Ballast Load Research Articles

Analysis of Waste Energy Utilization in Ballast Load at Suka Sama Micro Hydro Power Plant

The electrical power generated by a Micro Hydropower Plant (PLTMH) should be fully utilized without any wastage. The PLTMH Suka Sama, equipped with an Electronic Load Controller (ELC), diverts unused electrical power to a ballast load. This action is necessary to maintain system frequency stability in the event of excess power during a drop in demand. The utilization of energy from PLTMH Suka Sama can be improved by using the electrical power diverted to the ballast load to process sugarcane juice into palm sugar using a vacuum evaporator. The potential energy wasted to the ballast load will be calculated based on the comparison data of the power used by the PLTMH and the power wasted during peak and low demand periods over 9 days. The study results show that the power diverted to the ballast load ranges from 2,000 W to over 3,000 W for 4-7 hours per day. This research indicates that the wasted electrical energy can be utilized to produce palm sugar using a vacuum evaporator with a capacity of 2,000 W for 4-5 hours. The wasted energy, if utilized, can produce 2.5 kg to 3.5 kg of palm sugar.

Ballast Settlement Accumulation in Zones with Unsupported Sleepers

The high influence of impact and vibration on the behavior of crushed stone and ballast materials has been known for a long time. The zones with unsupported sleepers, which are always present in transition zones, crossings, welds, etc., are typically characterized by impact interaction, ballast full unloading, and additional preloading. However, no studies on ballast layer settlements consider impact vibration loading. Moreover, the influence of the cyclic loading on the ballast settlement intensity is considered ambiguously, with both decelerating and accelerating trends. The comprehensive literature review presents the influence of factors on settlement intensity. The present study aims to estimate the long-term processes of sleeper settlement accumulation depending on the loading factors: impact, cyclic loading, and preloading. The typical for a void zone ballast loading pattern was determined for various void sizes and the position along the track by using a model of vehicle-track interaction that was validated by experimental measurements. The loading patterns were parametrized with four parameters: maxima of the cyclic loading, impact loading, sleeper acceleration, and minimal preloading. A specially prepared DEM simulation model was used to estimate the ballast settlement intensity after initial settlement stabilization for more than 100 loading patterns of the void zone cases. The settlement simulation results clearly show that even a low-impact loading pattern causes many times increased settlement intensity than ordinary cyclic loading. Moreover, the initial preloading in the neighbor-to-void zones can cause even a decrease in the settlement intensity compared to the full ordinary or partial unloading. A statistical analysis using a machine learning approach and an analytic one was used to create the model for the intensity prediction regarding the loading patterns. The analytic approach demonstrates somewhat lower prediction quality, but it allows to receive plausible and simple analytic equations of the settlement intensity. The results show that the maximal cyclic loading has a nonlinear influence on the settlement intensity that corresponds to the 3–4 power function, and the impact loading is expressed by the linear to parabolic function. The ballast’s minimal preloading contributes to the reduction of the settlement intensity, especially for high cyclic loadings that are typical for neighbor-to-void zones. The results of the present study could be used for the complementing of the present phenomenological equations with the new factors and further application in the algorithms of the settlements accumulation prediction.

Minimizing Voltage Ripple of a DC Microgrid via a Particle-Swarm-Optimization-Based Fuzzy Controller

DC microgrids play a crucial role in both industrial and residential applications. This study focuses on minimizing output voltage ripple in a DC microgrid, including power supply resources, a stochastic load, a ballast load, and a stabilizer. The solar cell serves as the power supply, and the stochastic load represents customer demand, whereas the ballast load includes a load to safeguard the boost circuits against the overvoltage in no-load periods. The stabilizer integrates components such as electrical vehicle batteries for energy storage and controlling long-time ripples, supercapacitors for controlling transient ripples, and an over-voltage discharge mechanism to prevent overcharging in the storage. To optimize the charging and discharging for batteries and supercapacitors, a multi-objective cost function is defined, consisting of two parts—one for ripple minimization and the other for reducing battery usage. The battery charge and discharge are considered in the objective function to limit its usage during transient periods, providing a mechanism to rely on the supercapacitor and protect the battery. Particle swarm optimization is employed to fine-tune the fuzzy membership function. Various operational scenarios are designed to showcase the DC microgrid’s functionality under different conditions, including scenarios where production exceeds and falls below consumption. The study demonstrates the improved performance and efficiency achieved by integrating a PSO-based fuzzy controller to minimize voltage ripple in a DC microgrid and reduce battery wear. Results indicate a 42% enhancement in the integral of absolute error of battery current with our proposed PSO-based fuzzy controller compared to a conventional fuzzy controller and a 78% improvement compared to a PI controller. This translates to a respective reduction in battery activity by 42% and 78%.

Power Quality Control of Micro Hydro Power Plant Based-ELC and VSI Using Fuzzy-PI Controller

Stability of frequency and voltage of micro hydro power plant (MHPP) are influenced by sufficiency of active power and reactive power respectively in handling load power. These powers are normally controlled by Electronic Load Controller (ELC) and Voltage Source Inverter (VSI), respectively. VSI is specifically added to compensate reactive power caused by inductive load. The objective of the study is to control active power and reactive power in MHPP system against the changes in load power through the improvement of ELC and VSI output responses by applying Fuzzy-PI controller. ELC applied Fuzzy-PI controller to obtain more precise TRIAC ignition angle to meet a suitable active power to balance the load power. While VSI implemented Fuzzy-PI controller to meet a precise reactive power needed to oppose inductive load power. Capability of Fuzzy-PI controller in improving ELC and VSI performance were assessed by using Matlab in complete MHPP model. Assessments on the proposed controller indicate that it was effective in improving the performance of both ELC and VSI. By applying Fuzzy-PI controller on ELC, a precise ignition angle of TRIAC stimulated a more precise ballast load to balance active power against the load power. While the addition of Fuzzy-PI controller on VSI produced more suitable reactive power to compensate for the inductive load presence. With a more stable frequency and voltage against changes in load power, the power quality of the MHPP also improve.

Analysis Computational Fluid Dynamics in a State of Ballast Loading on a Passenger Ship Prototype

Indonesia, as the largest archipelagic country in the world, has a very favourable geographical position because it is located between the Indian Ocean and the Pacific Ocean. The background of this research stems from the critical importance of effectively managing ballast loading on passenger ships to ensure stability, safety, and operational efficiency during voyages. Traditionally, methods for assessing ballast loading have often relied on empirical formulas or simplified models, which may not fully capture the complex fluid dynamics and structural interactions inherent in modern ship designs. This gap highlights the need for advanced computational tools like computational fluid dynamics (CFD), which can provide a more detailed and accurate analysis of how ballast loading affects the ship’s behaviour. CFD simulations offer the capability to model and analyse complex flow patterns, pressure distributions, and structural responses under various ballasting scenarios. By leveraging CFD, this research aims to enhance understanding and optimize the management of ballast loading on passenger ships, thereby addressing the limitations of traditional methods and advancing the state-of-the-art in maritime engineering practices. The simulation was carried out at different speeds, namely 1 knot, 10 knots, and 20 knots. When moving at a speed of 1 knot, the obstacles encountered have a range of 30–40 cm/s and a maximum speed of 83.0971 cm/s. Likewise, when moving at a speed of 10 knots, the obstacle has a range of 200–400 cm/s and a maximum speed of 766.921 cm/s. Finally, at a speed of 20 knots, facing obstacles with speeds ranging from 400 to 800 cm/s and a maximum speed of 1504.56 cm/s, the ship’s hull remained unaffected in terms of damage. However, the fluid speed magnifies the occurrence of friction.

Method of calculating the pressure on the soil of wheeled tractors

The market of tractors in Russia has changed greatly in recent years. A number of new suppliers have appeared on the market, abandoned brands are replaced for Russian analogues and machines from friendly countries. It is hard to evaluate all the quantitative and qualitative diversity of tractors provided to agricultural producers through the system of machine tests, especially considering that every manufacturer has a large number of standard size ranges of power equipment. Nevertheless, the customer should have access to information about the basic consumer properties and the degree of effectiveness of a particular machine unit. The article provides a computational method for evaluating one of the most important functional indicators of tractors, namely, the level of impact of its wheels on the soil, using limited initial information: technical characteristics and operational documentation of the manufacturer. The algorithm given in the text was approved during testing real tractor samples. Insignificant differences in the assessment of the maximum pressure on the soil, obtained as a result of measurements and calculations (the difference is 1.9-3.3 %) indicate a high degree of reliability of the developed methodology, as well as the possibility of its application in engineering practice to evaluate the functional indicators of tractors, including taking into account changes in their size and mass parameters when equipped with ballast weights, agricultural machines, implements, dual tires, etc. To make calculations, it is enough to know the weight of the tractor, the weight of ballast loads (mounted implements), the size of the installed tires, their static radius and the amount of tire inflation pressure. The methodology will significantly improve the quality of the predictive assessment of the level of impact on the soil of both mass-produced and designed tractor equipment.

Modeling Railway Track Mechanical Behavior with Under Tie Pads and Under Ballast Mats

Under tie pads (UTPs) and under ballast mats (UBMs) are used in rail track construction to reduce track stiffness and increase the size of the ballast contact area where it meets track support elements either above the ballast (ties) or below the ballast (e.g., subgrade, bridge deck, or tunnel invert). Limited information on the in-track performance of UTPs or UBMs is available. The University of Florida recently completed a research program to monitor track performance and track support changes using a UBM and UTPs in the Virginia Avenue Tunnel in Washington, DC. Researchers measured parameters to estimate the effect of a UBM and UTPs on tunnel invert pressure, tie bottom pressure, and track deflection. A control condition without a UBM or UTPs was not available for testing; however, Volpe developed a finite element track model for estimating track behavior without a UBM or UTPs. The modeling results highlighted the individual contributions of both a UBM and UTPs to stress reduction on the ties and tunnel floor. The model included features that simulate the load chains that can develop in clean granular materials leading to high peak stresses and ballast and structure degradation. The modeling results revealed that a UBM and UTPs might reduce the average stress on the ties and tunnel floor by 5% to 20% when the ballast was well compacted. The peak stresses from ballast load chains, or edges, may be reduced by 50% or more.

Design a prototype of a marine wave power plant (PLTGL) using a recoil starter

As the needs of human life increase, the need for electrical energy will also increase. Currently, fossil energy, which is widely used as fuel for the provision of electrical energy, is running low. In Indonesia, renewable energy sources have not been utilized properly, such as wave energy. This study discussed how to design a prototype of a sea wave power plant. The problem is, how to be able to utilize the energy of sea waves to the maximum. The purpose of this research is to find solutions and designs to utilize recoil starter as a prototype of ocean wave power plants. The methodology used in this study is an experiment in which the prototype made is given a certain treatment and then measurements are made. His data analysis technique is descriptive analysis. Based on the results of measurements and observations, the performance of the tool is not only influenced by the height of the wave, but also the period of arrival of the sea wave and the ballast load of the tool. After measurements were made on the first day of Maruni beach, the prototype could produce an average power of 4.21 watts for an average wave height of 0.35 cm and Maruni beach on the second day could produce an average power of 5.68 watts for an average wave height of 0.4 m. While on the first day Amban beach obtained an average power of 3.29 watts for an average wave height of 0.37 cm and Amban beach on the second day could produce an average power of 14.26 watts for an average wave height of 0.5 m.

РАСЧЕТНОЕ ОБОСНОВАНИЕ ЗНАЧЕНИЙ ПАРАМЕТРОВ, ОПРЕДЕЛЯЮЩИХ ТЯГОВЫЕ СВОЙСТВА ОДНООСНОГО МОБИЛЬНОГО ЭНЕРГЕТИЧЕСКОГО СРЕДСТВА ТОЛКАЮЩЕГО ТИПА

The aim of the work is to study the static parameters of a pushing unit based on a uniaxial mobile power vehicle (UMPV). The article gives the analysis of the influence of the parameters of ballasting and traction load on the reaction of the wheel, the reaction of the support heel of the plow, the weight distribution coefficient, the force on the control handles. Using the MATLAB software, a computer model is implemented that makes it possible to take into account the influence of various parameters of the pushing unit when they change on its static indicators. It is found that in a pushing unit based on the UMPV, a growth in the weight of ballast loads Gб increases the loading of the driving wheels, improving the traction properties of the unit compared to the traction unit based on the UMPV. It is shown that increase in the traction load Rx and the distance aн to agricultural equipment leads to an increase in the load on the driving wheels and control handles, the weight of ballast loads is 0.07...0.35 kN, which is less than that for a traction unit based on UMPV (0.1...0.45 kN).

Towards the effects of load condition on ship manoeuvrability by a system simulation method with hydrodynamic derivatives from RANS computations

The effects of load condition on ship manoeuvrability are investigated by means of system simulation method. To this end, a MMG-type mathematical manoeuvring model is applied to simulate the standard turning and zigzag rudder manoeuvres for a KVLCC2 ship model in six load conditions (two drafts × three trims). In order to determine the needed hydrodynamic derivatives, the forces and moments on the hull in a range of combined static drift and circle motions are computed by using the own expanded RANS (Reynolds-Averaged Navier-Stokes) solver on OpenFOAM. However, the coefficients of hydrodynamic interaction among hull, propeller and rudder are obtained from available experiments. The computed surge forces, sway forces and yaw moments agree fairly well with the experimental data, suggesting a promising prospect for the used RANS solver in the application of ship manoeuvring prediction. By regressing the hydrodynamic forces and moments, the hydrodynamic derivatives are obtained. Turning and zigzag rudder manoeuvres are simulated by solving ship motion equations in line with the acquired derivatives and coefficients. Comparing the simulated results between the full and ballast load condition without trim, a small draft (i.e. the ballast load condition) improves turning performance, but weaken course stability. For the three full load conditions or ballast load conditions, trim by bow improves turning ability, but deteriorates yaw-checking ability. The simulated results for two load conditions show satisfactory agreement with available experimental data, which suggests that the present procedure for ship manoeuvring prediction is effective. The course stability indexes are analysed as well. The load condition will affect significantly the manoeuvrability of a ship, at least for KVLCC2. It may be quite necessary to evaluate the manoeuvrability of a ship in different load conditions at the initial design stage.

NUMERICAL INVESTIGATIONS ON THE FREE SURFACE FLOW AROUND WING-BODY JUNCTIONS

Starting with January 2013, all ships greater than 400 tons engaged in international voyages must comply with the Energy Efficiency Design Index (EEDI), and starting with January 2023 also with the Efficiency Existing Ship Index (EEXI), issued by the International Maritime Organization, (IMO). Knowing that, in general, a ship hull is the result of a compromise between the main dimensions imposed by the size of the locks, navigation route depth, port depth, taxes, transport capacity (deadweight, volume), ship equipment (machinery, deck installations, piping systems), hydrostatic performances and last but not least the hydrodynamic performances, from ship hydrodynamics point of view the available approaches are the optimization of the ship size and hull forms or the design of propellers adapted to the ship's wake. The main purpose is to reduce the ship resistance and increase the efficiency of the propulsion system which ultimately leads to a reduction in the power placed on board the ship. For this, there can be used the so-called flow control devices or Energy Saving Devices (ESD hereafter), as hydrofoils or nozzles, to improve the flow parameters entering the propeller disc in order to increase the efficiency of the propulsion system and decreasing the fuel consumption leading to reducing of the carbon and greenhouse gasses emissions. For ballast loading condition the ESD may intersect the free surface, the flow becoming complicated and combining nonlinear, three-dimensional and turbulent phenomena such as the boundary layer on solid surfaces, the horseshoe vortex system developed around junctions and their effects turbulence, and also wave breaking. Therefore, this paper presents the results of the numerical study on the viscous free surface flow around junctions between a hydrofoil mounted on a plate, more precisely the study of the influence of the angle between hydrofoil and plate. It was observed that from a hydrodynamic point of view the angle between hydrofoil and base plate to be less than 15 degrees in respect to the vertical direction on the hydrofoil so that horseshoe vortex to be reduced in intensity and the value of the hydrofoil drag to be minimal.

Collision-accidental limit states-based safety studies for a LNG-fuelled containership

Liquefied natural gas (LNG) is an increasingly popular fuel alternative of ships for reducing greenhouse gas emissions. The interest in LNG fuel propulsion systems is rapidly growing, yet certain important safety design and engineering issues remain poorly constrained. The safety of LNG-fuelled ships must be assessed in terms of the potential structural damage owing to collision accidents and resulting LNG spills, especially for ship types that store the LNG storage tank within the cargo hold. In this paper, accidental limit state (ALS) based safety assessment for LNG-fuelled containership structures using nonlinear finite element methods is studied at the most unfavourable scenario of collisions between a striking ship's bow and a struck ship's LNG fuel tank, where the struck ship is in full load condition at a standstill, while the striking ship of the same size as the struck ship has different loading conditions in the ballast load condition, 50% partial load condition and full load condition, with varying collision speed at 0.5, 3, 6 and 9 knots. A hypothetical 9,000 TEU (Twenty-foot Equivalent Unit) LNG-fuelled containership was designed in accordance with the requirements for the international gas fuel transport standards, accommodating a membrane-type LNG fuel tank located amidship. It is found from the present study that inner side hull structures of the struck ship can be damaged in ship-ship collisions, and the current industrial guidelines for LNG fuel tank designs are required to amend to apply for LNG-fuelled ships.

An Efficient Numerical Model to Predict the Mechanical Response of a Railway Track in the Low-Frequency Range

With railway interoperability, new trains are allowed to move on the French railway network. These trains may present different designs from standard trains. This work aims to complete the current approach for vehicle admission on the railway network, which is defined in technical baselines. Historically, computation rules for traffic conditions are based on simplified analytical works, which are considerably qualitative. They have evolved through feedback and experimental campaigns to comply with the track structure evolution. An efficient methodology based on numerical simulation is needed to evaluate railway vehicle admission to answer this issue. A perspective to update these computation rules is to evaluate the structural fatigue in the rail. That is to say, fatigue is caused by bending and shear stresses. The complexity of the railway system has led to an investigation at first of the vertical response of the railway track and quantifying its contribution to the rail’s stress response. In that sense, this paper investigates the vertical track response to a moving railway vehicle at low frequencies. For this purpose, a lightweight numerical model for the track, a multi-body model for the vehicle, and a random vertical track irregularity are proposed. More explicitly, the track model consists of a two-layer discrete support model in which the rail is considered as a beam and sleepers are point masses. The rail pads and ballast layer are modelled as spring/damper couples. Numerical results show a negligible effect of track inertia forces due to high track stiffness and damping. Nevertheless, this assumption is valid for normal rail stresses but not for ballast loading, especially in the case of sleeper voids or unsupported sleepers. Hence, the prediction of the mechanical stress state in the rail for fatigue issues is achieved through a static track model where the equivalent loading is obtained from a dynamic study of a simplified vehicle model. A statistical analysis shows that the variability of the vertical track irregularity does not influence the output variabilities like the maximum in time and space of the normal and shear stress.

Analysis Of The Installation Of Subsea Pipelines To Support The Need For Clean Water In Supporting Tourism Development On Kayangan Island

Inclusive access to water is very important for the tourism sector to maintain a good reputation among tourists and the social license of the local community to operate. While all stakeholders or stakeholders expect the success of tourism which contributes to economic improvement, community welfare, human resource development, and improvement of public health and the environment, tourism activities on Kayangan Island need clean water for their development. Considering that the island is one of the favourite tourist destinations and is growing quite rapidly at this time, there is no effective source of clean water available on the island. Therefore, it can be attempted to provide clean water by using subsea pipes sourced from PDAM Makassar. According to observations from various aspects, the pipe will cross the ocean with a span of ±1500 meters by flowing water with a discharge of 10 lt/s using HDPE pipes with a diameter of 140mm PE100, PN 16 according to SNI standards. For a fairly good security system, the jet pump and the pipe will be tied to a 110 mm diameter stainless steel sling bridge. In addition, at every 6 meters distance, the pipe bridge slings are fitted with ballast loads with hanging slings. In this study, the installation of subsea pipelines requires a variety of supporting equipment and also a complicated implementation, but it is can be carried out considering this needs to be done to support the need for clean water on Kayangan Island to support tourism development.

Analysis Of The Installation Of Subsea Pipelines To Support The Need For Clean Water In Supporting Tourism Development On Kayangan Island

Inclusive access to water is very important for the tourism sector to maintain a good reputation among tourists and the social license of the local community to operate. While all stakeholders or stakeholders expect the success of tourism which contributes to economic improvement, community welfare, human resource development, and improvement of public health and the environment, tourism activities on Kayangan Island need clean water for their development. Considering that the island is one of the favourite tourist destinations and is growing quite rapidly at this time, there is no effective source of clean water available on the island. Therefore, it can be attempted to provide clean water by using subsea pipes sourced from PDAM Makassar. According to observations from various aspects, the pipe will cross the ocean with a span of ±1500 meters by flowing water with a discharge of 10 lt/s using HDPE pipes with a diameter of 140mm PE100, PN 16 according to SNI standards. For a fairly good security system, the jet pump and the pipe will be tied to a 110 mm diameter stainless steel sling bridge. In addition, at every 6 meters distance, the pipe bridge slings are fitted with ballast loads with hanging slings. In this study, the installation of subsea pipelines requires a variety of supporting equipment and also a complicated implementation, but it is can be carried out considering this needs to be done to support the need for clean water on Kayangan Island to support tourism development.

Ballast loading plate design and mechanical behavior of under ballast mats

Geometry of loading plate which simulates the ballast contacting interaction is the critical factor for mechanical properties and durability test of the geotextile for railway track. In this study, a ballast indentation test with 3D laser scanning method was performed to study the actual contact characteristics of the bottom of the ballast. Based on this, the existing problems of geometric-ballast-plate (GBP) of the EN standard were presented. Therefore, a new ballast loading plate, Actual Ballast Plate (ABP), was designed and verified. The mechanical behavior of under ballast mats (UBMs) with different stiffnesses were studied by applying different ballast loading plates (the ABP, GBP, and flat plate). Results demonstrated that for the GBP, the geometric characteristics of sharp corners at the bottom of the ballast were largely overlooked, resulting in smaller contact stress in the fatigue test. The ABP resulted in a better simulation of the contact characteristics and load transfer relationship of the ballast. The stiffness test with the flat plate (FP) and GBP resulted in a higher static modulus for the hard UBM because of the overestimation of the contact area between the UBM and the ballast. It is recommended that the EN standards adopt the ABP to replace the GBP for the fatigue tests of the UBMs.

Fatigue Crack Growth Evaluation of IMO Type B Spherical LNG Cargo Tank Considering the Effect of Stress Ratio and Load History

The crack propagation on a spherical IMO Type B LNG tank deployed on a 150K class LNG carrier is studied. IMO Type B tanks require a high level of safety . Therefore, analyses such as strength evaluation, fatigue analysis, fatigue crack propagation analysis, and LNG leak rate should be conducted to ensure safety. Various fatigue crack growth models were proposed for fatigue crack propagation analysis. The Forman model and the Walker model consider the stress ratio. Furthermore, the Huang model, and the Lee and Kim model consider the stress ratio and the effects of overload and underload present in the past load history on crack propagation.To examine the effects of stress ratio and load history for the fatigue crack propagation models, the crack growth of the LNG tank was evaluated by considering the stresses under full load and ballast load operating conditions, and three stress amplitude sequence cases.

Electronic Load Controller based on Dimmer Circuit and Stepper Motor for 5 kW Micro-Hydro Power Plant

This paper presents the results of research on a new schematic generator load controller simulation, namely an electronic load controller based on a dimmer circuit and a stepper motor for a small-scale 5 kW micro-hydro. The load controller is built from a dimmer circuit and a stepper motor with program control using Matlab software, and the PPI 8255 interface device. Using a dimmer circuit built from diac, triac, a variable resistor (pot), and capacitor components. As well as using a 28BYJ-48 stepper motor. Simulation is made to determine the performance of the load controller in controlling the distribution of power to the ballast load when the generator supplies power to consumers less than the full load of the generator. By using the simulation data of 45 variations of the consumer load sample, the result is that there are only 4 samples where the load controller is not working well. For the 4 samples, the generator was loaded beyond its full load tolerance limit (full load tolerance of 5kW ± 5 %). Overall, based on the simulation results, it can be said that the generator load controllers tested in this study have good performance.
 HIGHLIGHTS
 
 Methods and power electronic configurations used in electronic load controllers for micro-hydropower plants from 1980 until now. In the future, the use of low-power micro hydro and pico hydro power plants is also in great demand, especially for rural areas
 The utilization of micro-hydro in Indonesia, especially low-power micro-hydro, has been utilized by the community in Bulukumba Regency, South Sulawesi Province. A 5 kW generator has been operated in Katimbang Village, Borong Rappoa District, Kindang Regency, Bulukumba Regency, South Sulawesi Province to distribute electrical energy to 15 households
 This research proposes a new electronic load control scheme for a simple and inexpensive 5 kW micro-hydro power plant, namely a dimmer circuit and stepper motor-based generator load controller. With the consideration that the main components that make up this controller are not expensive
 
 GRAPHICAL ABSTRACT

BALLASTING AS THE WAY OF IMPROVING THE OPERATIONAL PROPERTIES OF THE TRACTOR

Since the invention of the tractor, its operational properties have been improved. As engine power increased, researchers, manufacturers and consumers looked for various ways to maximize the use of the effective power of the engine. Such methods are an increase in operational weight due to filling tires with liquid; the use of mechanical and hydraulic rear wheel loaders, agricultural machines on the front hitch and ballast loads. (Research purpose) The research purpose is to determine the limits of energy saturation of tractors of leading foreign manufacturers, to analyze the approach of foreign companies to the design of operational properties of tractors, to study, within the limits of energy saturation, the relationship between the operational mass of the tractor and the mass of the ballast cargo, to establish the optimal loading in order to maximize the operational properties for tractors of various classes. (Materials and methods) The article presents the research of domestic scientists studying the boundaries of energy saturation, manuals for the operation of tractors of leading foreign firms, tractors of the Belarus family, agricultural machinery. Authors applied the following methods: comparison, forecasting, economic and mathematical modeling, expert assessments and others. (Results and discussion) The article presents the energy saturation of 165 foreign agricultural tractors in 18 engine power ranges from 72 horsepower (53 kilowatts) to 628 horsepower (462 kilowatts) with a tractor weight from 3,400 to 29,940 kilograms. According to the energy saturation data, the limits of the energy saturation of tractors in different ranges of engine power and from different manufacturers were presented. The article presents the optimal loading options for maximizing the operational properties of tractors. (Conclusions) Based on the calculations of productivity and the effect of ballasting on productivity, the optimal option of loading was described.

Numerical investigations of the free surface flow around a surface piercing hydrofoil

Starting with January 2013, naval architects faces new challenges, as all ships greater than 400 tons must comply with energy efficiency index (MPEC 62, 2011). From ship hydrodynamics point of view one handy solution is using Energy Saving Devices (ESD), with the main purpose to improve the flow parameters entering the propeller. For ballast loading condition the ESD may intersect the free surface disturbing and complicating the flow due to free surface /boundary layer interaction, turbulence and breaking wave effects that coexist and which are not completely clarified so far. Therefore, a free surface flow around a NACA 0012 surface piercing hydrofoil is numerically investigated and the results are compared to experimental results obtained in the Towing Tank of the Naval Architecture Faculty, “Dunarea de Jos” University of Galati. The comparison includes drag and free surface elevation on hydrofoil surface together with numerical uncertainty.