Fuel Atomization Process Research Articles

Application of KH-RT model in lifting flame of methanol jet atomization

Abstract For the methanol jet atomization in a co-flow gas lifting flame, the self-developed WAVE model and KH-RT model were employed using the Saturne program to simulate the primary breakup of the jet column and the atomization of spray particles. Additionally, the unsteady flamelet model was utilized to simulate the combustion process. Comparing the calculated flame lifting height, droplet diameter distribution, and velocity distribution with experimental results demonstrates the atomization model’s ability to accurately capture the methanol fuel atomization process. This comparison verifies the reliability of both the atomization and combustion models, indicating their high accuracy. The study shows that upon injection from the nozzle, methanol fuel rapidly diffused, creating a cone-shaped spray structure. The high concentration of OH radicals is located close to the boundary between the regions of OH radical distribution and methanol distribution, gradually spreading downstream of the methanol jet. Furthermore, an increase in fuel flow rate resulted in a reduction in the flame’s lift height.

Multi-objective optimization of CRDI engine characteristics powered with Mahua methyl ester/diesel blend: a Taguchi fuzzy approach.

An investigation has been conducted on a CRDI (common rail diesel injection) engine utilizing a blended fuel using mahua methyl ester to explore the influence of fuel injection strategies (i.e., FIP, CR, and FIT) on the engine characteristics. It is observed that specific fuel consumption (BSFC) and nitrogen oxide emission (NOx) increased with a decrease in brake thermal efficiency (BTE) in the case of MME100 at a base FIP of 500bar. The volatility and viscosity (physical properties) of the MME fuel blend influenced the combustion phenomena resulting in a reduction in engine performance. The higher viscosity of the methyl ester blend restricts the fuel atomization process during the injection. Fuel injection pressure (Pinj) was raised from 500 to 1000bar in increments of 250bar in the first phase to maximize the use of the MME blend. High injection pressures (1000bar) have higher BTE (12.33%) and better combustion characteristics (2.86%) than lower fuel injection pressures (500bar). The concentrations of smoke (3.62%), CO (15.6%), and HC (2.8%) were reduced as injection pressure was raised, owing to the better formation of the mixture and improved spray atomization. Better results were obtained by optimizing and confirming operational parameters such as compression ratio, injection pressure, and injection time. This optimum value of 1000bar injection pressure, injection timing of 27° bTDC, and a compression ratio of 18: 1 is utilized as the operating parameter values in the subsequent experiments to improve performance and decrease emissions while utilizing MME biodiesel blends in a CRDI engine.

Influence of split injection strategies and Trade-off study on the CRDI engine characteristics powered with waste cooking Oil/Diesel blend

An investigation has been conducted on a CRDI (common-rail diesel injection) engine utilizing a blended fuel with waste cooking oil (WCO20) to explore the influence of fuel injection strategies (i.e., split injection strategy with different fuel injection pressure) on the engine characteristics. It is observed that specific fuel consumption (BSFC) and nitrogen oxide emission (NOx) increased with a decrease in brake thermal efficiency (BTE) in the case of WCO20 at a base FIP of 40 MPa. The volatility and viscosity (physical properties) of the WCO20 fuel blend influenced the combustion phenomena resulting in a reduction in engine performance. The higher viscosity of the methyl ester blend restricts the fuel atomization process during the injection. Fuel injection pressure (Pinj) was raised from 40 to 100 MPa in increments of 25 MPa in the first phase to maximize the use of the WCO20 blend. High injection pressures (100 MPa) have higher BTE (12.33%) and better combustion characteristics (2.86 %) than lower fuel injection pressures (40 MPa). The concentrations of smoke (3.62 %), CO (15.6 %), and HC (2.8 %) were reduced as injection pressure was raised, owing to the better formation of the mixture and improved spray atomization. When used as a pilot injection before the main injection (BMI), 5% WCO20 reduces HC and CO emissions and NOx (7.82%) and smoke emissions while compromising only a marginal amount of thermal efficiency in the second phase.

Study of fuel spray characteristics using a high-pressure common rail diesel injection system by the method of Schlieren

The supercritical atmosphere created by the increase in temperature and pressure in the diesel engine cylinder is the key factor that causes changes in the fuel atomization process. In this study, the differences in spray morphology of n-heptane under different ambient temperature and pressure conditions were investigated using a constant volume combustion bomb combined with the Schlieren method. Based on the Peng-Robinson equation of state (PR equation), several transport characteristics models are constructed to predict the transport characteristics of n-heptane under different operating conditions. During the experiment, the injection pressure and fuel temperature were kept constant (80 MPa, 300 K), the ambient pressure was varied from 2 to 5 MPa, and the fuel temperature was changed from 400 to 800 K, spanning from subcritical to supercritical state. Three different spray regions have been identified based on the fuel temperature and spray geometry: liquid phase region, gas-liquid interface mixing layer, gas phase region. The results show that in a subcritical environment (400 K, 2 MPa), the fuel injection and atomization process is dominated by evaporation. The degree of heat exchange between the fuel and the medium gas is very low, while a small amount of phase change occurs. When the fuel is in low (600 K, 3 MPa) and medium supercritical (600 K, 4 MPa) ambient atmosphere, turbulence becomes the dominant factor in the fuel atomization process. The mixing layer at the gas-liquid interface at the edge of the liquid jet increases significantly. When the fuel is in a high supercritical (700 K, 4 MPa; 800 K, 5 MPa) atmosphere, the jet takes on a shape similar to that of a gas jet, and the mixing layer at the gas-liquid interface becomes the main part of the spray projection area.

Operational evaluation of atomization indicators for gasoline with admixtures of ethanol and butanol during Keep-Clean tests

The global policy of reducing road transport sector pollution requires the introduction of significantly modified already in use technologies and construction solutions. Currently, direct fuel injection technology is the best solution in terms of reducing fuel consumption and exhaust emissions of standard pollutants into the atmosphere, as well as further improving the engine performance. In terms of exhaust emissions, direct injection spark ignition engines are characterized by significantly higher exhaust emissions of particulate matter (approximately 10 times higher) compared to indirect fuel injection SI engines, they show a greater tendency to knocking combustion and are prone to the formation of harmful deposits on engine parts, including in the fuel injectors. The injector tips located in the combustion chamber are exposed to the direct influence of the very high pressure and temperature caused by the combusting fuel-air mixture, which contributes to the rapid formation of harmful deposits. Operation-based injectors contamination in spark ignition engines results in a reduction of the cross-sectional flow diameter of the injector, which then necessitates the extension of the injection time in order to maintain the fuel dose and the expected engine operating parameters. The tests were carried out on an engine dynamometer and an optical test stand for fuel atomization process. The presented research analyzes indicate the possibility of using admixtures that effectively reduce the likelihood of contamination. The paper presents a results analysis of engine tests performed in accordance with the CEC F-113-KC procedure. Additionally, the injectors were tested to conduct an analysis of the injected fuel stream’s geometric indicators. The range, surface area and speed of the injected fuel stream as well as the fuel distribution in the stream were determined based on an equivalent indicator. The obtained results indicated that ethanol and butanol admixtures of 10% (V/V) to gasoline did not significantly extend the fuel injection time as compared to the reference fuel. A further increase in the proportion of ethanol caused a significant deterioration of the fuel flow and the geometric indicators of the fuel spray.

In-nozzle bubble formation and its effect on fuel jet breakup under cavitating and flash boiling conditions

Cavitation and flash boiling are regarded as the most important phenomena in fuel internal flow with phase change. Many researches have shown that both phenomena could enhance the fuel atomization process. In the past 60 years, most of the researchers have investigated these two phenomena individually. Limited research could be found to systematically discuss cavitation and flash boiling as a whole. To address the said issues, a high-speed imaging system coupled with a series of two-dimensional transparent nozzles was adopted to investigate the development of different kinds of bubbles inside of the nozzle. In this study, two different strategies were adopted to control the development of in-nozzle bubbles from the perspective of dynamic control and thermal control, via needle lifting and fuel temperature controlling, respectively. The development mechanism of different kinds of bubbles inside the nozzle was interpreted, and the effect of needle lift on internal flow performance under flash boiling conditions was investigated. It is found that cavitation in the upstream of the nozzle provides nucleus for the inception of flash boiling in the downstream, so as to enhance flash boiling. The decrement of needle lift could enhance the development of all kinds of internal bubbles. Besides, cavitation boiling is proposed in this study. The increment of fuel temperature leads to the decrement of cavitation and the increment of cavitation boiling. Furthermore, the combination of different kinds of bubbles near the nozzle outlet leads to the full fuel break-up process and steady near-nozzle spray.

Modelling Fuel Injector Spray Characteristics in Jet Engines by Using Vine Copulas

SummaryThe emission requirements for jet engines are becoming more stringent and the combustion process determines pollutant emissions. Therefore, we model the distribution of fuel drops generated by a fuel injector in a jet engine, which can be assumed to be a five-dimensional problem in terms of drop size, x-position, y-position, x-velocity and y-velocity. The data are generated by numerical simulations of the fuel atomization process for several jet engine operating conditions. In combustion simulations, the variables are usually assumed to be independent at the start of the simulation, which is clearly not so as our data show. The dependence between some of the variables is non-monotone and asymmetric, which makes the modelling task difficult. Our aim is to provide a realistic parametric model for the dependence structure. For this, we employ vine copulas which provide a flexible way to construct a multivariate distribution function. However, we need to use non-standard bivariate copulas as building blocks. Using this copula representation enables us to create realistic samples of fuel spray droplets which improve the prediction of the combustion process and the pollutant emissions. Moreover, this approach is significantly faster than solving the set of differential equations describing fuel disintegration.

Laser Research of the Fuel Atomization Process of Internal Combustion Engines

The paper presents test methods (mechanical, electrical and optical) for the fuel spray research in combustion engines. Optical methods, imaging and non-imaging can be used in laboratory and engine tests. Imaging methods include flash photography and holography. Their use is limited to testing droplet dimensions larger than 5 µm. Imaging methods have an advantage over non-imaging ones because they allow the droplet to be seen at the point and time where its measurement is required. Non-imaging methods can be divided into two groups: the first, which counts and measures, individual droplets one at a time, and the second, which measures a large number of droplets simultaneously. Exemplary results of research of droplet size distribution in fuel sprays are shown. In tests of atomized fuel spray, in conditions reflecting the conditions of the internal combustion engine, the size of droplets, their distribution in the spray and the velocity of individual droplets are presented. To determine the quality of the fuel spray, two substitute diameters Sauter (D32) and Herdan (D43) were selected, the first of which refers to heat transfer and the second to combustion processes. Laser research equipment including Particle Image Velocimetry laser equipment (PIV), Laser Doppler Velocimeter (LDV) and Phase Doppler Particle Analyzer (PDPA) were applied for testing fuel spray distribution for two kind of fuel. The atomization process from the point of view of combustion and ignition processes, as well as emission levels, is characterized by the best substitute diameter D43, which value is close to the median volume. The most harmful droplets of fuel in the spray are large droplets. Even a few such droplets significantly change the combustion process and emission of toxic exhaust components, mainly NOx.

A Laboratory Investigation into the Fuel Atomization Process in a Diesel Engine for Different Configurations of the Injector Nozzles and Flow Conditions

This paper reports a laboratory investigation of the fuel injection process in a diesel engine. The atomization process of the considered fuel (a hydrocarbon liquid) and the ensuing mixing with air is studied experimentally u... | Find, read and cite all the research you need on Tech Science Press

Experimental studies of the influence of pressure of slurry fuel and air on the spray cone structure during atomization

Results of experimental studies of pneumomechanical atomization process of slurry fuel with a plasticizer in an aerodynamic simulator of power boiler furnace are presented. Analysis of the current state in the field of research of slurry fuel atomization processes has been conducted. Influence of pressure of slurry fuel and air on the structure of the emerging spray cone have been analyzed. The values of characteristic dimensions of three zones of spray cone have been determined: core, middle and outer zones. Effect of pressure of the sprayed slurry fuel and air on the period of stable spray cone formation and geometric characteristics of the zones has been experimentally confirmed. Ranges of velocities and sizes of droplets in the flow at various pressures have been distinguished. The quantitative values of slurry fuel droplets with different velocities in the process of its pneumatic spraying have been obtained. It has been established that the largest number of particles in the study area have velocities up to 8 m/s; a significant number of droplets (up to 20%) have velocities from 8 to 32 m/s; velocities of 32 m/s and more are typical for 1% of droplets. During the results processing, aerosol particles with a size of 1 micron or less have not been taken into account. The values of We criterion for the respective sizes and velocities of the sprayed fuel droplets have been determined. It has been established that significant part of the droplets undergoes catastrophic crushing, which is characteristic for the values of We numbers from 7800 and higher. The obtained results can be used for mathematical and physical modeling of the process of slurry fuels atomization in the furnaces of power boilers in order to predict the aerodynamic characteristics of the designed and existing units.

Optimizing the Shape of a Compression-Ignition Engine Combustion Chamber by Using Simulation Tests

Abstract Modern solutions used in compression-ignition internal combustion engines are quite similar to each other. The use of high-pressure, direct fuel injection results in high combustion rates with controlled exhaust emissions. One of the combustion system quality criteria is to obtain adequately high thermodynamic indicators of the combustion process, which are obtained through, among others, the right combustion chamber geometry. Its shape influences the fuel atomization process, turbulence of fuel dose, evaporation and the combustion process. Optimizing the combustion chamber shape is one of the decisive factors proving the correct execution of the combustion process. This article presents the methodology of choosing the combustion chamber shape (changes of three selected combustion chamber dimensions) by using the optimization methods. Generating multidimensional data while maintaining the correlation structure was performed by using the Latin hypercube method. Chamber optimization was carried out by using the Nelder-Mead method. The combustion chamber shape was optimized for three engine load values (determined by the average indicated pressure) at selected engine operating conditions. The presented method of engine combustion chamber optimization can be used in low and high speed diesel propulsion engines (especially in maritime transport applications).

Research on the effect of cavitation on fuel atomization characteristics by molecular dynamics simulation

The atomization characteristic of fuel is an important factor that affects the combustion stability of aero-gas turbine engine, and is of great significance to the safe operation of aircraft. By means of molecular dynamics simulation, the advantages and disadvantages of cavitation on fuel atomization process are analyzed from the point of view of molecular mechanics and molecular motion, and the influence of cavitation intensity on fuel atomization characteristics is revealed. The results show that when the cavitation intensity ranges from 0% and 5%, the cavitation is helpful to improve the atomization characteristics of fuel. Especially when the cavitation intensity is up to 3%, the dispersion of fuel droplets is the best. However, with the increase of the cavitation intensity, the pressure and energy of fuel decrease sharply, and the breakup, spray penetration and dispersion of fuel become worse, which leads to the deterioration of fuel atomization characteristics.

Strength analysis of the intermediate shaft of the hypocycloidal fuel pump

Diesel engines are currently characterized by very high injection pressure. The high pressure allows to achieve better parameters of the fuel atomization process, thus contributing to the improvement of the engine’s ecological parameters. Achieving such a high pressure is possible thanks to the use of reciprocating positive displacement pumps, enabling the fuel pressure to be increased up to 3000 bar. A common feature of currently produced pumps is the drive of the pressing sections through the camshaft, which is lubricated using fuel. For this reason, cam-driven pumps are very sensitive to the quality of the fuel used, and one of its disadvantageous features is also the generation of lateral force on the piston of the section. For this reason, the authors of the article have developed a pump solution, using a hypocycloid drive, in which the disadvantages of traditional cam-driven pumps have been eliminated. The hypocycloid mechanism used has a separate lubrication system, and due to the generated rectilinear motion only the force parallel to the direction of the movement works on the piston. An important problem in the construction of a hypocycloid pump is the high loads of cooperating elements. The intermediate pump shaft is considered to be the most loaded element due to the complex state of stress. The article presents the methodology and results of simulation tests. Stress states have been determined for the position of the shaft in which it takes the highest load. As a result, it was recognized that the pump shaft was designed properly and despite the high force acting on the piston section, it is possible to ensure its long-term and reliable operation.

Possibilities of improvement fuel atomization process in CI – engines

Modern combustion engines development is targeted on respect of environment protection. Engine constructor main task is lowering toxic substances emission in exhaust. This trend is the same for CI and spark ignition engines. Toxic substances content in exhaust depend on many factors like combustion chamber construction, the sort of fuel and inlet system, fuel – air mixture organize process, the sort of fuel and engine work environment. It was very important period in motorization development implementing electronic engine work steering systems. The factors influence on emission in exhaust analysis shows that there is possibility reduce toxic substances in fumes through correct organizing fuel – air combustion mixture in CI – engine. The injecting fuel streams parameters influence on combustion mixture forming process. The article presents fuel injector modification concept. The aim of modern fuel injector modification is improvement of fuel stream parameters like range, width, atomization and obtuse angle. The performing researches show that making changes on non – working needle part influence especially on particles and carbon monoxide emission.

Digital image processing techniques for the analysis of fuel sprays global pattern

We studied the fuel atomization process of two fuel injectors to be fitted in a new small rotary engine design. The aim was to improve the efficiency of the engine by optimizing the fuel injection system. Fuel sprays were visualised by an optical diagnostic system. Images of fuel sprays were produced under various testing conditions, by changing the line pressure, nozzle size, injection frequency, etc. The atomisers were a high-frequency microfluidic dispensing system and a standard low flow-rate fuel injector. A series of image processing procedures were developed in order to acquire information from the laser-scattering images. This paper presents the macroscopic characterisation of Jet fuel (JP8) sprays. We observed the droplet density distribution, tip velocity, and spray-cone angle against line-pressure and nozzle-size. The analysis was performed for low line-pressure (up to 10 bar) and short injection period (1-2 ms). Local velocity components were measured by applying particle image velocimetry (PIV) on double-exposure images. The discharge velocity was lower in the micro dispensing nozzle sprays and the tip penetration slowed down at higher rates compared to the gasoline injector. The PIV test confirmed that the gasoline injector produced sprays with higher velocity elements at the centre and the tip regions.

Residual fuel atomization process simulation

The process of atomization of fuel in engines with compression ignition is determining in organization of the combustion process, the result of which are the economic and environmental performance of the engine. One of the main parameters of the spray jet fuel is the mean droplet diameter. The article presents the results of analytical and experimental studies by the definition of mean diameter of Sauter droplet of atomized residual fuel IFO380.

Effect of Nanoparticles on the Fuel Properties and Spray Performance of Aviation Turbine Fuel

The influence of nanoparticles' dispersion on the physical properties of aviation fuel and its spray performance has been investigated in this work. To this end, the conventional Jet A-1 aviation fuel and its mixtures with alumina nanoparticles (nanofuel) at different weight concentrations are investigated. The key fuel physical properties such as density, viscosity, and surface tension that are of importance to the fuel atomization process are measured for the base fuel and nanofuels. The macroscopic spray features like spray cone angle and sheet breakup length are determined using the shadowgraph technique. The microscopic spray characteristics such as droplet diameter, droplet velocity, and their distributions are also measured by employing phase Doppler anemometry (PDA) technique. The spray performance is measured at two nozzle injection pressures of 0.3 and 0.9 MPa. The results show that with the increase in nanoparticle concentrations in the base fuel, the fuel viscosity and density increase, whereas the surface tension decreases. On the spray performance, the liquid sheet breakup length decreases with increasing nanoparticle concentrations. Furthermore, the mean droplet diameters of nanofuel are found to be lower than those of the base fuel.

Experimental study on the effect of nozzle hole-to-hole angle on the near-field spray of diesel injector using fast X-ray phase-contrast imaging

Fuel atomization and vaporization process play a critical role in determining the engine combustion and emission. The primary near-nozzle breakup is the vital link between the fuel emerging from the nozzle and the fully atomized spray. In this study, the near-nozzle spray characteristics of diesel injectors with different umbrella angle (UA) were investigated using fast X-ray phase-contrast imaging and quantitative image processing. A classic ‘dumbbell’ profile of spray width (SW) composed of three stages: opening stage, semi-steady stage and closing stage. The SW peaks of two-hole injectors were more than twice of that of single-hole injector at the opening and closing stages, corresponding to the hollow-cone spray. This indicated the vortex flow was formed with the increase of the UA. The higher injection pressure had little influence on the SW while led to earlier breakup closer to the nozzle at lower needle lift. Significant fuel effect on the SW at higher needle lift was found. However, this effect could be neglect at lower needle lift due to the leading role of internal flow and cavitation on the near-field spray characteristics. In addition, the morphology-based breakup process was observed, which highlighted the important effect of internal flow on the spray development. The possibility of using hollow-cone spray in diesel injector was also discussed.

An experimental and numerical analysis of pressure pulsation effects of a Gasoline Direct Injection system

Downsized, turbocharged GDI engines are considered as the most effective system architecture car makers can implement to meet stricter CO2 production and pollutant emissions regulations. Moreover, the GDI engine is accounted to be the ideal thermal part of hybrid powertrains which will play a more and more significant role to meet future CO2 and emissions standards. Hence in the last years significant research efforts are being applied to the development of GDI technology in order to optimize its performance in terms of specific fuel consumption and emission control capabilities.These engines require an extremely reliable high pressure fuel injection system to allow advanced combustion strategies and to improve the fuel atomization process and the air–fuel mixing. Nevertheless, in these installations intense fuel pressure fluctuations may occur due to continuous pumping and injection events, possibly causing low precision in the fuel metering from cylinder to cylinder and relatively poor spray quality. For this reason the injection system design must be supported by accurate computational models able to predict the actual injector flow and the whole fuel system behavior.This paper describes a combined 1-D numerical and experimental analysis of a complete GDI injection system with a particular focus on the waves propagation phenomena and their dependence on the system geometry, such as high pressure pipe length and internal diameter, rail inlet position, flow-restrictor diameter.The numerical code was validated through the comparison of the predicted results with experimental data, mainly pressure and instantaneous injected flow rate measured by a hydraulic test bench (named Wet-System) developed at SprayLab – University of Perugia, which consists of the high pressure pump, the pipes, the fuel rail and injectors so to simulate the complete injection system operation. The injection-system mathematical model was then used to predict the system dynamic response in operating conditions beyond the test bench limits, paying specific attention to the flow-restrictor effect. Finally, the model capability in accurately predicting the waves dynamics effects on the injected fuel flow rate and mass was assessed for multi-injection strategies, when the dwell time between consecutive injections is varied.

Diesel nozzle geometries on spray characteristics with a spray model coupled with nozzle cavitating flow

Fuel spray characteristics is known to significantly affect the combustion and emission processes in diesel engines. High-pressure common-rail system can supply so high injection pressure for getting the better spray characteristics to enhance combustion efficiency and reduce emission. With the fuel injection pressure increasing, spray process becomes more and more complex which makes the study on atomization mechanism more challenging. Under the super high injection pressure, the internal turbulent flow and cavitating flow of the nozzle will greatly influence the subsequent fuel atomization process and spray characteristics, especially the cavitation has been the key to relating internal flow of nozzle and atomization behavior. So it is necessary to simulate the fuel spray process considering of internal cavitating flow of the nozzle. In this paper, firstly, the high-precision three-dimension structure of nozzle with detailed internal geometry information were obtained using synchrotron radiation x-ray phase contrast imaging technology, which was used for the mesh generation of three-dimensional numerical simulation of the cavitating flow in the nozzle. Then the spray model coupled with nozzle cavitating flow was setup in FIRE v2010 and validated by the spray experimental data got from the high-speed imaging technology on a high-pressure common-rail injection system. The spray simulations coupled with cavitating flow showed that the cavitating flow characteristics in nozzles have a large effect on both macroscopic properties and microscopic properties. Finally basing on the above verified spray model, multi-scheme simulations with various geometry parameters of nozzle were performed and the effect of nozzle geometries on the spray characteristics was analyzed and it was concluded that the nozzle sac volume, hole inlet curvature, hole inclination angle, injector needle lift and needle eccentricity had obvious effects on the nozzle flow and subsequent spray, and there was an opposite trend between the spray penetration and Sauter mean diameter, which provided a certain reference value for structure optimization of the fuel system.