Propagation limits of cellular detonation in narrow channels

Abstract

This study investigates the propagation limits of cellular detonation in narrow channels, aiming to distinguish between two mechanisms that govern these limits: the first associated with detonation cell accommodation and the second with boundary losses. Hydrogen–oxygen–argon mixtures were tested with and without ozone addition at initial pressures ranging from 5 to 35 kPa in three experimental configurations: (1) a base channel, (2) a half-height channel, and (3) a half-width channel. For each configuration, experiments were conducted at progressively lower pressures until detonation failed. For the base channel with and without ozone addition, and the half-height channel, detonation failure was observed to be governed by the cell limit, i.e., the geometric accommodation of cellular structures by the narrow channel. Specifically, ozone doping extended the detonation limit to lower pressures by reducing cell size, while decreasing channel height constrained cell development, leading to failure at higher pressures. Immediately before their respective limits, all three test sets exhibited the characteristic half-cell, zig-zag pattern. In contrast, results from the half-width channel with enhanced boundary losses revealed that there exists a loss limit: detonation failure started to appear at elevated pressures and became progressively more probable as pressure decreased, eventually reaching absolute failure. Unlike the zig-zag propagation mode, detonation either propagates with a multi-cell structure or fails completely. Ozone addition was ineffective at extending the limit, suggesting that detonation failure is governed by loss mechanisms independent of cell size. We further performed modified ZND calculations that take into account the impact of flow divergence. The models correctly captured the velocity deficit trends and limiting pressures, validating the experimental identification of the loss limit. These findings demonstrate that detonation failure in cellular detonations can be dominated by boundary losses, implying that modifying cellular structures alone may not extend propagation limits in confined systems with significant losses.