Research On Optimization Design And Mesh Characteristics For Promote Gearbox Used In Jack-up Offshore Platforms

The core component of the jack-up offshore platforms is the promote gearbox.The design and mesh characteristics analysis of the promote gearbox will directly affect the working performance of the entire offshore platform.This work took the promote gearbox of a jack-up offshore platform as the research object.The analysis and scheme design of the configuration for the promote gearbox were carried out.The teeth-distribution optimization model of the promote gearbox was established.Then the geometric design was completed and the mesh characteristics analysis model was established.The mesh characteristics of the promote gearbox under different working conditions was researched.The transmission system was optimized from the perspective of macro parameter optimization and micro modification to improve the mesh characteristics of the promote gearbox.The endurance fatigue and type vibration test of the promote gearbox were completed.Moreover,the research has important academic significance and engineering value for the design and development of the promote gearbox transmission system.The main contents and conclusions of this dissertation are shown as follows:(1)The existing promote gearbox configurations were summarized.The configuration of 4-level NGW planetary transmission was analyzed by using graph theory method and adjacency matrix method and the configuration isomorphism was excluded.The appropriate configuration was selected.At the same time,considering the singlestage and inter-stage constraints,the optimization design model with the smallest volume and the smallest inter-stage strength difference was established.After optimization,the volume was reduced by 10.21% and the gap between the minimum contact strength and bending strength of each level was greatly reduced.According to the gear geometry and working conditions,the strength and efficiency of the promote gearbox were calculated.(2)Considering the flexible planet carriers and the box body,the mesh characteristics analysis model of the promote gearbox transmission system was established.Then the mesh characteristics of the promote gearbox including contact performance,tooth root stress,transmission error and mesh stiffness were carried out under normal lifting and pre-load lifting condition.The results showed that,under the two working conditions,the maximum contact stress of the gear tooth surface of the promote gearbox was too large,and the peak value of the tooth root stress was distributed at both ends of the tooth width direction,and there was an obvious eccentric load phenomenon.The p-p value of transmission error and the mean value of the mesh stiffness were too large.Therefore,the optimization of the transmission system was needed to improve the mesh characteristics of the promote gearbox.(3)Based on the study of the influence of the pressure angle on the mesh characteristics of the promote gearbox,the modification scheme of the gear pairs at each level was put forward.It could be found that after the optimization of the pressure angle,the preferred combination of the pressure angle of the promote gearbox was 25 °,26 °,27 ° and 26 °,and the root stress,the p-p value of transmission error and the average value of mesh stiffness were reduced.After modification,the maximum contact stress of the tooth surface was reduced.The peak stress of the tooth root was distributed in the middle of the tooth width.The p-p value of the transmission error and the mean value of the mesh stiffness were greatly reduced.Finally,the mesh characteristics of the promote gearbox were optimized.(4)The promote gearbox test platform was built,and the endurance fatigue and type vibration test was carried out.The color and magnetic particle inspection of gears of the gearbox were proposed and the vibration and transmission efficiency of the gearbox were obtained.The test results showed that all the gears were not damaged and the vibration level was within the allowable range.The transmission efficiency was close to the theoretical calculation results and the design rationality of the promote gearbox was verified.