## 4 Experimental Verification
### Mixing Uniformity of the Slurry  
During the experiment, the machine is first started and allowed to run smoothly. Material is then added according to the proportions. After the readings of the torque, pressure sensors, etc., stabilize, samples of 30 mL are taken every 1 min for measurement (the beaker provided with the electronic density meter has a capacity of 50 mL). The prepared mixture was sampled at various rotational speeds to obtain a significant number of density samples of the slurry mixture. The test results included the simulated slurry mixture density for each group, along with the mean value and standard deviation of the density for each group (as depicted in Table 6). Additionally, the relationship between the average density of the simulated slurry mixture and the change in rotor speed was illustrated (as shown in Table 6). Through comparative analysis of the density values of slurry mixtures in each group, as presented in Table 6, it is observed that the mixture density of propellant simulants fluctuates to a certain extent at different rotational speeds, albeit the fluctuation is not significant. Specifically, at rotational speeds of 15 r/min, 25 r/min, 35 r/min, 45 r/min, and 55 r/min, the average densities were recorded as 1.197 g/cm\({}^{3}\), 1.199 g/cm\({}^{3}\), 1.206 g/cm\({}^{3}\), 1.207 g/cm\({}^{3}\), and 1.202 g/cm\({}^{3}\), respectively. The minimum standard deviation is 0.0082, and the maximum standard deviation is 0.0130. It can be deduced that the distribution density uniformity exceeds 90% (standard deviation is less than 0.1), indicating that the internal meshing screw mixer exhibited excellent efficiency in the mixing process between high-viscosity fluid and fine powder, to demonstrate the feasibility of applying the intermeshing screw mixing device in the food industry and the correctness of this design method. Using the mixing uniformity index to quantify the mixing effect of the slurry is defined as the ratio of the bulk density of the powdered material in the mixed slurry to the standard deviation of the mixture prepared by the intermeshing screw. The higher the mixing uniformity index, according to its definition, the greater the mixing uniformity. The calculation formula for the mixing uniformity index is as follows [41]:  
\[I=\frac{\rho_{0}}{10\text{s}} \tag{8}\]  
where \(I\) represents the mixing uniformity index; \(\rho_{0}\) is the bulk density of the powdered material, which, in this case, is the bulk density of flour since the powdered material in the slurry is flour; and \(s\) is the standard deviation of the density of the slurry after mixing, and \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Rotational Speed/r min\({}^{-1}\)**} & \multicolumn{6}{c}{**Slurry (2:1 Ratio of Corn Syrup to Flour Mixture)**} \\ \cline{2-7}  & **15** & **25** & **35** & **45** & **55** & **Mean Value** \\ \hline Non-newtonian fluid index \(n\) & 0.9799 & 0.9803 & 0.9807 & 0.9812 & 0.9817 & 0.98068 \\ Undulate/\% & \(-0.09\%\) & \(-0.05\%\) & \(-0.01\%\) & 0.04\% & 0.10\% & \\ Consistency coefficient \(k\)/Pa-s\({}^{n}\) & 303.88 & 297.17 & 289.67 & 281.84 & 273.09 & 289.1275 \\ Undulate (\%) & 5.10\% & 2.78\% & 0.19\% & \(-2.52\%\) & \(-5.55\%\) & \\ Degree of fitting \(R^{2}\) & 0.9196 & 0.9184 & 0.9149 & 0.9086 & 0.898 & 0.9119 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Rheological parameters of slurry at different rotational speeds. the unit of bulk density of the powdered material is consistent with the unit of standard deviation of slurry density. The average speed, distribution, and mixing uniformity index for different speeds are presented in Figure 17. It can be observed that the density of the slurry varies little at different speeds. The mixing uniformity index gradually decreases with increasing speed, reaching its maximum at 15 r/min. The overall trend of the mixing uniformity index decreases with increasing speed, indicating a deterioration in density uniformity.