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Author: Mohammad Sharif Siddiqui
Publisher:
ISBN:
Category : Automobiles
Languages : en
Pages : 102
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Book Description
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: Mohammad Sharif Siddiqui
Publisher:
ISBN:
Category : Automobiles
Languages : en
Pages : 102
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Book Description
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: Mitchell Terpstra
Publisher:
ISBN:
Category : Automobiles
Languages : en
Pages : 116
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Book Description
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: National Research Council
Publisher: National Academies Press
ISBN: 0309373913
Category : Science
Languages : en
Pages : 812
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Book Description
The light-duty vehicle fleet is expected to undergo substantial technological changes over the next several decades. New powertrain designs, alternative fuels, advanced materials and significant changes to the vehicle body are being driven by increasingly stringent fuel economy and greenhouse gas emission standards. By the end of the next decade, cars and light-duty trucks will be more fuel efficient, weigh less, emit less air pollutants, have more safety features, and will be more expensive to purchase relative to current vehicles. Though the gasoline-powered spark ignition engine will continue to be the dominant powertrain configuration even through 2030, such vehicles will be equipped with advanced technologies, materials, electronics and controls, and aerodynamics. And by 2030, the deployment of alternative methods to propel and fuel vehicles and alternative modes of transportation, including autonomous vehicles, will be well underway. What are these new technologies - how will they work, and will some technologies be more effective than others? Written to inform The United States Department of Transportation's National Highway Traffic Safety Administration (NHTSA) and Environmental Protection Agency (EPA) Corporate Average Fuel Economy (CAFE) and greenhouse gas (GHG) emission standards, this new report from the National Research Council is a technical evaluation of costs, benefits, and implementation issues of fuel reduction technologies for next-generation light-duty vehicles. Cost, Effectiveness, and Deployment of Fuel Economy Technologies for Light-Duty Vehicles estimates the cost, potential efficiency improvements, and barriers to commercial deployment of technologies that might be employed from 2020 to 2030. This report describes these promising technologies and makes recommendations for their inclusion on the list of technologies applicable for the 2017-2025 CAFE standards.
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: 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: Chris Dollimore
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Leroy Thomas
Publisher: Omniscriptum
ISBN: 9786131545207
Category :
Languages : en
Pages : 172
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Book Description
The production of torque and pollutants of Variable Valve Actuation equipped internal combustion engines found in the automotive industry (both Diesel and gasoline engines) is studied. Variable Valve Actuation (VVA) is a technology which has been introduced to optimize engine efficiency at steady-states covering a wide range of operating conditions. In more details, the outcome of the internal combustion engine (torque and pollutant) depends on the cylinder filling at each stroke which, itself, depends on the VVA positions and the engine intake manifold conditions. These two subsystems have inconsistent response times which results in efficiency losses during transient operations. In this manuscript, a remedy for this issue which takes the form of coordination loops of low-level controllers is proposed. This coordination uses a cylinder filling model, designed in the thesis. Experimental results prove that torque production and pollutant emissions can be improved.
Author: Yangtao Li
Publisher:
ISBN:
Category : Automobiles
Languages : en
Pages : 121
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Book Description
Variety of technologies along with the mechanisms for their implementations have been developed in order to pursue possible improvements in the performance and efficiency of gasoline engines. Yet, most of the commonly used techniques, such as the cam-based variable valve timings (VVT) and variable compression ratio (VCR), are realized by different kinds of complicated mechanisms, providing an extended but still relatively limited adjustability, for attaining improved valve timings and different engine cycles according to the varying working conditions of the engine. The hydraulic variable valve actuation (HVVA) system, however, can provide greater freedoms to the engine valve motions than most of the traditional cam-based valve train systems do. By considering the characteristics of the HVVA system, the strategies of putting its outstanding flexibilities into use for further improving the performances of gasoline engines with respect to power and fuel economy are developed in this research. By utilizing the flexibility offered by the HVVA system, a set of new valve motion strategies is developed for realizing an unthrottled engine load control. In this research, the late exhaust valve closure (LEVC) and early intake valve closure (EIVC) strategies are adopted at the same time for granting the engine an internal exhaust gas recirculation (IEGR) feature and together evolved into a tunable IEGR scheme for fulfilling the partial engine loads without throttling. Alternatively, the realization to the proposed variable Atkinson cycle (VAC), which is realized by late intake valve closures (LIVCs), can also achieve the same goal of unthrottled engine load control for partial load operations. Moreover, an HVVA engine model is proposed and built in GT-suite, which is able to capture the interdependencies of the HVVA system and the engine operations, and is as well carefully calibrated by experimental data acquired from individual bench tests of the HVVA system and the baseline engine. The HVVA engine in this research is a converted from a baseline single-cylinder engine and is able to carry out a variable Otto cycle (VOC) at full engine load operations for achieving higher power performance while realizing a variable Atkinson cycle (VAC) or a tunable IEGR feature at partial engine load operations for gaining better fuel economy without having any further modifications or attaching additional components to the engine. In addition, a set of genetic algorithm (GA)-based optimization schemes is also developed for identifying the proper operating parameters of the HVVA engine when adopting any of the proposed engine operation schemes. A MATLAB-Simulink and GT-Suite coupling simulation structure is proposed for carrying out the GA approaches. Furthermore, these GA optimizers are designed to be capable of maintaining their proper functionality while non-linear constraints are taken into considerations. By running the HVVA engine with the optimized operating parameters identified by the proposed GA optimizations, noticeable improvements on the engine outputs at full load operations and fuel economy at partial load operations are revealed. Benefited from the features of the HVVA system, the tunings of the HVVA engine can be flexibly customized to fulfill any requirements towards different desired engine characteristics. At last, with the corresponding operating parameters be optimized by the proposed GA optimization techniques, all the proposed HVVA valve motion strategies are carried out by an actual prototype HVVA engine and are qualitatively validated by experiments. The experimental results are showing expected outcomes on the improvements to the engine's power and fuel economy performances under corresponding operations. A power improvement of 12.3% is noticed from the experiments by running the HVVA engine in the proposed VOC operation at the exemplary 1000rpm engine speed. In addition, comparing to the throttled operation of the baseline engine, the experiment studies show also the HVVA engine is able to run with leaner air-fuel mixtures to achieve the same desired partial engine load operations by adopting the IEGR scheme or the VAC operation. With an adopted air-fuel ratio (AFR) of 16.1 for the IEGR scheme and 16.3 for the VAC scheme, the engine could realize the same exemplary speed-load operation of 1000rpm/5.2Nm, while the baseline engine with throttling load control requires an AFR of 14.7 to achieve the same partial load operation.
Author:
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Category :
Languages : en
Pages :
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An engine has a cylinder head having a first surface and a second surface spaced from the first surface. A valve is moveably connected to the cylinder head. A rocker arm is connected to the valve, and a rocker shaft having a first location spaced a maximum distance from the cylinder head is connected to the rocker arm. A support member has and an actuator fluid passage network. The actuator fluid passage network defines a volume. The support member is connected to the cylinder head and is positioned such that a majority of the volume of the actuator fluid passage network is between the first location of the rocker shaft and the second surface of the cylinder head.
