Visualisation of a flow field was performed within the rotor blade passage of anaxial flow fan operating under rotating stall conditions. A PIV system was used to capture the velocity field at an 80% span of the rotor blade. PIV triggering was synchronized with the observed bladesʼ passing, and over 1000 PIV images were obtained. These were then phase-locked averaged, and a sequence of 36 images was composed. The successive images represented the evolution of a flow field within the blade passage with 10° angular steps and made it possible for the structure and behaviour of the flow within the rotor blade passage to be analysed under rotating stall conditions. The initiation and development of flow distortion were clearly shown to be influenced by the advance of the rotating stall cell and the restoration of normal flow with the rotating stall cell moving away.
COBISS.SI-ID: 17444118
The purpose of the research work in the presented article was to find a solution, by means of a mathematic model, to the problem of how to prepare solid fuels from non-hazardous waste that can be processed into solid fuels according to the national law in force. Non-hazardous waste is defined by the DIRECTIVE 2008/98/ES of the European Parliament and the Council (19.11.2008) - Annex III.1 With the application of a mathematical model and its sensitivity tool, depending on the individual characteristics of the input waste material, the optimal utilization of different waste streams at disposal based on organic and inorganic parameters for the most optimal solution for exploitation was calculated. From the waste material at disposal the desired solid fuel was made in the maximum mass amount with all the necessary qualitative characteristics with the highest quality class and from the rest of the available mass stream solid fuel of lower quality that can still be placed on the market for incineration at cement kilns or incinerators was made. When defining the quality of non-hazardous waste and solid fuel one of the most important tasks of the research was to sample the waste and the fuel correctly, which was reflected in the degree of sample homogenization to find out the chemical, physical and energy characteristics. The analysis of the metal part of the non-hazardous waste was important because of the data about the expected air-emission values of the flue gas, the fly ash, the ash and the slag that occurs when incinerating solid fuel in the heating system. The analysis of the non-metal part of the non-hazardous waste was important from the view of the calorific value of the solid fuel and of the technological and environmental impact. The results of the research showed that it is possible to achieve from the non-hazardous waste at disposal a relatively small mass fraction of high-quality solid fuel from waste according to the whole amount of mass available in Slovenia at present.
COBISS.SI-ID: 16725782
The boundary element method was applied to study the motion of magnetic particles in fluid flow under the action of external nonuniform magnetic field. The derived formulation combines the velocity-vorticity resolved Navier-Stokes equations with the Lagrange based particle tracking model, where the one-way coupling with fluid phase was considered. The derived algorithm was used to test a possible design of high gradient magnetic separation in a narrow channel by computing particles trajectories in channel flow under the influence of hydrodynamic and magnetic forces. Magnetic field gradient was obtained by magnetization wires placed outside of the channel. Simulations with varying external magnetic field and flow rate were preformed in order to asses the collection efficiency of the proposed device. We found that the collection efficiency decreases linearly with increasing flow rate. Also, the collection efficiency was found to increase with magnetic field strength only up a saturation point. Furthermore, we found that high collection efficiently is not feasible at high flow velocity and/or at weak magnetic field. Recommendation for optimal choice of external magnetic field and flow rate is discussed.
COBISS.SI-ID: 16152342
This paper introduces the results of correlated numerical models study carried out to analyse cavitating flows. The flow field of steady attached sheet cavitation and the case of unsteady cavitation behaviour with quasi-periodic fluctuations is analysed with different homogenous cavitation transport models. Three models in form of additional transport equations for water volume fraction are combined with the RANS (Reynolds Averaged Navier-Stokes) equations and calibrated for the cavitating flow around the NACA66 (MOD) hydrofoil by means of an optimisation strategy. In the second stage, the optimised models are applied to the case of internal unsteady cavitating flow in Venturi type section. The results obtained using calibrated models are very close to each other, and agree well with the available experimental data, indicating that the optimisation process is recommended as a general - first step tool for mathematical models validation.
COBISS.SI-ID: 17669398
The presented work focuses on numerical and experimental analyses of biodiesel fuel's influence on the injection characteristics of a mechanically-controlled injection system, and on the operating conditions of aheavy-duty diesel engine. Addressed are mineral diesel fuel and neat biodiesel fuel made from rapeseed oil. The influence of biodiesel on mechanically controlled injection system characteristics was tested experimentally on an injection system test-bed. The injection test-bed was equipped with a glass injection chamber in order to observe the development of the fuel-spray by using a high-speed camera. The results of the experimental measurements were compared to the numerical results obtained by using our own mathematical simulation program. This program has been used to analyze the influences of different fuel properties on the injection systemćs characteristics. The photos taken with a high-speed camera were compared to the simulation results obtained by using the AVL FIRE 3D CFD simulation program. This software was used to simulate the fuel-spray development during different stages of the injection process. Furthermore, the influence of biodiesel fuel on the engine operating condition of a heavy-duty diesel engineand its' emission formation was tested experimentally on an engine test-bed, and numerically by using the AVL BOOST software. It was found out that the tested biodiesel could be used as an alternative fuel for heavy-duty diesel engines.
COBISS.SI-ID: 17091350