Study On The Performance Of Self-pumping Hydroynamic-static Double-face Mechanical Seal For Nuclear Reactor Coolant Pump

The sealing performance of the nuclear reactor coolant pump is an important indicator for the safety evaluation of metal molten salt reactors.A double-face self-pumping mechanical seal was proposed for certain type of coolant pump for metal molten salt reactors.In this paper,the self-pumping mechanical seal with the spiral groove on the rotating ring end and the liquid ring groove and the drainage hole in the static ring section is taken as the research object.The influence of the structural parameters of the end face of the static and rotating ring and the operating parameters of the nuclear reactor coolant pump on the sealing performance is discussed.The significance of each parameter was studied by orthogonal experiment and analysis of variance.Based on the results of single factor analysis and orthogonal test,the variation of the rotational speed of the end face of the rotating static ring and the change of the sealing clearance with the rotational speed after disengagement are calculated and analyzed.Finally,the disengagement speed of the end face of the small-diameter self-pumping mechanical seal was studied and compared with the theoretical calculation value,so as to verify the disengagement of the mechanical seal of the nuclear reactor coolant pump.The main work and conclusions are as follows:?1?Using the fluid simulation software Fluent numerical simulation to analyze the pressure distribution and velocity distribution of the end face flow field,and discuss the end face structure parameters?groove number Ng,helix angle ?,ratio of groove width to face width ?,ratio of groove width to ridge width ?,ring groove width B,ring groove depth H,spiral groove depth hg?and operating parameters?rotating speed n,pressure difference ?p?on sealing performance?opening force Fo,leakage rate Q?.The results show that the end face opening force increases with ratio of groove width to face width,ratio of groove width to ridge width,ring groove width,rotation speed and pressure difference increases.As the ring groove depth increase is firstly sharply reduced,When the ring groove depth reaches 800?m,the opening force changes gently and remains basically unchanged.Furthermore,opening force increases sharply with the increase of the depth of the spiral groove,when the depth reaches 40 ?m,the opening force remains substantially unchanged.The leakage rate increases with the increase of the ratio of groove width to face width,ratio of groove width to ridge width,the rotation speed and the pressure difference,and decreases with the increase of the ring groove width and the number of grooves.The influence of the ring groove depth on the leakage rate is firstly reduced rapidly,after 800?m,the slowdown is reduced,which corresponds to the change trend of the opening force.When the spiral groove is shallower,the depth of the spiral increases the leakage rate significantly.After the depth is 40?m,the leakage rate remains basically unchanged.?2?Orthogonal experiment and analysis of variance were used to study the influence of various influencing factors on the sealing performance.Based on the results of single factor and orthogonal test,based on the principle of comprehensive balance method,the geometric parameters of the selected structural parameters were established,and the disengagement speed of the self-pumping mechanical seal was quantitatively studied.The results show that under the conditions of the structural parameters and working parameters selected in this paper,the sealing end face is disengaged at the spindle speed of 213.7r·min^-1,and then the influence of the small change of the sealing gap on the spring is neglected.After the end face is disengaged,it is concluded that the change rule of the sealing gap with the spindle speed is hm=4.31775×10^-6n²+0.00592n-1.35393.?3?The disengagement speed of the small-diameter self-pumping mechanical seal end face was tested,and the feasibility of the numerical calculation method of the self-pumping mechanical seal disengagement speed of the nuclear reactor coolant pump was verified.The results show that under the test condition,the disengagement speed of the self-pumping mechanical seal end face is about 1900r·min^-1,which has certain error with the theoretical calculation results,but considering the processing and assembly error of the test piece,this paper studies The calculated value still has some reference significance.Through numerical simulation and experimental research,it is proved that the self-pumping double-end mechanical seal meets the requirements of the sodium-cooled fast reactor nuclear coolant pump sealing performance,which is suitable for the sodium-cooled fast reactor nuclear coolant pump,and also provides theoretical basis for the design of the fast-reactor nuclear coolant pump mechanical seal.