Applications and design peculiarities of modern controllable-pitch propellers

Abstract

Object and purpose of research. This paper discusses controllable-pitch propellers (CPPs) of various designs. The purpose of this study was to summarize the findings of CPP studies in Russia and abroad, as well as to identify current challenges in Russian CPP design and manufacturing. Materials and methods. This paper relies on the test data obtained at Deepwater Tank and cavitation tunnels of Krylov State Research Centre. It analyses the results of computational studies for CPP hydrodynamics and strength obtained as per the latest techniques of CFD and FE analysis. Main results. The history of CPP design and manufacturing in Russia clearly shows that our country has considerable expertise in design of controllable-pitch propellers that can operate in the harshest conditions. Analysis of global shipbuilding experience has shown that CPPs not only ensure optimal operational conditions for “engine-propeller” system in the conditions of variable hydrodynamic load on the propeller, but also feature better cavitation and vibroacoustic performance because the skew of CPP blades can be moderate and high: actually, it can be significantly higher than for fixed-pitch propellers (FPPs) because FPP blades in reversal conditions do not have to operate their trailing edges forward, which reduces the risk of high stresses and damage of skewed blades in crash-stop scenarios. Analysis of CPP test results obtained at Krylov State Research Centre hydrodynamic and cavitation laboratories, as well as the findings of foreign computational studies enabled justified assessment of CPP advantages. It also highlighted the challenges that require dedicated studies and special consideration in design of skewed CPPs, so as to improve their performance in partialcavitation and cavitation-inception conditions. Conclusion. Currently, Russia has all the pre-requisites for increased production and wide application of modern CPPs. Controllable blades with moderate and high skew have a certain potential in terms of improving their vibroacoustic performance as compared to FPPs. However, to design these blades correctly, with consideration of their possible operational risks, it is necessary to use state-of-the art computational and experimental methods, as well as to rely on the experience of full-scale trials.