Study on ice-induced load transmission in CP-mechanism

Abstract

Classification rules regarding the dimensioning of CP-mechanism has been found to be conservative based on experience. This thesis studies the load transmitted into CP-mechanism resulted from ultimate blade failure load (Fex) in heavy ice load condition, mainly focusing on the force on crank pin (Fcrp). Various FE simulations are carried out to investigate the load transmission in CP-mechanism for two hub models. Firstly, a simplification is come up with by using a remote force instead of blade geometry, in order to make the simulations more efficient. Then, initial simulations on the complete hub mechanism are implemented for both models. The results are compared with the results followed the procedure in DNV Classification Notes 51-1 and IACS UR I3. It is found that crank pin force from FE analysis is smaller compared to the result from rules calculation, meaning that the classification rules are conservative. There have been different versions of the application points of ultimate blade failure load and friction coefficient between blade flange, blade carrier bearings and crank disk. In order to achieve a clearer understanding on these factors, further research is implemented by studying three parameters, which are 1) application points of ultimate blade failure load, i.e. spindle arm, 2) geometry gap between blade flange and blade carrier bearings and 3) friction coefficient between blade flange and blade carrier bearings, crank disk and blade carrier bearings. Results show that different forces on crank pin are obtained from FE simulations when applying same spindle arm close to leading edge (LE) or trailing edge (TE). By running simulations of different geometry gaps and friction coefficients between blade flange, blade carrier bearings and crank disk, the purpose is to investigate the friction loss. The result indicates that the geometry gap has slight influence on the force on crank pin and friction coefficient affects the results significantly. Apparently, a bigger friction coefficient will cause more friction loss and smaller force on crank pin. However, the tendency of force on crank pin changing with friction coefficient differs with the relation described in DNV rules. In conclusion, more accurate rules could be suggested based on empirical formulas and FE simulations.