The dynamic behavior of a reciprocating compressor transmission mechanism with joint clearance is studied in this paper. A transmission mechanism virtual prototype model is built under software ADAMS. Revolute joint between connecting rod and crosshead pin is modeled with clearance by contact model based on the so called Impact-function, and four processes of cylinder pressure load is simulated by the IF function. Cylinder pressure load, amplitude of joint clearance, crank speed and flexibility of connecting rod is taken as influence factors. Four different cases were simulated. Joint contact forces, accelerations of compressor block and journal centre path are used to analyze the dynamic behavior. The presented results show that these factors play a significant role of dynamic behavior of mechanisms.
The vibration characteristics and vibration response under different load cases in the underground powerhouse structure of Yixing pumped-storage power station were studied by establishing three-dimensional finite element model. The harmonic and transient analysis methods were proposed to study the vibration response of the powerhouse structure under various generating unit dynamic loads and in transient process. The numerical results were evaluated according to the related rules and regulations. The result shows that the vibration response of the power house structure is in the limit of the rules and regulations and there was little chance of resonance.
To identify damaged position of oil derrick, this paper presents a damage identification method for oil derrick using LMD and sample entropy to extract eigenvector and SVM to identify classes. Hammering vibration response signal of damaged derrick is decomposed into several PF components. The sample entropy of PF components is calculated and used as eigenvectors. SVM classifier is constructed based on eigenvectors of different damage location, and this method can identify damage position accurately. This method is verified by comparison with recognition result of LMD and information entropy.
Some components in Double horse head (DHH) pumping unit may occur cracking failure due to high cycle alternating stress, and this makes the research on dynamic stress simulation for them more interesting topic in its maintenance operation. This paper aims to improve the accuracy of dynamic stress simulation model through a parameter optimization method for the cable joints in DHH pumping unit. A series of cylinders was employed to model the steel cable, and the back horse head was also transformed to flexible body, then a rigid-flexible multibody dynamics model with cable was constructed to simulate the dynamic stress of components in DHH pumping unit. Stiffness and damping coefficient in cable joints have a significant effect on the model performance, and an unreasonable value may cause a strong vibrational and undesirable model response, therefore, a Memetic Algorithms based method was proposed to optimize them for improving the simulation accuracy using tested stress as objective function. Results show that the dynamic stress simulated from improved model is much closer to the experimental test compared with the original model, and these optimized parameters are also valid for the model in other working condition.
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