Characterization of Tumble Motion in SI Engines: A New Parameter

2002 ◽  
Author(s):  
Pramod S. Mehta ◽  
M. Achuth
Keyword(s):  
Life Span ◽  
Combustion Chamber ◽  
Flow Analysis ◽  
Combustion Process ◽  
Operating Conditions ◽  
Mean Flow ◽  
Detailed Mechanism ◽  
Engine Combustion ◽  
Si Engines

A well-timed turbulence due to tumble in SI engines is found to be of substantial benefit to the engine combustion process. A mean flow analysis of tumble motion in conjunction with k-ε turbulence model has been developed to provide a detailed mechanism for turbulence enhancement due to tumble. Considering that the tumble phenomenon is highly geometry dependant, an attempt is made to relate tumble-generated turbulence to the parameters relating to intake conditions and combustion chamber geometry. Finally, a new parameter ‘vortex life span’ has been proposed to characterize tumble and its turbulence, which globally encompasses intake and combustion chamber related features. The sensitivity of this parameter is demonstrated at various operating conditions. It is found that the ‘vortex life span’ has an inverse relationship with commonly measured BDC tumble ratio and is more sensitive to the chamber geometry effects.

Multidimensional Modeling of Temperature Distribution in Engine Combustion Chamber

2011 ◽  
Author(s):  
Yuanhong Li ◽  
Song-Charng Kong
Keyword(s):  
Heat Conduction ◽  
Combustion Chamber ◽  
Thermal Stresses ◽  
Combustion Process ◽  
Numerical Procedure ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
Uniform Temperature ◽  
Temperature Distributions ◽  
Engine Combustion

Heat conduction calculations are coupled with in-cylinder combustion modeling for engine simulation in this study. Heat transfer on the fluid-solid interface will affect the in-cylinder combustion process, emissions formation, and thermal loading on the combustion chamber surface. Full knowledge of heat fluxes on the interface is important in helping improve engine efficiency, reduce exhaust emissions, and reduce combustion chamber thermal stresses. To account for the unsteady, non-uniform temperature distributions on the combustion chamber surface, a fully coupled numerical procedure was developed and applied to calculate in-cylinder flows and heat conduction in solids simultaneously. The current approach was first validated against analytical heat conduction solutions. The model was then applied to simulate diesel engine combustion under different operating conditions. Unsteady, non-uniform temperature distributions on the piston surface were successfully predicted. Global engine parameters including in-cylinder pressure, heat release rate, and emissions were also comparable to the experimental data.

scholarly journals On the Turbulence-Chemistry Interaction of an HCCI Combustion Engine

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5876
Author(s):  
Marco D’Amato ◽  
Annarita Viggiano ◽  
Vinicio Magi
Keyword(s):  
Combustion Chamber ◽  
Numerical Study ◽  
Combustion Process ◽  
Operating Conditions ◽  
Chemical Mechanism ◽  
Model Parameters ◽  
Time Duration ◽  
Hcci Engine ◽  
Hcci Combustion ◽  
Engine Combustion

A numerical study was carried out to evaluate the influence of engine combustion chamber geometry and operating conditions on the performance and emissions of a homogeneous charge compression ignition (HCCI) engine. Combustion in an HCCI engine is a very complex phenomenon that is influenced by several factors that need to be controlled, such as gas temperature, heat transfer, turbulence and auto-ignition of the gas mixture. An eddy dissipation concept (EDC) combustion model was used to take into account the interaction between turbulence and chemistry. The model assumed that reactions occur in small turbulent structures called fine-scales, whose characteristic lengths and times depend mainly on the turbulence level. The model parameters were slightly modified with respect to the standard model proposed by Magnussen, to correctly simulate the characteristics of the HCCI combustion process. A reduced iso-octane chemical mechanism with 186 species and 914 chemical reactions was employed together with a sub-mechanism for NOx. The model was validated by comparing the results with available experimental data in terms of pressure and instantaneous heat release rate. Two engine chamber geometries with and without a cavity in the piston were considered, respectively. The two engines provided significant differences in terms of fluid-dynamic patterns and turbulence intensity levels in the combustion chamber. The results show that combustion started earlier and proceeded faster for the flat piston, leading to an increase in both the peak pressure and gross indicated mean effective pressure, as well as a reduction of CO and UHC emissions. An additional analysis was performed by considering a case without swirl for the flat-piston case. Such an analysis shows that the swirl motion reduces the time duration of combustion and slightly increases the gross indicated work per cycle.

scholarly journals Optimizing the Shape of a Compression-Ignition Engine Combustion Chamber by Using Simulation Tests

2019 ◽  
Vol 26 (3) ◽  
pp. 138-146
Author(s):  
Ireneusz Pielecha ◽  
Jerzy Merkisz
Keyword(s):  
Combustion Chamber ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Combustion Process ◽  
Operating Conditions ◽  
Multidimensional Data ◽  
Compression Ignition ◽  
System Quality ◽  
Compression Ignition Engine ◽  
Engine Combustion

Abstract Modern solutions used in compression-ignition internal combustion engines are quite similar to each other. The use of high-pressure, direct fuel injection results in high combustion rates with controlled exhaust emissions. One of the combustion system quality criteria is to obtain adequately high thermodynamic indicators of the combustion process, which are obtained through, among others, the right combustion chamber geometry. Its shape influences the fuel atomization process, turbulence of fuel dose, evaporation and the combustion process. Optimizing the combustion chamber shape is one of the decisive factors proving the correct execution of the combustion process. This article presents the methodology of choosing the combustion chamber shape (changes of three selected combustion chamber dimensions) by using the optimization methods. Generating multidimensional data while maintaining the correlation structure was performed by using the Latin hypercube method. Chamber optimization was carried out by using the Nelder-Mead method. The combustion chamber shape was optimized for three engine load values (determined by the average indicated pressure) at selected engine operating conditions. The presented method of engine combustion chamber optimization can be used in low and high speed diesel propulsion engines (especially in maritime transport applications).

Analysis and Research of the Combustion Process of YN4100QB Diesel Engine

2013 ◽  
Vol 744 ◽  
pp. 35-39
Author(s):  
Lei Ming Shi ◽  
Guang Hui Jia ◽  
Zhi Fei Zhang ◽  
Zhong Ming Xu
Keyword(s):  
Diesel Engine ◽  
Internal Combustion Engine ◽  
Combustion Chamber ◽  
Optimization Design ◽  
Combustion Engine ◽  
Geometric Model ◽  
Combustion Process ◽  
Internal Combustion ◽  
Engine Combustion ◽  
Exhaust Noise

In order to obtain the foundation to the research on the Diesel Engine YN4100QB combustion process, exhaust, the optimal design of combustion chamber and the useful information for the design of exhaust muffler, the geometric model and mesh model of a type internal combustion engine are constructed by using FIRE software to analyze the working process of internal combustion engine. Exhaust noise is the main component of automobile noise in the study of controlling vehicle noise. It is primary to design a type of muffler which is good for agricultural automobile engine matching and noise reduction effect. The present car mufflers are all development means. So it is bound to cause the long cycle of product development and waste of resources. Even sometimes not only can it not reach the purpose of reducing the noise but also it leads to reduce the engine dynamic. The strength of the exhaust noise is closely related to engine combustion temperature and pressure. The calculation and initial parameters are applied to the software based on the combustion model and theory. According to the specific operation process of internal combustion engine. Five kinds of common operation condition was compiled. It is obtained for the detailed distribution parameters of combusted gas temperature pressure . It is also got for flow velocity of the fields in cylinder and given for the relation of the parameters and crankshaft angle for the further research. At the same time NOx emissions situation are got. The numerical results show that not only does it provide the 3D distribution data in different crank shaft angle inside the cylinder in the simulation of combustion process, but also it provides a basis for the engine combustion ,emission research, the optimization design of the combustion chamber and the useful information for the designs of muffler.

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.

scholarly journals Flow field and species concentration measurements in the primary zone of an aero-engine combustion chamber

2018 ◽  
Vol 10 (1) ◽  
pp. 168781401774805
Author(s):  
Yinli Xiao ◽  
Zupeng Wang ◽  
Zhengxin Lai ◽  
Kefei Chen ◽  
Wenyan Song
Keyword(s):  
Flow Field ◽  
Combustion Chamber ◽  
Operating Conditions ◽  
Chamber Pressure ◽  
Species Concentration ◽  
Primary Zone ◽  
Major Species ◽  
Engine Combustion ◽  
Aero Engine ◽  
Concentration Measurements

The principal features of primary zone determine the performance parameters of the whole combustion chamber, such as the pollutant emissions and combustion efficiency. In this work, flow field and major species concentration measurements are conducted in the primary zone of an aero-engine combustion chamber. The operating conditions such as air inlet temperature, chamber pressure, and air-to-fuel ratio are chosen to replicate the realistic operating conditions. The velocity field and streamlines are obtained by particle imaging velocimetry technology. The concentrations of major species are acquired by a spontaneous Raman scattering system. This article validates the feasibility of two laser diagnostic measurement techniques and presents the initial results under realistic aero-engine conditions.

scholarly journals Effect of Sisal Nanoparticles on Single Cylinder Spark Ignition Engine Combustion

2020 ◽  
Vol 8 (6) ◽  
pp. 1027-1032
Keyword(s):  
Flame Propagation ◽  
Combustion Process ◽  
Fuel Mixture ◽  
Spark Ignition ◽  
Combustion Efficiency ◽  
Spark Ignition Engine ◽  
Single Cylinder ◽  
Engine Combustion ◽  
Si Engines ◽  
Propagation Velocities

Turbulence is an important parameter to be considered for effective combustion inside a cylinder. Heat transfer inside the cylinder affects the combustion process. Insufficient turbulence leads to incomplete combustion, resulting in pollution. Effective flame propagation leads to higher combustion rates in SI engines which in turn requires enough turbulence. Effective combustion efficiency can be achieved through higher flame propagation velocities. In the present work an attempt has been made to enhance the turbulence inside the cylinder of a single cylinder spark ignition engine by injecting solid nanoparticles into the air fuel mixture.

Analysis of the Self-Excited Dynamics of a Heavy-Duty Annular Combustion Chamber by Large-Eddy Simulation

2019 ◽  
Author(s):  
Vittorio Michelassi ◽  
Roberto Meloni ◽  
Giovanni Riccio ◽  
Gianni Ceccherini
Keyword(s):  
Combustion Chamber ◽  
Operating Conditions ◽  
Test Facility ◽  
Heavy Duty ◽  
Mean Flow ◽  
Combustion Dynamics ◽  
Eddy Simulation ◽  
Stable Operating ◽  
Large Eddy ◽  
Accuracy Data

Abstract This paper discusses the use of LES to predict the performance of an annular combustion chamber in stable operating conditions and in presence of self-exited dynamics. The availability of high-accuracy data taken in a full-scale combustion test facility allowed an extensive validation of the prediction capability. The analysis focuses on a small size heavy duty annular gas turbine whose size allows to test and compute the entire 360° combustion chamber. The comparison with measurements confirms that, if the correct operating conditions are implemented, LES is capable to discern between stable and unstable operating conditions, as well as predict several other engineering relevant parameters, although the model is sometime affected by a limited shift in frequency. The post processing of LES results in presence of combustion dynamics is not a trivial task. Here the results of the simulations have been post-processed by means of a triple decomposition method to determine a mean flow, a deterministic unsteady flow at the main instability frequency and a turbulent stochastic flow. Such decomposition indicated the instability triggering mechanism together with the cross-talk mechanism between different components. This approach is currently used for design phase, while further validation is on-going to include different geometries and operating conditions with the goal of reducing both risks and number of tests.

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