Doubt: 0.7R Pitch and Pitch/Diameter ratio

Thank you for the explanation. Answering your questions, the idea is to build a thruster that generates more thrust within this limit of D = 79 mm. This limit is imposed on all other teams in the competition. Regarding the bollard pull aft, we are free to design the propulsion system as we wish. Only one team in all the competition years managed to build an azimuth system. But to answer, yes, we can build an azimuth thruster. As our resources are not so high, we are primarily interested in advancing the competition with this idea of Kaplan thrusters inside a Kort No. 37 (our team).

 

OK, this change the whole focus of the technology. Propellers designed for Kort nozzles are somewhat different from regular propellers. However, you need to qualify if this is bollard thrust, maximum speed thrust or maximum average.

 

Ok, you should not be trying to build a Ka 4 70 in Kort 37 nozzle. You should be trying to build a 79mm ROV thruster. See this paper https://pdfs.semanticscholar.org/c658/79f388dc41e9bed175539fea704e41a18028.pdf and especially read the following reference: Lerbs, H. W., SNAME Trans. 1952. Moderately Loaded Propellers with a Finite Number of Blades and an Arbitrary Distribution of Circulation. Almost all modern propeller design methods are based upon Lerbs' paper but notice the limitations pointed out in the title..."Moderately Loaded". There are a couple of others buried in the text also.

In the above master's thesis, notice the propellers, both the original T200 and the proposed modified B series. While they fit the motor into the hub resulting in the need for struts, I assume you will use a shaft. In that case the you should have the nominal hub radius of 0.2r (or up to 0.3r), but the length of the hub should be the full length of the nozzle. Having the fairwater cap inside the nozzle just reduces the effectiveness of the "thruster tube". Notice the blade shape, especially the original T200 prop. P/D and blade width should be fairly constant tip to root (you may want to look into the possibility of blade taper root to tip with fwd skew, but I've never worked with something this small at this high of rpm). This will make the root length on the hub significantly longer than a Ka type blade. For maximum efficiency, the interior dead flat length of the No. 37 nozzle (generally between 0.4L to 0.6L of the nozzle length) should be extended so it is the same axial length as the blade root (trust me; one day I'll finish my paper) and aligned to the blade root. Pitch should be selected based upon setting the velocity at the propeller (Vp) equal to n*P so that motor power @ n = 0.5*rho*A*Vp^3 where A is the clear area at the nozzle/blade center (i.e. it is the nozzle area excluding the hub blockage; again it's in my unfinished paper). Number of blades and EAR is then selected based upon the torque that the motor can deliver at n and cavitation considerations (again, see Lerbs). Because you want superior performance in reverse, I wouldn't deviate too much from a symmetrical blade section (indeed, as a thruster, the blade section shapes should be elliptical ogives of the minimum thickness to support blade bending and cavitation considerations).

Edit for spelling and stuff.