Variable Valve Timing Technology Research Articles

Optimization of power performance and combustion stability of ultra-lean combustion in hydrogen fuel engines through combined turbulent jet ignition and variable valve timing

Although pure hydrogen engines can achieve zero carbon and extremely low NOx emissions under ultra-lean combustion conditions, there are limitations with combustion stability and power performance. This paper combines turbulent jet ignition (TJI) and variable valve timing (VVT) technology, which not only improves the power output of pure hydrogen engines under ultra-lean combustion conditions but also ensures the engine’s stable operation. Therefore, this research reveals the working characteristics of TJI engines under lean conditions through numerical methods and explores the optimization characteristics of VVT on engine power performance and stability through experiments. The results indicate that TJI utilizes strong turbulence and multiple-point ignition to improve the efficiency of the mixture and combustion speed, ensuring reliable ignition capability under ultra-lean operating and achieving a stable and effective combustion process. According to the experimental results, the combination of TJI with VVT technology can ensure engine cyclic-variability of less than 1.5 % and the maximum values of Brake mean effective pressure (BMEP) and Brake thermal efficiency (BTE) are 4.5 bar and 41.6 %, respectively. This innovative technology combination not only enables the efficient and eco-friendly development of the transportation industry but also holds significant importance for promoting carbon-free fuels and environmental protection in the future.

Engine Performance Technology and Applications

The aim of this paper is to summarize and consolidate the optimization and improvements in engine types, new technologies, and existing technologies over the past few years. Additionally, it effectively analyzes the impact of improved engines on automotive performance and driving experience. Regarding direct-injection technology, this paper primarily highlights the new technology in the field of natural gas direct-injection engines. Among these, high-pressure direct-injection natural gas engines excel in improving fuel economy and emissions, effectively suppressing the limitations of knocking on such engines' output power. On the other hand, low-pressure direct-injection natural gas engines exhibit lower injection pressures when the engine is in the intake stroke. Concerning variable valve timing technology, the study investigates parameters such as the angle adjustment of the variable valve timing mechanism, unlocking methods, and unlocking pressures. Furthermore, the dual VVT-I technology enhances intake efficiency, ensuring ample torque output within the low and mid-range RPMs, guaranteeing sufficient power performance in various operating conditions. In today's rapidly advancing industrial technology landscape, many technologies have made significant progress. However, the current societal trend is moving towards energy conservation and carbon reduction, gradually phasing out traditional engines from the historical stage. The future development trend will be new energy engines, such as new energy materials like pure electric, hydrogen, and natural gas. Additionally, artificial intelligence will rapidly emerge in various industries.

Improving the partial-load performance and emission of GDI engine by combining injection strategy and exhaust variable valve timing technology

Improving the partial-load performance and emission of GDI engine by combining injection strategy and exhaust variable valve timing technology

Diesel engine optimization and exhaust thermal management by means of variable valve train strategies

Due to the need to achieve a fast warm-up of the after-treatment system in order to fulfill the pollutant emission regulations, a growing interest has arisen to adopt variable valve timing technology for automotive engines. Several variable valve timing strategies can be used to achieve an increment in the after-treatment upstream temperature by increasing the residual gas amount. In this study, a one-dimensional gas dynamics engine model has been used to carry out a simulation study comparing several exhaust variable valve actuation strategies. A steady-state analysis has been done in order to evaluate the potential of the different strategies at different operating points. Finally, the effect on the after-treatment warm-up, fuel economy and pollutant emission levels was evaluated over the worldwide harmonized light vehicles test cycle. As a conclusion, the combination of an advanced exhaust (early exhaust valve opening and early exhaust valve closing) and a delayed intake (late intake valve opening and late intake valve closing) presented the best trade-off between exhaust temperature increment and fuel consumption, which achieved a mean temperature increment during low-speed phase of the worldwide harmonized light vehicles test cycle of 27 °C with a fuel penalty of 6%. The exhaust valve re-opening technique offers a worse trade-off. However, the exhaust valve re-opening leads to lower nitrogen oxide (29% less) and carbon monoxide (11% less) pollutant emissions.

Optimization Method and Simulation Study of a Diesel Engine Using Full Variable Valve Motions

Variable valve timing technologies for internal combustion engines are used to improve power, torque, and increase fuel efficiency. Details of a new solution are presented in this paper for optimizing valve motions of a full variable valve actuation (FVVA) system. The optimization is conducted at different speeds by varying full variable valve motion (variable exhaust open angle, intake close angle, velocity of opening and closing, overlap, dwell duration, and lift) parameters simultaneously; the final optimized valve motions of CY4102 diesel engine are given. The CY4102 diesel engine with standard cam drives is used in large quantities in Asia. An optimized electrohydraulic actuation motion used for the FVVA system is presented. The electrohydraulic actuation and optimized valve motions were applied to the CY4102 diesel engine and modeled using gt-power engine simulation software. Advantages in terms of volumetric efficiency, maximum power, brake efficiency, and fuel consumption are compared with baseline results. Simulation results show that brake power is improved between 12.8% and 19.5% and torque is improved by 10%. Brake thermal efficiency and volumetric efficiency also show improvement. Modeling and simulation results show significant advantages of the full variable valve motion over standard cam drives.

Analysis of Variable Intake Runner Lengths and Intake Valve Open Timings on Engine Performances

In this paper, engine simulation tool is used to investigate the effect of variable intake manifold and variable valve timing technologies on the engine performance at full load engine conditions. Here, an engine model of 1.6 litre four cylinders, four stroke spark ignition (SI) engine is constructed using GT-Power software to represent the real engine conditions. This constructed model is then correlated to the experimental data to make sure the accuracy of this model. The comparison results of volumetric efficiency (VE), intake manifold air pressure (MAP), exhaust manifold back pressure (BckPress) and brake specific fuel consumption (BSFC) show very well agreement with the differences of less than 4%. Then this correlated model is used to predict the engine performance at various intake runner lengths (IRL) and various intake valve open (IVO) timings. Design of experiment and optimisation tool are applied to obtain optimum parameters. Here, several configurations of IRL and IVO timing are proposed to give several options during the engine development work. A significant improvement is found at configuration of variable IVO timing and variable IRL compared to fixed IVO timing and fixed IRL.

Numerical Calibration of Diesel Engine Variable Valve Timing

The performance of internal combustion engine can be improved by using variable valve timing technology. but how to get the optimal inlet/export valve open or close angles under various operating conditions still relies mainly on testing calibration method. By means of one-dimensional working process simulation method, the performance of a four cylinder diesel engine was simulated, and the influences of diffrent inlet/export valve timing on engine performances were compared. Optimum valve timing values and engine performances under thirty kinds of working conditions were gotton. After that, the engine performances compared with that without variable valve timing. Simulation results show that the engine performance, especially the emission performance, can be improved at all simulation working conditions. The method used in this paper may be a new way for calibration of optimal valve timing.

Pencapaian Performa Pada Katup Variabel Timing Fixed Timing Untuk Mesin Yang Optimal

Problems will be discussed in this research is how differences in exhaust emissions generated by engine with variable valve timing and valve timing on a fixed volume of motor vehicle cylinder 1300 cc. Variable valve timing technology, which is set when opening and closing the intake valve (intake valve) electronic fuel according to engine conditions. This will make mixing air and fuel that enters into an efficient machine that will produce great power, fuel economy and low emissions. Research emissions (CO, CO2, HC, O2) was performedwith dynamic testing, where the vehicle in a state of the load lifted and given transmission. Unlike the testing generally performed with a static test, in which the vehicle is at rest and without a load. This test is performed to determine how the condition of exhaust gases when the vehicle dynamic (analogous to the vehicle running). In general, machines with variable valve timing to produce better emissions than engines with fixed valve timing. The higher the spin machine and load transmission system will result in CO and HC emissions are decreased and O2 and CO2 increased. Engine with variable valve timing control the suction valve opening times to achieve optimum engine performance at various driving conditions. And set out the engineoutput as needed.

Modeling the Effects of Variable Intake Valve Timing on Diesel HCCI Combustion at Varying Load, Speed, and Boost Pressures

Homogeneous charge compression ignition (HCCI) operated engines have the potential to provide the efficiency of a typical diesel engine, with very low NOx and particulate matter emissions. However, one of the main challenges with this type of operation in diesel engines is that it can be difficult to control the combustion phasing, especially at high loads. In diesel HCCI engines, the premixed fuel-air charge tends to ignite well before top dead center, especially as load is increased, and a method of delaying the ignition is necessary. The development of variable valve timing (VVT) technology may offer an important advantage in the ability to control diesel HCCI combustion. VVT technology can allow for late intake valve closure (IVC) times, effectively changing the compression ratio of the engine. This can decrease compression temperatures and delay ignition, thus allowing the possibility to employ HCCI operation at higher loads. Furthermore, fully flexible valve trains may offer the potential for dynamic combustion phasing control over a wide range of operating conditions. A multidimensional computational fluid dynamics model is used to evaluate combustion event phasing as both IVC times and operating conditions are varied. The use of detailed chemical kinetics, based on a reduced n-heptane mechanism, provides ignition and combustion predictions and includes low-temperature chemistry. The use of IVC delay is demonstrated to offer effective control of diesel HCCI combustion phasing over varying loads, engine speeds, and boost pressures. Additionally, as fueling levels are increased, charge mixture properties are observed to have a significant effect on combustion phasing. While increased fueling rates are generally seen to advance combustion phasing, the reduction of specific heat ratio in higher equivalence ratio mixtures can also cause noticeably slower temperature rise rates, affecting ignition timing and combustion phasing. Variable intake valve timing may offer a promising and flexible control mechanism for the phasing of diesel HCCI combustion. Over a large range of boost pressures, loads, and engine speeds, the use of delayed IVC is shown to sufficiently delay combustion in order to obtain optimal combustion phasing and increased work output, thus pointing towards the possibility of expanding the current HCCI operating range into higher load points.