The “Two-in-One” Engine - Porsche's Variable Valve System (VVS)

1998 ◽  
Author(s):  
C. Brüstle ◽  
D. Schwarzenthal
Keyword(s):  
Valve System ◽  
Variable Valve

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%.

Optimization of piston bowl and valve system in compression ignition engine fueled with gasoline/diesel/polyoxymethylene dimethyl ethers for high efficiency

2019 ◽  
pp. 146808741986538
Author(s):  
Bowen Li ◽  
Haoye Liu ◽  
Linjun Yu ◽  
Zhi Wang ◽  
Jianxin Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Efficiency ◽  
High Efficiency ◽  
Compression Ignition ◽  
Combustion Mode ◽  
Compression Ignition Engine ◽  
Valve System ◽  
Percentage Points ◽  
Polyoxymethylene Dimethyl Ethers ◽  
Variable Valve

Polyoxymethylene dimethyl ethers, with excellent volatility and oxygen content of up to 49%, have great potential to improve engine performance and emission characteristics. In this study, experiments were carried out in a single-cylinder engine fueled with gasoline/diesel/polyoxymethylene dimethyl ethers blend fuel using multiple premixed compression ignition combustion mode along with engine optimization to exploit the high-efficiency potential. The thermal efficiency was increased by 9.4 percentage points after transforming the combustion mode from conventional diesel mode to gasoline/diesel/polyoxymethylene dimethyl ethers multiple premixed compression ignition mode. A fully variable valve system and a redesigned low-heat-transfer piston were used to further improve the thermal efficiency. The low-heat-transfer piston had a 15% lower area–volume ratio compared with the original ω-type piston. By replacing the original ω-type piston with the low-heat-transfer piston, the heat transfer loss was reduced by 2.29 percentage points and thus indicated thermal efficiency could be increased by 2.37 percentage points, which was up to 50.03%. On the basis of the low-heat-transfer piston, indicated thermal efficiency could be further increased to 51.09% with the application of fully variable valve system due to the longer ignition delay and more premixed combustion. At the same time, NOX emissions could be controlled below 0.4 g/kW·h using high exhaust gas recirculation ratio, which equaled the NOX emission limit of Euro VI standard. Although soot emissions could be increased due to weak turbulence and insufficient intake charge using the low-heat-transfer piston and fully variable valve system, it was still lower than those of the original diesel engines.

A Flexible, Electronically Controlled, Hydraulically Actuating Variable Valve System for Diesel Engine

2002 ◽  
Author(s):  
Qinxue Chen ◽  
Languang Lu ◽  
Xiaojun Zhang ◽  
Kerun Cui ◽  
Guowei Zhu
Keyword(s):  
Diesel Engine ◽  
Valve System ◽  
Variable Valve

Simulation and Analysis of Variable Valve System Based on Diesel Engine

2014 ◽  
Vol 556-562 ◽  
pp. 1271-1277 ◽  
Author(s):  
Long Yin ◽  
Dong Jian Zeng ◽  
Yi Zeng Peng
Keyword(s):  
Diesel Engine ◽  
Simulation Model ◽  
Engine Speed ◽  
Drive System ◽  
Variable Valve Timing ◽  
Valve Timing ◽  
Experiment Data ◽  
Valve System ◽  
Valve Drive ◽  
Variable Valve

The necessity and superiority of using variable valve system on diesel is described detailed. The design of electro-hydraulic variable valve drive system is introduced based on DK4A diesel engine, then the mathematical simulation model of the electro-hydraulic variable valve drive system is undertook by Simulink in order to study the movement of the intake valve. The results show the design of variable valve system can achieve the variable valve timing continuous vary in different engine speed and respond quickly. Further, the simulation model of the diesel engine is built by GT-POWER, and then the accuracy of the model is verified according to the experiment data. Lastly the intake performance of the variable valve system in different out flowing phase is analyzed through the GT-POWER model. The results show that when the engine speed at 2000RPM, 2800RPM, 3600RPM, out flowing phase behind 60oCA, 45oCA, 35oCA after intake TDC respectively ,the amount of intake air decreases with the increase of the out flowing phase, the amount of intake air has been effectively controlled by variable valve system.

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