Query: atomization characteristics of swirl atomizer

title: Microscopic and macroscopic atomization characteristics of a pressure swirl atomizer, injecting a viscous fuel oil
abstract: Combustion of heavy fuels is one of the main sources of greenhouse gases, particulate emissions, ashes, NOx and SOx. Gasification is an advanced and environmentally friendly process that generates combustible and clean gas products such as hydrogen. Some entrained flow gasifiers operate with Heavy Fuel Oil (HFO) feedstock. In this application, HFO atomization is very important in determining the performance and efficiency of the gasifiers. The atomization characteristics of HFO (Mazut) discharging from a pressure swirl atomizer (PSA) are studied for different pressures difference (Dp) and temperatures in the atmospheric ambient. The investigated parameters include atomizer mass flow rate m discharge coefficient (CD) spray cone angle (th) breakup length (Lb) the unstable wavelength of undulations on the liquid sheet (ls) global and local SMD (sauter mean diameter) and size distribution of droplets. The characteristics of Mazut sheet breakup are deduced from the shadowgraph technique. The experiments on Mazut film breakup were compared with the predictions obtained from the liquid film breakup model. Validity of the theory for predicting maximum unstable wavelength was investigated for HFO (as a highly viscous liquid) A modification on the formulation of maximum unstable wavelength was presented for HFO. SMD decreases by getting far from the atomizer. The measurement for SMD and th were compared with the available correlations. The comparisons of the available correlations with the measurements of SMD and th show a good agreement for Ballester and Varde correlations, respectively. The results show that the experimental sizing data could be presented by Rosin Rammler distributions very well at different pressure difference and temperatures.

title: Influence of orifice geometry on atomization characteristics of pressure swirl atomizer
abstract: The spray characteristics of the pressure swirl nozzle are experimentally studied using particle dynamics analysis (PDA) and high speed photography system in this paper, specifically focusing on the dependence of geometrical dimensions of orifice on the spray SMD, velocity magnitude and droplet distribution, and the spray cone angle. It is indicated that the increase of orifice diameter makes the initial swirling velocity lower and the spray liquid film thicker. When the spray cone is fully expanded, the flow rate of 900 mm orifice diameter nozzle increases by 30 40% and the SMD of 900 mm orifice diameter nozzle increases by 8.5% compared with that of 700 mm orifice diameter nozzle. According to the experimental conditions, the relationship between Re and spray angle was calculated as th 29.97*Re0.087, ignoring the factors that had little influence on spray angle. The decrease of the orifice length makes the distance of gas medium shearing action shorten so that thinner oil film near wall cannot be formed by the extrusion of air core, leading to the swirling intensity reducing and the suction effect weakened. The spray cone angle of the 450 mm orifice length atomizer is about 5deg smaller than the nozzle of 500 mm orifice length, and more small SMD droplets are not sucked, resulting in the distribution range of spray SMD declining.

title: Evaluation of the atomization characteristics of aviation fuels with different viscosities using a pressure swirl atomizer
abstract: With advances in the fuel spray field, much attention has been paid to the atomization characteristics of aviation fuels. The physical properties of fuels play a vital role in their resulting spray structure and spatial distribution of droplets. These characteristics are becoming more important for choosing alternative fuels for optimal performance in next generation gas turbines. The current study experimentally investigated the atomization quality and spray structure of aviation fuels with different viscosities sprayed through a pressure swirl type nozzle by employing laser diagnostics. A set of CCD cameras synchronized to the Nd:YAG laser characterized the spray structure, and the size and velocity of the drops were quantified by the phase Doppler technique. The fuels were tested under various temperature and injection pressure conditions. An alteration in both the injection pressure and the physical properties of the fuel were found to significantly dominate the spray structure and atomization quality. The transitional development of hollow conical sprays was shown to require a sufficient amount of swirl intensity, characterized by their physical properties and injection pressure. Fuels with a lower viscosity were experimentally found to generate well developed hollow conical sprays with finer drops, wide distribution in size, and higher velocity components, which are recognized as ideal spray properties in the combustion field.

title: Analysis on the atomization characteristics of aviation biofuel discharging from simplex swirl atomizer
abstract: The atomization characteristics of aviation biofuel discharging from a simplex swirl atomizer into quiescent atmospheric air are studied. The aviation biofuel is a mixture of 90% commercially available camelina derived biofuel and 10% VonSol 53 (aromatics) The experiments are conducted in a spray test facility at varying fuel flow rate conditions. The measured characteristics include atomizer flow number, spray cone angle, breakup length of liquid sheet, wavelength of undulations on liquid sheet, and spray droplet size. The characteristics of biofuel sheet breakup are deduced from the captured images of biofuel spray. The measurements of spray droplet size distribution are obtained using Spraytec. The experimentally measured characteristics of the biofuel sheet breakup are compared with the predictions obtained from the liquid film breakup model proposed by Senecal et al. (1999) The measurements of wavelength and breakup length of the biofuel sheet discharging from the simplex swirl atomizer agree well with the model predictions. The model predicted droplet size for the biofuel spray is significantly higher than the experimentally measured Sauter mean diameter (SMD) The spray droplets formed from the liquid sheet breakup undergo secondary atomization until 35 45 mm from the atomizer exit and thereafter the SMD increases downstream due to the combined effect of fuel evaporation and droplet coalescence. A good comparison is observed between the experimentally measured SMD of the biofuel spray and the predictions obtained using the empirical correlation reported in literature for sprays discharging from simplex swirl atomizers.

title: Experimental Studies on Fuel Spray Characteristics of Pressure Swirl Atomizer and Air Blast Atomizer
abstract: In this work, the effects of fuel temperatures and pressure drops on the flow field and spray characteristics of a pressure swirl atomizer were discussed using the Particle Imaging Velocimetry (PIV) Planar Laser Induced Fluorescence (PLIF) and Laser Particle Size Analyzer (LPSA) methods. Then the air blast atomizer was selected to study the interaction of initial atomization and flow field. The effect of fuel air ratio on the air blast atomizer were also considered, where the fuel air ratio was varied by adjusting mass flow rate of the air and fuel respectively. The results show that the spray angle of the pressure swirl atomizer increases first and changes a little after the pressure drop higher than 0.5 MPa. However, more fuel concentrate on the central region, which is mainly caused by the increase of the proportion of small droplets with lower centrifugal force. The fuel temperature can improve the spray angle only in lower pressure drop, and it has a little effect under higher pressure drops. In addition, the fuel pressure drop has an obvious influence on the fuel distribution and flow field near the nozzle exit compared with the downstream. For the air blast atomizer, the spray angle increases compared with the pressure swirl atomizer for the introduction of swirl air. Furthermore, the spray angle decreases with the air mass rate increasing, and it increases with the fuel mass rate increasing. The distribution of velocity and droplet near the nozzle exit is influenced by the air mass rate, and the fuel mass rate mainly affects the distribution in the downstream. The fuel accumulates in the annular area below the nozzle, and the distribution of it changes little with the development along the axial direction.

title: Effect of the two phase hybrid mode of effervescent atomizer on the atomization characteristics
abstract: In this paper, the atomization characteristics of an effervescent atomizer were investigated. The velocity, Sauter Mean Diameter (SMD) and atomization cone angle of the droplets were measured using the Phase Doppler Analyzer (PDA) to discuss the effect of different design parameters. The results showed that the atomization was unstable at a small Gas Liquid Rate (GLR) while the atomization proved gradually by increasing the GLR. The optimal atomization region was at a GLR=0.1. In the atomization process, there existed a typical velocity distribution for the swirl atomizer. The design parameters of atomizer provided a great influence on the Sauter Mean Diameter (SMD) and atomization cone angle. The experiment results showed that some droplets had negative velocities.

title: Gas core characteristics of swirl effervescent atomizer
abstract: Swirl effervescent atomizer consists of two atomization mechanisms, effervescent and swirl. For a swirl related atomizer, the air/gas core diameter was reported to be one of the factors affecting the widening of spray angle. A wider spray angle is important to provide a better spray distribution. The characteristic of gas core in an inside out swirl effervescent atomizer was investigated as part of the study in understanding the mechanism of this type of atomization. The interaction effects between three independent parameters (i.e. swirl generating vane angle, gas flowrate and discharge orifice diameter) on the size and characteristics of the gas core were investigated. Water and nitrogen gas were used respectively as the working fluid and atomization gas. The high speed shadowgraph technique was utilized to record the videos of the gas core structures. The video recordings were converted to image sequences and analyzed using an image processing software. It was concluded that a larger gas core was produced with an increasing vane angle or gas flowrate. The increasing gas flowrate tends to increase the gas core size for all cases of the vane angle. Increasing the orifice diameter tends to increase the gas core size for all cases of the gas flowrate. The interaction between the orifice diameter and swirl generating vane angle on the size of the gas core was inconclusive.

title: IGTC 53 Spray Characteristics of Swirl Atomizer at Pressurized Conditions(Session B 3 FUEL ATOMIZATION)

title: Effect of injection pressure on the atomization characteristics of a liquid sheet type swirl injector for Urea SCR system
abstract: In this study, the spray characteristics of a pressure swirl atomizer classified into a liquid sheet type swirl nozzle for Urea SCR system were investigated experimentally with the variation of injection pressure. The length to diameter ratio (l o /d) of the nozzle was 3.1, and the swirler was set inside the nozzle tip to give injecting fluid angular momentum. The injection duration of the nozzle was controlled by PWM (pulse width modulation) modes. The development processes of the spray were imaged by a 2 D PIV system, and the change of spray angle was measured. The atomization characteristics, including axial velocity and SMD, were measured using a 2 D PDA system with the injection pressures at room temperature and ambient pres sure conditions. As the experimental results, the injection pressure had a significant impact on the spray struc ture showing a different shape around the spray leading edge, and the smaller SMD was observed with in creasing injection pressures, which was similar to that of the previous work.

title: Gas Dissolving Effect on the Atomization Characteristics of a Swirl Atomizer