| High temperature oil pumps need to adopt dual mechanical seals for transporting high-risk process media,such as high temperature,high pressure,flammability and explosion.However,in the process of use,oil leakage often occurs,the operation and maintenance costs are high,and the service life is not up to the standard.In view of the existing problems of dual mechanical seals and combined with process media,this paper takes the new dual mechanical seals（main seals are upstream pumped spiral groove liquid film seals and secondary seals are contact mechanical seals）as the research object,and studies the influence of non-Newtonian characteristics of fluid,viscous-temperature relationship,operation parameters and structural parameters on the flow field,temperature field and thermal deformation of sealing rings.A three-dimensional model of moving ring-liquid film-stationary ring was established for a new type of dual mechanical seal.Combining the power law model of non-Newtonian fluid and Vogel viscous-temperature model,the effects of operating parameters（rotational speed,buffer pressure,flow rate and temperature of flushing fluid）and structural parameters（groove depth,groove number and groove angle）on sealing performance and end friction heat were studied.A three-dimensional model of dual mechanical seal was established.Considering the friction heat,stirring heat and heat conduction,the influence of operation parameters and structure parameters on the temperature field and thermal deformation of moving and stationary rings of spiral groove liquid film seal was studied.The effects of rotational speed and buffer pressure on the sealing performance and the temperature rise of the flushing fluid were also studied experimentally.The results show that the pressure of inner and outer diameters of the seal face increases,which inhibits the cavitation in the spiral groove.The larger the liquid power law index is,the better the upstream pumping function of the spiral groove can be realized.The upstream umping volume increases with the increase of the power law index.The viscous thermal power of the seal face increases with the power-law exponent.Considering the viscous-temperature relationship,the pressure distribution is similar to that of power law index is 0.94,and the leakage and viscous thermal power decrease.The heat transfer of the pump body and shaft is mostly carried away by the flushing fluid,and the friction heat of the sealing end surface is the main heat source of the sealing ring.With the increase of power-law index,the temperature of the end face of the sealing ring increases.When considering the viscous-temperature relationship,the temperature of the end face of the sealing ring is between power law index is0.94 and 0.96.When the flow rate of flushing liquid increases,the maximum temperature of sealing ring decreases,the temperature rise of flushing fluid decreases,and there exists an effective maximum of flushing flow rate.The taper deformation of the sealing ring is larger than the waviness deformation,and the waviness deformation is very small.Thermal deformation of sealing ring leads to convergence clearance.The larger the power-law index,the larger the deformation of sealing ring.Considering the viscous-temperature relationship,the deformation law of sealing ring is similar to that of power law index is 0.98.Choosing the appropriate auxiliary system and reduce the buffer temperature is conducive to reducing the deformation of the sealing ring.Under the condition of this paper,PLAN32和PLAN55 system is selected.The flushing pressure is 1.1MPa,the buffer pressure is 0.8MPa,the flushing temperature is 40℃,and the flushing fluid flow rate is 12L·min-1. |
