Optical investigation of Argon Power Cycle (APC)

The growing global demand for energy, combined with the urgent need to reduce greenhouse gas (GHG) emissions, is driving the development of alternative combustion technologies across transport sectors. Low- and zero-carbon fuels such as methanol, ammonia, and hydrogen are being explored as viable replacements for fossil fuels in internal combustion engine (ICE) applications. Among these, hydrogen stands out due to its wide flammability range and fast, carbon-free combustion. Research is ongoing to understand how hydrogen and other alternative fuels can be used most efficiently in ICEs. One promising concept is the Argon Power Cycle (APC), which could enable high-efficiency, zero-emission combustion in ICEs. In this approach, argon replaces air as the working fluid. Argon’s higher specific heat ratio (1.66 vs. 1.4 for air) and lower thermal conductivity both help increase efficiency. The absence of nitrogen also means NOx emissions are eliminated. The APC system is relatively simple: hydrogen and oxygen are injected directly into the cylinder at stoichiometric conditions. Combustion produces only water vapor, which can be condensed from the exhaust. The argon, free of combustion byproducts, is recycled back into the intake, creating a closed-loop system. However, several challenges remain before this technology can become commercially viable. A key issue is the limited understanding of hydrogen combustion in an argon atmosphere under engine-relevant conditions. To address this, the study uses a cutting-edge optical engine, allowing for visual diagnostics of the flame during combustion while maintaining realistic pressures. The goal is to evaluate APC under controlled conditions and compare its performance to a conventional air-breathing engine. This will be one of the first optical engine studies of APC ever published.