Prediction method for ignition delay time of liquid spray combustion in constant volume chamber

It is well known that nozzle internal geometries affect the characteristics of diesel spray and combustion. However, despite a number of studies, the effects are difficult to generalize. It is also not clear which spray features are more important for combustion than others. To investigate these subjects, a comprehensive dataset on diesel spray combustion was obtained with 20 variations of multi-hole injector nozzle. The 20 variations had different combinations of orifice diameter, orifice length, sac length and orifice hub-to-tip ratio, which cover the large range of existing production injectors. Vapor penetration, vapor width, ignition delay time, ignition distance and lift-off length were quantified using schlieren and excited-state hydroxyl radical (OH*) chemiluminescence imaging for an isolated plume emerging from these different nozzles. The experiments were conducted with Japanese diesel fuel in a constant-volume diesel spray combustion facility at Sandia National Laboratories. The results were analyzed with response surface and Lasso regression analysis to identify significant design factors for spray combustion. Orifice diameter has large effects on spray combustion. Orifice length, sac length, orifice hub-to-tip ratio and their interactions have effects on spray combustion, but each effect is smaller than the effect of orifice diameter. Vapor penetration is a significant design factor for ignition delay time, ignition distance and lift-off length, while vapor width is not. Lift-off length is well-explained by ignition distance and ignition delay time. Ignition distance should be taken into consideration as a significant design factor for lift-off length as well as ignition delay time.

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A study on the influence of ignition energy on ignition delay time and laminar burning velocity of lean methane/air mixture in a constant volume combustion chamber

Journal of Science and Technology Issue on Information and Communications Technology ◽

10.31130/ud-jst2021-009e ◽

2021 ◽

pp. 1-4

Author(s):

Nguyen Minh Tien Nguyen

Keyword(s):

Combustion Chamber ◽

Ignition Delay ◽

Delay Time ◽

Ignition Delay Time ◽

Burning Velocity ◽

Constant Volume ◽

Laminar Burning Velocity ◽

Ignition Energy ◽

Constant Volume Combustion ◽

Constant Volume Combustion Chamber

This study presents the effect of ignition energy (Eig) on ignition delay time (tdelay) and uncertainty of laminar burning velocity (Su0) measurement of lean methane/air mixture in a constant volume combustion chamber. The mixture at an equivalence ratio of 0.6 is ignited using a pair of electrodes at the 2-mm spark gap. Eig is measured by integrating the product of voltage V(t) and current I(t) signals during a discharge period. The in-chamber pressure profiles are analyzed using the pressure-rise method to obtain tdelay and Su0. Su0 approximates 8.0 cm/s. Furthermore, the increasing Eig could shorten tdelay, leading to a faster combustion process. However, when Eig is greater than a critical value, called minimum reliable ignition energy (MRIE), the additional elevating Eig has the marginal effect on tdelay and Su0. The existence of MRIE supports to optimize the ignition systems and partly explains why extreme-high Eig>> MRIE has less contribution to engine performance.

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On the Influence of Fuel Stratification and its Control on the Efficiency of the Shockless Explosion Combustion Cycle

Volume 3: Coal, Biomass, and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration; Organic Rankine Cycle Power Systems ◽

10.1115/gt2018-76435 ◽

2018 ◽

Cited By ~ 2

Author(s):

T. S. Rähse ◽

P. Stathopoulos ◽

J.-S. Schäpel ◽

F. Arnold ◽

R. King

Keyword(s):

Thermal Efficiency ◽

Ignition Delay ◽

Delay Time ◽

Pressure Wave ◽

Ignition Delay Time ◽

Fuel Injection ◽

Constant Volume ◽

Fuel Stratification ◽

Auto Ignition ◽

Constant Volume Combustion

Constant volume combustion cycles for gas turbines are considered a very promising alternative to the conventional Joule cycle and its variations. The reason is the considerably higher thermal efficiency of theses cycles, at least for their ideal versions. Shockless explosion combustion is a method to approximate constant volume combustion. It is a cyclic process that consists of four stages, namely wave propagation, fuel injection, homogeneous auto-ignition and exhaust. A pressure wave in the combustion chamber is used to realize the filling and exhaust phases. During the fuel injection stage, the equivalence ratio is controlled in such a way that the ignition delay time of the mixture matches its residence time in the chamber before self ignition. This means that the fuel injected first must have the longest ignition delay time and thus forms the leanest mixture with air. By the same token, fuel injected last must form the richest mixture with air (assuming that a rich mixture leads to a small ignition delay). The total injection time is equal to the time that the wave needs to reach the open combustor end and return as a pressure wave to the closed end. Up to date, fuel stratification has been neglected in thermodynamic simulations of the SEC cycle. The current work presents its effect on the thermal efficiency of the cycle and on the exhaust conditions (pressure, temperature and Mach number) of shockless explosion combustion chambers. This is done by integrating a fuel injection control algorithm in an existing CFD code. The capability of this algorithm to homogenize the auto-ignition process by improving the injection process has been demonstrated in past experimental studies of the SEC. The numerical code used for the simulation of the combustion process is based on the time-resolved 1D-Euler equations with source terms obtained from a detailed chemistry model.

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Ignition Delay Time for Silane/Hydrogen/Air Mixtures at Low Temperatures

Физика горения и взрыва ◽

10.15372/fgv20180404 ◽

2018 ◽

Keyword(s):

Ignition Delay ◽

Delay Time ◽

Low Temperatures ◽

Ignition Delay Time

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Ignition delay time measurements for distillate and synthetic jet fuels

AIAA Scitech 2019 Forum ◽

10.2514/6.2019-2248 ◽

2019 ◽

Cited By ~ 1

Author(s):

Yu Wang ◽

Yi Cao ◽

David F. Davidson ◽

Ronald K. Hanson

Keyword(s):

Ignition Delay ◽

Delay Time ◽

Ignition Delay Time ◽

Synthetic Jet ◽

Jet Fuels

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THERMAL BEHAVIOR AND IGNITION OF HIGH-ENERGY MATERIALS CONTAINING B, ALB2, AND TIB2

NONEQUILIBRIUM PROCESSES. Vol. 2. Fundamentals of combustion ◽

10.30826/nepcap2018-2-14 ◽

2020 ◽

Author(s):

A. G. Korotkikh ◽

◽

V. A. Arkhipov ◽

I. V. Sorokin ◽

E. A. Selikhova ◽

...

Keyword(s):

Heat Flux ◽

Thermal Behavior ◽

Flux Density ◽

Ignition Delay ◽

Delay Time ◽

Heat Flux Density ◽

Ignition Delay Time ◽

High Energy ◽

Energy Materials ◽

High Energy Materials

The paper presents the results of ignition and thermal behavior for samples of high-energy materials (HEM) based on ammonium perchlorate (AP) and ammonium nitrate (AN), active binder and powders of Al, B, AlB2, and TiB2. A CO2 laser with a heat flux density range of 90-200 W/cm2 was used for studies of ignition. The activation energy and characteristics of ignition for the HEM samples were determined. Also, the ignition delay time and the surface temperature of the reaction layer during the heating and ignition for the HEM samples were determined. It was found that the complete replacement of micron-sized aluminum powder by amorphous boron in a HEM sample leads to a considerable decrease in the ignition delay time by a factor of 2.2-2.8 at the same heat flux density due to high chemical activity and the difference in the oxidation mechanisms of boron particles. The use of aluminum diboride in a HEM sample allows one to reduce the ignition delay time of a HEM sample by a factor of 1.7-2.2. The quasi-stationary ignition temperature is the same for the AlB2-based and AlB12-based HEM samples.

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