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Author : Stephen Johnson
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)
Download or read book A Quasi-dimensional Model for Performance and Emissions Predictions in a Dual Fuel Engine written by Stephen Johnson and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Qirui Yang
Publisher : Springer Nature
ISBN 13 : 3658357746
Total Pages : 141 pages
Book Rating : 4.6/5 (583 download)
Download or read book A Quasi-dimensional Charge Motion and Turbulence Model for Combustion and Emissions Prediction in Diesel Engines with a fully Variable Valve Train written by Qirui Yang and published by Springer Nature. This book was released on 2021-10-01 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: Qirui Yang develops a model chain for the simulation of combustion and emissions of diesel engine with fully variable valve train (VVT) based on extensive 3D-CFD simulations, and experimental measurements on the engine test bench. The focus of the work is the development of a quasi-dimensional (QDM) flow model, which sets up a series of sub-models to describe phenomenologically the swirl, squish and axial charge motions as well as the shear-related turbulence production and dissipation. The QDM flow model is coupled with a QDM combustion model and a nitrogen oxides (NOx) / soot emission model. With the established model chain, VVT operating strategies of diesel engine can be developed and optimized as part of the simulation for specific engine performance parameters and the lowest NOx and soot emissions.
Author : National Aeronautics and Space Adm Nasa
Publisher : Independently Published
ISBN 13 : 9781731186041
Total Pages : 74 pages
Book Rating : 4.1/5 (86 download)
Download or read book Three-Dimensional Modeling of Diesel Engine Intake Flow, Combustion and Emissions written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-11-12 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: A three-dimensional computer code (KIVA) is being modified to include state-of-the-art submodels for diesel engine flow and combustion: spray atomization, drop breakup/coalescence, multi-component fuel vaporization, spray/wall interaction, ignition and combustion, wall heat transfer, unburned HC and NOx formation, soot and radiation, and the intake flow process. Improved and/or new submodels which were completed are: wall heat transfer with unsteadiness and compressibility, laminar-turbulent characteristic time combustion with unburned HC and Zeldo'vich NOx, and spray/wall impingement with rebounding and sliding drops. Results to date show that adding the effects of unsteadiness and compressibility improves the accuracy of heat transfer predictions; spray drop rebound can occur from walls at low impingement velocities (e.g., in cold-starting); larger spray drops are formed at the nozzle due to the influence of vaporization on the atomization process; a laminar-and-turbulent characteristic time combustion model has the flexibility to match measured engine combustion data over a wide range of operating conditions; and finally, the characteristic time combustion model can also be extended to allow predictions of ignition. The accuracy of the predictions is being assessed by comparisons with available measurements. Additional supporting experiments are also described briefly. To date, comparisons with measured engine cylinder pressure and heat flux data were made for homogeneous charge, spark-ignited and compression-ignited engines. The model results are in good agreement with the experiments. Reitz, R. D. and Rutland, C. J. Unspecified Center...
Author : Y. Zhaoda
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (137 download)
Download or read book Predictive Model for Dual Fuel DI Diesel Engine Performance and Emission written by Y. Zhaoda and published by . This book was released on 1991 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : P. A. Lakshminarayanan
Publisher : Springer Nature
ISBN 13 : 981166742X
Total Pages : 419 pages
Book Rating : 4.8/5 (116 download)
Download or read book Modelling Diesel Combustion written by P. A. Lakshminarayanan and published by Springer Nature. This book was released on 2022-01-21 with total page 419 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book comprehensively discusses diesel combustion phenomena like ignition delay, fuel-air mixing, rate of heat release, and emissions of smoke, particulate and nitric oxide. It enables quantitative evaluation of these important phenomena and parameters. Most importantly, it attempts to model them with constants that are independent of engine types and hence they could be applied by the engineers and researchers for a general engine. This book emphasizes the importance of the spray at the wall in precisely describing the heat release and emissions for most of the engines on and off-road. It gives models for heat release and emissions. Every model is thoroughly validated by detailed experiments using a broad range of engines. The book describes an elegant quasi-one-dimensional model for heat release in diesel engines with single as well as multiple injections. The book describes how the two aspects, namely, fuel injection rate and the diameter of the combustion bowl in the piston, have enabled meeting advanced emission, noise, and performance standards. The book also discusses the topics of computational fluid dynamics encompassing RANS and LES models of turbulence. Given the contents, this book will be useful for students, researchers and professionals working in the area of vehicle engineering and engine technology. This book will also be a good professional book for practising engineers in the field of combustion engines and automotive engineering.
Author : M Muralidharan
Publisher : Mohammed Abdul Sattar
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.2/5 (249 download)
Download or read book Optimizing the Performance and Emissions of an Advanced Diesel Engine for Dual Fuel Operation written by M Muralidharan and published by Mohammed Abdul Sattar. This book was released on 2024-03-24 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Energy is widely regarded as one of the key contributors to economic development and personal comfort. Economic expansion and energy use are closely related to one another. The availability of affordable, environmentally acceptable energy sources is necessary for the growth of an economy and for it to remain competitive on a global scale. Conversely, the level of economic development is considered to be affected by energy consumption. Due to rising population and economic development, consumption has recently increased. We are fortunate to have both moderate and renewable energy resources. We lack resources with a high energy density, such as nuclear power plants and fossil fuels. Diesel engines have slowly become more popular over the past century as a fuel-efficient and dependable form of transportation for commodities and the general public, as well as for other essential social needs, including small-scale power generation and other similar activities. They often have advantages over spark-ignition engines due to their reduced regulated emissions of CO, unburned HC & carbon dioxide (CO2) and better thermal efficiency. Diesel engines also have the advantage of using low-energy alternative fuels like biogas since they can run at a higher compression ratio. On the other hand, diesel engines generate dangerous pollutants, including PM and NOx. Because of their potential health hazards and effect on visibility, these emissions are a hazard. When exposed, particulate emissions have the potential to cause occupational cancer and have a number of other negative health effects. Diesel engines, when used as part of a transportation system, are widely acknowledged as a significant source of ambient particulate matter. Natural gas, a widely recognized gaseous alternative fuel, consists of various gas species and is derived from fossil sources. It is possible to find fossil natural gas either by itself or in conjunction with other fossil fuels (eg, coal in coal beds and crude oil in oil fields). Natural gas's properties are fundamentally identical to those of methane (CH4) which is its principal composition.
Author : Gunnar Stiesch
Publisher : Springer Science & Business Media
ISBN 13 : 9783540006824
Total Pages : 314 pages
Book Rating : 4.0/5 (68 download)
Download or read book Modeling Engine Spray and Combustion Processes written by Gunnar Stiesch and published by Springer Science & Business Media. This book was released on 2003-04-10 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: The utilization of mathematical models to numerically describe the performance of internal combustion engines is of great significance in the development of new and improved engines. Today, such simulation models can already be viewed as standard tools, and their importance is likely to increase further as available com puter power is expected to increase and the predictive quality of the models is constantly enhanced. This book describes and discusses the most widely used mathematical models for in-cylinder spray and combustion processes, which are the most important subprocesses affecting engine fuel consumption and pollutant emissions. The relevant thermodynamic, fluid dynamic and chemical principles are summarized, and then the application of these principles to the in-cylinder processes is ex plained. Different modeling approaches for the each subprocesses are compared and discussed with respect to the governing model assumptions and simplifica tions. Conclusions are drawn as to which model approach is appropriate for a specific type of problem in the development process of an engine. Hence, this book may serve both as a graduate level textbook for combustion engineering stu dents and as a reference for professionals employed in the field of combustion en gine modeling. The research necessary for this book was carried out during my employment as a postdoctoral scientist at the Institute of Technical Combustion (ITV) at the Uni versity of Hannover, Germany and at the Engine Research Center (ERC) at the University of Wisconsin-Madison, USA.
Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
ISBN 13 : 9781722842024
Total Pages : 72 pages
Book Rating : 4.8/5 (42 download)
Download or read book Three-Dimensional Modeling of Diesel Engine Intake Flow, Combustion and Emissions written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-17 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: A three-dimensional computer code (KIVA) is being modified to include state-of-the-art submodels for diesel engine flow and combustion: spray atomization, drop breakup/coalescence, multi-component fuel vaporization, spray/wall interaction, ignition and combustion, wall heat transfer, unburned HC and NOx formation, soot and radiation, and the intake flow process. Improved and/or new submodels which were completed are: wall heat transfer with unsteadiness and compressibility, laminar-turbulent characteristic time combustion with unburned HC and Zeldo'vich NOx, and spray/wall impingement with rebounding and sliding drops. Results to date show that adding the effects of unsteadiness and compressibility improves the accuracy of heat transfer predictions; spray drop rebound can occur from walls at low impingement velocities (e.g., in cold-starting); larger spray drops are formed at the nozzle due to the influence of vaporization on the atomization process; a laminar-and-turbulent characteristic time combustion model has the flexibility to match measured engine combustion data over a wide range of operating conditions; and finally, the characteristic time combustion model can also be extended to allow predictions of ignition. The accuracy of the predictions is being assessed by comparisons with available measurements. Additional supporting experiments are also described briefly. To date, comparisons with measured engine cylinder pressure and heat flux data were made for homogeneous charge, spark-ignited and compression-ignited engines. The model results are in good agreement with the experiments. Reitz, R. D. and Rutland, C. J. Unspecified Center...
Author : Kevin Alexander
Publisher :
ISBN 13 :
Total Pages : 57 pages
Book Rating : 4.:/5 (96 download)
Download or read book Prediction of Performance and Emissions of Diesel Engine by Using Artificial Neural Network written by Kevin Alexander and published by . This book was released on 2009 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Takuji Ishiyama
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (54 download)
Download or read book Improvement of Performance and Exhaust Emissions in a Converted Dual-fuel Natural Gas Engine written by Takuji Ishiyama and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Vaibhav Kailas Ahire
Publisher :
ISBN 13 :
Total Pages : 230 pages
Book Rating : 4.:/5 (126 download)
Download or read book Physics-based Diesel Engine Model Development, Calibration and Validation for Accurate Cylinder Parameters and Nox Prediction written by Vaibhav Kailas Ahire and published by . This book was released on 2021 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stringent regulatory requirements and modern diesel engine technologies have engaged automotive manufacturers and researchers in accurately predicting and controlling diesel engine-out emissions. As a result, engine control systems have become more complex and opaquer, increasing the development time and costs. To address this challenge, Model-based control methods are an effective way to deal with the criticality of the system study and controls. And physics-based combustion engine modeling is a key to achieve it. This thesis focuses on development and validation of a physics-based model for both engine and emissions using model-based design tools from MATLAB & Simulink. Engine model equipped with exhaust gas circulation and variable geometry turbine is adopted from the previously done work which was then integrated with the combustion and emission model that predicts the heat release rates and NOx emission from engine. Combustion model is designed based on the mass fraction burnt from CA10 to CA90 and then NOx predicted using the extended Zeldovich mechanism. The engine models are tuned for both steady state and dynamics test points to account for engine operating range from the performance data. Various engine and combustion parameters are estimated using parameter estimation toolbox from MATLAB and Simulink by applying the least squared solver to minimize the error between measured and estimated variables. This model is validated against the virtual engine model developed in GT-power for Cummins 6.7L turbo diesel engine. To account for the harmonization of the testing cycles to save engine development time globally, a world harmonized stationary cycle (WHSC) is used for the validation. Sub-systems are validated individually as well as in a loop with a complete model for WHSC. Engine model validation showed promising accuracy of more than 88.4 percent on average for the desired parameters required for the NOx prediction. NOx estimation is accurate for the cycle except the warm-up and cool-down phase. However, NOx prediction during these phases is limited due to actual NOx measured data for tuning the model for real-time NOx estimation. Results are summarized at the end to compare the trend of NOx estimation from the developed combustion and emission model to show the accuracy of in-cylinder parameters and required for the NOx estimation.
Author : Arash Jamali
Publisher :
ISBN 13 :
Total Pages : 124 pages
Book Rating : 4.:/5 (958 download)
Download or read book Numerical Simulation of Combustion and Unburnt Products in Dual-fuel Compression-ignition Engines with Multiple Injection written by Arash Jamali and published by . This book was released on 2015 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: Natural gas substitution for diesel can result in significant reduction in pollutant emissions. Based on current fuel price projections, operating costs would be lower. With a high ignition temperature and relatively low reactivity, natural gas can enable promising approaches to combustion engine design. In particular, the combination of low reactivity natural gas and high reactivity diesel may allow for optimal operation as a reactivity-controlled compression ignition (RCCI) engine, which has potential for high efficiency and low emissions. In this computational study, a lean mixture of natural gas is ignited by direct injection of diesel fuel in a model of the heavy-duty CAT3401 diesel engine. Dual-fuel combustion of natural gas-diesel (NGD) may provide a wider range of reactivity control than other dual-fuel combustion strategies such as gasoline-diesel dual fuel. Accurate and efficient combustion modeling can aid NGD dual-fuel engine control and optimization. In this study, multi-dimensional simulation was performed using a nite-volume computational code for fuel spray, combustion and emission processes. Adaptive mesh refinement (AMR) and multi-zone reaction modeling enables simulation in a reasonable time. The latter approach avoids expensive kinetic calculations in every computational cell, with considerable speedup. Two approaches to combustion modeling are used within the Reynolds averaged Navier-Stokes (RANS) framework. The first approach uses direct integration of the detailed chemistry and no turbulence-chemistry interaction modeling. The model produces encouraging agreement between the simulation and experimental data. For reasonable accuracy and computation cost, a minimum cell size of 0.2 millimeters is suggested for NGD dual-fuel engine combustion. In addition, the role of different chemical reaction mechanism on the NGD dual-fuel combustion is considered with this model. This work considers fundamental questions regarding combustion in NGD dual-fuel combustion, particularly about how and where fuels react, and the difference between combustion in the dual fuel mode and conventional diesel mode. The results show that in part-load working condition main part of CH4 cannot burn and it has significant effect in high level of HC emission in NGD dual-fuel engine. The CFD results reveal that homogeneous mixture of CH4 and air is too lean, and it cannot ignite in regions that any species from C7H16 chemical mechanism does not exist. It is shown that multi-injection of diesel fuel with an early main injection can reduce HC emission significantly in the NGD dual-fuel engine. In addition, the results reveal that increasing the air fuel ratio by decreasing the air amount could be a promising idea for HC emission reduction in NGD dual-fuel engine, too.
Author : Pankaj Kumar
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (798 download)
Download or read book Low-dimensional Models for Real-time Simulation of Internal Combustion Engines and Catalytic After-treatment Systems written by Pankaj Kumar and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The current trend towards simultaneously increasing fuel-to-wheels efficiency while reducing emissions from transportation system powertrains requires system level optimization realized through real-time multivariable control. Such an optimization can be accomplished using low-order fundamentals (first-principles) based models for each of the engine sub-systems, i.e. in-cylinder combustion processes, exhaust after-treatment systems, mechanical and electrical systems (for hybrid vehicles) and sensor and control systems. In this work, we develop a four-mode low-dimensional model for the in-cylinder combustion process in an internal combustion engine. The lumped parameter ordinary differential equation model is based on two mixing times that capture the reactant diffusional limitations inside the cylinder and mixing limitations caused by the input and exit stream distribution. For given fuel inlet conditions, the model predicts the exhaust composition of regulated gases (total unburned HC's, CO, and NOx as well as the in-cylinder pressure and temperature. The results show good qualitative and fair quantitative agreement with the experimental results published in the literature and demonstrate the possibility of such low-dimensional model for real-time control. In the second part of this work, we propose a low-dimensional model of the three-way catalytic converter (TWC) for control and diagnostics. Traditionally, the TWC is controlled via an inner-loop and outer-loop strategy using a downstream and upstream oxygen sensor. With this control structure, we rely on the oxygen sensor voltage to indicate whether the catalyst has saturated. However, if the oxidation state of the catalyst could be estimated, than a more pro-active TWC control strategy would be feasible. A reduced order model is achieved by approximating the transverse gradients using multiple concentration modes and the concepts of internal and external mass transfer coefficients, spatial averaging over the axial length and simplified chemistry by lumping the oxidants and the reductants. The model performance is tested and validated using data on actual vehicle emissions resulting in good agreement. The computational efficiency and the ability of the model to predict fractional oxidation state (FOS) and total oxygen storage capacity (TOSC) make it a novel tool for real-time fueling control to minimize emissions and diagnostics of catalyst aging.
Author :
Publisher :
ISBN 13 :
Total Pages : 62 pages
Book Rating : 4.:/5 (682 download)
Download or read book Three-dimensional Modeling of Diesel Engine Intake Flow, Combustion and Emissions-II. written by and published by . This book was released on 1993 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: A three-dimensional computer code, KIVA, is being modified to include state-of-the-art submodels for diesel engine flow and combustion. Improved and/or new submodels which have already been implemented and previously reported are: Wall heat transfer with unsteadiness and compressibility, laminar-turbulent characteristic time combustion with unburned HC and Zeldo'vich NO(subscript x), and spray/wall impingement with rebounding and sliding drops. Progress on the implementation of improved spray drop drag and drop breakup models, the formulation and testing of a multistep kinetics ignition model and preliminary soot modeling results are described in this report. In addition, the use of a block structured version of KIVA to model the intake flow process is described. A grid generation scheme has been developed for modeling realistic (complex) engine geometries, and computations have been made of intake flow in the ports and combustion chamber of a two-intake-valve engine. The research also involves the use of the code to assess the effects of subprocesses on diesel engine performance. The accuracy of the predictions is being tested by comparisons with engine experiments. To date, comparisons have been made with measured engine cylinder pressure, temperature and heat flux data, and the model results are in good agreement with the experiments. Work is in progress that will allow validation of in-cylinder flow and soot formation predictions. An engine test facility is described that is being used to provide the needed validation data. Test results have been obtained showing the effect of injection rate and split injections on engine performance and emissions.
Author : Amin Yousefi
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (135 download)
Download or read book Experimental and Numerical Study of the Combustion and Emissions of Natural Gas/diesel Dual-fuel Engine Under Different Engine Load-speed Conditions written by Amin Yousefi and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Universal concerns about degradation in air quality, stringent emissions regulations, energy scarcity, and global warming have prompted research and development of compressed ignition engines using alternative combustion concepts. Natural gas/diesel dual-fuel combustion is an advanced combustion concept for compression ignition diesel engines, which has attracted global attention in recent years. This combustion concept is accomplished by creating reactivity stratification in the cylinder via the use of two fuels characterized by distinctly different reactivities. The low reactivity and main fuel (i.e., natural gas) is firstly premixed with air and then charged into the cylinder through the intake manifold, and the high reactivity fuel (i.e., diesel) is then injected into the charged mixture through a direct injector. This combustion concept offers prominent benefits in terms of a significant reduction of particulate matter (PM) and sometimes nitrogen oxides (NOx) emissions while maintaining comparable fuel efficiency compared to diesel engine. However, low thermal efficiency and high greenhouse gas (GHG) emissions under low load conditions are major challenges which prevented the implementation of dual-fuel concept in commercial automative engines. The present study investigates different combustion approaches with the aim to enhance combustion performance and reduce emissions of unburned methane, CO, NOx, soot, and GHG of natural gas/diesel dual-fuel engines under different engine load-speed conditions. In particular, the main focus of this thesis is on low load conditions where GHG emissions of conventional natural gas/diesel dual-fuel engine is much higher than that of conventional diesel engine. Alongside the experimental study, a computational fluid dynamic (CFD) model is developed to help understand the behaviour of natural gas/diesel dual-fuel combustion process under different engine load-speed conditions. The studied approaches showed that the fuel efficiency and GHG emissions of natural gas/diesel dual-fuel engine can be significantly improved under low engine load conditions compared to diesel engine.
Author :
Publisher :
ISBN 13 :
Total Pages : 10 pages
Book Rating : 4.:/5 (873 download)
Download or read book Chemical Kinetic Models for HCCI and Diesel Combustion written by and published by . This book was released on 2010 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: Predictive engine simulation models are needed to make rapid progress towards DOE's goals of increasing combustion engine efficiency and reducing pollutant emissions. These engine simulation models require chemical kinetic submodels to allow the prediction of the effect of fuel composition on engine performance and emissions. Chemical kinetic models for conventional and next-generation transportation fuels need to be developed so that engine simulation tools can predict fuel effects. The objectives are to: (1) Develop detailed chemical kinetic models for fuel components used in surrogate fuels for diesel and HCCI engines; (2) Develop surrogate fuel models to represent real fuels and model low temperature combustion strategies in HCCI and diesel engines that lead to low emissions and high efficiency; and (3) Characterize the role of fuel composition on low temperature combustion modes of advanced combustion engines.
Author :
Publisher :
ISBN 13 :
Total Pages : 364 pages
Book Rating : 4.:/5 (941 download)
Download or read book Development of a Phase Stability-based Fuel Condensation Model for Advanced Low Temperature Combustion Engines written by and published by . This book was released on 2016 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ever-more stringent legislative regulations on harmful emissions and fuel efficiency have driven researchers to develop cleaner and more efficient internal combustion engines. Research studies have shown that low temperature combustion can produce very low NOx and soot emissions while obtaining diesel-like high thermal efficiency. One strategy is reactivity controlled compression ignition (RCCI) combustion, which has been shown to be more practical and applicable than homogeneous charge compression ignition (HCCI) by providing extra controllability on the combustion processes, including for the combustion phasing and duration. However, recent experimental work has shown that more than 95% of the particulate matter from RCCI combustion consists of organic species, which is drastically different from conventional diesel combustion (CDC), which mainly produces carbonaceous soot. This distinctive character is believed to be related to condensation processes of large hydrocarbon species that cannot stably exist in the gas phase. Rather, under certain conditions the heavy gaseous species can condense and they become responsible for the organic fraction of the particulate matter. To investigate this physical phenomenon, a thermodynamically consistent, robust and efficient phase equilibrium solver, which performs rigorous phase stability tests and phase splitting calculations with advanced numerical algorithms, was developed. This is a first step forward modeling condensation processes in engines. Potential phase separation and combination are considered using Gibbs free energy minimization and entropy maximization. The numerical solver was well validated on a number of mixtures in two- and three-phase equilibria with available data. It was also applied to study the complex phase behavior of mixtures, including multiphase dynamic flash calculations, supercritical fluid behavior, condensation and evaporation, PVT analysis and critical point behavior. In addition, the developed model was coupled with an open-source CFD code, KIVA, widely used for multi-dimensional engine spray and combustion simulations, thus enabling a consistent treatment of both the fluid dynamics and thermodynamics. The model was used to investigate a number of two-phase flow problems, including regular condensation in a nozzle, retrograde condensation in a shock tube, condensation processes during supercritical fuel injection, and condensation in an engine combustion chamber. The simulations were validated using available experiments for both pure species and mixtures, ranging from subcritical to supercritical flows. The thermodynamic equilibrium analysis was also applied to study engine fuel condensation processes under non-reacting conditions. First, simulations were performed for Sandia optical combustion vessels and engines with direct injection of a diesel jet into a pure nitrogen environment. Consistent with experiments, the simulations show that condensation of previously evaporated fuel takes place during the expansion stroke. For high-pressure fuel injection of an n-alkane fuel, there are local sub-critical conditions under which phase separation can take place. This is because of the significant reduction of the mixture temperature caused by vaporization and cooling of the cold liquid fuel. Therefore, even though the ambient conditions during injection are supercritical relative to the fuel, the actual mixture temperature can be much lower so that the mixture enters into the two-phase region. The phase equilibrium model was finally applied to study fuel condensation processes in a RCCI combustion engine. Condensation was predicted during the late stages of the expansion stroke, when the continuous expansion sends the local fluid into the two-phase region again. The condensed fuel is shown to affect emission predictions, including engine-out particulate matter and unburned hydrocarbons. Consistent with experiments, the organic fraction mass from the condensed fuel is predicted to be the majority (more than 99%) of the total particulate matter. Also, as the engine operation changes from low to high load, fuel condensation is significantly reduced due to the higher temperatures and pressures, and the engine-out PM is predicted to be mainly composed of solid carbonaceous soot particles.
