Modeling and Experimental Investigation of Methylcyclohexane Ignition in a Rapid Compression Machine PDF Download

Author: W. J. Pitz
Publisher:
ISBN:
Category :
Languages : en
Pages : 26

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Author: Zhandong Wang
Publisher: Springer
ISBN: 9811056935
Category : Science
Languages : en
Pages : 225

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This thesis investigates the combustion chemistry of cyclohexane, methylcyclohexane, and ethylcyclohexane on the basis of state-of-the-art synchrotron radiation photoionization mass spectrometry experiments, quantum chemistry calculations, and extensive kinetic modeling. It explores the initial decomposition mechanism and distribution of the intermediates, proposes a novel formation mechanism of aromatics, and develops a detailed kinetic model to predict the three cycloalkanes’ combustion properties under a wide range of conditions. Accordingly, the thesis provides an essential basis for studying much more complex cycloalkanes in transport fuels and has applications in engine and fuel design, as well as emission control.

Author: Colin Banyon
Publisher:
ISBN:
Category : Combustion engineering
Languages : en
Pages :

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Rapid compression machines (RCMs) are well characterized laboratory scale devices capable of achieving internal combustion (IC) engine relevant thermodynamic environments. These machines are often used to collect ignition delay times as targets for gas-phase chemical kinetic fuel autoigntion models. Modern RCMs utilize creviced piston(s) to improve charge homogeneity and allow for an adequate validation of detailed chemistry mechanisms against experiments using computationally efficient, homogeneous reactor models (HRMs). Conventionally, experiments are preformed by introducing a premixed gas of fuel + oxidizer + diluent into the machine, which is compressed volumetrically via a piston. Experiments investigating low-vapor pressure fuels (e.g. diesels, biodiesels, jet fuels, etc.) and surrogates can be conducted by preheating both the charge as well as the machine. This method of fuel loading can lead to pretest fuel pyrolysis as well as machine seal degradation. Under some conditions loading a fuel aerosol of finely atomized liquid droplets in an oxidizer + diluent bath gas (i.e. wet compression) has been suggested to extend the capabilities of RCM experiments to involatile fuels. This work investigates phase-change effects during RCM experiments, especially for aerosol-fueling conditions, while the methodology can be applied to gas-phase fuel experiments where fuel condensation can occur at the compressed conditions within the boundary layer region. To facilitate this study a reduced-order, physics-based model is used. This work highlights important machine-scale influences not investigated in previous work, and provides additional detail concerning an aerosol RCM{u2019}s capabilities and limitations. A transient formulation is developed for the multi-phase transport within the RCM reaction chamber as well as the flow to the piston crevice region during both the compression and delay periods. The goal of this work is threefold. First, an a priori knowledge of the stratification present under various conditions can help determine an optimum machine geometry so that discrepancies between experimental data sets and 0D kinetics simulations are minimized for involatile fuels. Second, the model is computationally tractable to prescribe heat loss rates to an HRM during simulations of experiments so that physical effects can be incorporated into simulations using detailed chemistry. Finally, heat loss rates that are prescribed to the HRM are only a function of machine geometry, and are independent of ad hoc and empirically derived fits that vary between facilities. Thus a more adequate comparison of data between RCM facilities and with existing literature can be made.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 14

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The use of gasoline in homogeneous charge compression ignition engines (HCCI) and in duel fuel diesel - gasoline engines, has increased the need to understand its compression ignition processes under engine-like conditions. These processes need to be studied under well-controlled conditions in order to quantify low temperature heat release and to provide fundamental validation data for chemical kinetic models. With this in mind, an experimental campaign has been undertaken in a rapid compression machine (RCM) to measure the ignition of gasoline mixtures over a wide range of compression temperatures and for different compression pressures. By measuring the pressure history during ignition, information on the first stage ignition (when observed) and second stage ignition are captured along with information on the phasing of the heat release. Heat release processes during ignition are important because gasoline is known to exhibit low temperature heat release, intermediate temperature heat release and high temperature heat release. In an HCCI engine, the occurrence of low-temperature and intermediate-temperature heat release can be exploited to obtain higher load operation and has become a topic of much interest for engine researchers. Consequently, it is important to understand these processes under well-controlled conditions. A four-component gasoline surrogate model (including n-heptane, iso-octane, toluene, and 2-pentene) has been developed to simulate real gasolines. An appropriate surrogate mixture of the four components has been developed to simulate the specific gasoline used in the RCM experiments. This chemical kinetic surrogate model was then used to simulate the RCM experimental results for real gasoline. The experimental and modeling results covered ultra-lean to stoichiometric mixtures, compressed temperatures of 640-950 K, and compression pressures of 20 and 40 bar. The agreement between the experiments and model is encouraging in terms of first-stage (when observed) and second-stage ignition delay times and of heat release rate. The experimental and computational results are used to gain insight into low and intermediate temperature processes during gasoline ignition.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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A computer model is used to examine oxidation of hydrocarbon fuels in a rapid compression machine. For one of the fuels studied, n-heptane, significant fuel consumption is computed to take place during the compression stroke under some operating conditions, while for the less reactive n-pentane, no appreciable fuel consumption occurs until after the end of compression. The third fuel studied, a 60 PRF mixture of iso-octane and n-heptane, exhibits behavior that is intermediate between that of n-heptane and n-pentane. The model results indicate that computational studies of rapid compression machine ignition must consider fuel reaction during compression in order to achieve satisfactory agreement between computed and experimental results.

Author:
Publisher: John Wiley & Sons
ISBN: 0470974028
Category : Technology & Engineering
Languages : en
Pages : 3888

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Erstmals eine umfassende und einheitliche Wissensbasis und Grundlage für weiterführende Studien und Forschung im Bereich der Automobiltechnik. Die Encyclopedia of Automotive Engineering ist die erste umfassende und einheitliche Wissensbasis dieses Fachgebiets und legt den Grundstein für weitere Studien und tiefgreifende Forschung. Weitreichende Querverweise und Suchfunktionen ermöglichen erstmals den zentralen Zugriff auf Detailinformationen zu bewährten Branchenstandards und -verfahren. Zusammenhängende Konzepte und Techniken aus Spezialbereichen lassen sich so einfacher verstehen. Neben traditionellen Themen des Fachgebiets beschäftigt sich diese Enzyklopädie auch mit "grünen" Technologien, dem Übergang von der Mechanik zur Elektronik und den Möglichkeiten zur Herstellung sicherer, effizienterer Fahrzeuge unter weltweit unterschiedlichen wirtschaftlichen Rahmenbedingungen. Das Referenzwerk behandelt neun Hauptbereiche: (1) Motoren: Grundlagen; (2) Motoren: Design; (3) Hybrid- und Elektroantriebe; (4) Getriebe- und Antriebssysteme; (5) Chassis-Systeme; (6) Elektrische und elektronische Systeme; (7) Karosserie-Design; (8) Materialien und Fertigung; (9) Telematik. - Zuverlässige Darstellung einer Vielzahl von Spezialthemen aus dem Bereich der Automobiltechnik. - Zugängliches Nachschlagewerk für Jungingenieure und Studenten, die die technologischen Grundlagen besser verstehen und ihre Kenntnisse erweitern möchten. - Wertvolle Verweise auf Detailinformationen und Forschungsergebnisse aus der technischen Literatur. - Entwickelt in Zusammenarbeit mit der FISITA, der Dachorganisation nationaler Automobil-Ingenieur-Verbände aus 37 Ländern und Vertretung von über 185.000 Ingenieuren aus der Branche. - Erhältlich als stets aktuelle Online-Ressource mit umfassenden Suchfunktionen oder als Print-Ausgabe in sechs Bänden mit über 4.000 Seiten. Ein wichtiges Nachschlagewerk für Bibliotheken und Informationszentren in der Industrie, bei Forschungs- und Schulungseinrichtungen, Fachgesellschaften, Regierungsbehörden und allen Ingenieurstudiengängen. Richtet sich an Fachingenieure und Techniker aus der Industrie, Studenten höherer Semester und Studienabsolventen, Forscher, Dozenten und Ausbilder, Branchenanalysen und Forscher.

Author:
Publisher: Elsevier
ISBN: 0444640886
Category : Technology & Engineering
Languages : en
Pages : 1034

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Mathematical Modelling of Gas-Phase Complex Reaction Systems: Pyrolysis and Combustion, Volume 45, gives an overview of the different steps involved in the development and application of detailed kinetic mechanisms, mainly relating to pyrolysis and combustion processes. The book is divided into two parts that cover the chemistry and kinetic models and then the numerical and statistical methods. It offers a comprehensive coverage of the theory and tools needed, along with the steps necessary for practical and industrial applications. Details thermochemical properties and "ab initio" calculations of elementary reaction rates Details kinetic mechanisms of pyrolysis and combustion processes Explains experimental data for improving reaction models and for kinetic mechanisms assessment Describes surrogate fuels and molecular reconstruction of hydrocarbon liquid mixtures Describes pollutant formation in combustion systems Solves and validates the kinetic mechanisms using numerical and statistical methods Outlines optimal design of industrial burners and optimization and dynamic control of pyrolysis furnaces Outlines large eddy simulation of turbulent reacting flows

Author:
Publisher:
ISBN:
Category : Internal combustion engines
Languages : en
Pages : 592

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Mickael Chomier
Publisher:
ISBN:
Category : Chemical kinetics
Languages : en
Pages : 72

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The objective of this thesis is to understand the influence of the non-ideal effects in Rapid Compression Machines (RCM), namely the vortex roll-up and mass flow into the crevice, on autoignition. The effect of the vortex roll-up is studied computationally using CFD simulations of autoignition in a RCM. Whereas, the effect of the crevice mass flow is investigated experimentally by studying isooctane autoignition. Over the last two decades, experimental data of the nature of species evolution profiles and ignition delays from RCMs has been used to develop and validate chemical kinetic mechanisms at low-to-intermediate temperatures and elevated pressures. A significant portion of this overall dataset is from RCMs that had not employed a creviced piston to contain the roll-up vortex. The detrimental influence of the roll-up vortex and the thermokinetic interactions due to the resulting temperature non-homogeneity during the negative temperature coefficient (ntc) regime have been documented in the literature. However, the adequacy of the homogeneous modeling of RCMs without creviced pistons during reactive conditions has not been investigated. In this work, computational fluid dynamics simulations of an RCM without a creviced piston are conducted for autoignition of n-heptane over the entire ntc regime over a range of compressed pressures from 5 to 18 bar. The results from the CFD simulations highlight the non-homogeneity of autoignition and reveal significant quantitative discrepancy in comparison to homogeneous modeling, particularly for the hot ignition delay in the ntc regime. Specifically, the roll-up vortex induced temperature non-homogeneity leads to diminution of the ntc behavior. The experimental data from RCMs without creviced piston needs to be taken with caution for quantitative validation and refinement of kinetic mechanism, particularly at conditions when ntc behavior is highly pronounced. Rapid Compression Machines (RCMs) often employ creviced pistons to suppress the formation of the roll-up vortex. However, the use of a creviced piston promotes mass flow into the crevice when heat release takes place in the main combustion chamber. This multi-dimensional effect is not accounted for in the prevalent volumetric expansion approach for modeling RCMs. The method of crevice containment, on the other hand, avoids post-compression mass flow into the crevice. In order to assess the effect of the crevice mass flow on ignition in a RCM, experiments were conducted for autoignition of isooctane in a RCM with creviced piston in the temperature range of 680-940 K and at compressed pressures of ~15.5 and 20.5 bar in two ways. In one situation, post-compression mass flow to the crevice is avoided by crevice containment and in other it is allowed. Experiments show that the crevice mass flow can lead to significantly longer ignition delays. Experimental data from both scenarios is modeled using adiabatic volumetric expansion approach and an available kinetic mechanism. The simulated results show less pronounced effect of crevice mass flow on ignition delay and highlight the deficiency of the volumetric expansion method owing to its inability to describe coupled physical-chemical processes in the presence of heat release. Results indicate that it is important to include crevice mass flow in the physical model for improved modeling of experimental data from RCMs for consistent interpretation of chemical kinetics. The use of crevice containment, however, avoids the issue of mass flow altogether and offers an alternative and sound approach.