中文摘要：

介绍了液压自由活塞发动机（HFPE）与液压约束活塞发动机（HCPE）的发展现状，就两者的结构原理、功能特性等方面进行了对比分析。HFPE和HCPE都能直接将燃料燃烧产生的热能转化为液压能，都可作为伞液压午辆动力源使用。采用传统的燃烧技术，HFPE总效率可达40％，HCPE可达35％。两者任何工况下都能方便地工作在最佳经济工况，方便地回收车辆制动能量，提高整车效率。

英文摘要：

Development of hydraulic free piston engine （HFPE）and hydraulic confined piston engine（HCPE） was described, the comparative analysis of their structural principle and main performance character was carried out also. HFPE and HCPE can both directly transform thermal energy int. hydraulic energy and be used as power source at full hydraulic vehicle. Using traditional combustion technology, the efficiency of HFPE reaches 40%, HCPE reaches 35%. In any working condition, they can easily work at optimal economic routine, recover braking energy and improve the efficiency of the entire vehicle.