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Numerical simulation and experimental identification of the hydraulic servomechanisms
Published in Nicolae Vasiliu, Daniela Vasiliu, Constantin Călinoiu, Radu Puhalschi, Simulation of Fluid Power Systems with Simcenter Amesim, 2018
Nicolae Vasiliu, Daniela Vasiliu, Constantin Călinoiu, Radu Puhalschi
Some practical implementation of the EHVS developed by Sturman Industries in 2008 for GENERAL MOTORS CORPORATION has shown the following benefits of camless engines, which is confirmed during official assessment [13]: independent valve lift and timing control allow mixed-charge combustion; low parasitic loss, since most of the conventional valve train (including the camshaft), is eliminated; high-speed engine operation (up to 12,000 rpm); homogeneous charge compression ignition combustion is enabled; cylinder deactivation and cylinder balancing are enabled; scalable to any engine size, and can be retrofitted to older engines as all the technology is in the head; compatible with any fuel type; a square lift pattern compared to the lobe profiles that a camshaft requires; can be used to create an internal exhaust gas recirculation (EGR) system; potential up to 60% thermal efficiency; and can be used to help eliminate the need for an exhaust after treatment.
Experimental analysis of the volumetric and thermal efficiency performance of a novel direct piezo-acting CVVT mechanism
Published in International Journal of Green Energy, 2023
A. Sürmen, M.I Karamangil, A Avcı, B. Dirim, F. Işıklı, M. Tekin, N. Türköz
The idea of a camless ICE emerged in early 1899 (Deokar 2013). In camless systems, the need for a mechanical connection between the camshaft and valve mechanism is eliminated, thereby preventing friction losses. The variability in valve travel and valve timing is the most prominent feature of this system. Electro-mechanical (electromagnetic), electro-hydraulic and electro-pneumatic valve mechanisms are considered in this category. In the electromagnetic valve mechanism, the opening and closing times of the valves are determined by magnetic coils. Electromagnet force is activated to maintain the moving element and the valve to which it is connected in an open or closed position. In this system, the selection of springs is critical, as they must be sufficiently large to overcome the variable gas forces caused by the magnet force, spring force, and pressure differences in the engine (Bergstrom 2001).
Performance enhancement of camless air engine by optimising the inlet-valve cut-off position
Published in International Journal of Ambient Energy, 2022
Nikhilkumar Jagjivanbhai Chotai, Vivek Patel, Vimal Savsani, Motwani Karan
In the base research engine (camless engine), cam and follower were replaced by a solenoid-operated DCV to reduce the friction power losses. DCV-operated cranking mechanism is also known as a fully flexible variable valve train mechanism, which can be controlled by the controller. Camless mechanism’s valve flexibility was adapted for early or delayed closing of inlet and exhaust valve and to control the supply of intake compressed air during the cycle. In the camless mechanism, there is no dependency on a predefined cam profile. Camless mechanism can change intake and exhaust duration as per programming and set any state of early or delayed valve intake and exhaust duration, thus creating the engine's operational flexibility. Figure 2 shows the two phases of the first stroke. The first phase is the compressed air intake, and the second is the expansion phase. The excessive supply of compressed air was controlled by operating solenoid at a proper time frame. Extraction of maximum energy from input compressed air attained through a cut-off supply of air at the appropriate intake duration (crank angle), thus allowing the optimum quantity of compressed air, which has sufficient time to expand during the rest of the stroke in the cylinder (Marvania and Subudhi 2017). There is not enough time if compressed air is continuously supplied from 0° to 180°. The experimental setup was developed by considering this intake advance angle or early cut off position as the prime point of analysis, which maximises input energy utilisation and increases the air engine's efficiency (Chen, Liu, and Tao 2005).
Modelling of an electro-hydraulic variable valve actuator for camless engines aimed at controlling valve lift parameters
Published in International Journal of Control, 2021
Alessandro di Gaeta, Carlos Ildefonso Hoyos Velasco, Veniero Giglio
The results clearly show that the power losses of a camless engine based on such EHVAs are always lower than those of a traditional cam-based engine at all engine speeds and that power differences only seem to be less at high speeds. Furthermore, power losses due to pumping the oil in the HP circuit, i.e. gear pump and electrical motor power losses, account for about of total power loss; the remaining is due to the valve actuators.