Investigating the Possibility of Air Cooling Compact Jet Combustion Chambers Working at Alpha(Gamma) = 1

摘要

Compact combustion chambers of jet engines (20-40 mm flame tube diameter and 200-300 mm long) operating at an air excess coefficient alpha(sub Gamma) minus 1 and exposed to substantial thermal loads in the range of 50,100,000 to 70,100,000 kcal/m(hr(ata) are difficult to cool with air. Therefore, to study this problem an investigation was made of a simplified flame tube with convective air cooling. The cooling air circulates through a special annular chennel formed by the flame tube wall and the liner. The air is used for cooling purposes only, and is discharged into the atmosphere at the exit of the cooling channel. The amount of air required is calculated under the following conditions: (1) the combustion temperature is practically not affected by the cooling system; (2) the fuel burnout law and the air temperature rise along the flame tube length are linear functions; (3) a turbulent flow regime is present in the cold and hot flows; (4) the average values of heat transfer coefficients alpha (subscript 1) and alpha (subscript 2) are determined in the first approximation along the total length of the combustion chamber, and the effect of the temperature factor is not considered; (5) the outside surface of the linear wall is provided with heat insulation, and the heat transfered from the flame tube to the cooling flow increases the flow enthalpy. (Author)