## 2 Design of Self-Inhaling Internal Cooling Structured Grinding Wheel
### Simulation of Flow Field in Grinding Zone
This is because the abrasive grains are not staggered radially, which clearly affects the cooling efficiency of the coolant and its ability to carry away the grinding debris. For Layout 2, before entering the grinding zone, the coolant experiences a noticeable velocity partitioning due to the centrifugal force from the rotating wheel, with coolant at the outer edges moving faster. Once it enters the grinding zone, the speed is reduced due to obstruction by the abrasive grains. Additionally, the rotation of the wheel affects the flow direction of the coolant. Layout 2 has a significant drawback: the coolant's flushing effect on the rectangular abrasive grains in the circumferential direction is insufficient, only affecting one side. It does not exert an equal effect in all directions. For Layout 3, the characteristics of the coolant before entering the grinding zone are similar to those of Layout 2. However, as it approaches the grinding zone, the velocity decreases. This is clearly because the coolant encounters obstruction, and its flow into the gaps and grooves between the abrasive grains is not smooth. Additionally, due to the abrasive grain configuration, there is significant interference with the direction of coolant flow in the grinding zone. Combined with the centrifugal force from the rotating wheel, the velocity partitioning of the coolant is more pronounced in Layout 3 than in Layout 2. Some grooves between the abrasive grains do not receive coolant flow. The disadvantage of Layout 3 is that the flushing effect on both sides of the parallelogram-shaped abrasive grains is highly uneven, creating a one-sided force on the grains. This raises the requirement for greater stability of the abrasive grains. Furthermore, the coolant's flushing of the grooves is not uniform and is concentrated on one side, which can lead to a decrease in the efficiency of coolant usage. For the structure of Layout 3, simply analyzing the average outlet coolant flow rate is not sufficient to assess its performance. For Layout 4, which uses a distribution based on the spiral theory, the abrasive grains are staggered, eliminating any radial obstructions. From the velocity contour, it can be seen that before entering the grinding zone, the coolant velocity experiences a partitioning due to centrifugal force, which follows the expected pattern. Upon entering the grinding zone, there is a slight decrease in velocity, as the abrasive grains provide some resistance, and the coolant loses part of its kinetic energy as it flushes the grains. The advantage of Layout 4 is that the coolant velocity throughout the entire grinding zone is uniform, with nearly no areas left uncovered by the coolant, providing thorough and even flushing of the entire grinding zone. This demonstrates that the use of the spiral distribution theory for the abrasive grain configuration in end face grinding wheels indeed offers advantages in maintaining a uniform and orderly coolant flow. By performing postprocessing on the simulation results, velocity vector diagrams could also be obtained. These vector diagrams can reflect the quantity of coolant at a given location to some extent. They can validate the patterns observed in the velocity contour maps and also help to discuss issues that are not reflected in the velocity contour maps. The velocity vector diagram for Layout 1 is shown in Figure 15a. When the coolant enters the grinding zone, it flows through the gaps and grooves between the abrasive grains. As the flow space becomes smaller, we can see a local concentration of velocity vectors as the coolant just enters the grinding zone. This corresponds to a higher average velocity in this area on the contour map. More coolant flows radially outward quickly, and because the abrasive grains are not staggered radially, some areas between the grains do not receive coolant flow. This phenomenon becomes more pronounced towards the outer edges, where the coolant velocity is faster due to the absence of obstacles. The velocity vector diagram for Layout 2 is shown in Figure 15b.