Variable Valve-Timing Unit Suitable for Internal Combustion Engines

1972 ◽  
Vol 186 (1) ◽  
pp. 301-306 ◽  
Author(s):  
G. E. Roe
Keyword(s):  
Internal Combustion Engines ◽  
Engine Speed ◽  
Valve Lift ◽  
Specific Power ◽  
Combustion Engines ◽  
Valve Timing ◽  
Specific Power Output ◽  
Torque Curve ◽  
Lift Curve ◽  
Variable Valve

As the specific power output of I.C. engines is increased, the range of engine speed over which useful torque is available is reduced. This ‘power band’ can be widened by having automatically varying valve timing, with the timing being a function of engine speed and/or load. A prototype cyclic phasing unit has been tested which successfully varies the timing of a poppet valve with opening, closing points, and the form of valve lift curve being readily varied independently. The unit is simple mechanically, but ideally one unit is needed for each valve, so principal application is likely to be on engines with a small number of cylinders. In addition to flattening the torque curve, such a unit is likely to give improved fuel consumption and lower exhaust emissions, particularly hydrocarbons.

scholarly journals Computational studies of the influence of variable valve timing on the performance of a gas engine with Miller’s thermodynamic cycle

2021 ◽  
Vol 2061 (1) ◽  
pp. 012066
Author(s):  
K V Milov
Keyword(s):  
Internal Combustion Engines ◽  
Computer Modelling ◽  
Thermodynamic Cycle ◽  
Valve Lift ◽  
Variable Valve Timing ◽  
Miller Cycle ◽  
Valve Timing ◽  
Gas Engine ◽  
Lift Height ◽  
Variable Valve

Abstract Current development trends in the field of internal combustion engines aim at regulating all processes of the engine and individual units. A converted diesel to gas engine with Miller thermodynamic cycle is more energy efficient at partial loads than a gas engine with Otto thermodynamic cycle. The Miller cycle engine with variable valve timing and valve lift has been investigated to improve performance and energy efficiency across the load range. The aim of the work is to study the influence of the displacement of the valve timing phases of the intake and exhaust camshafts and the valve lift height on the performance of the gas engine with the Miller cycle. Computer modelling was based on data obtained from the full-scale experiment on the gas engine with the Miller thermodynamic cycle.

scholarly journals Miller Cycle Analysis Using EGM

2005 ◽  
Author(s):  
Bernardo Ribeiro ◽  
Jorge Martins
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Compression Ratio ◽  
Internal Combustion Engines ◽  
Combustion Engines ◽  
Miller Cycle ◽  
Valve Timing ◽  
Entropy Generation Minimization ◽  
Flow And Heat Transfer ◽  
Variable Valve

The Entropy Generation Minimization (EGM) method is based on the analysis by three sciences (thermodynamics, fluid flow and heat transfer) of the different processes that may occur in a system or in an equipment. Herein the EGM method is applied to internal combustion engines to determine the entropy generation caused by different processes. A model incorporating entropy generation calculations is used to assess various engines configurations. Otto cycle was tested and Variable Valve Timing (VVT) and Variable Compression Ratio (VCR) were applied so thermodynamic benefits could be tested and evaluated. With the referred model, the Miller cycle variables are analyzed in order to establish the best working conditions of an engine under a certain load. The intake and exhaust valve timing, combustion start, compression ratio adjustment and heat transfer are the variables for which a best working condition is determined based on the minimization of the entropy generation of the several engine processes.

Effects of Supercharging, EGR and Variable Valve Timing on Power and Emissions of Hydrogen Internal Combustion Engines

2008 ◽  
Vol 1 (1) ◽  
pp. 647-656 ◽  
Author(s):  
Sebastian Verhelst ◽  
Jannick De Landtsheere ◽  
Frederik De Smet ◽  
Christophe Billiouw ◽  
Arne Trenson ◽  
...  
Keyword(s):  
Internal Combustion Engines ◽  
Internal Combustion ◽  
Variable Valve Timing ◽  
Combustion Engines ◽  
Valve Timing ◽  
Variable Valve

NOx and Fuel Economy Challenges With EMD Two-Stroke Engines: Variable Injection and Valve Timing

2009 ◽  
Author(s):  
Michael B. Riley ◽  
John C. Hedrick
Keyword(s):  
Fuel Economy ◽  
Simulation Modeling ◽  
Internal Combustion Engines ◽  
Nox Reduction ◽  
Injection Timing ◽  
Combustion Engines ◽  
Valve Timing ◽  
Start Of Injection ◽  
Variable Valve ◽  
The Impact

NOx emissions are a major cause of ozone formation. Several technologies to mitigate NOx in internal combustion engines have been developed, both in-cylinder and aftertreatment. Some of these newer technologies are being implemented on new engines, but older engines, especially large diesel engines, have few options to reduce these emissions substantially. The most common method of NOx reduction is retarding the start of injection timing but this has a penalty in fuel economy. A program has been undertaken on an EMD 645E two-stroke diesel engine to combine a simple mechanical system with both retarded and variable start of injection — to mitigate NOx — with variable valve timing to offset the fuel economy penalty. Simulation modeling and on-engine experimentation have been carried out to quantify the extent of the NOx reduction with the impact on fuel economy.

Variable Valve Timing (VVT) Modelling by Lotus Engine Simulation Software

2021 ◽  
Vol 17 (4) ◽  
Author(s):  
Mohammed Kadhim Allawi ◽  
Mohanad Kadhim Mejbel ◽  
Mahmood Hasan Oudah
Keyword(s):  
Fuel Consumption ◽  
Internal Combustion Engines ◽  
Simulation Software ◽  
Valve Lift ◽  
Variable Valve Timing ◽  
Valve Timing ◽  
Engine Simulation ◽  
Engineering Software ◽  
And Performance ◽  
Variable Valve

Variable valve timing (VVT) is an advanced modern technique applied in internal combustion engines by altering the valve lift event timing. This work aims to contribute to the continuing industrial VVT development to improve engine efficiency, fuel consumption and performance. To observe the influence on the spark-ignition (SI) engine’s performance, four valve timing strategies are selected carefully by varying the intake and exhaust valve timing. Lotus Engine Simulation, a simulation engineering software, is adapted in this study. The engine characteristics used in this modelling are spark engine, multicylinder, four strokes, port injection fuel system and constant compression ratio. A comparison between a conventional standard exhaust/intake valve timing and three other different timing cases is carried out. Results reveal that the overlap case of 98° showed a good brake-specific fuel consumption by approximately 3% less than the conventional case. An improvement of 6.2% for volume efficiency and 2.9% in brake thermal efficiency is also reported.

Improvement in CAM Shaft Design: An Experimental Application and Recommendation

2015 ◽  
Vol 789-790 ◽  
pp. 251-256
Author(s):  
M.S. Al-Khaldi ◽  
Mohd K.A. Ariffin ◽  
Shamsuddin Sulaiman ◽  
B.T.H. Bahrudind ◽  
N.A. Aziz
Keyword(s):  
Hydraulic System ◽  
Internal Combustion Engines ◽  
Engine Speed ◽  
Combustion Engines ◽  
Power Performance ◽  
Peak Point ◽  
Model Predictions ◽  
Torque Curve ◽  
Cam Profile ◽  
Valve Opening

A new design of CAM shaft has been investigated for Campro engine 3.0L V4 engine. The new design adds a modification to Cam profile peak point in the Camshaft to be controllable at different speeds through a hydraulic system. The new design was simulated in CFD for tolerating stresses. The new design promotes Cams to give the exact heights at different engine speed depending on the optimize value valve opening time. At the same time this paper discusses the prediction of power performance of internal combustion engines with the new design. The expected result will significantly improve the engine speed-torque curve, reduce emission gases, and reduce fuel consumption. The new design model predictions need to be tested experimentally for further improvement in the hydraulic system before the commercial use.

scholarly journals Practical Aspects of Cylinder Deactivation and Reactivation

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2540
Author(s):  
Norbert Zsiga ◽  
Johannes Ritzmann ◽  
Patrik Soltic
Keyword(s):  
Internal Combustion Engines ◽  
Engine Speed ◽  
Initial Conditions ◽  
Torque Ripple ◽  
Combustion Engines ◽  
Mode Transition ◽  
Valve Timing ◽  
Effective Measure ◽  
Cylinder Deactivation ◽  
Exhaust Valves

Cylinder deactivation is an effective measure to reduce the fuel consumption of internal combustion engines. This paper deals with several practical aspects of switching from conventional operation to operation with deactivated cylinders, i.e., gas spring operation with closed intake and exhaust valves. The focus of this paper lies on one particular quantity-controlled stoichiometrically-operated engine where the load is controlled using the valve timing. Nevertheless, the main results are transferable to other engines and engine types, including quality-controlled engines. The first aspect of this paper is an analysis of the transition from fired to gas spring operation, and vice versa, as well as the gas spring operation itself. This is essential for mode changes, such as cylinder deactivation or skip-firing operation. Simulation results show that optimizing the valve timing in the last cycle before deactivating/first cycle after reactivating a cylinder, respectively, is advantageous. We further show that steady-state gas spring operation is reached after approximately 6 s regardless of the initial conditions and the engine speed. The second aspect of this paper experimentally verifies the advantage of optimized valve timings. Furthermore, we show measurements that demonstrate the occurrence of an unavoidable torque ripple, especially when the transition to and from the deactivated cylinder operation is performed too quickly. We also confirm with our experiments that a more gradual mode transition reduces the torque drop.

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