Cam Phasing Research Articles

Intelligent Optimization Based on a Virtual Marine Diesel Engine Using GA-ICSO Hybrid Algorithm

Considering the trade-off relationship between brake specific fuel consumption (BSFC), combustion noise (CN) and NOx emission, it is a difficult task to optimize them simultaneously in a marine diesel engine. In order to overcome this problem, a novel genetic algorithm and improved chicken swarm optimization (GA-ICSO) hybrid algorithm was proposed, where the enhanced Levy flight and adaptive self-learning factor were introduced in this algorithm. Computational comparisons between GA-ICSO and other effective optimization algorithms were performed using four standard test functions, validating the improvements in both accuracy and stability for GA-ICSO. Furthermore, a predictive engine model based on a phenomenological approach was developed and validated. This model coupled the proposed algorithm for the optimization of a marine diesel engine. In the optimization process, five control parameters were selected as design variables, including injection timing (IT), intake cam phasing (ICP), intake valve closing (IVC), intake temperature and pressure. Results show that, a lower objective value can be obtained by GA-ICSO than other widely used optimization algorithms for all the operating conditions. Besides, by comparing the results between the optimal generations and baselines, it could be found that, under the condition of 50%, 75% and 100%load, CN is reduced by 10.7%, 4.9% and 3.9%, NOx is decreased by 15%, 31% and 33%, and BSFC is suppressed by 10.8%, 13.3% and 9.5%, respectively. Finally, heat release rates, noise spectrums, cylinder pressures and temperatures were all employed to discuss the optimization results of a marine diesel engine under different working conditions.

Electric Camshaft Phasing System to Meet Euro 6/BS-VI Emission Norms for Gasoline Engine

<div class="section abstract"><div class="htmlview paragraph">In today’s ever-changing scenario, gasoline engine is going to be more acceptable passenger vehicle prime mover, as it meets Bharat Stage-VI (BS-VI) emission standard and need less cost of up-gradation. Variable cam phasing (VCP) system is well known & proven advanced technology in automotive world, which already used by many OEMs globally to improve fuel consumption and reduce engine emissions. Electric Cam Phasing (ECP) is an integration of electro-mechanical system. In ECP, angle shifting is independent of engine oil pressure, which allows a more aggressive engine calibration of valve timing to minimize active intervention in the ignition and fuel injection sequences. Early advance timing makes it possible for the combustion engine to build up torque more quickly during acceleration, which means that ECP not only helps to achieve high operating efficiency, but also good driving performance. This paper will describe use of advanced features of ECP over Hydraulic Cam Phaser (HCP) in achieving improved fuel consumption & reduction in HC & CO emissions to meet BS-VI standard by precise controlling of valve timing at engine start condition and to enhance driving comfort, low engine vibrations during engine stop condition.</div></div>

Cylinder Charge Estimation in Diesel Engines with Dual Independent Variable Valve Timing

Abstract With stricter emission legislations and demands on low fuel consumption, new engine technologies are continuously investigated. At the same time the accuracy in the over all engine control and diagnosis and hence also the required estimation accuracy is tightened. Central for the internal combustion control is the trapped cylinder charge and composition. Traditionally cylinder charge is estimated using cycle averaged manifold pressures and engine speed in e.g. two dimensional look-up tables. With the introduction of variable valve timing, two additional degrees of freedom are introduced. To incorporate support for these new dimensions in a traditional look-up table estimation approach would be rather expensive in terms of model calibration and collection of empirical data. This is especially true if the cam phasers are given large enough authority to offer the powerful thermal management capabilities required to fulfill future emission legislations. Two semi-physical models for pumped mass flow through the engine are developed and evaluated on experimental data. Both utilize crank angle resolved manifold pressures and cylinder volumes at discrete valve events, e.g. intake valve closing. The data covers a large operating region in engine speed/load and large independent variations in both intake and exhaust valve timing, including valve overlap and symmetric/asymmetric underlap.

Influence of sensor and communication setup on electric cam phaser control quality

This study investigates the control quality of an electric cam phaser system. The impact of different sensor concepts, synchronization algorithms, controller and hardware topologies on the control quality is examined by using a transient simulation covering the electric cam phaser, valve train, mechanical transmission and a wide variety of cam- and crankshaft trigger wheels. Limited angular accuracy effects are simulated by realistic sensor models and the processing of sensor signals by a real-time capable synchronization algorithm. Nonlinear friction in transmission and valve train are considered by the simulation accordingly. Furthermore, the effects of distributed controller algorithms based on conventional electronic control units are evaluated. Communication latencies have a strong impact on the control plant and are taken into account during controller definition. The effects of different layouts are compared in the time domain, and a sensitivity analysis is carried out to evaluate the effects of different parameters on the cam phasing control quality. The control quality is measured in terms of overshoot, phasing duration and energy consumption of a phasing event. Using a sensor fusion for the current cam phasing angle and an integrated controller layout – that is, an architecture without any communication delay – improves the controllability and reduces overshooting, phasing duration and electrical energy consumption under transient conditions.

Development of an aggressive Miller Cycle engine with extended Late-Intake-Valve-Closing and a two-stage turbocharger

This paper describes the development of an aggressive Miller cycle gasoline engine with stoichiometric combustion, a high expansion ratio of 12.5:1, a 65 crank angle degrees (CAD) longer duration Late-Intake-Valve-Closing (LIVC) cam, and a two-stage turbocharger. The full-load performance and part-load fuel consumption of the baseline and Miller cycle engines were assessed through engine dynamometer testing. The aggressive Miller cycle engine achieved the maximum Brake Mean Effective Pressure (BMEP) of 22 bar at 1500 rpm, which was enabled by the 65 CAD longer duration LIVC cam to further reduce the effective compression for controlling knock and by the two-stage turbocharger to provide significantly higher boost for maintaining and increasing trapped mass. It was shown that the more aggressive Millerization was realized while maintaining the specific output and advantages of current downsized boosted engines, such as lower friction and lower pumping losses. The aggressive Miller cycle engine achieved above 6% brake-specific fuel consumption (BSFC) reduction over the baseline turbocharged spark-ignition engine on average. The 65 CAD longer duration LIVC cam provided the benefit of pumping loss reduction with delayed intake valve closing and the benefit of hot residual dilution with relatively advanced intake cam phasing simultaneously, which provided the significant fuel economy improvement at non-knocking light-load conditions. Even without the latest technology enhancements and friction reduction methods on its base engine hardware, the aggressive Miller cycle engine achieved a very broad BSFC island of 230 g/kWh or lower, with the lowest BSFC of 223 g/kWh at 2000 rpm and 10 bar BMEP.

Targeted Efficiency Optimisation for Gasoline Engines

The European Union’s mandatory CO2 standards for new passenger cars in 2009 set a 2015 target of 130 g/km for the fleet average of all manufacturers combined, which was met in 2013, with average EU fleet emissions amounting to 129 g/km. Individual manufacturers are allowed a higher CO2 emission value, depending on the average vehicle weight of their fleet. The heavier the average weight of the cars sold by a manufacturer, the higher the CO2 level allowed. Figure 1 shows that in order to meet the future EU emissions regulations, significant increases in gasoline engine efficiency will have to be realised. Open image in new window FIGURE 1 European CO2 targets and the derived average fuel consumptions resulting from efficiency improvements for the C- and D- vehicle segments for European passenger car markets for the intervals 2015-2021 and 2021-2025 (© FEV) Based on two representative vehicles from the C- and D-segment, which meet the present day CO2 targets, it can be demonstrated that there is a need to improve efficiency for the intervals 2015 to 2021 and 2021 to 2025. The CO2 targets of the two vehicles have been converted to specific fuel consumption targets for each of comparison. The common reduction measures — reduction in vehicle mass, reduction of rolling resistance — and electrification of the powertrain (Micro-HEV, Mild-HEV, HEV) are already considered. — In a C-Segment vehicle, the engine is allowed a maximum average fuel consumption of 256 g/kWh in 2021 and for 2025 it should be 223 g/kWh (Micro-HEV). — In a D-Segment vehicle, the engine is allowed a maximum average fuel consumption of 238 g/kWh in 2021 and for 2025 it should be 213 g/kWh (Micro-HEV). The specification of such an average fuel consumption map is readily comparable across different driving cycles and therefore provides a simple way of evaluating the various technologies in a wide scope. In contradiction, the use of micro-hybridisation to advance electrification of the gasoline engine, allows a slight increase in the maximum allowable average Brake Specific Fuel Consumption (BSFC); but the Micro-HEV must be increasingly used in the new fleet of vehicles [3]. In the analysis presented here, a three-cylinder and a four-cylinder gasoline engine are considered: — 1.0-l three-cylinder turbocharged gasoline engine with direct injection, capable of 200 Nm and 90 kW — 1.6-l four-cylinder turbocharged gasoline engine with direct injection, capable of 250 Nm and 115 kW. Both engines are turbocharged and equipped with direct fuel injection and have intake and exhaust cam phasers. Figure 2 shows the full engine operating range of the 1.0-l- and 1.6-l engines with focus on fuel consumption in the New European Drive Cycle (NEDC) and Worldwide Harmonized Light-Duty Vehicles Test Procedure (WLTP) driving cycles for the C- and D-segment vehicles. Open image in new window FIGURE 2 Engine operating range of the 1.0-l and 1.6-l engines with focus on fuel consumption (marked with red/gray outline) on the NEDC and WLTP driving cycles for the C- and D-segment vehicles (© FEV) Comparing the individual engine maps in Figure 2, it is clear to see that the average fuel consumption would be highly influenced by the different driving cycles and target vehicles. Especially when considering the high load WLTP-H (WLTP with highest vehicle mass) cycle, extended areas of the engine map will also need to be optimised. Technologies with efficacy in broad regions of the engine map will definitively have an advantage. To this effect, the next section will analyse the effectiveness of the individual fuel consumption reduction technologies.

Accounting for combustion mode switch dynamics and fuel penalties in drive cycle fuel economy

A methodology is introduced to analyze the drive cycle fuel economy of a vehicle equipped with a multimode combustion engine, utilizing commercial cam phasers and two-step cam profile switching. The analysis is based on a longitudinal vehicle model with manual transmission. The engine model employs a finite state machine describing mode switches between two distinct combustion modes, namely, spark-ignited and homogeneous charge compression ignition. Preliminary combustion mode switch experiments were used to parameterize the model. The influence of mode switch fuel penalties on drive cycle fuel economy was quantified through application of the model to the federal test procedure (FTP-75), the highway fuel economy test (HWFET) and the US06 supplemental federal test procedure. The mode switches were analyzed individually in terms of their benefit on fuel economy and a distinction was made between harmful and beneficial mode switches. Mode switches were defined as harmful whether their fuel penalty is greater than the benefits originating from spending time in the subsequent homogeneous charge compression ignition mode. A parametric study was conducted to investigate the impact of harmful mode switches on fuel economy as a function of the fuel penalties during the switch. In the case of high fuel penalties, supervisory control becomes an important tool for minimizing the number of harmful mode switches. One possible supervisory strategy discussed is a smoothing strategy, in which a mode switch is delayed by introducing a dwell time.

Development of a Cam Phaser System to Improve the Performance of a Small Engine

Development of a Cam Phaser System to Improve the Performance of a Small Engine

Delphi Electric Cam Phasing as an Enabler for CO2 Reduction

Delphi Electric Cam Phasing as an Enabler for CO2 Reduction

Mixed ${\cal H}_{2}/{\cal H}_{\infty}$ Observer-Based LPV Control of a Hydraulic Engine Cam Phasing Actuator

In this paper, a family of linear models previously obtained from a series of closed-loop system identification tests for a variable valve timing cam phaser system is used to design a dynamic gain-scheduling controller. Using engine speed and oil pressure as the scheduling parameters, the family of linear models was translated into a linear parameter varying (LPV) system. An observer-based gain-scheduling controller for the LPV system is then designed based on the linear matrix inequality technique. A discussion on weighting function selection for mixed H2/H∞ controller synthesis is presented, with an emphasis placed on examining various frequency responses of the system. Test bench results show the effectiveness of the proposed scheme.

HCCI Load Expansion Opportunities Using a Fully Variable HVA Research Engine to Guide Development of a Production Intent Cam-Based VVA Engine: The Low Load Limit

While the potential emissions and efficiency benefits of HCCI combustion are well known, realizing the potentials on a production intent engine presents numerous challenges. In this study we focus on identifying challenges and opportunities associated with a production intent cam-based variable valve actuation (VVA) system on a multi-cylinder engine in comparison to a fully flexible, naturally aspirated, hydraulic valve actuation (HVA) system on a single-cylinder engine, with both platforms sharing the same GDI fueling system and engine geometry. The multi-cylinder production intent VVA system uses a 2-step cam technology with wide authority cam phasing, allowing adjustments to be made to the negative valve overlap (NVO) duration but not the valve opening durations. On the single cylinder HVA engine, the valve opening duration and lift are variable in addition to the NVO duration. The content of this paper is limited to the low-medium operating load region at 2000rpm. Using different injection strategies, including the NVO pilot injection approach, the single-cylinder engine is operated over a load range from 160-390 kPa net IMEP at 2000 rpm. Changes to valve opening duration on the single-cylinder HVA engine illustrate opportunities for load expansion and efficiency improvement at certain conditions. For instance, the low loadmore » limit can be extended on the HVA engine by reducing breathing and operating closer to a stoichiometric air fuel ratio (AFR) by using valve deactivation. The naturally aspirated engine used here without external EGR confirmed that as operating load increases the emissions of NOx increases due to combustion temperature. NOx emissions are found to be one limitation to the maximum load limitation, the other being high pressure rise rate. It is found that the configuration of the production intent cam-based system represents a good compromise between valve lift and duration in the low to medium load region. Changing the extent of charge motion and breathing via valve deactivation prove beneficial at moderating the pressure rise rate and combustion stability and extending the low load limit at 2000rpm on the HVA engine. It also confirms that strategies using a pilot fuel injection are beneficial at low operating loads but that as operating load is increased, the benefits of multiple injection diminish to the point where a single injection offers the best performance.« less

Effects of Gasoline Direct Injection Engine Operating Parameters on Particle Number Emissions

A single-cylinder, wall-guided, spark ignition direct injection engine was used to study the impact of engine operating parameters on engine-out particle number (PN) emissions. Experiments were conducted with certification gasoline and a splash blend of 20% fuel grade ethanol in gasoline (E20), at four steady-state engine operating conditions. Independent engine control parameter sweeps were conducted including start of injection, injection pressure, spark timing, exhaust cam phasing, intake cam phasing, and air–fuel ratio. The results show that fuel injection timing is the dominant factor impacting PN emissions from this wall-guided gasoline direct injection engine. The major factor causing high PN emissions is fuel liquid impingement on the piston bowl. By avoiding fuel impingement, more than an order of magnitude reduction in PN emission was observed. Increasing fuel injection pressure reduces PN emissions because of smaller fuel droplet size and faster fuel–air mixing. PN emissions are insensitive to ...

Modeling and Control of an Exhaust Recompression HCCI Engine Using Split Injection

Homogeneous charge compression ignition (HCCI) is currently being pursued as a cleaner and more efficient alternative to conventional engine strategies. Control of the load and phasing of combustion is critical in the effort to ensure reliable operation of an HCCI engine over a wide operating range. This paper presents an approach for modeling the effect of a small pilot injection during the recompression process of an HCCI engine, and a controller that uses the timing of this pilot injection to control the phasing of combustion. The model is a nonlinear physical model that captures the effect of fuel quantity and intake and exhaust valve timings on work output and combustion phasing. It is seen that around the operating points considered, the effect of a pilot injection can be modeled as a change in the Arrhenius threshold, an analytical construct used to model the phasing of combustion as a function of the thermodynamic state of the reactant mixture. The relationship between injection timing and combustion phasing can be separated into a linear, analytical component and a nonlinear, empirical component. Two different control strategies based on this model are presented, both of which enabled steady operation at low load conditions and effectively track desired load-phasing trajectories. These strategies demonstrate the potential of split injection as a practical cycle-by-cycle control knob requiring only minimal valve motion that would be easily achievable on current production engines equipped with cam phasers.

Improving the predictiveness of the quasi-d combustion model for spark ignition engines with flexible intake systems

Fast and predictive simulation tools are prerequisites for pursuing simulation based engine control development. A particularly attractive tradeoff between speed and fidelity is achieved with a co-simulation approach that marries a commercial gas dynamic code WAVE™ with an in-house quasi-dimensional combustion model. Gas dynamics are critical for predicting the effect of wave action in intake and exhaust systems, while the quasi-D turbulent flame entrainment model provides sensitivity to variations of composition and turbulence in the cylinder. This paper proposes a calibration procedure for such a tool that maximizes its range of validity and therefore achieves a fully predictive combustion model for the analysis of a high degree of freedom (HDOF) engines. Inclusion of a charge motion control device in the intake runner presented a particular challenge, since anything altering the flow upstream of the intake valve remains “invisible” to the zero-D turbulence model applied to the cylinder control volume. The solution is based on the use of turbulence multiplier and scheduling of its value. Consequently, proposed calibration procedure considers two scalar variables (dissipation constant Cβ and turbulence multiplier CM), and the refinements of flame front area maps to capture details of the spark-plug design, i.e. the actual distance between the spark and the surface of the cylinder head. The procedure is demonstrated using an SI engine system with dual-independent cam phasing and charge motion control valves (CMCV) in the intake runner. A limited number of iterations led to convergence, thanks to a small number of adjustable constants. After calibrating constants at the reference operating point, the predictions are validated for a range of engine speeds, loads and residual fractions.

High-Degree-of-Freedom Engine Modelling for Control Design Using a Crank-Angle-Resolved Flame Propagation Simulation and Artificial Neural Network Surrogate Models

Non-linearity of the engine system creates a challenge in building a reliable control-oriented model (COM). The main source of non-linearity is the complex nature of the combustion process. Modern engine system configurations are increasingly complex and predicting their transient response poses additional difficulty. In the present paper, a COM is developed to address the challenges and capture the behaviour of a high-degree-of-freedom engine system. Engine combustion models are created by utilizing the high-fidelity engine cycle simulation to characterize the effects of main parameters, such as turbulence, air—fuel ratio, and residual fraction, and subsequently capturing the interrelationships with artificial neural networks. Then, system dynamics are accounted for by adding manifold and actuator dynamics models. The capabilities of the proposed COM are demonstrated using a spark-ignition engine with a dual-independent cam phasing as a test case. The results indicate the model's ability to accurately predict engine responses to an arbitrary schedule of engine control inputs over the feasible operating range.

Mid-ranging control of a multi-cylinder HCCI engine using split fuel injection and valve timings

Homogeneous charge compression ignition (HCCI), though a promising piston-engine strategy for the future, presents a significant control challenge due to the presence of cycle-to-cycle dynamics and the absence of a direct combustion trigger. Several actuators can be used for controlling HCCI, but each of them presents unique hurdles to practical implementation. This paper presents an approach for controlling HCCI with exhaust recompression that addresses these challenges using the principle of mid-ranging control. The controller is based on a physical, discrete-time model of HCCI presented in previous work. A split injection strategy is used, with the timing of a small pilot injection of fuel during recompression being used to control the phasing of combustion on a cycle-by-cycle basis. A slower valve motion, easily achievable on an engine equipped with cam phasers, is then used to keep the injection timing in the middle of its range of influence, maintaining the control authority to handle fast transients while respecting actuator constraints. The controller is seen to be effective in tracking desired load and phasing trajectories in simulation, and on a multi-cylinder engine testbed. In particular, the controller enables steady operation at low load conditions on the engine.

Optimizing the Calibration of a Turbocharged GDI Engine through Numerical Simulation and Direct Optimization

Different optimization strategies for the optimization of the calibration of a turbocharged GDI engine through numerical simulation were analyzed, aiming to evaluate the opportunities offered by direct optimization techniques. A one-dimensional fluid dynamic engine model was used to predict engine performance, taking into account knock and exhaust temperature constraints. Air fuel ratio, spark advance, boost pressure and cam phasing were optimized by means of different optimization strategies, including direct search as well as numerical methods. Both full load (with maximum bmep targets) and part load (with minimum bsfc targets) were considered. The potential for remarkable improvements (up to 10% bmep increase at full load and 8 g/kWh bsfc decrease at part load) in comparison with the baseline engine calibration was highlighted, and a ranking between different optimization methods was obtained, based on the requested computational efforts and on their capabilities to handle constrained optimization problems

A Detailed Chemistry Simulation of the SI-HCCI Transition

A Stochastic Reactor Model (SRM) has been used to simulate the transition from Spark Ignition (SI) mode to Homogeneous Charge Compression Ignition (HCCI) mode in a four cylinder in-line four-stroke naturally aspirated direct injection SI engine with cam profile switching. The SRM is coupled with GT-Power, a onedimensional engine simulation tool used for modelling engine breathing during the open valve portion of the engine cycle, enabling multi-cycle simulations. The model is initially calibrated in both modes using steady state data from SI and HCCI operation. The mode change is achieved by switching the cam profiles and phasing, resulting in a Negative Valve Overlap (NVO), opening the throttle, advancing the spark timing and reducing the fuel mass as well as utilising a pilot injection. Experimental data is presented along with the simulation results. The model is used to investigate key control parameters and their effects on parameters that are difficult to measure experimentally. The effect of the spark in the first HCCI cycles is found to have a major impact on the stability of the transition.

Impact of variable valve timing on power, emissions and backfire of a bi-fuel hydrogen/gasoline engine

Hydrogen-fueled internal combustion engines are a possible solution to make transportation more ecological. Apart from difficulties in production and storage of hydrogen, there are three major bottlenecks in the operation of hydrogen-powered engines: reaching a high power output, reducing NO x emissions at high loads and avoiding backfire. This paper presents an experimental study of the influence of continuously variable valve timing of the intake valves on these bottlenecks. Measurements were performed on a four-cylinder engine that can run on gasoline as well as on hydrogen. The measurements on hydrogen are compared to those on gasoline. For hydrogen, the effects of the cam phasing were investigated at wide open throttle, where load is controlled by the quality of the mixture (equivalence ratio) as well as in throttled mode, where load is defined by the quantity of mixture. Results show that it is possible to optimize the applied control strategy by using variable valve timing as a means to increase the range of both the qualitative and quantitative load control methods, which contributes to an easier switch between both methods.

Variable valve timing complementing Hybrid-EGR at diesel engines

To understand the benefits of the Atkinson cycle added to a two-stage boosting system including Hybrid-EGR, engine simulations were carried out by BorgWarner. The possible valve curves were determined by a real variable valve timing device consisting of two concentric camshafts with an integrated cam phaser. The results promise a higher degree of freedom in tradeoffs between fuel economy, NOx emission and Particulate Matters (PM).