OCR Text |
Show R E S U L T S A N D DISCUSSIONS The preliminary experiments were devoted to special tests to establish the steady-state diffusion flame in the vicinity of the fuel jet feedings and to spread the flame among the fuel jets at the air flow velocity UA up to 30 m/s. As a result of the experiments, the shape and the sizes of the hollow bluff bodies - the evaporated kerosine feeding manifolds - were determined. The bluff bodies with the fuel feeding holes maintained the steady-state flame stabilization and ensured a necessary distance between the axes of the neighboring fuel jets to secure their firing. The coefficient of the fuel combustion completeness r\ versus the excess air a is presented in Figure 4. As may be seen from it, the coefficient of the fuel combustion completeness within the combustion chamber has a value of approximately 100%, until a=2.5. While enriching the mixture up to a= 1.5, the fuel combustion completeness decreases by 80%. The other 2 0 % of the fuel burns in the short diffusion flame behind the chamber in a free flow. To improve the fuel combustion completeness while enriching the mixture from a=2.5 to a=l, part of the fuel may be fed into an air flow before the combustion chamber, that is approximately 1 m from the inlet of the chamber. In the case, the fuel-air mixture composition is very poor before the combustion chamber. Therefore, there is no danger of a flameout in the upstream direction. The local NOx concentration with respect to the excess air factor is presented in Figure 5 for the evaporated kerosine combustion. As evident from Figure 5, the N O x concentration in the combustion gas composition is quite low. To officially certificate the combustion chamber the experiments with natural gas combustion were carried out in the laboratory of the experimental plant of the Joint-Stock Company "Promgaz" (Kamensk, Russia). Nominal gas flow rate was held at the level of 18 m3/hour (180 k W ) in the experiments. The investigations confirmed remarkable operating characteristics, namely, stable ignition of the combustion chamber, wide range of the steady-state run of the combustion chamber, high level of the fuel combustion completeness, and low emission of N O X(50 vppm at a=l). 1.0 0.9 0,8 0,7 A J* A At A A A 1 2 3 4 5 6 a Figure 4 COEFFICIENT OF FUEL COMBUSTION COMPLETENESS WITH RESPECT TO EXCESS AIR: tV.=25m/s, 7>573K 6 |