able to provide better maneuverability of electric vessels. Research results. A structural diagram of EPPP as part of an electric ship’s propulsive complex has been made. A mathematical model of transient operation modes has been worked out on its basis. An algorithm and a package of application programs for calculating the basic mode indices of the complex have been developed. The estimation procedure of the basic indicators of quality of maneuver operation performance is worked out. The model and method of calculation make it possible to study the influence of EM control laws on the electric ships’ maneuvering characteristics, on transient processes in the EPPP and on the parameters of electric power of the ship network. The research was carried out on the example of the science-research vessel MV SANCO STAR. Maneuver modes for various control laws are calculated and the performance indicators of maneuver operations are evaluated. A comparative analysis of the results made it possible to find the best EM control laws on maneuvers. Conclusions. With respect to electric vessels with frequency-controlled electric motors, the proportional control law has significant advantages over other control laws. At the same time, increasing the supply voltage of the EM in transient modes opens the possibility of increasing the efficiency of performing maneuver operations. It is recommended to form the control laws of the EM voltage as analytical dependencies, in which the correlation between the relative voltage and the relative frequency changes gradually depending on the depth of regulation. Specific analytical dependencies are obtained from the results of optimization calculations of control laws.

The study of dynamic processes in the hydraulic system of the roll clamp of a two-cone unwinder rolls pipe-welding unit 159-529

The work is devoted to the study of dynamic loads arising in the hydraulic system of the clamping mechanism of a roll of a two-cone unwinder of rolls of tubes of a pipe-welding unit 159-529. The operating experience of the two-cone unwinder has shown that one of its drawbacks is the unsatisfactory operation of the roll clamp hydraulic system, in which increased dynamic loads are observed. In the hydraulic system of the roll clamping mechanism, the executive hydraulic cylinder is located at a large distance from the pressure source, therefore, it uses long hydraulic lines. In transient modes of operation of a machine with such a hydraulic system, wave processes arise in it (unsteady fluid motion), which affect the quality of its functioning.Based on the analysis of mathematical models used in the practice of dynamic calculations of real hydraulic systems, it is shown that it is advisable to use a system of partial differential equations converted by a finite-difference method into a system as a mathematical model that takes into account the design and operation of the hydraulic system of the roll clamp mechanism of a two-cone unwinder ordinary differential equations with boundary conditions. This makes it possible to create a dynamic model that allows with high reliability to analyze the behavior of the hydraulic system of the mechanism of the clamping roll of a two-cone unwinder. During the implementation of the proposed mathematical model in the Simulink MATLAB software environment, a study was made of the operating modes of the hydraulic system of the roll clamping mechanism. As a result of the study, it was shown that in the hydraulic system of the roll clamping mechanism of a two-cone unwinder, dynamic loads occur at the end of the return stroke, which significantly exceed the permissible values.In order to reduce dynamic loads, a valve operating procedure with a response time of 0.16 seconds is proposed. This allows you to significantly reduce dynamic loads in the hydraulic system of the roll clamping mechanism by reducing the speed of movement of the hydraulic cylinders at the end of the carriage return stroke.

Noise reduction of refrigerant two-phase flow using flow conditioners near the electric expansion valve

Two-phase flow, particularly generated in an expansion device, is a primary cause of refrigerant-induced noise in an air-conditioning system. The indoor unit (IDU) of a multi-split air source heat pump (ASHP) for both heating and cooling must include an electric expansion valve (EEV); therefore, consumers have perceived the increased noise. To reduce this noise, we experimentally investigated the two-phase flow and consequent noise by applying a honeycomb and porous metal as a flow conditioner to the EEV in the IDU of a multi-split ASHP. Flow conditioning near the EEV with the honeycomb and porous metal made the two-phase flow steadier and more uniform, leading to reduced noise and frequency variation for the three heat operation modes of a multi-split ASHP. The noise reduction was also verified in the transient operating modes of a real IDU.

Математическое моделирование процесса функционирования одноцилиндрового дизеля с воздушным охлаждением с учетом расхода картерных газов

At present, the most effective method for studying internal combustion engines (ICE) is mathe-matical modeling and computational experiment. The use of a computational experiment can signif-icantly reduce material and time costs in the research, design and refinement of the internal combus-tion engine. At the same time, despite the high level of the applied mathematical models, there are practically no studies aimed at establishing the regularities of the influence of the state of the cylin-der-piston group (CPG) on the crankcase gas consumption and other indicators of engine operation at steady-state and transient modes. This article is devoted to solving an urgent problem associated with the development of a theoretical base that provides a comprehensive simulation of steady-state and transient modes of diesel engine operation, taking into account the consumption of crankcase gases. The article presents a mathematical model of a diesel engine based on thermal mechanics, which reflects the main features of the engine as a system that converts energy in time. The system of equations of the mathematical model is based on the laws of conservation of energy, mass, equa-tions of motion of solid links and includes differential equations for the rates of change in the tem-perature and density of the working fluid in the cylinder and in the crankcase of the internal com-bustion engine, the ideal gas equation of state, as well as differential equations for the change in the angular speed and angle of motor shaft rotation. The mathematical model is tested on the example of a small-sized single-cylinder diesel engine 1Ch9.5 / 8.0 with air cooling. This type of engine is widely used for small-scale mechanization in agriculture, generator sets, etc. The article presents the results of calculations of a number of engine operating modes in comparison with the results of field tests carried out at the test bench.

СИНТЕЗ ОПТИМАЛЬНОГО НАБЛЮДАТЕЛЯ ПРИ ОТСУТСТВИИ АПРИОРНОЙ ИНФОРМАЦИИ О ХАРАКТЕРИСТИКАХ ШУМА ВОЗМУЩЕНИЯ СИСТЕМЫ АВТОМАТИЧЕСКОГО УПРАВЛЕНИЯ И КОНТРОЛЯ ТУРБОРЕАКТИВНОГО ДВУХКОНТУРНОГО ДВИГАТЕЛЯ

The possibility of obtaining measuring in-formation about the parameters of the automatic control and monitoring system of a turbofan engine during its operation in flight conditions and almost no restrictions on computational costs enable using algo-rithmic methods to improve the engine fault tolerance. In the previous article, the optimal observer, the Kalman filter, was used as a reserve meter. Its functioning essentially depends on the probabilistic characteristics of the system noise, which is known approximately and changes in a complex man-ner over time. Inaccuracies in these characteristics can lead to filter divergence and loss of its stability. To solve this problem, it is proposed to use the Yazvinsky adaptive filter, which allows calculating the covariance matrix of the disturbance noise after the arrival of new measurements from the values of the updated process of the Kaman filter. In this case computational costs increase insignificantly. The use of the Yazvsky adaptive filter eliminates the need for preliminary correlation analysis of system noise and pro-tects the Kalman filter from loss of stability. The results of modeling the Yazvinsky filter, consistent with the mathematical model of the turbofan engine, based on the flight test data of the PS-90A type engine as part of the TU-214 aircraft, both in steady-state and transient modes of engine operation, are presented. The parameters are indicated as percentage of the maximum values. A comparative analysis of the actual errors in the estimation of the output vector of the turbofan engine ACS when Kal-man and Yazvinsky filters are operating is carried out. The results of the comparative analysis are presented in the form of tables and graphs. It is shown that the proposed algorithm ensures fulfillment of the requirements for the accuracy of estimating the output vector of the automatic control and monitoring system of a gas turbine engine and can be recommended for use in the ACS of the turbofan engine.

Applying of IIoT technologies in an automated information system for monitoring and accounting of energy resources

The authors consider the actual task of increasing the scalability and ease of deployment of a distributed automated system for monitoring and metering of energy resources (ASMMER, hereinafter referred to as the System). The system intended for experimental investigation of complex transient modes of operation in high-voltage circuits of power supply systems (up to 25 kV) of the experimental Sverdlovsk Railway (Russian Railways) pilot site. This article proposes a solution using the technologies of the Industrial Internet of Things (IIoT). The protocol stack for the system, that was formed and implemented programmatically, reduces the amount of traffic in the system and supports existing and developing devices with LoRa and XNB technologies. The proposed solutions allowed the development of mobile information-measuring systems using wireless technologies (ZigBee, LoRa, XNB) and independent power sources. The proposed set of solutions allows providing a modular architecture for the rapid addition of new devices and functions through the use of IIoT technologies.

АЛГОРИТМ ЦИФРОВОГО УПРАВЛІННЯ ЕЛЕКТРОПРИВОДОМ АНТЕНИ НАЗЕМНОГО ПУНКТУ КЕРУВАННЯ БЕЗПІЛОТНОГО АВІАЦІЙНОГО КОМПЛЕКСУ

Every year, unmanned aircraft systems are increasingly used in both the civilian and military spheres. Stable communication with an unmanned aerial vehicle is provided by high-precision pointing of the antenna of the ground control point. In the automatic tracking mode of an unmanned aerial vehicle, the antenna guidance is carried out by the automatic tracking system in the direction. It is shown that the main requirement that is put forward in the direction of the auto tracking system is high dynamic accuracy under conditions of disturbances and noises of various kinds. The traditional directional tracking system is not able to provide high precision antenna pointing. It is proposed to improve the quality of the tracking system in both transient and steady-state operating modes by supplementing the existing analog system with a digital correction subsystem. That is why the work is devoted to the synthesis of the digital control algorithm for the electric drive of the antenna of the ground receiving and transmitting station of an unmanned aircraft complex. The digital control algorithm is synthesized as a result of solving difference equations determined by the discrete transfer function of the digital controller. In practice, preference is given to simple controls, the dimension of which is less than the dimension of the object. A simplification of the controller structure was achieved by using a reduced model of the antenna control system in the synthesis process. The reduction is implemented by a method that is based on the proximity of the transition characteristics of mathematical models of initial and reduced control objects covered by a single negative feedback. To assess the degree of proximity, indirect indicators of the quality of the transition process are used. The direct synthesis of the controller is performed by a method that is based on the theory of invariance and provides for the compensation of zeros and poles of the transfer function of the control object. A distinctive feature of the method used is the ability to take into account the stability requirements and the given dynamic accuracy of the control system at the stage of synthesis of the digital controller. The simulation results confirming the efficiency and effectiveness of the synthesized control algorithm are presented.

LINEAR DYNAMIC MATHEMATICAL MODEL AND IDENTIFICATION OF MICRO TURBOJET ENGINE FOR TURBOFAN POWER RATIO CONTROL

Micro turbojets can be used for propulsion of civilian and military aircraft, consequently their investigation and control is essential. Although these power plants exhibit nonlinear behaviour, their control can be based on linearized mathematical models in a narrow neighbourhood of a selected operating point and can be extended by using robust control laws like H∞ or Linear Quadratic Integrating (LQI). The primary aim of the present paper is to develop a novel parametric linear mathematical model based on state space representation for micro turbojet engines and the thrust parameter being Turbofan Power Ratio (TPR). This parameter is used by recent Rolls-Royce commercial turbofan engines but can be applied for single stream turbojet power plants as well, as it has been proven by the authors previously. An additional goal is to perform the identification for a particular type based on measurements of a real engine. This model has been found suitable for automatic control of the selected engine with respect of TPR, this has been validated by simulations conducted in MATLAB® Simulink® environment using acquired data from transient operational modes.

Методика експериментального дослідження визначення динамічних характеристик при русі колісних тракторів з агрегатами змінної маси

Today, an urgent and unresolved issue is the study of transport operations that are used in the agricultural sector, because there is a problem when studying the movement of a machine-tractor unit with trailed or semi-trailer units. This is directly related to the increase in energy saturation of wheeled tractors and, as a result, an attempt to maximize vehicle performance. The study of transport work in the transportation of liquid cargo is of great interest, where an increase in cargo transportation leads to significant instability in the operation of a wheeled tractor and a tractor tank (which is devoid of internal partitions) due to natural vibrations of the liquid. This process leads to longitudinal and lateral instability, contributes to an increase in both dynamic characteristics and emergency situations (there is an effect on the smoothness of movement, vibration load, handling and stability of the vehicle, increasing the dynamic load of the undercarriage, etc.). Therefore, to confirm the theoretical aspects of the influence of fluid oscillations in the tractor tank, experimental studies are necessary. The experimental research methodology presented in this article will allow us to determine the dynamic characteristics during transportation of trailed and semi-trailer tractor tanks during steady-state movement, as well as in transient operation modes. The practical significance of the work is to obtain experimental data on the accelerations of the studied objects at different height filling of the liquid level in the tanks.

Transient phenomena in the draft tube model of a Francis hydro-turbine

This article is devoted to the study of pressure pulsations behind the runner of a hydro turbine model caused by the precessing vortex core (PVC). Pressure pulsations are investigated under conditions of stationary load and transient modes of the hydro-turbine operation. Studies were performed in model conditions on the aerodynamic setup. The map of pressure pulsations was built for stationary modes using acoustic sensors and served to find rotational speeds of the swirler and flow rates at which the PVC occurs. On the basis of the data presented by parametric dependences, the initial and final parameters of the transition process were chosen. In the article, a sudden (fast) transition from part-load regime to the best efficiency point and back was considered. The characteristic times for the formation of PVC and the establishment of the flow regime when changing the controlling parameters of the installation have been determined using a continuous wavelet transform.

Temperature field in gas-cooled reactor core in transient conditions under different approaches to mass flow profiling

Positive effect of profiling the gas-cooled reactor core within the framework of the GT-MHR project was investigated in (Podgorny and Kuzevanov 2017, Kuzevanov and Podgorny 2017, 2018). The necessity arises to supplement already implemented analysis of equilibrium conditions of core operation with investigation of effects of profiling on the temperature field in transient modes of reactor core operation. The present paper is dedicated to the investigation of development of transients in gas-cooled nuclear reactor core subject to the implementation of different principles of core profiling. Investigation of transients in reactor core represents complex problem, solution of which by conducting direct measurements is beyond the resources available to the authors. Besides the above, numerical simulation based on advanced CFD software complexes (ANSYS 2016, 2016a, 2016b, Shaw 1992, Anderson et al. 2009, Petrila and Trif 2005, Mohammadi and Pironneau 1994) is also fairly demanding in terms of required computer resources. The algorithm for calculating temperature fields using the model where the reactor core is represented as the solid medium with gas voids was developed by the authors and the assumption was made that heat transfer due to molecular heat conductivity can be described by thermal conductivity equation written for continuous medium with thermal physics parameters equivalent to respective parameters of porous object in order to get the possibility of obtaining prompt solutions of this type of problems. Computer code for calculating temperature field in gas-cooled reactor in transient operation modes was developed based on the suggested algorithm. Proprietary computation code was verified by comparing the results of numerous calculations with results of CFD-modeling of respective transients in the object imitating the core of gas-cooled nuclear reactor. The advantage of the developed computer code is the possibility of real-time calculation of evolution of conditions in complex configurations of gas-cooled reactor cores with different channel diameters. This allows using the computer code in the calculations of transients in loops of reactor facility as a whole, in particular for developing reactor simulators. Results are provided of calculations of transients for reactor core imitating the core of gas-cooled nuclear reactor within the framework of GT-MHR project performed for different approaches to profiling coolant mass flow. Results of calculations unambiguously indicate the significant difference of temperature regimes during transients in the reactor core with and without profiling and undeniable enhancement of reliability of nuclear reactor (Design of the Reactor Core 2005, International Safeguards 2014, Safety of Nuclear Power Plants 2014) with profiling of coolant mass flow in the reactor core as a whole.

Возможности совершенствования распылительной сушки пищевых суспензий

Spray drying is currently used to obtain powder products from suspensions. It is considered the most effective type of drying for such media. The complexity of the drying process is associated with thermal destruction of components, which degrades the properties of the product and imposes significant restrictions on temperature condition. The present research features the simulation of transient modes of operation of the solenoids to generate a controlled cavitation effect when applied to a stream of acoustic vibrations using a magnetostrictive generator of ultrasound. The authors propose a new design of spray nozzle for drying suspensions with counter-connected solenoids. Such solenoids can cause deformation of the main suspension supply line. The intensity of the cavitation processes depends on the dynamics of the solenoid actuation. The paper introduces a mathematical modeling of transient modes of operation for ultrasonic frequency generator solenoids that create a controlled cavitation effect when applied to the jet of acoustic oscillations of this frequency. When modeling the process of operation of solenoids, the main criterion for changing the intensity of cavitation is the average rate of change in the volume of the cavity at the stage of its collapse, related to one cycle of oscillations for a spherical cavity. An increase in the static pressure of the liquid led to a shift in the phase of the collapse of the cavity. As a result of the chosen mathematical model, a numerical experiment with modeling in the MathCAD program was carried out. It revealed some graphical dependences of the change in U(t), L(t), and R(t). The obtained data allow one to predict the ballast induction and active load (R, L) for the control of transients in the solenoid of the ultrasonic generator. These dependences make it possible to choose more effective parameters for drying suspensions, which is especially important for heat- sensitive components.

District heating system simulation considering consumer and pump operation features

Introduction. The purpose of this investigation is to show what changes introduced in the mathematical model of a district heating system are capable of considerable improving the convergence of simulation results and actual data. The study evaluates the work of heating supply establishments with their customers as well as analysis of the ways of enhancing pump equipment efficiency that allows saving electric energy or increasing output at the same energy consumption. Materials and methods. Engineering acceptance of newly introduced and reconstructed facilities is conducted, heat loads are corrected, disconnections and recurrent connections of indebted consumers are carried out. Studying data submitted by a local heat supply establishment shows that pump seals made from iron and steel are subject accelerated wear in the course of operation. Results. Three variants of the problem solution are suggested: making seals from bronze or stainless steel, prevention of unjustified increase of seal clearances as well as using labyrinth pump seals. This will allow increasing pump equipment efficiency by 5 to 7 % and save about 2 × 105 kW∙h of electrical energy for every pump or increase of output at the same energy consumption. Taking into account that a pump station is a part of the district heating system and unmachined inner surfaces of the pumps have a significant roughness, grinding of these surfaces can improve their hydraulic characteristics of the pumps. In the scope of the suggested method, the entire district heating system is considered not in the situation when actual load is equal to the sum of all the design loads and the pump equipment has manufacturer’s parameters, but accounting actual loads and characteristics. Conclusions. Mathematical model of district heating system heating and hydraulic mode that takes issues mentioned above into consideration would allow simulating joint operation of the heating and hot water supply systems at transient operation modes with higher accuracy.

Influence of ship consumers of electric energy on optimal control of electrical propulsion plants

The urgency of the problem. The most important condition for ensuring the safety of navigation and reducing accidents in the fleet is to take into account the maneuverability of ships, and especially their inertial characteristics. Electric propulsion vessels have the best maneuverability. Special attention is paid to the issues of control of electrical propulsion plants (EPP) of electric ships during maneuvers. Recently, more and more electric ships with a unified electric power system (UEPS) are being built. Both electrical propulsion plant and electricity consumers of electric ships with the UEPS are supplied with power from the general tires of the ship power plant and have a mutual influence on each other. This effect should be taken into account when optimizing the control of the electrical propulsion plant. The status of the issue. Quality indicators of electric ships’ maneuvering were determined and quality indicators of electric energy of the ship network were selected. A method of optimizing the parameters of the control laws of EPP has been developed. The transition to optimal control leads to an increase in the load on the propulsion motors and on the generating units. This may affect the quality indicators of the electric energy of the ship network. The study of this influence is the purpose of this work. The method of solving the problem. A mathematical model of EPP transient modes as part of the ship propulsion complex is used to evaluate the maneuvering characteristics of electric ships. A method of calculating transient modes of operation during maneuvering has been developed on its basis. It is proposed to form the control signals for frequency and voltage in the form of polynomials. A method of optimizing the parameters of control laws has been developed. The results of the study. Effects of load changes on optimal control laws are the following: load decrease slightly affects the optimal solution; with an abrupt increase in the load the stopping distance grows. The optimal parameters of the control laws vary slightly. The impact of the transition from the classical to the optimal control is the following: the quality indicators of the electric energy of the ship network are deteriorating, but are within acceptable limits. Conclusions. The search for optimal control laws of EPP during maneuvering for electric ships with a unified electric power system can be carried out without taking into account the switching on and off of ship consumers. The change of load in the ship network affects the value of the target function but does not affect the optimal parameters of the control laws.

Revisiting the benchmark problem of starting control of combustion engines

Starting of combustion engines is a typical transient operating mode that has significant influence to the engine performance. Due to the distinct variations in the pathes of air intake and fuel injection, the model of the engine system contains considerable uncertain parameters. To search effective control schemes that guarantee desired performance, engine starting control is proposed as a benchmark challenge problem. As a challenging result, a model-based control scheme is developed perviously. In this work, the benchmark problem is revisited and a modification for the fuel injection path control of the previous work is proposed by integrating a time sequence regressive based parameter tuning strategy. Validation by the benchmark problem simulator shows that although the new strategy has simple structure, similar control performance is obtained. Especially, the new strategy has potential extensibility with learning based methods to further improve the performance of the benchmark problem on engine starting control.

On the transient thermal response of thin vapor chamber heat spreaders: Governing mechanisms and performance relative to metal spreaders

Vapor chambers can offer a passive heat spreading solution for thermal management in electronics applications ranging from mobile devices to high-power servers. The steady-state operation and performance of vapor chambers has been extensively explored. However, most electronic devices have inherently transient operational modes. For such applications, it is critical to understand the transient thermal response of vapor chamber heat spreaders and to benchmark their transient performance relative to the known behavior of metal heat spreaders. This study uses a low-cost, 3D, transient semi-analytical transport model to explore the transient thermal behavior of thin vapor chambers. We identify the three key mechanisms that govern the transient thermal response: (1) the total thermal capacity of the vapor chamber governs the rate of increase of the volume-averaged mean temperature; (2) the effective in-plane diffusivity governs the time required for the spatial temperature profile to initially develop; and (3) the effective in-plane conductance of the vapor core governs the range of the spatial temperature variation, and by extension, the steady-state performance. An experiment is conducted using a commercial vapor chamber sample to confirm the governing mechanisms revealed by the transport model; the model accurately predicts the experimental measurements. Lastly, the transient performance of a vapor chamber relative to a copper heat spreader of the same external dimensions is explored as a function of the heat spreader thickness and input power. The mechanisms governing the transient behavior of vapor chambers are used to explain the appearance of key performance thresholds beyond which performance is superior to the copper heat spreader. This work provides a foundation for understanding the benefits and limitations of vapor chambers relative to metal heat spreaders in transient operation and may inform the design of vapor chambers for improved transient performance.