## 3 Experimental Research Results, Analysis and Discussion  
The changes in the instantaneous values of the air flow velocity \(w_{x}\) for time \(\tau\) at different heights \(h\) for the installation of the hot-wire anemometer sensor and for different initial flow velocities \(w_{\rm o}\) are presented in Figures 6 and 7. Figure 6: Dependences of instantaneous values of flow velocity \(w_{x}\) on time \(\tau\) for initial \(w_{\rm o}\) = 1.12 m/s in a vertical conical diffuser at different heights \(h\) (along diffuser axis): (**a**) \(h\) = 150 mm and (**b**) \(h\) = 450 mm (\(w\) is average flow velocity at measured point). Figure 6a shows that the spread of the air flow velocity oscillation amplitude is up to 0.6 m/s for \(w_{\rm o}\) = 1.12 m/s and \(h\) = 150 mm. At the same time, air flow velocity fluctuations are observed on the function \(w_{x}\) = \(f\) (\(\tau\)). In general, the function \(w_{x}\) = \(f\) (\(\tau\)) does not have a clearly expressed trend and is similar to white noise. The function \(w_{x}\) = \(f\) (\(\tau\)) is transformed downstream for \(h\) = 450 mm (Figure 6b). There is a decrease in the spread of the velocity fluctuations to 0.35 m/s. The velocity fluctuations become more orderly. There is also a decrease in the average flow velocity at the measurement points under consideration from 0.39 m/s (\(h\) = 150 mm) to 0.175 m/s (\(h\) = 450 mm). An increase in the initial air flow velocity (\(w_{\rm o}\) = 2.22 m/s) at the diffuser inlet causes a slight increase in the amplitude of the flow velocity oscillations to 0.7 m/s for \(h\) = 150 mm (Figure 7a). An increase in the initial flow velocity led to an increase in the flow velocity oscillations by 14% for \(h\) = 150 mm. Speed fluctuations are also observed in the \(w_{x}\) = \(f\) (\(\tau\)) dependencies, which is typical for all measurement points. The spread of the air flow speed fluctuations is 0.55 m/s for \(h\) = 450 mm (Figure 7b). Accordingly, an increase in the initial velocity from \(w_{\rm o}\) = 1.12 m/s to \(w_{\rm o}\) = 2.22 m/s causes an increase in the amplitudes of the \(w_{x}\) pulsations by 36%. This indirectly indicates an increase in large- and small-scale flow turbulence with an increase in the initial velocity \(w_{\rm o}\). Turbulization of the flow should have a positive effect on the heat and mass transfer processes in the vertical diffuser. In the applied aspect, turbulization of the flow can improve the mixing and combustion processes in the flow gasifier. The velocity fields \(w\) were obtained by averaging the instantaneous values of \(w_{x}\) at each measurement point and the velocity fields in the vertical diffuser were obtained for different initial velocities to assess the evolution of the flow structure under different boundary conditions (Figure 8). Figure 8a shows that the air flow moves mainly along the diffuser axis at an initial velocity of \(w_{\rm o}\) = 0.4 m/s. It can be assumed that the location of the flow outlet does not affect the direction of air movement at low initial velocities \(w_{\rm o}\). This is since the flow energy is insufficient to set the trajectory of the air movement direction. Accordingly, the air flow is dispersed throughout the entire volume of the diffuser. Figure 7: Dependences of instantaneous values of flow velocity \(w_{x}\) on time \(\tau\) for initial \(w_{\rm o}\) = 2.22 m/s in a vertical conical diffuser at different heights \(h\) (along diffuser axis): (**a**) \(h\) = 150 mm and (**b**) \(h\) = 450 mm (\(w\) is average flow velocity at measured point). An increase in the initial velocity to \(w_{\rm o}\) = 2.22 m/s causes a significant change in the air flow structure in the vertical diffuser under study (Figure 8b). There is a clearly expressed \"sticking\" of the flow to the right side of the diffuser. The flow movement along the right side of the diffuser is caused by the presence of an air outlet on this side.