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Title: Variable Valve Actuation

Abstract

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 ofmore » 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.« less

Authors:
;
Publication Date:
Research Org.:
Delphi Automotive Systems
Sponsoring Org.:
USDOE
OSTI Identifier:
993477
DOE Contract Number:
FC26-05NT42483
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; 33 ADVANCED PROPULSION SYSTEMS; COMBUSTION; COMPRESSION; DESIGN; DIESEL ENGINES; DISTRIBUTION; ELECTRIC MOTORS; ELEVATORS; ENGINES; FLEXIBILITY; FUEL CONSUMPTION; GASOLINE; IGNITION; IMPLEMENTATION; MANUFACTURERS; MANUFACTURING; OPENINGS; RELIABILITY; TESTING; VALVES

Citation Formats

Jeffrey Gutterman, and A. J. Lasley. Variable Valve Actuation. United States: N. p., 2008. Web. doi:10.2172/993477.
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Jeffrey Gutterman, & A. J. Lasley. Variable Valve Actuation. United States. doi:10.2172/993477.
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Jeffrey Gutterman, and A. J. Lasley. Sun . "Variable Valve Actuation". United States. doi:10.2172/993477. https://www.osti.gov/servlets/purl/993477.
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@article{osti_993477,
title = {Variable Valve Actuation},
author = {Jeffrey Gutterman and A. J. Lasley},
abstractNote = {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.},
doi = {10.2172/993477},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Aug 31 00:00:00 EDT 2008},
month = {Sun Aug 31 00:00:00 EDT 2008}
}
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Technical Report:
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DOI:  10.2172/993477
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  • ; ; ; ...
    This report describes the work completed over a two and one half year effort sponsored by the US Department of Energy. The goal was to demonstrate the technology needed to produce a highly efficient engine enabled by several technologies which were to be developed in the course of the work. The technologies included: (1) A low-pressure direct injection system; (2) A mass air flow sensor which would measure the net airflow into the engine on a per cycle basis; (3) A feedback control system enabled by measuring ionization current signals from the spark plug gap; and (4) An infinitely variablemore » cam actuation system based on a pneumatic-hydraulic valve actuation These developments were supplemented by the use of advanced large eddy simulations as well as evaluations of fuel air mixing using the KIVA and WAVE models. The simulations were accompanied by experimental verification when possible. In this effort a solid base has been established for continued development of the advanced engine concepts originally proposed. Due to problems with the valve actuation system a complete demonstration of the engine concept originally proposed was not possible. Some of the highlights that were accomplished during this effort are: (1) A forward-backward mass air flow sensor has been developed and a patent application for the device has been submitted. We are optimistic that this technology will have a particular application in variable valve timing direct injection systems for IC engines. (2) The biggest effort on this project has involved the development of the pneumatic-hydraulic valve actuation system. This system was originally purchased from Cargine, a Swedish supplier and is in the development stage. To date we have not been able to use the actuators to control the exhaust valves, although the actuators have been successfully employed to control the intake valves. The reason for this is the additional complication associated with variable back pressure on the exhaust valves when they are opened. As a result of this effort, we have devised a new design and have filed for a patent on a method of control which is believed to overcome this problem. The engine we have been working with originally had a single camshaft which controlled both the intake and exhaust valves. Single cycle lift and timing control was demonstrated with this system. (3) Large eddy simulations and KIVA based simulations were used in conjunction with flow visualizations in an optical engine to study fuel air mixing. During this effort we have devised a metric for quantifying fuel distribution and it is described in several of our papers. (4) A control system has been developed to enable us to test the benefits of the various technologies. This system used is based on Opal-RT hardware and is being used in a current DOE sponsored program.« less

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    This project studied the results of previous research on the potential effects of variable valve timing for improving automotive engine fuel economy. Methods of implementation of valve timing control and their practicality were also assessed. Some of the sources claim fuel economy improvements as high as 18 to 20% but conclusions suffer from insufficient test data as well as a recording of major variables. Other deficiencies include insufficient attention to effects on driveability; lack of standard reference for data comparisons; and little consideration toward manufacturing feasibility. It is concluded that savings of 5 to 10% over the normal drive cyclemore » are probably realizable providing emphasis is directed towards optimizing valve timing schedules at low speeds under low loads as opposed to the current practice of wide open throttle. Methods of implementation as reported from research programs and patent disclosures were also evaluated, categorized and assessed for manufacturing practicability.« less

  • ; ;
    In recent years, new mechanical inventions and electronic engine controls have made variable valve timing a production possibility. A few manufacturers have VVT systems in production. The report presents a paper study of the fuel economy benefits and the incremental manufacturing costs, tooling costs and engine weights as well as production leadtime for a VVT engine. Emission levels are considered. As a base, a 4-valve, V-6 engine of 3.5 liters was used with a 3750 lb. passenger vehicle. The VVT system applied to that engine was a combination of the Atsugi cam phasing system, a modified Mitsubishi MIVEC long andmore » short duration cam system and intake port throttle. The final VVT engine was presumed to have reduced idle speed (500 vs 640 rpm base) and an 8% lower displacement (3.22 liters).« less

  • The results of the summary report and the attached contractor study suggest that the incorporation of variable valve timing features into a modern V-6 engine will be fairly costly to the vehicle buyer. However, fuel economy gains will likely be significant over the life of the vehicle. The scope of the project did not include any estimates of the long term benefits that would accrue to vehicle owners through energy conservation. Most important, the cost and weight contained herein is based on a theoretical engine design for which the dimensions are approximate. Hence, the estimates provided below and throughout thismore » report are preliminary only. The $392 retail price increase shown below represents a composite for Chrysler, Ford, and General Motors. The variable valve timing features selected for inclusion in the study are: variable camshaft phasing, long and short event follower cams, and divided air intake runners with a port throttle in one runner. Oil system and variable valve timing system controls plus miscellaneous wiring, clips, painting, plating and assembly labor complete the changes required to incorporate the variable valve timing system into the selected engine design. Estimated retail price and weight increases associated with these changes are presented.« less