Impulse Measurement of Pulse Combustion Tube using Accelerometer

An experimental study of impulse produced by a pulse combustion tube based on acceleration measurement has been performed. Mixtures of propane and oxygen with nitrogen dilution of 10%, 25% and 50%, were used as the combustible medium. Experiments were done at 3 equivalence ratios; 0.75, 1 and 1.25. A single point electrical spark at 0.1 Joule energy was used as the ignition source. Pressure of reaction front was measured to determine the combustion wave propagation velocity. The value of measured velocity was used as the basis to differentiate between deflagration and detonation mode of combustion wave. Experimental data were compared with calculated value for the impulse force and the velocity. Detonation was not observed both for the case of lean mixture case as well as when the dilution of nitrogen was increased beyond 25%. In the case where the detonation was not observed, the tube experienced less acceleration rate, resulting in reduction of the impulse force. By decreasing the amount of nitrogen and/or increasing the stoichiometric level, detonation mode of combustion wave propagation was observed and the tube experienced high acceleration rate thus increasing the impulse force.