Two Stage Ignition of<i>n</i>-Heptane Isolated Droplets

Tanabe, Mitsuaki; Kono, Michikata; Sato, Junichi; Koenig, Jens; Eigenbrod, Christian; Dinkelacker, Friedrich; Zarm, H. J. Rath

doi:10.1080/00102209508960393

Cited by 65 publications

(36 citation statements)

References 8 publications

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“…For lower initial velocities, where a considerable increase of the relative velocity during the ignition process is present, the dependence of the ignition delay time on the gas flow velocity is not that strong and so the acceleration does not have a significant influence on the ignition delay time. The identification of a minor influence of gravity on the ignition delay times of droplets corresponds with the experimental results of Faeth and Olson [28], Tanabe et al [7], and Schnaubelt et al [12] for other fuels (n-heptane, n-hexadecane, benzene).…”

Section: Ignition Delay Timesmentioning

confidence: 93%

“…Qualitative numerical results for the ignition process of methanol droplets in air at high pressure and ignition delay times of droplets consisting of liquid oxygen in a hydrogen atmosphere have been presented by Aouina et al [22]. Several studies deal with the phenomena of the influence of gravitational acceleration on the ignition behavior of droplets [7,12,28,29].…”

Section: Introductionmentioning

confidence: 99%

“…Especially, a detailed understanding of the basic physical and chemical processes, such as vaporization, transport, and chemical kinetics, and their interaction is of interest. The ignition or combustion of single droplets in a quiescent atmosphere has been investigated in detail both experimentally and numerically for different fuels, e.g., methanol [1][2][3] and n-heptane [4][5][6][7][8][9][10][11][12][13][14][15], by a large number of research groups. However, in all technical applications, fuel droplets are exposed to a convective environment and to accelerating or decelerating forces.…”

Section: Introductionmentioning

confidence: 99%

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The ignition of methanol droplets in a laminar convective environment

Stauch

Maas

2008

Combustion and Flame

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Numerical simulations of the ignition of methanol droplets in a laminar convective environment are performed using detailed reaction mechanisms and detailed transport models. The flow velocities of the forced convection ranges from 0.01 up to 5 m/s, whereas the ambient gas temperature is varied between 1300 and 1500 K. The ignition delay time of a single droplet is found to decrease with increasing velocity of the convective gas flow. This decrease is attributed to the steepening of the spatial gradients of the profiles of physical variables, such as species mass fractions or temperature. This steepening is originated by a stronger gas flow and leads to a speed-up of the physical transport processes. For the studied flow conditions, an acceleration of the gas flow on the order of the gravitational acceleration does not show a significant influence on the ignition delay time. A downstream movement of the local ignition point with increasing flow velocity is observed. For higher flow velocities, an ignition in the wake of the droplet followed by an upstream flame propagation is found. After ignition, the formation of an envelope flame is detected. The structure of this envelope flame is studied.

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Section: Ignition Delay Timesmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The ignition of methanol droplets in a laminar convective environment

Stauch

Maas

2008

Combustion and Flame

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“…The predictions of the code developed in [23] were validated against experimental data published by Belardini et al [58], Nomura et al [59], and Tanabe et al [60]. In what follows a comparison between the experimental data reported in [59] and the predictions of the model will be discussed based on [23].…”

Section: Heating Evaporation and Ignition Of Fuel Droplets: Combinedmentioning

confidence: 99%

Modelling of heating, evaporation and ignition of fuel droplets: combined analytical, asymptotic and numerical analysis

Sazhin

2005

J. Phys.: Conf. Ser.

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Modelling of heating, evaporation and ignition of fuel droplets: combined analytical, asymptotic and numerical analysis Abstract.The paper discusses recent progress in the development of a combined analytical, asymptotic and numerical approach to modelling of heating and evaporation of fuel droplets and ignition of a fuel vapour/ air mixture. This includes a new approach to combined analytical and numerical modelling of droplet heating and evaporation by convection and radiation from the surrounding hot gas. The relatively small contribution of thermal radiation to droplet heating and evaporation allows us to take it into account using a simplified model, which does not consider the variation of radiation absorption inside droplets. The results of the analysis of the simplified problem of heating and evaporation of fuel droplets and ignition of fuel vapour/ air mixture based on the asymptotic method of integral manifolds are discussed. The semi-transparency of droplets was taken into account in this analysis, and a simplified model for droplet heat-up was used. The results of investigations of the effect of the temperature gradient inside fuel droplets on droplet evaporation, break-up and the ignition of fuel vapour/ air mixture based on a new zero-dimensional code are reviewed. The convection heating of droplets is described in this code based on a combined analytical and numerical approach. A new decomposition technique for a system of ordinary differential equations, based on the geometrical version of the integral manifold method is discussed. This is based on comparing the values of the right hand sides of these equations, leading to the separation of the equations into 'fast' and 'slow' variables. The hierarchy of the decomposition is allowed to vary with time. The application of this technique to analyse the explosion of a polydisperse spray of diesel fuel is presented. It is pointed out that this approach has clear advantages from the point of view of accuracy and CPU efficiency when compared with the conventional approach widely used in CFD codes. IntroductionThe problems of droplet heating, evaporation and ignition of fuel vapour/ air mixture have been widely discussed in the literature [1] - [10]. However, the models used in most practical engineering applications tend to be rather simple. This is due to the fact that droplet heating and evaporation have to be modelled alongside the effects of turbulence, combustion, droplet breakup and related phenomena in realistic 3D enclosures. Hence, finding a compromise between the complexity of the models and their computational efficiency is the essential precondition for successful modelling. In a series of our recent papers [11] -[25] an attempt was made to develop simplified models for droplet heating, evaporation and ignition of fuel vapour/air mixture;

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“…Many experiments, theoretical analyses and numerical simulations have been done on the ignition of single fuel droplets in ambience with infinite volume as the simplest model of spray ignition. [1][2][3][4][5][6][7][8][9] From studies on ignition of premixed gas, it is well known that certain fuels (often n-alkanes) burn to yield a cool flame under certain conditions with a flame temperature typically lower than 1000 K and with almost no light emission. 10) Countless elementary reactions for the oxidation of such fuels can be divided into two groups: high-temperature reactions, and low-temperature reactions.…”

Section: Introductionmentioning

confidence: 99%

Spontaneous Ignition of n-Alkane Droplets with Various Volatility

Moriue

Eigenbrod

Rath

et al. 2004

Trans. Japan Soc. Aero. S Sci.

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Ignition delays of a cool flame ( 1 ) and a hot flame ( t ) were measured experimentally for single n-decane, n-dodecane, n-tetradecane and n-hexadecane droplets, which have similar volatilities to common commercial hydrocarbon fuels, in hot air. Droplet diameter was 0.7 mm. Ambient pressure was 0.3 and 1.0 MPa. Ambient temperature was 550 K to 1000 K. Results show the similarity of the examined fuels in terms of reactivity of the low-and high-temperature reactions. Values of 1 and t were longer for fuels with lower volatility. Values of 2 (¼ t À 1 ) were similar for examined fuels. Both the ignition limits of cool and hot flames were similar between fuels, but were slightly lower for less-volatile fuels.

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Two Stage Ignition ofn-Heptane Isolated Droplets

Cited by 65 publications

References 8 publications

The ignition of methanol droplets in a laminar convective environment

The ignition of methanol droplets in a laminar convective environment

Modelling of heating, evaporation and ignition of fuel droplets: combined analytical, asymptotic and numerical analysis

Spontaneous Ignition of n-Alkane Droplets with Various Volatility

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