To improve the intershaft seal performance of the dual-rotor turbofan engine and extend the life of the intershaft seal, a compliant cylindrical aerodynamic intershaft seal structure is proposed, which avoids the problem of leakage increase after tooth wear of intershaft labyrinth seal. According to the proposed seal structure, the force condition of the floating seal ring is analyzed, and an aeroelastic coupling method for the floating seal ring eccentricity is presented. And the leakage characteristics, with different seal structures and operating conditions are calculated and compared when the two rotors are under homodromy/counter-rotating condition. The results show that, for the dual-rotor cylindrical hydrodynamic gas film seal, the hydrodynamic effect under homodromy condition is enhanced greatly while the hydrodynamic effect is significantly weakened under counter-rotating condition; the rotational direction of rotors, seal width, rotor circular precession eccentricity, rotational speed and rotor radius all have pronounced influence on the seal performance. For the application of hydrodynamic form of compliant cylindrical intershaft seal, the seal performance under homodromy condition is better than that under counter-rotating condition.
To improve the weaknesses of large leakage and wear of dual-rotor intershaft labyrinth seal in aero-engines, the cylindrical gas film seal of metal rubber with a compliant feature is proposed to substitute this conventional seal. According to the dual-rotor operating condition, an analysis method of gas film pressure is presented considering the complex condition of rotor tilt, centrifugal expansion effect, and rotor circular precession. The characteristics of gas film pressure distribution are computed and comparisons are conducted in a complex operating state that the tilt rotor is in forward/backward circular precession under a homodromous/counter-rotating condition with/without the influence of centrifugal expansion. Besides, the formation mechanism of the gas film pressure caused by rotor rotational direction and circular precession direction is revealed. Also, the influence of rotor speed and seal ring speed on gas film pressure is analyzed when the rotor is tilted. The results indicate that for the dual-rotor cylindrical gas film seal with high rotating speed, the rotor tilt and centrifugal expansion effect have significant influence on the gas film pressure distribution, and the rotors’ rotational direction as well as rotor circular precession direction determines the maximum gas film pressure distribution area. The maximum pressure under a homodromous condition with backward precession is the highest; the maximum pressure under a homodromous condition with forward precession is the lowest. The former is 1.33% and 1.68% higher than the latter, respectively, with/without consideration of centrifugal expansion. The study method, which is generally suitable for the cylindrical gas film seal with single-rotor/dual-rotor, lays the foundation of performance analysis under complex operating conditions.
A compliant cylindrical gas film seal has the potential to adapt to the complex operating conditions of a dual-rotor aeroengine, with radial runout and eccentricity, due to its special structural characteristics. To accurately investigate the seal performance of a compliant cylindrical gas film seal on dual-rotor shafts, an aeroelastic coupling method is proposed. This method analyzes the performance of a compliant cylindrical intershaft gas film seal by taking the centrifugal expansion effect into consideration. The seal performance under homodromy and counter-rotating conditions, with and without the centrifugal expansion effect, is calculated, and various performance parameters are compared and analyzed. Furthermore, the influence mechanism of the direction of rotation of the two rotors on seal performance is revealed. The results show that seal performance under homodromy condition is greater than under counter-rotating condition, and for an aeroengine under homodromy condition, it is advantageous to apply the compliant cylindrical intershaft gas film seal. The effect of centrifugal expansion (in large-diameter and high-speed rotors) and rotor eccentricity on the performance of a compliant cylindrical intershaft gas film seal, as well as the impact of inner and outer rotor speed on leakage rate, are analyzed and presented in this study. The proposed aeroelastic coupling method provides a promising guidance for the performance analysis of the compliant cylindrical gas film seal in single and dual- rotor systems.
This paper introduces the composition and operating principle of the image test signal generator about HDTV based on CPLD, it explains the logic function design in CPLD and the hardware configuration of this system in detail. The signals produced by this generator accord with the parameter standard of video signal interface about our national High Definition Television. Furthermore, programming with hardware description language VHDL makes it easy to expand software functions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.