Modeling the Initial Growth of the Plasma and Flame Kernel in S.I. Engines

2001 ◽  
Author(s):  
Hilde Willems ◽  
Roger Sierens
Keyword(s):  
Burning Velocity ◽  
Life Time ◽  
Electrical Energy ◽  
Combustible Mixture ◽  
Heat Losses ◽  
Cylinder Wall ◽  
Initial Growth ◽  
Flame Kernel ◽  
Average Flow Velocity ◽  
Combustion Phase

Abstract The initial size and growth of the plasma and flame kernel just after spark discharge in S.I. engines determines if the flame becomes self-sustainable or extinguishes. On the other hand the development of the kernel during the initial phases has non-negligible influences on the further combustion. For example cyclic variations often find their origin in the beginning of combustion and determine the working limits of the engine and the driving behavior of the vehicle. These factors demonstrate the crucial importance of the knowledge of the initial growth of the plasma and flame kernel in S.I. engines. A complete model is developed for the growth of the initial plasma and flame kernel in S.I. engines, which takes into account the fundamental properties of the ignition system (electrical energy and power, geometry of the spark plug, heat losses to the electrodes and the cylinder wall), the combustible mixture (pressure, temperature, equivalence ratio, fraction of residual gasses, kind of fuel) and the flow (average flow velocity, turbulence intensity, stretch, characteristic time and length scales). The proposed model distinguishes three phases: the prebreakdown, the plasma and the initial combustion phase. The model of the first two phases is proposed in a previous article of the same authors (Willems and Sierens, 1999), the latter is exposed in this article. A thermodynamic model based on flamelet models and which takes stretch into account, is used to describe the initial combustion phase. The difference between heat losses to the electrodes and the cylinder wall is considered. The burning velocity varies from the order of the laminar velocity to the fully developed burning velocity. The evolution is determined as well by the life time as by the size of the kernel. The stretch (caused by turbulence and by the growth of the kernel), the non-adiabatic character of the flame and instabilities have influence on the laminar burning velocity. Validation of this model is done using measurements of the expansion in a propane-air mixture executed by Pischinger at M.I.T. The correspondence seems to be very well.

Modeling the Initial Growth of the Plasma and Flame Kernel in SI Engines

2003 ◽  
Vol 125 (2) ◽  
pp. 479-484 ◽  
Author(s):  
H. Willems ◽  
R. Sierens
Keyword(s):  
Burning Velocity ◽  
Life Time ◽  
Electrical Energy ◽  
Combustible Mixture ◽  
Heat Losses ◽  
Cylinder Wall ◽  
Initial Growth ◽  
Flame Kernel ◽  
Average Flow Velocity ◽  
Combustion Phase

The initial size and growth of the plasma and flame kernel just after spark discharge in S.I. engines determines if the flame becomes self-sustainable or extinguishes. On the other hand, the development of the kernel during the initial phases has non-negligible influences on the further combustion. For example, cyclic variations often find their origin in the beginning of combustion and determine the working limits of the engine and the driving behavior of the vehicle. These factors demonstrate the crucial importance of the knowledge of the initial growth of the plasma and flame kernel in S.I. engines. A complete model is developed for the growth of the initial plasma and flame kernel in S.I. engines, which takes into account the fundamental properties of the ignition system (electrical energy and power, geometry of the spark plug, heat losses to the electrodes and the cylinder wall), the combustible mixture (pressure, temperature, equivalence ratio, fraction of residual gasses, kind of fuel), and the flow (average flow velocity, turbulence intensity, stretch, characteristic time and length scales). The proposed model distinguishes three phases: the pre-breakdown, the plasma, and the initial combustion phase. The model of the first two phases is proposed in a previous article of the same authors [1], the latter is exposed in this article. A thermodynamic model based on flamelet models and which takes stretch into account, is used to describe the initial combustion phase. The difference between heat losses to the electrodes and the cylinder wall is considered. The burning velocity varies from the order of the laminar velocity to the fully developed burning velocity. The evolution is determined as well by the life time as by the size of the kernel. The stretch (caused by turbulence and by the growth of the kernel), the nonadiabatic character of the flame, and instabilities have influence on the laminar burning velocity. Validation of this model is done using measurements of the expansion in a propane-air mixture executed by Pischinger [2] at M.I.T. The agreement seems very good.

scholarly journals Experimental and Simulation of Diesel Engine Fueled with Biodiesel with Variations in Heat Loss Model

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1622
Author(s):  
Daniel Romeo Kamta Legue ◽  
Zacharie Merlin Ayissi ◽  
Mahamat Hassane Babikir ◽  
Marcel Obounou ◽  
Henri Paul Ekobena Fouda
Keyword(s):  
Heat Release ◽  
Heat Loss ◽  
Heat Release Rate ◽  
Release Rate ◽  
Diffusion Combustion ◽  
Cylinder Wall ◽  
Compression Ignition Engine ◽  
Experimental Conditions ◽  
Load Range ◽  
Combustion Phase

This study presents an experimental investigation and thermodynamic 0D modeling of the combustion of a compression-ignition engine, fueled by an alternative fuel based on neem biodiesel (B100) as well as conventional diesel (D100). The study highlights the effects of the engine load at 50%, 75% and 100% and the influence of the heat loss models proposed by Woschni, Eichelberg and Hohenberg on the variation in the cylinder pressure. The study shows that the heat loss through the cylinder wall is more pronounced during diffusion combustion regardless of the nature of the fuels tested and the load range required. The cylinder pressures when using B100 estimated at 89 bars are relatively higher than when using D100, about 3.3% greater under the same experimental conditions. It is also observed that the problem of the high pressure associated with the use of biodiesels in engines can be solved by optimizing the ignition delay. The net heat release rate remains roughly the same when using D100 and B100 at 100% load. At low loads, the D100 heat release rate is higher than B100. The investigation shows how wall heat losses are more pronounced in the diffusion combustion phase, relative to the premix phase, by presenting variations in the curves.

Development and Validation of an Ignition Model for SI Engines

2006 ◽  
Author(s):  
Stefania Falfari ◽  
Gian Marco Bianchi
Keyword(s):  
Cfd Simulation ◽  
Combustion Process ◽  
Three Dimensional ◽  
Electrical Energy ◽  
Combustion Model ◽  
Test Case ◽  
Ignition Process ◽  
Mean Flow ◽  
Flame Kernel ◽  
Si Engines

In SI engines the ignition process strongly affects the combustion process. Its accurate modelling becomes a key issue for a design-oriented CFD simulation of the combustion process. Different approaches to simulate ignition have been proposed. The common base is decoupling the physics related to the very first ignition phase when a plasma is formed from that of the development of the flame kernel. The critical point of ignition models is related to the capability of representing the effect of ignition system characteristics, the criterion used for flame deposit and the initialisation of the combustion model. This paper aims to present and validates extensively an ignition model suited for CFD calculation of premixed combustion. The ignition model implemented in a customized version of the Kiva 3 code is coupled with ECFM Flamelet combustion model. The ignition model simulates the plasma/kernel expansion based on a lump evaluation of main ignition processes (i.e., breakdown, arc-phase and glow phase). A double switch criterion based on physical and numerical consideration is used to switch to the main combustion model. The Herweg and Maly experimental test case has been used to check the model capability. In particular, two different ignition systems having different amount of electrical energy released during spark discharge are considered. Comparisons with experimental results allowed testing the model with respect to its capability to reproduce the effects of mixture equivalence ratio, mean flow, turbulence and spark energy on flame kernel development as never done before in three-dimensional RANS CFD combustion modelling of premixed flames.

On the issue of occurrence of fire-hazardous situations with unbalanced power consumption

2021 ◽  
Vol 14 (1) ◽  
pp. 69-76
Author(s):  
I. V. Naumov ◽  
D. A. Karamov
Keyword(s):  
Power Consumption ◽  
Electrical Energy ◽  
Heat Losses ◽  
Zero Sequence ◽  
The Russian Federation ◽  
Short Circuits ◽  
Phase Conductors ◽  
Current Unbalance ◽  
Supply Systems ◽  
Additional Losses

The influence of phase current unbalance on the probability of occurrence of fire-hazardous situations in industrial premises that receive power in various power supply systems is considered. The theoretical prerequisites for the occurrence of fire-hazardous situations are described. It is shown that zero-sequence flows flowing through a neutral conductor in an unbalanced mode significantly heat it, which can lead to short circuits and conditions for the occurrence of fires. The results of studies of unbalanced conditions in Russia and abroad are presented. It is shown that the zero-sequence flows resulting from current unbalance lead to an increase in additional losses of active power and electrical energy. It is proved that additional heat losses caused by unbalanced power consumption can destroy the insulation of neutral and phase conductors, which is the main cause of short circuits and, as a result, fires. Based on the use of the Matlab graphical editor, dynamic characteristics of variations in phase and interphase currents and voltages, as well as the power loss coefficient, which characterizes the increase in heat losses, are constructed. The analysis of fires and their consequences for various objects in the Russian Federation is made. A computational unit has been developed in Matlab, which is used for calculating and plotting the dynamics of fires and their consequences over the investigated period of time. It is shown that the occurrence of fires and their consequences due to violations of the rules of operation of electrical installations occurs in any premises and sometimes reaches more than 20% of all possible causes of fires. Methods and technical means of minimizing zero-sequence currents as a means of preventing the occurrence of fire-hazardous situations are considered. The principle of operation of an automatically controlled shunt-symmetric device with a minimum resistance to zero-sequence currents is described.

scholarly journals Advances in Power and Energy Systems

TecnoLógicas ◽  
2018 ◽  
Vol 21 (42) ◽  
pp. 9-11
Author(s):  
Carlos A. Ramos-Paja ◽  
Daniel González-Montoya ◽  
Adriana Trejos-Grisales ◽  
Sergio I. Serna-Garcés
Keyword(s):  
Renewable Energy Sources ◽  
Life Time ◽  
Electrical Energy ◽  
Energy Storage Devices ◽  
Storage Devices ◽  
Electrical Systems ◽  
Research Fields ◽  
Power And Energy Systems ◽  
Power And Energy

Processing electrical energy is one of the most important research fields in our society. So far, tremendous efforts have been made to improve the efficiency of each step in electrical systems: generation systems have been enhanced by introducing renewable energy sources and new control systems for conventional generators, losses have been reduced, the power quality of distribution and transmission systems has been increased, the life-time and state-of-health of energy storage devices have been extended, and sections of the power grid have been isolated for intelligent energy management.

STABILITY OF ULTRALEAN HYDROGEN FLAMES IN TERRESTRIAL CONDITIONS

2020 ◽  
Author(s):  
I. Yakovenko ◽  
◽  
K. Melnikova ◽  
A. Kiverin ◽  
◽  
...  
Keyword(s):  
Large Scale ◽  
Burning Velocity ◽  
Flame Structure ◽  
Combustion Products ◽  
Flammability Limits ◽  
Flame Kernel ◽  
Terrestrial Gravity ◽  
Convective Flows ◽  
Flame Dynamics ◽  
Scale Motion

The paper is devoted to the study of specific features of flame dynamics in ultralean hydrogen-air mixtures in terrestrial gravity conditions. By means of numerical methods, it is shown that gasdynamic flows, which develop due to the buoyancy force acting on the hot combustion products, play a crucial role on the overall ultralean flame dynamics from the earliest stage after ignition and up to the large-scale motion of the developed flame. Immediately after ignition, convective flows determine the stability of flame kernel. It is shown that, on the one hand, despite the “superadiabatic” temperature of the flame products that is considered as one of the main stability factors of the ultralean flames in microgravity conditions, the influence of convective flows on the ultralean flames in terrestrial gravity conditions can alter flammability limits from that measured in microgravity. On the other hand, the propagation dynamics of the stable flame kernels is also mainly determined by the buoyancy forces. Rising velocity of the flame kernel in the ultralean mixture occurs to be much greater than the burning velocity and correlates well with estimations obtained for the bubble rising in liquid. Apart from the upward rising, the developed flame is shown to be expanding laterally; so, the complex large-scale flame structure is observed which could be a possible threat for explosion and fire safety for many industrial environments.

A quasi-dimensional combustion model for spark ignition engines fueled with gasoline–methanol blends

2017 ◽  
Vol 232 (1) ◽  
pp. 57-74 ◽  
Author(s):  
Duc-Khanh Nguyen ◽  
Louis Sileghem ◽  
Sebastian Verhelst
Keyword(s):  
Ignition Delay ◽  
Burning Velocity ◽  
Measurement Data ◽  
Lewis Number ◽  
Combustion Model ◽  
Laminar Burning Velocity ◽  
Velocity Correlation ◽  
Flame Kernel ◽  
Initial Flame ◽  
Better Than

The current work provides a quasi-dimensional model for the combustion of methanol–gasoline blends. New correlations for the laminar burning velocity of gasoline and methanol are developed and used together with a mixing rule to calculate the laminar burning velocity of the blends. Several factors (such as the laminar burning velocity, initial flame kernel, residual gas fraction, turbulence, etc.) have been investigated and the sensitivity of these factors and the used sub-models on the predictive performance was assessed. The simulation results were compared with measurement data from two engines on different gasoline–methanol blends. The results show the importance of the laminar burning velocity correlation, the method of initializing combustion and the turbulent burning velocity model. The newly developed laminar burning velocity correlation of gasoline performed equally or better than the existing correlations and the newly developed correlation of methanol outperformed the other correlations. The initial flame kernel size had a strong influence on the ignition delay. Changing the initial flame kernel to reproduce the same ignition delay was very effective to improve the simulations. Several turbulent combustion models were tested with the newly developed laminar burning velocity correlations and optimized ignition delay. In conclusion, the model of Bradley reproduced the trend going from gasoline to methanol much better than others due to the inclusion of the Lewis number.

A Study on the Wall Thickness and Life Time or Life Cycle of High-Pressure Cylinders for Automotive Vehicles Under Pressure Circulation Conditions

2016 ◽  
Author(s):  
Yi-wen Yuan ◽  
Ming-hai Fu ◽  
Yu Li ◽  
Bo Yang
Keyword(s):  
High Pressure ◽  
Life Cycle ◽  
Wall Thickness ◽  
Life Time ◽  
Material Strength ◽  
Cylinder Wall ◽  
Market Demand ◽  
Pressure Cycle ◽  
Test Verification ◽  
Natural Gas Vehicle

NGV’s (Natural Gas Vehicle) are known for their energy-saving and environment-friendly advantages. The high-pressure cylinder for automotive vehicles (hereinafter cylinder) is the main energy supply unit of an NGV. Therefore, the Life time or Life Cycle of the cylinder is closely related to vehicle safety performance. Pressure cycle test is, as a test that simulates the cylinder filling process, the most realistic and effective method to evaluate cylinder Life time or Life Cycle. To simulate the actual situation of cylinder use, there are two types of Pressure cycle tests: Pressure cycle test under filling conditions and Pressure cycle test under overload conditions (LBB Mode). To meet the market demand for reduced vehicle mass, most cylinder manufacturers in China tend to reduce cylinder weight by improving cylinder material. strength and reducing cylinder wall thickness. Few manufacturers, however, pay attention to the relation between cylinder Life time or Life Cycle and cylinder thickness reduced by strength improvement. In this paper, Pressure cycle tests are conducted on cylinders with the same specification but various wall thickness values to calculate and analyze the Life time or Life Cycle values. This paper is trying to discover the inherent law between cylinder material. strength, wall thickness and Life time or Life Cycle, to put forward the viewpoint that analysis design or test verification can be adopted in cylinder wall thickness design, to build the wall thickness design model for a widely-used cylinder model, and to lay the theoretical basis for lightweight cylinder design under safe conditions.

Towards Integrated Spark and Combustion Modeling for Engines

2020 ◽  
Author(s):  
Anand Karpatne ◽  
Vivek Subramaniam ◽  
Sachin Joshi ◽  
Xiao Qin ◽  
Douglas Breden ◽  
...  
Keyword(s):  
Cross Flow ◽  
Electrical Energy ◽  
Combustion Model ◽  
Consistent Estimate ◽  
Combustion Kinetics ◽  
Flame Kernel ◽  
Combustion Modeling ◽  
Combustion Simulation ◽  
Coupling Strategy ◽  
Ignition And Combustion

Abstract Combustion and emission performance of internal combustion (IC) engines depend on the ability of the ignition system to provide an ignition kernel that can successfully transition into an early flame kernel. Several key physical phenomena such as flow physics, plasma dynamics, circuit transients, and electromagnetics influence the behavior of the spark. The combustion kinetics decide the eventual transition of the spark into a self-sustaining flame kernel. The goal of this paper is to present a feasibility study involving the integration of a high-fidelity magnetohydrodynamic description of the spark physics with a finite rate chemical kinetics-based combustion model. A future goal of this proposed framework will be to model and validate a coupled ignition and combustion simulation for spark ignited engines. Two separate solvers are used to model spark physics and combustion kinetics respectively, and a coupling strategy is developed to model different aspects of physics occurring at disparate time-scales. This approach provides a physically consistent estimate of the electrical energy distribution within the spark-gap under high cross-flow velocities. When provided with certain favorable in-cylinder conditions, the spark kernel triggers self-sustained combustion.

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