Dynamic Modeling and Accuracy Evaluation Method for Complex Special-Shaped Components of Aviation Transmission

Aiqiang Zhang,Jing Wei,Hao Cheng,Bin Peng,Miaofei Cao 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.11

Due to designers' demanding pursuit of high power-to-weight ratio, most components in aviation transmission, including casing and shafting, are designed as special-shaped thin-walled structures. The assumption of large stiffness is no longer applicable. The casing is rich in geometric features and is usually modeled by the finite element (FE) method. However, the huge number of degrees of freedom (DOFs) poses great challenges to dynamic design. Model condensation provides an effective method for matrix dimensionality reduction. Taking the case of a helicopter main reducer as an example, a dynamic modeling method based on experimental modal analysis-FE method-substructure condensation is proposed. In addition, a method for measuring condensation errors is proposed to help determine the minimum number of nodes and their most suitable locations. Finally, the condensed models with the minimum number of nodes which meet the accuracy requirements are obtained. In previous studies, beam elements were usually used to simulate shafting flexibility, but the number of nodes and model accuracy were rarely discussed. And the selection of beam elements has not yet been unified. The optimal combination of beam element stiffness and mass matrix is determined based on regular shafting. Furthermore, the applicability of beam element method and condensation method in shafting modeling with different degree of regularity is compared. The research provides substructure models considering both accuracy and calculation efficiency for the overall system modeling of the aviation transmission.

Study of a hybrid modular exhaust turbocharging system and its application on an 8-cylinder marine diesel engine

Kun Zhang,Xinyu Huang,Sai He,Kangyao Deng,Yi Cui,Aiqiang Luo 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.6

For turbocharging engines, the structure of the exhaust system directly affects the flow and energy transfer process of the exhaust gas, which has a big influence on the turbocharger performance. To evaluate the performance of various kinds of exhaust systems, two indicators, “available energy loss coefficient” and “pressure wave interference coefficient”, are proposed to evaluate the steady flow loss and transient flow anti-interference characteristics. Two kinds of exhaust system modular, Modular pulse converter (MPC) and Modular multi-purpose pulse converter (MMPC), are analyzed and compared by the three-dimensional calculation. The results show that the MMPC structure has a smaller available energy loss and a better anti-interference performance in the exhaust process. To solve the problems of scavenging interferences and exhaust temperature discrepancy on a highly boosted 8-cylinder marine diesel engine, a Hybrid modular exhaust (HME) system is proposed. Effects of MMPC, HME and MIXPC (Mixed pulse converter) on the engine performance are compared by one-dimensional simulation. This is followed by an engine test for performance comparison between MMPC and HME, which shows that the HME system can effectively relieve the problems of scavenging interference, and the maximum exhaust temperature discrepancy of all cylinders is reduced from 60°C to 31°C under the rated condition.

A study on load-sharing structure of multi-stage planetary transmission system

Wei Sun,Xiang Liu,Jing Wei,Aiqiang Zhang,Xin Ding,Xinglong Hu 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.4

Unequal load distribution is a crucial factor in decreasing bearing capacity and stability of the planetary transmission system. In thispaper, a dynamical model of two-stage helical planetary gear transmission system is established based on lumped-parameter method andLagrange general function. Nonlinearity of gear tooth backlash and error is taken into account. Four load-sharing structures are proposedto study the load-sharing performance. A method to calculate dynamic sensitivity of load-sharing coefficient to errors is presented thatcan provide a reference to component precision determination in order to make planetary system have a better load distribution. Finally, anumerical method of load-sharing performance is validated by a test. These results provide fundamental basis for multi-stage planetarygear transmission system design.

Performance assessment and collapse prediction of a latticed tension-type transmission tower

Juncai Liu,Li Tian,Ruisheng Ma,Bin Zhang,Aiqiang Xin 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.1

This paper aims to provide a comprehensive performance assessment of a latticed tension-type transmission tower by performing both full-scale static tests and numerical simulations. In particular, a full-scale tension-type transmission tower was firstly constructed and tested for examining the performances under design loads and the ultimate capacity under an extreme wind load. The displacement and strain responses are investigated, and the failure process of the tension-type tower is presented. Numerical simulations are then performed in order to capture the failure process and estimate the bearing capacity of the experimental tower under the overload case. Moreover, Numerical simulations are also adopted to evaluate the influence of wind attack angles on the structural behavior of the tested tower. Experimental and numerical results demonstrate that this latticed tension-type transmission tower is designed with sufficient capacity to resist the design loads, and the buckling failures of the leg members at the bottom are the governing reason for the collapse of tower. In addition, the developed numerical model can accurately present the failure and structural response of the tension-type tower, and the influence of wind attack angles on the structural behavior is significant. This research is beneficial for improving the understanding on the bearing capacity and design of latticed tension-type transmission towers.

Influence of Screw Rotors Tip Angle on Mixing Performance for One Novel Twin-screw Kneader

Jing Wei,Dabing Chen,Dongming Zhou,Aiqiang Zhang,Yuliang Yang 한국고분자학회 2015 폴리머 Vol.39 No.3

Twin-screw kneader is an efficient polymer processing equipment. In this paper, the mixing performance of one novel intermeshing counter-rotating twin-screw kneader with different tip angles of the male rotor is simulated using the mesh superimposition technique (MST). Statistical analysis is carried out for the flow field using particle tracking technique, and distributive mixing performance is evaluated using the residence time distribution and segregation scale, while the dispersive mixing performance is estimated using the parameters such as shear rate, stretching rate and mixing index. The results show that the best distributive mixing performance is achieved when the tip angle is 0˚, while the optimal dispersive mixing performance is obtained when the tip angle is 20˚. The results in this paper provide a data basis for the selection of parameters and optimization of the performance for the screw rotors.

Study of Synchronization Characteristics of a Multi- Source Driving Transmission System Under an Impact Load

Jing Wei,Ruizhi Shu,Datong Qin,Teik C. Lim,Aiqiang Zhang,Fanming Meng 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.9

Multi-source driving transmission systems, in which the gear assembly is driven by multiple induction motors, are extensively used in new energy, aerospace, marine engineering, and in other fields. The multi-source driving system faces an even-load distribution problem, i.e., torque or speed synchronization issues. In this study, the synchronization characteristics of a multi-source driving transmission system under an impact load at different load change rates are studied. An accurate electromechanical coupling dynamic model of the system considering the flexible shafts, support bearing and meshing gear pair is established by applying virtual equivalent shaft elements. By considering the time-varying meshing and the coupling effects of the dynamic electric motor and the speed, torque and stator current synchronization characteristics are investigated using this model. Computational results show that the influence of the load change rate on the speed synchronization characteristics of the system is minor, but has a significant influence on the torque and stator current synchronization characteristics. The stator current root mean square value (RMS) can be chosen as a feedback signal to monitor the synchronization characteristics of the system. The proposed research provides the theoretical basis for the formulation of the synchronization control strategy for multi-source driving transmission systems.