Perturbations ignition wave

In the examples given above we have tried to describe some of the phenomena which arise as a result of chemical kinetic-fluid dynamic coupling. First, we described studies of the isolated effects of chemical-acoustic coupling, emphasizing the effects on the chemical kinetics. The major conclusion is that sound waves and entropy perturbations can alter chemical timescales, and that this effect can be quantified. We then described a system in which sound waves and entropy perturbations behind a shock wave caused early ignition at unpredictable locations and at reduced ignition times. A series of reaction centers formed and one of these close to the shock front eventually ignited. 

The nozzle diameter effect on the pressure perturbation amplitude is demonstrated in Fig. 11.44. The measurements were performed at 40 MPa pressure of the hydrogen outflow. The flow ignition delay is 2 s. The spark igniter location is shown in Fig. 11.43. The turbulent combustion velocity assessed by high-speed filming is close to 300 m/s. When the nozzle diameter is less than 5 mm, the pressure wave amplitude is less than 1 kPa at a distance of 2 m or more. 

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