Electro-pneumatic variable valve actuation system for camless engine: Part II-fuel consumption improvement through un-throttled operation

The environmental concerns officially aroused in 1970s made the control of the engine emissions a major issue for the automotive industry. The corresponding reduction in fuel consumption has become a challenge so as to meet the current and future emission legislations. Given the increasing interest retained by the optimal use of a Variable Valve Actuation (VVA) technology, the present paper investigates into the potentials of combining the VVA solution to CNG fuelling. Experiments and simulations were carried out on a heavy duty 6-cylinders CNG engine equipped with a turbocharger displaying a twin-entry waste-gate-controlled turbine. The analysis aimed at exploring the potentials of the Early Intake Valve Closure (EIVC) mode and to identify advanced solutions for the combustion management as well as for the turbo-matching. The engine model was developed within the GT-Power environment and was finely tuned to reproduce the experimental readings under steady state operations. The 0D-1D model was hence run to reproduce the engine operating conditions at different speeds and loads and to highlight the effect of the VVA on the engine performance as well as on the fuel consumption and engine emissions. Pumping losses proved to reduce to a great extent, thus decreasing the brake specific fuel consumption (BSFC) with respect to the throttled engine. The exhaust temperature at the turbine inlet was kept to an almost constant value and minor variations were allowed. This was meant to avoid an excessive worsening in the TWC working conditions, as well as deterioration in the turbocharger performance during load transients. The numerical results also proved that full load torque increases can be achieved by reducing the spark advance so that a higher enthalpy is delivered to the turbocharger. Similar torque levels were also obtained by means of Early Intake Valve Closing strategy. For the latter case, negligible penalties in the fuel consumption were detected. Moreover, for a given combustion phasing, the IVC angle directly controls the mass-flow rate and thus the torque. On the other hand, a slight dependence on the combustion phasing can be detected at part load. Finally, the simulations assessed for almost constant fuel consumption for a wide range of IVC and SA values. Specific attention was also paid to the turbocharger group functioning and to its correct matching to the engine working point. The simulations showed that the working point on the compressor map can be optimized by properly setting the spark advance (SA) as referred to the adopted intake-valve closing angle. It is anyhow worth observing that the engine high loads set a constraint deriving from the need to meet the limits on the peak firing pressure (PFP), thus limiting the possibility to optimize the working point once the turbo-matching is defined.

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Design of a New Mechanical Variable Valve Actuation System for Motorcycle Engines

Volume 3: Advanced Composite Materials and Processing; Robotics; Information Management and PLM; Design Engineering ◽

10.1115/esda2012-82317 ◽

2012 ◽

Cited By ~ 2

Author(s):

Carmelina Abagnale ◽

Mariano Migliaccio ◽

Ottavio Pennacchia

Keyword(s):

High Performance ◽

Numerical Procedure ◽

Valve Lift ◽

Variable Valve Actuation ◽

Actuation System ◽

Mechanical Variable ◽

System 2 ◽

Variable Valve ◽

System 1 ◽

Valve Actuation

This paper deals with design and manufacturing of a mechanical variable valve actuation (VVA) system, developed as part of a MUR financed research project concerning the realization of a high performance motorcycle engine, through a partnership of Moto Morini (Bologna), Dell’Orto (Milano), Istituto Motori - CNR (Napoli) and DiME (Department of Mechanical Engineering and Energetics) – University of Napoli Federico II. After a synthetic description of the main variable valve actuation methods currently employed, the paper presents the results of our mechanical VVA system, consisting of three main elements: cam, main rocker arm with fixed fulcrum and secondary rocker arm with mobile fulcrum. This VVA system (system 1) enables valve lift variation by a simple translation of one of the three elements (the intermediate one). The study has been conducted implementing a numerical procedure specifically designed to determine cam profile and kinematic and dynamic characteristics of the whole system, starting from the following input data: rocker arm geometry, relative positions and inertial data of elements, spring stiffness and preloading, camshaft speed and valve lift law. The model has been validated against the conventional timing system using kinematic simulations. Results of the numerical procedure verify the validity of the VVA system, capable of a valve lift variation, with a limited acceleration. Starting from the numerical results, we have developed a new mechanical variable valve actuation system (system 2): it consists of the same three elements used previously, but they are connected in a different way. The newer system enables more general lift profile distributions with a similar geometric complexity. The activity has been extended to research for a new solution (always a mechanical system), capable to allow inlet valves complete closing and timing and duration variation (system 3). This paper reports results reachable with the simplest system 1, that gives better perspectives of use for a new two-wheel vehicle engine.

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Performance and power consumption optimization of a hydraulic variable valve actuation system

Mechatronics ◽

10.1016/j.mechatronics.2020.102479 ◽

2021 ◽

Vol 73 ◽

pp. 102479

Author(s):

Junjie Pan ◽

Amir Khajepour ◽

Yangtao Li ◽

Jing Yang ◽

Weiqiang Liu

Keyword(s):

Power Consumption ◽

Variable Valve Actuation ◽

Actuation System ◽

Power Consumption Optimization ◽

Variable Valve ◽

Valve Actuation

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OS-A4: A Study of a Variable Compression Ratio and Variable Valve Actuation System for Improving Fuel Economy(OS-A High Efficiency and Low Emission Engine by Variable Mechanism,Organized Session Papers)

The Proceedings of the International symposium on diagnostics and modeling of combustion in internal combustion engines ◽

10.1299/jmsesdm.2008.7.49 ◽

2008 ◽

Vol 2008.7 (0) ◽

pp. 49-56

Author(s):

Hirofumi Tsuchida ◽

Masayuki Tomita ◽

Shunichi Aoyama ◽

Shinichi Takemura ◽

Koji Hiraya ◽

...

Keyword(s):

Compression Ratio ◽

Fuel Economy ◽

High Efficiency ◽

Variable Compression Ratio ◽

Variable Valve Actuation ◽

Actuation System ◽

Low Emission ◽

Variable Valve ◽

Variable Compression ◽

Valve Actuation

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A numerical procedure for the calibration of a turbocharged spark-ignition variable valve actuation engine at part load

International Journal of Engine Research ◽

10.1177/1468087416674653 ◽

2016 ◽

Vol 18 (8) ◽

pp. 810-823 ◽

Cited By ~ 17

Author(s):

Fabio Bozza ◽

Vincenzo De Bellis ◽

Luigi Teodosio

Keyword(s):

Fuel Consumption ◽

Spark Ignition ◽

Specific Fuel Consumption ◽

Brake Specific Fuel Consumption ◽

Valve Closure ◽

Intake Valve ◽

Part Load ◽

Variable Valve Actuation ◽

Variable Valve ◽

Valve Actuation

Referring to spark-ignition engines, the downsizing, coupled to turbocharging and variable valve actuation systems are very common solutions to reduce the brake-specific fuel consumption at low-medium brake mean effective pressure. However, the adoption of such solutions increases the complexity of engine control and management because of the additional degrees of freedom, and hence results in a longer calibration time and higher experimental efforts. In this work, a twin-cylinder turbocharged variable valve actuation spark-ignition engine is numerically investigated by a one-dimensional model (GT-Power™). The considered engine is equipped with a fully flexible variable valve actuation system, realizing both a common full-lift strategy and a more advanced early intake valve closure strategy. Refined sub-models are used to describe turbulence and combustion processes. In the first stage, one-dimensional engine model is validated against the experimental data at full and part load. The validated model is then integrated in a multipurpose commercial optimizer (modeFRONTIER™) with the aim to identify the engine calibration that minimizes brake-specific fuel consumption at part load. In particular, the decision parameters of the optimization process are the early intake valve closure angle, the throttle valve opening, the turbocharger setting and the spark timing. Proper constraints are posed for intake pressure in order to limit the gas-dynamic noise radiated at the intake mouth. The adopted optimization approach shows the capability to reproduce with good accuracy the experimentally identified calibration. The latter corresponds to the numerically derived Pareto frontier in brake mean effective pressure–brake specific fuel consumption plane. The optimization also underlines the advantages of an engine calibration based on a combination of early intake valve closure strategy and intake throttling rather than a purely throttle-based calibration. The developed automatic procedure allows for a ‘virtual’ calibration of the considered engine on completely theoretical basis and proves to be very helpful in reducing the experimental costs and the engine time-to-market.

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