A highly optical, controlled trajectory rapid compression and expansion machine for gas phase chemical physics research.

The article focuses on the design, development, and validation of a highly optical Controlled Trajectory Rapid Compression and Expansion Machine (CT-RCEM) at the University of Minnesota for advanced research in gas phase chemical kinetics, combustion, and high-temperature gas dynamics. The CT-RCEM features precise electrohydraulic piston motion control with active feedback, enabling digital adjustment of compression ratio, stroke, compression time, and piston trajectory without mechanical intervention, thereby improving repeatability and operational flexibility. Its optical test section includes four side-wall and one end-wall sapphire windows designed to withstand pressures up to 250 bar and temperatures up to 300 °C, allowing simultaneous advanced optical diagnostics such as high-speed imaging, schlieren, and chemiluminescence. Demonstrated through autoignition studies of dimethyl ether/air and spark and pre-chamber ignition of methane/air, the CT-RCEM provides a versatile platform for investigating combustion phenomena and supports collaborative research in sustainable energy and propulsion technologies.