Tuesday, February 21, 2017

Posted by February 1, 2017

Maritime Propulsion

New Bronze Propeller for Arctic Ops

  • Photo: Tevo Oy
  • Photo: Tevo Oy
  • Photo: Tevo Oy
  • Photo: Tevo Oy

Finnish company TEVO Oy said it has developed a cost-effective alternative for steel propellers.

The result of a large product development project, TEVO said it can now design and manufacture an optimal bronze propeller construction for 1A Super (PC-6) class. A bronze propeller designed for 1A Super class with optimized efficiency and noise characteristics has been verified in full-scale sea tests in the northernmost part of the Baltic Sea, particularly in harsh ice conditions of the northern part of the Gulf of Bothnia. The full-scale sea tests enabled to demonstrate durability of TEVO's bronze propellers in arctic ice conditions and prove that with the help of appropriate design a propeller can be optimized emphasizing, for example, ice-going properties or energy efficiency. The high quality material used and refined by TEVO together with sophisticated design and optimization knowhow facilitates a high quality end product for arctic conditions.
TEVO's propeller unit in Turenki (about 100 km from Helsinki) has nearly 65 years of experience and has delivered more than 4,000 bronze cast propellers. Also in the past decades over 2,000 propellers were designed at the propeller plant, some of their models are still being manufactured. At the moment TEVO, being a top firm in bronze propeller manufacturing, has allocated resources heavily in one's own product development. The aim of the nearly three-year-long project was to develop an arctic bronze propeller product family of one's own to meet the challenges of arctic shipping.
Two internationally recognized top expert organizations, Arctic Aker Technology Oy and VTT Technical Research Centre of Finland, both having a large experience in arctic navigation related design and product development, were invited to participate in the R&D project which was a part of Arctic Seas program pursued by Tekes – The Finnish Funding Agency for Innovation.
State-of-the-Art Tools Kit, High Quality Material and Expert Knowhow
During product development project TEVO's ice-going design and design abilities related to bronze propellers rose to an international level. As a design software TEVO has now in use an internal code based on traditional potential flow theories which has been further enhanced within the product development project together with the specialists of VTT. By it means we can quickly find such kind of a propeller which would meet the design criteria in a rough level. For more exact hydrodynamic studies TEVO has in its disposal a modern CFD-based software which allows to define design more closely. In addition to class rules, a Nastran-code operating in Siemens NX-environment can be used for strength dimensioning and Siemens NX CAD tools for other modeling. The Magmasoft simulation software is being utilized in casting design, it allows to simulate casting process beforehand.
Based on the material studies carried out in the course of product development TEVO said it was able to prove that the bronze propeller raw-material used by its propeller plant exceeds the requirements set by the class which makes it possible to use significantly better dimensioning parameters.
This fact together with top design and optimization knowhow enables TEVO to make still lighter propeller constructions which would improve energy efficiency of bronze propeller and thus improve environment friendliness also, the manufacturer said.
From Design to Prototype and Verification 
Design of the test propeller was based on dimensioning of both ice and noise characteristics. The bronze propeller was manufactured enough strong to operate in the ice conditions of the northern part of the Gulf of Bothnia. However, its form had to be such that it would create noise as little as possible when navigating in open sea. Experimental propeller was fabricated completely from start to finish at TEVO's propeller unit in Turenki.
The purpose of the full-scale sea tests was to verify performance of TEVO's bronze propeller in arctic conditions. A multi-functional vessel of 1A Super (PC-6) class equipped with two podded propeller systems was used for the execution of the full-scale sea tests.
Full Scale Sea Tests 
Design results were verified with full-scale sea tests in northern part of the Gulf of Bothnia in the springtime of 2016. That point of time coincided ideally with the moment when the ice conditions were considerably more challenging compared with the typical winter in that sea area. There were pack ice banks of even over 7 meters in some places and in any case the ice thickness was about 80 cm at the surveyed spots. When reversing in the above-mentioned conditions with the propeller ahead we could evidentially reach harder ice load than the ice class 1A-Super would require and, consequently, TEVO was able to observe bronze propeller's performance in extreme conditions.
The prototype propeller performed without damage also through the most challenging parts during the full-scale sea tests. In addition, the tests proved also bronze propeller's energy efficiency and lower noise level.
Summary of the Project 
Thanks to the product development project TEVO's propeller unit has improved its bronze propeller's ice dimensioning and computation abilities to an international top level and thus it can act as an expert partner to its customers in challenging questions related to propeller selection. TEVO has been able to build around itself a large specialist network due to which TEVO will be able to react to and support its customers and also ensure the very best and optimal propeller option for arctic conditions, be it a bronze or steel one. Furthermore, the full-scale sea tests have proved that with the proper design optimization and TEVO's knowhow in bronze propeller fabrication one will be able to reach a better efficiency compared to a traditional solution. TEVO has at its disposal an optimization tool developed during the project by which a bronze propeller can be optimized according to customer needs with the emphasis either on ice-going conditions or energy efficiency. Proper configuration can increase bronze propeller's strength and also influence its noise and energy efficiency level. Full-scale sea tests did show that bronze trial propeller could generate alone thrust even by 18 percent more in the same power-speed use point than the vessel's original steel propeller.
Customers and Markets
TEVO is aiming at arctic shipping markets with its new special product. Owing to the optimization tool developed by TEVO together with its cooperation partners the ship operators will be provided for their disposal a bronze propeller performing ideally in open sea conditions and also fulfilling completely the class rules for operation in one-year ice.
The manufacturer believes that there is a demand for this special product. It will serve as TEVO's cutting edge product when marketing propeller design to new potential clients. Shipping companies willing to invest in environmental friendliness and energy efficiency will be one significant business when they are going to replace their propellers with new ones. With the help of TEVO retrofit design a new bronze propeller can be designed for an existing vessel. For example, in terms of efficiency it can be optimized to be considerably more efficient than the present solution. Once a vessel's initial data would be accurate enough, TEVO's propeller design will be able to prove by means of computation the benefit brought by a new bronze propeller, even the payback time of the investment can be calculated for the customer.
SiemensCADGulf of Bothnia