Results of the theoretical and experimental investigations of the turbulent mean swirl flows characteristics change along straight conical diffuser of incompressible fluid (air) are presented in this paper. The main swirl flow characteristics review is given. In addition: the specific swirl flow energy, the energy loss, the mean circulation, the swirl flow parameter, the ratio between the swirl and axial flow loss coefficients change along the diffuser are presented. Among other values: the Boussinesq number, outlet Coriolis coefficient and swirl flow loss coefficient dependences on inlet swirl flow parameter are also given. The swirl flow specific energy and outlet Coriolis coefficient calculation procedure are presented in this paper, as well as experimental test bed and measuring procedures. The swirl flow fields were induced by the axial fan impeller. Various swirl parameters were achieved by the impeller openings and rotational speeds.

Fluid machinery courses demand, besides theoretical approach, also good practice and laboratory exercises. After course completion, students should be aware of all aspects of good practice and possible problems. Focus of this paper is on hydraulic pumps and designed demonstrational-educational test rig. It is possible to demonstrate and educate students in following: Bernoulli equation, Euler equation for turbomachinery, hydraulic losses, Venturi flow meter - geometry and measurements, cavitation and swirling flow phenomena, as well as in practical issues such as pump testing after international standard ISO 9906, pump control and energy efficiency issues, determination of hydraulic system characteristics, volumetric calibration of the Venturi flow meter, and etc. Students are educated how to choose and connect pressure transmitters, as well as how to calibrate them, how to apply and upgrade developed LabVIEW application. In addition, many components of the installation are transparent, such as pipes at the pipe inlet and pressure side, Venturi flow meter, main and calibration tank, as well as pump spiral casing. Flow visualization and application of modern measurement technique, such as particle image velocimetry are possible in this way. Following experiments of this test rig, students are motivated to generate technical electronic report. In addition are presented virtual experiments, designed in LabVIEW for testing pumps in parallel and series modes.

This paper describes a study case of student production of laboratory model for engineering education and its integration in the local remote laboratory. Students guided by teaching staff are passing through all phases of development and testing of engineering product. In our case, student should produce and test a fan. This part of case study concerning with courses in Hydraulic and Pneumatic Machinery, which incorporates, besides fundamental courses, subjects related to the theory, construction, design and testing of the hydraulic machines (pumps, fans, turbines) and turbo-compressors. After this, students should produce fan and plate system, which is well-known a laboratory model for Control Engineering education. In this paper, are also described procedures and benefits of integration of a laboratory model in Go-Lab Portal as a remote controlled experimental setup with materials for teaching and learning.

Turbulent swirl flow, which exists in numerous turbomachinery systems, is the focus of this paper. It consumes a significant amount of energy, so it is a subject of investigation for many researchers. It is even more present in ventilation systems, as numerous axial fans are still installed without guide vanes. The experimental investigation of the turbulent swirl flow behind an axial fan in a pipe, installed in a test rig with a free inlet and ducted outlet, as defined in the international standard ISO 5801, is presented in this paper. Moreover, in this paper, the axially restricted case is studied. A designed axial fan generates a Rankine vortex with a complex structure, and research on the vortex turbulence structure and dynamics is presented. On the basis of the HSS PIV (high-speed stereo particle image velocimetry), measurement results are calculated using invariant maps. All states of turbulence anisotropy are thoroughly analyzed by applying the invariant theory on HSS PIV results. Vortex dynamics is observed on the basis of the total velocity minima positions and their repetitions. Both methods are correlated, and important conclusions regarding vortex behavior are deduced.

Variable-speed Francis turbines offer the advantages of a broader operational range and enhanced stability. To investigate the internal flow dynamics and pressure pulsation characteristics during the variable-speed operation of the Francis-99 turbine, this paper employs numerical simulations to examine the internal pressure, flow behavior, and energy loss variations over time during the acceleration process. The Hilbert–Huang Transform method is utilized to generate the corresponding time-frequency diagram of the pressure pulsation signal, thereby enhancing the accuracy and reliability of feature extraction. The pressure pulsation signal was decomposed into an intrinsic mode function (IMF) using variational modal decomposition, and fast Fourier transform was applied to the IMF to identify the components contributing most significantly to the pressure fluctuations. The final results demonstrate that the accelerated operation of the Francis-99 turbine positively affects the reduction of hydraulic losses and enhances operational stability. Regarding hydraulic stability, the rotor−stator interference effects must be considered. Following a change in rotor speed, the flow within the runner becomes more complex. However, total entropy production within the Francis-99 turbine decreased by 9.1% following accelerated operation. During acceleration, the dominant frequencies of pressure pulsations at the guide vane outlet and impeller inlet remained at 30 fn and 28 fn, respectively, as speed increased. Furthermore, the peak pressure pulsations at these dominant frequencies were reduced by 83% and 76%, respectively, compared to those observed during fixed-speed operation. This study offers a valuable reference for assessing the instability characteristics of the turbine during variable-speed operation and enhancing operational efficiency.