Fuel Spray Characteristics Research Articles

Spray cyclic variations of multicomponent fuels under subcooled, transitional, and superheated conditions

The superheated spray has attracted attention due to itsenhanced atomization in gasoline direct injection (GDI) engines. Even though spray characteristics of multicomponent fuels under superheated conditions have been studied before, the connection between plume-to-plume interaction and spray cyclic variation (SCV) has not been adequately addressed. Moreover, the lack of physical understanding of SCV for multicomponent fuels hampers effort to reduce GDI engine cyclic variations. Thus, this work investigates the SCV of binary and ternary multicomponent fuel blends under superheated conditions. Three pure components of n-pentane, isooctane, and n-decane were analyzed and compared to their twelve binary and ternary blends. The experiments were conducted using the laser Mie-scattering technique in a spray chamber at a fuel temperature of 70 °C and ambient pressure of 50 kPa. This test condition facilitated the occurrence of subcooled, transitional, and superheated sprays for all 15 fuel blends. Five spray plume-to-plume interaction levels are defined to reveal the relationship between the SCV and plume-to-plume interaction. The results show that the spray structure is constrained by the blending ratio of n-pentane (high volatility component). The transitional spray exhibited higher plume-to-plume interaction with larger SCV on the variations of partially connected plumes. Both the non-collapsed spray (no plumes interaction) and totally collapsed spray (wholly merged plumes) showed less SCV. However, the total collapsed spray showed higher SCV compared to non-collapsed spray.

Prediction of the fuel spray characteristics in the combustion chamber with methane and TiO2 nanoparticles via numerical modelling

In this study the methane combustion was analysed with the TiO2nanoparticles. A series of the simulation runs were performed by varying the fuel inlet velocity. However, the oxidizer and the nanoparticles spray were maintained constant for the entire run. The spray velocity varied from 100 m/s to 200 m/s with titanium dioxide (TiO2)nanoparticles. Using the series of the governing equation and modified Navier Stokes equation the model has been developed with the aid of numerical workbench. Three different domains are generated for fuel, oxidizer and nanoparticles. The velocity of the air and nanoparticles were maintained at constant levels and varying only the spray velocity of the fuel. Based on the findings, the mass fraction of both fuel and formation of the CO2were dependent on the spray velocity. As the spray velocity increases the turbulence in the combustion chamber increases which ensures the higher mixing of both air–fuel and nanoparticles. From the procured findings 175 m/s and 200 m/s were the ideal range for better combustion efficiency compared to 100 m/s and 150 m/s. The simulation results have ascertained the role of the spray velocity on the emissions and the combustion efficiency of the engine. It is hoped that obtained results can provide directions to work on the combustion of the methane with the nanoparticles at the optimized spray velocity.

Effects of Accelerated Oxidation on Fuel Spray and Engine Characteristics of Karanja Biodiesel

Abstract The unsaturated content of biodiesel makes it prone to oxidation resulting in variations in the fuel properties, hindering its widespread application. Variations in biodiesel properties impact injection, spray, evaporation, mixing and combustion processes. The present study investigates the effect of accelerated oxidized Karanja biodiesel on injector flow, macroscopic spray, and engine characteristics. The accelerated oxidation of Karanja biodiesel is carried out by heating and bubbling the air through the fuel. The variations in fuel properties that profoundly influence spray and engine characteristics are analyzed before and after accelerated oxidation. Even though biodiesel viscosity is increased beyond the ASTM specification limit due to accelerated oxidation, the variations in the density, surface tension, and calorific value are marginal. The injector flow and macroscopic spray characteristics are investigated for fresh and oxidized biodiesel using a constant volume spray chamber at different chamber and injection pressures. The results indicate a similar fuel flowrate and injection velocity for the fresh and oxidized biodiesels at identical test conditions. Under identical test conditions, the macroscopic spray characteristics between the test fuels are negligible. Engine experiments with fresh and oxidized biodiesel are carried out in an automotive truck diesel engine at rated torque speed and variable load conditions. A shorter ignition delay (∼20% lower), less intense premixed combustion, and lower nitrogen oxide (NOx) emissions (∼27% lower) are observed with oxidized biodiesel. The study concludes that despite significant variations in the kinematic viscosity of fresh and oxidized biodiesels (∼28% higher), the variations in macroscopic spray and engine performance characteristics are insignificant.

Experimental study on spatial distribution characteristics of cylinder-wall oil films under fuel spray impinging condition of GDI engine

This research investigates GDI (Gasoline Direct Injection) fuel spray characteristics, and spray impingement on cylinder-wall oil film were carried out in a constant volume chamber. For studying free spray and spatial distribution characteristics of oil film under spray impinging conditions, the backlight method and LIF (Laser Induced Fluorescence) technology were used, respectively. The influence of injection pressure, ambient pressure, and ambient temperature on the distribution characteristics of oil film with spray impingement were examined. Detailed results on coalescence/splash thresholds criteria of oil film were obtained by considering the incident spray Weber number and the injected fuel mass. In addition, the formation mechanism of oil dilution and splash following the collision were analyzed. It has been found that the incident Weber number is not the only discriminant parameter that can be used to determine the splash criticality of a fuel droplet or spray hitting an oil film. Meanwhile, spray impingement at a higher injection pressure results in a wider spread of oil film, whereas a higher ambient pressure inhibits the spread of oil film.

Modeling the spray characteristics of blended fuels for gasoline direct injection applications

ABSTRACT Methanol and ethanol are considered as potential candidates for alternative fuels in spark-ignited engines and flex-fuel vehicles. Alcoholic fuels have higher latent heat of vaporization (), lower boiling-point temperature and higher-octane numbers help the engine run under higher compression ratios, resulting in better efficiency and fuel economy. A numerical study is carried out to understand the spray-breakup and vaporization characteristics of binary blended fuel and ternary fuel blend compared to single-component fuel for gasoline direct injection (GDI) system. Multiple simulations were carried out by substituting individual fuel properties of isooctane with those of ethanol to understand the relative importance and effect of fuel properties on spray characteristics. The spray characteristics of pure isooctane fuel and their blends with ethanol and methanol are studied and compared, and the charge cooling effects for alcoholic fuels have been observed. The Spray G operating condition has been taken from the Engine Combustion Network (ECN) for this study. The simulated data for isooctane has been validated with the experimental data from the ECN, and a similar model setup has been used for pure and blended fuel sprays. The discrete-phase modeling (DPM) approach is carried out, and the Unsteady Reynolds-Averaged Navier–Stokes (URANS) RNG (Renormalization) k-ε turbulence model is considered in understanding the spray characterization. The blended methanol fuels have higher penetration lengths compared with ethanol ones. The penetration of the blended fuels (binary and ternary) is slightly lower than the isooctane. The ternary blends showed spray characteristics similar to those of E85, and it indicates that the ternary blended fuel has the potential to be used as a drop-in fuel for a GDI-based flex-fuel vehicle.

Spray Characteristics of Bioethanol-Blended Fuel under Various Temperature Conditions Using Laser Mie Scattering and Optical Illumination

Bioethanol has great potential to reduce emissions from transportation while improving energy security and developing the economy. Bioethanol has a higher octane-number and a higher enthalpy of vaporisation than gasoline (resulting in charge cooling)—properties that have been used to extend knocking limits. Therefore, bioethanol can be used to substitute gasoline in automotive engine applications. The characteristics of bioethanol spray, such as hydrous bioethanol fuel which consists of 93% bioethanol and 7% water, were investigated under various temperature conditions from sub-zero (−15 °C) to room temperature (17 °C) by means of high-speed direct photography and laser Mie scattering techniques without any seeding materials. The experimental results show that the spray patterns are not significantly changed. In the case of the sub-zero temperature condition, the spray tip penetration decreases while the spray angle keeps almost constant once the spray becomes fully developed. The results show that scaling of the spray tip penetration rate achieves a reasonable collapse of the experimental results. The normalised droplet diameter was also obtained and shows that larger droplets are formed at the sub-zero temperature condition.

Spray response on a model prefilmer under unsteady airflows of various frequencies

An appealing concept for jet engine combustors is the Lean Premixed Prevaporized (LPP) combustor, which operates at high pressures. The low NOx emissions achieved by lean combustion are one of the targets for modern aircraft engines. However, these types of combustors can introduce thermoacoustic instabilities that can potentially damage the engine and reduce its lifespan. Since the potential instabilities on the fuel spray characteristics, i.e. the spray mass flux, can affect the flame stability, the need arises to investigate the spray response under an unsteady airflow. For this study, a model prefilmer was experimentally investigated to produce a two-dimensional droplet flow without swirl flow. An acoustic forcing in the range of 100–500 Hz was introduced into the airflow, characterized by a hot wire Constant Temperature Anemometry (CTA) setup. Droplet characteristics, namely the droplet diameter distribution and velocity, were determined using a Phase Doppler Anemometry (PDA) setup, while the acquired data were phase-averaged in one period of the airflow oscillation. The influence of the excitation frequency and the air-to-liquid ratio (ALR) on the spray was studied: the spray responded to the acoustic excitation and therefore critical performance parameters, such as the spray mass flux, oscillated indicating potential problems regarding the flame stability.

Effect of Injection Pressure and Ambient Pressure on the Spray Characteristics of Fuels with Different Cetane Numbers

Effect of Injection Pressure and Ambient Pressure on the Spray Characteristics of Fuels with Different Cetane Numbers

Effects of Diesel Injector Nozzle Hole Deposit on Fuel Injection and Spray Characteristics

Effects of Diesel Injector Nozzle Hole Deposit on Fuel Injection and Spray Characteristics

Effect of injection system characteristics on performance, efficiency and emissions of agricultural tractor Diesel engines

The development and the control of Diesel engines combustion process are fundamentally influenced by the parameters of the injection system, namely by the fuel injection characteristic and the injection rate shape. This work comparatively evaluates, by numerical simulation the influences of the injection system characteristics on performance, efficiency, and emissions of two tractor engine types, with four and three cylinders, with similar energetic configuration and same piston displacement. Therefore, the simulation applied two AVL-BOOST computation models, each of them using the AVL-MCC combustion equations system, with the calibration of the models being based on experimental data obtained by testbed investigations. The corresponding specification of the injection systems, together with those of the fuel spray characteristics simulated by the AVL Hydsim tool and the appropriate injection parameters have been adapted for both engines. The results highlighted that for the 3-cylinders engine, presenting lesser total displacement compared to the 4-cylinders one, it is possible to achieve in the condition of similar performance per cylinder, higher efficiency and lower Soot emissions.

Statistical variation analysis of fuel spray characteristics under cross-flow conditions

Owing to cavitation inside the nozzle, spray breakup, and complex flow fields in the cylinder of a spark ignition engine, a certain degree of cycle-to-cycle variation (CCV) remains in different spray cycles under the same operating conditions, thereby affecting the spark ignition engine significantly. Therefore, the effect of cross-flow on the cyclic variation of the spray characteristics is investigated in this work. The CCV of fuel spray characteristics is evaluated via the statistical analysis of 30 repeated experiments under atmospheric pressure. First, the coefficient of variation (COV) is used to assess variations in the spray penetration, area, and optical thickness. Moreover, the effects of injection pressure and cross-flow velocity on the statistical characteristics of the spray are analyzed at the end of injection (EOI). Finally, a dimensionless “Ins number”, which is defined as the parameter of any spray characteristic at a certain time divided by the average experimental value, is proposed to evaluate the spray variation characteristics under cross-flow conditions. Therefore, when the absolute value of the Ins number approaches 1, the CCV of the spray characteristic parameters is low. Results show that the COV of the spray penetration is the largest in the initial stage of injection and then decreases gradually. Meanwhile, the COV of the vertical penetration can be categorized into two stages. Furthermore, it is discovered that the variation in the horizontal penetration is enhanced by the cross-flow and injection pressure at the EOI. In addition, in terms of the COV of the optical thickness, the variation on the windward side is greater, and the cross-flow enhanced the variation in the spray tip region. Most of the Ins numbers of the spray characteristics range from 0.9 to 1.1 (±10%) in this study, and they can provide data support for improving the accuracy of empirical prediction equations and models.

Spray and combustion characteristics of butanol-diesel and hexanol-diesel blends under high-altitude conditions

Due to their excellent fuel properties, butanol and hexanol are considered as two promising renewable fuels for diesel engine applications. The objective of this work is to investigate and compare the spray and combustion characteristics of butanol-diesel and hexanol-diesel blends under high-altitude conditions. A constant volume combustion chamber was used to provide the desired environment. Experiments were conducted under various ambient temperatures ranging from 800 K to 1200 K and various ambient densities ranging from 11 kg/m3 to 15 kg/m3. Fuel blends with 20% blend ratio (B20 and H20) and neat diesel were used as test fuels. The spray and combustion characteristics of the test fuels were analyzed using measured liquid penetration length, ignition delay, combustion duration, flame lift-off length (FLoL), and spatially integrated natural luminosity (SINL). Results revealed that B20 and H20 had shorter liquid penetration length than diesel under low ambient temperature and density conditions due to their higher volatility. The blended fuels showed significantly longer ignition delay than diesel under low ambient temperature conditions, but it could be overcome by increasing the ambient temperature. Adding butanol and hexanol into diesel both extended FLoL especially under low ambient temperature and density conditions, but the effects of hexanol was less dramatic compared to butanol due to its lower latent heat of vaporization and higher chemical reactivity. Both B20 and H20 showed lower SINL than diesel under any conditions, indicating their ability of reducing soot emissions. However, no apparent differences could be found between these two fuels until the ambient temperature dropped to 800 K.

Spray characteristics of standard and alternative aviation fuels at high ambient pressure conditions

The spray characteristics of standard and alternative aviation fuels generated by a hybrid pressure-swirl airblast (HPSA) atomizer were investigated at high ambient pressure conditions. The measurements were performed in an optically accessible pressure vessel at pressures of 1, 2, 3, 4, 5, and 9.5 bar with heated gas and fuel temperatures of 394 K and 332 K, respectively. The drop size and drop velocity of sprays from a standard (Jet-A) and an alternative (C-5) aviation fuels were measured using phase Doppler anemometry (PDA), and 2-D visualization of spray was imaged using simultaneous fuel-Planar Laser Induced Fluorescence (PLIF) and Mie scattering. The spatially resolved PDA drop size measurements were obtained at 25.4 mm downstream of the swirler exit plane and up to 30 mm in the radial direction from the spray centerline. The Sauter Mean Diameter (D32) was observed to decrease significantly with increasing ambient pressure, up to 5 bar. However, the change in D32 was observed to be limited with a further increase in the ambient pressure. A higher swirler pressure drop resulted in a significant reduction in the D32 at an ambient pressure of 5 bar. Using simultaneous fuel-PLIF and Mie scattering imaging, the feasibility of the laser sheet drop-sizing (LSD) technique was examined for the spray at high ambient pressure application. In addition, the effect of ambient pressure on the spray cone angle was investigated using both instantaneous and averaged Mie images. The distribution of fuel vapor and droplets in the spray was also imaged and identified by comparing instantaneous fuel-PLIF and Mie images. A phenomenological three-step atomization model was used to predict the drop size and demonstrate the drop size trend with increasing ambient pressure.

A study of the effect of swirling airflow on fuel spray characteristics under low pressure atmosphere

A study of the effect of swirling airflow on fuel spray characteristics under low pressure atmosphere

Concentration Distribution Characteristics of Two-component Fuel Spray under High-pressure Injection Conditions

Concentration Distribution Characteristics of Two-component Fuel Spray under High-pressure Injection Conditions

Spray Characteristics of Standard and Alternative Aviation Fuels at Cold-start Conditions

The spray characteristics of standard and alternative aviation fuels created by a hybrid pressure-swirl airblast (HPSA) atomizer were investigated at conditions corresponding to engine cold start for an aviation gas turbine. Drop size and drop velocity of sprays from three different fuels, Jet-A (A-2), JP-5 (A-3), and a JP-5/farnesane blend (C-3) were investigated using a phase Doppler anemometry. The spatially resolved drop measurements were obtained at three axial locations downstream of the swirler exit plane and up to 30 mm in the radial direction from the spray centerline. Smaller , , and were observed when increasing the pressure drop across the atomizer swirler (). Increasing also increased the mean axial velocity. No definitive trend was observed with viscosity on drop size, while liquid–gas surface tension showed a weak correlation with drop size due to its small variation in value among fuels. The spray unsteadiness was examined using interparticle arrival time distribution functions. A semi-empirical model was also developed using a phenomenological three-step model for the atomization process of the HPSA atomizer and was used to predict drop-size values at engine cold-start conditions in this work and near lean blowout conditions presented in earlier work.

Polydisperse spray flame ignition by a pulsed heat flux

A mathematical analysis of the ignition of a polydisperse spray/air mixture by an infinite surface heated in a pulsed manner is presented. In contrast to previous work in the literature, the entire history of the ignition process is accounted for starting from the flame-embryo progenitor stage, through the thermal runaway stage to the final flame propagation stage. For tractability at the current stage, the chemical kinetics is taken to be that of a single global reaction. The spray is modeled using the sectional approach and the influence of fuel spray characteristics on ignition is determined. Good agreement was found between the theoretical predictions and full numerical simulations. Delay in ignition due to the build-up of vapor from the fuel droplets as well as heat loss to the droplets for evaporation are found to play a significant role under certain operating conditions. Comparison between the critical energy flux and the initial spray polydispersity revealed small differences for larger values of the pulse duration but more significant minor differences for smaller pulse durations. Despite these seemingly minor differences, it was shown that the initial spray polydispersity can have a critical influence on whether flame ignition will occur or fail, even for sprays having the same initial SMD.

Investigation of preheated Dhupa seed oil biodiesel as an alternative fuel on the performance, emission and combustion in a CI engine

The present study investigates the suitability of preheated Vateria indica methyl ester (VIME) as an alternative fuel for a diesel engine. VIME is a renewable, non-toxic and sustainable alternative biodiesel obtained from Dhupa fat by transesterification. This study aims to evaluate the combustion, performance, and emission characteristics of four different blends such as B0 (0% VIME and 100% mineral diesel), B30, B50 and B100 at elevated fuel inlet temperatures ranging from 35 °C to 95 °C. The tests are carried out in a single cylinder diesel engine at optimum loading condition and fixed speed. Results are obtained in terms of brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), in-cylinder pressure, heat release rate and exhaust emissions (CO, HC, NOX, CO2 and soot). It is observed that the preheating of blends decreases the viscosity which enhances fuel spray characteristics, leading to higher engine performance, lower CO and HC emissions with a slight increase in NOX and CO2 emissions. BTE and peak in-cylinder pressure for B100 at 95 °C and 75% load are increased by 7.44%, 2.97% respectively compared to unheated B100 biodiesel. BSFC, CO, HC emissions at 75% load for B100 at 95 °C are reduced by 26.73%, 28.08%, 42.7% respectively compared to unheated B100.

Effects of autooxidation on the fuel spray characteristics of Karanja biodiesel

A significant obstacle to utilize biodiesel fuel for automotive engine applications is its poor oxidative stability. In the present work, oxidation and spray characteristics of Karanja biodiesel stored for one year are studied. The fuel physical properties that influence the spray characteristics, viz. density, kinematic viscosity, and surface tension, are increased by 0.38%, 12.74%, and 3.95%, respectively, after a one-year storage period. The macroscopic spray characteristics of fresh and aged Karanja biodiesels are compared with that of diesel. The spray penetration length, spray cone angle, and the projected spray area are measured at chamber pressures of 20, 30, and 40 bar and injection pressures of 300, 600, and 900 bar. The results showed reduced mass flow rate at lower injection pressures with fresh and aged biodiesels than diesel. At 300 bar injection pressure, spray penetration length is longer with diesel during the initial injection period, but later the spray slows down. There are no appreciable differences in the spray penetration length and the spray cone angle between diesel, fresh, and aged biodiesels at all the injection pressures. The projected spray area is higher for diesel than biodiesels indicating a denser spray with biodiesels. The study concludes that although biodiesel's long-term storage results in variations in physical and chemical properties, there are no significant variations in the macroscopic spray characteristics. Analysis of atomization characteristics of fresh and aged biodiesels also revealed similar results.

Erratum to: Experimental Studies on Fuel Spray Characteristics of Pressure-Swirl Atomizer and Air-Blast Atomizer

Erratum to: Experimental Studies on Fuel Spray Characteristics of Pressure-Swirl Atomizer and Air-Blast Atomizer