Design And Performance Study Of Horizontal Shaft Flow Based On Optimal Design Flow Rate

With fossil fuel consumption and environmental pollution increasingly intensified, tidal current energy, as a kind of abundant renewable clean energy, has the characteristics of high power density, strong predictability and smooth velocity, etc. Many research institutions have conducted researches and tests on horizontal axis blade.Blade is a key component for power generation device of horizontal-axis tidal current energy to capture energy and the design flow velocity, as a blade design preference, has a direct impact on the shape, the working performance and actual capture efficiency of the blade. At present, there is no suitable method to select blade design velocity for fixed-pitch blade: Wind turbine blade design is usually determined by the probability distribution density of energy contained by wind speed; due to the small flow velocity in the design of blade capturing tidal current energy, the maximum is generally selected, which leads to the low capture power when the blade with variable velocity works under off-design condition and unpredictable power changes of the design blade, especially under the actual condition that most flow velocity is low, it is of significance for greater use of tidal current energy to select appropriate design flow velocity to do fixed-pitch blade design.This paper uses blade element momentum theory and fluid dynamics to analyze velocity-induced changes of the fixed-pitch blade with variable velocity and then get the different capture power under different velocity changes. It establishes the mathematical model between power capture under variable flow velocity and the design velocity. Combined with test of the actual current velocity changes, it puts forward the goal of maximizing the total energy captured within a month and a half cycle of current velocity variation, and then uses MATLAB calculation iteration to get the right design flow velocity to realize the maximizing of total energy captured by blade with variable velocity, rather than the largest output power just in the design points. Furthermore, it takes the average flow velocity of the largest tidal current as the design flow velocity to make contrast with design method in this paper and uses the modified Wilson optimization design method and MATLAB software procedureto calculate blade shape parameters. On basis of above-mentioned, it makes theoretically comparative analysis of performance prediction of two different design velocity on the size and shape of the blades, the starting characteristics, thrust, torque and power changes, which provides a theoretical comparison data for experiment.Due to the complexity of operational environment called flow field, a lot of assumptions and simplifications are frequently made on the calculation model in the design of blades, and to a great extent, these factors affect the calculation accuracy. Therefore, it needs to actually model and process the above two kinds of design blades and set up off shore blade performance test platform to acquire the experiment data, which is going to be compared with the theory. Through the actual experiment, it finds that power capture based on the blade design with the optimal velocity is better than that of the compared blade during the most time period of the tidal current velocity changing, and the total energy captured in the cycle of one month and a half has improved by 8%, which proves the rationality and validity of the design method in this paper, and also has a certain guiding significance to the theory and engineering practice in the blade design with variable velocity.