Preparation method of head for starting wide envelope of combustion chamber of evaporating pipe

The invention discloses a preparation method of a head for starting a wide envelope of an evaporation tube combustion chamber, an annular cavity is formed by a flame tube outer ring, a flame tube front end face and a flame tube inner ring, a plurality of inverted L-shaped contraction type evaporation tubes are arranged in the cavity, and each contraction type evaporation tube comprises an evaporation tube contraction type inlet and an evaporation tube contraction type outlet. Flame tube outer ring head air inlet holes and flame tube inner ring head air inlet holes are formed in the flame tube periodic section where the evaporation tube contraction type outlet is located, and a plurality of main combustion holes are formed in the flame tube inner ring and the flame tube outer ring respectively. By adopting the design of the segmented contraction type evaporation pipe and constructing a large-scale vortex structure at the head part of the combustion chamber, the working envelope of the combustion chamber is exp