Kerosene Droplets Research Articles

Characteristic evolution and energy variation during the generation of kerosene droplet

Understanding the generation behavior of kerosene droplets is an important precursor for predicting the kerosene-mineral adsorption. Using a high-speed motion acquisition system, we investigated the thermodynamic and kinetic characteristics of kerosene droplet with different size capillaries. As the capillary inner diameter increased, the formation time of the kerosene droplet become longer, and the width/height value decreased. The width/height value of the kerosene column roughly increased as the capillary inner diameter decreased due to the variation in the buoyancy, gravity and surface tension. The kinetic energy per unit superficial area (Ek/S) of the kerosene droplet firstly decreased sharply as the capillary inner diameter increased and then remained almost constant. The energy barrier on the kaolinite, quartz, montmorillonite and coal surfaces was found easy to be overcome by Ek/S independently of capillary inner diameter, and the energy barrier on the mica surface could be overcome if the capillary inner diameter was smaller than 0.50 mm. A predictive model of the formation condition of deuterogenic kerosene droplet was established, and the critical capillary inner diameter for forming a deuterogenic kerosene droplet was predicted to be approximately 0.29 mm. This aspect of kerosene droplet characteristics has not been well represented in the earlier literature. The results can provide valuable insight into the development of technology for surfactant adsorption and mineral flotation.

Single droplet ignition models via evaporation and ignition competition

There is individual droplet burning phenomenon in spray flames but the ignition prediction and criteria are lack of both experimental and theoretical study. In this paper, firstly based on the energy balance analysis method, two new droplet ignition models are proposed by analyzing the single droplet evaporation and ignition process in relatively static high temperature air environment. These new models can be used to predict the droplet ignition phenomenon in spray flames. Then, single droplets of RP3 aviation kerosene, common kerosene and diesel were suspended in static air environment with ambient temperature from 845 ​K to 1085 ​K to test the ignition limits of the fuel droplet. The experimental ignition boundary was obtained by measuring and recording the minimum ignitable initial diameters of the experimental droplet in every temperature condition. The experimental results show that the ignitable minimum initial diameter of the fuel droplet decreases along with the increase of ambient temperature. And at the same ambient temperature, the minimum ignitable initial diameter of common kerosene droplet is the biggest, then is diesel and RP3 aviation kerosene is the smallest. Finally, the predicted ignition boundaries of the two new models are compared with the experimental data. And the comparison results show that the models’ predictions are in good agreement with the experimental data, whose error is within 10%.

Laser diagnostics of atomization and combustion of kerosene in a model combustion chamber

The experimental results are presented of implementation of a built-up laser-based diagnostic system at a test rig for investigations of the flame tube heads of aircraft gas turbine engines, both existing and being under development. At this test rig the processes of liquid fuel atomization and mixing with air by flame tube heads of model combustion chambers equipped with newly-developed atomizers, and of combustion of the fuel–air mixture formed in the flow have been studied. These studies enable development and optimization of advanced low-emission engines satisfying the established environmental requirements for the levels of polluting species in the exhaust gases. By using the particle shadow velocimetry technique with a pair of 10 μs delayed 5 ns laser pulses the transverse spatial distributions of average kerosene droplet dimensions, the axial components of their average velocity, and of the average volume flux of the fuel have been measured in the mixture flow axial cross-section. By employing coherent anti-Stokes Raman scattering with 10 ns pump laser pulses at 10 Hz repetition rate during combustion of the produced kerosene–air mixture the statistical characteristics of local ‘instantaneous’ gas temperature fluctuations in the flame, slow variations of these temperatures in time during the combustion process, and transverse distributions of average temperatures in the flame axial cross-section have been measured.

Evaporation and Combustion Characteristics of Kerosene Droplets in Localized Stratified Vortex-tube Combustor: A Numerical Investigation

ABSTRACT The combustion of AC10H20 droplets was investigated to explore the combustion performance of liquid fuels in localized stratified vortex-tube combustor (LSVC). The evaporation ratio, flame structure, stability limit, heat loss, and combustion efficiency in the LSVC were investigated under various equivalence ratios and fuel mass fluxes numerically. Results corroborate that the LSVC exhibits a large heat release with uniform flame front, large stability limit, low heat loss, high evaporation rate, and good combustion efficiency under lean operating conditions, indicating good potential to deal with liquid fuels directly. Then, the evaporation and stabilization mechanisms are analyzed. As for the former, the evaporation ratio in LSVC increases sharply along the axial direction toward the outlet, indicating a high evaporation rate, which is optimized through the heat produced by itself efficiently. Viz., the vortex currents can entrain the AC10H20 droplets to interior high-temperature region and then promote the evaporation of liquid fuels. As for the latter, the localized stratified distribution of species in the LSVC results in an edge flame structure, which differs from that in the traditional vortex-tube combustors. The local equivalence ratio increases along the radial direction toward the center. The increased local equivalence ratio of the interior is crucial for stabilization and the decreased local equivalence ratio of exterior enables the heat loss to be reduced. In the end, the edge flame structure and the low heat loss yields a large heat release in the LSVC, which can increase the flame speed, thereby ensuring the stabilization and the high burn-off rate.

Emulsification of kerosene and its effect on the separation of unburned carbon from fly ash

ABSTRACT This type of fly ash is difficult to float even at a higher concentration of collector due to less dispersion of the collector molecules on the surface. Emulsification of kerosene in the presence of Sodium Dodecyl Sulfate (SDS) dramatically reduces the size of the kerosene droplets. The results showed that much less collector was required to achieve a good separation of carbon from fly ash when SDS was employed in conjunction with the collector. In this paper, the influence of the concentration of emulsifier on flotation was discussed. The emulsifier concentration of 0.2 kg/t produced the superior performance of LOI of 54.5% and the corresponding CR of 93.1%. The contact angle and attachment efficiency of CFA after pretreatment were found to be increased. The results of XRD and SEM demonstrate that a complete separation of unburned carbon from CFA could be achieved by using the emulsifier.

Ignition, puffing and sooting characteristics of kerosene droplet combustion under sub-atmospheric pressure

The ignition, puffing and sooting characteristics of Chinese RP-3 kerosene droplet burning have been studied using high-speed, OH* chemiluminescence and soot thermal radiation imaging. The experiments were conducted in air at standard temperature and sub-atmospheric pressures ranging from 0.2 bar to 1 bar. The kerosene droplet was supported by a thermocouple tip and ignited by a retractable coiled heating wire. The results showed that the ignition delay time increased with a decrease of the ambient pressure, due to an increased distance between kerosene and oxygen molecules. Steady burning and disruptive burning were identified following the ignition. OH* chemiluminescence images showed a spherical flame and a longer flame standoff distance under a lower pressure. The puffing intensity was observed to be enhanced with a reduction of the ambient pressure, and a decreased pressure was found to lower the sooting emission.

Mathematical model and calculation results of the kerosene aerosol combustion rate

This paper presents a mathematical combustion model of the kerosene aerosol and the calculation results of the combustion front normal velocity. The model is based on the dynamic equations of the two-phase reacting medium and consists of the energy equations for the gas and kerosene droplets, taking into account heat exchange, evaporation and heat release from the kerosene-oxygen reaction in the air; mass conservation equations for the gas, droplets, oxygen and kerosene, controlling the mass exchange between the phases and the burning of the reagents; the motion equation of the droplets; the particle number equations for the of droplets per unit volume; the ideal gas equation. The model assumes the isobaric conditions of the aerosol combustion. The obtained (calculated) propagation velocity of the kerosene aerosol combustion front, depending on the kerosene mass concentration and the initial temperature of the mixture, is in good agreement with the experimental data.

Modelling of multi-component kerosene and surrogate fuel droplet heating and evaporation characteristics: A comparative analysis

A Discrete Component Model (DCM) is applied to study the heating and evaporation of suspended kerosene and kerosene surrogate droplets. The effects of natural convection are taken into account using the Churchill approximation, whilst the effects of heat addition from the supporting fibre are modelled using the assumption that heat supplied via the fibre is uniformly distributed within the droplet volume. The results of taking into account and ignoring the above effects are investigated. It is shown that the effect of supporting fibre can be ignored in the analysis of these droplets. In contrast, the effect of natural convection cannot be ignored. The time evolution of droplet radii predicted by the DCM, taking into account the effects of natural convection and supporting fibre, is shown to be close to experimental predictions of this parameter for gas temperatures in the range 500 °C to 700 °C. The heating and evaporation of kerosene droplets are compared with those for droplets of various kerosene surrogate fuels, including eleven surrogate fuels proposed in the literature, and two original compositions. Considering the balance between the heating and evaporation characteristics of droplets we conclude that those of the original surrogate SU1 and the modified Utah surrogate are the closest to those of kerosene droplets.

Numerical Investigation of Influence of Flow Rates on Combustion Characteristics using Multiphase Flamelet Combustion

Numerical analysis plays vital role in designing gas turbine combustors for improving its performance. It requires deep understanding of turbulent and multiphase reactive flow physics inside the combustor. Hence present work focusses on numerical investigation of turbulent flow and reactive interaction between liquid spray of aviation kerosene droplets and air for the experimentally investigated combustor configuration. The present analysis results agree well with the experimental test results. Mixture fraction based Probability Density Function flamelet combustion model is used to solve transport equations by generating the flamelet library for Jet-A fuel. The analysis provides good insight into the multiphase combustion process and the flow phenomena occurring inside the combustor. Further, combustion performance characteristics at different design point operations are investigated in the present work keeping the air fuel ratio constant. Results show rise in peak velocity by 2.5 times and pressure loss factor by 6 for design point operating at higher flow rates in comparison with the baseline design operating point.

Floc-Flotation of Malachite Fines with an Octyl Hydroxamate and Kerosene Mixture

Malachite fines are easily produced in the grinding process, leading to low malachite flotation recovery. Floc-flotation of malachite fines with an octyl hydroxamate and kerosene mixture was studied to improve the flotation recovery, using microflotation, microscopy image observations, contact angle measurements, and Extended Derjguin–Landau–Verwey–Overbeek (EDLVO) analysis. The results showed that the addition of octyl hydroxamate as an emulsifier of kerosene enhanced the aggregation of malachite fines and improved malachite flotation recovery. In addition, when kerosene droplets were smaller and of uniform size distribution, the spreading of kerosene droplets on the malachite surface improved. The enhanced spreading of kerosene droplets led to higher coverage of kerosene on the malachite surface, resulting in improved hydrophobic aggregation and flotation recovery.

Numerical Simulation of the Flowfield in a Boron-Based Slurry Fuel Ramjet

By considering the parametric variation of an individual boron particle in a boron agglomerate, the heat transfer, and the mass transfer between the boron particle agglomerate and the surroundings, an ignition and combustion model of a boron agglomerate is proposed. An experiment of a ramjet combustor using a boron-based slurry fuel is designed and operated for the purpose of validating the ramjet configuration and verifying the combustion of boron particles. Then a mathematical model for simulating a multiphase reacting flow within the combustor of a boron-based slurry fuel ramjet is established. Kerosene droplets and boron particles are injected discretely to the burner flowfield, and their trajectories are traced using the discrete phase model. The influence of the agglomerate size, bypass air mass flow rate, initial boron particle diameter, and boron particle content on the combustion efficiency of the slurry fuels is analyzed in detail. The results show that the combustion efficiency decreases with an increase in the agglomerate radius, initial boron particle diameter, and boron particle content. The combustion efficiency increases with an increase in the mass flow rate of bypass air. If the agglomerate diameter is greater than 100 μm or the bypass air mass flow rate is smaller than 50 g/s, the boron particles cannot be fully burned.

Numerical investigation of flame appearance and heat flux and in a deep-throttling variable thrust rocket engine

Much attention has been drawn to liquid-propellant rocket engine with thrust that can be varied on demand in recent years. A GO2/kerosene deep-throttling variable thrust rocket engine using the newly proposed gas-liquid pintle injector is presented. Three-dimensional numerical simulations are conducted to investigate the flame appearance and heat flux distribution of the engine. The SST k-omega model is used for modeling turbulence and single-step finite-rate kinetics are used for modeling combustion. A grid sensitivity study is performed to examine the validity of the simulation results. The effects of total mass flow-rate, kerosene droplet injection velocity and kerosene droplet size distribution on flame appearance and heat flux distribution of the combustor are studied in detail. Three entirely different flame appearances are observed and it correspondingly causes different heat flux distributions. Details of the flow field structure and mass fraction contour inside the combustor are discussed to explore the cause of heat flux distribution. The work will provide a reference for the design of thermal protection system of the variable-thrust rocket engine operating with a wide range of space.

Модель испарения капель керосина в атмосфере и загрязнения грунтов приаэродромной территории

Модель испарения капель керосина в атмосфере и загрязнения грунтов приаэродромной территории

Combustion of rocket-grade kerosene droplets loaded with graphene nanoplatelets—A search for reasons behind optimum mass loadings

Nanofluid-type fuels formulated by mixing minute quantities of graphene nanoplatelets (GNPs) with Isrosene, a refined form of kerosene utilized in semi-cryogenic engines by the Indian Space Research Organization (ISRO), were found to improve the convective heat transfer characteristics by 49% in a previous study. In this study, the combustion characteristics of such nanofluid-type fuels, such as initial mass burning rates, burning rate constants, and flame stand-off ratios, were determined for millimeter-sized droplets under ambient conditions. The impact of the specific surface area of the nanoplatelets and their relative mass loading in the nanofluid was determined. While the specific surface area did not have any impact on the combustion characteristics, the relative mass loading had a strong impact on the burning rate constants, with an increment of approximately 13.5% over Isrosene for a mass loading of 0.2%. There also existed an optimum value of mass loading, beyond which the burning rate constants. This anomalous behavior, which had earlier been conjectured to be due to various physico-chemical reasons, was attributed primarily to the gas phase conduction phenomenon, corroborated by the analysis of the temperature profiles in the gas phase, acquired using an infrared imaging camera.

Combustion characteristics of inorganic kerosene gel droplet with fumed silica as gellant

Gelled fuel has gained extensive attention because of combination of the main advantages of liquid fuel (throttle ability) and solid fuel (easy handling, etc.). For investigating the combustion characteristics of gelled fuel formed by inorganic gellant, several kinds of kerosene gels were prepared by adding fumed silica as gellant. Suspended single droplet combustion experiment was carried out under normal gravity conditions at room temperature. Experimental observations were compared with pure liquid fuel and organic-gellant-based gel fuel. Under ambient pressure condition, special combustion phenomena occur during the combustion process of an inorganic gelled kerosene droplet, such as the formation, shrinkage and exfoliation of a rigid shell surrounding the droplet. The combustion stability is inferior to pure liquid fuel but superior to organic gels. The pattern of droplet diameter variation basically obeys the d2-law in the early period; the combustion rate of inorganic gel fuel decreases with the increasing of gellant content according to the law. In the late period diameter change deviates from the law because of the incombustible residual gellant. We believe that the combustion rate becomes higher in the later period because the higher thermal conductivity of fumed silica than kerosene vapor enhances the intensity of reverse heat transfer. Unlike organic gels, the ignition delay time and total survival time of inorganic kerosene gels are shorter than that of kerosene, which facilitates the rapid response and shortening the residence time of the fuel in the combustion chamber.

Migration and Evaporation Characteristics of Kerosene Droplet in Supercritical Environment

A one-dimensional full transient droplet evaporation model was established under consideration of factors such as high pressure vapour-liquid equilibrium, high-pressure physical property corrections, gas phase dissolution, and shift of interface. The finite volume method was used for discretization to study the migration and evaporation characteristics of the surrogate fuel for kerosene, which was constituting of (mass fraction)80% n-decane and 20%1,2,4-trimethylbenzene, under supercritical conditions. The results show that, under supercritical conditions, the higher the temperature and the pressure, the easier and the sooner the supercritical migration occurs. Before the supercritical migration occurring, there was obvious boundary between the gas and liquid phases. The mass fraction of component was discontinuous, and the gradient of temperature near the interface was large. After the supercritical migration occurring, the surface of the droplet disappeared, there was no obvious boundary between the gas and liquid phases, and the distribution of the components mass fraction and temperature were continuously. With the increase of the initial temperature of the droplet, the time of the supercritical migration was greatly advanced, the rise rate of the droplet surface temperature increased, and the phenomenon of endothermic expansion no longer appeared.

The effect of demulsifier on the stability of liquid droplets: A study of micro-force balance

An original device was developed by our research group and used for quantitatively and qualitatively studying the stability mechanism of two liquid droplets in another liquid phase. The squeeze time can be employed to detect the stability of liquid droplets. The effect of water soluble emulsifier TX-100 and oil soluble one Span-80 on the squeeze times of both aqueous and kerosene droplets have been investigated. Moreover, the influences of three polyether demulsifiers with different structures, linear PEL, branched PEB and star-type PES, on the stability of liquid droplets have also been studied. Based on experimental results, the hydrophilic head group ethoxylation (EO) chain of TX-100 nearly flats at interface and forms compact interfacial film closed to water phase, which makes kerosene droplets stable at aqueous. On the other hand, two water droplets contain TX-100 will coalesce at once when they contact each other. For oil soluble emulsifier Span-80, the compactness of two sides of interfacial film leads to both stable water droplets and oil droplets. The molecular size of demulsifier may play the crucial role in controlling droplets coalescence: PEL with smaller size can easily destroy aqueous droplets in oil; PEB shows strong effects on both kerosene and aqueous droplets for it has a moderate molecular size; PES with larger size shows strong ability to destroy oil droplets in aqueous but little effects on aqueous droplets in oil.

Numerical investigation on evaporation characteristics of kerosene droplets with dilute concentrations of aluminum nanoparticles at elevated temperatures

We have numerically investigated the problem of kerosene droplets evaporation with dilute concentrations of aluminum nanoparticles at elevated temperatures. The aim of the research was to develop a mathematical model describing the evaporation process and obtain numerical simulation data which is in good agreement with an experimental data. The dependences of kerosene droplet evaporation time on its initial diameter and ambient temperature are presented in this paper.

Electric field assisted transport of dielectric droplets dispersed in aqueous solutions of ionic surfactants.

Motion of liquid droplets with a surface electric charge can be efficiently controlled by dc electric field. Here, we show that the surface of a dielectric kerosene droplet can be charged by the addition of ionic surfactants to a surrounding aqueous electrolyte. The direction of droplet motion is determined by the polarity of the surfactant charge and the orientation of the imposed electric field. We have found that the effective electrophoretic mobility of dielectric droplets in a confined channel is directly proportional to the logarithm of the surfactant concentration even for values significantly exceeding critical micelle concentration (CMC). We attribute this finding not only to adsorption of ionic surfactants to the surface of dielectric droplets but also to the weakening of electro-osmosis at channel walls due to the increase of ionic strength in the aqueous phase. Our findings can be exploited in microfluidic reactors and separators for on request dosing, sampling, and separation of dielectric fluids.

Analysis of Flow Field and Spray Characteristics of a Lean Premixed Injector in Low Emission Combustor of Industrial Gas Turbine

A lean premixed injector designed by the authors provides a solution for achieving the goal of high efficiency and super low emission combustion in industrial gas turbine. The present work lays out a series of injector structures to investigate their flow and atomization characteristics. To facilitate the analysis, laser measurement technologies such as Particle Image Velocimetry (PIV) and Particle Dynamics Analyzer (PDA) are applied to experiments. A typical and reasonable flow field is revealed since Primary Recirculation Zone (PRZ) and Corner Recirculation Zone (CRZ) are clearly observedin PIV experiment results. The angle of main swirl blades is main parameter to affect flow field, in which the swirl angle, axial velocity, radial velocity, location of PRZ all will change. Atomization test shows that Sauter Mean Diameter (SMD) of kerosene droplets is less than 40μm in downstream cross section 10mm away from lip. Unique aspects of this study play a pivotal role of application before this injector is installed in low emission combustor. of industrial gas turbine.