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Author: Chris Dollimore
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Chris Dollimore
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Many approaches exist to enable advanced mode, low temperature combustion systems for diesel engines - such as premixed charge compression ignition (PCCI), Homogeneous Charge Compression Ignition (HCCI) or other HCCI-like combustion modes. The fuel properties and the quantity, distribution and temperature profile of air, fuel and residual fraction in the cylinder can have a marked effect on the heat release rate and combustion phasing. Figure 1 shows that a systems approach is required for HCCI-like combustion. While the exact requirements remain unclear (and will vary depending on fuel, engine size and application), some form of substantially variable valve actuation is a likely element in such a system. Variable valve actuation, for both intake and exhaust valve events, is a potent tool for controlling the parameters that are critical to HCCI-like combustion and expanding its operational range. Additionally, VVA can be used to optimize the combustion process as well as exhaust temperatures and impact the after treatment system requirements and its associated cost. Delphi Corporation has major manufacturing and product development and applied R & D expertise in the valve train area. Historical R & D experience includes the development of fully variable electro-hydraulic valve train on research engines as well as several generations of mechanical VVA for gasoline systems. This experience has enabled us to evaluate various implementations and determine the strengths and weaknesses of each. While a fully variable electro-hydraulic valve train system might be the 'ideal' solution technically for maximum flexibility in the timing and control of the valve events, its complexity, associated costs, and high power consumption make its implementation on low cost high volume applications unlikely. Conversely, a simple mechanical system might be a low cost solution but not deliver the flexibility required for HCCI operation. After modeling more than 200 variations of the mechanism it was determined that the single cam design did not have enough flexibility to satisfy three critical OEM requirements simultaneously, (maximum valve lift variation, intake valve opening timing and valve closing duration), and a new approach would be necessary. After numerous internal design reviews including several with the OEM a dual cam design was developed that had the flexibility to meet all motion requirements. The second cam added complexity to the mechanism however the cost was offset by the deletion of the electric motor required in the previous design. New patent applications including detailed drawings and potential valve motion profiles were generated and alternate two cam designs were proposed and evaluated for function, cost, reliability and durability. Hardware was designed and built and testing of sample hardware was successfully completed on an engine test stand. The mechanism developed during the course of this investigation can be applied by Original Equipment Manufacturers, (OEM), to their advanced diesel engines with the ultimate goal of reducing emissions and improving fuel economy. The objectives are: (1) Develop an optimal, cost effective, variable valve actuation (VVA) system for advanced low temperature diesel combustion processes. (2) Design and model alternative mechanical approaches and down-select for optimum design. (3) Build and demonstrate a mechanism capable of application on running engines.
Author: Mitchell Terpstra
Publisher:
ISBN:
Category : Automobiles
Languages : en
Pages : 116
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Conventional engines with camshafts with fixed timings force a compromise between performance at high engine loads and fuel economy at low engine loads. Adjusting internal combustion engine valve timing and lift through a variable valve actuation (VVA) system is an established method of improving engine performance [1]. A fully flexible hydraulic variable valve actuation (HVVA) system in development at the University of Waterloo allows the valve timing to be optimized for any engine operating condition. This project is a further development of this HVVA system. First, the previous prototype was thoroughly tested and evaluated. Major design issues and challenges were addressed, and changes were incorporated into a new prototype design. This prototype was designed to be robust and more compact than the previous system. A completely new concept was developed for the phasing system used to adjust the valve timings. The new HVVA design was manufactured, assembled, and installed on a single cylinder test engine. Initial experiments of the new HVVA system validated its ability to change engine valve timing and match the profiles of different VVA strategies. The system was able to switch between different profiles in
Author: Mohammad Pournazeri
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The automotive industry has been in a marathon of advancement over the past decades. This is partly due to global environmental concerns about increasing amount of air pollutants such as NOx (oxides of nitrogen), CO (carbon monoxide) and particulate matters (PM) and decreasing fossil fuel resources. Recently due to stringent emission regulations such as US EPA (Environmental Protection Agency) and CARB (California Air Resource Board), improvement in fuel economy and reduction in the exhaust gas emissions have become the two major challenges for engine manufacturers. To fulfill the requirements of these regulations, the IC engines including gasoline and diesel engines have experienced significant modifications during the past decades. Incorporating the fully flexible valvetrains in production IC engines is one of the several ways to improve the performance of these engines. The ultimate goal of this PhD thesis is to conduct feasibility study on development of a reliable fully flexible hydraulic valvetrain for automotive engines. Camless valvetrains such as electro-hydraulic, electro-mechanical and electro-pneumatic valve actuators have been developed and extensively studied by several engine component manufacturers and researchers. Unlike conventional camshaft driven systems and cam-based variable valve timing (VVT) techniques, these systems offer valve timings and lift control that are fully independent of crankshaft position and engine speed. These systems are key technical enablers for HCCI, 2/4 stroke-switching gasoline and air hybrid technologies, each of which is a high fuel efficiency technology. Although the flexibility of the camless valvetrains is limitless, they are generally more complex and expensive than cam-based systems and require more study on areas of reliability, fail safety, durability, repeatability and robustness. On the contrary, the cam-based variable valve timing systems are more reliable, durable, repeatable and robust but much less flexible and much more complex in design. In this research work, a new hydraulic variable valve actuation system (VVA) is proposed, designed, prototyped and tested. The proposed system consists of a two rotary spool valves each of which actuated either by a combination of engine crankshaft and a phase shifter or by a variable speed servo-motor. The proposed actuation system offers the same level of flexibility as camless valvetrains while its reliability, repeatability and robustness are comparable with cam driven systems. In this system, the engine valve opening and closing events can be advanced or retarded without any constraint as well as the final valve lift. Transition from regenerative braking or air motor mode to conventional mode in air hybrid engines can be easily realized using the proposed valvetrain. The proposed VVA system, as a stand-alone unit, is modeled, designed, prototyped and successfully tested. The mathematical model of the system is verified by the experimental data and used as a numerical test bench for evaluating the performance of the designed control systems. The system test setup is equipped with valve timing and lift controllers and it is tested to measure repeatability, flexibility and control precision of the valve actuation system. For fast and accurate engine valve lift control, a simplified dynamic model of the system (average model) is derived based on the energy and mass conservation principles. A discrete time sliding mode controller is designed based on the system average model and it is implemented and tested on the experimental setup. To improve the energy efficiency and robustness of the proposed valve actuator, the system design parameters are subjected to an optimization using the genetic algorithm method. Finally, an energy recovery system is proposed, designed and tested to reduce the hydraulic valvetrain power consumption. The presented study is only a small portion of the growing research in this area, and it is hoped that the results obtained here will lead to the realization of a more reliable, repeatable, and flexible engine valve system.
Author: William E. Tourdot
Publisher:
ISBN:
Category :
Languages : en
Pages : 334
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Author: Ahmad M. Sabri
Publisher:
ISBN:
Category :
Languages : en
Pages : 486
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Author: Mohammad Sharif Siddiqui
Publisher:
ISBN:
Category : Automobiles
Languages : en
Pages : 102
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The combustion characteristics in an engine cylinder can greatly change over a range of speeds and loads. However, conventional engines x the timing and amount of intake and exhaust, which can lead to higher emissions, wasted fuel, and lower power output. This thesis studies the application of a hydraulics based variable valve actuation system to change the valves' lift and timing on a single cylinder spark ignition engine. In addition to controlling the valve actuation, a hydraulics based design has the advantage of protecting against engine failure in cases of electrical power loss, reverting the system to behave as a conventional camshaft valve train. The research extends the previous iterations of the hydraulics design to prevent leakage, retain pressure, and reliably open and close the engine valves. A hydraulic cylinder is used to replace the conventional cam where pressurized fluid opens, and spring force closes, the engine valve. The pressurized fluid is supplied to, or removed from, the cylinder using rotary spool valves coupled to the engine crankshaft. Additionally, the system is modelled in Simulink to determine the effect of system pressure, flow area, and spring rate on the resulting valve pro file. After modelling the system's performance for achieving variable lift and timing, the system was designed, manufactured, and tested on a single cylinder engine with the aid of a dynamometer. Experimental results for valve lift showed good agreement with the simulation models. Majority of the tests were performed using manual control, followed by experiments with active control of the system pressure to reach a desired valve lift. The lift controller is able to achieve the desired valve actuation in under 2 seconds with active pressure feedback. Lastly, the ability of the hydraulic variable valve system as a viable alternative is shown by achieving combustion at 1500 RPM engine idle speed.
Author: Doug Woodyard
Publisher: Butterworth-Heinemann
ISBN: 0080943616
Category : Technology & Engineering
Languages : en
Pages : 925
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Since its first appearance in 1950, Pounder's Marine Diesel Engines has served seagoing engineers, students of the Certificates of Competency examinations and the marine engineering industry throughout the world. Each new edition has noted the changes in engine design and the influence of new technology and economic needs on the marine diesel engine. Now in its ninth edition, Pounder's retains the directness of approach and attention to essential detail that characterized its predecessors. There are new chapters on monitoring control and HiMSEN engines as well as information on developments in electronic-controlled fuel injection. It is fully updated to cover new legislation including that on emissions and provides details on enhancing overall efficiency and cutting CO2 emissions. After experience as a seagoing engineer with the British India Steam Navigation Company, Doug Woodyard held editorial positions with the Institution of Mechanical Engineers and the Institute of Marine Engineers. He subsequently edited The Motor Ship journal for eight years before becoming a freelance editor specializing in shipping, shipbuilding and marine engineering. He is currently technical editor of Marine Propulsion and Auxiliary Machinery, a contributing editor to Speed at Sea, Shipping World and Shipbuilder and a technical press consultant to Rolls-Royce Commercial Marine. - Helps engineers to understand the latest changes to marine diesel engineers - Careful organisation of the new edition enables readers to access the information they require - Brand new chapters focus on monitoring control systems and HiMSEN engines - Over 270 high quality, clearly labelled illustrations and figures to aid understanding and help engineers quickly identify what they need to know
Author: Gus Wright
Publisher: Jones & Bartlett Learning
ISBN: 1284150917
Category : Transportation
Languages : en
Pages : 1895
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"Fundamentals of Medium/Heavy Duty Diesel Engines, Second Edition offers comprehensive coverage of every ASE task with clarity and precision in a concise format that ensures student comprehension and encourages critical thinking. This edition describes safe and effective diagnostic, repair, and maintenance procedures for today's medium and heavy vehicle diesel engines"--
Author: Society of Automotive Engineers
Publisher:
ISBN: 9781560913412
Category : Technology & Engineering
Languages : en
Pages : 93
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