Combustion tube and combustor for gas turbine, and gas turbine

A combustion tube for a gas turbine including an outlet section having a cross-section of an annular sector-shape. The outlet section includes an outer wall forming an outer peripheral boundary of the annular sector-shape, an inner wall forming an inner peripheral boundary of the annular sector-shape, and a pair of side walls forming boundaries on both sides of the annular sector-shape in a circumferential direction, respectively. The outer wall extends obliquely with respect to the inner wall such that a height of the annular sector-shape decreases toward an outlet opening of the combustion tube. A first side wall extends obliquely with respect to a second side such that a perimeter of the annular sector-shape increases toward the outlet opening of the combustion tube. An inclination angle θ1 of the first side wall with respect to the second side wall satisfies 0