Estimate the Value of Propeller Trailing Edge Cutting with Numerical Lifting-Surface Theory
|School||Wuhan University of Technology|
|Keywords||Propeller Numerical lifting-surface theory Vortex lattice method Cutting Matching between hull-propeller-engine|
The propeller may be overloaded which caused by some reasons when ship has been serviced for a period of time. As a result, the rated revolution of the engine cannot be achieved, or the engine may be on overloaded operation condition. It will not be in the optimum matching between the propeller and the engine. The speed of the ship may be lowed and the engine was operated on half-duty on purpose in some conditions. The running condition would be deteriorated and at last the parts of the engine would be damaged if the revolution were reduced too low. The propeller must be redesigned or be modified in this situation. People usually modify the propeller rather than change the propeller because it will be more easily and economical. The propeller’s torque could be lighted through edge cutting. The engine’s revolution will be reduced also. The running condition becomes better than before. So, It is valuable and important to find out how to select the style of propeller trailing edge cutting and estimate the value with numerical theory.Numerical lifting-surface theory has been developed as a practical tool in predicting marine propeller’s hydrodynamic performance because it is easily being computed and accurate for application. Based on the Green’s formula and the assumption of the propeller blade’s thin sections, a lifting-surface method of propellers with the vortex lattice and equal source panel distributions on the mean camber surface has been introduced for the prediction of steady propeller’s hydrodynamics in this paper. An approximate kurta condition was applied.The primary purpose of this paper is how to solve the overloaded propeller’s condition. The style of propeller trailing edge cutting and shave on the pressure surface is adopted. The propeller’s actual effect pitch will be reduced which cause the propeller’s torque down. The loading of the engine will be lowed and the revolution will be raised at the same time. It is effective when the propeller trailing edge cutting is performed outer radius. There are different thrusts and torques corresponds to difference trailing edge cutting value at different advance coefficients. Combined with the real hull’s resistance and the real engine’s power and revolution, the matching point between hull-propeller-engine and the value of trailing edge cutting can be calculated. The result shows this theoretical method is feasible.