Search

This paper presents a novel approach to augment existing engine calibrations to deliver improved engine performance during a transient through the application of multi-objective optimization techniques to the calibration of the Variable Valve Timing (VVT) system of a 1.0 litre gasoline engine. Current mature calibration approaches for the VVT system are predominantly based on steady state techniques which fail to consider the engine dynamic behaviour in real world driving, which is heavily transient. In this study the total integrated fuel consumption and engine out NOx emissions over a 2min segment of the transient Worldwide Light-duty Test Cycle are minimised in a constrained multi-objective optimisation framework to achieve an updated calibration for the VVT control. The cycle segment was identified as an area with high NOx emissions. The optimisation framework was developed around a Mean Value Engine Model with representative engine controls which was validated against an engine tested on a dynamometer. The aim of this study was to demonstrate a practical benefit without having to significantly change the existing engine control strategy. Offline optimization with the MVEM model allows exploitation of workstation computational performance to effectively explore the calibration space, reducing both time and investment in engine testing. The initial optimization results show a strong dominance of both fuel and NOx objectives with a potential reduction in fuel consumption and engine out NOx emissions of up to 5% and 18% respectively compared to the original steady-state based VCT calibration. Engine experimental results have confirmed that NOx emissions can be significantly reduced without any significant detriment to fuel economy over this 2min transient.

Methanol is gaining traction in some regions, e.g. for road transportation in China and for marine transportation in Europe. In this research, the possibility for achieving higher power output and higher efficiency with methanol, compared to gasoline, is investigated and the influence of several engine settings, such as valve timing and intake boost control, is studied. At wide open throttle (WOT), engine speed of 1650 rpm, the brake mean effective pressure (BMEP) of the methanol-fueled engine is higher than on gasoline, by around 1.8 bar. The maximum BMEP is further increased when positive valve overlap and higher intake boost pressure are applied. Thanks to a lower residual gas fraction, and a richer in-cylinder mixture with positive valve overlap period, the engine BMEP improves by a further 2.6 bar. Because of higher volumetric efficiency with a boosted intake air, the engine BMEP enhances with 4.7 bar. The maximum BMEP for gasoline was found through a test matrix using the design of experiment approach. At that BMEP (16.3 bar), the efficiency when fueling the engine with methanol improves by 22.7% relatively with valve overlap control and by 25.75% with intake boost control. The BMEP of the methanol engine can increase to a higher value without knock when a higher boost pressure or a longer valve overlap duration is employed. Limitations are no longer engine knock, but excessive peak in-cylinder pressures, however, being over 100 bar. If the maximum pressure is limited to 100 bar, the downsizing potential with boost control is higher than with variable valve timing. The engine could be further downsized by ~10.7% with methanol by boosting the intake pressure.

Modern automotive engines almost exclusively operate on the 4-stroke Otto cycle and utilize poppet valves for gas exchange. This state of affairs has not always been the case, however, and one unusual and relatively successful technology that was once in mass production (albeit in piston aero engines) was the Burt-McCollum single sleeve valve. This paper investigates the timing and angle-area of a Bristol Centaurus engine cylinder, which utilized such a single sleeve valve for gas exchange, using some modern tools. A comparison with poppet valve angle-areas is made. Finally, the results are also used to study the potential of variable valve timing and the interaction with variable compression ratio of a single sleeve mechanism. An opportunity for the sleeve valve is provided by the fact that direct injector placement in the cylinder junk head is effectively completely free, and furthermore multiple ignition sites can be incorporated to increase the delivered ignition energy for dilute mixtures, for example. Furthermore, as there are no mechanical impact loads (as arise from poppet valves hitting their seats, for instance), theoretically ceramics or temperature-swing materials could be more simply applied when using the technology as well, and over a larger proportion of the total combustion chamber surface area than is possible with poppet valves. The motivation for studying the interaction of timing and compression ratio was driven by the observation that it would be relatively simple to incorporate a wide-range continuously-variable compression ratio mechanism without the spatial limitations enforced by the presence of poppet valves and their timing and drive mechanisms in the cylinder head of a conventional 4-stroke engine. The potential range of compression ratio variation is also significantly larger than for poppet-valve engines because the piston does not have to incorporate valve pockets for valve-to-piston clearance at high compression ratio settings. As a result the surface-area-to-volume ratio of the combustion chamber would be expected to be less effected over any given ratio range as well. The results of this study show a very favourable trade-off between port timing, compression and expansion ratios with a simple variable compression ratio mechanism being employed. Furthermore, the system is found to provide a large potential to yield increased Miller cycle operation automatically.

As part of the U.S. Environmental Protection Agency (U.S. EPA) “Midterm Evaluation of Light-duty Vehicle Standards for Model Years 2022-2025 [1]”, the U.S. EPA is evaluating engines and assessing the effectiveness of future engine technologies for reducing CO2 emissions. Such assessments often require significant development time and resources in order to optimize intake and exhaust cam variable valve timing (VVT), exhaust gas recirculation (EGR) flow rates, and compression ratio (CR) changes. Mazda

In this study, the effects of Variable Valve Timing (VVT) on the performance of a Homogeneous Charge Compression Ignition (HCCI) engine are analyzed by developing a computationally efficient modeling approach for the HCCI engine cycle. A full engine cycle model called Sequential Model for Residual affected HCCI (SMRH) is developed using a multi zone thermokinetic combustion model coupled with flow dynamic models. The SMRH utilizes CHEMKIN ® -PRO and GT-POWER ® software along with an in-house exhaust gas flow model. Experimental data from a single cylinder HCCI engine is used to validate the model for different operating conditions. Validation results show a good agreement with experimental data for predicting combustion phasing, Indicated Mean Effective Pressure (IMEP), thermal efficiency as well as CO emission. The experimentally validated SMRH is then used to investigate the effects of intake and exhaust valve timing on residual affected HCCI engine combustion. A new Fuel Efficiency and Emission (FEE) index is defined to optimize engine performance. SMRH is used as a virtual engine test bed to generate FEE contour maps as a function of valve timings. The simulation results determine optimum valve timings with the highest FEE index. The results indicate the SMRH is of utility for design of VVT strategies to control the HCCI engine in optimum regions with low engine-out emissions and low fuel consumption.

This paper presents the development and implementation of an analytical target cascading (ATC) multi-disciplinary design optimisation (MDO) framework for the steady state engine calibration optimisation problem. A case study on variable valve timing calibration for a gasoline engine was considered to illustrate the analysis and mathematical formulation of the calibration optimisation as an ATC framework, and its Matlab implementation with gradient based and evolutionary optimisation algorithms. The results and performance of the ATC are discussed comparatively with the conventional two-stage approach to steady state calibration optimisation. The conclusion is that ATC offers a powerful and efficient approach for engine calibration optimisation, delivering better solutions at both ‘Global’ and ‘Local’ levels. The ATC framework is flexible and scalable to the complexity of the calibration problem, and enables calibrator preference to be incorporated a priori in the optimisation problem formulation, delivering important time saving for the overall calibration development process.

A two-input and two-output physical model for pressures and combustion phases was built to realize the coordinated control of the peak pressures and combustion phases for a homogeneous charge compression ignition (HCCI) engine. This model is based on the Shaver' residual-affected HCCI engine model with the constant wall temperature heat transfer model suitable for HCCI combustion. A cooperative control system of pressure and combustion phase was designed using the model predictive control (MPC) theory with the variable valve timing (VVT) as the control method. The coordinated simulation experiment was done by using GT-Power and Matlab/Simulink. The results show that the control model satisfies the engine control demand, realizes the collaborative control of the pressure and combustion phase with control accuracies of ±30 kPa and ±0.6° CA, and the response time of 6-7 engine cycles.

International audience; Increasing the degrees of freedom in the air path has become a popular way to reduce the fuel consumption and pollutant emissions of modern combustion engines. That is why technical definitions will usually contain components such as multi or single-stage turbocharger, throttle, exhaust gas recirculation loops, wastegate, variable valve timing or phasing, etc. One of the biggest challenges is to precisely quantify the gas flows through the engine. They include fresh and burnt gases, with trapping and scavenging phenomena. An accurate prediction of these values leads to an efficient control of the engine air fuel ratio and torque. Fuel consumption and pollutant emissions are then minimized. In this paper, we propose to use an artificial neural networkbased model as a prediction tool for the engine volumetric efficiency. Results are presented for a downsized turbocharged spark-ignited engine, equipped with inlet and outlet variable valve timing. The calibration process that is used in this study only requires steady-state operating points. The validation stage was conducted on both steady-state and vehicle transients. Model prediction is in very good agreement with experimental results while keeping a very low calibration effort and matching embedded computational requirements. The conclusion stresses that thanks to their generic structure, neural models offer an interesting potential for generalization to even more complex technical definitions.

As it is well known one of the most harmful emissions in SI engines is NOx and there are several ways to minimize NOx emission. Internal exhaust gas recirculation (IGR) is an effective way to control and minimize NOx concentration in exhaust gas. In this paper, a method for minimizing NOx emission by use of IGR and variable valve timing (VVT) is introduced. In this method, formation of NOx is controlled by mass fraction of residual gas (RG) and mass fraction of RG is controlled by variable timing of exhaust valves opening and closing so not only the timing of exhaust valves changes but also the lift profile of exhaust valves is variable. In this paper, first a thermodynamic model of a SI engine was developed and validated by experimental data. The model was a reliable tool for predicting engine performance and emission characteristics. The effect of variable exhaust valve timing on RG mass fraction, NOx formation and brake specific fuel consumption was investigated. Then a multi-objective genetic algorithm (NSGA II) was applied to find the optimum timing and lift duration of exhaust valve.

In a gasoline engine, the cycle-by-cycle fresh trapped charge, and corresponding unswept residual gas fraction (RGF) are critical parameters of interest for maintaining the desired air-fuel ratio (AFR). Accurate fueling is a key precursor to improved engine fuel economy, and reduced engine out emissions. Asymmetric flow paths to cylinders in certain engines can cause differences in the gas exchange process, which in turn cause imbalances in trapped fresh charge and RGF. Variable cam timing (VCT) can make the gas exchange process even more complex. Due to the reasons stated above, simplified models can result in significant estimation errors for fresh trapped charge and RGF if they are not gas dynamics-based or detailed enough to handle features such as variable valve timing, duration, or lift. In this paper, a new air flow and RGF measurement tool is introduced. The tool is a combination of 1-D gas dynamics modeling and imposed, measured dynamic pressure signals in the intake and exhaust manifolds. With this method, the components to be modeled in the gas exchange system are reduced to a minimum, making it possible to model the gas exchange process with adequate detail and still maintain reasonable tool execution time. In this approach, the accuracy of the air flow and RGF estimation are not influenced by the location of pressure transducers and it is possible to “track” EGR flow from the exhaust to the intake system. The tool is demonstrated on a 4-cylinder gasoline engine powered vehicle with dual intake and exhaust cam phasing. Predictions from the tool are compared to AFR and other real-time signals measured during a variety of different real-world transient drive cycles. The instantaneous fresh trapped charge, RGF across all cylinders, as well as the influence of VCT actuation is discussed.

Most automobile manufacturers have developed hybrid vehicles that combine an internal combustion engine and an electric motor, fusing the advantages of these two power sources. For example, Toyota, in its Prius II, uses a highly efficient gasoline engine based on a modified Atkinson cycle featuring a variable valve timing management. This implementation of the Atkinson cycle is not the optimal solution because some of the air is first sucked from the intake manifold into the cylinder and subsequently returned. This oscillating air stream considerably reduces the thermal conversion efficiency of this cycle. This paper analyzes in detail the loss of thermal conversion efficiency of an internal combustion engine especially for modified Seiliger and Atkinson cycles - and a proposal is made for the improvement of aspirated and supercharged engines.

In modern four-stroke automotive engine, variable valve technology offer potential benefits for making a highperformance engine. In this paper, a novel electromechanical fully variable valve system (EMFVVS) is introduced. Just like the conventional mechanical variable valve systems, this design still uses a camshaft mechanism, but it is integrated into an electrohydraulic system to form an electromechanical system. The use of electrohydraulic system is to provide input hydraulic pulses to drive the engine valves cyclically. The output valve profile is controlled electronically by a common proportional pressure relief valve, and hence Late-ValveOpening + Early-Valve-Closing + Variable-Max-ValveLift can be achieved. The construction of the mathematical model of the variable valve system and its dynamic analysis, and some design issues are presented in this paper. Experimental and simulation results show that the novel electromechanical variable valve system can achieve fully variable valve timing and lift control without using complex control systems, and has the potential to eliminate the traditional throttle valve in the gasoline engines.

The effect on the intake flow field, air fuel mixing processes, thermodynamic performance and emissions output has been investigated for a range of valve operating profiles. A standard speed load point of 2000 rpm and 2.7 bar IMEP720° has been reached by throttling the intake whilst running standard cam profiles, by early closing of both inlet valves (EIVC) and by early closing of each inlet individually to generate bulk swirl motions within the cylinder. Data has been recorded at stoichiometric air fuel ratios for both direct injection and port fuelled operation. The valve profiles have been applied to two single cylinder homogeneous gasoline direct injection (GDI) spark ignition engines, developed to investigate the potential of controlling engine load by limiting the inducted air mass using fully variable valve timing (FVVT) to reduce pumping losses at part load. The first engine featured a full length optical liner, allowing 2D Particle Image Velocimetry (PIV) measurements of the intake flow fields to be made, along with Mie imaging studies of the liquid fuel fraction. The second was a thermodynamic engine equipped to measure specific fuel consumption and emissions of CO2, CO, NOX and THC. The work shows that fuel economy benefits can be gained by operating the engine with unthrottled EIVC operation. However, the interaction between the intake air and direct injection fuel spray means performance is highly dependant upon which valve is operated and the timing of the direct injection fuel spray. Copyright © 2007 SAE International.

Urban traffic involves frequent acceleration and deceleration. During deceleration, the energy previously used to accelerate the vehicle is mainly wasted on heat generated by the friction brakes. If this energy that is wasted in traditional IC engines could be saved, the fuel economy would improve. One solution to this is a pneumatic hybrid using variable valve timing to compress air during deceleration and expand air during acceleration. The compressed air can also be utilized to supercharge the engine in order to get higher load in the first few cycles when accelerating. A Scania D12 single-cylinder diesel engine has been converted for pneumatic hybrid operation and tested in a laboratory setup. Pneumatic valve actuators have been used to make the pneumatic hybrid possible. The actuators have been mounted on top of the cylinder head of the engine. A pressure tank has been connected to one of the inlet ports and one of the inlet valves has been modified to work as a tank valve. The goal has been to test and evaluate 2 different modes – compression mode (CM) where air is stored in an air tank during deceleration and air-motor mode (AM) where the previously stored pressurized air is used for accelerating the vehicle. This paper also includes an optimization of the CM.

Cam phasing, or Variable Valve Timing (VVT), is an electro hydraulic and mechanical camshaft control concept managed by the vehicle's microcontroller engine management system. Development and implementation of cam phasing mechanisms is pursued by the automotive industry today because it gives measurable increase in performance, and reduction in undesired engine emissions. This paper illustrates the usage of virtual prototyping techniques to efficiently investigate cam phasing architecture control algorithm implementation to permit more robust cam phasing design. The control algorithm implementation resides in Simulink, and the virtual prototype of a complete hydraulic vane cam phaser system resides in a selected analog mixed technology simulator. Co-simulation enables the two different simulation engines to communicate, hence dynamic controller development can commence against virtual hardware. Cam phaser response is heavily dependent on engine oil temperature and pressure. As a specific conceptual example, a simple initial controller is developed that does not consider oil temperature and pressure fluctuations. An enhanced more robust controller is then implemented to account for these system variances. The ability to develop the entire control algorithm in a tool suited for that purpose, and then to test the controller with a highfidelity system plant modeled in another simulation environment is illustrated using robust engineering techniques.

Cam-phasing is increasingly considered as a feasible Variable Valve Timing (VVT) technology for production engines. Additional independent control variables in a dual-independent VVT engine increase the complexity of the system, and achieving its full benefit depends critically on devising an optimum control strategy. A traditional approach relying on hardware experiments to generate set-point maps for all independent control variables leads to an exponential increase in the number of required tests and prohibitive cost. Instead, this work formulates the task of defining actuator set-points as an optimization problem. In our previous study, an optimization framework was developed and demonstrated with the objective of maximizing torque at full load. This study extends the technique and uses the optimization framework to minimize fuel consumption of a VVT engine at part load. By adding a penalty term for NOx emissions in the optimization objective, the tradeoff of fuel consumption and NOx emissions is explored. The methodology relies on high-fidelity simulations for pre-optimality studies and as means of generating data that characterize engine behavior in the multidimensional space. Artificial Neural Networks (ANN) are then trained on sets of high-fidelity simulation data and used as surrogate models, thus enabling optimization runs requiring hundreds of function evaluations. A case study performed for a DaimlerChrysler 2.4 liter fourcylinder SI engine demonstrates the use of the algorithm for minimizing fuel consumption while simultaneously meeting NOx emission targets.

The control of Homogeneous Charge Compression Ignition (HCCI) (also known as Controlled Auto Ignition (CAI)) has been a major research topic re- cently, since this type of combustion has the poten- tial to be highly efficient and to produce low NOx and particulate matter emissions. Ion current has proven itself as a closed loop control feedback for SI engines. Based on previous work by the authors, ion current was acquired through HCCI operation too, with promising results. However, for best utilization of this feedback signal, advanced in- terpretation techniques such as artificial neural net- works can be used. In this paper the use of these advanced techniques on experimental data is explored and discussed. The experiments are performed on a single cylinder cam- less (equipped with a Fully Variable Valve Timing (FVVT) system) research engine fueled with com- mercially available gasoline (95 ON). The results obtained display an improvement in the correlation between characteristics of ion current and cylinder pressure, thus allowing superior monitoring and con- trol of the engine. Peak pressure position can be estimated with sufficient precision for practical ap- plications, thus pushing the HCCI operation closer to its limits.

This paper describes a model of a 1.8-litre four-cylinder four-stroke gasoline engine fitted with a close-coupled three-way catalyst (TWC). Designed to meet EURO 3 emissions standards, the engine includes some advanced emission control features in addition to the TWC, namely: variable valve timing (VVT), swirl control plates, and exhaust gas recirculation (EGR). Gas flow is treated as one-dimensional (1D) and unsteady in the engine ducting and in the catalyst. Reflection and transmission of pressure waves at the boundaries of the catalyst monolith are modelled. In-cylinder combustion is represented by a two-zone burn model with dissociation and reaction kinetics. A single Wiebe analysis of measured in-cylinder pressure data is used to determine the mass fraction burned as a function of crank angle (CA) at each engine speed. Measured data from steady-state dynamometer tests are presented for operation at wide open throttle (WOT) over a range of engine speeds. These results include CA-resolved traces of pressure at various locations throughout the engine together with cycle-averaged traces of gas composition entering the catalyst as indicated by a fast-response emissions analyser. Simulated engine performance and pressure wave action throughout the engine are well validated by the measured data.

One of the main challenges with the Homogeneous Charge Compression Ignition, HCCI, combustion system is to control the Start Of Combustion, SOC, for varying load and external conditions. A method t ...

The demand for emission control and improved fuel economy is one of the driving forces behind new automotive technologies. Variable valve timing, 42-volt architecture, fuel cells are all gaining acceptance as viable technologies. This paper reviews briefly these technologies and how powder metal parts usage in the automobile will be affected.

Residual-effected HCCI is investigated using a single-cylinder research engine equipped with fully-flexible variable valve actuation. Dilution limits are explored with various valve profiles in order to gain insight into the best way to use exhaust residual to achieve and control HCCI. The tests repeatedly point out the importance of delayed combustion phasing to reduce thermal losses and maximize efficiency. Combustion phasing is not significantly affected by charge in-cylinder residence time, but is strongly influenced by both the level of exhaust residual and by valve strategies that aim to affect homogeneity. Further dilution with air shows little promise for reaching lower loads, but does suggest that operation near the lean limit can maximize efficiency while minimizing NO and CO emissions. Comparison of exhaust reinduction and exhaust retention (negative valve overlap) strategies shows that, at the same load, reinduction strategies have significantly higher efficiency and reduced NO emissions, though they suffer from higher HC emissions. Reinduction strategies also show some ability to recover from a misfire while retention strategies do not. The data show that the best combination of load range, efficiency, and emissions may be achieved using a reinduction strategy with variable intake lift instead of variable valve timing.

General Motors adds a larger displacement more powerful variant to its global 4-cylinder engine family. The new Ecotec 2.4L VVT, being introduced in the 2006 Pontiac Solstice is the latest variant within the Ecotec engine family. This new engine is built on the heritage and excellent reputation of the Ecotec 2.2L (1) , the global 4-cylinder engine introduced for the North American market in the 2000 model year Saturn L-series. Ecotec engines are now offered in many additional GM platforms in North America as well as in Europe. The Ecotec 2.4L VVT shares many parts with the Ecotec 2.2L (1) , with addition of cam phaser technology to enable variable valve timing (VVT) along with several structural enhancements. The Ecotec 2.4L VVT produces 25% more power, impressive torque at lower engine speeds and offers a number of other advantages. Production of the Ecotec 2.4L VVT is integrated with the Ecotec 2.2L (1) resulting in efficient use of the manufacturing systems already in place, at the same time providing flexibility to split the production volumes for the two engines based on the demand.

An accurate air flow rate model is critical for high-quality air-fuel ratio control in Spark-Ignition engines using a Three-Way-Catalyst. Emerging Variable Valve Timing technology complicates cylinder air charge estimation by increasing the number of independent variables. In our previous study (SAE 2004-01-3054), an Artificial Neural Network (ANN) has been used successfully to represent the air flow rate as a function of four independent variables: intake camshaft position, exhaust camshaft position, engine speed and intake manifold pressure. However, in more general terms the air flow rate also depends on ambient temperature and pressure, the latter being largely a function of altitude. With arbitrary cam phasing combinations, the ambient pressure effects in particular can be very complex. In this study, we propose using a separate neural network to compensate the effects of altitude on the air flow rate. A predictive, high-fidelity simulation tool is used to generate training samples for the altitude compensation ANN. Compared with a test-based approach both developmental cost and time are reduced. The effectiveness of the proposed approach is evaluated and validated by both engine dynamometer tests and in-vehicle tests.

In today's state of the art vehicle drive trains, there is hardly any major component that is not controlled or monitored electronically. Especially the complex modern combustion have a wide variety of parameters like injection, ignition, variable valve timing, variable port geometry, EGR etc. This variability allows unprecedented performance, fuel consumption, emission levels and driveability, but requires a tremendous effort for calibration of the ECU. Modern test bed technology, DOE, design of experiments, and powerful calibration software are required to handle the increased number of test runs which are necessary to for calibration of such a complex, modern combustion engine system. However, high dynamic engine test beds, drive train test beds, or the simulation of climatic conditions increase testing costs, and after all, even the most sophisticated technologies can't reproduce the complexity of a complete vehicle and real driving conditions. Therefore, taking measurements in the vehicle in addition to best bed measurements, provides a potentially cost and time saving alternative, with the advantage of absolutely realistic measurement conditions, but at the expense of reproducibility of measurement runs. It has proven to improve the quality and reliability of the engine application, control systems and components in the vehicle, and according to a major car manufacturer, was for example crucial for bringing SULEV vehicles into production. Using combustion diagnosis systems in combination with an ECU application system to measure data in correlation to the combustion cycles has opened new insight into the processes and the interrelations between ECU, injection system, combustion system, exhaust system, engine mechanics, on-board electronics and other parts of the vehicle. The detailed information about every single combustion and its parameters enables application and development engineers to optimize the vehicle performance under all conditions. It helps to identify and consequently correct ECU function errors, to optimize the strategies for emission reduction, and to improve the responsiveness and driveability of the vehicle. Additionally, these aspects of vehicle quality can be verified and tested under all climatic conditions or sea levels. This paper will take a look at the measurement system that can be used for such measurements, and the type of data which can be acquired. It will discuss some examples of improvements in engine calibration, emissions, performance and engine hardware. It will show how the in-vehicle measurement approach ideally supplements testbed testing to reach emission limits, and to improve and fine tune engine performance and driveability while keeping costs under control.

The emerging Variable Valve Timing (VVT) technology complicates the estimation of air flow rate because both intake and exhaust valve timings significantly affect engine's gas exchange and air flow rate. In this paper, we propose to use Artificial Neural Networks (ANN) to model the air flow rate through a 2.4 liter VVT engine with independent intake and exhaust camshaft phasers. The procedure for selecting the network architecture and size is combined with the appropriate training methodology to maximize accuracy and prevent overfitting. After completing the ANN training based on a large set of dynamometer test data, the multi-layer feedforward network demonstrates the ability to represent air flow rate accurately over a wide range of operating conditions. The ANN model is implemented in a vehicle with the same 2.4 L engine using a Rapid Prototype Controller. Comparison between a mass air flow (MAF) sensor and the ANN model during a typical dynamic maneuver shows a very good agreement and superior behavior of the network during the transient. Practical recommendations regarding the production implementation of the ANN are provided as well.

The presented results are part of a research project to create a universal residual gas fraction model. It is supported by the ,,Forschungsvereinigung Verbrennungs-kraftmaschinen e.V. (FVV). In the research project an universal formula has been developed which allows the determination of the residual gas fraction in allkind of IC engines. The formula is valid for naturally aspirated engine, turbo and super charged, variable valve timing and fully variable valve trains, as well. The formula (constant approach) developed during the project is based on variables like time averaged intake and exhaust pressure, exhaust temperature and geometric engine data which were measured on the test bench. As a result, online and real time calculation is possible already while the engine is running. This implies that the formula can be used within the engine control unit for control purposes. The comparison of the results from the thermodynamic gas exchange analysis and the 1-dimensional simulation (GT-Power) shows a good correlation with the experimental results. The outcome of the newly developed calculation method (constant statement) obtain simple models of Heywood and Muller-Bertling[1,2,6,9]. The improved values can be used for fast in advance calculations of the internal residual gas mass.

Homogeneous Charge Compression Ignition (HCCI) engine concept has the potential to be high efficient and to produce low NOx and particulate matter emissions. However, the problem of controlling the combustion over the entire load/speed range limits its practical application. The HCCI combustion is controlled by chemical kinetics of the charge mixture, with no influence of the flame diffusion or turbulent propagation. Therefore, to achieve a successful control of the HCCI process, the composition, temperature and pressure of the charge mixture at IVC point have to be controlled. The use of the variable valve timing strategy that enables quick changes in the amount of trapped hot exhaust gases shows the potential for the control of the HCCI combustion. The aim of this paper is to analyse influence of the variable valve timing strategy on the gas exchange process, the process between the first valve open event (EVO) and the last valve closing event (IVC), in a HCCI engine fuelled with standard gasoline fuel (95RON). The gas exchange process affects the engine parameters and charge properties and therefore plays a crucial role in determining the control of the HCCI process. Analysis is performed by the experimental and modelling approaches. The single-cylinder research engine equipped with the fully variable valve train (FVVT) system was used for the experimental study. A combined code consisting of a detailed chemical kinetics code and one-dimensional fluid dynamics code was used for the modelling study. The results obtained indicate that the variable valve timing strategy has a strong influence on the gas exchange process, which in turn influences the engine parameters and the cylinder charge properties, hence the control of the HCCI process. The EVC timing has the strongest effect followed by the IVO timing, while the EVO and IVC timings have the minor effects.

In recent years, increasing attention has been paid to a non-throttling technology that is expected to contribute to a reduction in fuel consumption. This paper describes a study on the technology behind the electromagnetic variable valve timing mechanism (electromagnetic valve mechanism). The electromagnetic valve mechanism ensures highly efficient and stable valve opening/closing control. The detailed information and findings will be described in the main body. In addition, the advantages of the mechanism's application to a homogeneous charge compression ignition engine (HCCl engine) will also be described.

Variable cam timing strategies which utilize retard of the intake and exhaust valve events at part load have been previously shown to provide improved fuel consumption and feedgas NOx. These benefits can be increased by enhancing the combustion system with variable charge motion. A variable event duration valvetrain was simulated on engine dynamometer by running a series of short duration/low lift intake valve events. The fuel consumption benefit for this simulated variable event valvetrain is compared to that of dual retard VCT with variable charge motion. An estimated upper limit for the fuel consumption improvement potential of variable valve timing is presented. This upper limit includes both pumping work reduction and indicated efficiency improvement with high levels of exhaust residual dilution. The measured benefits of dual retard VCT and of the variable event valvetrain are compared to the estimated upper limit.

This paper discusses the design and control of a two-stage electro-hydraulic camless Variable Valve Actuation (VVA) system designed for gasoline engines that encompass a wide rpm range. The VVA portion of each engine valve assembly in the system consists of two miniature pilot valves, a proportional valve, a compound engine valve actuator and an engine valve return mechanism. The design and proper control of these devices allow for variable valve timing, lift, duration, seating velocity and flank velocity. This flexibility enables an array of combustion strategies. Many of these strategies (such as Miller cycle operation, cylinder and valve deactivation, etc.) have been tested on fired engines that have been redesigned to incorporate the VVA system. Test results for both bench and fired engines running in a dynamometer cell are presented. These results indicate the current level of controllability of the system and the power consumed by the system in a variety of test conditions.

The paper reports the research activity related to the development of a twin-spark Sl engine equipped with a variable valve timing (VVT) device. Improvements on the fuel consumption at part load are expected when an high internal exhaust gas recirculation (internal EGR) level is realized with a proper phasing of the VVT device. The twin-spark solution is implemented to improve the burning speed at low load, and to increase the EGR tolerance levels. Both experimental and theoretical analyses are carried out to investigate the real advantages of the proposed engine architecture. In particular an original quasi-dimensional model for the simulation of the burning process in a twin-spark engine is presented. The model is mainly utilized to find the proper combination of VVT device position (and hence EGR level) and spark advance for different engine operating conditions. A comparison with the single-spark solution is also provided. In addition, a procedure for the estimation of the sound pressure levels originated from the combustion process is utilized, to estimate the increased radiated noise associated to the double ignition. The model is well suited to define the control strategy maps of the engine in its whole operating range.