Experimental research of an integrated scavenging pump coupled with a buffer tank for a free-piston engine

Free-piston engine is considered one of the potential range extenders for hybrid vehicles because of its high thermal efficiency, low mechanical loss, and ultimate fuel flexibility. The performance of scavenging devices or structures is critical of two-stroke free-piston engine stable operation. This paper aims to explore the operating characteristics of an integrated scavenging pump coupled with a buffer tank under different operating conditions to promote the application of scavenging pumps on free-piston engines. Hence, a detailed contrast experiment is performed to investigate the effect of the buffer tank volume, discharge position and deflated pressure on the scavenging pump performance. By analysing the experimental results, a weighting score system is employed in deciding the most appropriate buffer tank for the application. The CFD calculation of the gas exchanging process to validate the feasibility of the selected scavenging pump parameters. In addition, the influence of buffer tank pressure on combustion is evaluated via scavenging combustion tests. The experiment results show that the maximum in-cylinder pressure can reach 47.44 bar when the buffer tank pressure 165 kPa.