Fuel Atomization Research Articles

Atomization of liquid fuels in an acoustic burner

The acoustic burner based on a modified Hartmann principle in conjunction with a convergent divergent nozzle developed for atomization of high viscous fuels is used to study the atomization characteristics of high viscous fuel oil. The Sauter's mean diameter values of the fuel oil droplets are evaluated by varying parameters such as atomizing air pressure; fuel oil pressure; and air fuel ratio. The mean droplet sizes obtained varies between 12 and 60 μm in contrast to earlier studies which obtained droplet sizes between 55 and 90 μm. A possible mechanism is proposed to explain the reasons for the finer atomization of fuel oil obtained using an acoustic burner.

Internal Flow Effects in Prefilming Airblast Atomizers: Mechanisms of Atomization and Droplet Spectra

Fuel atomization with prefilming airblast nozzles has been investigated. The present analysis is directed toward a detailed investigation of the atomization processes and the clarification of the fundamental phenomena. Two-dimensional models were utilized. High-speed films, showing the deterioration of the liquid film close to the atomizing edge, reveal the dynamics of the liquid’s deterioration and show the motion of the film during the drop formation. The liquid separation is shown to be a periodic process with the drop formation caused by momentum transfer. The frequency spectrum of the liquid separation is determined by means of an optical technique. It is seen that the main frequencies depend only on the air velocity. They are always lower than the corresponding wave frequencies. The droplet size measurements obtained by a light scattering technique emphasize the dominant role of the air velocity at the atomizing edge. A decrease in the surface tension provides an improvement in atomization quality. Other parameters such as liquid flow rate, liquid viscosity, gap height, and length of the prefilming surface within the nozzle were found not to affect directly the droplet size distribution produced, if the air velocity in each of the two ducts of the nozzle is kept constant. The pressure drop of the air, however, rises. It is shown that the droplet size distribution can be easily determined, if the arithmetic mean value of the air velocity in both ducts is known, e.g., from a calculation of the internal flow. Due to the high liquid mass flow rates of airblast nozzles, the wavy film is partly atomized within the nozzle before the liquid separates at the atomizing edge. The measurements show that the portion of the liquid mass flow atomized remains relatively small and that the droplet sizes are equivalent to those produced at the atomizing edge.

Fluid dynamics in double venturies of carburetor (3rd report, Fuel atomization and its effect on air flow resistance)

The observation of fuel atomization and the measurements of fuel droplets are performed to examine the spray flow in the double venturies of carburetor, which is the interaction process between spouted fuel and air flow. Based on the above results, the spray transportation in the small venturi is analized using one dimensional model. It is concluded that the unbalancing by fuel spout in pressure between small venturi and large venturi is not caused from the evaporation of fuel or momentum losses of air flow, but from the change of the air flow pattern.

COM及びSRC-IIを燃料とした場合のディーゼル機関の燃焼と性能

Coal is considered one of the major fuels alternative to petroleum. The possibility of its use in combustion engines is particularly great in marine engines, and its use could reduce fuel costs considerably.This paper presents the engine performance and exhaust gas emissions with Coal Oil Mixtures (COM; in the experiment carbon black was used instead of coal slurry) and Solvent Refined Coal-II (SRC-II) as diesel fuel substitutes. Properties of the fuels when blended with diesel fuel and their spray characteristics are also presented.The results of the experiment show that specific heat consumption and exhaust smoke were improved when 5w-% carbon black or 25v-% SRC-II were blended with the diesel fuel. However engine noise and NOx emissions increased with the increase in the carbon or SRC-II ratio in the fuel. The analysis of the indicator diagrams show that these fuels result in larger premixed combustion and shorter combustion duration compared with conventional diesel fuels.Both COM and SRC-II have higher viscosity than diesel fuels; the paper shows their viscosities in empirical formula as a function of the blending ratios. In spite of the higher viscosities, the spray atomization of these alternative fuels was better than diesel fuel.

Guest Editorial Particle Sizing And Spray Analysis

The measurement of particle size and velocity in particle laden flows is a subject of interest in a variety of industrial applications. In combustion systems for electricity generation, industrial processes and heating, and transportation, where liquid and solid fuels are injected into air streams for burning in furnaces, boilers, and gas turbine and diesel engines, the initial size and velocity distributions of particles are determining factors in the overall combustion efficiency and the emission of pollutants and particulates. In the design of injectors and burners for the atomization of liquid fuels, a great deal of attention is being focused on developing instrumentation for the accurate measurement of size and velocity distributions in sprays as a function of space and time. Most recent advances in optical engineering techniques using lasers for particle measurement have focused on detailed spray characterization, where there is a major concern with spherical liquid droplets within the size range of 1 to 500µm in diameter, with droplet velocities within the range of 1 to 100 m/s, and the requirement for making in situ measurements of moving particles by nonintrusive optical probes. The instruments being developed for spray analysis have much wider applications. These include measurement in particle laden flows encountered in a variety of industrial processes with solid particles in gas and liquid streams and liquid particles in gas streams. Sprays used in agriculture, drying, food processing, coating of materials, chemical processing, clean rooms, pharmaceuticals, plasma spraying, and icing wind tunnels are examples of systems for which information is being sought on particle and fluid dynamic interactions in which there is heat, mass, and momentum transfer in turbulent reacting flows.

Nozzle Exit Flow Characteristics for Square-edged and Rounded Inlet Geometries

Abstract This study was conducted to provide some insight into effects of nozzle inlet shape on turbulent flow characteristics. It was motivated by the recognized importance of nozzle geometry on atomization and subsequent combustion of liquid fuels. Flow coefficient and nozzle exit turbulence data have been obtained with incompressible air flow in two nozzles having rounded and and square-edged inlet geometries respectively. Photon correlation laser Doppler velocimetry was used to measure the mean velocities and turbulence intensities. For operation with equal mass flow rates, the square-edged inlet nozzle requires a greater pressure drop and produces higher turbulence intensities than a nozzle with a well rounded inlet. The higher turbulence level which we observed with the square-edged inlet nozzle correlates with wider spray dispersion angles observed by Reitz and Bracco (1979) as the nozzle inlet radius is decreased.

Fuel atomization for spray modelling

This paper presents a review of the fuel spray models and discusses the problem of atomization since they affect spray modeling and combustion chamber design. Various experimental methods for determining droplet size distribution are also included in the review. 74 refs.

Airblast Atomization of Alternative Liquid Petroleum Fuels under High Pressure Conditions

A study has been conducted of the effects that fuel and air properties have upon the mean droplet size characteristics of a pre-filming airblast atomizer of the type commonly employed in the gas turbine engine. The fuels tested included kerosine, gas oil and two blends of gas oil in residual fuel oil. The tests were carried out over a wide range of air pressures (about 1 to 13 atmospheres), fuel viscosities (about 0.001 to 0.037 Ns/m2) and the spray mean drop sizes were measured using a laser light-scattering technique. The experimental data accumulated in the study is presented in the paper and it is concluded that the spray Sauter Mean Diameter performance of the atomizer studied can be predicted to a reasonable degree of accuracy, over the range of conditions studied, by a relatively simple correlating equation.

Some Practical Advance in Fuel Atomizer

Practical problems in the atomizer used in the conbustion systems are reviewed and some technical improvements which were recently carried out in Ishi-kawajima-Harima Heavy Industries Co. Ltd. are described.Spilit flame burner. The burner was developed to reduce NOx emission by means of minor modification of cobustionm system, and is characterized in its fuel atomizer. The burner with grooved tip atomizer, a typical type of the burner, which has afew grooves at the opening of the atomizer tip forms split flame and yields lower NOx than the conventional burner.Air blast atomizer. A new air blast atomizer named AFIT was developed to improve the combustion efficiency at the low load condition of jet engine. The test results of the AFIT combustor showed higher combustion efficiency at the low load codition and lower NOx emission at the high load condition than the conventional combustor which has the swirl type pressure atomizer.Carbon deposit. In the development test of a gas turbine combustor, it was found that the circumferential uneveness of the fuel spray caused a local carbon deposit on inside the liner.Atomizer life. In a field test it was found that the atomizer tips installed on a large boiler were often heated up to the annealing temperature of the metal, and these tips were remarkably weared by the fuel flow. The combustion test results of the weared atomizer tips showed the deterioration of combustion characteristics.

Fuel atomization in a flowing airstream

parison of the location of the supersonic pocket and shock calculated by the relaxation method and obtained from the shadowgraphs of Fig. 1 is presented in Fig. 2. The shape of the shock is predicted correctly, but the location of the shock obtained experimentally is shifted some distance downstream. The surface pressure calculated by the relaxation method is compared with the experimental data for M^ from 0.7 to 1.0 in Fig. 3. The theory predicts the pressure distribution correctly from the nosetip until the point at which the shock seems to appear. For M& =0.8 there is significant disagreement between the theoretical and experimental pressure distributions. The corresponding shadowgraph given in Fig. 2 does indicate a pronounced boundary-layer separation; therefore, the inviscid theory fails to work there. For M^ = 1, it is surprising to see the good agreement between the predicted and measured surface pressure. In conclusion, from experimental and theoretical results it is shown that an interaction of boundary-layer separation and shock waves strongly influences the flow over a hemispherecylinder in the transonic Mach number range; therefore, the inviscid theory fails to predict the flow. Such interaction is particularly strong when M^ ~ 0.8. Further study, both theoretical and experimental, is required to have a better understanding of the flow.

Electorostatic Atomization of Liquid Fuels

Experiments have been performed to define the influence of d. c. high voltage on liquid fuel atomization by existing fuel spray systems, such as a carburettor and a pressure spray nozzle. Studies of electrostatic spray at quasistatic states were made over a wide range of applied voltages and showed that liquid fuels were atomized by electrification at high voltage, although a fuel atomizing rate was very slight.Fuel droplets atomized by the spray systems with an electrode were intercepted on the sampling pad or liquid. The distribution of droplet size has been yeiled to investigate the effect of applied voltage. It was found that applying high voltage improves fuel atomization and decreases the mean diameter of droplets and its standard deviation. The droplet size depends on quantity of electricity charged on it and is independent of fieldpolarity.A result of practical importance confirmed by experiment is that the shape and arrangement of electrodes should be determined so as to increase the quantity of electricity charged on the fuel liquid. The effects of high voltage were limited by a sparking voltage between nozzle and applied electrode.

Measuring Method for Spray Characteristics of a Fuel Atomizer under Arbitrary Conditions of Ambient Gas

Measuring Method for Spray Characteristics of a Fuel Atomizer under Arbitrary Conditions of Ambient Gas

Paper N–6: Photomicrographic Study of Atomization of Liquid Fuels within a Combustion Chamber

Paper N–6: Photomicrographic Study of Atomization of Liquid Fuels within a Combustion Chamber

Atomization, acceleration, and vaporization of liquid fuels

The Doppler-Mie combination technique was examined as one of the methods to obtain the distributions of diameters and velocities of droplets simultaneously as well as their mutual correlation in a burning or nonburning spray with fine discrimination in space but without disturbing the two-phase flow field. Attention was focussed on the technique of correcting the errors which inevitably occur in optical systems measuring size distribution of droplets, especially in those utilizing laser beams. A method for deriving correct probability density distributions in the velocity-diameter field from raw data involving errors in diameter values was developed. This technique was applied to burning or nonburing sprays injected from an ultrasonic atomizer. The size distributions of droplets obtained by this technique were in fair agreement with those obtained by the magnesium oxide method in diameter range between 20 and 80 μm. It was also found that velocities of droplets were distributed over a wide range regardless of their sizes.