Parametric Effect Investigation on Aerodynamic Interaction Characteristics for Tandem Rotors in Forward Flight

An iterative free-wake computational method is developed for the prediction of aerodynamic interaction characteristics between the twin rotors of a tandem helicopter.Here the mutual interaction effects between twin rotors are included,as well as those between the rotor and wake.A rotor wake model,blade aerodynamic model and rotor trim model are coupled during the process of solution.A new dual-rotor trim approach is presented to fit for the aerodynamic interaction calculations between tandem twin rotors.By the present method,the blade aerodynamic loads and rotor performance for the twin rotors under the interactional condition are calculated,and the comparisons with available experimental data are also made to indicate the capability of the proposed method.Then,the effects of such parameters as the longitudinal separation and axial separation between twin rotors on the aerodynamic interaction characteristics are analyzed.Based on the investigation,the conclusions are obtained to be of benefit to the configuration design of tandem rotors.Furthermore,the performance comparison between the tandem rotors and a single rotor is conducted.It is shown that the strongest interaction does not appear in a hover state,but in a low-speed forward flight state.

Temperature and thermodynamic deformation analysis of the rotors on a twin screw multiphase pump with high gas volume fractions

The pressure increasing process within a twin screw multiphase pump, under the condition of high gas volume fractions (GVFs), induces large temperature and pressure changes that cause the rotors to deform. Rotor deformations heavily influence the backflow of the multiphase fluid through clearances within the twin screw multiphase pump and these deformations may even lead to pump failures. An accurate temperature and pressure distribution on the screw rotors need be obtained before the deformation analysis can be carried out. By means of small temperature and pressure sensors embedded into the groove at the root of the rotors, the temperatures of 12 points on the rotors and the pressure distributions of a twin screw multiphase pump under high GVFs conditions were recorded. Temperature test results were adopted to perform a heat transfer analysis for determining the temperature distribution on the screw rotors. Then deformation analyses, including thermal deformation, force deformation, and total deformation, were conducted according to the pressure and temperature distributions. Deformation analysis for different materials was also conducted under the same boundary conditions. A material was suggested for the manufacturing of rotors in a twin screw multiphase pump under the condition of high gas volume fractions.