NOx formation in gas-fired pulse combustors

The main focus of this investigation was to get a greater understanding of the effect of combustion frequency, positive pressure amplitude, relative air:fuel ratio (A), water jacket temperature and input firing rates on the emissions of NO from pulse combustors. This study was carried out by a programme of experimental work combined with the development of a one-dimensional model. Results obtained in this study from experimental measurement, revealed evidence that a Schmidt tube has the ability to operate over a wide range of parameters (such as operating frequency, positive pressure amplitude, relative air:fuel ratio, water jacket temperature and input firing rates) with variable NO emissions. It was found that the level of NO emissions became lower with increasing operating frequency and positive pressure amplitude. As an example, when the rig was operated at input firing rate 25 kW and a positive pressure amplitude of 0.12 bar, increasing the frequency from 35 Hz to 73 Hz produced a monotonic reduction in NO emissions from 61 ppm to 29 ppm (dry, 3% O2). An'increase in positive pressure amplitude from 0.05 to 0.12 bar produced a change in NO emissions from 46 ppm to 34 ppm. It was also found that the values of NO emissions fell. with increasing excess air for A> 1.1. However, NO emissions increased with increasing water jacket temperature (Tw) along the length of tail pipe and with increasing input firing rates. Experimental results showed that the positive pressure amplitude was not dependent on the wall jacket temperature. However, the operating range of stable pressure oscillation could be extended from [...continued].