Spray Cone Angle Research Articles

SPRAY VISUALIZATION OF HYDROTREATED VEGETABLE OIL UNDER SIMULATED DIESEL ENGINE CONDITION

The diversity of alternative fuels and the corresponding variation in their physical and chemical properties, coupled with simultaneous changes in advanced techniques for CI-engine, needed to improve engine efficiency and emissions. Hydrotreated Vegetable Oil (HVO), seen as a promising substitution for petrol-diesel, and diesel fuel (mixed of 7% palm-biodiesel or B7) were analyzed on fuel properties. Then, the influence of these fuel properties on spray characteristics in constant volume combustion chamber were evaluated under conditions of single hole injector of 200m diameter, injection pressure of 100MPa, constant back pressure of 4.0MPa and energizing time of 2.5ms. The results show that HVO had smaller in viscosity (18.48%), density (5.52%), sulfur content, distillation under T50, T90 and higher in derived cetane index (27.2%), heating value (2.2%), respectively, compared to diesel. Spray characteristics of HVO had the same propensity with diesel fuel. HVO revealed a slightly shorter in penetration length (5%) during fully developed zone, a larger spray cone angle (from 0.2 to 1.1 degree wider in quasi-steady state). Both fuels had a similar maximum spray velocity reaching at 5mm to 10mm from nozzle orifice. Also observed was an increase in spray volume of HVO.

Study of pressure swirl atomizer with tangential input at design point and outside of design point

Pressure swirl atomizers with tangential inputs are widely used in various industries, including power generation and gas turbines. For example, in combustion chambers with increasing time, a lot of factors, such as sediments and corrosions, cause their dimensions to reduce, and therefore, the working condition of these chambers moves outside of the design point. The main purpose of this work is to study the properties of spray at the design point and outside of the design point. To satisfy this objective, design and fabrication of an injector were done first based on some physical parameters, such as pressure difference, spray cone angle, flow rate, fluid type, and so on, and then, it was tested experimentally. Afterward, the effects of the main parameters at the design point and outside of the design point were studied numerically. The results showed a 50% increase in the number of tangential inputs from the design point lowers the pressure difference and spray cone angle by 63.72% and 10.53%, respectively. The increment of the swirl chamber length to 17% can reduce the respective pressure difference and spray cone angle up to 34.2% and 4.5%, respectively. This study also demonstrates that an increase in the length of the orifice lessens the total velocity and pressure as well. A reduction of 22.73% of the outlet nozzle diameter raises the average droplet diameter and flow number to 12.98%, and 11.8%, respectively. Finally, for the requirement of spray properties in a practical situation, the present study can be adopted to predict them accurately.

Experimental study on spray characteristics of six-component diesel surrogate fuel under sub/trans/supercritical conditions with different injection pressures

The purpose of this study is to explore the spray characteristics of six-component diesel surrogate fuel under sub/trans/supercritical conditions with different injection pressures and provide a reference for numerical simulation. The experiments were conducted in a constant volume chamber. The liquid- and vapor-phase spray images were captured by backlight illumination and schlieren imaging technology, respectively. Some macroscopic parameters were obtained and analyzed, such as spray structure, spray penetration, liquid-core index, spray cone angle, gas entrainment mass, spray perimeter, spray area, and spray irregularity. Results show that the variation law of the liquid-phase penetration shows opposite trend with injection pressure depending on ambient temperature. The liquid-phase spray is more stable with a smoother surface under supercritical conditions. The spray cone angle is mainly related to ambient temperature and pressure. The gas entrainment mass increases with decreasing ambient temperature or increasing ambient pressure. When the ambient pressure is twice fuel’s critical pressure, the liquid-phase spray irregularity is smaller, but an increase in injection pressure can further increase the spray irregularity. When the ambient temperature is higher than the critical temperature, increasing the injection pressure or ambient pressure is conducive to increasing the ratio of pure vapor-phase spray and improving the spray characteristics.

IMPACT OF ENLARGED SCALES AND CONTINUOUS BUBBLES ON CAVITATION PATTERNS OF DIESEL NOZZLES

Spray developments are mostly influenced by the flow characteristics inside a diesel nozzle orifice. In this paper, an experimental visual system is built with transparent nozzles. This test rig is used to explore the effect of enlarged scales and continuous bubbles on the cavitation phenomena in CI nozzles. The variation of discharge coefficient with the cavitation number under two cavitation patterns and the scale effect of string cavitation on the discharge coefficient under three enlarged scales are also explored. Additionally, the spatial distribution of standard deviations with two cavitation patterns is compared and analyzed. Under different enlarged scales, the results indicate that the development stages of string cavitation with two-phase flow are almost the same, having similar behaviors through the transitional period from single-phase flow to cavitation fully developed flow. Compared to the situation without bubbles, the cavitation intensity and spray cone angle are promoted. Furthermore, the effect of continuous bubbles is studied under the single-injection working condition, and the results illustrate that string cavitation is very sensitive to the bubble content. The finding also reveals that continuous bubbles lead to an enhancement in the string cavitation inception compared to that in the geometry-induced cavitation under the same conditions.

Numerical Simulation of Characteristics of Spray Flow Field on the Conical Surface

Aiming at the gas-liquid two-phase flow process in the spray flow field on the conical outer surface, based on Euler-Euler method a spray film forming model is proposed. A polyhedral mesh was utilized to divide the fluid computing domain and the coupled SIMPLE algorithm was adopted to solve the model. The results of show that the spray shape on the outer surface of the cone is similar to that on the outer surface of the arc, and both are in the shape of an elliptical cone; in the area far away from the wall surface, the difference ofsurface has almost no effect on the spray cone angle. In terms of the spraying speeds of the two spraying methods within the area close to the outer surface of the cone, for the circumferential spraying, the spray normal speed is higher than that of spraying along the busbar, and the maximum tangential speed is lower. Meanwhile, both the two speeds are almost equal to that of spraying the arc surface; for spraying along the busbar, the spray normal speed is higher than that of the arc outer surface, and the maximum tangential speed is lower.

Experimental and numerical investigation of low sulfur heavy fuel oil spray characteristics under high temperature and pressure conditions

The spray characteristics of low sulfur heavy fuel oil (HFO) are firstly investigated by the experimental and numerical methods, and some new findings are obtained. First, the experiments have been conducted to evaluate the influence of low-sulfurization on the spray characteristics for HFOs under varied conditions, while little effect is found on the spray macroscopic features. The tip penetration of HFO spray behaves like a non-evaporating spray, but it is like an evaporation spray in terms of the cone angle under high temperature and pressure conditions. The large increment in ambient temperature is found to show little effect on its tip penetration but lead to a visible reduction in cone angle. This is because the spray tip penetration and cone angle are separately predominated by non-volatile and volatile components. The evaporation and pyrolysis penetration lengths are proposed for low sulfur HFO sprays as criteria for discriminating the dominant periods by volatile and non-volatile components. Then, a multicomponent evaporation model combined with real-gas vapor–liquid equilibrium has been implemented into OpenFOAM code. The numerical simulations have been carried out and extensively validated against the experimental data. The simulated HFO spray exhibits a distinct liquid penetration length, which agrees with the proposed evaporation penetration length in experiment. This is contributed to confirming the occurrence of pyrolysis and polymerization in low sulfur HFO spray. Finally, the vapor distribution and stratification in the low sulfur HFO spray are presented, and the heavy-end multi-ring aromatics exhibit low evaporation rate and large effects on the mixture generations.

Prediction of the Initial Drop Size and Velocity Distribution in the Cold Cryogenic Spray

The polydispersed nature of the spray is captured through the use of probability density functions based on the maximum entropy method to stand for the complete atomization characteristics of spray dynamics. The droplet and velocity size distributions are practical tools for the analysis of sprays cooling. The special benefit of the model is a Eulerian based which is less computationally intensive when compared to models that are based on the Lagrangian approach that tracks droplet parcel. The accuracy of using Lagrangian approach in polydispersed phase is always accurately less than Eulerian approach because it depends on the number of parcels while in Eulerian approach it depends on the proposed continuous distribution function. The main intent of the current work is to evaluate the capability of using the model for the initial predictions of the droplet size and velocity distribution for liquid nitrogen spray of solid-cone pressure swirl nozzle. The use of liquid injection pressure cases of up to 0.6MPa and spray cone angles of just 30◦ from three different sets of experimental data. The results being characterized are spray drop size distribution, liquid volume fraction and spray cone angle values. The unsteady analyses of the effect of injection pressure are studied on the cryogenic liquid nitrogen. The numerical results show that the maximum entropy method applies to liquid cryogenic spray and indicates that the model reacts correctly to changes in different injection pressures. Comparisons are also made with measured drop size distribution data that are reasonably captured and the spray cone angle is found to be in good agreement during initial and far-field spray angles.

Study of spiral path angle in pressure-swirl atomizer with spiral path

The purpose of this study was to investigate the effect of the number of spiral paths on the spray cone angle, discharge coefficient and droplet diameter in pressure-swirl atomizer with spiral paths using numerical and experimental methods. Initially, the injector was designed and manufactured based on some assumptions such as operating fluid type, pressure difference, spray cone angle and mass flow rate and then tested. Comparison of test results with design assumptions showed that mass flow rate and spray cone angle and discharge coefficient were 5%, 13.25% and 4% error, respectively. Then, numerical solution method was used for numerical investigation of the influence of geometric parameters. To simulate the two-phase flow, the fluid volume fraction model was used. The numerical solution of mass flow rate and spray cone angle and discharge coefficient showed 7.4%, 9.5% and 11.76% error, respectively. The results showed that the pressure-swirl atomizer with spiral paths has a conical shape and is hollow. Also, the total velocity and its components on the edge of the spray cone have the highest value. Investigations showed that at constant mass flow rate with increasing the torsion of spiral path, the total radial, axial and tangential velocities increased, which increased the spray cone angle and decreased the droplet diameter.

Diesel spray and combustion of multi-hole injectors with micro-hole under ultra-high injection pressure – Non-evaporating spray characteristics

Increasing the injection pressure and reducing the nozzle hole diameters can increase the thermal efficiency of diesel engines (DI). To understand the spray characteristics under ultra-high injection pressure, the spray characteristics of multi-hole injectors with different diameters were investigated under different injection pressures. The results show that the injector with a larger hole diameter has a larger injection delay and a longer injection rate rise and fall time. The injection pressure has a small effect on the injection delay. As the injection pressure increases, the injection rate rise and fall time decreases. Increasing the injection pressure and the hole diameter increases the instability of the spray. The penetration of the injectors with different hole diameters is similar in the initial stage of injection. The penetration increased with the increase of the injection pressure. However, the effect of the high injection pressure on the increase of the penetration becomes weak. The injectors with a larger nozzle hole diameter displayed a larger penetration, spray angle, spray cone angle, and spray area. The micro-hole injector under the ultra-high injection pressure, the expansion of the middle of the spray caused a larger spray angle and spray area. A larger nozzle hole diameter and injection pressure promotes an increase in the gas mass rate. But the injector with the micro-hole diameter has a better ṀA/ṀF ratio and a lower average spray equivalent ratio under ultra-high injection pressure. Naber and Siebers’ penetration model and Inagaki and Mizuta's spray angle model with modified parameters showed the better prediction effect under all experimental conditions.

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.

Experimental Characterization of Two-Phase Aerated Liquid Ethanol and Jet A Spray Flames

This work provides an analysis of an air-assisted atomizing nebulizer’s spray characteristics and combustion behaviors via application of various diagnostics. Two-phase far-field flows and flames of liquid ethanol and practical aviation fuel Jet A were characterized for the droplet distributions, fuel concentrations, and flame dynamics by shadowgraph, Mie scattering, and chemiluminescence imaging of CH*, C2*, and CO2*. Both instantaneous and time-averaged measurements of the two-phase flow and flame characteristics were obtained. Shadowgraphs were used to measure the probability distribution of the droplet diameters. Mie scattering was used to map fuel concentration and obtain the liquid spray cone angles. Estimates of the lifted flame height were obtained by both shadowgraph and Mie scattering, which were verified by the chemiluminescence images. The effect of flow rates on parameters such as flow characteristic, spray cone angle, and drop size spectrum were quantitatively characterized for both ethanol and practical aviation fuel Jet A.

Experimental investigations on atomization characteristics of dual-orifice atomizers part II: Optimization method application

In this paper, the optimization method we obtained from dual-orifice atomizers previously is used to design and optimize new dual-orifice atomizers, whereas there are some differences between the new dual-orifice atomizer and dual-orifice atomizer used in Part I. For example, the mass flow is much smaller, there is an expansion angle at pilot nozzle to regulate pilot stage spray cone angle, and there is no recess length between main nozzle and pilot nozzle. Influences of structure parameters on mass flow, spray cone angle and liquid film fusion and separation are investigated, which are consistent with the expectation. Structure parameters that meet performance requirements of dual-orifice atomizer are analyzed. In addition, a new phenomenon has been found is that liquid film oscillation appears with the increase of Δ P, which should be avoided during the design and optimization of new atomizers. Pilot liquid film oscillation will influence the development of dual-orifice liquid film. Pilot swirling groove depth and expansion angle of pilot nozzle are key parameters that influence liquid film oscillation. Conclusions in this paper can be used to guide the design and optimization of new dual-orifice atomizers.

Numerical study on turbulent dispersion of diesel sprays under ultrahigh injection pressure using large eddy simulation

ABSTRACT The modern diesel engines equipped with an advanced fuel injection system up to ultrahigh injection pressure of 300 MPa are under development at present. The impact of injection pressure on fuel spray characteristics such as spray penetration and spray cone angle has been widely concerned in previous studies. However, it is still lack of the detailed investigation on the turbulent dispersion of small droplets produced by a high-pressure injector due to the limited capability of optical diagnostic techniques to simultaneously measure the two phases. Droplet dispersion due to turbulence plays a major role in high-velocity fuel spray mixing and combustion processes involving group evaporation of droplets. Thus, the effect of different injection pressures on droplet dispersion in nonevaporating diesel sprays was investigated using the Euler-Lagrange framework with large eddy simulation (LES) implemented in an open-source code OpenFOAM. Size-dependent instantaneous radial motion and dispersion characteristics of droplets dominated by large-scale turbulent structures within a polydisperse downstream spray were analyzed in detail. Results show that increasing injection pressure can modestly promote the radial dispersion of most droplets with diameter of 2 ~ 12 µm further downstream at the late stage of injection. This could be the result of the increasing interaction time of droplets with larger turbulent structures due to the increase of spray penetration with increasing injection pressure. However, increasing injection pressure has no significant impact on the strength of droplet-turbulence interaction in terms of slip velocity between droplet and gas phases and this could be quantitatively explained by the droplet Stokes number (St) estimated in this study. The most droplets with 0.1 < St < 10 tend to move and concentrate further radially outward, leading to droplet clustering. Thus, the effect of injection pressure on droplet-turbulence interaction is much less than its influence on droplet size for high-velocity fuel sprays, indicating that the ultrahigh injection pressure has much less important impact on the spatial inhomogeneity of droplet distribution than its influence on the evaporation rate of individual droplets.

Investigation of the Spray Development Process of Gasoline-Biodiesel Blended Fuel Sprays in a Constant Volume Chamber

This study investigated gasoline–biodiesel blended fuel (GB) subjected to a fuel spray development process on macroscopic and microscopic scales. The four tested fuels were neat gasoline and gasoline containing biodiesel (5%, 20%, and 40% by volume) at three different ratios. The initial spray near the nozzle revealed that the spray penetration and spray tip velocity both decreased with decreasing biodiesel blending ratio. In addition, the different spray tip velocities at the start of spraying result in different atomization regimes between the fuels. The GB fuels with a low biodiesel blending ratio were disadvantaged in terms of spray atomization due to their lower spray penetration and tip velocity. The macroscopic spray penetration changes were similar to those observed in the microscopic spray. The fuel with the lower biodiesel blending ratio had a larger spray cone angle, indicating increased radial spray dispersion.

Primary break-up and atomization characteristics of a nasal spray.

The primary objective of this research was to extract the essential information needed for setting atomization break up models, specifically, the Linear Instability Sheet Atomization (LISA) breakup model, and alternative hollow cone models. A secondary objective was to gain visualization and insight into the atomization break up mechanism caused by the effects of viscosity and surface tension on primary break-up, sheet disintegration, ligament and droplet formation. High speed imaging was used to capture the near-nozzle characteristics for water and drug formulations. This demonstrated more rapid atomization for lower viscosities. Image processing was used to analyze the near-nozzle spray characteristics during the primary break-up of the liquid sheet into ligament formation. Edges of the liquid sheet, spray break-up length, break-up radius, cone angle and dispersion angle were obtained. Spray characteristics pertinent for primary breakup modelling were determined from high speed imaging of multiple spray actuations. The results have established input data for computational modelling involving parametrical analysis of nasal drug delivery.

Analysis of diesel engine injector nozzle spray characteristics fueled with residual fuel oil

Experimental analysis on the spray characteristics of a diesel engine injector nozzle fueled with Residual Fuel Oil (RFO) was carried out in this study. To achieve this, the fuel was characterized to determine its physicochemical properties, and an experimental set up was designed to visualize and capture the spray pattern of the fuel. The images obtained were processed and analysed using Image J software to determine the spray length, spray cone angle, spray area, spray volume, and spray velocity values of the fuel. Experimental results obtained agree with validation models and reveal that spray parameter values of RFO are higher than those of diesel fuel. The values of spray parameters of RFO such as 456mm spray length, 2.85mm Sauter Mean Diameter (SMD) and the low spray cone angle of 12.69°, led to a higher spray volume causing the engine to run on a rich mixture after initial start-up conditions. This would create such challenges as reduction in power and clogging of injector nozzle tip due to an increase in carbon deposits. Regression models generated reveal that these challenges could be eliminated when the spray parameters run on optimal values of 256mm, 6.41cm2, 16.18cm3, 0.96 mm/s and 13.59° for the spray length, spray area, spray volume, spray velocity and the spray angle respectively. These optimal values were obtained when the engine fuel injection time was set to 500μs while running on fuel of viscosity 4.305 mPa.s and temperature of 48 °C.

Combustion characteristics of butanol, butyl butyrate, and Jet A-1 in a swirl-stabilized combustor

Significant growth in the aviation industry has also raised concern on the impact of this sector in terms of environmental pollution. Bio-derived fuels are going to play an important role as potential alternative aviation fuels in the near future to mitigate the carbon footprint. Ethanol is a candidate biofuel which is widely used in many countries in the petrol-ethanol blend for S.I. engines. However, the interest in utilizing biofuels in aviation gas turbine engines is relatively recent. In comparison to ethanol, n-butanol possesses some better fuel properties such as higher energy density, less hygroscopic, lower vapor pressure, higher flash point. Butyl butyrate is another potential candidate which can fulfill the chemical property requirements of alternative aviation fuels. However, compatible substitutes for currently used aviation fuel (such as Jet A-1) are still at the early stage of development. The present study deals with experimental investigations of combustion characteristics of aviation kerosene (Jet A-1), butanol, butyl butyrate, and blends of the last two fuels with Jet A-1 in a swirl-stabilized gas turbine type combustor. Visualization of flame, measurement of temperature inside the flame, and exhaust emissions at the combustor exit are carried out to compare the performance of various fuels relative to Jet A-1. Spray penetration length, ligament length, droplet diameter, and spray cone angle of various fuels obtained using high-speed imaging technique are analyzed to understand the combustion characteristics. Fuel properties of individual fuels and blends are also measured and compared to probe the variation in spray and combustion performances.

Effects of nozzle geometries and needle lift on steadier string cavitation and larger spray angle in common rail diesel injector

The cavitating flow in diesel injector nozzles plays a vital role in spray atomization and formation of fuel–air mixture, since vortex-induced string cavitation has recently been found a much more influence on spray compared to the ordinary geometry-induced film cavitation. In this study, in order to investigating string cavitation and its’ enhancement on spray, the visualization experimental platform for the real-size optical tapered-hole nozzle was built based on the high-pressure common rail fuel injection system. Groups of optical nozzles with different geometries were designed for exploring the couple effects of several nozzle geometric parameters, including nozzle sac chamber depth, nozzle-hole position height and needle lift, on the three-dimension vortex flow structure and then on the string cavitation and spray characteristics. Results indicated that the string cavitation characteristics are tightly associated with couple characteristics of the parameters. The stable and strong string cavitation during the whole injection process can be obtained in the Min-sac nozzle with the high hole position under the low needle lift. The string cavitation extends to the nozzle-hole outlet, and subsequently induces the special hollow cone spray with air in the spray center location and corresponding a larger spray cone angle even under not so high injection pressure.

Theoretical model of swirling thick film flow inside converging nozzles of various geometries

Pressure-swirl jets are of paramount importance in such applications as liquid rockets, gas turbines, and internal combustion engines. Although the external spray has been extensively studied, the internal nozzle flow, which determines the external spray characteristics outside the nozzle, is relatively underexplored. Experimental studies of the internal nozzle flow are available, whereas theoretical approaches are less common, especially for strong swirl flows in which the boundary layer effect at the nozzle walls is significant. Herein, we explore a strongly swirling film flow, where viscous effects become dominant in the entire film and the boundary-layer approximation fails. The parabolized Navier-Stokes equations are solved by using the integral von Karman-Pohlhausen method, and the viscous liquid film flow over the entire nozzle wall is predicted including the central free surface configuration, the film characteristics such as its thickness, velocity components, and the spray cone angle, at the nozzle exit. The theoretical predictions are compared to the experimental data, and the dependence of the spray-cone angle on mass flow rate is experimentally validated. The theoretical parametric studies include the effect of the internal nozzle geometry, initial film thickness, the mass flow rate, and the effect of the swirling strength.

Spray characteristics and flow topologies of high shear injector at high primary swirl

In this paper, we present detailed experimental measurements and analysis on the spray-flow interaction emerging from a newly designed high shear injector. The injector consists of a series of radial/axial entry air swirler with interchangeable flare at the exit and the fuel nozzle mounted concentric to the swirlers. The geometrical parameters concerning the swirl configuration are geometrical swirl number (SNPrim), airflow split ratio(γ), area ratio(Δ), flare angle(θ) and relative flow orientation of primary and secondary swirlers (co and counter-rotation). The time-resolved particle image velocimetry is employed to capture the spray flow field topology. The radial (W/Df) and axial (L/Df) expansion of the recirculation zone are explored with respect to the near field swirl number (SN5). The flow from the present injector indicates a negligible change in the radial expansion (W/Df) of the recirculation zone on switching the relative swirl orientation from counter to co-rotation configuration. The radial dispersion of spray illustrates nearly linear relationship with the size of the recirculation zone, whereas the droplet size distribution is insensitive across the test cases. Furthermore, the spray patternation and droplet size across all the cases indicate that a change in spray cone angle could be achieved without much deteriorating the circumferential uniformity and droplet size distribution. Finally, proper orthogonal decomposition (POD) analysis reveals that with radial expansion of recirculation zone, the peak amplitude shifts to lower frequencies and the turbulent kinetic energy contribution to flow of the different spatial coherent structures change accordingly.