One promising technique for increasing the efficiency of combustion engines is to perform the reaction at extremely high compression ratios. To manage significantly higher temperatures and pressures, a new engine architecture is required. In addition, critical questions must be answered to address feasibility of operating at these extreme states. To investigate these questions, a single-shot, free-piston laboratory device was built, capable of achieving combustion at compression ratios of 100:1 and greater. This paper quantifies the combined heat- and mass-transfer losses present during air-compression experiments. Since these air-compression losses are also present during combustion experiments, quantifying these baseline operating losses, independent from additional losses during combustion, will help in assessing feasibility of the overall strategy as well as in identifying specific strategies for achieving higher efficiencies.

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