The Research Of The Dynamic Characteristics Of The New Bearing Layout Counter-Rotating Dual-Rotor System

The dynamic characteristics were researched about the counter-rotating dual-rotor system in this paper. The criteria were discussed for the aero-engine design of the counter-rotating dual-rotor system in the future. The results had directing significance on theory and reference valuable on engineering for the dynamic design of the counter-rotating dual-rotor system. The main contents and results were obtained as follows:1) The finite element models were constructed basing on a certain aero-engine with a four bearings dual-rotor or four five bearings dual-rotor structures making use of ANSYS, the dynamic characteristics was researched about the dual-rotor system with five bearings or four bearings. The researched results were showed that the strain-energy distribution was larger for the four bearing dual-rotor structure than the five bearing, the strain-energy distribution was unreasonable and should be optimized for the four bearing dual-rotor structure. The dynamic characteristic was the most optimal for the low pressure rotor with the 1-1-1 supporting program within the five bearing dual-rotor structures; The four bearings program is feasible to some degree in the respect of the strain energy distribution;2) The influence of the parameters to the critical-speed was researched, including the stiffness of the bearing, the speed ratio between the low and high pressure rotor. The conclusion is drawn as follows: the critical speed is increased as the stiffness of the bearing, but obviously in a certain range. Some mode shape for the small stiffness of the bearing would disappear when the stiffness became too big.3) The test bench is designed and processed with the similar dynamic characteristic to the real dual-rotor structures based on the criteria of the similarity for the dynamic characteristic. The finite element models with different supporting programs were constructed, calculated and analyzed, the researched result shows that: the two test bench models with the low-pressure rotor supporting program 0-1-1 and 1-1-1 were similar with each other, which were better than the 1-0-1 low-pressure rotor supporting program. Therefore, the one with the 0-1-1 low pressure rotor supporting program is the best one referred the test bench model, the four supporting program is feasible to some degree;4) The dynamic characteristics were optimized on the aspect of the strain energy distribution, the summit value of response for displacement and the critical speed margin. The optimization with multi-objective function and single-objective function is applied on the optimization for the strain energy distribution of four bearing counter-rotating dual-rotor structure. The result shows that, after the optimization, the value of objective function is descended from 0.401 to 0.379, decreased about 5.5 % for the real four support dual-rotor structure; and descended from 0.47 to 0.44, descended about 6.4% for the four support test-bench?The result of the optimization is meaningful to the dynamic design for the dual-rotor structures of the aero-engine;5) The unbalance response is calculated for the real dual-rotor structures and the test bench dual-rotor structures respectively, the unbalance response is analyzed on the respect of sensitivity, summit response and so on. The result shows that because the sensitivity of the four bearing program to fan plate, the property of the aero-engine would tend to be declined.The dynamic characteristic of the counter-rotating dual-rotor system was researched and the supporting program of the four bearing dual-rotor structure is optimized and the sensitivity is analyzed, the researched result of the four supporting program is meaningful in engineering.