Experimental investigations on atomization characteristics of dual-orifice atomizers part I: Optimization method formation

In this paper, influences of structure parameters on mass flow and atomization characteristics (spray cone angle, SMD, liquid film fusion and separation) of dual-orifice atomizers were investigated using Fraunhofer diffraction optical instrument and high-speed shadowgraph technique. The main influential structure parameters are obtained by structural parameter sensitivity analysis. Liquid film fusion and separation is an important atomization characteristic lacking of in-depth research. Results of liquid film fusion and separation illustrate that three patterns (separation-fusion-secondary separation) of main stage liquid film and pilot stage liquid film appear with the increase of Δ P. Liquid film fusion makes SMD larger, and there is a delay in liquid film separation when reduce Δ P after liquid film fusion. In addition, mass flow and spray cone angle are key factors which affect liquid film fusion pressure, liquid film secondary separation pressure and distance between two liquid films. The smaller the pilot stage mass flow is, the larger the effect of the main stage on pilot stage spray cone angle will be. Results in this paper could be used to the design and optimization of new dual-orifice atomizers.

A computational study of laminar-flow secondary separation on a slender delta wing

ABSTRACTThe laminar flow over a slender delta wing at incidence has been extensively studied both experimentally and theoretically using vortex sheet methods. These vortex sheet methods have generally been successful apart from the prediction of the secondary boundary-layer separation induced by the primary vortex. This paper revisits the problem using computational fluid dynamics (CFD) and focusses on the effects of the secondary flow separation. The modelling approach is briefly summarised, and the results are compared with flow measurements and results from vortex sheet methods. The computations show very good agreement with measurements for the surface pressures and total head contours. The results help to understand the complex structure of the leading edge vortex flow, and the associated secondary separation of the boundary layer. They indicate that inviscid mechanisms dominate the larger scale features, and highlight a possible mechanism for the development of an instability in the leading edge vortex sheet.

Proximate Design of Onion Harvester Separating Surface

High variability of soil and climatic conditions in Russia requires to develop and use appropriate technologies and technical means to harvest root crops. The authors have determined input parameters that depend on physical and mathematical characteristics of harvested crops, soil type and condition and have a critical impact on developing crop harvesters and harvesting technologies.(Research purpose)The research aims at determining the separation intensity of onion-­soil heap on the rod elevator, as well as onion heap supply from the surface of the rod elevator trails to the secondary separation mechanisms – all relating to onion harvesting machines.(Materials and methods)The size and mass parameters of the studied material are limitative for designing basic parameters of the working elements of technical equipment. The issue of increasing quality indicators of onion picker separators is considered on condition that basic input parameters should be precisely defined as they determine technological process of onion cleaning from soil and plant impurities. The authors have determined the amount of onion heap supply to the onion harvester lifting share in accordance with onion dimensional and mass characteristics.(Results and discussion)The onion fraction in the total lifted heap has been determined as well as the weight of onion heap and impurities on the rod elevator trails and onion heap supply from the surface of the rod elevator trails to the secondary separation mechanisms. The authors have also specified separation intensity as well as interdependencies describing a possibility of loss prevention in onion heap fractional composition passing through the rod elevator slots. The influence of design and technical parameters of the rod elevator as well as the influence of fine soil fraction mass on the onion heap separation intensity of the rod elevator have been revealed as well.(Conclusions)The formula has been obtained to determine onion heap supply from the rod elevator surface to the secondary separation mechanisms depending on design and technical parameters of the rod elevator as well as the onion heap weight.

Models for inviscid wakes past a normal plate

Closed and open hollow wakes are considered as analytic models for the two-dimensional inviscid steady flow past a plate normal to the stream. It is shown that only open configurations which satisfy the Kutta condition exist. The main argument is based on considering a plate located on the edge of a step with varying height. It is shown that solutions for open wakes exist for backward-, null and forward-facing steps, while closed wakes only exist for backward-facing steps. The occurrence of secondary separation has been modelled by adding a hollow region attached to the downstream corner. Peculiar accuracy issues of the problem are pointed out which may explain other contradictory results from the literature. It is shown how the Kirchhoff wake is a limiting solution for certain values of the governing parameters.