| As a kind of new-typed and advanced seal in the end of the shaft,dry gas seal was applied widely in the rotary fluid machineries owing to the outstanding seal performance long-life service and low abrasion among the various non-contact seals.Recently,with the development of the fluid machineries in the field of high-temperature high-speed and high-pressure,a battery of higher-level requirements was put forward in the end seal of the shaft of the rotary machineries.Based on the conditions of high-temperature and obvious vibration in the flue gas turbines and combustion gas turbines.A kind of cylindrical dry gas seal with the adaptive character was presented.The pressure of cylindrical gas film and the steady characteristics of the cylindrical dry gas seal were mainly studied.Based on the characteristics of the cylindrical spiral groove seal,the steady-state Reynolds equation was established in the condition of the slip-boundary.With the background of the relevant researches,the gas film thickness function with the influence of the structure parameters of the spiral groove was deduced.In addition,the approximate analytical solution of the gas film pressure distribution of the cylindrical spiral groove was solved under the control of the film thickness equation and pressure boundary conditions by using the PH linearization method and the small parameter iteration method.By the MATLAB software program,the three-dimensional graph of pressure distribution of cylindrical gas film in particular condition was obtained.Furthermore,steady characteristics of cylindrical seal were put forward in the specific conditions with the corresponding formulas.The specific values of buoyancy,leakage and friction torque of the gas film were achieved.In the end,the pressure distributions and steady characteristics of non-groove cylindrical seal with eccentricity ratio and spiral groove cylindrical seal without eccentricity ratio were carried out.Furthermore the results were compared with the conclusion of the cylindrical spiral dry gas seal.On the basis of the above results,variation laws between the gas film pressure distribution and the number of groove,groove depth,eccentricity and seal width were analyzed.Meanwhile,buoyancy,seal leakage and friction torque under the condition of the above parameters were also discussed.According to the above research results,part of the optimized structural parameters of spiral groove was proposed.The results showed that with the increase of the groove number;groove depth;eccentricity ratio,the peak value of pressure increased gradually but the seal length had tiny influence on the pressure.However,the influence of the number of grooves on the buoyancy was not obvious in different eccentricity ratio.The friction torque increased but leakage decreased to a stable value.The buoyancy decreased due to the groove depth.But leakage of gas film and the friction torque increased.With the increase of the seal length,the buoyancy force increased and the leakage reduced.The buoyancy decreased with the increase of spiral angle.But leakage of gas film and the friction torque increased.It is recommended that the optimum number of groove was 12~18,the seal width was 0.03~0.045 m and the spiral angle was 40°~50°,which provides a basis and reference for the subsequent theoretical research and engineering application. |
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