The assembly process of flareless pipe joints is very important for the sealing performance of hydraulic pipeline system. Based on the theory of contact mechanics, a theoretical model of the assembly process of pipe joints is established to simulate the extrusion molding process of flareless pipe joints. It is found that tightening torque is an important factor affecting the sealing performance of pipe joints. By comparing the changes of the contact stress between the sleeve and the pipe joint under different tightening tortures, combined with the mechanical transfer and deformation results of the contact surface, the results show that the fitting situation of the sleeve and the pipe is good when the expansion pressure is 180Mpa, and the sealing performance of the pipe joint is good when the tightening tortures are between 15N·m and 18N·m.

To study the influencing factors of liquid droplets on the cleaning effects of the scale layer, a three-dimensional droplet-impacting-a-blade model is constructed. The finite volume method and the volume of fluid method are used to numerically study the dynamic characteristics of a droplet impacting the fouling layer of a blade. The results show that under certain conditions, increased velocity and diameter of the droplet lead to an increase in the impact force of the droplet, and the greater the curvature of the blade surface, the smaller the vertical impact force of the droplet; likewise, the greater the impact force on cutting, the larger the corresponding spreading coefficient. The impact of liquid on the surface of the blade reduces the peak value of the droplet impact force. Finally, the increase in droplet diameter and velocity will improve the cleaning effect of the jet droplet. The larger the blade surface curvature, the wider the droplet cleaning area will be.

The assembly process of flareless pipe joints is very important for the sealing performance of hydraulic pipeline system. Based on the theory of contact mechanics, a theoretical model of the assembly process of pipe joints is established to simulate the extrusion moulding process of flareless pipe joints. It is found that tightening torque is an important factor affecting the sealing performance of pipe joints. By comparing the changes of the contact stress between the sleeve and the pipe joint under different tightening tortures, combined with the mechanical transfer and deformation results of the contact surface, the results show that the fitting situation of the sleeve and the pipe is good when the expansion pressure is 180 MPa, and the sealing performance of the pipe joint is good when the tightening tortures are between 15 and 18 N⋅m. Considering that the contact surface is a clearance fit, the mean value error of contact stress obtained by simulation verifies that the accuracy of the torsional relationship formula is very high.