Wyniki wyszukiwania - BazTech

1

Failure of magnetic fluid seals operating in water: preliminary conclusions

Matuszewski L.

Polish Maritime Research

|

2017

|

nr 2

113--120

EN

The article analyses properties of magnetic fluid seals installed in rotary sealing nodes which operate in the utility water environment. Seals of this type have been examined as a possible solution to the problem with ship manoeuvring propulsion sealing. The present analysis bases on laboratory durability tests of magnetic fluid seals exposed to longterm utility water loads, at different water pressures and shaft revolutions. The basic seal durability criterion was the number of revolutions made by the sealing node shaft until the appearance of water tightness loss (leakage). It was found that the main factor leading to the wear of the seal is the relative speed of the magnetic fluid with respect to that of the utility water, and this process is heavily affected by the pressure acting on the seal. The reported test results are presented in the form of diagrams showing the seal durability (time until water tightness loss) as a function of rotational speed. The curves shown in the diagrams are regular, with two different rotational speed ranges: the highspeed range, when the tightness loss is relatively fast, and the low-speed range, with a clear tendency to prolong the seal lifetime. These diagrams were given the name of durability curves of the MF seal operating in water. The results of the performed tests suggest formal similarity between the experimental data distribution concerning tightness loss processes occurring in magnetic fluid seals operating in water environment and metal fatigue processes. The article proposes a preliminary simplified durability model to describe the examined phenomenon.

2

Multi-stage magnetic-fluid seals for operating in water - life test procedure, test stand and research results. Part II Results of life tests of multi-stage magnetic - fluid seal operating in water

Matuszewski L.

Polish Maritime Research

|

2013

|

nr 1

39--47

EN

The edge criteria for magnetic-fluid seals durability research were described in previous article [24] and now the tests results are presented. The tests were made with three magnetic fluids using various magnets quantity in magnetic assemblies. If values obtained in the repeated test deviated by more than 10 % from results of the first test an additional control test was made for final characteristics. The characteristics are: critical pressure, critical motion velocity and working life of the seal. The test stands were prepared for particular seals dimensions and results of tests are presented in the form of tables, cross section draws and diagrams. In conclusion one can see that multi-stage magnetic-fluid seals could be efficiently used in water for rotating shaft seals in a limited range of motion velocity and cycles quantity. Nevertheless a particular applications can be provided by magnetic-fluid seals only.

3

Multi-stage magnetic-fluid seals for operating in water – life test procedure, test stand and research results. Part. I. Life test procedure, test stand and instrumentation

Matuszewski L.

Polish Maritime Research

|

2012

|

nr 4

62--70

EN

The edge criteria for magnetic-fluid seals durability research are critical for the seal’s technological usefulness. The magnetic fluid seal technology in water is much more difficult technological problem in comparison to gas or vacuum environment. There is always problem with immediate contact between magnetic fluid and the environmental uninspected liquids. In the paper are presented ways of experiments definitions carried out with multi-stage rotating magnetic fluid seal operating in permanent contact with utility water. The special test procedures have been elaborated and practically used, with the aim to define main characteristics of magnetic fluid seals. These characteristics were: critical pressure, critical motion velocity and working life of the seal. Some grades of commercial, silicon based magnetic fluids of hydrophobic properties were tested in sealing system. The test stand and its features as well as results of tests are presented in the form of tables, cross section draws and diagrams. In conclusion one can see that multi-stage magnetic-fluid seals could be efficiently used in water for rotating shaft seals in a limited range of motion velocity and work lasting.

4

Mathematical model of radial passive magnetic bearing

Matuszewski L., Falkowski K.

Polish Maritime Research

|

2010

|

nr 3

37-44

EN

In the article a mathematical model of radial passive magnetic bearings applicable to ocean engineering units has been presented. The application of the bearings in ship thrusters should increase durability of propulsion systems and give lower maintenance costs. The rotor of thruster’s electric motor is suspended in magnetic field generated by radial passive magnetic bearings. However the maintaining of axial direction of the rotor must be controlled with electromagnets equipped with a high-dynamic controller. The risk of application of the magnetic bearings results from very low stiffness of the unit in comparison with rolling bearings. Also construction of the bearing should be different due to gyroscope effect and high forces generated during ship manoeuvring. The physical model performs correctly if electromagnets are controlled properly; and, technological problem with sealing system seems more significant than power supply to electromagnets winding. The equations presented in the article are necessary to build algorithms of a digital controller intended for on-line controlling magnetic bearing in axial direction.

5

Ring thruster – a preliminary optimisation study

Matuszewski L.

Polish Maritime Research

|

2009

|

nr 1

43-46

EN

The ring thruster is a new type of propeller, for which there is no experimental data to verify analytical design calculations. A significant feature of the ring thruster is the absence of a shaft. Propeller blades are mounted to the ring rotating inside the housing, which has the shape of a nozzle. For this reason the ring thruster is closest, with respect to both the construction and principle of operation, to the Kort nozzle propeller. The absence of a shaft and no gap between the blades and the nozzle make it impossible to fully relay on results obtained from Kort nozzle propeller examination. What is more, the already existing computer codes developed for designing Kort nozzle propellers cannot be directly used for designing ring thrusters either. That is why for this purpose a new code determining hydrodynamic characteristics based on the theory of the vortex lifting surface will be used. When using the above method, some differences between calculated and experimentally recorded results are expected to be observed. To a significant extent, the level of the torque taken by the thruster will be affected by drag of the rotating ring to which the blades are fixed. Examining a propeller equipped with a rotating ring has revealed that the expected torque increment may reach as much as a few per cent, at the comparable level of axial force (thrust). At the present stage of ring propeller investigations there is no data available on how to shape the ring propeller blades. Possible comparison calculations, done using the existing computer code, will allow, the most, the shape of the blades to be determined for preliminary tests in the cavitation tunnel and on a selfpropelled model. And only the results obtained in these tests will provide opportunities for verification of preliminary design calculations. It should be stressed, however, that developing design procedures for this type of propellers will require additional optimisation calculations, with further experimental verification. And this should be the subject of separate investigations.

6

The application of magnetic fluids in sealing nodes designed for operation in difficult conditions and in machines used in sea environment

Matuszewski L., Szydło Z.

Polish Maritime Research

|

2008

|

nr 3

49-58

EN

Presented in article MF seals are being researched for sea technology purposes due to their excellent tightness and low resistance of motion. These features are most valuable for ring propellers and ship’s main propeller shaft. There are more reasons why technologists payf significant attention for various MF seals applications in their difficult operating conditions. For instance, an advanced pumping systems are designed with contactless (screw or centrifugal) fluid seal used as the first stage seal and then the MF seal as the main seal. Further parts of the article contain discuss of the properties of magnetic fluids in the construction of MF seals. Sample of the few systems of magnetic fluid seals are presented, which have been researched lately in our laboratory including sea conditions. The magnetic fluids used in our seals are colloidal suspensions of magnetic nanoparticles. Undertaken earlier various systems selection for sea-water purposes forced us to focus on double sealing systems, in which the MF seal is used as the second seal following a conventional system especially adapted to co-operation with MF systems. This solution successfully limits direct contact of the sealed liquid with the magnetic fluid, and the entire sealing construction secures absolute tightness of the system. Using this solution we also can reduce costs by elements high accuracy avoidance. Research and design activities are carried out in the AGH Laboratory of Seals and Magnetic Fluid Applications together with Deep Water Department of Technical University of Gdansk over the use of magnetic fluid seals in sea water environment. These activities are oriented on working out MF seals able to work effectively in machines in which low-pressure water flow takes place. The objects of experimental investigations are seals having two different nominal diameters: 50 mm and 220 mm and two research rigs of different construction had to be built up. Works are scheduled to be continued.

7

Ring thruster – a preliminary optimisation study of ferrofluid seal and propeller

Szydło Z., Matuszewski L.

Polish Maritime Research

|

2007

|

S 1

71-74

EN

The article reports the course of preliminary examination of a ferrofluid seal applied in liquid environment. A newly built research rig is described, and results of pressure tests performed for different shaft rotations are discussed. Other studies carried out in the past only referred to the gas environment, while the present examination aims at finding an answer to the question whether magnetic liquids can be successfully used in underwater applications. The obtained answer is positive, but further, more comprehensive investigations of the problem are necessary.

8

Ring thruster – a preliminary optimisation study

Matuszewski L.

Polish Maritime Research

|

2007

|

S 1

67-70

9

Experimental research on effectiveness of the magnetic fluid seals for rotary shafts working in water

Szydło Z., Matuszewski L.

Polish Maritime Research

|

2007

|

nr 4

53-58

EN

This paper presents course of research on ferro-fluidal seals used in water. The tests were carried out for a hydrophobic magnetic fluid and specially selected profiles of sealing lips at various linear velocities in sealing unit. Though the tests were preliminary their results showed that the research on application of magnetic fluids to seals working in liquid environment should be continued. From the point of view of development of ring drives the most important advantage of ferro-fluidal seals is their smallest drag as compared with seals of other types.

10

An electric ring thruster as auxiliary manoeuvring propulsion system for watercraft - construction analysis

Matuszewski L., Falkowski K.

Polish Maritime Research

|

2007

|

S 1

62-66

EN

The reported project aimed at examining properties and purposefulness of use of modern electromagnetic bearings for a screw propeller in a prototype version of a synchronous ring motor with rare earths magnets. Bearings of this type generate electromagnetic forces which keep the rotor in a state of levitation. The rotating machine with magnetic bearings can work in any environment which reveals diamagnetic properties (air, vacuum, water, liquid gases, etc.). However, a basic quality of the magnetic bearings is elimination of cooling installation and lubrication, which is necessary for proper operation of rotating machines with rolling and slide bearings, undergoing wear with time. Therefore the lifetime of the machine supported on magnetic bearings is incomparable with others. Also torque losses on this bearing are the smallest, compared to all known types of bearings. Ring thrusters can be used as the main drive for relatively small sea-going and inland vessels, and as manoeuvring drive for ships of arbitrary size, especially for AES (All Electric Ship) type vessels. This type of propeller is extremely useful for any types of abyssal vessels, autonomous and remotely controlled, and on submarines. It can also be used as effective generator of electric current for charging batteries in towing trains, barges for instance. The project consisted of three research tasks: 1. Designing, manufacturing and examination of a magnetic bearing on-line controlled by a digital controller, 2. Manufacturing a model of a ring thruster and examination of characteristics of a propeller mounted in the ring, 3. Examining the ferrofluid seal. A concept of the new thruster is a consequence of investigations carried out in Poland upon propellers and magnetic bearings in years 2001-2005.

11

The ring propeller with conical electromagnetic bearings and magneto fluid sealing system

Matuszewski L.

Marine Technology Transactions. Technika Morska

|

2004

|

Vol. 15

479-488

EN

Unique features and operating principles of the method of conversion of electrical energy into mechanical and vice versa are presented herein as applied in the marine vessel propulsion. A marine application has been chosen because of a working prototype for such has been built and is currently tested. It is able to convert the electric power of the prime mover into the rotative power of the propeller, support the propeller, and transmit the thrust developed by the propeller to the vessel's hull. In this new design, an electric variable-frequency-drive synchronous motor mover is integrated with a ring propeller in such a way that the motor's stator in the form of electric windings is built into a nozzle shrouding the propeller, and the motor's rotor in the form of permanent neodymium magnets is built into the propeller's ring. Similar idea had been patented in Ship Research Institute in 1963. The propeller is shaftless, with the ring joining the blades at the tips. The nozzle has radial cavity that accommodates the ring in such a way that the ring inner surface is an extension of the nozzle inner surface, so the nozzle maintains it's optimal geometry. Furthemore, the ring improves the nozzle-propeller hydrodynamic interaction and efficiency by eliminating the leakage losses between moving blades and the nozzle encountered in traditional designs, such as Kort nozzles. Most important innovation is that the propeller is supported by and able to transmit the thrust via two self-centered, self-aligned, tapered magnetic bearings that keep the propeller in state of levitation. Magnetic bearings, as compared with roller and journal bearings, have significantly higher efficiency and require less maintenance. The taper enables transmission of both, radial and thrust loads. The propeller's ring sides perform as the conical bearing's journal (race) surface. The nozzle ring cavity performs as the mating surface and contains two sets of electro-magnets. Magnetic curtain is provided ti seal the bearing from the environment. The curtain is yet another advancement in this design, providing efficiency higher than existing mechanical and labyrinth seals. Magnetorheological fluid is one of the most efficient medium in sealing systems which gives, among all others, relatively lowest torque losses and no leakage at all. Its application has not been tested yet due to preliminary stage of researching work, and is schedule for trials at late autumn of 2004.