Fuel Spray Characteristics Research Articles

Experimental investigation into simulated aging effects of common-rail injector nozzles: Influences on injection rate, spray characteristics, and engine performance

Emission performance of combustion engines has gained outstanding importance with both legislators and customers over the past years. Injector aging, such as nozzle wear or coking, results in the deterioration of injection and emission parameters. In this study, the influences of aging effects on injection rate, fuel spray as well as engine performance and emissions were assessed. Nozzles, which had previously been operated in a vehicle engine and were likely to have suffered from aging, showed no aging-induced characteristics during injection rate and spray measurements and were not investigated further. Therefore, nozzles with different nozzle hole diameters were utilized to simulate the different aging effects. Injection rate measurements demonstrated, that for smaller energizing times, a nozzle with smaller nozzle holes can deliver a higher injected mass than a nozzle with bigger nozzle holes. The adaptation of energizing time or injection pressure demonstrated the potential to compensate the change in engine load due to smaller or bigger nozzle holes. For bigger nozzle holes, the adaptation of injection pressure in order to restore the target load returned lower NOx emissions, whereas the adaptation of the energizing time always yielded lower soot emissions compared to the reference nozzle. For small nozzle holes, the optimization of the start of energizing reduced specific NOx emissions without increasing specific soot emissions. The comparison of measured injection rate and fuel spray characteristics to the ones reported in literature confirms the possibility of simulating nozzle wear by increased nozzle holes and coking by smaller nozzle holes. The results of this study are of vital interest to the research of aging effects and add useful knowledge about compensation methods for nozzle aging.

A Review of Engine Fuel Injection Studies Using Synchrotron Radiation X-ray Imaging

Fuel spray characteristics directly determine the formation pattern and quality of the fuel/air mixture in an engine, and thus affect the combustion process. For this reason, the improvement and optimization of fuel injection systems is crucial to the development of engine technologies. The fuel jet breakup and atomization process is a complex liquid–gas two-phase turbulent flow system that has not yet been fully elucidated. Owing to the limitations of standard optical measurement techniques, the spray breakup mechanism and its interaction with the nozzle internal flow are still unclear. However, in recent years synchrotron radiation (SR) X-ray imaging technologies have been widely applied in engine fuel injection studies because of the higher energy and brilliance of third-generation SR light sources. This review provides a brief introduction to the development of SR technology and compares the critical parameters of the primary third-generation SR light sources available worldwide. The basic principles and applications of various X-ray imaging technologies with regard to nozzle internal structure measurements, visualization of in-nozzle flow characteristics and quantitative analyses of near-field spray transient dynamics are examined in detail.

Three-dimensional flow structure and string cavitation in a fuel injector and their effects on discharged liquid jet

Two kinds of cavitation may occur in mini-sac type diesel injectors. The first is geometrical cavitation, which can usually be seen as a film-like structure in the nozzle. The second is the filament-like string cavitation. Both types of cavitation are known to affect fuel spray characteristics, although the effects of geometrical cavitation and that of string cavitation have not been individually clarified. Moreover, the mechanism behind string cavitation occurrence is still unclear. String cavitation usually occurs at low needle lift, which might indicate the existence of a vortex ring flow in the sac. However, because of the difficulty in precise flow measurement of the three-dimensional flow structure in the sac, the link between vortex ring flow and string cavitation occurrence in the sac has not been proven. In this study, high-speed imaging of string cavitation, geometrical cavitation, and discharged liquid jet of an enlarged three-hole mini-sac diesel fuel injector was conducted to individually clarify the effects of string cavitation and geometrical cavitation on the discharged liquid jet angle. Furthermore, tomographic–stereo particle image velocimetry was carried out on the sac. The experiments were conducted at two different needle lifts, to clarify the link between needle lifts and flow structure in the sac, as well as how it affects string cavitation occurrence and liquid jet angle. The results confirmed that at low needle lift, vortex ring flow forms in the sac, which may induce helical flow in the nozzle, resulting in a large jet angle. Vortex strength varies with time, and string cavitation occurs when the vortex is particularly strong. As a result, the magnitude of the jet angle increase at low needle lift is enhanced when string cavitation occurs. At high needle lift, flow pattern in the sac becomes relatively uniform, which makes it harder for string cavitation to form.

An investigation of deposit formation in the injector, spray characteristics, and performance of a diesel engine fueled with preheated vegetable oil and diesel fuel

ABSTRACTDiesel engines have considered as the popular internal combustion engine used in transport, agriculture-forestry-fishery, and power generator due to their utility. Stringent norms of the environment, increasing demand of energy, and depleted fossil fuel have led to looking for an alternative and renewable energy source. Jatropha oil-based fuels were considered as the appropriate energy source in the future to replace traditional diesel fuel. However, some problems such as coke and deposit formation resulting in the changes in fuel spray characteristics and engine performance were encountered because of high kinematic viscosity and density of straight Jatropha oil when used for diesel engines. The aim of this study is to improve the drawbacks of Jatropha oil by heating before being fueled a 4-stroke–4-cylinder diesel engine. The deposit formation around the injector tips, fuel spray characteristics (including penetration length and cone angle), combustion, and emissions of the above-mentioned diesel engine running on preheated Jatropha oil and diesel fuel after 300 h were practically measured and compared to the first hour (0 h). After completion of the long-term 300 h test, some results of the test engine fueled with preheated Jatropha oil such as a huge amount of deposits around the injectors tips resulting in partly clogging the nozzle holes and increasing penetration length to 10.52%, a decrease of 30.73% for engine power and 7.28% for NOx emissions, an increase in 8.63% of HC and 6.96% of CO emissions were detected; meanwhile, the above parameters for diesel fuel after 300 h of test were insignificantly different from the first hour. Moreover, the element components in deposits were also thoroughly analyzed by EDS, and optical observation was assisted by SEM.

CFD ANALYSIS ON DIFFERENT PISTON BOWL GEOMETRIES BY USING SPLIT INJECTION TECHNIQUES

A better spatial distribution is required for the injected fuel throughout the entire space of combustion geometry in DI diesel engine, to obtain a better combustion with lesser emission. In order to effectively make use of gas flows it is mandatory to match the piston bowl geometry with fuel spray characteristics. For obtaining better combustion, matching of combustion chamber geometry, fuel injection and gas flow plays prominent role. The model was developed in computational fluid dynamics (CFD) code, ANSYS FLUENT. The simulations were conducted for the combinations of swirl ratio, three split injection and four piston bowl geometries (Case A,B,C and D). The simulation results revealed that, the pilot injection creates favorable condition for the upcoming main fuel injection in the case of multiple injection. In case of multiple injections there is a considerable reduction in NO formation. The final NO formed is 24% lower than that of normal injection and 22% lower than that of the retarded injection. The combination of split injection with suitable combustion chamber configuration would greatly enhance the engine performance, besides reducing emission level to a greater extent.

Impact of gasoline direct injection fuel injector hole geometry on spray characteristics under flash boiling and ambient conditions

The effect of injector nozzle design on the Gasoline Direct Injection (GDI) fuel spray characteristics under atmospheric and flash boiling conditions was investigated using Phase Doppler Anemometry (PDA) measurements. To understand the impact of hole diameter and conicity, experiments were conducted on two bespoke 3-hole injectors in a pressure and temperature controlled constant volume chamber and in the open air. The measurements were taken radially outward from the injector axis to the outer extent of the plume at distances of 15 mm, 25 mm and 40 mm from the injector tip.Observations of the influence of surrounding gas and temperature conditions and hole design on the injector spray performance were made. Under non-flash boiling conditions, it was found that the injection pressure dictates the length of the spray penetration before collapse occurs, with an increase in pressure resulting in an increase in this length. Comparison of mean velocity and droplet diameter data are also made to understand the performance under flash boiling conditions. Results show that, under flash boiling conditions, the droplet velocity significantly increases while the droplet size reduces. More importantly, it is found that the impact of the flash boiling environment on sprays of different hole geometries is different. Some hole designs offer more resistance against spray collapse. It was found that the mid-sized of the three hole diameters tested here was found to produce a spray that more readily collapsed than that of the smaller or larger hole diameters. In addition, it was found that under flash boiling conditions, the convergent hole had a greater propensity to exhibit spray collapse.

Development of a decoupling physical-chemical surrogate (DPCS) model for simulation of the spray and combustion of multi-component biodiesel fuels

A decoupling physical–chemical surrogate (DPCS) model was established for simulation of the spray and combustion characteristics of multi-component biodiesel fuels. In the DPCS model, the physical and chemical properties of biodiesel fuels are described separately. For the case study of soybean methyl ester (SME), the physical properties are represented based on the five primary components, i.e., methyl palmitate, methyl stearate, methyl oleate, methyl linoleate, and methyl linoleate. Meanwhile, the chemical kinetics of SME are described by a skeletal reaction mechanism composed of methyl decanoate, methyl 5-decenoate, and n-decane. Furthermore, an improved quasi-dimensional multi-component vaporization model was applied to predict the fuel vaporization process. To validate the DPCS model, the predictions from the present model and the previous models are compared with the experimental data, including the liquid penetration in a constant-volume bomb and the combustion and emission characteristics in a premixed charge compression ignition (PCCI) engine. The results indicate that the predictions of the DPCS model agree better with the measurements than the previous models considering only the single-component physical and/or single-component chemical properties of SME on the spray, ignition, and combustion behaviors. It is found that the ignition delay and heat release rate of PCCI combustion are dominated by the evaporation rate of SME and the fuel-reactivity stratification within the cylinder. By considering the multi-component properties of SME, the combustion and emission characteristics can be satisfactorily reproduced by the DPCS model. Meanwhile, the computational time can be well controlled due to the simplification of the physical and chemical surrogate sub-models.

Experimental study of diesel fuel atomization performance of air blast atomizer

In this study, the spray performance of airblast atomizer is experimentally investigated under different operating conditions and different internal atomizer geometry. The used airblast atomizer is designed so that, the atomizing air is issuing from the atomizer with swirling motion. The swirling of the air blast is formed as passing the through a vane swirler fixed around the fuel exit. The investigated parameters are: the atomizing air swirler angle, the atomizing air to fuel mass ratio and the distance between the fuel nozzle exit and the atomizing air exit orifice. Four air swirlers with vane angels: 0°, 15°, 30°, and 45° are used. The distance between the fuel nozzle exit and the atomizing air exit orifice is changed from 0 to 3 mm. The fuel spray characteristics are studied then represented as spray shape and spray droplets intensities which are photographed using digital camera of particle image velocimetry (PIV). The radial spray concentrations are measured by using the tubes patternator technique. The spray cone angle is also measured under different operating conditions. The fuel used in this study is commercial diesel oil. The results indicate that, the spray cone angle increases with increasing the atomizing air to fuel mass ratio and also by increasing the atomizing air swirler angle while it decreases by increasing the distance between the fuel nozzle exit and the atomizing air exit orifice. The results also show, the spray concentration have its maximum values at the center line and decreases by moving radially outward. The spray intensities are clearly radially decreased. The spray cone angle is increased by about 142% (17°), 120% (18°), 123% (21°) and 120% (24°) for atomizing air swirler angle of 0°, 15°, 30° and 45°, respectively at constant value of the distance between the fuel nozzle exit and the atomizing air exit orifice ratio of zero.

Experimental Study on the Macro Spray and Combustion Characteristics of Mixed Sunflower Oil and Diesel Fuel

Experimental Study on the Macro Spray and Combustion Characteristics of Mixed Sunflower Oil and Diesel Fuel

Experimental investigation on spray, evaporation and combustion characteristics of ethanol-diesel, water-emulsified diesel and neat diesel fuels

This paper explored the spray and combustion characteristics of ethanol-diesel (E10), water-emulsified diesel (W10) and neat diesel (D100), especially micro-explosion of E10 and W10. The experiments were conducted in a constant volume combustion chamber under cold (383 K, 0% O2), evaporating (900 K, 0% O2) and combustion (900 K, 21% O2) conditions. Results showed that the spray expansion capacities of E10 and W10 under cold condition were much weaker than that of D100 due to the larger viscosity of emulsified diesels. Under evaporating condition, the spray volume of E10, W10 and D100 increased by 59%, 34% and 21% respectively comparing with cold spray volume. The higher increasing rates of E10 and W10 were mainly due to the micro-explosion effects of ethanol and water contents. Under combustion condition, the integrated natural flame luminosity (INFL) demonstrated that the ethanol content could accelerate the oxidation of soot, while the water content could prohibit soot generation. Therefore, both ethanol- and water-emulsified diesels could inhibit the soot emission, causing lower final residual soot emission of E10 and W10 than that of D100 by 21% and 39% respectively. Moreover, the flame lift-off length (LOL) and flame spread velocity showed that the effects of micro-explosion in E10 and W10 are different. The micro-explosion in ethanol occurred earlier, which enhanced the reaction rate in upstream flame and reduced the LOL. However, the micro-explosion in W10 occurred later, which enhanced the combustion rate in downstream flame.

Kajian Efek Medan Elektromagnet terhadap Karakteristik Semburan Bahan Bakar Solar, Biodiesel dan Campuran Keduanya

Abstract Research on optimization of diesel engine fuel have been conducted, among other, by utilizing the electromagnetic field. To prove that by using the electromagnetic field of the combustion process to be optimal among them is to analyze the character of atomization. The purpose of this research was to analyze the effect of fuel magnetization on the fuel spray pattern. Experiments were conducted using several fuel including diesel fuel, mixtures of diesel fuel and biodiesel of 10%, 40%, 70%, and biodiesel. Before the spraying test, the fuel was exposed to strong electromagnetic field with variation of wound coil 5000-9000 winding (876-1300 Gauss) for 5 minutes. The spraying test used an injector tester at a pressure of 14.7 Mpa. The spray was observed using a high-speed camera. It was appeared that the larger magnetic field applied to the fuel caused the viscosity to fall in the range of 5-15%, increasing the angle of the sprays or widespread area of the bursts in the range of 3.5-12%, and the particle size of the bursts becomes smaller by 0.2916-0.975 nm. This information is considered to be useful for further research in order to resolutely clarify the phenomenon of efficient combustion process of fuel after exposure to magnetic field. Abstrak Berbagai penelitian tentang pengoptimalisasian bahan bakar motor diesel telah banyak dilakukan, salah satunya dengan memanfaatkan medan elektromagnet. Untuk membuktikan bahwa dengan menggunakan medan elektromagnet proses pembakaran menjadi optimal diantaranya adalah dengan menganalisis karakter semburan bahan bakar. Tujuan penelitian ini adalah menganalisis efek magnetisasi bahan bakar terhadap pola semburan bahan bakar. Bahan bakar yang digunakan adalah solar, B10, B40, B70, dan biodiesel. Bahan bakar yang dicoba diberi paparan kuat medan elektromagnet dengan variasi jumlah lilitan kawat 5000-9000 lilitan 836.45 - 1353 Gauss selama 5 menit (300 detik) dan dilanjutkan dengan proses penyemprotan melalui alat injector tester pada tekanan 14.7 Mpa. Hasilnya diamati dengan kamera kecepatan tinggi. Tampak bahwa makin besar medan magnet yang diberikan pada bahan bakar menyebabkan viskositas turun pada kisaran 5-15%, meningkatkan sudut semburan atau luas daerah semburan menjadi lebih besar berkisar 3.5-12%, dan ukuran partikel semburan menjadi lebih kecil sebesar 0.2916-0.975 nm. Informasi ini berguna untuk penelitian lebih lanjut agar secara jelas dapat mengklarifikasi fenomena magnetisasi bahan bakar terhadap pr o ses pembakaran yang efisien.

Kajian Efek Medan Elektromagnet terhadap Karakteristik Semburan Bahan Bakar Solar, Biodiesel dan Campuran Keduanya

Kajian Efek Medan Elektromagnet terhadap Karakteristik Semburan Bahan Bakar Solar, Biodiesel dan Campuran Keduanya

Experimental Study on Effect of Injection Pressure to Spray Characteristics, Performance and Emissions of DieselEngine DI 20 C Using Biodiesel Fuel

Biodiesel as an alternative fuel can replace fossil fuels. However, biodiesel has a higher value of viscosity, density and surface tension to fossil fuels. Increasing the injection pressure on the injector is one solution to overcome the problem of high viscosity, density, and surface tension in biodiesel. This study aims to determine the effect of increasing injection pressure and injection timing variations on spray characteristics, performance and exhaust emissions diesel engine. Injection pressure namely 200, 210, 220, 230 kg/cm$^2$ by setting the rotation of adjusting screw the injector. The results of this study were obtained by increasing the pressure injection of biodiesel fuel by 230 kg/cm$^2$ resulting in fuel spray characteristics better than the standard 200 kg/cm$^2$ and resulting improvements in the penetration length, spray angle, the average diameter size of each 30$\%$, 28$\%$, and 9.78$\%$. And performance improvements and exhaust emissions also occur, namely Thermal Efficiency, Specific Fuel Consumption, and Smoke Opacity with values of 16.99$\%$, 14.15$\%$, and 46.39$\%$ improved respectively.

Effect of In-Cylinder Conditions on Spray Characteristics of Diesel, Biodiesel, and Biodiesel-Ethanol Blended Fuels

The analysis result of liquid fuel combustion performance shows that the factors affecting chamber combustion are the vaporization and atomization of liquid fuel. At the same time, the combustion chamber conditions and the property of liquid fuel, in turn, affect the heat transfer process and atomization quality. The present work aims to study the effect of in-cylinder conditions on spray characteristics of diesel, biodiesel, and biodiesel-ethanol blended fuels. Besides, research of the addition of ethanol in biodiesel blends compared with diesel is also discussed in this paper. Meanwhile, for the sake of contrastive analysis, two prediction models are adopted, and the corresponding research is conducted. With the experimental results and theoretical analysis approach, the extent and main influencing factors of droplet vaporization and breakup in the spray process are reached. The liquid-fuel penetration and spray tip penetration all present a decreasing tendency with the increase of in-cylinder pressure and percentage of ethanol in blended fuel, and these parameters are affected slightly by the change of in-cylinder temperature in certain range.

Modeling of macroscopic mineral diesel and biodiesel spray characteristics

This paper investigates the injection of fuel into a constant volume spray chamber at high pressures by utilizing macroscopic fuel spray characteristics of mineral diesel and rapeseed oil biodiesel. In the case of lower spray chamber pressure the shapes of fuel sprays tend to be more inclined and indicate higher cavitation inside the nozzle hole. On this basis and from experimentally obtained spray tip penetration and spray angle, a modified mathematical model for spray tip penetration and spray angle is developed. This new model includes two-zone theory and the obtained results agree very well with experiments through the whole interval of spray development.

Transition Weber number between surfactant-laden drop bag breakup and shear breakup of secondary atomization

Fuel spray and atomization characteristics play an important role in the performance of internal combustion engines and many applications of industry. In drop aerobreakup, there are two main breakup modes: general bag breakup and shear breakup, which are induced by Rayleigh-Taylor instability and Kelvin-Helmholtz instability, respectively. Influence of surfactant on drop deformation and breakup is remarkable. So the transition condition of surfactant-laden drop between general bag breakup and shear breakup will be different from pure liquid. In this work, we investigate the influence of surfactant on drop breakup morphology in a continuous air jet stream, and find the physical mechanism of surfactant-laden drop atomization. Finally the predicted expression of transition Weber number is obtained.

Experimental Study on Spray Characteristics of Biodiesel-Diesel Fuels Blends in a Constant Volume Chamber

Spray formation from diesel fuel injection through a realistic heavy-duty multi-hole injector plays a crucial role in the compression ignition engine performance. Fuel Spray characteristics influence the mixture formed in the combustion chamber which affects combustion. The present work is related to high-speed photography of fuel spray characteristics using biodiesel blends at different fuel temperatures. The spray cone angle, a time needed for full development of the spray cone, spray velocity and spray penetration were the primary study parameters. Multi-hole injectors are of paramount importance concerning the CI engines. The purpose of this work is to reveal the effects of fuel temperatures and blend effect on the spray characteristics using biodiesel and diesel fuel. Special significance was that the highest vapor fuel mass concentration was observed at the center region of the spray axis with biodiesel at a higher temperature. This is believed to be due to an increase in the number of small droplets that quickly evaporated. The mean axial velocity of droplets decreased with increasing fuel temperature. Spray penetration reduced with increasing order of fuel temperature.

Experimental study on spray characteristics of long-chain alcohol-diesel fuels in a constant volume chamber

This study aims at study effects of blending long-chain alcohol (n-butanol or n-pentanol) with diesel on the spray characteristics and compare the differences of those spray characteristics between n-butanol-diesel blends and n-pentanol-diesel blends. Results showed that with the addition of long-chain alcohols, the spray tip penetration decreased, the spray cone angle increased and the spray area increased, while with the increasing proportions of long-chain alcohols in blended fuels, the spray area decreased whereas the peak tip velocity increased. Under the same blended ratios, n-butanol-diesel blends showed longer tip penetration, larger cone angle, larger spray area and lower peak tip velocity compared to n-pentanol-diesel blends in the same injection conditions. Furthermore, from the comparison between spray morphology of each tested fuel with each other, it can be inferred that n-butanol-diesel blends have largest spray areas and thinnest spray boundaries, followed by n-pentanol-diesel blends and then pure diesel fuel.

Key fuel properties and engine performances of diesel-ethanol blends, using tetrahydrofuran as surfactant additive

In this paper there were presented researches related to preparation and characterization of physicochemical properties of diesel-ethanol blends stabilized with tetrahydrofuran as surfactant, in order to be used as fuels in compression ignition engines. The main spray characteristics and engine performances of these blends were evaluated by using AVL Fire software. In the first stage of the studies, commercial diesel was mixed with ethanol, in different concentrations (between 2% and 15% v/v), followed by the addition of tetrahydrofuran (THF) until the blends were miscible, i.e. the blends were stabilized. The experiments were done at room temperature (22 °C). The obtained blends were characterized in order to determine the chemical composition and physicochemical properties, i.e. density, kinematic viscosity, surface tension. UV-Vis spectroscopy was utilized in order to determine a semi-quantitative evaluation regarding the chemical composition of the prepared blends and chemical interaction between diesel, ethanol and THF. Based on the determined properties, the fuel spray characteristics, engine performances and emission characteristics were evaluated by simulation using the AVL Fire software. The obtained results regarding physicochemical properties of blends were compared with diesel. Some improvements were observed when operating with the prepared blends compared to diesel with respect to engine performances and emission characteristics. Based on physicochemical evaluation and computer simulation, it was demonstrated that diesel-ethanol-tetrahydrofuran blends can be used as alternative fuel in compression ignition engines.

Impact of fuel on real diesel injector performance in field test

This work assessed the potential impact of diesel fuel complying with the EN 590 standard on real diesel injector performance in a long-term field test. Injector deposit formation has been attributed to diesel fuel instability during storage in relation to fuel injection equipment (FIE) operating conditions. These deposits can occur at different locations within FIE and impact on fuel spray characteristics, causing threats to the proper functioning of the fuel injectors. The long-term field tests were performed with two new vehicles fitted with an advanced common rail (CR) fuel injection system, meeting the requirements of Euro 5. A high quality diesel fuel meeting the requirements of the EN 590 standard was used for both vehicles. A scanning electron microscope with energy dispersive X-ray spectrometry (EDS) and an electron backscatter diffraction (EBSD) detector was used for observation and imaging of external, coking injector deposits around the nozzle fuel-flow holes and internal diesel injector deposits (IDID) in the area of the nozzle needle. An elemental analysis was performed by energy dispersive X-ray spectroscopy analysis (EDX). Evaluation of the macroscopic characteristics revealed that, despite the formation of external and internal injector deposits, there was no measurable loss of flow through the injectors. As a result, while injector deposits have adverse impacts on some injector macroscopic characteristics, they did not cause a significant deterioration of the injectors’ operating characteristic and their real performance.