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Analysis Of Homogeneous Charge Compression Ignition Hcci Engines For Cogeneration Applications
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Book Synopsis Analysis of Homogeneous Charge Compression Ignition (HCCI) Engines for Cogeneration Applications by : G. Reistad
Download or read book Analysis of Homogeneous Charge Compression Ignition (HCCI) Engines for Cogeneration Applications written by G. Reistad and published by . This book was released on 2004 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents an evaluation of the applicability of Homogeneous Charge Compression Ignition Engines (HCCI) for small-scale cogeneration (less than 1 MWe) in comparison to five previously analyzed prime movers. The five comparator prime movers include stoichiometric spark-ignited (SI) engines, lean burn SI engines, diesel engines, microturbines and fuel cells. The investigated option, HCCI engines, is a relatively new type of engine that has some fundamental differences with respect to other prime movers. Here, the prime movers are compared by calculating electric and heating efficiency, fuel consumption, nitrogen oxide (NOx) emissions and capital and fuel cost. Two cases are analyzed. In Case 1, the cogeneration facility requires combined power and heating. In Case 2, the requirement is for power and chilling. The results show that the HCCI engines closely approach the very high fuel utilization efficiency of diesel engines without the high emissions of NOx and the expensive diesel fuel. HCCI engines offer a new alternative for cogeneration that provides a unique combination of low cost, high efficiency, low emissions and flexibility in operating temperatures that can be optimally tuned for cogeneration systems. HCCI engines are the most efficient technology that meets the oncoming 2007 CARB NOx standards for cogeneration engines. The HCCI engine appears to be a good option for cogeneration systems and merits more detailed analysis and experimental demonstration.
Book Synopsis Control and Robustness Analysis of Homogeneous Charge Compression Ignition Using Exhaust Recompression by : Hsien-Hsin Liao
Download or read book Control and Robustness Analysis of Homogeneous Charge Compression Ignition Using Exhaust Recompression written by Hsien-Hsin Liao and published by Stanford University. This book was released on 2011 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt: There has been an enormous global research effort to alleviate the current and projected environmental consequences incurred by internal combustion (IC) engines, the dominant propulsion systems in ground vehicles. Two technologies have the potential to improve the efficiency and emissions of IC engines in the near future: variable valve actuation (VVA) and homogeneous charge compression ignition (HCCI). IC engines equipped with VVA systems are proven to show better performance by adjusting the valve lift and timing appropriately. An electro-hydraulic valve system (EHVS) is a type of VVA system that possesses full flexibility, i.e., the ability to change the valve lift and timing independently and continuously, making it an ideal rapid prototyping tool in a research environment. Unfortunately, an EHVS typically shows a significant response time delay that limits the achievable closed-loop bandwidth and, as a result, shows poor tracking performance. In this thesis, a control framework that includes system identification, feedback control design, and repetitive control design is presented. The combined control law shows excellent performance with a root-mean-square tracking error below 40 [Mu]m over a maximum valve lift of 4 mm. A stability analysis is also provided to show that the mean tracking error converges to zero asymptotically with the combined control law. HCCI, the other technology presented in this thesis, is a combustion strategy initiated by compressing a homogeneous air-fuel mixture to auto-ignition, therefore, ignition occurs at multiple points inside the cylinder without noticeable flame propagation. The result is rapid combustion with low peak in-cylinder temperature, which gives HCCI improved efficiency and reduces NOx formation. To initiate HCCI with a typical compression ratio, the sensible energy of the mixture needs to be high compared to a spark ignited (SI) strategy. One approach to achieve this, called recompression HCCI, is by closing the exhaust valve early to trap a portion of the exhaust gas in the cylinder. Unlike a SI or Diesel strategy, HCCI lacks an explicit combustion trigger, as autoignition is governed by chemical kinetics. Therefore, the thermo-chemical conditions of the air-fuel mixture need to be carefully controlled for HCCI to occur at the desired timing. Compounding this challenge in recompression HCCI is the re-utilization of the exhaust gas which creates cycle-to-cycle coupling. Furthermore, the coupling characteristics can change drastically around different operating points, making combustion timing control difficult across a wide range of conditions. In this thesis, a graphical analysis examines the in-cylinder temperature dynamics of recompression HCCI and reveals three qualitative types of temperature dynamics. With this insight, a switching linear model is formulated by combining three linear models: one for each of the three types of temperature dynamics. A switching controller that is composed of three local linear feedback controllers can then be designed based on the switching model. This switching model/control formulation is tested on an experimental HCCI testbed and shows good performance in controlling the combustion timing across a wide range. A semi-definite program is formulated to find a Lyapunov function for the switching model/control framework and shows that it is stable. As HCCI is dictated by the in-cylinder thermo-chemical conditions, there are further concerns about the robustness of HCCI, i.e., the boundedness of the thermo-chemical conditions with uncertainty existing in the ambient conditions and in the engine's own characteristics due to aging. To assess HCCI's robustness, this thesis presents a linear parameter varying (LPV) model that captures the dynamics of recompression HCCI and possesses an elegant model structure that is more amenable to analysis. Based on this model, a recursive algorithm using convex optimization is formulated to generate analytical statements about the boundedness of the in-cylinder thermo-chemical conditions. The bounds generated by the algorithm are also shown to relate well to the data from the experimental testbed.
Download or read book HCCI Combustion written by and published by . This book was released on 2001 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Homogeneous charge compression ignition (HCCI) is a new combustion technology that may develop as an alternative to diesel engines with high efficiency and low NOx and particulate matter emissions. This paper describes the HCCI research activities being currently pursued at Lawrence Livermore National Laboratory and at the University of California Berkeley. Current activities include analysis as well as experimental work. On analysis, we have developed two powerful tools: a single zone model and a multi-zone model. The single zone model has proven very successful in predicting start of combustion and providing reasonable estimates for peak cylinder pressure, indicated efficiency and NOX emissions. This model is being applied to develop detailed engine performance maps and control strategies, and to analyze the problem of engine startability. The multi-zone model is capable of very accurate predictions of the combustion process, including HC and CO emissions. The multi-zone model h as applicability to the optimization of combustion chamber geometry and operating conditions to achieve controlled combustion at high efficiency and low emissions. On experimental work, we have done a thorough evaluation of operating conditions in a 4-cylinder Volkswagen TDI engine. The engine has been operated over a wide range of conditions by adjusting the intake temperature and the fuel flow rate. Satisfactory operation has been obtained over a wide range of operating conditions. Cylinder-to-cylinder variations play an important role in limiting maximum power, and should be controlled to achieve satisfactory performance.
Book Synopsis Homogeneous Charge Compression Ignition (HCCI) by : Rudolf H. Stanglmaier
Download or read book Homogeneous Charge Compression Ignition (HCCI) written by Rudolf H. Stanglmaier and published by . This book was released on 1999 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Large reductions in low-load NOx emissions can be obtained by replacing conventional Diesel or spark ignited combustion by HCCI combustion in reciprocating engines. Currently, CCHI combustion is limited to operating conditions with lean air/fuel ratios or large amounts of EGR. However, a numerical model shows that, even if high equivalence ratio HCCI operation were satisfactory attained,.the NOx reduction potential vs. DI-Diesel combustion would be much smaller. Thus, high-load HCCI operation may be best obtained through highly boosted fuel-lean operation. Alternatively, HCCI combustion may be suited well for "dual mode" engine applications, in which spark ignition or conventional Diesel combustion is used to obtain fuel load. Avoiding wall impingement with heavy fuels is critical for achieving good emissions and fuel consumption, and it appears that a large degree of mixture inhomogeneity can be tolerated from a NOx benefit standpoint" -- Page 1.
Book Synopsis Control and Robustness Analysis of Homogeneous Charge Compression Ignition Using Exhaust Recompression by : Hsien-Hsin Liao
Download or read book Control and Robustness Analysis of Homogeneous Charge Compression Ignition Using Exhaust Recompression written by Hsien-Hsin Liao and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: There has been an enormous global research effort to alleviate the current and projected environmental consequences incurred by internal combustion (IC) engines, the dominant propulsion systems in ground vehicles. Two technologies have the potential to improve the efficiency and emissions of IC engines in the near future: variable valve actuation (VVA) and homogeneous charge compression ignition (HCCI). IC engines equipped with VVA systems are proven to show better performance by adjusting the valve lift and timing appropriately. An electro-hydraulic valve system (EHVS) is a type of VVA system that possesses full flexibility, i.e., the ability to change the valve lift and timing independently and continuously, making it an ideal rapid prototyping tool in a research environment. Unfortunately, an EHVS typically shows a significant response time delay that limits the achievable closed-loop bandwidth and, as a result, shows poor tracking performance. In this thesis, a control framework that includes system identification, feedback control design, and repetitive control design is presented. The combined control law shows excellent performance with a root-mean-square tracking error below 40 [Mu]m over a maximum valve lift of 4 mm. A stability analysis is also provided to show that the mean tracking error converges to zero asymptotically with the combined control law. HCCI, the other technology presented in this thesis, is a combustion strategy initiated by compressing a homogeneous air-fuel mixture to auto-ignition, therefore, ignition occurs at multiple points inside the cylinder without noticeable flame propagation. The result is rapid combustion with low peak in-cylinder temperature, which gives HCCI improved efficiency and reduces NOx formation. To initiate HCCI with a typical compression ratio, the sensible energy of the mixture needs to be high compared to a spark ignited (SI) strategy. One approach to achieve this, called recompression HCCI, is by closing the exhaust valve early to trap a portion of the exhaust gas in the cylinder. Unlike a SI or Diesel strategy, HCCI lacks an explicit combustion trigger, as autoignition is governed by chemical kinetics. Therefore, the thermo-chemical conditions of the air-fuel mixture need to be carefully controlled for HCCI to occur at the desired timing. Compounding this challenge in recompression HCCI is the re-utilization of the exhaust gas which creates cycle-to-cycle coupling. Furthermore, the coupling characteristics can change drastically around different operating points, making combustion timing control difficult across a wide range of conditions. In this thesis, a graphical analysis examines the in-cylinder temperature dynamics of recompression HCCI and reveals three qualitative types of temperature dynamics. With this insight, a switching linear model is formulated by combining three linear models: one for each of the three types of temperature dynamics. A switching controller that is composed of three local linear feedback controllers can then be designed based on the switching model. This switching model/control formulation is tested on an experimental HCCI testbed and shows good performance in controlling the combustion timing across a wide range. A semi-definite program is formulated to find a Lyapunov function for the switching model/control framework and shows that it is stable. As HCCI is dictated by the in-cylinder thermo-chemical conditions, there are further concerns about the robustness of HCCI, i.e., the boundedness of the thermo-chemical conditions with uncertainty existing in the ambient conditions and in the engine's own characteristics due to aging. To assess HCCI's robustness, this thesis presents a linear parameter varying (LPV) model that captures the dynamics of recompression HCCI and possesses an elegant model structure that is more amenable to analysis. Based on this model, a recursive algorithm using convex optimization is formulated to generate analytical statements about the boundedness of the in-cylinder thermo-chemical conditions. The bounds generated by the algorithm are also shown to relate well to the data from the experimental testbed.
Book Synopsis Design of a Viable Homogeneous-charge Compression-ignition (HCCI) Engine by : Paul E. Yelvington
Download or read book Design of a Viable Homogeneous-charge Compression-ignition (HCCI) Engine written by Paul E. Yelvington and published by . This book was released on 2004 with total page 261 pages. Available in PDF, EPUB and Kindle. Book excerpt: The homogeneous-charge compression-ignition (HCCI) engine is a novel engine technology with the potential to substantially lower emissions from automotive sources. HCCI engines use lean-premixed combustion to achieve good fuel economy and low emissions of nitrogen-oxides and particulate matter. However, experimentally these engines have demonstrated a viable operating range that is too narrow for vehicular applications. Incomplete combustion or misfire can occur under fuel-lean conditions imposing a minimum load at which the engine can operate. At high loads, HCCI engines are often extremely loud and measured cylinder pressures show strong acoustic oscillations resembling those for a knocking sparkignited engine. The goal of this research was to understand the factors limiting the HCCI range of operability and propose ways of broadening that range. An engine simulation tool was developed to model the combustion process in the engine and predict HCCI knock and incomplete combustion. Predicting HCCI engine knock is particularly important because knock limits the maximum engine torque, and this limitation is a major obstacle to commercialization. A fundamentally-based criterion was developed and shown to give good predictions of the experimental knock limit. Our engine simulation tool was then used to explore the effect of various engine design parameters and operating conditions on the HCCI viable operating range. Performance maps, which show the response of the engine during a normal driving cycle, were constructed to compare these engine designs. The simulations showed that an acceptably broad operating range can be achieved by using a low compression ratio, low octane fuel, and moderate boost pressure. An explanation of why this choice of parameters gives a broad operating window is discussed. Our prediction of the HCCI knock limit is based on the autoignition theory of knock, which asserts that local overpressures in the engine are caused by extremely rapid chemical energy release. A competing theory asserts that knock is caused by the formation of detonation waves initiated at autoignition centers ('hot-spots') in the engine. No conclusive experimental evidence exists for the detonation theory, but many numerical simulations in the literature show that detonation formation is possible; however, some of the assumptions made in these simulations warrant re-examination. In particular, the effect of curvature on small (quasispherical) hot-spots has often been overlooked. We first examined the well-studied case of gasoline spark-ignited engine knock and observed that the size of the hot-spot needed to initiate a detonation is larger than the end-gas region where knock occurs. Subsequent studies of HCCI engine knock predicted that detonations would not form regardless of the hot-spot size because of the low energy content of fuel-lean mixtures typically used in these engines. Our predictions of the HCCI viable operating range were shown to be quite sensitive to details of the ignition chemistry. Therefore, an attempt was made to build an improved chemistry model for HCCI combustion using automatic mechanism-generation software developed in our research group. Extensions to the software were made to allow chemistry model construction for engine conditions. Model predictions for n-heptane/air combustion were compared to literature data from a jet-stirred reactor and rapid-compression machine. We conclude that automatic mechanism generation gives fair predictions without the tuning of rate parameters or other efforts to improve agreement. However, some tuning of the automatically-generated chemistry models is necessary to give the accurate predictions of HCCI combustion needed for our design calculations.
Book Synopsis Evaluation of Technical Feasibility of Homogeneous Charge Compression Ignition (HCCI) Engine Fueled with Hydrogen, Natural Gas, and DME. by :
Download or read book Evaluation of Technical Feasibility of Homogeneous Charge Compression Ignition (HCCI) Engine Fueled with Hydrogen, Natural Gas, and DME. written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of the proposed project was to confirm the feasibility of using blends of hydrogen and natural gas to improve the performance, efficiency, controllability and emissions of a homogeneous charge compression ignition (HCCI) engine. The project team utilized both engine simulation and laboratory testing to evaluate and optimize how blends of hydrogen and natural gas fuel might improve control of HCCI combustion. GTI utilized a state-of-the art single-cylinder engine test platform for the experimental work in the project. The testing was designed to evaluate the feasibility of extending the limits of HCCI engine performance (i.e., stable combustion, high efficiency and low emissions) on natural gas by using blends of natural gas and hydrogen. Early in the project Ricardo provided technical support to GTI as we applied their engine performance simulation program, WAVE, to our HCCI research engine. Modeling support was later provided by Digital Engines, LLC to use their proprietary model to predict peak pressures and temperatures for varying operating parameters included in the Design of Experiments test plan. Digital Engines also provided testing support for the hydrogen and natural gas blends. Prof. David Foster of University of Wisconsin-Madison participated early in the project by providing technical guidance on HCCI engine test plans and modeling requirements. The main purpose of the testing was to quantify the effects of hydrogen addition to natural gas HCCI. Directly comparing straight natural gas with the hydrogen enhanced test points is difficult due to the complexity of HCCI combustion. With the same air flow rate and lambda, the hydrogen enriched fuel mass flow rate is lower than the straight natural gas mass flow rate. However, the energy flow rate is higher for the hydrogen enriched fuel due to hydrogen's significantly greater lower heating value, 120 mJ/kg for hydrogen compared to 45 mJ/kg for natural gas. With these caveats in mind, an analysis of test results indicates that hydrogen enhanced natural gas HCCI (versus neat natural gas HCCI at comparable stoichiometry) had the following characteristics: (1) Substantially lower intake temperature needed for stable HCCI combustion; (2) Inconclusive impact on engine BMEP and power produced; (3) Small reduction in the thermal efficiency of the engine; (4) Moderate reduction in the unburned hydrocarbons in the exhaust; (5) Slight increase in NOx emissions in the exhaust; (6) Slight reduction in CO2 in the exhaust; and (7) Increased knocking at rich stoichiometry. The major accomplishments and findings from the project can be summarized as follows: (1) A model was calibrated for accurately predicting heat release rate and peak pressures for HCCI combustion when operating on hydrogen and natural gas blends. (2) A single cylinder research engine was thoroughly mapped to compare performance and emissions for micro-pilot natural gas compression ignition, and HCCI combustion for neat natural gas versus blends of natural gas and hydrogen. (3) The benefits of using hydrogen to extend, up to a limit, the stable operating window for HCCI combustion of natural gas at higher intake pressures, leaner air to fuel ratios or lower inlet temperatures was documented.
Book Synopsis The Potential of Using Natural Gas in HCCI Engines by : Junnian Zheng
Download or read book The Potential of Using Natural Gas in HCCI Engines written by Junnian Zheng and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: With the depletion of petroleum based fuels and the corresponding concerns of national energy security issues, natural gas as an alternative fuel in IC engine applications has become an attractive option. Natural gas requires minimum mixture preparation, and is chemically stable, both of which make it a suitable fuel for homogeneous charged compression ignition (HCCI) engines. Compared to petroleum based fuels, natural gas produces less green-house emissions. However, natural gas is hard to auto-ignite and therefore requires a higher compression ratio, some amount of intake heating, or some type of pre-ignition. In addition, natural gas usually has large differences in fuel composition from field to field, which adds more uncertainties for engine applications. The current study determines the auto-ignition characteristics, engine performance, and nitric oxides emissions as functions of major operating parameters for a natural gas fueled HCCI engine, and determines differences relative to gasoline fueled HCCI engines which have been studied for many years. These tasks have been done using both zero- and multi-dimensional engine simulations. By zero-dimensional simulation, the effects of varying equivalence ratios, engine speeds, compression ratio, EGR level, intake pressure and fuel compositions are determined and analyzed in detail. To be able to account for the in-cylinder inhomogeneous effect on the HCCI combustion, multi-zone models coupled with cold-flow CFD simulations are employed in addition to the single-zone model. The effects of non-homogeneous temperature and equivalence ratio stratification on the ignition timing, combustion phasing, and emissions formation have been studied and discussed. Finally, the preliminary two-dimensional axial-symmetric CFD simulations have been conducted to study the in-cylinder temperature and the species distributions, which provide better visualization of the natural gas auto-ignition process.
Book Synopsis Analysis of Homogeneous Charge Compression Ignition Engine with Emphasis on Combustion Timing and Reaction Rate by : Arunim Bhattacharya
Download or read book Analysis of Homogeneous Charge Compression Ignition Engine with Emphasis on Combustion Timing and Reaction Rate written by Arunim Bhattacharya and published by . This book was released on 2017 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt: HCCI engines are a class of engines which use high compression ratio to ignite a charge of air-fuel mixture, essentially eliminating the need for spark plugs. This contrasts with diesel engines (although HCCI can be used for diesel engines) where the fuel is injected near the top dead center of the compression stroke regime. Gasoline HCCI engines are of significance because, it attempts to improve the characteristics of the engine for example the thermal efficiency. High compression ratio comes with higher thermal efficiency, yet the peak temperature remains low enough to have low production rates of harmful oxides of nitrogen and formation of soot. However, there are certain challenges associated with such type of engine, one of which and perhaps the most important of all is how to control the combustion rate. Flow dynamics and chemical-kinetics analysis, is essential to predict combustion timing, duration, and rate. The objective of this study is to analyze a HCCI engine using, simulation analysis models including a three-dimensional CFD simulation model. Simulation analysis is carried out using a generic HCCI engine, initially with simplified chemical kinetics, and then using detailed chemical kinetics and using RANS turbulence CFD model. A sensitivity analysis of the effect of RPM on the combustion time, burn duration, heat release, efficiency and emission concentration are carried out.
Book Synopsis Ignition Study in Rapid Compression Machine by : Tairin Hahn
Download or read book Ignition Study in Rapid Compression Machine written by Tairin Hahn and published by . This book was released on 2008 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: As it becomes more and more difficult to find "easy" oil, various alternative fuels are introduced to the markets. These fuels have chemical properties that are different from the traditional gasoline and diesel fuels so that engine efficiency and other engine behaviors may be affected To improve engine efficiency and to identify which alternative fuel is the cleanest fuel solution, it is necessary to compile information about the ignition delay, which governs auto-ignition in spark-ignition (SI), compression-ignition (CI) and homogeneous charge compression-ignition (HCCI) engines. In this study, we measured ignition delay on the Rapid Compression Machine (RCM). RCM is a single-stroke device, which compresses uniform mixtures to engine-like condition. We can interpret from the pressure the detailed heat release process. A comprehensive ignition delay database of toluene/n-heptane mixtures and gasoline/ethanol mixtures was established The data allow us to calculate the auto-ignition behavior in engines. Depending on application the correct choice of alternative fuels may be made.
Book Synopsis Closed-loop Control of a Multicylinder Homogeneous Charge Compression Ignition Engine Using Fast Thermal Management and Ion Sensors by : Parag Mehresh
Download or read book Closed-loop Control of a Multicylinder Homogeneous Charge Compression Ignition Engine Using Fast Thermal Management and Ion Sensors written by Parag Mehresh and published by . This book was released on 2005 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Comparison Study on Combustion Characteristics and Emissions of a Homogeneous Charge Compression Ignition (HCCI) Engine with and Without Pre-combustion Chamber by :
Download or read book Comparison Study on Combustion Characteristics and Emissions of a Homogeneous Charge Compression Ignition (HCCI) Engine with and Without Pre-combustion Chamber written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Thermal Barrier for Homogeneous Charge Compression Ignition Application by : Edward Lawrence Hurley
Download or read book Thermal Barrier for Homogeneous Charge Compression Ignition Application written by Edward Lawrence Hurley and published by . This book was released on 2010 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stringent emissions regulations set forth by the Environmental Protection Agency has forced the automotive industry in the United States to seek a low cost and reliable solution to meet these regulations. Homogeneous Charge Compression Ignition (HCCI) is one of the potential answers to the problem. The HCCI combustion process mates the best features of the two main Internal Combustion Engines (ICE) technologies, Spark Ignition (SI) and Compression Ignition Direct Injected (CIDI). The HCCI combustion process is building on the advantages of each technology while avoiding the disadvantages. One of the main hurdles preventing the successful application of an HCCI engine to the main automotive market is the lack of the precise control over the combustion event. Every successful HCCI research engine found during the literature review employed an external energy source to provide the energy boost necessary for the combustion event. The work contained in this thesis was designed to capture the energy normally wasted by the engine through the engine's exhaust and cooling systems with a Thermal Barrier Coating (TBC). The captured energy was used as the energy boost necessary to cause and control HCCI combustion. This was achieved by modifying a Nissan gasoline engine by increasing the compression ratio from 10.3:1 to 13.5:1 along with coating the cylinder head fire deck, valve heads and crown of the pistons with TBC.
Book Synopsis A Computational Study of the Impact of Mixing on Homogeneous Charge Compression Ignition by : Rahul Jhavar
Download or read book A Computational Study of the Impact of Mixing on Homogeneous Charge Compression Ignition written by Rahul Jhavar and published by . This book was released on 2003 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :Cathy Ka Wai Ng Publisher :Library and Archives Canada = Bibliothèque et Archives Canada ISBN 13 :9780612954977 Total Pages :378 pages Book Rating :4.9/5 (549 download)
Book Synopsis A Computational Study on Ethanol HCCI Combustion [microform] by : Cathy Ka Wai Ng
Download or read book A Computational Study on Ethanol HCCI Combustion [microform] written by Cathy Ka Wai Ng and published by Library and Archives Canada = Bibliothèque et Archives Canada. This book was released on 2004 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: Homogeneous charge compression ignition (HCCI) engines have great potential in high efficiency with ultra-low NOx and particulates emissions. Therefore, fundamentals of HCCI and the control techniques of changing initial temperature, equivalence ratio, exhaust gas recirculation (EGR) rate and fuel reforming rate are examined using a single-zone well-stirred reactor model of an ethanol engine. In particular, the expansion of the Acceptable Operating Range (AOR) using fuel reforming, complemented by EGR, is investigated. It is found that reforming extends the complete combustion limit of the AOR, but shrinks the NOx emission limit. Reforming is also less effective than EGR in widening the AOR at the conditions studied. Therefore, reforming should be used only at temperatures near the ignition limit to enhance combustion. It is recommended that other control techniques, such as using different fuel and additives, and stratified charge combustion should be tested using a more sophisticated multi-zone well-stirred reactor model.
Book Synopsis Effects of Increased Intake Pressure on Homogeneous Charge Compression Ignition (HCCI) of Gasoline and Ethanol in a Four-cylinder Engine by : Robert Vern Mills
Download or read book Effects of Increased Intake Pressure on Homogeneous Charge Compression Ignition (HCCI) of Gasoline and Ethanol in a Four-cylinder Engine written by Robert Vern Mills and published by . This book was released on 2007 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Maximizing Power Output in Homogeneous Charge Compression Ignition (HCCI) Engines and Enabling Effective Control of Combustion Timing by : Samveg Saxena
Download or read book Maximizing Power Output in Homogeneous Charge Compression Ignition (HCCI) Engines and Enabling Effective Control of Combustion Timing written by Samveg Saxena and published by . This book was released on 2011 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: Homogeneous Charge Compression Ignition (HCCI) engines are one of the most promising engine technologies for the future of energy conversion from clean, efficient combustion. HCCI engines allow high efficiency and lower CO2 emission through the use of high compression ratios and the removal of intake throttle valves (like Diesel), and allow very low levels of urban pollutants like nitric oxide and soot (like Otto). These engines, however, are not without their challenges, such as low power density compared with other engine technologies, and a difficulty in controlling combustion timing. This dissertation first addresses the power output limits. The particular strategies for enabling high power output investigated in this dissertation focus on avoiding five critical limits that either damage an engine, drastically reduce efficiency, or drastically increase emissions: 1) ringing limits, 2) peak in-cylinder pressure limits, 3) misfire limits, 4) low intake temperature limits, and 5) excessive emissions limits. The research shows that the key factors that enable high power output, sufficient for passenger vehicles, while simultaneously avoiding the five limits defined above are the use of: 1) high intake air pressures allowing improved power output, 2) highly delayed combustion timing to avoid ringing limits, and 3) using the highest possible equivalence ratio before encountering ringing limits. These results are revealed by conducting extensive experiments spanning a wide range of operating conditions on a multi-cylinder HCCI engine. Second, this dissertation discusses strategies for effectively sensing combustion characteristics on a HCCI engine. For effective feedback control of HCCI combustion timing, a sensor is required to quantify when combustion occurs. Many laboratory engines use in-cylinder pressure sensors but these sensors are currently prohibitively expensive for wide-scale commercialization. Instead, ion sensors made from inexpensive sparkplugs are proposed for sensing combustion timing. Ion sensing, however, is unreliable under certain HCCI conditions. The dissertation presents two strategies for improving the usefulness of ion sensors in HCCI engines: 1) the use of tiny fractions of metal-acetate fuel additives that expand the useful range of ion sensors, and 2) the use of ion sensors for detecting excessive ringing that must be avoided in HCCI engines. These two innovative research efforts make ion sensors viable for sensing combustion characteristics across the full range of HCCI operation, making them effective for use in engine control systems. In summary, this Ph. D dissertation addresses two important technical challenges facing HCCI engines: power output limits, and difficulty in sensing combustion characteristics for control applications. The strategies proposed in this dissertation research bring HCCI engines closer to widespread commercialization allowing vehicles to operate with significantly higher efficiency and with cleaner emissions.
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