Optimum wind turbine blade design with xfoil

[ginobee2000]

my dessertation topic is optimum wind turbine blade design with xfoil. and the aim of this project is to find a series of airfoil that gives a good efficiency and also how the angle of attack changes with rotation...pls has somebody got an idea about...and also how best can i start this dessertation...

pls i need help on this...all help will do... thank you

 

[Topher925]

Usually the best place to start is with a literature review.

This isn't a PhD dissertation is it?

 

[ginobee2000]

it is an MSC AEROSPACE ENGINEERING DESSERTATION.

 

[FlexGunship]

Are you talking about variable blade geometry or variable axial geometry?

 

[ginobee2000]

no even the geometry because am only optimizing in a 2D form. well am looking into now is how to look up for the typical windspeed and the typical rotational speed of the turbine..
i read some journal adviced to use the weibull distribution to find the wind speed with respect to the area at which the turbine will be placed... but when i looked the distribution there is proper understanding.

pls if someone have got any idea on how to find the typical wind speed and rotational speed i will be very much pleased...

thanks

 

[malay_555]

i think your topic is to design a blade,
1) for that you have to first decide your operating range of the wind turbine means a speceific value of wind speed, it may be assumed or selected for perticuler location on the basis of atmospheric data,
2) then you also have to fix your rpm of turbine based on the aplication of the wind turbine (for example if it is conected with generator then you have to fix torque and rpm as per generator load where torque helps in finding length by moment calc and rpm helps in getting angle of attack of airfoil at diff location)
3) Now it will give you a complete picture of diff velocities at diff location of the span. (total incoming air velcity is the vector sumation of the wind speed in axial diraction and the tangential velocity at any location due to rotation)

so on the basis of these data you can select or design diff airfoil shape for diff location over the blade span that gives you the complete model of the blade

 

[ginobee2000]

thank malay. well i have trying to get the annual(2009) mean wind speed for the calcualtion of the windspeed using linear regression and last weibull distribution..but i can't get the wind speed.

it hard to come by this information. pls do u have any help. anyway i got a data for 2007 which i found on a previous project. but am tryin to get 2009

 

[dtango]

If I understand what the topic of your dissertation is it's really related to general propeller blade design. There are loads of resources out there on the internet regarding propeller blade design that you can dig up. There should be loads of reports on the NASA Technical Reports Server ( ntrs.nasa.gov ) on the topic.

In general if you're working with a fixed pitch wind turbine propeller the efficiency of the propeller is a function of propeller advance ratio, thrust coefficient, and power coefficient and there is a combination of the three of these that gives you the highest efficiency for a given propeller. For your case one way you can start the analysis is by determining what you think the advance ratio will generally be given the atmospheric / wind conditions are like for the geographic site you are designing for. Advance Ratio is defined as

J = V/nd where

J= advance ratio
V= velocity
n= revolutions
d= prop diameter

Starting with velocity (wind speed) and revolutions (whatever you need the turbine to turn the generator at) will give you some target constraints you need to start your turbine blade design from.

Be sure to look into Blade Element Theory as a starting place to model blade geometry to get the right thrust and power coefficients that you want.

I have no clue if you have to account for wind direction or not which makes a difference on the aerodynamic results, nor if wind turbines are variable pitched or not, etc. Hope that helps!

 

[ginobee2000]

Thanks dtango, for sometime nw I have been looking through the BEM theory it similar to the turbine blade design. But my worry homework to get the average wind for a year. I have got the mean wind speed data of 2008 and I have done all the necessary statistics, graphs and after that I used weibull to find the distribution based on 2 parameters that is K and C. Nw the only thing left is homework to find the average wind speed from the wiebull because the design is for a specific site called shropshire. And I need the wind speed to find the Tip speed ratio of the blade..any help will do. thank you very much for all ur support.

 

[Cyrus]

Hello Ginobee,

Could you please avoid abbreviating the words you are trying to convey, it is very hard to follow.

Thanks

 

[ginobee2000]

Pls what word don't u understand so I can write it again...thank you

 

[Cyrus]

Pls what word don't u understand so I can write it again...thank you

I mean spelling things out, such as Please for Pls.

 

[ginobee2000]

Oh ok yeah u ar right pls means please..

 

[ginobee2000]

Thanks dtango, for sometime nw I have been looking through the BEM theory it similar to the turbine blade design. But my worry homework to get the average wind for a year. I have got the mean wind speed data of 2008 and I have done all the necessary statistics, graphs and after that I used weibull to find the distribution based on 2 parameters that is K and C. Nw the only thing left is homework to find the average wind speed from the wiebull because the design is for a specific site called shropshire. And I need the wind speed to find the Tip speed ratio of the blade..any help will do. thank you very much for all ur support.

 

[dtango]

Thanks dtango, for sometime nw I have been looking through the BEM theory it similar to the turbine blade design. But my worry homework to get the average wind for a year. I have got the mean wind speed data of 2008 and I have done all the necessary statistics, graphs and after that I used weibull to find the distribution based on 2 parameters that is K and C. Nw the only thing left is homework to find the average wind speed from the wiebull because the design is for a specific site called shropshire. And I need the wind speed to find the Tip speed ratio of the blade..any help will do. thank you very much for all ur support.

ginobee - see if this helps. You're really asking for statistics help ;).

http://www.talentfactory.dk/en/tour/wres/weibull.htm

What they say is to multiply each wind speed interval by it's related probability and then add them all up. That will give you the average wind speed. Cumulative distribution function (CDF) basis of analysis. Someone with a better stats background then me will need to explain. I get all turned around dealing with it ;).

 

[ginobee2000]

Wind Speed (m/s)

0.5
1.0
1.5
2.1
2.6
3.1
3.6
4.1
4.6
5.1
5.7
6.2
6.7
7.2
7.7
7.8
8.2
8.7
9.3
9.8
10.3
10.8
11.3
11.8
12.3
12.9
13.4
13.9
14.4
15.4
17.0

this is my wind speed

 

[ginobee2000]

90
175
459
586
901
667
743
606
787
589
619
446
537
332
322
50
223
219
125
107
43
50
28
12
17
8
6
4
3
1
1
this is the frequency column of the wind speed above

 

[ginobee2000]

Probability Probability(%)

0.010273973 1.027
0.019977169 1.998
0.052397260 5.240
0.066894977 6.689
0.102853881 10.285
0.076141553 7.614
0.084817352 8.482
0.069178082 6.918
0.089840183 8.984
0.067237443 6.724
0.070662100 7.066
0.050913242 5.091
0.061301370 6.130
0.037899543 3.790
0.036757991 3.676
0.005707763 0.571
0.025456621 2.546
0.025000000 2.500
0.014269406 1.427
0.012214612 1.221
0.004908676 0.491
0.005707763 0.571
0.003196347 0.320
0.001369863 0.137
0.001940639 0.194
0.000913242 0.091
0.000684932 0.068
0.000456621 0.046
0.000342466 0.034
0.000114155 0.011
0.000114155 0.011

this the probability i found for the above.

 

[ginobee2000]

0.005284932
0.020552511
0.080859452
0.137643105
0.264540183
0.235003288
0.30541032
0.284681644
0.41592411
0.345869406
0.399834429
0.31427726
0.409934521
0.272937352
0.283624658
0.044520548
0.209518174
0.21862
0.132123288
0.119380731
0.050500457
0.061657534
0.03617242
0.016207123
0.023958356
0.011744292
0.009160548
0.006341918
0.004932603
0.001761644
0.001937808

when i multiplied the speed by it related probability this is what i got therefore the total of this is given as 4.724914612m/s
please dtango am i right..

 

[dtango]

4.7 m/s looks about right intuitively looking at you wind speed values and their distribution. Someone who's more versed in CDF's and statistics should comment but that value feels about right for the average basis your data and distribution.

 

[ginobee2000]

Thanks so much dtango...am still doing more research to find out how best I can make the calculations of the speed. So far all the journals and papers I have read don't tell u homework to make such calculation. They only do elaborations on it and how do the weibull distribution only..

 

[ginobee2000]

hi dtango.

i have been able to calculate my average wind speed from the data. i read a book by author name MR PATEL. it a good book. what i did is by plotting my distribution and calculating the power output based on the new derived probability i used from the weibull probability density function. i also calculated this based on 2 parameters K AND C.

from the scale factor C according to patel u can calculate the average wind speed of the site. the relation for calculating this is

U(Average mean wind speed)=0.9C

based on this formula the average wind speed, U is 6.3m/s

Now i decided to use 2m rotor radius, with a swept area of the rotor calculated as 12.57m2(diameter=4m). i also decided to use a tip speed ratio(TSR) of 5 for 3 bladed rotor since i want to reduce the noise.

i calculated the revolution per mins for the turbine using the formula:
(V*TSR*60)/(D*pie) which i got 150.4rpm i then change this rev per mins and i got 2.51 rev per second.

now it time to find the rotational speed which i used this relation to calculate
W=2*pie*(Rev)=2*3.142*2.51= 15.8m/s

now i want to calculate the tip speed of the blade but i really don't kno if what i have done nw is ok..

because when i calculated the tip speed of the blade i got 1.99m/s when i used the relation below
TSR= (ROTATIONAL SPEED X TIP SPEED)/WINDSPEED, V

I MADE SUM CHANGE OF SUBJECT AND I GOT THE 1.99M/S

AM not sure if am right.. can somebody help if anyone has the idea.

thanks very much

 

[dtango]

Hmm ginobee - not sure what you are trying to do with your math there. If you're wanting to estimate tip speed of the blades its the following basic relationship:

TSR = tip speed / wind speed

You have two knowns and one unknown there already. You already know:

TSR = 5 (per your decision)
wind_speed = 6.3 m/s (per your weibull distribution calcs)

Rearranging the above equation we get:

tip_speed = TSR * wind_speed

Plugging with your known values we get

tip_speed = 31.5 m/s


I'm not sure where you're getting your equations and how you're doing the unit conversions etc but something is wrong with it all.

For instance what you calcuated as "rotational speed" at 15.8 m/s, that's actually in radians/sec. How do I know?

TSR = rotational_speed (rads/s) * Radius (m) / wind_speed (m/s)
TSR = 15.8 * 2 / 6.3
TSR = 5.0158

TSR=5.0158 is awfully close to your specified TSR of 5.

Also from our two equations of TSR we can infer that

Rotational_speed(rad/s)*Radius(m) = tip_speed(m/s)
tip_speed = 15.8 * 2
tip_speed = 31.6 m/s

This 31.6 m/s is awfully close to the 31.5 m/s I calculated for tip speed.

Hope that helps!

 

[ginobee2000]

the rotational speed i calculated is not in radians per second...

because i read some website and a journal which gave me the relation as (V*TSR*60)/(D*pie). i used this relation to find the RPM(revolution per minutes) which is 150.4.
after getting this since i want to find the rotational speed i used this formula w=2πN where i N=RPM calculated.

i was finking that the 150.4 rpm was revolution per minutes so have to change it to revolution persecond to get 2.51

 

[ginobee2000]

the formula i used to calculate the blade tip speed was this TSR= (Ω*tip speed)/V where Ω is the rotational speed=w

may be am misunderstanding myself.. i wish u can start from calculating the rotational speed

 

[dtango]

ginobee:

The TSR equation you have is incorrect.

First it doesn't match the TSR equations I know of:

TSR = tip_speed / wind_speed
TSR = rotational_speed * radius / windspeed

2nd using your equation the units are wrong - here's why using your equation

TSR = rotational_speed (rad/s) * tip_speed (m/s) / wind (m/s)

Your left with TSR with dimensions of rad/s which is invalid because TSR is a dimensionless ratio.

Here are a couple of other references you can use to check your equations against:

http://www.kidwind.org/Presentations/WindTurbineBladeDesign..March.08.ppt
http://www.asr.org.tr/pdf/vol10no1p147.pdf
http://www.nrel.gov/docs/fy00osti/27143.pdf
http://practicalaction.org/docs/technical_information_service/energy_from_wind.pdf
http://www.bringaboutgreen.com/building-hawt-wind-generator/whats-tip-speed-ratio-tsr
http://www.raeng.org.uk/education/diploma/maths/pdf/exemplars_advanced/23_Wind_Turbine.pdf


Also I'm pretty confident your equation for rotational speed give you unit of radians/sec and not m/s.

Hope that helps!

 

[ginobee2000]

Hi dtango, thanks for ur help.. I appreciate it..well all the necessary calculation is done nw.. Hw do we go about the blade geometry. Since my blade is 2m I decided to make the number of stations along the blade up to 10 starting from 0.2.. How is the chord calculated... Nw am tryin to analyse the airfoil using xfoil. Xfoil is abit complicated. I have got all the tutorials but I fink I need someone to help me understand it..I appreciate everybodys help on this tanx..

 

[ginobee2000]

hi am now calculating my blade geometry. can somebody help with chord calculation and the blade set angle along the blade with respect to the intervals thanks. the one i did is below and am not sure if it correct so didnt continue.
my blade calculation is below:

r/R r(stations) c Airfoil
[-] [m] [m]
0 0 0 MH102 WITH HIGH LIFT
0.04 0.4 6.523157208 CL=1.46
0.08 0.8 3.261578604 "
0.12 1.2 2.174385736 "
0.16 1.6 1.630789302 "
0.2 2 1.304631442 "
0.24 2.4 1.087192868 "
0.28 2.8 0.931879601 "
0.32 3.2 0.815394651 "
0.36 3.6 0.724795245 "
0.4 4 MH104 NEXT HIGH LIFT
0.44 4.4 CL=1.30
0.48 4.8 "
0.52 5.2 "
0.56 5.6 "
0.6 6 MH106 NEXT HIGH LIFT
0.64 6.4 CL=1.17
0.68 6.8 "
0.72 7.2 "
0.76 7.6 "
0.8 8 MH108 NEXT HIGH LIFT
0.84 8.4 CL=1.23
0.88 8.8 "
0.92 9.2 "
0.96 9.6 MH110 NEXT HIGH LIFT
1 10 CL=1.03

 

[dtango]

Hi ginobee -sorry, I've had some issues with my browser that kept me from getting to this site! I've gotten that fixed now. I hadn't a chance to analyze your request yet. I'll let you know if I come up with anything!

 

[HorstClaude]

Hey... i just finished my final thesis and completed a wind turbine blade design software based on the BEM and integrated in XFOIL, you might want to check it out! please cite me!

download from:

qblade.de.to

cheers

David

 

[ginobee2000]

thank you dtango..sorry for your browser.. may be u have to get the google browser...

hello horstclaude. i just checked your blade design software and it was very nice...i will site u very well...it is good.. i will talk to my supervisor about it.

cheers..zehr gut..ich bin gluklich für u.. du bist sprechen deutch!.. hurray cia

 

[ginobee2000]

hello horstclaude i tried using ur program. i fink it a little bit complicated.. do u have a tutorials for this program.. thanks

 

[HorstClaude]

You can download the Guidelines from the download section, they explain the most basic functionalities. Otherwise have a look at the XFLR5 Guidelines, as they explain the Functionalities of XFLR (which is part of my software). Download the XFLR package at sourceforge, the Guidelines are included there. Other than that if you have any specific questions just ask me. It might be a bit tricky to configure QBlade for the first time, try doubleclicking the graphs to reset them. other than that you might want to try to hold ctrl while creating a blade - that enables you to have full 3D control with the mouse...

have fun

Horst

 

[ginobee2000]

well. i have already analysed my airfoil.. which are from mh102 to mh110.

i have the polars saved in txt file which i copied to MS Excel from which i was able to make the graphs for the lift coefficient now if i want to copy this polar to QBlade how do i do that or in which format is the file suppose to be. because i tried doing this yesterday and it wasnt working

 

[HorstClaude]

ok... you should export a polar from QBlade, then you see which format you need.
bring the polar in the right format and create a foil which has exactly the same name as the polar in the file that you created... then the polar should appear in qblade.