# Dynamics of Hydrogen-oxygen-argon cellular detonations with a constant mean lateral strain rate

## TL;DR

This study investigates hydrogen-oxygen-argon detonations in expanding channels, demonstrating that macro-scale detonation speeds align well with first principles models, especially due to longer reaction zones from argon dilution, despite cellular instabilities.

## Contribution

The paper provides experimental validation of quasi-1D detonation models in complex geometries with argon dilution, highlighting the influence of reaction zone length on macro-scale dynamics.

## Key findings

- Detonation speeds agree with first principles predictions.
- Longer reaction zones due to argon dilution improve model accuracy.
- Detonations propagate slightly beyond predicted strain rate limits.

## Abstract

The present work revisits the problem of modelling the real gaseous detonation dynamics at the macro-scale by simple steady one-dimensional (1D) models. Experiments of detonations propagating in channels with exponentially expanding cross-sections were conducted in the H2/O2/Ar reactive system. Steady detonation waves were obtained at the macro-scale, with cellular structures characterized by reactive transverse waves. For all the mixtures studied, the dependence of the mean detonation speed was found to be in excellent agreement with first principles predictions of quasi-1D detonation dynamics with lateral strain rate predicted from detailed chemical kinetic models. This excellent agreement departs from the earlier experiments of Radulescu and Borzou (2018) in more unstable detonations. The excellent agreement is likely due to the much longer reaction zone lengths of argon diluted hydrogen-oxygen detonations at low pressures, as compared with the characteristic induction zone lengths. While the cellular instability modifies the detonation induction zone, the detonation dynamics at the macro-scale are arguably controlled by its hydrodynamic thickness. Near the limit, minor discrepancy is observed, with the experimental detonations typically continuing to propagate to slightly higher lateral strain rates and higher velocity deficits.