- View Source
> Your question is very interesting because I am myself studyING about

This is correct - the formula for calculating discharge, needs an additional

> that wheel

> Do you know the works of Clemson university about that wheel ?

> (papers of NADIM M.AZIZ)

> I have disvovered tAat there is a real question about Qmax and that

> question is also in relation with the true Qmax which is lower that

> the product of nozzle section (Width * throat) * Speed of water

>

> A MENDRET

> FRANCE

term, called the coefficient of discharge and denoted by C. Thus Qmax = C x

nozzle crossectional area x speed of water. This coefficient allows for losses

due to friction and losses due to contraction of the water stream as it passes

through the nozzle.

I do not know the value of this coefficient for crossflows, but have seen values

of 0.95 to 0.97 quoted for Pelton turbines.

Regards,

Max Enfield

Planetary Power - View Source--- In microhydro@yahoogroups.com, Max Enfield <max@p...> wrote:
> brijesh mainali wrote:

mathematical

> >

> > Hi friends,

> > I will be grateful to you, if any of you could suggest me the

> > expression [formula] for the maximum flow [Qmax] and runner

length[L] in a

> > cross flow turbine.

can be as

> >

> > Regards

> > Brijesh Mainali

>

> One of the nice things about a crossflow is that the runner length

> chosen to suit the application and is independent of the runner

diameter.

> However, usually the runner length does not exceed 3 x runner

diameter.

>

runner and has a

> At maximum flow the inlet stream occupies the full width of the

> thickness [T] designed to be 9% of the runner diameter.

sqrt [2 x g x

>

> First calculate the velocity in m/sec using the usual formula V =

> H] where g [gravitational constant] = 9.8 m/sec^2 and H is the net

head in

> metres. Then Qmax = V x L x T. Using metric values throughout,

Qmax is given

> in m^3/sec.

Excuse me for the previuos mail incorrect

>

> Regards,

>

> Max Enfield

> Planetary Power

I am searching about crossflow and the works of Nadim m Aziz in

Clemson university

I cannot undestand the large lamda admission ( 90 degrees) and the

fact of the Q that couls pass in the nozzle is >> than the real Qmmax

(about twice and more)

So it seems that water fall in hard rain and not in compact jet in

the wheel

I have no good onformation on the eventual position of a vane

Thanks for a reply

A MENDRET

FRANCE - View Sourceamader2003 wrote:
>

If what you say is correct, then the coefficient of discharge is about 0.5. I

> Excuse me for the previuos mail incorrect

> I am searching about crossflow and the works of Nadim m Aziz in

> Clemson university

> I cannot undestand the large lamda admission ( 90 degrees) and the

> fact of the Q that couls pass in the nozzle is >> than the real Qmmax

> (about twice and more)

> So it seems that water fall in hard rain and not in compact jet in

> the wheel

> I have no good onformation on the eventual position of a vane

>

> Thanks for a reply

>

> A MENDRET

> FRANCE

cannot accept that it is ever this low for a well designed turbine (or more

specifically a well designed nozzle).

In an earlier posting, I noted seeing values of 0.95 to 0.97 quoted for Pelton

turbines. It is probably a bit less than this for a crossflow, because the

rectangular nozzle has a larger wetted perimeter compared to a circular nozzle

with the same cross sectional area.

In our designs we have simplistically taken the discharge coefficient as 1.0.

If it were actually closer to 0.5 then our performance claims will have been

greatly overstated and we would by now have a lot of unhappy customers. This is

certainly not the case.

Regards,

Max Enfield

Planetary Power