reducing the rotor noise in helicopters
It is seen that the noise in helicopters is mainly due to the formation of vortices formed by the blade tips. when the vortex formed by a blade is hit by a succeeding blade, noise is produced. to eliminate this noise or to reduce this noise a lot of modifications to the design of the rotor blades have been made. but if we can remove the chance of the blade coming in contact with the vortex by offsetting the blades, i believe that the noise level can be considerably reduced. thus we will have a shaft where the blades are fixed one below. there will only be one blade per plane. the unbalance in masses can be taken care of by adding correcting masses on the other side.
rebellionofrebelNot only the blade tip vortices, but the major contributor is the Gas turbine Engine and its rotating connecting elements like Gear box !!!!! The blade tip vortices after a point cannot give so much reduction in noise as compared to the reduction offered by modifying the Gas Turbine exhuast !!! In fact i do not think that BLad tip vortices contribute to noise as much as the GT engine and its connected rotating elements!!!!!
arun_267thanks. but can u giv some more details on hw the noise can be brought down. cos im doin a project on tat.
rebellionofrebelIf u ra trying to reduce noise due to blade tips ,expect not much reduction.. on Turbine side noise youcan have muffled noise by designing the exhaust area in a way that promotes noise muffling...
FYI, the latest US army tanks and even the older US Army Abrams tanks have a Gas Turbine as their engine and not an IC engine!!! Yeah its true .. THe Army has been able to reduce noise effectively. Normally their tanks have Turbines in range of 1600kW and so....
CE DesignerArun i see the point you are making but i doubt that will make much of a difference because the strong vortices formed at such high rotational speed will still be cut by successive blades.
rebellionofrebelPoint well taken .. THats y i had commented that its the Gas Turbine that makes then noise!!!!!
arun_267ya but wat if the offset is suficient enuf to dodge the vortices. i am sayin tat the blades are in completely diff planes
Devil26I feel we simply cant assign the cause of the noise to the gas turbine..obviously it contributes to the noise factor in a big way.. probably a flow analysis around the chopper blades has to be carried out and based on trial and errors of different shapes, we can reach upon the most favourable shape of the blades..
arun_267hmm thanks.. can u suggest any topics for my miniproject
CE DesignerLook at your surroundings, challenges faced in your home or community, talk to people you know who may have a problem to solve, you must find a good project in one of those places. For one of my projects i went to a paraplegic hospital to look at the challenges they faced and i found a project there.
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