Förrotation till omrörare
The primary function of a mixer is to keep a fluid in constant motion. All mixing applicationsrequire varying degrees of small-scale turbulence and bulk flow. The performance of asubmersible mixer is measured by the thrust that it produces, while the strength of the bulkflow is dependent on the total amount of installed thrust.In a mixer, the fluid quickly flows past the propeller, and as a result, the current is mainlyaxial. The fluid will also obtain a rotating velocity, or a swirl, though this is significantly lessthan that of the propeller. During the process, the total amount of energy increases in the formof static pressure and kinetic energy. The static pressure creates the mixer?s thrust. Thekinetic energy is caused by the fluid?s rotation and is usually not desirable. Therefore, toobtain maximal static pressure, or thrust, the rotation of the fluid should be minimised wherepossible. This can be achieved by creating a pre-swirl of the water opposite the propellerrotation.The main objective of this master thesis is to develop and construct a set of guide vanes,capable of producing the pre-swirl needed to eliminate the rotational velocity of the fluid, andverify this through testing.To be able to carry out tests in small tanks, scaled down models of the 4620 mixer weredeveloped, and manufactured with SLS technique in Duraform PA. Furthermore, a test rigwas constructed with the purpose of measuring the mixer?s thrust. Mixer thrust test resultsreveals that by applying guide vanes to a mixer, the mixer thrust increases by approximately10-20 % compared to a normal mixer, depending on whether or not a jet ring is used. Themixer?s efficiency increases by 1-5 % compared to a normal mixer. Tests with the mixer?s jetshows that by using guide vanes, the jet becomes more stable, and obtains a higher velocity.After evaluating seven different concepts, a full scale prototype was manufactured with theSLS-method. Performance tests with this prototype, at ITT Flygt in Lindås, revealed that themixer thrust increases by 5-15 % depending on the propeller blade angle and whether or not ajet ring is used. The mixer efficiency increases by up to 7,5 %.