Development of a hybrid multi-scale simulation approach for spray processes

This paper presents a multi-scale approach coupling a Eulerian interface-tracking method and a Lagrangian particle-tracking method to simulate liquid atomisation processes. This method aims to represent the complete spray atomisation process including the primary break-up process and the secondary break-up process, paving the way for high-fidelity simulations of spray atomisation in the dense spray zone and spray combustion in the dilute spray zone. The Eulerian method is based on the coupled level-set and volume-of-fluid method for interface tracking, which can accurately simulate the primary break-up process. For the coupling approach, the Eulerian method describes only large droplet and ligament structures, while small-scale droplet structures are removed from the resolved Eulerian description and transformed into Lagrangian point-source spherical droplets. The Lagrangian method is thus used to track smaller droplets. In this study, two-dimensional simulations of liquid jet atomisation are performed. We analysed Lagrangian droplet formation and motion using the multi-scale approach. The results indicate that the coupling method successfully achieves multi-scale simulations and accurately models droplet motion after the Eulerian–Lagrangian transition. Finally, the reverse Lagrangian–Eulerian transition is also considered to cope with interactions between Eulerian droplets and Lagrangian droplets.This work was supported by the Engineering and Physical Sciences Research Council of the UK (grant number EP/L000199/1)

Improvements in petrol engine performance with ultrasonic fuel atomisation

Initial studies of the effect of air-fuel mixture preparation on piston engine performance have been conducted on a four cylinder 1600 cc petrol engine using conventional carburation and ultrasonic fuel atomisation. The performance of the engine, under various conditions of operation, has been assessed on the basis of specific fuel consumption and brake mean effective pressure. Whereas only minor differences in performance were found under full power condition at part throttle running of the engine with ultrasonic fuel atomisation improvements in fuel consumption in excess of 10% were observed. These improvements appear to be the direct result of better mixture preparation. Indirect benefits of improved mixture preparation may be a reduction in exhaust smoke and hydrocarbon emission from the engine

Social Dangers of European Integration

Integracja europejska jako proces społeczny pozostaje pod wpływem licznych zagrożeń, które w różnym zakresie mogą na nią oddziaływać. Przynajmniej częściowo występują one na płaszczyźnie politycznej - stając się konsekwencją zachodzących procesów ekonomicznych czy psychologicznych. Ewolucja postaw społecznych jednostek może mieć negatywne znaczenie dla europejskich społeczeństw. W niniejszym artykule szczególną uwagę autorzy poświęcają zagrożeniom płynącym z atomizacji, anomii oraz społecznej alienacji. Odniesieniem dla ich oddziaływania jest sfera społeczno-polityczna. Atomizacja może wpływać na poziom uczestnictwa politycznego i doprowadzić do upadku moralnych i społecznych zasad demokracji. Anomia wiąże się z reakcjami adaptacyjnymi, które mogą powodować wycofanie się z istniejących norm i wartości społecznych. Dodatkowo anomia i atomizacja mogą oddziaływać w ramach megatrendów sprawiając, że trudniej adaptować procesy demokratyzacyjne. Mając na uwadze znaczenie aspektu psychologicznego funkcjonowania jednostki w środowisku społecznym, analizie został poddany także problem alienacji społecznej, który w określonych wymiarach może stanowić istotne zagrożenie dla procesów integracji europejskiej.European integration as a social process is endangered by phenomena which can reduce, stop and downgrade this process. They occur, at least partly, out of political intentions. They become a conseąuence of existing processes in the political, industrial and psychosocial spheres. The evolution of social attitudes of an individual can take the wrong direction, and this can result in a negative influence on social systems. In this paper, special attention is placed on a few of them: atomisation, anomie and social alienation, linked to political and social problems. Atomisation can effect political participation and can lead to morał decay of the social rules of democracy. Anomie leads to adaptation reactions, which can cause withdrawal from existing values and social norms. Additionally, stratification of anomie and atomisation in terms of megatrends makes it harder to counteract their results, because the character of these phenomena leads to an indirect relationship with integration. Bearing in mind the importance of psychological functioning of individuals in a changing social environment, the issue of social alienation that at certain levels of intensity can pose a threat to European integration was also analysed

Spray characteristics of a multi-hole injector for direct-injection gasoline engines

The sprays from a high-pressure multi-hole nozzle injected into a constant-volume chamber have been visualized and quantified in terms of droplet velocity and diameter with a two-component phase Doppler anemometry (PDA) system at injection pressures up to 200 bar and chamber pressures varying from atmospheric to 12 bar. The flow characteristics within the injection system were quantified by means of a fuel injection equipment (FIE) one-dimensional model, providing the injection rate and the injection velocity in the presence of hole cavitation, by an in-house three-dimensional computational fluid dynamics (CFD) model providing the detailed flow distribution for various combinations of nozzle hole configurations, and by a fuel atomization model giving estimates of the droplet size very near to the nozzle exit. The overall spray angle relative to the axis of the injector was found to be almost independent of injection and chamber pressure, a significant advantage relative to swirl pressure atomizers. Temporal droplet velocities were found to increase sharply at the start of injection and then to remain unchanged during the main part of injection, before decreasing rapidly towards the end of injection. The spatial droplet velocity profiles were jet-like at all axial locations, with the local velocity maximum found at the centre of the jet. Within the measured range, the effect of injection pressure on droplet size was rather small while the increase in chamber pressure from atmospheric to 12 bar resulted in much smaller droplet velocities, by up to four-fold, and larger droplet sizes by up to 40 per cent

Drop-charge correlations for polydisperse electrostatically atomized liquid sprays

In many applications liquid sprays are atomized using electrostatic methods, and typically these spray plumes containing drops that have a range of diameters. To understand and predict the dynamics of polydisperse electrically charged spray plumes, knowledge of how the electrical charge is distributed amongst the drops is required. This has been achieved by post-processing phase Doppler anemometry data for two electrostatically atomized liquid sprays and fitting the drop diameter-charge correlation to an assumed relationship of form q=ADn, Here q and D are drop charge and diameter and n and A are empirical constants that describe the correlation. Values of n and A were calculated to be 2.1 to 2.9 and 5.8 ×10-5 for a spray of specific charge 1.8 C/m3 and 2.1 to 3.2 and its value of A is 2.5×10-4 for a spray of specific charge 1.2 C/m3. It was found that the mean drop charge, for all drop diameters, for both data-sets, was almost always less than the drop Rayleigh limit. This latter fact gives confidence in the procedure used since no restriction was placed on this parameter during the processing. We also estimate the distribution of drop charge about the mean value and as a function of diameter and suggest that small drops possess higher rms charge levels

Mechanism of droplet-formation in a supersonic microfluidic spray device

Spray drying is an approach employed in automotive, food, and pharmaceutical industries as a robust and cost efficient liquid atomization technique offering direct control over droplet dimensions. The majority of commercially available spray nozzles are designed for large throughput spray drying applications or uniform surface coating, but microfluidic nebulizers have recently been developed as small scale alternatives. Here, we explore the physical parameters that define the droplet size and formation under supersonic flow conditions commonly found in microfluidic spray drying systems. We examined the spray nozzle operation using high speed imaging and laser scattering measurements, which allowed us to describe the spray regimes and droplet size distributions. It was determined that by using this spray nozzle device, droplets with diameters of 4–8 μm could be generated. Moreover, we show that the supersonic de Laval nozzle model can be used to predict the average droplet size. Our approach can be used as a platform for interfacing fluid microprocessing with gas phase detection and characterization