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Show 30 25 20 15 10 5 :: :ii; : r 7 ^ ^ 13 11 9 7 5 3 1 3 5 7 9 11 1/m~ - m Figure 3. DIMENSIONLESS FLAME LENGTH U VERSUS RATIO BETWEEN AIR AND GAS JET m=UJUg VELOCITY FOR THE COMBUSTION COMPLETENESS n=l differences of m from 1 depend on the character of the ratio m. Thus, if the gas velocity is higher than the air velocity U^»UA (m«\), the limiting value of Lf becomes much less than that of the case of the inverse relationship. The calculations enabled to deduce a relationship between main geometric and thermal and gas dynamic parameters of the frontal equipment of the combustion chamber, which provide the shortest diffusion flame length L{ and thus, the shortest combustion chamber length (Lc=Lf, see Figure 1). EXPERIMENTAL SETUP The experiments were carried out using a model combustion chamber with the square transversal cross-section of 0.15 m x 0.15 m and the length of 0.3 m. Natural gas or evaporated kerosine and air were used as a fuel and an oxidizer, respectively. A n air was forced into the combustion chamber by a blower. Evaporated kerosine was supplied from special evaporator to manifold installed in the air flow. The manifold constituted a set of hollow bluff bodies uniformly distributed over the cross-section of the combustion chamber. The evaporated kerosine was fed through holes on the rear, streamwise, side of these bodies. W h e n using natural gas as a fuel, the air temperature was equal to Ta=293 K and 573 K while using evaporated kerosine. Air and fuel flow rate as well as gas composition in the outlet cross-section of the combustion chamber was measured. Using the measured values, local values of the excess air a* and coefficient of fuel combustion completeness r\i, as well as concentrations of nitrogen oxides, carbon and not completely burned hydrocarbons were determined. 5 |