Computational Studies of Gas Injection, Ignition and Combustion Emissions in a Direct-injection Natural Gas Engine PDF Download
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Author: Kang Pan
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The direct-injection of natural gas into the compression-ignition engines is attractive, due to its emission advantage and diesel-equivalent efficiency. The computational simulation of this next-generation heavy-duty engine can provide deep insights of the gas injection and ignition characteristics and help understand the emission formation process, and hence, a KIVA-3v based three-dimensional computational model was developed and improved to represent the configuration of a glow plug assisted direct-injection natural gas engine. This thesis presents the important conclusions about the numerical studies of the natural gas ignition and emissions by using this engine computational model. Preliminary simulations revealed that the shield for a glow plug, an ignition assist for natural gas in compression-ignition engines, can highly improve the natural gas ignition stability compared to an unshielded glow plug, and the design of the glow plug shield has great potential for the further improvement of the natural gas ignition. The different shield designs, characterized by the parameters such as shield opening shape, number and distribution, were evaluated by using the improved KIVA model. The simulated results clearly demonstrated the three key functions of a good shield design. A multi-opening shield, consisting of four small openings in a diamond shape, can achieve all three requirements and hence highly reduce the natural gas ignition delay and improve the ignition stability, compared to the original single-opening shield. The proper emission models are critical for the numerical simulations of natural gas engine emissions. For the gaseous species, a kinetic package, CANTERA, is coupled to KIVA CFD code to simulate the formation of important emissions, such as C2H2 and NOx. However, the available detailed mechanisms, such as GRI-3.0, will over-predict the ignition delay at low temperature (
Author: Kang Pan
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The direct-injection of natural gas into the compression-ignition engines is attractive, due to its emission advantage and diesel-equivalent efficiency. The computational simulation of this next-generation heavy-duty engine can provide deep insights of the gas injection and ignition characteristics and help understand the emission formation process, and hence, a KIVA-3v based three-dimensional computational model was developed and improved to represent the configuration of a glow plug assisted direct-injection natural gas engine. This thesis presents the important conclusions about the numerical studies of the natural gas ignition and emissions by using this engine computational model. Preliminary simulations revealed that the shield for a glow plug, an ignition assist for natural gas in compression-ignition engines, can highly improve the natural gas ignition stability compared to an unshielded glow plug, and the design of the glow plug shield has great potential for the further improvement of the natural gas ignition. The different shield designs, characterized by the parameters such as shield opening shape, number and distribution, were evaluated by using the improved KIVA model. The simulated results clearly demonstrated the three key functions of a good shield design. A multi-opening shield, consisting of four small openings in a diamond shape, can achieve all three requirements and hence highly reduce the natural gas ignition delay and improve the ignition stability, compared to the original single-opening shield. The proper emission models are critical for the numerical simulations of natural gas engine emissions. For the gaseous species, a kinetic package, CANTERA, is coupled to KIVA CFD code to simulate the formation of important emissions, such as C2H2 and NOx. However, the available detailed mechanisms, such as GRI-3.0, will over-predict the ignition delay at low temperature (
Author: Yu Shi
Publisher: Springer Science & Business Media
ISBN: 0857296191
Category : Technology & Engineering
Languages : en
Pages : 323
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Book Description
Computational Optimization of Internal Combustion Engines presents the state of the art of computational models and optimization methods for internal combustion engine development using multi-dimensional computational fluid dynamics (CFD) tools and genetic algorithms. Strategies to reduce computational cost and mesh dependency are discussed, as well as regression analysis methods. Several case studies are presented in a section devoted to applications, including assessments of: spark-ignition engines, dual-fuel engines, heavy duty and light duty diesel engines. Through regression analysis, optimization results are used to explain complex interactions between engine design parameters, such as nozzle design, injection timing, swirl, exhaust gas recirculation, bore size, and piston bowl shape. Computational Optimization of Internal Combustion Engines demonstrates that the current multi-dimensional CFD tools are mature enough for practical development of internal combustion engines. It is written for researchers and designers in mechanical engineering and the automotive industry.
Author:
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Category :
Languages : en
Pages :
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Abstract : Among the various alternative fuels, natural gas is considered as a leading candidate for heavy-duty applications due to its availability and applicability in conventional internal combustion diesel engines. Compared to their diesel counterparts natural gas fueled spark-ignited engines have a lower power density, reduced low-end torque capability, limited altitude performance, and ammonia emissions downstream of the three-way catalyst. The dual fuel diesel/natural gas engine does not suffer with the performance limitations of the spark-ignited concept due to the flexibility of switching between different fueling modes. Considerable research has already been conducted to understand the combustion behavior of dual fuel diesel/natural gas engines. As reported by most researchers, the major difficulty with dual fuel operation is the challenge of providing high levels of natural gas substitution, especially at low and medium loads. In this study extensive experimental and simulation studies were conducted to understand the combustion behavior of a heavy-duty diesel engine when operated with compressed natural gas (CNG) in a dual fuel regime. In one of the experimental studies, conducted on a 13 liter heavy-duty six cylinder diesel engine with a compression ratio of 16.7:1, it was found that at part loads high levels of CNG substitution could be achieved along with very low NOx and PM emissions by applying reactivity controlled compression ignition (RCCI) combustion. When compared to the diesel-only baseline, a 75% reduction in both NOx and PM emissions was observed at a 5 bar BMEP load point along with comparable fuel consumption values. Further experimental studies conducted on the 13 liter heavy-duty six cylinder diesel engine have shown that RCCI combustion targeting low NOx emissions becomes progressively difficult to control as the load is increased at a given speed or the speed is reduced at a given load. To overcome these challenges a number of simulation studies were conducted to quantify the in-cylinder conditions that are needed at high loads and low to medium engine speeds to effectively control low NOx RCCI combustion. A number of design parameters were analyzed in this study including exhaust gas recirculation (EGR) rate, CNG substitution, injection strategy, fuel injection pressure, fuel spray angle and compression ratio. The study revealed that lowering the compression ratio was very effective in controlling low NOx RCCI combustion. By lowering the base compression ratio by 4 points, to 12.7:1, a low NOx RCCI combustion was achieved at both 12 bar and 20 bar BMEP load points. The NOx emissions were reduced by 75% at 12 bar BMEP while fuel consumption was improved by 5.5%. For the 20 BMEP case, a 2% improvement in fuel consumption was achieved with an 87.5% reduction in NOx emissions. At both load points low PM emissions were observed with RCCI combustion. A low NOx RCCI combustion system has multiple advantages over other combustion approaches, these include; significantly lower NOx and PM emission which allows a reduction in aftertreatment cost and packaging requirements along with application of higher CNG substitution rates resulting in reduced CO2 emissions.
Author: H Zhao
Publisher: Elsevier
ISBN: 1845697324
Category : Technology & Engineering
Languages : en
Pages : 325
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Book Description
Direct injection enables precise control of the fuel/air mixture so that engines can be tuned for improved power and fuel economy, but ongoing research challenges remain in improving the technology for commercial applications. As fuel prices escalate DI engines are expected to gain in popularity for automotive applications. This important book, in two volumes, reviews the science and technology of different types of DI combustion engines and their fuels. Volume 1 deals with direct injection gasoline and CNG engines, including history and essential principles, approaches to improved fuel economy, design, optimisation, optical techniques and their applications. Reviews key technologies for enhancing direct injection (DI) gasoline engines Examines approaches to improved fuel economy and lower emissions Discusses DI compressed natural gas (CNG) engines and biofuels
Author: Xu (Stewart). Cheng
Publisher:
ISBN: 9780494578544
Category :
Languages : en
Pages : 494
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Book Description
With increasing concerns about the harmful effects of conventional liquid fossil fuel emissions, natural gas has become a very attractive alternative fuel to power prime movers and stationary energy conversion devices. This research studies the injection and ignition numerically for natural gas (mainly methane) as a fuel applied to diesel engine.Natural gas injector and glow plug ignition enhancement are two of the most technical difficulties for direct injection natural gas engine design. This thesis models the natural gas injector, and studies the characteristics of the internal flow in the injector and natural gas jet in the combustion chamber during the injection process. The poppet valve model and pintle valve model are the first reported models to simulate the natural gas injector to improve the traditional velocity and pressure boundary conditions.This thesis also successfully models the glow plug assisted natural gas ignition and combustion processes by developing a glow plug discretized model and a novel virtual gas sub-layer model. Glow plug discretized model can describe the transient heat transfer, and adequately represents the thin layers of heat penetration and the local temperature difference due to the cold gas jet impingement. The virtual gas sub-layer model considers complicated physical processes, such as chemical reaction, heat conduction, and mass diffusion within the virtual sub-layers without significantly increasing computational time and load.KIVA-3V CFD code was chosen to simulate the fluid flow. Since the KIVA-3V is designed specifically for engine research application with conventional liquid fuels, many modifications have been implemented to facilitate this research.
Author: Ivan Gogolev
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Natural gas direct injection and glow plug ignition assist technologies were implemented in a single-cylinder, optically-accessible engine. Initial experiments studied the effects of injector and glow plug shield geometry on ignition quality. Injector and shield geometric effects were found to be significant, with only two of 20 tested geometric combinations resulting in reproducible combustion. Further experiments explored the effects of equivalence ratio and intake pressure on ignition delay, engine performance, and exhaust emissions. Combustion was found to proceed in a stratified-premixed mode at lower equivalence ratios, and a free-mixing mode at the higher equivalence ratios. Both combustion modes resulted in high NOx emissions. Stratified-premixed combustion produced higher hydrocarbon emissions, and lower levels of particulate matter and carbon monoxide, when compared to free-mixing combustion. Higher intake pressure was found to reduce all emissions levels. This effect was largely attributed to better charge mixing achieved from pressure-driven increase in engine swirl momentum.
Author: P. A. Lakshminarayanan
Publisher: Springer Nature
ISBN: 9819706297
Category :
Languages : en
Pages : 678
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Author: Xu Jr Cheng
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: P. A. Lakshminarayanan
Publisher: Springer Nature
ISBN: 981166742X
Category : Technology & Engineering
Languages : en
Pages : 419
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Book Description
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: Hongsheng Guo
Publisher: Frontiers Media SA
ISBN: 2889666212
Category : Technology & Engineering
Languages : en
Pages : 125
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