Larger Droplet Diameters Research Articles

Are there any Differences in the Raindrop Size Distributions between Summer Typhoons and Autumn Typhoons？

ABSTRACT To improve typhoon forecasting in southern China, which is one of the most susceptible regions in China by typhoons, it is essential to investigate the microphysical characteristics of various types of typhoon precipitation. In this study, the dual-frequency precipitation radar (DPR) data from the Global Precipitation Measurement (GPM) satellite is adopted to reveal the raindrop size distribution (RSD) characteristics of 18 typhoons that made landfall in southern China during 2014 – 2022. The RSD characteristics of precipitation in the horizontal and vertical directions of summer typhoons (STs) and autumn typhoons (ATs) are examined. There is no obvious difference between the parameters corresponding to STs andATs without considering the precipitation types. The mass-weighted mean diameter (D m ) both STs and ATs are primarily composed of small-sized (D m <1.4 mm) and medium-sized (1.4 mm ≤ D m <2.4 mm) precipitation particles, while STs contain a higher proportion of large-sized (D m ≥2.4 mm) precipitation particles. Convective precipitation during STs contributes most to the large-sized precipitation particles. The STs and the ATs are both dominated by stratiform precipitation, the proportion of convective precipitation is higher in the STs than that in the ATs. While the strong precipitation centres of ATs are primarily made up of small-sized and medium-to-small-sized (1.4 mm ≤ D m <1.7 mm) precipitation particles, the strong precipitation centres of STs are primarily made up of medium-to-large-sized (1.7 mm ≤ D m <2.4 mm) precipitation particles at various vertical profiles. Compared to ATs, the storm height and freezing level height of STs are typically higher, and these variables may contribute to divert D m to relatively larger droplet diameters. An examination of the RSD characteristics of STs and ATs in southern China may assist in advancing our comprehension of the microphysical characteristics of typhoon precipitation.

Effect of droplet diameter on oblique detonations with partially pre-vaporized n–heptane sprays

Liquid fuels have been widely used in propulsion systems for their higher energy density and easier storage, but there are few studies on oblique detonation engines (ODEs) using the liquid fuels. In this study, oblique detonation waves (ODWs) in partially pre-vaporized n–heptane sprays are simulated, using a hybrid Eulerian–Lagrangian algorithm with a skeletal chemical mechanism, to facilitate liquid fuels applications in ODE. A novel phenomenon has been observed, illustrating that the ODW initiation lengths in pre-vaporized n–heptane sprays firstly increase and then decrease with increasing fuel droplet diameters. It is found out that an increase of droplet diameter can increase the transferred heat amount caused by droplets evaporation and lower the inflow temperature, so leading to the increase of ODW initiation length firstly. However, extremely large droplet diameter can markedly reduce the heat transfer rate of the droplet and its surrounding mixture, and the compressed gas-stream behind oblique shock wave has a higher temperature that accelerate the induction chemical reaction and results in a decrease in the ODW initiation length. Furthermore, the unsteady oscillations of ODW initiation structures are also observed even for a steady inflow, which involves the periodic hot spots, normal detonation waves and their evolutions. Some factors causing the unsteady behavior of ODWs are tested through a sensitivity analysis method of the initiation lengths. Through the analyzation, the fluctuation of the post-shock temperatures is the main factor causing the fluctuation of initiation lengths, revealing that inhomogeneous heat loss by evaporation of dispersed liquid droplets is the main reason causing the unsteady behaviors of ODWs and the competition between heat release by chemical reactions and heat loss by evaporation determines the steadiness of ODWs.

Influence of air mass origin on microphysical properties of low-level clouds in a subarctic environment

Abstract. In this work, an analysis was performed to investigate how different long-range transport air masses can affect the microphysical properties of low-level clouds in a clean subarctic environment. The cloud measurements included in situ and remote sensing ground-based techniques and were conducted during eight Pallas Cloud Experiments (PaCEs) held in the autumn between 2004 and 2019. Each PaCE was carried out at the Pallas Atmosphere-Ecosystem Supersite, located in the Finnish subarctic region. Two cloud spectrometer ground setups were installed on the roof of the station to measure cloud microphysical properties: the cloud, aerosol and precipitation spectrometer (CAPS) and the forward-scattering spectrometer probe (FSSP). Air mass histories were analyzed using the Lagrangian FLEXible PARTicle dispersion model (FLEXPART) in order to investigate the differences between five distinct source regions (“Arctic”, “Eastern”, “Southern”, “Western” and “Local”). We observed clear differences in the cloud microphysical properties for the air mass source regions. Arctic air masses were characterized by low liquid water content (LWC), low cloud droplet number concentration (Nc) and comparatively large median volume and effective droplet diameter. The Western region (marine North Atlantic) differed from the Arctic by both higher Nc and LWC. The Eastern region (continental Eurasia) only had a little higher LWC than the Arctic but substantially higher Nc and a smaller droplet diameter. The Southern region (continental Europe) had high Nc and LWC and a very similar droplet diameter to the Eastern region. Finally, the relationship between Nc and droplet size (i.e., the Twomey effect) was characterized for the different source regions, indicating that all region clouds were sensitive to increases in Nc.

A review on different additives and advanced injection strategy on diesel engine characteristics fuelled with first, second and third generation biodiesel

The scarcity of fossil fuels and the increased pollution produced by their combustion requires new alternative sources for CI engines. Biodiesel has been used as an alternative fuel for diesel engines due to its fuel properties. NOx emissions are higher in diesel engines fueled with biodiesel. Further, engine combustion efficiency is also affected by its viscosity and bulk modulus. In addition, injecting high viscous fuel into diesel engines could damage the injector, and a large droplet diameter can reduce the atomization, resulting in poor engine efficiency and higher exhaust emissions. In recent years, an advanced injection strategy has been applied in engine technology to improve engine performance and control smoke and NOx emissions. As a result, this article comprehensively discussed the effect of alcohol and Nano additives on engine characteristics operated with different biodiesel blends. Further, various injection strategies and EGR techniques are also discussed. The literature studies revealed that the combination of split injection and EGR techniques has improved engine performance and simultaneously controlled the NOx and smoke emissions. Also, the CRDI injection system can improve engine efficiency by controlling the injection quantity and pressure. Further, the metal and alcohol-based additives enriched the combustion efficiency and controlled the NOx formation.

Effect of Process Parameters on the Performance of Drop-On-Demand 3D Inkjet Printing: Geometrical-Based Modeling and Experimental Validation.

As additive manufacturing has evolved, 3D inkjet printing (IJP) has become a promising alternative manufacturing method able to manufacture functional multi-material parts in a single process. However, issues with part quality in terms of dimensional errors and lack of precision still restrict its industrial and commercial applications. This study aims at improving the dimensional accuracy of 3D IJP parts by developing an optimization-oriented simulation tool of droplet behavior during the drop-on-demand 3D IJP process. The simulation approach takes into consideration the effect of droplet volume, droplet center-to-center distance, coverage percentage of jetted droplets, the contact angle of the ink on the solid substrate and coalescence performance of overlapping droplets, in addition to the number of printed layers. Following the development of the simulation tool using MATLAB, its feasibility was experimentally validated and the results showed a good agreement with a maximum deviation of 2.25% for horizontal features. In addition, the simulated horizontal features are compared with the results of “Inkraster” software, which also illustrates droplet behavior, however, only in 2D. For vertical features, a dial gauge indicator is used to measure the sample height, and the validation results show that the simulation tool can predicate the height of the sample with an average error of 10.89% for a large droplet diameter and 8.09% for a small diameter. The simulation results were found to be in a good agreement with the dimensions of the printed parts. The developed tool was then used to elucidate the effect of resolution of processed TIFF image and droplet diameter on the dimensional accuracy of 3D IJP parts.

Comprehensively evaluating and modelling droplet diameters and kinetic energies of low‐pressure sprinklers

AbstractProper droplet diameter and kinetic energy can effectively reduce the risk of soil erosion during low‐pressure sprinkler irrigation. In this study, we comprehensively evaluated the radial distributions of droplet diameter, velocity, kinetic energy, kinetic energy per unit droplet volume, and specific power for three common low‐pressure sprinklers, i.e. Nelson D3000, R3000 and Komet KPT, with two operating pressures (103 and 138 kPa) and three nozzle outlet diameters (3.97, 5.95 and 7.94 mm). Additionally, the relationships between these droplet characteristic parameters were analysed. Overall, the maximum values of five characteristic parameters were observed at the end of the jet under various treatments. Although R3000 had a larger droplet diameter (0.10–6.42 mm) and kinetic energy (1.08 × 10−10–8.59 × 10−3 J) distribution range than D3000 and KPT, the D3000 specific power (mean value of 0.4274 W m−2) was the highest of the three sprinklers. Therefore, KPT was suggested more in low‐pressure sprinkler irrigation than in the other two sprinklers because its application rates were reduced along the radial direction. In addition to selecting a suitable sprinkler type for minimizing specific power, determining a reasonable sprinkler spacing was also significant (P &lt; 0.01). Furthermore, a universal specific power model with an appropriate accuracy (RMSE = 0.011 W m−2, NRMSE = 29%) was proposed. This study provides a key basis for the selection and combination of low‐pressure sprinklers.

Study of pressure-swirl atomizer with spiral path at design point and outside of design point

Studies on pressure-swirl atomizers have mainly focused on pressure-swirl atomizers with tangential input while there are limited studies on pressure-swirl atomizers with a spiral path. This study applies experimental and computational methods to provide a better understanding of flow development in this type of atomizer at the design point and outside the design point. Experimental results showed that as the pressure increases, the spray cone angle increases. This increase initially occurs with a higher slope and then the slope is toned down. While the drainage coefficient remains constant, the droplet diameter decreases as the pressure increases. It is observed that similar to the pressure-swirl atomizer with tangential input, the pressure-swirl atomizer with a spiral path has a conical hollow spray. At the constant mass flow rate, as the spiral path cross-section, the length of the swirl chamber and orifice diameter increase, the fluid film thickness and average diameter of droplets increase while the spray cone angle reduces. Further, increasing the number of spiral paths causes a wider spray cone angle, higher discharge coefficient, larger fluid film thickness, and larger droplet diameter. The results also showed that increasing the length of the orifice marginally affected the properties of the spray while significantly reducing the spray cone angle. It is important to note that the numerical results are in good agreement with the experimental data.

Diesel-fired boiler performance and emissions measurements using a combination of diesel and palm biodiesel

Biodiesel is widely accepted as a fuel that is similar to diesel with various advantages. Biodiesel's low-temperature flow qualities are one of its characteristics that limits its use. The goal of this study was to see how volumetric blends of palm biodiesel and diesel, and diesel as a fuel affected the performance and emissions characteristics of a diesel fired vertical coil type, water tube, and non IBR boiler. Various volumetric blends were prepared like PB25, PB50, PB75, PB100 and test in diesel fired boiler with variation in injection pressure. Performance of PB25, PB50, PB75, and PB100 fuels was observed 62.73%, 62.45%, 62.36%, and 62.32%, respectively, compare to pure diesel the value of all blends is either slightly higher or comparative. The maximum boiler efficiency with B100 fuel is 64.98%, which is lower than the pure diesel as fuel 65.30%. Because B100 has a higher kinematic viscosity, it has a larger droplet diameter which lead to poor spray formation and thus a lower boiler efficiency. At 11 bar fuel injection pressure, maximum EGT for diesel, PB25, PB50, PB75, and PB100 fuels is 300 °C, 295 °C, 308 °C, 328 °C, and 340 °C, respectively. Other blends, with the exception of B25, have higher EGT than diesel fuel. At a same fuel injection pressure of 11 bar, CO emissions from diesel, B25, B50, B75, and pure palm biodiesel fuels are 0.037%/Vol., 0.0336%/Vol., 0.0326%/Vol., 0.033%/Vol., and 0.036%/Vol., respectively. CO emissions for PB50 are the lowest of all the fuels tested, followed by B25, diesel, and B100. CO emissions from diesel, PB25, PB50, PB75, and PB100 fuels at maximum fuel pressure are 0.0605%/Vol., 0.0616%/Vol., 0.0605%/Vol., 0.060%/Vol., and 0.05%/Vol., respectively. When compared to diesel fuel, CO emissions from B100 fuel are 21% higher. The highest HC emissions are 18 ppm, 16 ppm, 14 ppm, 13 ppm, and 12 ppm for diesel, PB25, PB50, PB75, and PB100 fuel, respectively. When utilizing B100 fuel, HC emissions are reduced by around half compared to when using diesel fuel.

Morphology-dependent resonances in laser-induced fluorescence images of micrometric gasoline/ethanol droplets utilizing the dye nile red.

The present study deals with the solvent-dependent morphology-dependent resonances (MDR) in the laser-induced fluorescence (LIF) signal of monodisperse gasoline droplets (30µm-60µm) generated with a droplet generator. To investigate the influence of an ethanol addition to gasoline and the respective LIF signal of the dye nile red dissolved in these fuel blends, a reference gasoline fuel is blended with various ethanol concentrations from E0 (gasoline) to E100 (pure ethanol). A spectral fluorescence characterization of the investigated fuel mixtures at various concentrations is carried out in a micro cell in order to identify the dye and ethanol concentration influence of the respective fuel mixtures. The absorption and emission spectra of the fuel mixtures show a Stokes shift with increasing ethanol concentration towards larger wavelengths. The coefficient of variation (COV) of the fluorescence signals of spherical droplets was utilized to characterize the MDR effects within the droplet LIF images. The investigations revealed an increase of MDR contribution in terms of the COV of LIF signals with larger droplet diameters. For small droplets, no monotonic trend was found for contribution of MDR in the LIF signal as a function of the ethanol concentration. For larger droplets (e.g., 50µm-60µm), a lower contribution of MDR in LIF signals was observed with increasing ethanol content. For E80 and most of the studied ethanol blends, the normalized integrated COV values exhibited maxima at certain droplet sizes (40µm, 47.5µm, and 55µm), which indicate the presence of distinct MDR effects.

A Comparison of Soybean Oil Methyl Ester and Diesel Sprays Behavior and Atomization Characteristics

The present numerical study compares between spray characteristics of diesel and soybean oil methyl ester (SME biodiesel) under non-evaporating sprays. The spray structure of diesel and biodiesel fuel (soybean oil) in a common rail injection system are investigated and compared with that of available experimental data used image processing and atomization performance analysis. The proposed approach for the liquid phase, which based on the sprays’ statistical properties, is used to present the gas and liquid phases in an Eulerian-Eulerian approach. The main concept for this model is the possibility of describing a poly disperses spray by using moments of a drop number size distribution function. The main reason for less spray tip penetration in the (SME) comparing with diesel because a larger droplet diameters is the higher density, surface tension and viscosity of (SME). The fuel properties effect on the near nozzle structure is studied. The comparisons are referring that the spray drag, breakup and collision processes are promoted.

A Comparison of Soybean Oil Methyl Ester and Diesel Sprays behavior and atomization characteristics

The present numerical study compares between spray characteristics of diesel and soybean oil methyl ester (SME biodiesel) under non-evaporating sprays. The spray structure of diesel and biodiesel fuel (soybean oil) in a common rail injection system are investigated and compared with that of available experimental data used image processing and atomization performance analysis. The proposed approach for the liquid phase based on the statistical properties of sprays be used to describe the liquid and gas phases in an Eulerian-Eulerian approach. The main concept for this model is the possibility of describing a poly disperse spray by using moments of a drop number size distribution function. The main reason for less spray tip penetration in&#x0D; the (SME) comparing with diesel because a larger droplet diameters is the higher density, viscosity and surface tension of (SME). The effect of fuel properties on the near nozzle structure is studied. The comparisons are referring that the spray drag, breakup and collision processes are promoted.

Liquid phase model and its coupling interaction with the ambient gas for the droplet heating and evaporation of highly volatile R134a

Droplet evaporation plays a decisive role in determining the evolutions of droplet temperature, diameter, and velocity in sprays with low saturation temperature and high volatile mediums. This study conducts a comparative analysis of liquid phase models for single droplet heating and evaporation of high volatile R134a. Three traditional liquid phase models based on the assumption of infinitely large liquid thermal conductivity (lumped), limited thermal conductivity, and effective thermal conductivity and a recently proposed third-order polynomial temperature profile (third-order) liquid phase model based on the presentation of the temperature profile inside the droplet in cubic polynomial form without solving the heat conduction equation are introduced to predict the temporal evolutions of droplet temperature, diameter, and velocity, and the spatial evolution of temperature within the droplet. The coupling of heat and mass transfer between the droplet and its surrounding gas is incorporated into the liquid phase models to investigate its effect on droplet evaporation. The droplet temperature first undergoes a rapid decrease at the transient stage of evaporation and then decreases slowly to the minimum temperature (Tmin). The droplet temperature in the transient stage depends highly on the choice of liquid phase models. Tmin is mostly unaffected by the liquid phase models. The dependence of the droplet diameter at the transient stage of evaporation on the choice of the liquid phase model is stronger compared with the following steady stage. The droplet velocity is rarely influenced in the whole evaporation. The liquid phase models incorporating the coupling weaken the evaporation intensity, resulting in a high droplet temperature and large droplet diameter. The third-order liquid phase model incorporating the coupling model predicts Tmin and agrees with the experimental data. This model can reflect reasonably the heat transfer enhancement by the recirculation inside the droplet for moving droplet.

Study on the dynamic characteristics of spray droplet in air environment under inclined condition

Theoretical investigations on the dynamic characteristics of spray droplet in air environment subjected to the inclination were performed. The inclined angle ranged from 0° to 30°, and the droplet diameter, initial velocity and injection angle ranged from 0.1 mm to 2 mm, from 1 m/s to 10 m/s and from 15° to 75°, respectively. The results show that the larger droplet initial velocity, diameter and injection angle led to the slower decreasing rate of lateral velocity, the longer lateral distance, and the larger coverage area caused by spray droplet. The larger droplet diameter and initial velocity induce the higher growth rate of vertical distance. The greater difference of droplet diameter and initial velocity result in the shorter chasing time and chasing distance. Increasing the inclined angle will result in the decrease of coverage area and the reduction of the impact of inclined angle on it. In addition, the influence of inclined condition on droplet trajectory heightens with the increase of droplet diameter. For different droplet diameters, the influence of inclined angle on the droplet trajectory located in the same direction with inclination is greater than that of the opposite direction. While the inclined angle has a similar influence on the variation tendency of droplet trajectory located in the same and opposite direction with inclination. Impact mechanism analysis concerns droplet trajectory under inclination are conducted to explain the dynamic characteristics of spray droplet.

Numerical Simulation and Experimental Validation of Liquid Metal Droplet Formation in a Co-Flowing Capillary Microfluidic Device.

A two-phase flow axisymmetric numerical model was proposed to understand liquid metal droplet formation in a co-flowing capillary microfluidics device based on a phase field model. The droplet detachment processes were observed in the experiment and are in good agreement with the simulation method. The effects of the viscosities and flowrates of the continuous phase fluid, interfacial tension as well as the wetting property of the metallic needle against the bulk liquid metal on the droplet formation and production rate were numerically investigated. It was found that the droplet diameter decreased with the increment of the viscosities and flowrates of the outer phase carrier fluid. The dispersed phase fluid with high interfacial tension tended to prolong the time for equilibrium between the viscous drag force and interfacial tension on the liquid–liquid fluid surface, delaying the droplet to be pinched off from the capillary orifice and causing large droplet diameter. Finally, the wetting performance of the metallic needle against the liquid metal was explored. The result indicate that the droplet diameter became less dependent on the contact angle while the size distribution of the liquid metal droplet was affected by their wetting performance. A more hydrophilic wetting performance were expected to prepare liquid metal droplet with more monodispersity. The numerical model and simulation results provide the feasibility of predicting the droplet formation with a high surface tension in a glass capillary microfluidic device.

Impeding effect of bubbles on metal transfer in underwater wet FCAW

Aiming at the complicated physical process of underwater wet welding, two background light sources, laser and dysprosium lamp, are combined with high-speed camera to realize synchronous visual sensing of metal transfer, bubble evolution and arc behaviors. The dynamic changes of droplets and bubbles under different arc voltage conditions are investigated. Their interaction relationships are described in detail. From the perspective of the bubble impeding the metal transfer, the reason for the large droplet diameter and low transfer frequency under low arc voltage conditions is analyzed. The gas flow drag force (FL) is the largest at the neck of the bubble separation stage, which greatly affects the stability of the metal transfer process. When the droplet is located above the neck, it is easy to be carried away by separated bubbles to form a spatter. At the same time, the bubbles rising away from the axis of the wire can easily cause the droplet to deviate from the wire.

Energy conservation during single droplet impact on deep liquid pool and jet formation

This paper investigates the impact of single droplets impinged into a deep liquid pool at atmospheric pressure. The single-droplet dynamics of three impinging liquid samples with different surface tensions, viscosities, and densities were experimentally investigated. The time evolution from droplet impingement on the pool surface to jet formation was recorded by a high-speed video camera. The impact velocity and droplet diameter were varied as 1.0–3.2 m/s and 1.8–3.0 mm respectively, and the liquid-pool depth was fixed at 30 mm. The cavity volume was affected by the impact parameters, indicating a clear correlation between drop diameter and impact velocity. For the water droplets, the jet volume was decreased and increased under lower and higher impact velocity conditions, respectively. For ethanol droplets, the jet volume increased at higher impact velocity and larger droplet diameter. To gain deeper physical insight into the jet formation, the energy balance of droplet impingement onto the liquid pool surface was estimated. Approximately 28% of the impact energy was invested in cavity formation, regardless of the liquid properties. The remaining energy was most likely dissipated or consumed at the surface. All of the cavity energy in all samples was consumed in jet formation.

Performance of natural draft hybrid cooling system of large scale steam turbine generator unit

To overcome the shortage of dry cooling technology for large scale steam turbine generator unit in summer, the potential feasibility of hybrid cooling was investigated numerically. The physical model was established for the thermo-flow performances of a hybrid cooling system, which combined the air-cooled heat exchangers and water spray facility in a natural draft cooling tower. The mathematical model included the heat and mass transfer between circulating water and cooling air, as well as the condensation of exhaust steam from turbine. The impacts of cooling modes, operating parameters and ambient conditions of the natural draft hybrid cooling system were investigated accordingly. The results showed that both dry and wet cooling sections determined the thermo-flow performances of hybrid cooling system. Due to the blocking effects of upstream air-flows with medium wind speeds, the hybrid cooling mode may have poorer performance than that of dry cooling system. The large droplet diameter and low spray water flow ratio could deteriorate the thermo-flow performances of hybrid cooling mode, which were even worse than that of dry cooling mode and dry cooling system. The operating parameters obtained and the conditions of cooling mode selection may benefit the future application of the hybrid cooling technology.

Contact angle and droplet evaporation on the smooth and structured wall surface in a wide range of droplet diameters

Droplet evaporation in a wide range of initial volumes of 1–1000μl on the structured and smooth surfaces was studied experimentally. It is found that the static contact angle on the structured surface for the steady equilibrium depends on the droplet shape and initial diameter; it has an extreme. With the increasing wetting diameter of water samples from 2 to 30mm, the contact angle increases first, reaches a maximum, then decreases and tends to a constant value. To determine the contact angle, the authors have performed the comparisons by different methods in a wide range of droplet sizes. A wide range of droplet sizes is usual for spray cooling. Approximation dependences for determining droplet volume were obtained in a wide range of droplet sizes. For the droplets with the initial diameter less than 1mm, middle and large droplets, as well as for the small initial contact angles and angles of about 85–90°, different kinetics of evaporation will be observed. Kinetics of droplet evaporation on the structured surface differs from evaporation on a smooth wall. Dimensionless Fourier number (Fo), derived by the initial droplet diameter and total time of evaporation, decreases with an increase in the wall temperature and initial droplet diameter. For large droplet diameter and a high wall superheating the derivatives d(Fo)/d(Tw) and d(Fo)/d(d0) tend to zero.

Experimental investigation on the effect of n-butanol blending on spray characteristics of soybean biodiesel in a common-rail fuel injection system

In this work, the spray and atomization characteristics of neat soybean biodiesel fuel (BD100) and biodiesel/n-butanol blends (BDB80, 20% of n-butanol (wt.)), were investigated at room temperature and ambient pressure of 1 and 2MPa. A high-pressure common-rail injection system was used to generate sprays from an injector (aperture 0.25mm) at a maximum injection pressure of 100MPa. High speed schlieren technique was used to record the highly transient spray penetration process, through which the spray macroscopic parameters such as spray tip penetration, spray cone angle, projected spray area and spray volume were deduced. In addition, droplet size, number density and its sauter mean values at specific location within the spray cone was analyzed, by using a particle/droplet image analyzing technique (PDIA). Results show that longer spray tip penetration and larger droplet diameters were observed for BD100, compared with BDB80, which was attributed to the lower viscosity and surface tension of BDB80. BDB80 has a spray volume less than BD100, the same trend is also observed in the spray tip penetration. BD100 presents bigger spray area than BDB80 under 1MPa ambient pressure. This is mainly attributed to the bigger spray tip penetration of BD100. The results also show that droplets at the spray periphery have larger diameters than those in the center of the spray due to the effect of air entrainment at the spray periphery. The small particles of fuels are easily sucked into internal of spray. Furthermore, the droplets near the liquid core of spray have more small numbers, where the effect of viscosity is dominant.

A PTV Method Based on SIFT Feature Points Matching for Velocimetry Measurement of Oil-water Two-phase Flow in Horizontal Pipelines

Due to the advantages of scale invariant feature transform (SIFT) feature points on the invariant to image scale, brightness, rotation, occlusion, noise and so on, this paper proposes a Particle Tracking Velocimetry (PTV) method, based on SIFT feature points matching for velocity measurement of oil-water two-phase flow in horizontal pipelines. The oil-water two-phase flow with large droplet diameter, oil droplets overlap, ununiform lighting, and the centroid position of oil droplets can’t be obtained only by using traditional PTV methods through morphological processing. However, in this paper, the algorithm can directly achieve the average velocity of the flow field according to the positions of correctly matched SIFT feature points, and there is no need to extract the centroid coordinates of each oil droplet. The experimental results show that the proposed algorithm not only can be used in the average velocity measurement of oil-water twophase flow in horizontal pipelines, but also can reach 95% in the measuring accuracy when the matching feature points are enough sufficient.