Performance of a micro engine with heptane as working fluid

A micro Newcomen engine is proposed. To overcome the problems of friction and leakage of the micro mechanical parts during engine's operation, we use a flexible ripple tube to integrate piston and cylinder into one monolithic part. Heptane is used as the working fluid, and it works in the two-phase condition for higher energy output density per thermodynamic cycle. In the experiment, the prototype engine is tested under different operational conditions. It works continuously and generates the net mechanical work of 0.833 J per cycle with an efficiency of 2.77% in the maximum. The experimental results prove its feasibility. However, the prototype engine still requires further improvement and optimization for better performance.