Variable valve timing (VVT)

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Design And Timing Analysis Of Variable Valve Timing (VVT) For Internal Combustion Engine

Design And Timing Analysis Of Variable Valve Timing (VVT) For Internal Combustion Engine

Variable valve timing (VVT) is a generic term for an automobile piston engine technology. VVT allows the lift or duration or timing of the intake or exhaust valves to be changed while the engine is in operation. Two-stroke engines use a power valve system to get similar results to VVT.

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Variable Valve Timing Scheduling in a 4-Stroke Internal Combustion Cylinder Utilizing Artificial Neural Networks

Variable Valve Timing Scheduling in a 4-Stroke Internal Combustion Cylinder Utilizing Artificial Neural Networks

In order to resolve these issues, a fully-flexi- ble valve actuation system is required to continu- ously vary the valve opening and closing times according to the crank angle. Such a design could maintain the optimum timing at all spins. A num- ber of variable valve timing systems which have already been introduced or are under develop- ment, are mentioned in a paper by Carrie M. Hall [5]. Earlier systems discussed in S. M. Rabia’s pa- per [18] rely only on discrete steps applied to the proportion between the crankshaft and camshaft, but such a design cannot be completely effective because a shift in one will have an effect on the other events. For instance, if the IVC lags by 10°, the IVO, EVC and EVO will also experience a delay. The current study does not discuss ways of devising variable valve timing (VVT) systems, but studies the effect of fully-variable VVT on cylinder output to find a way to supervise those events with a trained prediction matrix.

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The Effects of a Pneumatic-Driven Variable Valve Timing Mechanism on the Performance of an Otto Engine

The Effects of a Pneumatic-Driven Variable Valve Timing Mechanism on the Performance of an Otto Engine

engine speed and engine load status. Camshaft profiles are used in order to change the opening levels of valves. Mechanical, electrical, hydraulic, pneumatic, and other energy sources are used to engage and disengage different cam profiles. Usually, next to a central cam profile, there are other cam profiles that engage and disengage with the help of a feeder needle. The Honda variable valve timing and lift electronic control system (VTEC) is the first system in the world that can simultaneously switch the timing and lift of the intake and exhaust valves. This system has made improvements in the maximum output at high rpm and also improved the low rpm range, with regards to idling stability and starting capability [8]. The customization of valve lifts and open/close advances according to engine speeds increase engine efficiency [9]. With a two-graded Variable Valve Actuation system, which is lower than the regular profile of camshaft, a 6.9 % decrease in fuel consumption can be achieved in dynamometer tests [10]. In such systems, which perform gradual variable valve timing and valve lift alteration, engine efficiency is optimum at several engine speeds instead of a single speed. Although it seems like a disadvantage, the low number of parts and low level of friction forces make these systems more utilizable.

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internal combustion engines, overlap angles, performance, variable valve timing

internal combustion engines, overlap angles, performance, variable valve timing

emissions means improving the engine thermal efficiency [2].This target can be met following different routes, each of them could be an effective way with different cost-to-benefit ratio. Often, it could be observed, it is helpful to adopt numerous solutions contemporaneously. As an example, fast combustion, lean burn, variable valve timing and actuation, gasoline direct injection and so long may be reminded. During most of its average life, a road engine is run under low load and low speed conditions. It is known that load reduction in spark-ignition engines is traditionally realized by introducing additional losses during the intake stroke by means of a throttle valve. In these operating points, the engine efficiency decreases from the peak values (already not very high) to values dramatically lower. The optimization of intake and exhaust valve timing can provide significant reductions in pumping losses at part load operation [3–5]. A number of papers have been sighted by [6].

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Gear Drive Mechanism for Continuous Variable Valve Timing of IC Engines

Gear Drive Mechanism for Continuous Variable Valve Timing of IC Engines

In internal combustion engines, variable valve timing (VVT), also known as variable valve actuation (VVA), is a generalized term used to describe any mechanism or method that can alter the shape or timing of a valve lift event within an internal combustion engine [1-6]. The (VVT) system allows the lift, duration or timing (in vari- ous combinations) of the intake and/or exhaust valves to be changed while the engine is in operation, which have a significant impact on engine performance and emissions. In a standard engine, the valve events are fixed, so per- formance at different loads and speeds is always a com- promise between drivability (power and torque), fuel economy and emissions. An engine equipped with a variable valve actuation system is freed from this con- straint, allowing performance to be improved over the engine operating range [7-10].

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Engine optimization by using variable valve timing system at low engine 
		revolution

Engine optimization by using variable valve timing system at low engine revolution

Engine optimization is one of the most cost-effective methods in reducing emissions and fuel consumption. In the theory, the maximum overlap would be needed between the intake valves and the exhaust valves opening whenever a common internal-combustion engine is running at high revolution per minute (RPM). At lower RPM, however, as the engine is run at lighter load, maximum overlaps may be useful as a means to lessen the fuel consumptions and emissions. The timing of air intake and exhaust valves are usually determined by the shapes and the phase angles of the camshaft. To optimize the air breathing, an engine would require different valve timings at different speeds. As the revolution speed increases, the duration of the intake and exhaust valves opening would decrease, thus less amount of fresh air may enter the combustion chambers, while complete exhaust gas cannot exit the combustion chamber in time. Therefore, varying the intake timing of an engine could help to produce more power and, if applied to smaller and lighter engine, it could result in a lower fuel consumption as well. This particular investigation has been conducted through simulations and complemented by experimental works. It has been realized in this study that optimization of an engine together with implementation of variable valve timing was able to generate similar power with an increase in volumetric efficiency, while it is obtained with a slightly lower fuel consumption. As reported by many researchers, the variable valve timing method has been indeed proven to deliver better fuel economy, less emissions, but higher torque under any operating condition.

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Investigating the Effects of Variable Valve Timing on Spark Ignition Engine Performance

Investigating the Effects of Variable Valve Timing on Spark Ignition Engine Performance

11%. Although late EVO (LEVO) decreases the exhaust gas pressure and requires work for pump- ing out, Hara [9] found that it could improve volumetric efficiency if the exhaust gas is fully pumped out by the piston because no residual gas will remain inside. Kang [12] equipped a diesel engine with a pneumatic inlet valve controller which acts using a nonlinear mean value model under wide-gap dynamic conditions and the re- sults show some improvement. Benson [3] dem- onstrated that a 4-cylinder 4-stroke diesel engine can benefit from LIVC with regard to fuel sav- ings, volumetric efficiency and residual gas dis- charge. Similarly, Saunders [17] showed that an overall VVT approach can improve fuel economy in diesel engines. Fiorenza [6] concluded that a continuous VVT can increase the output torque. Caufield [4] reported that VVT can decrease the fuel consumption in small spark-ignition (SI) engines through accurate fluid path simulations. The VVT was shown to be of even greater ben- efit for auto ignition diesel engines by Cao [13], who discussed its effect on gas composition and combination. Ghazal and Borowski investi- gated the effect of different water mass flow rates and air/fuel ratio on the SI engine emissions and performance as well [8].

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A NEW APPROACH FOR VARIABLE VALVE ACTUATION (VVA) MECHANISM TO ENHANCE ENGINE PERFORMANCE.

A NEW APPROACH FOR VARIABLE VALVE ACTUATION (VVA) MECHANISM TO ENHANCE ENGINE PERFORMANCE.

Automotive electrical systems today are moving towards higher power requirements. The introduction of this standard, coupled with recent advances in power electronics, sensors and microprocessors, has led to several innovations in automotive systems. Many of these innovations significantly increase fuel economy, and some involve the replacement of automotive mechanical systems with electrical systems. Of particular relevance, the new voltage standard has made the electrification of internal combustion (IC) engine valves a technically and economically viable innovation. In conventional IC engines, engine valve displacements are fixed relative to the crankshaft position. The valves are actuated with cams that are located on a belt-driven camshaft, and the shape of these cams is determined by considering a trade-off between engine speed, power, and torque requirements, as well as vehicle fuel consumption. This optimization results in an engine that is highly efficient only at certain operating conditions. Instead, if the engine valves are actuated as a variable function of crankshaft angle, significant improvements in fuel economy up to 21% can be achieved. In addition, improvements in torque, output power and emissions are achieved. Internal combustion engines in which both the duration (how long each valve is opened or closed) and the phase (how each valve profile is shifted with respect to some nominal valve profile) of the valves can be controlled are said to have variable valve timing (VVT). VVT can be achieved using fluidic system with electromagnetic actuation systems. In this paper, the focus is on an electromagnetic actuation system. With VVT alone, a 21% improvement in fuel economy can be achieved. Further more, if the lift (how much each valve is opened) of the valves is controlled, another 21% improvement

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Comparison the Sensitivity Analysis and Conjugate Gradient algorithms for Optimization of Opening and Closing Angles of Valves to Reduce Fuel Consumption in XU7/L3 Engine

Comparison the Sensitivity Analysis and Conjugate Gradient algorithms for Optimization of Opening and Closing Angles of Valves to Reduce Fuel Consumption in XU7/L3 Engine

Bin Wu and his colleagues presented optimization valve timing using neural network algorithm. The reason noted for using from this algorithm in this study is was to reduce the time in reaching the optimal point. The engine being used in this study is a gasoline engine with two camshaft having variable valve system and variable valve timing system which have been employed by changing camshaft phase. The result of this study is to reach optimal timing by using neural network in variable valve system engine. Therefore a mathematical model of target engine has been made, then the model was validated by using experimental information and also the constants and performance zone of engine have been realized. To realize these constants in the working zone of engine neural network algorithm have been used. Then to maximize output torque, timing of valves is changed and the best timing in each speed in full throttle condition using neural algorithm is determined. Independent variables in this study are intake and exhaust valve timing, spark timing and air-fuel ratio.

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Modelling And Simulation Of Cylinder Deactivation System Applied To Passenger Vehicles

Modelling And Simulation Of Cylinder Deactivation System Applied To Passenger Vehicles

In an internal combustion engine, the flow of the intake and exhaust gasses into and out of the cylinders respectively are controlled with the used of valves. The lift, timing, and duration of these valves events will have implication on the output performance of the engine. If an engine does not use variable valve timing, the valve timing will be equal for all the engine speed and conditions, thus certain compromises are necessary. [4] An engine that is equipped with this system however is free from this constraint which allows the performance to become better with the engine operating range. The valves are usually actuated by camshafts where the cam lifts the valve open for a certain period of time throughout intake and exhaust stroke. The timing of the valves for opening and closing is also essential as the camshaft is driven by the crankshaft through chains, gear, or timing belts.

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Numerical Study of a Spark Assisted Compression Ignition (SACI) Engine Using the One-Dimensional Turbulence (ODT) Model.

Numerical Study of a Spark Assisted Compression Ignition (SACI) Engine Using the One-Dimensional Turbulence (ODT) Model.

6 kernel growth (EKG) stage. However, due to limitations in diagnostic methods, the effect of the spark plasma in this stage could not be measured. This limitation was overcome in the study conducted by Natarajan and Reuss, [9], and the first conclusion of the previous study was confirmed. However, it was found that the spark ignition system did not affect the EKG cyclic variations, but the charge composition distribution did. Pastor et al. [10], combined direct visual diagnostic methods and spectroscopic analysis of natural radiation, with analysis of Rate of Heat Release, to validate the works of Reuss [8,9]. The spectral analysis of the combustion reaction radicals was used to study the progress of the combustion process and identify the transition of the SACI stages. A similar research was conducted by Benajes et al. [11], for a gasoline partially premixed spark assisted compression ignition engine at low load to better observe the combustion process. It was found that, apart from spark assistance and ignition timing, the fuel injection timing and duration had an important role in improving combustion stability, cyclic stability and combustion phase duration. The author continued this work in [12] to show the effect on emissions due to single and double direct fuel injection strategies, and by varying the fuel fraction in the double injection case. It was concluded that air/fuel mixture distribution was improved using double injection strategy and increased the fuel energy conversion efficiency.

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Heart valve closure timing intervals in response to left ventricular blood pressure

Heart valve closure timing intervals in response to left ventricular blood pressure

nonlinear model of any part of an artery or vein generally consists of three elements: resistance, modeled by a re- sistor; compliance, modeled by a capacitor; and inertia, modeled by an inductor. The circulatory system is thus converted to an analog circuit, as shown in Figure 1. The values of the resistors, capacitors, and inductors are given in Appendix A. The heart cycle period is deter- mined physiologically by the vagal-sympathetic mecha- nism. With the support of this cardiopulmonary platform, heart valve closure timing can be defined by the differen- tial blood pressure (BP) across the valves.

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Engine management system for dynamometer testing.

Engine management system for dynamometer testing.

In modern engine control strategies utilizing electronic throttle actuation, all actuator functions can be based on a central engine torque requirement. This consists of driver torque demand, accessory loading, idle speed control, traction control, and vehicle speed control. In order to fulfill this torque requirement, actions such as modifying ignition timing, camshaft phasing, fuelling or throttle opening may be taken. This leads to reduced calibration effort when component changes are made, enables a number of fuel saving and emission reduction schemes, and facilitates traction control by limiting engine torque.

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Design and Development of Pneumatic Cutting Machine

Design and Development of Pneumatic Cutting Machine

________________________________________________________________________________________________________ Abstract – The pipe cutting process is a main part of all industries. Normally the pipe cutting machine is manually hand operated one for medium and small scale industries. Automation in the modern world is in inevitable. Any automatic machine aim at the economical use of man, machine, and material worth the most. In our project is solenoid valve and control timing unit is used for automation .The pipe cutting machine works with the help of pneumatic double acting single cylinder .The piston is connected to the moving cutting tool .It is used to cut the small size of the pipe. The machine is portable in size, so easy transportable. A compress air from compressor is used as force medium for this operation. There are pneumatic double acting cylinders, solenoid valve, flow control valve and timer unit is used. The arm from the compressor enters to the flow of control valve. The control air from the flow control valve enters to the solenoid valve. The function of solenoid valves all of air correct time interval. The 5/2 solenoid valve is used In one position air enters to the cylinder and pushes the piston so that the cutting stroke is obtained. The next position air enters to the other side of cylinder and pushes the piston return back, so that the remaining stroke is obtained .The speed of cutting releasing stroke is varying by the timer control unit circuit.

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MATHEMATICAL MODELING AND STRESS ANALYSIS OF VALVE GEAR TRAIN OF DIESEL ENGINE AT VARIABLE VALVE LIFT

MATHEMATICAL MODELING AND STRESS ANALYSIS OF VALVE GEAR TRAIN OF DIESEL ENGINE AT VARIABLE VALVE LIFT

The design of diesel engine valve gear train is so intricate, leading to many problems while analyzing the contact forces. For cam materials, the usual permissible Hertzian pressure is between 850 to 1000 MPa. In this paper, obtained Hertz pressures are below the permissible limit. Exhaust cam had higher stress than inlet cam. Hence at the exhaust cam side, Hertz pressure shall be minimized by modifying the cam profile or a higher surface hardness may be used.

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A comparison of wear behaviour of heat resistant steel engine valves and TiAl engine valves

A comparison of wear behaviour of heat resistant steel engine valves and TiAl engine valves

The increasingly demand for higher performance internal combustion engines (ICEs) has led to higher temperatures in the combustion chamber. As a result, TiAl valves have been investigated with a view to their use in a natural gas fuelled diesel ICE, taking advantage of their low density and good high temperature resistance. In this work, comparison bench tests for traditional steel valves and TiAl valves were carried out through the use of specially designed wear testing apparatus. Compared to the traditional valves made from heat resistant steel (X60, X85), the TiAl valves have 50 % lower mass, leading to a decrease in the impact seating forces during the engine operation. With the reduction of the inertia of engine valve movement, the dynamic characteristics of the engine valve train system can be optimized. Each contact pair of valve and seat insert was tested for 3 million impact cycles. Compared to the austenitic exhaust valves (X60) tested at 700 °C, the TiAl valve had better wear resistance and the wear loss decreased by 24.8 %. The predominant wear mechanism is considered to be a combination of oxidative wear

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Design of High throughput adaptive filter using aging aware Reliable Multiplier

Design of High throughput adaptive filter using aging aware Reliable Multiplier

In this situation, the extra re-execution cycles caused by timing violation incurs a penalty to overall average latency. However, our proposed AHL circuit can accurately predict whether the input patterns require one or two cycles in most cases.Only a few input patterns may cause a timing variation when the AHL circuit judges incorrectly. In this case, the extra re- execution cycles did not produce significant timing degradation.

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Design and Optimization of 2-stage Variable Valve Actuation
Mechanism for Diesel Engines

Design and Optimization of 2-stage Variable Valve Actuation Mechanism for Diesel Engines

The reserves of diesel and gasoline fuels are ever decreasing, which plays an important role in the technological development of automobiles. The demands on combustion engines continue to grow. On one hand, customers want more power and torque; while on the other hand, one cannot lose sight of fuel economy and increasingly stringent emissions laws. Another important area in engine research is the implementation of new technologies like Variable Valve Timing (VVT), Variable Compression Ratio (VCR), Variable Intake System, Variable Geometry Compressor, and Exhaust Gas Recirculation (EGR), to improve engine performance by enhancing Combustion efficiency. The multiplicity of types of VVA systems [1][4][5] and their functions in internal combustion engines is well documented. This is particularly so for gasoline engines, with phasing system finding widespread applications [4]. The applications and benefits of these systems are well known and have been thoroughly investigated

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Computational Geometric Modeling and Finite Element Structural Analysis of Automobile Camshaft

Computational Geometric Modeling and Finite Element Structural Analysis of Automobile Camshaft

Abstract— This Cam is a Mechanical Linkage used especially in transforming rotary motion into linear motion.Its main function is to control the valve timing in I.C Engines.In the present work we are designed Automobile camshaft by Numerical Calculations there after it is Designed by using Modelling software CATIA and CAE(Structural) Analysis is carried out in ANSYS-WORKBENCH by varying three different materials Castiron, Carbon steel and ALMMC to investigate which material will give best performance for camshaft.

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Design, Fabrication And Partial-Analysis Of A 2-Wheeler Prototype That Runs On Compressed Air

Design, Fabrication And Partial-Analysis Of A 2-Wheeler Prototype That Runs On Compressed Air

Abstract: The primary objective of the project is to create a prototype of a purely air powered motorcycle by retrofitting its internal combustion engine to run on compressed air. Firstly, the conventional spark plug was replaced with a solenoid valve. The solenoid valve was initially actuated using a reed switch and magnet duo, but then later replaced with an optical crank position sensor circuit due to reasons that include lack of control over the amount of air injected during each stroke and also for more precise control over the opening and closing of the valve. The torque, brake power, indicated power, air consumption rate of the engine under load are calculated. Separate mounts for the modified engine and the cylindrical storage unit are designed and analysed using Catia v4. Also, possible ways of future scope of the prototype are mentioned.

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