Establishment of rational parameters of temperature of working liquid in the hydraulic drive of the excavator of the fourth dimensional group at different equipment

The article considers the hydraulic drive of a modern excavator on which the influence of the working fluid temperature on the power is established, depending on the technical condition of the hydraulic elements. Studies have shown that new pumps and which have operating wear, have different rational temperature of the working fluid. It is impossible to imagine modern construction machines without equipping them with a hydraulic drive. The operation of the hydraulic drive largely determines the efficiency of operation of both a single machine and the entire fleet, which consists of new and old machines . The efficiency of hydrated machines is ensured in their design, manufacture, and operation, where an important role is played by the parameters of the working fluid: the degree of its contamination and temperature (viscosity). The influence of the temperature of the working fluid on the efficiency of the hydraulic drive and the ability to control the efficiency of the hydraulic drive with the help of temperature have not been studied enough. One of the promising areas in determining the rational temperature of the working fluid is the development of new designs of heat exchangers, heaters, diagnostic devices, which will be able to assess the technical condition of individual elements and the hydraulic drive as a whole. Establishing a rational temperature of the working fluid as a necessary parameter of the hydraulic system is mandatory when using modern methods to increase the efficiency of operation, maintenance and repair of hydraulic drives. With increasing temperature of the working fluid, its viscosity decreases and the loss of pressure and power in the mains of the hydraulic drive. However, this increases the internal flow of hydraulic units, which leads to an increase in power loss. Studies have shown that new pumps and which have operational wear, have different rational temperature of the working fluid. At rational values of temperature to the hydraulic motor the worn out pumps can give almost twice more power, than at 50 ° C, recommended for new pumps. The driving power of the pump, thus, practically does not change.

Rapidly Accelerated Synchronous Generators in CAES Systems for Frequency Support in Power Grids

<p>Modern electrical networks are transformed through the use of intermittent sources of energy, such as small-scale photovoltaic installations and wind turbines. By reducing the carbon footprints associated with centralised power grids, they are made more vulnerable to contingent under-frequency events. The renewable energy sources can't provide the required rotational inertia to make the power grid's frequency stable and to be able to assist in restoring the frequency. In New Zealand, Transpower (system operator) is responsible for normalising the frequency in case of contingent events to avoid blackouts in the networks. In case of contingent events in power grids, additional power must be delivered to the networks with the use of primary frequency support systems. Internationally these systems are represented by under loaded power plants, where power output can be adjusted by controlling the primary governor output. This approach incurs no-load running costs and to avoid these costs generation units should be maintained at rest. The most efficient and technically feasible solution is to use synchronous generators that are already present in the power grids or can be additionally delivered to the grids as stand-alone units. However, with the use of the traditional synchronisation method, the generators cannot be synchronised with power grids in a short timeframe (up to 10 s in some countries). To overcome this disadvantage, a novel synchronisation approach should be designed to synchronise synchronous generators from rest of the electrical networks. This thesis proves that it can be achieved by a ballistic synchronisation approach (and then the improved 2-stage ballistic approach), which computes and follows an acceleration trajectory which simultaneously synchronises both phase and frequency. To achieve this fast acceleration a novel environmentally friendly small-scale compressed air energy storage (ss-CAES) system has been designed. This system utilises a hydraulic drivetrain which transmits very high torque directly to the shaft of a synchronous generator, thus enabling its rapid acceleration. The hydraulic drivetrain is composed of a proportional throttle valve and a variable-displacement hydraulic motor. The central controller from National Instruments outputs a voltage that controls the opening of the proportional valve. It changes the flowrate in the main hydraulic circuit, meaning that it is possible to control the output torque and velocity of the hydraulic motor. Since it is coupled to a synchronous generator, the control system can control the dynamics of the drivetrain by changing its voltage output. Computer simulations indicate that this approach enables very rapid synchronisation of a model system to the grid in < 1.5 s at a 100-kW scale. The modelling of the prototype helped to verify the control parameters of the system before the implementation of the algorithm built into the hardware. It should be noted that this model was simulated with the use of the corresponding manufacturer's data. To increase the accuracy of the mathematical model and verify the control parameters, the system components were experimentally characterised with the use of a ubiquitous high-speed data acquisition system. It resulted in a realistic and accurate mathematical model of the complex electro-hydraulic system, despite the well-known challenges of modelling the hydraulic domain. This model was utilised for the tuning of the control parameters of the system before its experimental testing. Experimental runs confirmed the feasibility of the proposed acceleration and synchronisation approach for synchronisation from the rest of the generator in < 4 s.</p>

Rapidly Accelerated Synchronous Generators in CAES Systems for Frequency Support in Power Grids

<p>Modern electrical networks are transformed through the use of intermittent sources of energy, such as small-scale photovoltaic installations and wind turbines. By reducing the carbon footprints associated with centralised power grids, they are made more vulnerable to contingent under-frequency events. The renewable energy sources can't provide the required rotational inertia to make the power grid's frequency stable and to be able to assist in restoring the frequency. In New Zealand, Transpower (system operator) is responsible for normalising the frequency in case of contingent events to avoid blackouts in the networks. In case of contingent events in power grids, additional power must be delivered to the networks with the use of primary frequency support systems. Internationally these systems are represented by under loaded power plants, where power output can be adjusted by controlling the primary governor output. This approach incurs no-load running costs and to avoid these costs generation units should be maintained at rest. The most efficient and technically feasible solution is to use synchronous generators that are already present in the power grids or can be additionally delivered to the grids as stand-alone units. However, with the use of the traditional synchronisation method, the generators cannot be synchronised with power grids in a short timeframe (up to 10 s in some countries). To overcome this disadvantage, a novel synchronisation approach should be designed to synchronise synchronous generators from rest of the electrical networks. This thesis proves that it can be achieved by a ballistic synchronisation approach (and then the improved 2-stage ballistic approach), which computes and follows an acceleration trajectory which simultaneously synchronises both phase and frequency. To achieve this fast acceleration a novel environmentally friendly small-scale compressed air energy storage (ss-CAES) system has been designed. This system utilises a hydraulic drivetrain which transmits very high torque directly to the shaft of a synchronous generator, thus enabling its rapid acceleration. The hydraulic drivetrain is composed of a proportional throttle valve and a variable-displacement hydraulic motor. The central controller from National Instruments outputs a voltage that controls the opening of the proportional valve. It changes the flowrate in the main hydraulic circuit, meaning that it is possible to control the output torque and velocity of the hydraulic motor. Since it is coupled to a synchronous generator, the control system can control the dynamics of the drivetrain by changing its voltage output. Computer simulations indicate that this approach enables very rapid synchronisation of a model system to the grid in < 1.5 s at a 100-kW scale. The modelling of the prototype helped to verify the control parameters of the system before the implementation of the algorithm built into the hardware. It should be noted that this model was simulated with the use of the corresponding manufacturer's data. To increase the accuracy of the mathematical model and verify the control parameters, the system components were experimentally characterised with the use of a ubiquitous high-speed data acquisition system. It resulted in a realistic and accurate mathematical model of the complex electro-hydraulic system, despite the well-known challenges of modelling the hydraulic domain. This model was utilised for the tuning of the control parameters of the system before its experimental testing. Experimental runs confirmed the feasibility of the proposed acceleration and synchronisation approach for synchronisation from the rest of the generator in < 4 s.</p>

The Selection of Hydraulic Cylinder using multi-attribute decision-making methods

A hydraulic cylinder has an important role in the manufacturing industry for producing unidirectional force through the unidirectional direction. Generally, hydraulic cylinders are used where high-pressure applications are required. It is also called a linear hydraulic motor or mechanical actuator. It is manufactured with closer precisions; thus, it involves higher costs and also, it is desired that hydraulic cylinder work as mentioned design. The main purpose of a hydraulic cylinder is to apply force unidirectional with high pressure. The selection of appropriate Hydraulic Cylinders is a critical task for designers. Designers need to find out precise and required properties of it to fulfil industry demand with desired specifications. Different cylinders possess different properties, so by using an optimization tool we can solve such problems. A systematic approach must be used for the selection of hydraulic cylinders. Thus, in current case study work concentrate on the selection methodology for the best Hydraulic cylinder using four different multi-attribute decision-making methods. The decision-making methods help to predict and rank different hydraulic cylinders.

Simulation of a hydraulic drive with volumetric regulation of an amphibious vehicle

The article considers a hydraulic drive designed for the fan transmission, which implements the amphibious vehicle chassis on an air cushion. A mathematical model of the dynamics of the hydraulic rotary drive power section with volumetric regulation has been developed. It is proposed to carry out volumetric regulation by means of a directed change in the working volume of the pump. The dynamics of the output link of the hydraulic drive is calculated when a control signal is applied to change the pump washer angle of inclination. The control signal varied from zero to a signal corresponding to 70% of the maximum, and in the range of 70...100%. The basic and structural diagrams of the hydraulic drive are given; its transient characteristics are obtained when the moment of inertia on the shaft of the hydraulic motor changes when the amphibious vehicle is moving. The simulation study focuses on the change in the moment of inertia on the hydraulic motor shaft under various modes of amphibious vehicle movement. The computational studies of the hydraulic drive determine the time of the transient process and the dynamic error. Computational studies of the hydraulic drive revealed its sufficient performance. The use of the developed mathematical model allows choosing the optimal ratio of the hydraulic drive parameters for an amphibious vehicle.

Design and research of hydraulic conversion system of wave energy generating device

Taking the hydraulic conversion system of the oscillating flapping-wing wave energy power generation device as the research object, a hydraulic conversion system is designed to convert wave energy into usable mechanical energy. Based on the principle of high-efficiency collection of wave energy and stable output of the hydraulic conversion system, the composition of the hydraulic conversion system and the parameters of each component are determined. According to different sea conditions, the pre-charge pressure of the accumulator is adjusted to keep the pressure of the high and low pipelines of the hydraulic system stable, and the mechanical energy is stably output through the hydraulic motor. The AMESim simulation platform is used to build the model of acquisition mechanism and hydraulic conversion system, simulate the motion response of acquisition mechanism under actual sea conditions as the system input, and analyze the effectiveness and output stability of hydraulic conversion system. The results verify that the designed hydraulic conversion system can achieve efficient collection of wave energy. The research results have laid a theoretical foundation for the development and research of wave energy power generation devices.

Displacement prediction and optimization of a non-circular planetary gear hydraulic motor

The non-circular planetary gear hydraulic motor is a low-speed and high-torque hydraulic motor with excellent performance. It has the characteristics of a wide speed range, low weight and is widely used in various fields. Aiming to solve the problem of there being no intuitive formula for calculating the displacement of the non-circular planetary gear hydraulic motor at present, based on the analysis of the effects of structural parameters on the displacement of the motor, this paper proposes a formula for calculating the displacement of a non-circular planetary gear hydraulic motor when the pitch curve of the sun wheel is a high-order ellipse. The formula allows the direct calculation and prediction of the displacement of the motor. To improve the unit volume displacement of the hydraulic motor (which determines the power density of the motor), based on the analysis of the unit volume displacement constraints, an optimization equation is proposed by adding an optimization factor to the original equation of the pitch curve of the sun wheel. It is seen that the addition of the new optimization factor eliminates the self-interlacing of the pitch curve of inner ring gear. This elimination increases the unit volume displacement of the motor.