Defining the rational installation position for the discharging unit of the bucketless rotary imple-ment in the trenching excavator

The increasing volumes of the earthworks performed by trenching excavators during the creation of the lengthy excavations in the soil for the pipelines of different sizes and other purposes create the need to improve the excavators, to create new highly productive machines of the fundamentally new construction. The goal of this work is to increase the performance of trenching excavators equipped with the bucketless rotary implement by improving the process of the soil discharging from the implement. To achieve this goal it is required to reveal the physical essence of the soil excavation by the bucketless rotary implement and based on the performed study to determine the rational installation position for the discharging unit of the bucketless rotor. Methodology. The scientific hypothesis is that discharging of the inner circular cavities of the bucketless rotor during the trench digging and the movement of the excavated soil to the side from the trench is possible by means of rational use of the flow header pressure of the soil that is being transported in the rotor from the excavation. The study is performed with analytical methods using basic principles of the theoretical mechanics, flowing medium statics, force analysis. Results. The study confirms the scientific hypothesis of the possibility to discharge the bucketless rotary implements of the trenching excavators by using the flow header pressure of the excavated soil that is transported by the rotor from the excavation, rational installation position of the discharging unit of the implement is defined. Originality. The scientific novelty of the study lays in the rationale and confirmation of the possi-bility to excavate and transport the soil from the excavation with the implements of the rotary trenching excavators with continuous flow and not with the separate portions. Practical value. Practical value lays in ensuring the 2-5 times performance increase of the excavation using the bucketless rotary implements.

Data Acquisition System for Chemical Iodine Generation Suitable for Flowing Medium Chemical Oxygen Iodine Laser

Development of infrared flowing medium lasers needs to be envisaged in a manner that practical aspects such as system compactness, short readiness time, low system size, weight and power are met to make them field deployable. In this context, the critical aspect of in-situ production of lasing species (Iodine) in Chemical Oxygen Iodine Lasers (COIL), one of the most potent flowing medium lasers, has been investigated. The paper dwells on chemical generation of iodine and its precise flow and parameter control by implementing a customised Data Acquisition System (DAS). Iodine is generated in a chemical reaction of Cuprous Iodide (CuI) with chlorine. This is achieved by precisely controlled flow of chlorine diluted with a carrier gas (N2 ) in a ratio of 1:2. DAS includes regulated gas feed, accurate thermal stabilisation, relevant diagnostics and implementation of necessary safety interlocks in a real time operation scenario for establishing the system efficacy and scalability. The studies have demonstrated chemically generated iodine flow rate of ~ 1.2 mmol.s-1 for Cl2 flow rate of ~3 mmol.s-1 all measured in real time using the developed DAS with a conversion efficiency of 80%. Developed I2 supply system has potential to deliver iodine on demand with required flow rates, measurement uncertainty of ~ 4.5 percent and advantages of smaller specific weight and size with reduced system readiness time and electrical power supply using DAS system with adequate safety interlocks.

Energy and Exergy Analyses of a Flat Plate Solar Collector Using Various Nanofluids: An Analytical Approach

Energy and exergy (EnE) efficiencies are considered the most important parameters to compare the performance of various thermal systems. In this paper, an analysis was carried out for EnE efficiencies of a flat plate solar collector (FPSC) using four different kinds of nanofluids as flowing mediums, namely, Al2O3/water, MgO/water, TiO2/water, and CuO/water, and compared with water as a flowing medium (traditional base fluid). The analysis considered nanofluids made of nanomaterials’ volume fractions of 1–4% with water. The volume flow rates of nanofluids and water were 1 to 4 L/min. The solar collector′s highest EnE efficiency values were obtained for CuO/water nanofluid among the four types of nanofluids mentioned above. The EnE efficiencies of the CuO nanofluid-operated solar collector were 38.21% and 34.06%, respectively, which is significantly higher than that of water-operated solar collectors. For the same volume flow rate, the mass flow rate was found to be 15.95% higher than water for the CuO nanofluid. The EnE efficiency of FPSC can also be increased by increasing the density and reducing the specific heat of the flowing medium.

Micropolar Flow Over a Black Isothermal Plate in the Presence Thermal Radiation

This study numerically investigates the effects of thermal radiation on the flow over a black isothermal plate for an optically thin gray micropolar fluid. The flowing medium absorbs and emits radiation, but scattering is not included. The computational results are discussed graphically for several selected flow parameters.

Thermal radiation and magnetohydrodynamics flow over a black isothermal plate

We study the effects of the thermal radiation and an induced magnetic field on the flow over a black isothermal plate for an optically thin gray fluid. The flowing medium absorbs and emit radiation, but scattering is not included. Numerical solutions are obtained for different values of radiation parameter, Prandtl number, Grashof number and magnetic Prandtl number.

Evaluation of the Characteristics of the Control Valves

When designing pipeline networks, the knowledge of loss coefficient respectively resistance coefficient when flowing through various types of fluids through hydraulic elements, e.g. control valves, which are often used in the engineering and energy industry. Their specification is performed mainly experimentally. However, there are applications where the experimental approach of their determination is unrealistic and then mathematical methods can be considered. The article presents a methodology for determining the static characteristics of the DN25 control valve for different opening. The measurement of the characteristics was performed with an incompressible flowing medium - water and with a compressible flowing medium - air. Subsequently, a comparison of measurement and evaluation of loss and flow coefficients was performed. The measured values will be further used to verify the results of modelling and to precisely define mathematical models, so that the models can be subsequently used at vapour flow, where the experimental method of determination is difficult. Frequent applications are found in the flow of saturated and superheated vapour through control valves.

Dewatering of foam-laid and water-laid structures and the formed web properties

The use of aqueous foams as a carrier fluid for pulp fibers instead of water has re-emerged in the paper and board industry in recent years. In foam forming, a surfactant is needed to reduce the surface tension of the carrier liquid and to create foam as a process fluid and flowing medium. This presents the following questions: (1) How do the water forming and foam forming processes differ? (2) How do the obtained wet/dry fibre sheets differ after forming and after wet pressing? (3) Which differences in the process behavior and sheet properties are due to the surfactant, and which are due to the presence of air bubbles in the flowing medium? The answers to these questions were sought by using an experimental academic approach and by applying a special dynamic vacuum assisted sheet former. Although foams are much more viscous than water, dewatering times were found to be approximately equal in water and foam forming at higher vacuum levels. The hydrodynamic resistance of sheet was approximately constant during water forming, while in foam forming resistance was initially even smaller than in water forming but it increased with time, being substantially higher at the end of the forming process. In certain cases, surfactant alone was found to have a similar, albeit often lower, effect on the sheet properties of foam. Surfactant improved sheet dryness (both after forming and wet pressing), lowered density, and lowered strength properties also in water forming. Foam, on the other hand, had a crucial effect particularly on certain structural properties such as formation and porosity. The difference between water and foam-laid sheets typically reduced in line with higher wet pressing pressure. This suggests that the role of surface tension and foam bubbles in controlling interfiber contact is overridden by wet pressing pressure. Thus applying foam as a carrier fluid has characteristic effects both on the papermaking process and the end product properties. The main features of foam forming can be explained by the chemical effects caused by the surfactant, and the structural effects caused by the foam bubbles. Graphic abstract