This paper deals with the analysis of leakage characteristics of the proportional directional valve. These characteristics distinguish a real directional valve from an ideal one. The ideal directional valve is characterized by zero leakage due to its perfect geometry. The investigated element is the three-position four-way proportional directional valve with zero spool lap and feedback from the spool position. The spool position is measured by the inductive position sensor and processed by external electronics. Internal leakage occurs due to axial and radial clearances between the spool and the sleeve. The magnitude of axial clearances that occur at throttle edges and their effect on the directional valve leakage is the subject of research. The blocked-line pressure sensitivity curve, the leakage flow curve and the center flow curve are determined by experiment. Individual characteristics are determined for different working fluid temperatures and different supply pressures. The flow through internal leaks in the center position of the valve spool is determined by analytical calculations. The flow through internal leaks is also simulated using the Ansys Fluent software. Subsequently, the geometry of the flow simulation model is modified to take into account manufacturing tolerances. From simulation results, the effect of the manufacturing tolerance magnitude on the internal leakage of the directional valve is evaluated. Finally, simulated dependencies are compared with experimentally determined characteristics.

This paper deals with the experimental and numerical analysis of the flow force acting on the spool of a proportional directional valve. The flow force arises due to the fluid flow through the flow path of the proportional directional valve and significantly influences the dynamics of the valve spool. The valve under investigation is a three-position four-way proportional directional valve with zero spool lap and feedback from the spool position. The dependence of the valve spool flow force on the volumetric flow rate is measured as part of the experiment. The measurements are performed for different spool displacements. The measured data will be used to verify the numerical simulations. The proportional directional valve was modified so that a force sensor could be included on the spool axis to realize the experiment. Firstly, the flow force is measured as the fluid passes through the two flow paths of the valve (PB and AT). Subsequently, the experimental setup is modified to determine the flow force when the fluid passes through each flow path separately. The measurements are compared. Simulations of the flow through the proportional directional valve are performed using Ansys Fluent 2022 R2 software to determine the flow forces acting on the valve spool. Simulations are performed for the selected spool positions of the proportional directional valve. Finally, the results of the simulation and the experiment are compared. The contribution of this study is a CFD model of the flow paths of the proportional directional valve verified by experiment. The CFD model will allow the flow force analysis for different flow path geometries of the investigated valve. Experimental analysis of flow force is performed over the entire spool stroke at different volumetric flow rates. The flow forces are measured for each flow path separately and for both flow paths simultaneously.

Fluidic muscles have been the subject of research since the 1930s to the present day. McKibben's muscle is one of the most common ones. This type is the basis for fluidic muscles already being used commercially. The power-to-weight ratio is one of their main advantages. The disadvantage is difficult handling. The article describes experimental verification of static characteristics of fluidic muscles. During muscle contraction, a tensile force is developed which changes as the length of the muscle changes. This dependence is experimentally verified. A measuring equipment for testing fluidic muscles of various lengths and diameters is designed and assembled. The device consists of a pneumatic circuit, where the output drive is a loaded fluidic muscle. The load of muscle is generated by a hydraulic cylinder. The results will be further applicable to fluidic muscle simulations.

This paper deals with the experimental analysis of the effect of the braid angle on the behaviour of a hydraulic hose under pressure loading. The main structural elements of the hose are a rubber tube and a steel braid or spiral. The material of the braid and the number of braids influence the magnitude of the pressure load on the hydraulic hose. The angle of the braid affects the deformation of the hydraulic hose when the inner wall is loaded with fluid pressure. For hydraulic hoses, it is a requirement to maintain a neutral braid angle during manufacture to ensure a balance between axial and circumferential stresses under pressure loading. An experimental device was set up to measure the hoses. This device can be used to measure the diameter of the outer braid, the length and the tensile force of the hose in the axial direction and, where appropriate, to evaluate the angle of the outer braid of the hose as a function of the fluid pressure loading on the inner wall of the hose. The object of the research is to determine the effect of the braid angle on the behaviour of the hydraulic hose under pressure loading. Based on the measurements, the dependencies of the tensile force, the braid angle and the change in length of hydraulic hoses on the internal pressure were determined. In order to compare the measurement results, hydraulic hoses with different inner diameters and different numbers of braids or spirals were selected.Research background: Description of neutral braid angle, hydraulic hose geometry, tensile force of hose.Purpose of the article: Influence of braid angle on the hydraulic hoses behaviour under pressure loading.Methods: Experimental measurements.Findings & Value added: Determining of the change of length dependencies on the pressure, determining of the tensile force dependencies on the pressure.

Hydraulic hoses are part of most hydraulic systems, from industrial hydraulics with open loop hydraulic systems to mobile hydraulics with closed loop hydraulic systems. The design parameters of hydraulic hoses may influence the duty cycle dynamics of these systems. One of the factors that influence the behavior of a hydraulic hose under pressure loading is the steel braid angle with respect to the hydraulic hose axis. This work aims to determine the effect of the hydraulic hose braid angle on the change in its geometry. The next objective is to determine the forces that occur at the hose ends under pressure loading. The stresses occur when fluid pressure is applied to the inner wall of the hydraulic hose. Consequently, these stresses are transferred to the hose ends through the steel braid or spiral. The phenomenon of the neutral braid angle provides a balance between the stresses generated inside the hydraulic hose. Therefore, hydraulic hose manufacturers try to produce hydraulic hoses with a neutral braid angle, because the lifetime of the hydraulic hose is also related to this. As part of this research work, an experimental device was constructed in order to measuring the properties of hydraulic hoses. When the hose was loaded with fluid pressure, the change in hose geometry was measured and the angle of the hose braid was measured simultaneously. Upon the measurements, the effect of the braid angle on the hose behavior under pressure loading was determined.

This paper covers with experimental measurement and mathematical simulation of parallel capacitance influence on pressure response for non-stationary flow. The hydraulic circuit for measuring required quantities, which are necessary to determine of parallel capacitance influence on the hydraulic system dynamics. A part of hydraulic system is a long pipe, in which the parallel capacitance created by hydraulic hose is connected. A non-stationary flow is caused by fast closing of the seat valve, which is situated at the end of long pipe. Mathematical model is realized and verified in Matlab SimScape Fluids software for this hydraulic system.