Development of a plasma-coupled rapid compression machine to study advanced ignition concepts

Enhancing the operability of next-generation combustion devices with emerging fuels at near-limit conditions requires the development of innovative ignition strategies. To address this need, a new modular plasma-coupled rapid compression machine (PRCM) featuring a mono-piston, single-stroke configuration was developed to support auto-ignition, conventional spark-ignition, and non-equilibrium plasma-assisted ignition studies within a single experimental platform. The PRCM attains end-of-compression pressures up to 70 bar and temperatures up to 1200 K, enabling systematic investigation of ignition phenomenon and the effects of non-equilibrium plasmas on fuel reactivity at regimes inaccessible to previous platforms. A high-voltage pulse generator delivers up to 20 kV pulses at repetition rates up to 100 kHz, producing kilohertz repetitive nanosecond pulsed (KRNP) discharges at elevated pressures in the combustion chamber. Integrated diagnostics include high-speed pressure transducers and optical access to enable time-resolved measurements of ignition delay, burn rate, and kernel and plasma morphology to probe for plasma-combustion coupling. Initial benchmarking with methane and n-butane mixtures demonstrated good agreement with auto-ignition data from the literature, validating the PRCM's functionality and measurement fidelity. Preliminary KRNP studies at 10 bar revealed a nearly 20% increase in burn rate compared to conventional spark ignition for n-butane, highlighting the efficacy of pulsed plasma in enhancing fuel reactivity and ignition kernels. This novel experimental facility offers a versatile, high-fidelity platform for investigating the fundamental processes by which non-equilibrium plasmas initiate, control, and accelerate combustion. These insights are expected to guide the design of optimized plasma-based ignition strategies for advanced air-breathing propulsion and power systems.