Fuel Vapor Research Articles

Two-tracer LIF imaging of preferential evaporation of multi-component gasoline fuel sprays under engine conditions

A laser-induced fluorescence (LIF) technique capable of imaging the effects of preferential evaporation of multi-component fuels was developed based on the simultaneous detection of two aromatic fluorescence tracers with complementary evaporation characteristics matched to different components of a multi-component fuel. Relative variations in the spatial distribution of fuel components as a consequence of preferential evaporation were determined from the ratio of LIF-signals measured within two distinct spectral bands. The accuracy and precision of the method was characterized from determining the LIF-signal ratio within two identical spectral bands. Measurements were performed in a high-pressure high-temperature vessel equipped with a hollow-cone injector. Experimental conditions with temperatures up to 700K were chosen that are representative for engine environments and favor preferential evaporation. The effects of preferential evaporation were analyzed based on the comparison of instantaneous and mean images of LIF ratios obtained at various temperatures. Variations in the spatial distribution of the fuel volatility classes were observed up to 550K.

Study of Hot Surface Aviation Fuel Thermal Ignition Pattern

Fuel evaporation and ignition process on the high-temperature hot surface are difficult to be predicted accurately. The rule of fuel evaporation and ignition delay that various with hot wall temperature have been obtained by utilizing the simulated experiment to study the evaporation and ignition process of aviation fuel on hot surface. This study complements the related content of the fuel ignition mechanism on hot wall,at the same, reference method for fuel fire engineering practice has been provided.

Coadsorption Equilibria of Automotive Fuel Vapors on Wet Activated Carbon Filters

AbstractKraftstoffdampf‐Rückhaltesysteme in PKWs enthalten gewöhnlich einen Aktivkohlefilter an dem die flüchtigen Kraftstoffkomponenten adsorbieren. Kurz vor Durchbruch dieser Stoffe wird die Zufuhr der Dämpfe unterbrochen und der Filter mithilfe von Umgebungsluft regeneriert. Da die Luft feucht ist, wird untersucht, ob im langjährigen Betrieb Wasser auf dem Filter kumuliert und so die Beladekapazität und Funktionsfähigkeit beeinträchtigt wird. Die Kosorptionsgleichgewichte von Wasser und n‐Pentan auf Aktivkohle wurden gemessen. Die Gemischbeladungen weichen nur wenig von den Summen der Reinstoffbeladungen beider Komponenten ab. Auch bei extremer Vorbefeuchtung der Kohle ist nur eine geringe Reduktion der Pentanbeladungskapazität zu beobachten.

Numerical investigation of VOC levels in the area of petrol stations

In the area of petrol stations several Volatile Organic Compounds (VOCs) leak into the atmosphere due to the evaporation of liquid fuels, especially of gasoline that is predominantly composed of light hydrocarbons. The aim of the present study is to investigate the spatial distribution of various VOCs when leaked into the atmosphere in the area of a petrol station. The study is based on numerical simulations. The effect of wind speed and direction, as well as of air temperature has been studied. Gasoline components of different properties have been studied (e.g. pentane, iso-octane, o-xylene, toluene, benzene), as well as ethanol that is considered a new fuel blend component that can be found in different fractions in new gasoline blends worldwide. The area of flammable cloud near the source of the leak is investigated for various atmospheric conditions taking into account the lower and higher flammable limits of each compound. Lastly, the exposure to gasoline vapour is studied taking into consideration the recommended occupational exposure limits of various organisations.

Bio-fuel reformation for solid oxide fuel cell applications. Part 1: Fuel vaporization and reactant mixing

A new configuration of a mixing chamber integrated with a customized porous nozzle has been developed to completely vaporize heavy hydrocarbon fuels (e.g., diesel, biodiesel) and achieve homogenous mixing of fuel/air/steam. This proposed configuration suppresses hydrocarbon thermal pyrolysis and solid carbon formation in the fuel vaporization step. The porous nozzle promotes the micro-explosion of emulsified fuel and accelerates secondary atomization to reduce the droplet size. The mixing chamber with customized nozzle was integrated in a single-tube reformer system in order to analyze its effect on diesel and biodiesel auto-thermal reforming (ATR). It has been demonstrated that the customized nozzle not only improved the hydrogen production rate and the reforming efficiency, but it also stabilized the chemical reactions within the reformer and prevented the reactor inlet from high temperature sintering. For diesel ATR, this mixing chamber–reformer combination enabled operation at relatively low reformer temperature without forming solid carbon. This study is one component of a three-part investigation of bio-fuel reforming, also including biodiesel (Part 2) and biodiesel–diesel blends (Part 3).

Effects of size on combustion of isolated methanol droplets

Results are presented from numerical simulations of the combustion process of an isolated methanol droplet in a nearly quiescent ambient air (T∞=1200K, and p∞=1atm.). The focus is on the effects of size variation for droplets which are present in a practical spray. We show a gradual transition from a kinetically controlled regime of small droplets to a diffusion controlled regime of large droplets. The analysis underlines the importance of accurate chemical kinetics, especially for small droplets. With reduction in the droplet size, the flame-sheet approximation breaks down, and the flame becomes a larger reactive zone relative to the droplet, along with a concomitant reduction in the flame temperature. Fuel vapour accumulation and depletion affects the entire burning history significantly, and combustion characteristics, such as gasification rate, and flame stand-off ratio are time dependent, with increasing unsteadiness with reduction in size. Extinction diameters are found based on the sudden movement of the flame relative to the droplet. The effect of the initial droplet diameter and ambient temperature on the extinction diameter is presented. The main differences in the internal circulation flow fields for a large and a small droplet are presented.

Two-Phase Flow Heat and Mass Transfer Model Construction and Experiment Study of the Fuel Evaporation Progress

As for the time-dependent behavior of the fuel heat and mass evaporation transfer progress on hot surface,consider the convective mass transfer and heat transfer, the liquid-gas two-phase flow of continuous heat transfer model was studied. By the dimensionless transform, the time-dependent behavior of the concentration distribution and the temperature field was obtained. The result of n-Heptanes evaporation transfer progress on hot surface experiment is consistent with the academic model.

The Effects of Fuel Evaporation and Biomass Burning on Toluene Concentrations in an Urban Area

Using an automated gas chromatography system coupled with an online sampling/thermal desorption module, benzene, toluene, and their alkylated derivatives were measured in Las Vegas, Nevada from 3 July to 28 August 2008. The levels of hydrocarbons were comparable to those typically found in urban environments. Statistically significant (at 95 % level) higher concentrations were measured on mid-week days as compared with those measured during weekends. This was correlated to a local traffic pattern rather than traffic on highways. The concentrations of aromatic hydrocarbons also increased during periods when transport of smoke from wildfires in central and north California was identified by remote sensing but these levels were comparable to other days with volatile organic compounds concentrations. The high toluene/benzene ratios and the estimated photochemical age of air masses implied the contribution of other local sources. Fuel evaporation accounted for the vast majority of toluene enhanced concentrations in early July (as compared with those measured in June) for sites within the urban grid, but very little for sites located outside the urban area.

A CFD Study of Fuel Evaporation and Related Thermo-fluid Dynamics in the Inlet Manifold, Port and Cylinder of the CFR Octane Engine

A CFD Study of Fuel Evaporation and Related Thermo-fluid Dynamics in the Inlet Manifold, Port and Cylinder of the CFR Octane Engine

Burning rates of liquid fuels in fire whirls

This paper presents semi-empirical investigations on the quasi-steady burning rates of laminar and turbulent fire whirls established over liquid fuel pools. The inflow boundary layer above the fuel surface consists of two regions: outer reactive region and inner non-reactive region. Based on the momentum boundary layer solutions with the applications of stagnant film model and Chilton–Colburn analogy, the burning rates are correlated with ambient circulation and pool size for laminar and turbulent fire whirls respectively. It is shown that in general pool fires the mass and heat transfers on the fuel surface are controlled by natural convection, while in fire whirls they are strongly enhanced by forced convection. Fuel evaporation rate in the outer region is relatively larger than that in the inner region. The large proportion of fuel evaporated from the outer region is mainly due to its larger area. The predictions agree well with the data from the present experiments and the literature. Furthermore, the flame height is confirmed to be proportional to the ambient circulation for both laminar and turbulent liquid fire whirls.

203 燃料の蒸発で発生する青白煙に及ぼす蒸発温度の影響(エンジンシステムI)

203 燃料の蒸発で発生する青白煙に及ぼす蒸発温度の影響(エンジンシステムI)

Validation of an Infrared Extinction Method for Fuel Vapor Concentration Measurements Towards the Systematic Comparison Between Alternative and Conventional Fuels for Aviation

Due to increasing oil prices and the obvious influence of the combustion of fossil fuel-derivatives on climate change on the one hand and the steady growth of transportation needs on the other, it is necessary to develop alternatives to oil for aviation. For this purpose a specific research program on the investigation of adequate alternative fuels for aviation has been founded by the European Commission’s Framework Program. The project Alfa Bird (Alternative Fuels and Bio-fuels in Aircraft Development) focuses on an identification of possible alternative fuels to kerosene, the investigation of the adequacy of the selected ones, an evaluation of the environmental and economic impact of them, and finally the creation of a future perspective for the industrial use of the “best” alternative. The main part of the investigation activities at TU Graz, in cooperation with ONERA Centre de Toulouse and Fauga-Mauzac on these specific topics consists of the analysis of the evaporation of the previously chosen fuel types in comparison to fully synthetic jet fuel. Therefore qualitative measurements to obtain vapor concentration gradients will be done using the infrared extinction (IRE) measurement method. Based on a simplified Beer–Bouguer–Lambert law the integral vapor concentrations can be obtained. The main hypothesis is that if the line-of-sight extinction due to Mie-scattering is similar for both infrared and visible wavelengths because of the presence of the spray, only infrared light will be absorbed by the fuel vapor, being transparent to visible light. This contribution focuses on the validation of the infrared measurement technique on a well characterized spray. The tests are performed under controlled boundary conditions. Therefore an existing IRE test arrangement at ONERA Toulouse using an ultrasonic atomizer injecting n-octane at atmospheric conditions has been analyzed. Error sources related to misalignments in the hardware have been considered and an iterative alignment method of the laser beams followed by a beam diameter and diffraction analysis have been performed. Optimizing the setup to obtain a stable operation point has been successful. Improved experimental results at this operation point were compared with existing simulation results for the evaporation of the ultrasonic atomizer used. The achieved data has shown good accordance to the existing simulation results.

Surprising Formation ofp-Cymene in the Oxidation of α-Pinene in Air by the Atmospheric Oxidants OH, O3, and NO3

Anthropogenic sources release into the troposphere a wide range of volatile organic compounds (VOCs) including aromatic hydrocarbons, whose major sources are believed to be combustion and the evaporation of fossil fuels. An important question is whether there are other sources of aromatics in air. We report here the formation of p-cymene [1-methyl-4-(1-methylethyl) benzene, C6H4(CH3)(C3H7)] from the oxidation of α-pinene by OH, O3, and NO3 at 1 atm in air and 298 K at low (<5%) and high (70%) relative humidities (RH). Loss of α-pinene and the generation of p-cymene were measured using GC-MS. The fractional yields of p-cymene relative to the loss of α-pinene, Δ [p-cymeme]/Δ [α-pinene], were measured to range from (1.6±0.2)×10(-5) for the O3 reaction to (3.0±0.3)×10(-4) for the NO3 reaction in the absence of added water vapor. The yields for the OH and O3 reactions increased by a factor of 4-8 at 70% RH (uncertainties are ±2s). The highest yields at 70% RH for the OH and O3 reactions, ∼15 times higher than for dry conditions, were observed if the walls of the Teflon reaction chamber had been previously exposed to H2SO4 formed from the OH oxidation of SO2. Possible mechanisms of the conversion of α-pinene to p-cymene and the potential importance in the atmosphere are discussed.

High-pressure vaporization modeling of multi-component petroleum–biofuel mixtures under engine conditions

Numerical simulation of the vaporization of multi-component liquid fuels under high-pressure conditions is conducted in this study. A high-pressure drop vaporization model is developed by considering the high-pressure phase equilibrium which equates the fugacity of each component in both liquid and vapor phases. Peng–Robinson equation of state is used for the calculation of fugacity. To model the vaporization of diesel fuel under high-pressure conditions, continuous thermodynamics based on a gamma distribution is coupled with phase equilibrium by correlating the parameters of the equation of state with the molecular weights of the continuous components. The high-pressure vaporization model is validated using the experimental data of n-heptane drops under different ambient pressures and temperatures. Good levels of agreement are obtained in drop size history. Predicted results of the vaporization of diesel fuel drops show that increasing ambient pressure leads to a shorter drop lifetime under high temperature conditions (e.g., 900 K). On the other hand, at a slightly lower temperature of 700 K, the drop lifetime increases as the ambient pressure increases. It is found that the net affects of high ambient pressure on drop vaporization are determined by two competing factors, namely, reduced mass transfer number and reduced enthalpy of vaporization. The model was further applied to biodiesel and its blends with diesel fuel. The fuel blend is modeled based on a method that continuous thermodynamics is used to model diesel fuel and biodiesel is modeled as a mixture of its five representative components. Results of single drop vaporization history show that drop lifetime increases as the volume fraction of biodiesel in the fuel blend increases. This phenomenon reveals the low vaporization rate of biodiesel that has a higher critical temperature than diesel fuel. It is also observed that the volume fraction of biodiesel in the fuel blend increases during vaporization and its vapor concentrates near the tip of the liquid spray while diesel fuel vapor is around the entire liquid spray.

Distribution of Different Organotin and Organolead Compounds in Sediment of Suez Gulf

Organotin and organolead compounds were determined in sediments of the Suez Gulf The concentrations of Tributyltin (TBT) ranged from 0.27 to 2.77 with an average value of 1.37 µgg-1; dry wt. However, the concentrations of dibutyltin (DBT) ranged from 0.07 to 2.27 with an average value of 0.58 µgg-1; dry wt. A significant correlation was found between TBT and DBT with r = 0.82, (p = 0.05) indicating that the occurrence of DBT is mainly related to the degradation of TBT. Generally, the high concentration of TBT was attributed to shipping activity in harbours. In addition, Diphenyltin (DPhT) concentrations ranged from not detected to 2.09 with an average of 1.10 µgg-1 dry wt. Antifouling agents, industrial discharge and the influence of sewage discharge are the main sources of pollution by DPhT compounds in Suez Gulf. On the other side, organolead (OLC) concentrations ranged from 10.88 - 440.2 with an average of 168.7 ngg-1; dry wt. A significant setting of OLC recorded in sediments of Suez Gulf was mainly attributed to cars exhaust and/or spelling and direct evaporation of fuels.

G060063 赤外吸収法を用いた燃料液滴近傍の燃料蒸気濃度計測([G06006]熱工学部門一般セッション(6)二燃焼の分光計測および輻射)

G060063 赤外吸収法を用いた燃料液滴近傍の燃料蒸気濃度計測([G06006]熱工学部門一般セッション(6)二燃焼の分光計測および輻射)

Radiation blockage in small scale PMMA combustion

Fuel vapors, soot and products of combustion near a burning fuel surface often block much of the radiative heat feedback to the fuel surface of a burning object. The blockage phenomenon was clearly observed in experiments of small 9.5 cm diameter PMMA pool fires subjected to external radiation burning in ambient atmospheres of different oxygen concentrations. The measurements are explained by a one-dimensional model of a diffusion flame, which focuses on the radiant absorption and emission of the soot–gas mixture of the flame. An approximate Band Model was developed and inserted into Radcal to compute gas absorption and emission from MMA vapor, CO 2 and H 2O. The Radcal results are included in the one-dimensional diffusion flame model to provide a greater understanding of the radiation blockage and burning rates in various ambient atmospheres and externally imposed radiant heat fluxes. A comparison between experimental data and model prediction shows a good agreement.

Structure of evaporating single- and multicomponent fuel sprays for 2nd generation gasoline direct injection

In the present paper the effect of fuel properties on spray formation and evaporation was investigated for a hollow-cone spray of a piezoelectric injector for Direct Injection Spark Ignition (DISI) engines. Late injection timing in a high-pressure atmosphere (1.5 MPa, 200 °C) was simulated in an injection chamber. Liquid and vapor phase structure of the hollow-cone spray were studied with 2D-Mie scattering, laser-induced fluorescence (LIF) as well as phase-Doppler anemometry (PDA). The spray structure was investigated for several alkanes with high and low volatility ( n-hexane, n-heptane, iso-octane, n-decane) and a three-component mixture of the n-alkanes with similar fuel properties like a multicomponent gasoline fuel. It is found that the rapid evaporation of high volatility fuels can lead to spray destabilization, whereas low volatility single-component fuels overestimate radial spray propagation and vortex formation. For iso-octane the droplet size distribution is shifted to smaller droplets and the spray appeared to be less dense compared to n-heptane despite almost identical boiling behavior. However, the much higher viscosity of iso-octane determines the internal nozzle flow which results in a reduced injected fuel mass and changed atomization. A well defined three-component fuel models the global spray characteristics as well as the droplet size, droplet momentum distribution and evaporation behavior of the used multicomponent gasoline fuel very precisely. Small amounts of low volatility fractions delay the droplet evaporation and support the overall spray stability also for multicomponent mixtures. This leads to an increased spray width as well as larger droplet sizes and momenta. The evaporation characteristic of multicomponent fuels at increased ambient pressure is complex. At the studied injection conditions it is situated between the two limiting cases of distillation-like behavior and coevaporation of the components. Moreover, the results in comparison with theoretical estimations indicate a demixing of light and heavy boiling fractions in the three-component and multicomponent fuel under conditions which are typical for DISI strategies with late injection.

Numerical study of solid fuel evaporation and auto-ignition in a dump combustor

Evaporation of polymeric solid fuels in backward facing step geometry subject to an inlet oxidizer flow at elevated temperatures is considered and convective heating of the fuel surface by the hot oxidizing inlet flow and subsequent mixing of the evaporated fuel with the oxidizer flow and its combustion is numerically studied. The objective of this work is to gain insight into the auto-ignition of the fuel and its controlling parameters in this configuration. The system of governing equations is solved with a finite volume approach using a structured grid in which the AUSM + scheme is used to calculate the gas phase convective fluxes. The flowfield is turbulent and the Spalart–Allmaras turbulence model is used in these simulations. Special attention is paid to the coupling of gas and solid phase to study the ignition process. Distinct intervals in ignition delay time are studied and evaporation time, mixing time, and reaction time are individually estimated. We have demonstrated that for inlet oxidizer streams with high initial oxygen concentration levels and high enough inlet temperatures a diffusion-controlled ignition mechanism controls the ignition time delay independent of the inlet velocity. This ignition time delay is directly related to the solid fuel evaporation time delay.

Effects of Fuel Vapor in Ambience on Spontaneous Ignition of Isolated Fuel Droplet

Experiments have been carried out on the effects of pre-vaporized fuel in the ambience on spontaneous ignition behavior of isolated fuel droplets. An isolated droplet of n-heptane or n-dodecane, which is sustained by a quartz fiber, is inserted into a high-temperature gas field including fuel in the electric furnace. Methane and n-heptane are selected as fuels of the ambience. The ambient pressure and the temperature are set to be 0.3 MPa and 700 K, respectively, in order to prevent the consumption of methane and oxygen in the ambience. The condition of the ambience including fuel is elucidated using a numerical analysis of chemical reactions. The results indicate that the ignition delay time increases due to methane included in the ambience. In the case of the ambience where n-heptane vapor is included, both n-heptane and oxygen are consumed by chemical reactions prior to the droplet insertion. The ignition delay time of n-heptane droplet in the reacted n-heptane and air mixture is larger than that in air and chemical reactions at the reduced oxygen concentration seems to be slow. The ignition delay time is shorter in the reacted n-heptane and air mixture than in an air with the same amount of oxygen as the reacted mixture.