15 research outputs found
An indirectly controlled high-speed servo valve using piezo actuators
Since the exhaust emissions legislation for motor vehicles with combustion engines is complicating the manufacturing of environmental yet powerful engines more than ever, automobile manufacturers have approached this challenge by means of downsizing, hybridization of combustion and electric engines and variable valve opening times. In these cases conventional, mechanical valve trains are still used. The subject of this master thesis is the development of a mechatronic control unit as replacement for the camshaft driven valve train of common combustion engines. The system’s aim is a contribution to the progression of the development of modern combustion engines satisfying current demands in terms of economy and efficiency. The developed system is based on the “Full Variable Valve Train” project, founded at the “Institute of Vehicle Construction Wolfsburg” at the “Ostfalia University of Applied Sciences”. An indirectly controlled high speed servo valve that is actuated by a piezoelectric actuator and pressurized hydraulic fluid is being developed. The overall aim is to obtain advantages from a control engineering perspective, being able to reduce the size of the used piezo actuator and hence solve the packaging and regulation issues of the overall system. After manufacturing and improvement activities, a system could be developed that allows a variable control of the engine valve movement. The best results are achieved using a rectangular function for the engine valve actuator. The system allows engine valve operation independent from the crankshaft position and shows the potential to generate higher engine torque and power output while decreasing fuel consumption and emissions at the same time
An indirectly controlled high-speed servo valve using piezo actuators
Since the exhaust emissions legislation for motor vehicles with combustion engines is complicating the manufacturing of environmental yet powerful engines more than ever, automobile manufacturers have approached this challenge by means of downsizing, hybridization of combustion and electric engines and variable valve opening times. In these cases conventional, mechanical valve trains are still used. The subject of this master thesis is the development of a mechatronic control unit as replacement for the camshaft driven valve train of common combustion engines. The system’s aim is a contribution to the progression of the development of modern combustion engines satisfying current demands in terms of economy and efficiency. The developed system is based on the “Full Variable Valve Train” project, founded at the “Institute of Vehicle Construction Wolfsburg” at the “Ostfalia University of Applied Sciences”. An indirectly controlled high speed servo valve that is actuated by a piezoelectric actuator and pressurized hydraulic fluid is being developed. The overall aim is to obtain advantages from a control engineering perspective, being able to reduce the size of the used piezo actuator and hence solve the packaging and regulation issues of the overall system. After manufacturing and improvement activities, a system could be developed that allows a variable control of the engine valve movement. The best results are achieved using a rectangular function for the engine valve actuator. The system allows engine valve operation independent from the crankshaft position and shows the potential to generate higher engine torque and power output while decreasing fuel consumption and emissions at the same time
Development of a New Fully Flexible Hydraulic Variable Valve Actuation System
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
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Computational and experimental study of air hybrid engine concepts
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityThe air hybrid engine absorbs the vehicle kinetic energy during braking, stores it in an air tank in the form of compressed air, and reuses it to start the engine and to propel a vehicle during cruising and acceleration. Capturing, storing and reusing this braking energy to achieve stop-start operation and to give additional power can therefore improve fuel economy, particularly in cities and urban areas where the traffic conditions involve many stops and starts. In order to reuse the residual kinetic energy, the vehicle operation consists of 3 basic modes, i.e. Compression Mode (CM), Expander Mode (EM) and normal firing mode, as well as stop-start operation through an air starter. A four-cylinder 2 litre diesel engine has been modelled to operate in four air hybrid engine configurations so that the braking and motoring performance of each configuration could be studied. These air hybrid systems can be constructed with production technologies and incur minimum changes to the existing engine design. The regenerative engine braking and starting capability is realised through the employment of an innovative simple one-way intake system and a production cam profile switching (CPS) mechanism. The hybrid systems will allow the engine to be cranked by the compressed air at moderate pressure without using addition starters or dedicated valves in the cylinder head. Therefore, the
proposed air hybrid engine systems can be considered as a cost-effective regenerative hybrid powertrain and can be implemented in vehicles using existing production technologies. A novel cost-effective pneumatic regenerative stop-start hybrid system, Regenerative Engine Braking Device (RegenEBD), for buses and commercial vehicles is presented. RegenEBD is capable of converting kinetic energy into pneumatic energy in the compressed air saved in an air tank using a production engine braking device and other production type automotive components and a proprietary intake system design. The compressed air is then used to drive an air starter to achieve regenerative stop-start operations. The proposed hybrid system can work with the existing vehicle transmission system and can be implemented with the retro-fitted valve actuation device and a sandwich block mounted between the cylinder head and the production intake manifold. Compression mode operation is achieved by keeping the intake valves from fully closed throughout the four-strokes through a production type variable valve exhaust brake (VVEB) device on the intake valves. As a result, the induced air could be compressed through the opening gap of intake valves into the air tank through the intake system of proprietary design. The compressed air can then be used to crank the engine directly through the air expander operation or indirectly through the action of an air starter in production. A single cylinder camless engine has been set up and operated to evaluate the compression mode performance of two air hybrid concepts. The experimental results are then compared with the computational output with excellent agreement. In order to evaluate the potential of the air hybrid engine technologies, a new vehicle driving cycle simulation program has been developed using Matlab Simulink. An air hybrid engine sub-model and methodology for modelling the air hybrid engine’s performance have been proposed and implemented in the vehicle driving cycle simulation. The NEDC analysis of a Ford Mondeo vehicle shows that the vehicle can achieve regenerative stop-start operations throughout the driving cycle when it is powered by a 2.0litre diesel engine with air hybrid operation using a 40litre air tank of less than 10bar pressure. The regenerative stop-start operation can lead to 4.5% fuel saving during the NEDC. Finally, the Millbrook London Transport Bus (MLTB) driving cycle has been used to analyse the effectiveness of RegenEBD on a double deck bus powered by a Yuchai diesel engine. The results show that 90% stop-starts during the MLTB can be accomplished by RegenEBD and that a significant fuel saving of 6.5% can be obtained from the regenerative stop-start operations
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Experimental investigation of CAI combustion in a two-stroke poppet valve DI engine
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonDue to their ability to simultaneously reduce fuel consumption and NOx emissions, Controlled Auto Ignition (CAI) and HCCI combustion processes have been extensively researched over the last decade and adopted on prototype gasoline engines. These combustion processes were initially achieved on conventional two-stroke ported gasoline engines, but there have been significantly fewer studies carried out on the CAI combustion in two-stroke engines. This is primarily due to the inherent problems associated with conventional two-stroke engine intake and exhaust ports. Meanwhile, engine downsizing has been actively researched and developed as an effective means to improve the vehicle’s fuel economy. This is achieved by operating the engine at higher load regions of lower fuel consumption and by reducing the number of cylinders. However, aggressive downsizing of the current 4-stroke gasoline engine is limited by the knocking combustion and high peak cylinder pressure. As an alternative approach to engine downsizing, boosted two-stroke operation is being researched. In this thesis, it has been shown that the CAI combustion in the two-stroke cycle could be readily achieved at part-load conditions with significant reductions in CO and uHC emissions when compared to typical SI combustion in a single cylinder gasoline direct injection camless engine. In addition, extensive engine experiments have been performed to determine the optimum boosting for minimum fuel consumption during the two-stroke operation. In order to minimise the air short-circuiting rate, the intake and exhaust valve timings were varied and optimised. It is shown that the lean operation under boosted condition can extend the range of CAI combustion and increase combustion and thermal efficiencies as well as producing much lower CO and HC emissions. By means of the cycle-resolved in-cylinder measurements and heat release analysis, the improvement in combustion and thermal efficiencies were attributed to the improved in-cylinder mixture, optimised autoignition, and combustion phases. Finally, in view of the increased use of ethanol in gasoline engines, E15 and E85 were used and their effect on engine performance, fuel economy and exhaust emissions were investigated
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Experimental studies of performance and emissions in a 2/4-stroke engine
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityDirect Injection (DI) gasoline engines are staging a come-back because of its potential for
improved fuel economy through principally the engine down-sizing by boosting, stratified
charge combustion and Controlled Auto Ignition (CAI) at part load operations. The problem
with the Spark Ignition (SI) engine is its inherent low part-load efficiency. This arises due to
the pumping loses that occur when the throttle closes or partially opens. One way of
decreasing the pumping losses is to operate the engine lean or by adding residual gases. It is
not possible to operate the engine unthrottled with a very lean or diluted mixture at low loads
due to misfire. However, the load can also be controlled by changing the valve timing. This
reduce the pumping loses and hence increase the efficiency. Due to the limited time available for complete fuel evaporation and the mixing of fuel and air mixture, locally fuel rich mixture or even liquid fuel can be present during the combustion process. This causes a significant increase in Particulate Matter (PM) emissions from direct injection gasoline engines compared to the conventional port fuel injection gasoline engines, which are of major concern because of its health implications. In the meantime, depleting reserves of fossil fuels and the increasing environmental pollution caused by burning of fossil fuels, have paved the way for fuel diversification. Cleaner and renewable fuel is being introduced worldwide. The use of ethanol as an alternative transportation fuel shows promise for several reasons. While ethanol can be produced from
several types of biomass, it offers properties such as high octane number, higher oxygen content and high heat of evaporation, which make it a most attractive alternative fuel, in particular for the direct injection gasoline engine. In this research, a single cylinder camless engine equipped with an electro-hydraulic valve
train system has been used to study and compare different engine operation modes in the SI and CAI combustion. The fuel consumption, gaseous and particulate emissions of gasoline
and its mixture with ethanol (E15 and E85) were measured and analysed at the same engine
operating condition. The heat release analysis and performance characteristics of CAI and SI
combustion were carried out by the in-cylinder pressure measurement. The effect of load and
valve timings on the gaseous and Particulate Matter (PM) emissions was investigated for both
4-stroke SI and CAI combustion. Within the achieved CAI operational ranges, particle
emissions were found to be dominated by smaller particles (<50nm). Hotter charge and better
mixing are the main parameters affecting the soot particles in the exhaust irrespective of the
combustion modes and valve timings. At part-load conditions investigated, it was found that the CAI combustion produced the lowest NOx emissions of 0.4g/KWh in all fuel blends and lower fuel consumption 223g/KWh with improved combustion efficiency of 94.7% in ethanol fuel E15 and E85. The positive
valve overlap was found to produce lowest fuel consumption of 222.8 g/KWh in all fuel blend
and respond better to ethanol fuel in E15 and E85 with improved indicated efficiency of 40.5% compared to the other modes investigated. The early intake valve throttled SI operation led to a moderate improvement in the fuel consumption of 243.5g/KWh over the throttled SI operation but it was characterised by the slowest combustion and highest CO (33.5g/KWh) and HC (16.8g/KWh) emissions . Less and smaller particles numbers were detected for Early Intake Valve Closure (EIVC) from the combustion of E0 and E15 (4.0E+07#/cm3 less than 50nm in diameter) fuel blends. The particulate emission results showed that soot was the dominant particles in the exhaust, which could be reduced by leaner mixture combustion
.Tertiary Education Trust Fund and University of Portharcourt
Nigeri
Volume 3 – Conference
We are pleased to present the conference proceedings for the 12th edition of the International Fluid Power Conference (IFK). The IFK is one of the world’s most significant scientific conferences on fluid power control technology and systems. It offers a common platform for the presentation and discussion of trends and innovations to manufacturers, users and scientists. The Chair of Fluid-Mechatronic Systems at the TU Dresden is organizing and hosting the IFK for the sixth time. Supporting hosts are the Fluid Power Association of the German Engineering Federation (VDMA), Dresdner Verein zur Förderung der Fluidtechnik e. V. (DVF) and GWT-TUD GmbH. The organization and the conference location alternates every two years between the Chair of Fluid-Mechatronic Systems in Dresden and the Institute for Fluid Power Drives and Systems in Aachen. The symposium on the first day is dedicated to presentations focused on methodology and fundamental research. The two following conference days offer a wide variety of application and technology orientated papers about the latest state of the art in fluid power. It is this combination that makes the IFK a unique and excellent forum for the exchange of academic research and industrial application experience. A simultaneously ongoing exhibition offers the possibility to get product information and to have individual talks with manufacturers. The theme of the 12th IFK is “Fluid Power – Future Technology”, covering topics that enable the development of 5G-ready, cost-efficient and demand-driven structures, as well as individual decentralized drives. Another topic is the real-time data exchange that allows the application of numerous predictive maintenance strategies, which will significantly increase the availability of fluid power systems and their elements and ensure their improved lifetime performance. We create an atmosphere for casual exchange by offering a vast frame and cultural program. This includes a get-together, a conference banquet, laboratory festivities and some physical activities such as jogging in Dresden’s old town.:Group 8: Pneumatics
Group 9 | 11: Mobile applications
Group 10: Special domains
Group 12: Novel system architectures
Group 13 | 15: Actuators & sensors
Group 14: Safety & reliabilit
Implementation of a fully variable valve actuation valvetrain
In January 2008 the Sasol (Pty) Ltd Advisory Board identified that the Sasol Advanced Fuels Laboratory's (SAFL) single cylinder research engine was not in line with the current engine technologies, in particular Fully Variable Valve Actuation (FVVA). This project represented the first stage of the engine upgrade, which was to modify the current single cylinder engine to interface with pneumatic valve actuators and a fully configurable Engine Control Unit (ECU)
Optimized state feedback regulation of 3DOF helicopter system via extremum seeking
In this paper, an optimized state feedback regulation of a 3 degree of freedom (DOF) helicopter is designed via extremum seeking (ES) technique. Multi-parameter ES is applied to optimize the tracking performance via tuning State Vector Feedback with Integration of the Control Error (SVFBICE).
Discrete multivariable version of ES is developed to minimize a cost function that measures the performance of the controller. The cost function is a function of the error between the actual and desired axis positions. The controller parameters are updated online as the optimization takes place. This method significantly decreases the time in obtaining optimal controller parameters. Simulations were conducted for the online optimization under both fixed and varying operating conditions. The results demonstrate the usefulness of using ES for preserving the maximum attainable performance