Unthrottled Engine Operation with Variable Intake Valve Lift, Duration, and Timing

2007 ◽  
Author(s):  
David Cleary ◽  
Gerald Silvas
Keyword(s):  
Valve Lift ◽  
Intake Valve ◽  
Engine Operation

Experimental research on pumping losses and combustion performance in an unthrottled spark ignition engine

2018 ◽  
Vol 232 (7) ◽  
pp. 888-897 ◽  
Author(s):  
Tingting Sun ◽  
Yingjie Chang ◽  
Zongfa Xie ◽  
Kaiyu Zhang ◽  
Fei Chen ◽  
...  
Keyword(s):  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Valve Lift ◽  
Combustion Characteristic ◽  
Spark Ignition Engines ◽  
Intake Valve ◽  
Valve System ◽  
Combustion Performance ◽  
Intake Swirl ◽  
Variable Valve

A novel fully hydraulic variable valve system is described in this paper, which achieves continuous variations in maximum valve lift, valve opening duration, and the timing of valve closing. The load of the unthrottled spark ignition engine with fully hydraulic variable valve system is controlled by using an early intake valve closing rather than the conventional throttle valve. The experiments were carried out on BJ486EQ spark ignition engine with fully hydraulic variable valve system. Pumping losses of the throttled and unthrottled spark ignition engines at low-to-medium loads are compared and the reason of it decreasing significantly in the unthrottled spark igntion engine is analyzed. The combustion characteristic parameters, such as cyclic variation, CA50, and heat release rate, were analyzed. The primary reasons for the lower combustion rate in the unthrottled spark ignition engines are discussed. In order to improve the evaporation of fuel and mix with air in an unthrottled spark ignition engine, the in-cylinder swirl is organized with a helical intake valve, which can generate a strong intake swirl at low intake valve lifts. The effects of the intake swirl on combustion performance are investigated. Compared with the throttled spark ignition engine, the brake specific fuel consumption of the improved unthrottled spark ignition engine is reduced by 4.1% to 11.2%.

Design and Dynamic Analysis of an Innovative Axial Shift Valvetrain System (ASVS) for Variable Stroke Engine

2021 ◽  
pp. 146808742110653
Author(s):  
Jingchen Cui ◽  
Liping Chen ◽  
Wuqiang Long ◽  
Xiangyu Meng ◽  
Bo Li ◽  
...  
Keyword(s):  
Contact Force ◽  
Engine Speed ◽  
Exhaust Valve ◽  
Valve Lift ◽  
Intake Valve ◽  
Power Performance ◽  
Working Cycle ◽  
Valve Motion ◽  
Axial Shift ◽  
Stroke Engine

A variable valvetrain system is the key part of the variable stroke engine (VSE), which could achieve higher power performance and low-speed torque. An innovative axial shift valvetrain system (ASVS) was put forward to meet the air-charging requirements of a 2/4-stroke engine and complete a changeover within one working cycle. Two sets of intake and exhaust cam profiles for both intake and exhaust sides in the 2/4-stoke mode were designed for 2/4-stoke modes. Furthermore, a simulation model based on ADAMS was established to evaluate the dynamic valve motion and the contact force at different engine speeds. The dynamic simulation results show that the valve motion characteristics meet the challenges at the target engine speed of 3000 r/min. In two-stroke mode, the maximum intake valve lift could achieve 7.3 mm within 78°CaA, and the maximum exhaust valve lift could achieve 7.5 within 82°CaA on the exhaust side. In four-stroke mode, the maximum intake valve lift can achieve 8.8 mm within 140°CaA, and the maximum exhaust valve lift can achieve 8.4 mm within 140°CaA. The valve seating speeds are less than 0.3 m/s in both modes, and the fullness coefficients are more than 0.5 and 0.6 in the 2-stroke and 4-stroke mode, respectively. At the engine speed of 3000 r/min, the contact force on each component is acceptable, and the stress between cam and roller can meet the material requirement.

Some aspects concerning the combination of downsizing with turbocharging, variable compression ratio, and variable intake valve lift

2007 ◽  
Vol 221 (10) ◽  
pp. 1287-1294 ◽  
Author(s):  
A C Clenci ◽  
G Descombes ◽  
P Podevin ◽  
V Hara
Keyword(s):  
Compression Ratio ◽  
Gasoline Engine ◽  
Control Method ◽  
Operation Time ◽  
Spark Ignition Engine ◽  
Valve Lift ◽  
Boost Pressure ◽  
Intake Valve ◽  
Variable Compression Ratio ◽  
Variable Compression

The inefficient running of the spark ignition engine at part loads due to the load control method but, mostly, their major weighting in the vehicle's operation time justifies the interest in the technical solutions, which act in this particular operating range. These drawbacks encountered at low part loads are even more amplified when considering larger engines. For instance, it is well known that, at the same engine load, a larger engine is more throttled than a smaller engine; therefore the concerns are the higher pumping work, the lower real compression ratio, and the overall mechanical efficiency, which is also lower. One solution is a reduction in the displacement without affecting the power output. This is what is now commonly known as the downsizing technique. The combination of downsizing and uploading an engine has been known for a long time. However, the conversion, in an acceptable way, of this potential to actual practice is very challenging. On the one hand, the degree of the downsizing is related to the boost pressure. In order to cope with the knocking phenomenon, the downsized high-pressure turbocharged gasoline engine requires a lower volumetric compression ratio that limits the efficiency on part loads. Therefore, the degree of the downsizing has been limited and, thus, the possible fuel consumption reduction has not yet been fully achieved. On the other hand, other problems are encountered when considering a downsized turbocharged gasoline engine: insufficient low-end torque, poor starting performance, and turbo lag. In order to solve these problems an effective combination of the downsized turbocharged gasoline engine with additional technologies is needed. Thus, the paper will present a so-called adaptive thermal engine, which has at the same time a variable compression ratio and a variable intake valve lift. It will then be demonstrated that it is highly suitable for turbocharging, thus resulting in a high downsizing factor.

scholarly journals Influence of asymmetric valve strategy on large-scale and turbulent in-cylinder flows

2017 ◽  
Vol 19 (6) ◽  
pp. 631-642 ◽  
Author(s):  
Daniel Butcher ◽  
Adrian Spencer ◽  
Rui Chen
Keyword(s):  
Large Scale ◽  
Vortex Pair ◽  
Velocity Fields ◽  
Valve Lift ◽  
Intake Valve ◽  
Single Vortex ◽  
Cyclic Variability ◽  
Stochastic Fluctuations ◽  
Particle Imaging ◽  
The Impact

Phase-locked particle imaging velocimetry measurements are carried out in a direct-injected spark-ignition single-cylinder optical research engine equipped with fully variable valve timing to assess the impact of asymmetric intake valve lift strategies on the in-cylinder flow. The engine was operated under a range of asymmetric strategies, with one valve following a full lift profile, while the second intake valve is scaled as a factor of the first, expressed as % maximum valve lift. Proper orthogonal decomposition combined with a proposed methodology allows instantaneous velocity fields to be decomposed into what are nominally demonstrated as coherent and turbulent constituent velocity fields. Analysis of the coherent fields reveals the behaviour of large-scale structures within the flow, subject to cyclic variation. In the case of 40% maximum valve lift, an increase in the flow cyclic variability is observed. This is found to be as a result of a switch between a flow dominated by a counter-rotating vortex pair and a single vortex. The impact of maximum valve lift on the bulk motion is further evident by an increase in the magnitude of swirl ratio from 0.5 to −6.0 (at 75°CA). Analysis of the turbulent constituent shows how the increased valve life asymmetry leads to increased turbulence during the intake stroke by over 250%. Finally, it is shown how the ensemble turbulence statistics may be misleading as stochastic fluctuations were found to be typically 66% of the total turbulent kinetic energy calculated from the ensemble statistic in the tested conditions.

Analytical synthesis and computer-aided kinematic analysis of a continuously variable valve lift mechanism

2016 ◽  
Vol 231 (2) ◽  
pp. 309-325 ◽  
Author(s):  
Adrian C Clenci ◽  
Vasile Hara ◽  
Nicolae-Doru Stănescu ◽  
Adrian Bîzîiac ◽  
Rodica Niculescu
Keyword(s):  
Kinematic Analysis ◽  
Transfer Functions ◽  
Valve Lift ◽  
Spark Ignition Engines ◽  
Intake Valve ◽  
Computer Aided ◽  
Lift Mechanism ◽  
Cam Profile ◽  
Variable Valve Lift ◽  
Analytical Synthesis

This paper presents an original continuously variable intake valve lift mechanism designed for the automotive spark ignition engines. The paper first presents the analytical kinematic synthesis of the variable intake valve lift mechanism, which consists in finding out the required intake cam profile starting from an imposed intake valve lift law. Then, by using the obtained cam profile, a computer-aided kinematic analysis of the variable intake valve lift mechanism is performed using commercial CAD software. The accuracy of the motion conversion performed with CAD software is validated by checking the degree of correlation between the resulted intake valve lift law and the imposed law used when performing the analytical synthesis. The goals of the kinematic analysis are first to find the partial laws of the intake valve lift, corresponding to the engine part loads and second, to find the transfer functions of the elements used to command the mechanism, i.e. the dependency between these elements and the intake valve lift law. The designed variable intake valve lift mechanism is successfully operated on an engine prototype and proved its energetic improvement potential.

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