The effect of the length (L4) in the mixing chamber geometries at the second stage on the entrainment ratio is shown in Figure 4.2. The area ratio of mixing chamber geometries at the second stage (A4/A6) was 1.6 and convergence angle (θII) at the second stage was 10°. The maximum entrainment ratio (Rm) was 0.694, while the length of the mixing chamber geometries was 1.6 < L4/D4