Theoretical Research of the Mechanism for Compression Ratio Changing of the Conrod-Free Engine

The article is devoted to the conrod-free internal combustion engine (ICE). An analytical review of the papers on the application of variable compression ratio on gasoline ICE is carried out. Theoretical research of the engine without connecting rod with rocking mechanism is carried out. This research is directed at improving the mechanism for compression ratio changing (MCRC) for the gasoline four-stroke engine. The mathematical model for calculating the response time of the mechanism compression ratio is developed. The mathematical model for calculating the response time of the compression ratio of the MCRC is developed in the article. This made it possible to reveal the influence of various engine factors with the connecting rod and crank mechanism (CRCM) on the operation of the MCRC (e.g., the rate of the compression ratio change). The results of the study of the operation of the MCRC indicate a strong influence of the values δ (relative area of flow passage of channels) and р (pressure) on the response time τ in the field of their small values. This indicates that with insignificant changes of the area of flow passage in the channel of the hydraulic lock and the smallish oil pressure in the cavities, a significant response rate of the MCRC is ensured. The results demonstrate the possibility to get the speedy compression ratio change of the engine with the MCRC. Calculation studies show that the mechanism’s full operation takes place fairly quickly (0.02 s per unit ε_x), which indicates the expediency of using such a high-pressure pump in a four-stroke gasoline engine with CRCM. The mechanism’s movable body complete movement (S = 4 mm) at an oil temperature of 45°C in the hydraulic system and pressure of p = 60 bar on the body is stated to take place for 0.2 s.