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Author: Samveg Saxena Publisher: ISBN: Category : Languages : en Pages : 238
Book Description
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.
Author: Samveg Saxena Publisher: ISBN: Category : Languages : en Pages : 238
Book Description
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.
Author: Hsien-Hsin Liao Publisher: Stanford University ISBN: Category : Languages : en Pages : 201
Book Description
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.
Author: H Zhao Publisher: Elsevier ISBN: 184569354X Category : Technology & Engineering Languages : en Pages : 557
Book Description
Homogeneous charge compression ignition (HCCI)/controlled auto-ignition (CAI) has emerged as one of the most promising engine technologies with the potential to combine fuel efficiency and improved emissions performance, offering reduced nitrous oxides and particulate matter alongside efficiency comparable with modern diesel engines. Despite the considerable advantages, its operational range is rather limited and controlling the combustion (timing of ignition and rate of energy release) is still an area of on-going research. Commercial applications are, however, close to reality.HCCI and CAI engines for the automotive industry presents the state-of-the-art in research and development on an international basis, as a one-stop reference work. The background to the development of HCCI / CAI engine technology is described. Basic principles, the technologies and their potential applications, strengths and weaknesses, as well as likely future trends and sources of further information are reviewed in the areas of gasoline HCCI / CAI engines; diesel HCCI engines; HCCI / CAI engines with alternative fuels; and advanced modelling and experimental techniques. The book provides an invaluable source of information for scientific researchers, R&D engineers and managers in the automotive engineering industry worldwide. Presents the state-of-the-art in research and development on an international basis An invaluable source of information for scientific researchers, R&D engineers and managers in the automotive engineering industry worldwide Looks at one of the most promising engine technologies around
Author: Samveg Saxena
Author: Samveg Saxena
Author: Hsien-Hsin Liao
Author: 
Author: Michael Y. Au
Author: Tanet Aroonsrisopon
Author: Robert Vern Mills
Author: William Lee Gans
Author: Jacob Richard Zuehl
Author: Craig David Marriott
Author: H Zhao