Search Results

Increasing the efficiency of an internal combustion engine is possible thanks to the use of an extended expansion stroke relative to the suction stroke. This solution was first patented by James Atkinson in the construction of an internal combustion engine in the XIX century. The article presents a solution using the principle of extended expansion stroke. In the design of Szymkowiak's proprietary engine, a conceptual crank-piston system was used with additional elements enabling the Atkinson cycle to be obtained. A 3D model was created based on which forces acting in the system were tested. The generated piston path profile allowed to characterize its movement. A mobile mesh of the combustion chamber was created, thanks to this a detailed CFD simulation was performed in the AVL Fire software. An important criterion was the assumption of adiabatic characteristics of processes during the combustion.

The tests were carried out on an 3D engine model with an unconventional multiple linkage system. Compared to a classic crankset, the mechanism consists of more elements. In this multiple linkage system the camshaft, the piston rod and the main rod are connected to one common element. The camshaft rotating during operation at twice the speed of the crankshaft makes possible to achieve different piston stroke lengths with each revolution. With proper synchronization of the camshaft revolution with the crankshaft, the suction and compression stroke is smaller in relation to the expansion and exhaust strokes. For this reason, the Atkinson cycle was obtained without interfering with the variable valve timing. The thermal cycle is characterized by increased theoretical thermal efficiency. Due to the unique mechanism, the piston movement has different characteristics compared to classic solutions. Therefore, work was undertaken to analyze the distribution of forces in the system.

The Institute of Combustion Engines and Transport has developed a concept of fuelling diesel engines with an improved mechanism of spray. To facilitate the spray, and consequently the combustion process, air or exhaust gas was dissolved in diesel oil. The gases mixed with diesel oil formed a solution, which induced non-equilibrium state owing to its effervescence. As a result, the gaseous phase spontaneously released from the solution throughout the whole volume. The paper presents the results of observations and measurements of the fuel injection into the open chamber recorded with AVL 513D Engine Video System. The injection process has been realized with a common rail system, where the conventional mechanism of fuel atomization has been enhanced by the presence of gas in the fuel. The solution of gas and fuel was considered separately as non-saturated, saturated and supersaturated (in the last case, some amount of gas remained undissolved in the fuel).