A methodology for analysis of diesel engine in-cylinder flow and combustion
26 May 2010-Progress in Computational Fluid Dynamics (Inderscience Publishers)-Vol. 10, Iss: 3, pp 157-167
TL;DR: In this article, a methodology is developed for the analysis of diesel engine in-cylinder processes and combustion and an integrated KIVA-3V code is developed by incorporating two well-validated models into the standard code: the Shell hydrocarbon auto-ignition model and the Characteristic-time model for simulation of subsequent diesel combustion.
Abstract: A methodology is developed for the analysis of diesel engine in-cylinder processes and combustion. Beginning from CAD data of the engine geometry, the methodology involves use of a commercial code AVL FIRE for simulation of suction stroke, and an open-source code KIVA-3V for simulation of the closed-valve part of the diesel cycle. For this, an algorithm is first developed to map a generalised three-dimensional Computational Fluid Dynamics (CFD) solution from an unstructured mesh in AVL FIRE to a structured mesh in KIVA-3V to provide initial conditions for the closed-valve simulations. For simulation of diesel combustion process, an integrated KIVA-3V code is developed by incorporating two well-validated models into the standard code: the Shell hydrocarbon auto-ignition model for simulation of diesel auto-ignition under conditions of high temperature and pressure, and the Characteristic-time model for simulation of subsequent diesel combustion. The integrated code is validated and calibrated against experimental pressure measurements in a naturally aspirated direct injection diesel engine. These tools are then used for exploring the potential of a constant-speed, turbocharged diesel engine towards emission reduction. The case study involves combustion simulations for exploring multiple injection strategy for the engine concerned.
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TL;DR: In this article, an experimental and numerically investigating in-cylinder flows of a small motorcycle engine under steady-state conditions was conducted in the engine head for a variety of fixed valve lifts at two pressure drops (300 and 600 mmH2O).
9 citations
Dissertation•
01 Oct 2016
TL;DR: In this article, a mathematical model has been developed and used to simulate the behavior of the fuel injection system, including the fuel delivery and injector needle valve motions, and the authors investigated the change dynamic behaviour of fuel injection on engine combustion process.
Abstract: In recent years, serious restrictions on diesel emission levels, combined with price instability and a significant increase in imports, has forced researchers to look for alternatives to this fossil fuel. Biodiesel is widely accepted as an alternative because it can be used in diesel engines without any substantial modifications and produced by sustainable resources. However, there are serious gaps in available knowledge regarding the effects of biodiesel blends on engine fuel injection systems and the engine combustion process. Therefore, this research focuses on the investigation into such effects through a vibration analysis of fuel injection systems in order to achieve nonintrusive quantitative diagnosis and hence condition monitoring of CI engines.
Having identified the specifics of technique gaps by a comprehensive literature study, this research firstly, investigates the dynamics of the fuel injection system with a CI engine running on biodiesel blends as fuels. This is achieved by numerical modelling analysis and experimental studies, which paves ways for using vibration response of fuel injection to diagnose the dynamic behaviour of different fuel properties. Then it investigates the of the change dynamic behaviour of fuel injection on engine combustion process. Finally, it explores the diagnostics of engine valve train clearance faults with an engine running with biodiesel and biodiesel blends based on engine fuel injection vibration responses.
A mathematical model has been developed and used to simulate the behaviour of the fuel injection system, including the fuel delivery and injector needle valve motions. It has concluded that the high pressure dynamic forces within the injection system will be affected by fuel properties such as fuel density, viscosity and bulk modules. The simulation results demonstrated; (i) that, the injector pressure is higher than that of the fuel injection pump, whose amplitudes are about 10% higher for biodiesels compared with petro-diesel; (ii) the levels of the pressure forces applied to the delivery valve and injector needle valve are also higher for biodiesel blends and (iii) nearly 1° (cam shaft) advance in the times of fuel injection rates and valve impacts with biodiesel and biodiesel blends. These predictions are confirmed by experimental results obtained by injection line pressures and pump vibrations and in-cylinder pressures.
Diesel engines are particularly prone to the engine combustion process primarily due to a fault in the fuel injection system and an abnormal clearance valve train conditions. The high-signal to noise ratio pump vibrations obtained from the pump body can be easily used for detecting and diagnosing faults from fuel injections. In the meantime, the research has also established that the pump vibration signals can be also used to recognise valve train diagnostics with medium effort of signal processing. It has found that the vibration levels become higher, due to the faults as a consequence of additional fuel supply to compromise the loss of overall power caused by poor combustion performance on the cylinder with an increased valve clearance. Moreover, B20 and B40 exhibit the similar changes with that of petro-diesel in the proposed high frequency envelop amplitudes (HFEA) whereas B100 shows less increased values. However, the pressure measurements are not very clear in representing these small changes in valve clearances for both the exhaust and inlet valves.
Compared with head vibration signals, which also can indicate the faults by a reduced level of vibration due to an effect combined reduced valve movement stroke with gas flow dampening, the pump vibration signals uniformly show the injection events and allow combustion uniformity between different cylinders to be diagnosed using a single transducer, whereas it may produce less accurate diagnosis by the head vibrations because of the close overlap of combustion and valve impact responses which needs complicated methods to be separated.
6 citations
Cites background from "A methodology for analysis of diese..."
...Such measurements should also to be able to detect anomalies such as misfire or poor combustion in the cylinder [111], [112]....
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TL;DR: In this article, the in-cylinder flow characteristics of a four-stroke, four-valve, pentroof small engine of a motorcycle at engine speeds from 2000 rpm to 4000 rpm were studied using computational fluid dynamics (CFD).
Abstract: The in-cylinder flow characteristics of a four-stroke, four-valve, pent-roof small engine of motorcycle at engine speeds from 2000 rpm to 4000 rpm were studied using computational fluid dynamics (CFD). The aim of this study was to investigate the in-cylinder flow characteristics of small engines, including tumble, swirl, turbulent kinetic energy (TKE), angular momentum, in-cylinder air mass, turbulent velocity, turbulent length scale, and air flow pattern (in both intake and compression strokes) under motoring conditions. The engine geometry was created using SolidWorks, then was exported and analyzed using CONVERGE, a commercial CFD method. Grid independence analysis was carried out for this small engine and the turbulence model was observed using the renormalized group (RNG) k-ɛ model. The pressure boundary conditions were used to define the fluid pressure at the intake and exhaust of the port. The results showed that the increase in the engine speed caused the swirl flow in the small engine to be irregularly shaped. The swirl flow had a tendency to be stable and almost constant in the beginning of the compression stroke and increased at the end of compression stroke. However, the increase of in engine speed had no significant effect on the increase in tumble ratio, especially during the intake stroke. There was an increase in tumble ratio due to the increase in engine speed at the end of compression stroke, but only a marginal increase. The increase in engine speed had no significant effect on the increase in angular momentum, TKE, or turbulent velocity from the early intake stroke until the middle of the intake stroke. However, the angular momentum increased due to the increase in engine speed from the middle of the intake stroke to the end of compression stroke, and the angular momentum achieved the biggest increase when the engine speed rose from 3000 to 4000 rpm by 10 % at the end of the intake stroke. The increase in engine speed caused an increase of TKE and turbulent velocity from the middle of intake stroke until the end of compression stroke. Moreover, the biggest increase of TKE and turbulent velocity occurred when the engine speed rose from 3000 to 4000 rpm at the middle of intake stroke around 50 % and 25 %, respectively. Turbulent length scales appeared to be insensitive to increasing engine speed, especially in the intake stroke until 490 °CA. From that point, the value of the turbulent length scale increased as engine speed increased. The biggest increase in the turbulent length scales occurred when the intake valve was almost closed (around 20 %) and the engine speed was within two specific ranges (2000 to 3000 rpm and 3000 to 4000 rpm). Regarding the effect of engine speed, there were no significant effects upon the accumulated air mass in the small engine. The increase in engine speed caused an increase of turbulence in the combustion chamber during the late stages of the compression stroke. The increase in turbulence enhanced the mixing of air and fuel and made the mixture more homogeneous. Moreover, the increase in turbulence directly increased the flame propagation speed. Further research is recommended using a new design with several types of intake ports as well as combinations of different intake ports and some type of piston face, so that changes in air flow characteristics in small engines can be analyzed. Finally, this study is expected to help decrease the number of experiments necessary to obtain optimized systems in small engines.
4 citations
TL;DR: In this paper, the early phase combustion of a biogas engine was studied to assess the effect of various ignition parameters such as spark plug location, spark energy, and number of spark plugs.
Abstract: This paper presents computational work on the biogas early phase combustion in spark ignition (SI) engines using detailed chemical kinetics. Specifically, the early phase combustion is studied to assess the effect of various ignition parameters such as spark plug location, spark energy, and number of spark plugs. An integrated version of the KIVA-3V and CHEMKIN codes was developed and used for the simulations utilizing detailed kinetics involving 325 reactions and 53 species The results show that location of the spark plug and local flow field play an important role. A central plug configuration, which is associated with higher local flow velocities in the vicinity of the spark plug, showed faster initial combustion. Although a dual plug
configuration shows the highest rate of fuel consumption, it is comparable to the rate exhibited by the central plug case. The radical species important in the initiation of combustion are identified, and their concentrations are monitored during the early phase of combustion. The concentration of these radicals is also observed to correlate very well with the above-mentioned trend.Thus, the role of these radicals in promoting faster combustion has been clearly established. It is also observed that the minimum ignition energy required to initiate a self-sustained flame depends on the flow field condition in the vicinity of the spark plug.Increasing the methane content in the biogas has shown improved combustion.
4 citations
References
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Book•
01 Jan 1988
TL;DR: In this article, the authors describe real engine flow and combustion processes, as well as engine operating characteristics and their operation, including engine design and operating parameters, engine characteristics, and operating characteristics.
Abstract: 1 Engine Types and Their Operations 2 Engine Design and Operating Parameters 3 Thermochemistry of Fuel-Air Mixtures 4 Properties of Working Fluids 5 Ideal Models of Engine Cycles 6 Gas Exchange Processes 7 SI Engine Fuel Metering and Manifold Phenomena 8 Charge Motion within the Cylinder 9 Combustion in Ignition Engines 10 Combustion in Compression Ignition Engines 11 Pollutant Formation and Control 12 Engine Heat Transfer 13 Engine Friction and Lubrication 14 Modeling Real Engine Flow and Combustion Processes 15 Engine Operating Characteristics Appendixes
14,372 citations
"A methodology for analysis of diese..." refers methods in this paper
...Both the measured and the predicted heat release rates have been computed from the respective p – θ curves by applying a zero-dimensional model (Heywood, 1988)....
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01 Jan 1977
TL;DR: In this paper, a model for the rate of combustion which takes into account the intermittent appearance of reacting species in turbulent flames is presented, which is applicable to premixed as well as diffusion flames.
Abstract: Principles of mathematical models as tools in engineering and science are discussed in relation to turbulent combustion modeling. A model is presented for the rate of combustion which takes into account the intermittent appearance of reacting species in turbulent flames. This model relates the rate of combustion to the rate of dissipation of eddies and expresses the rate of reaction by the mean concentration of a reacting specie, the turbulent kinetic energy and the rate of dissipation of this energy. The essential features of this model are that it does not call for predictions of fluctuations of reacting species and that it is applicable to premixed as well as diffusion flames. The combustion model is tested on both premixed and diffusion flames with good results. Special attention is given to soot formation and combustion in turbulent flames. Predictions are made for two C 2 H 2 turbulent diffusion flames by incorporating both the above combustion model and the model for the rate of soot formation developed by Tesner et al., as well as previous observations by Magnussen concerning the behavior of soot in turbulent flames. The predicted results are in close agreement with the experimental data. All predictions in the present paper have been made by modeling turbulence by the k -∈ model. Buoyancy is taken into consideration in the momentum equations. Effects of terms containing density fluctuations have not been included.
2,575 citations
Book•
01 Mar 2000
TL;DR: In this article, the second edition of the Second Edition of the first edition, the authors presented a simplified conversation equation for the solution of nonlinear flow equations for a C-H-O-N system.
Abstract: Preface Preface to the Second Edition Preface to the First Edition 1: Introduction 2: Combustion and Thermochemistry 3: Introduction to Mass Transfer 4: Chemical Kinetics 5: Some Important Chemical Mechanisms 6: Coupling Chemical and Thermal Analyses of Reacting Systems 7: Simplifed Conversation Equations for Reacting Flows 8: Laminar Premixed Flames 9: Laminar Diffusion Flames 10: Droplet Evaporation and Burning 11: Introduction to Turbulent Flows 12: Turbulent Premixed Flames 13: Turbulent Nonpremixed Flames 14: Burning of Solids 15: Pollutant Emissions 16: Detonations Appendix A: Selected Thermodynamic Propertiesof Gases Comprising C-H-O-N System Appendix B: Fuel Properties Appendix C: Selected Properties of Air, Nitrogen, and Oxygen Appendix D: Diffusion Coefficients and Methodology for their Estimation Appendix E: Generalized Newton's Method for the Solution of Nonlinear Equations Appendix F: Computer Codes for Equilibrium Products of Hydrocarbon-Air Combustion
2,129 citations
"A methodology for analysis of diese..." refers background or methods in this paper
...In case, the cell temperature is above 1800 K (Turns, 1996), NO concentrations are solved for using the above-mentioned three reactions....
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...The Extended Zeldovich model is widely used for predicting NOx formation in diesel engine simulations (Turns, 1996; Kong et al., 1995)....
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TL;DR: In this article, the RNG κ-e turbulence model derived by Yakhot and Orszag (1986) based on the Renormalization Group theory has been modified and applied to variable-density engine flows in the present study.
Abstract: The RNG κ-e turbulence model derived by Yakhot and Orszag (1986) based on the Renormalization Group theory has been modified and applied to variable-density engine flows in the present study. The original RNG-based turbulence transport approximations were developed formally for an incompressible flow. In order to account for flow compressibility the RNG e-equation is modified and closed through an isotropic rapid distortion analysis. Computations were made of engine compressing/expanding flows and the results were compared with available experimental observations in a production diesel engine geometry. The modified RNG κ-e model was also applied to diesel spray combustion computations. It is shown that the use of the RNG model is warranted for spray combustion modeling since the ratio of the turbulent to mean-strain time scales is appreciable due to spray-generated mean flow gradients, and the model introduces a term to account for these effects. Large scale flow structures are predicted which ar...
1,200 citations
"A methodology for analysis of diese..." refers background in this paper
...However, the RNG k – ε model is able to predict the trend of overall TKE variation sufficiently (Han and Reitz, 1995)....
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...k – ε model is able to predict the trend of overall TKE variation sufficiently (Han and Reitz, 1995)....
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