چكيده به لاتين
Surface-Piercing Propellers (SPP) are a type of propellers, half of which operate in water and the other half in air. These propellers are generally more efficient than other ones, so their good performance is very important. However, despite the good performance of these propellers, they are unfortunately less efficient at low speeds than other systems. One way to increase the efficiency of SPPs is aeration. In the present study, two experimental and numerical perspectives have been discussed in this regard. From an experimental point of view, using a water tunnel of the Hydrodynamics Research Institute of Iran University of Science and Technology, a number of different tests have been performed on different types of propellers under different conditions. The most important issue regarding the results is the improvement of the trust coefficient. A special innovation that has been done in the experimental discussion of this research is the aeration system of this propeller, which all its design and construction stages were done in the Applied Hydrodynamics Research Institute of the University of Science and Technology. The experiments were performed at different injection air flow rates and different immersions. After the tests, it is observed that the highest rate of performance improvement is related to low drowning as well as low β / α ratio (in immersion 0.25). The point discussed in this project is that at 0.25 immersion the amount of aeration at high β / αs is less effective, so the best comparison is the performance improvement at 0.4 immersion, in which immersion results in an 80% improvement in propeller performance at β / α is equal to 0.3. Also, the lowest performance improvement that actually causes negative propeller performance is related to deep drowning and consequently low β / α ratio. Also, the effect of injected air flow rate (Q) in different immersions and in different advance coefficients was shown and the optimal immersion and advance coefficients were obtained to improve the thrust coefficient of the submerged propeller. At working points, the thrust coefficient increases with increasing injection air flow at different immersion coefficients and different propeller advance coefficients. Then, using the mixture model, the injected air flow upstream and downstream of the propeller was simulated and a direct relationship between the injected air flow rate and the downstream flow profile thickness was obtained. The experimental results also confirm that we will finally conclude that this method can be used in future analyzes.
