## 3 Results and Discussion
### Lubrication Performance under Different Discharge Pressure
#### 3.2.3 MDMT Calculation Results  
The calculation results of MDMT under different discharge pressure are shown in Figure 15. Since \(\delta_{\rm bal}\) in this calculation is always greater than 0, the coordinate value on y axis is set from 0 to +\(\delta_{\rm lim}\). If \(T_{\rm t}\) remains negative under the condition that \(\delta=+\delta_{\rm lim}\); it indicates that wear occurs at leading side and the contact force will be involved to balance the negative \(T_{\rm t}\). In this case, the \(\delta_{\rm bal}\) is set +\(\delta_{\rm lim}\). Figure 14: The water film stiffness under different discharge pressure. Under the discharge pressure of 0.8 MPa, the MDMT curve of SCT always coincides with the straight line of \(\delta_{\rm bal}=+\delta_{\rm lim}\) in a whole period \(\gamma\). This result suggests that the water films at leading side cannot afford sufficient bearing capacity to bear the torque generated by water films of trailing side even when \(\delta=+\delta_{\rm lim}\) and contact force from the leading side participates in balancing the negative \(T_{\rm t}\). The MDMT curve of SSLT coincides with the straight line of \(\delta_{\rm bal}=+\delta_{\rm lim}\) in a whole period except a small region which \(\varphi_{\rm gr}\) ranges from \(-2.49^{\circ}\) to \(1.51^{\circ}\). In this small region, the hydrodynamic lubrication is established for the leading side and \(T_{\rm t}\)=0 or \(\delta_{\rm bal}\) is available. However, in this region, \(\delta_{\rm bal}\) is too small; in other words, the water films at leading side are too thin when the gate-rotor gets balanced. Contact is still prone to occur under shock. The MDMT curve of MCT is always kept in the region of the \(\delta_{\rm lim}\). Figure 15: The micro deflecting movement trajectory (MDMT) curves under different discharge pressure. 0\(\rightarrow\)+\(\delta_{\rm lim}\), which represents the MCT has good self-regulating ability and contact will not happen in both sides in a whole period \(\gamma\). It suggests that the gate-rotor is floating in the water films of both sides and meshing with the screw. In addition, the MDMT curve of MCT is relatively far away from the line of \(\delta_{\rm bal}\) = +\(\delta_{\rm lim}\), which proves that water films at leading side still have enough thickness to remain at full fluid hydrodynamic lubrication and to resist some impact. Under the discharge pressure of 1.2 MPa, only in a very small region about 3.4\({}^{\circ}\) (\(-\)2.55\({}^{\circ}\)\(\sim\)0.82\({}^{\circ}\)) the MDMT curve of SSLT does not coincide with the straight line of \(\delta_{\rm bal}\) = +\(\delta_{\rm lim}\). The MDMT curve of SCT is still the straight line of \(\delta_{\rm bal}\) = +\(\delta_{\rm lim}\), which is consistent with the situation under 0.8 MPa. The MDMT curve of MCT remains in the region of 0\(\rightarrow\)+\(\delta_{\rm lim}\), but the curve gets closer to the line of \(\delta_{\rm bal}\) = +\(\delta_{\rm lim}\) than that under 0.8 MPa. This suggests the MCT still has good self-regulating ability to prevent contact. However, as \(\delta_{\rm bal}\) is achieved, the water films at leading sides get thinner than those under 0.8 MPa. Under the discharge pressure of 1.6 MPa, both MDMT curves of SCT and SSLT completely coincide with the straight line of \(\delta_{\rm bal}\) = +\(\delta_{\rm lim}\). This illustrates contact occurs at leading sides throughout. For the MCT, it cannot keep full fluid lubrication in the whole period but only in a 17.71\({}^{\circ}\) range including the region of \(-\)27.2\({}^{\circ}\)\(\sim\)\(-\)22.49\({}^{\circ}\) and the region of \(-\)8.49\({}^{\circ}\)\(\sim\)4.51\({}^{\circ}\). It can be inferred that all the MDMT curves move towards the straight line of \(\delta_{\rm bal}\) = +\(\delta_{\rm lim}\) when the discharge pressure increases. Compared to the SSLT and SCT, the MCT can keep full fluid lubrication in a wider pressure range and has the best self-regulating ability.