## 2 Design of Self-Inhaling Internal Cooling Structured Grinding Wheel
### Influence of Grinding Wheel's Cooling Hole Position and Size
Then, the outlet flow rate fluctuates around a relatively stable value. According to the results, we can choose a cooling hole position at 11.25 mm from the center to achieve a large outlet flow rate and a relatively reasonable outlet velocity. Under the same conditions, a larger outlet flow rate can guarantee that more coolant enters the grinding zone through the cooling holes, which improves the cooling performance of the grinding wheel and enhances the flow of grinding debris. A relatively reasonable outlet velocity means the coolant has enough kinetic energy to flush the abrasive grain clusters, carrying away the grinding debris through the grooves and gaps between the abrasive grains, resulting in better surface grinding quality. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Parameters** & & & & & & & \\ \hline Cooling hole locations (mm) & 10.5 & 10.75 & 11.0 & 11.25 & 11.5 & 11.75 & 12 \\ The average speed of the & & & & & & & \\ outlet \(V_{\text{out}}\) (m/s) & & & & & & & \\ Outlet flow Q (kg/s) & 0.356 & 0.354 & 0.359 & 0.370 & 0.357 & 0.358 & 0.358 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulation results for cooling hole positions. Figure 4: Fluid motion for different cooling hole positions: (**a**) average speed of outlet; (**b**) outlet flow. 2. Diameter of the cooling holes For different cooling hole diameters, based on the design parameters determined in previous sections, the diameter range for the cooling holes was set to 1.5 mm to 2.5 mm. The basic conditions for the simulation were as follows: 12 cooling holes positioned 11.25 mm away from the center, with a rotational speed of 3000 r/min, and a coolant inlet pressure of 5 bar. Simulation calculations for the internal flow field of the grinding wheel were performed for different cooling hole diameters, and the simulation results are shown in Table 3.  
Based on the data in Table 3, with the cooling hole diameter values as the x-axis, and the outlet average velocity and outlet flow rate values as the y-axis, line graphs are plotted in Figure 5.  
It can be seen that as the cooling hole diameter increases, the outlet flow velocity of the coolant continually decreases. When the cooling hole diameter is in the range of 1.9 mm to 2.0 mm, the change in outlet velocity slows down. Furthermore, within this range, the coolant outlet velocity is relatively reasonable. As the cooling hole diameter increases, the outlet flow rate of the coolant basically shows an increasing trend. When the cooling hole diameter is between 1.5 mm and 2.0 mm, the increasing trend is more significant. When  
Figure 5: Fluid motion for different cooling hole diameters: (**a**) average speed of outlet; (**b**) outlet flow. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Cooling Hole Diameter** & **Average Speed of Outlet** & **Outlet Flow Q (kg/s)** \\
**(mm)** & **\(\mathbf{V_{\text{out}}}\) (m/s)** & **Outlet Flow Q (kg/s)** \\ \hline
1.5 & 16.243 & 0.309 \\
1.6 & 15.101 & 0.319 \\
1.7 & 14.281 & 0.334 \\
1.8 & 13.486 & 0.346 \\
1.9 & 12.826 & 0.353 \\
2.0 & 12.638 & 0.370 \\
2.1 & 11.763 & 0.367 \\
2.2 & 11.393 & 0.370 \\
2.3 & 11.033 & 0.370 \\
2.4 & 10.859 & 0.375 \\
2.5 & 10.665 & 0.379 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Simulation results for cooling hole diameter. the diameter is in the range of 2.0 to 2.3 mm, the outlet flow rate fluctuates within a certain range, and when the diameter exceeds 2.3 mm, the outlet flow rate increases monotonically. It is difficult to directly determine the size of the cooling hole diameter just from the line graph and data. Velocity contour diagrams of the cooling hole exits were used for further judgment.