Search

Pneumatic directional valves are used in most industrial pneumatic systems. Most of them are two-stage valves controlled by a pilot valve. Pilot valves are often chosen randomly. Experimental studies in order to determine the flow-rate characteristics and parameters of pilot valves were not conducted. The paper presents experimental research of two piezo pilot valves.

The article describes research carried out for design and construction of devices stabilizing the working pressure of cement slurry, with use of Deep Soil Mixing technology. The paper presents also the results of numerical calculations showing the flow in the device stabilizing the working pressure of the cement slurry. Flow simulation tests were carried out in the ANSYS program.

The paper presents investigations into pool boiling heat transfer for open microchannel surfaces. The experiments were carried out with saturated FC-72 at atmospheric pressure. Parallel microchannels fabricated by machining were about 0.2 to 0.4 mm wide and 0.2 to 0.5 mm deep. Analyzed surfaces with microchannels allowed to obtain heat transfer coefficients within the range of 6.1 – 9.8 kW/m2K, which in relation to the flat surface gives a 3 – 5 - fold increase in HTC. One of the reasons for the increase in the heat transfer coefficient when increasing the heat flux was the growing number of active nucleation sites at the bottom of microchannels and its side surfaces.

The paper presents the results of numerical calculations showing the temperature distribution of the workpiece (copper) during the face milling process. The ANSYS program was used for simulation studies. The calculations were carried out for two different cutting speeds, examining their influence on the temperature of the workpiece. The calculations constitute the basis for further research in order to determine the influence of variable temperature fields on the thermal expansion of the workpiece and to estimate the dimensional accuracy of the parts to be made during milling.

The paper presents visualization investigations into pool boiling heat transfer for open microchannel surfaces. The experiments were carried out with saturated water, ethanol, FC-72 and Novec-649 at atmospheric pressure. Parallel microchannels fabricated by machining copper sample were about 0.2 to 0.5 mm wide and 0.2 to 0.5 mm deep. The diameter of departing bubble was calculated for the microchannel surface on the basis of buoyancy force and surface tension force balance. The visualization carried out was aimed at determining the diameters of the departing bubbles at various heat fluxes for four working fluids.

A building design of vertical axis wind turbines (VAWT) was presented in the article. The construction and operating principle of a wind turbine were described therein. Two VAWT turbine models were compared, i.a. Darrieus and Lenz2, taking their strengths and weaknesses into consideration. 3D solid models of turbine components were presented with the use of SolidWorks software. Using CFD methods, the air flow on two aerodynamic fins, symmetrical and asymmetrical, at different angles of attack were tested. On the basis of flow simulation conducted in FlowSimulation, an asymmetrical fin was chosen as the one showing greater load bearing capacities. Due to the uncertainty of trouble-free operation of Darrieus turbine on construction elements creating the basis thereof, a 3D model of Lenz2 turbine was constructed, which is more reliable and makes turbine self-start possible. On the basis of the research, components were designed and technical docu mentation was compiled.

This study focuses on the effect of channel depth on the heat transfer coefficient during nucleate pool boiling. Experimental studies were performed for saturated deionized water, and Novec-649 as working fluids at atmospheric pressure. Copper surfaces were modified to form microchannels with different geometrical properties. The microchannels were from 0.2 mm to 0.4 mm deep, 0.3 mm wide and spaced every 0.1 mm. The experiment was conducted for increasing heat flux up to the critical heat flux point. The surface modification provided an appreciably higher heat transfer coefficient compared to the smooth surface for all boiling liquids. The maximum heat transfer coefficient obtained exceeded 60 kW/m2K.

The work includes a study on the comparative analysis of two test methods. The first method - numerical method, consists in determining the flow characteristics with the use of ANSYS CFX. A modeled poppet directional valve 3/2 3D CAD software – SolidWorks was used for this purpose. Based on the solid model that was developed, simulation studies of the air flow through the way valve in the software for computational fluid dynamics Ansys CFX were conducted. The second method - experimental, entailed conducting tests on a specially constructed test stand. The comparison of the test results obtained on the basis of both methods made it possible to determine the cross-correlation. High compatibility of the results confirms the usefulness of the numerical procedures. Thus, they might serve to determine the flow characteristics of directional valves as an alternative to a costly and time-consuming test stand.

This article presents the changes in temperature distribution concerning the processed object during side milling. The analysis included the influence of selected cooling methods (cold air from vortex tube, cooling with compressed air, and without cooling) on the maximum temperature of the processed object during the process of milling. Measurement of the maximum temperature was conducted with the use of thermocouples and a thermal camera.

This thesis presents the outcome of experimental research of the impact of changes in cutting speed and volume of material processed during a face milling process on the temperature of the processed object made of copper of M1Ez4 class. Measurement of the temperature of the processed object was conducted in six points with K-type thermocouples. The theoretical amount of released heat per unit of time for particular parameters of machining was also calculated.

The article concerns experimental studies of the effect of temperature on the positioning accuracy of pneumatic muscles. It presents results of experimental studies in the form of thermal images from thermal imaging camera. Pneumatic artificial muscles have unique operational characteristics and because of that they are used in industrial production processes, where classic drives do not work. During operation of muscles with large frequencies above 60 Hz, one can observe a significant increase in temperatures on the bladder surface. The article concerns a study aimed at the determination of the maximum temperature which can be achieved and whether it affects the accuracy of their positioning.