The paper is focused on the synthesis and analysis of a variable valve lift and timing (VVLT) mechanism, used to enhance the fuel consumption in the low part loads operation. This mechanism is self-regulated thanks to a hydro-mechanical system, which is the subject of a French patent and allows a continuously intake valve lift and opening variation. The synthesis, which consisted in finding out the required intake cam profile starting from an imposed

The VVA system that is to be presented in this paper is actually a variable intake valve lift and timing mechanism (VVLT) and is part of a larger project whose final goal is to combine it with variable compression ratio and turbocharging in the context of the downsizing technique. Such an engine, entitled adaptive thermal engine, is currently in progress of being developed at the University of Pitesti. Due to its complexity, a primary stage was firstly

The inefficient running of the spark ignition engine at part loads due to the load control method, but mostly, their major weighting in vehicle’s operation time justifies the interest for the technical solutions, which act in this particular operating range. These drawbacks encountered at low part loads are even more amplified when talking about bigger engines. For instance, it is well known the fact that at the same engine load, a bigger engine

The paper deals with the analysis of adaptive thermal engine lower block, first by means of classical calculations and then by means of finite elements method. Taking into account, that lower block is the supporting structure for the adaptive thermal engine, the deformations and stresses, the eigenfrequencies and eigenmodes, have all been tried to be found, in order to be able to say if the structure is rigid enough for adaptive thermal engine application.

This paper presents a further investigation into the effect of higher-expansion cycle in a spark ignition engine, realized either by late or by early intake valve(s) closing. This kind of cycle is called Miller cycle. Any of these two methods goes to a reduced specific output due to the decreasing of volumetric efficiency. That’s why, a Miller cycle engine has to be supercharged. Thus the paper presents some results regarding the effect of supercharging

Of the higher expansion cycles, Miller cycle is obtained by late closing of the intake valve(s). The result is the artificial decrease of the compression ratio relatively to expansion ratio, which remains the same, in this way compression and expansion being no longer dependent on each other. The paper presents the concept of more-, over- or higher expansion cycle at spark ignition engine, called Miller cycle and it also intends to show what has

Since the knock and NOx is affected by the gas temperature and pressure at TDC, in other words by the geometrical compression ratio, while the thermal efficiency of the cycle is determined by the work during the expansion stroke, a better way to increase the efficiency is to have higher expansion ratios rather than higher compression ratios. Thus the paper presents some results regarding the effect of high compression and high expansion theoretical

In a century of internal combustion engine with piston and valves development, automatic regulation of air-fuel ratio and spark advance in function of speed and load were realized. Nowadays, the only way to obtain lower consumption and pollution is to provide this engine with automatic control systems such as variable valve timing and variable compression ratio. This paper describes the construction, a short calculus and some of the performances

Nowadays, taking into account the wide variety of car engines working regimes, the only way to obtain lower consumption and pollution is to provide this engine with automatic control systems such variable compression ratio and variable valve timing. Such an engine is the subject of Romanian patent no 111863B. The purpose of this paper is to show that this engine, as an automatic system with self-regulation, can respond fast enough when working processes