Ex. 6.2

[Ashveen Tewarie]

Did you have a chance to lok at Ex 6.2? I found a Felman Mollier
diargam on the internet but I'm not sure how to proceed...

[Josh Duckett]

Sorry - I've been out on a trip for work. I'm just getting to start
Homework 4 this evening. Have you run into any major problems? I'm
sure you've gotten past this question but we don't need the Felman
Mollier diagram since we're only doing the problem for Nitrogen.

[Josh Duckett]

For Problem 3.1, were you able to work out a relationship between
alpha* and T that did not involve density?

[Josh Duckett]

Have you gotten both homework problems figured out? I'm having
trouble in both of them avoiding a dependence on density? In the
first problem the density should change as the wind tunnel discharges
and in the second we are supposed to find the density at another
temperature after we find the relation between T and alpha. I'm stuck
trying to figure out how to solve without knowing density.

Have you had any luck?

[Bryan]

I have a plot of alpha(T) for 3.1 but I'm not even sure it's in the ballpark. I predict total dissociation at about 3200-3500 K which seems a bit early to me. The way I got around the density dependence is to use the relation of eqn 2.6, which gives density as a function of T and alpha. For the second question, part b, I just use the same relation (2.6) for a known T, alpha, and P.

I'm having some trouble on the Hotshot wind tunnel problem though, so I'm not much help there but if you figure something out I could use the advice.

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[Josh Duckett]

Thanks...ill see if I can figure anything out with that info. I've got to go to something for the next couple hours but if I get anything this evening ill let you know. It may be late tonight tho since I'm on the west coast.

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---

From: Bryan <sprtn...@gmail.com>

Date: Sun, 28 Mar 2010 17:11:05 -0400

To: <mae...@googlegroups.com>

Subject: Re: Ex. 6.2

[Josh Duckett]

I may have gotten something with 3.1 but had to make some assumptions
to get there and ignore some constants to get relationship between T
and alpha*. I've gotten a complete dissociation temp of around 5500K.

I started with eq 2.5 p 153 and used the equation you gave to get rid
of roe. used the relationships for Q^a and Q^aa in the book. Only
thing I'm not sure of is I ignored the h^2 part - not sure about the
legitimacy of that.

Have to finish up the second problem this evening and tomorrow and
send in

[Ashveen Tewarie]

Sorry I could not reply earlier....I was in Tobago on a business trip.
Hope I'm not too late
For 3.1 I'm getting complete dissociation at T= 6000 K.

For 6.2 the density remains constant, it's a closed system and they
are talking about discharge of electric energy. The nitrogen is not
discharged (yet) in this problem.
What I did here is determine alpha as a function of T from eqn (2.9)
on page 155. From this I derived the quantity alpha^2/(1-alpha) as
function of T.
Then I made a matlab plot of this expression as a function of T and in
the same figure I made a plot of eqn (3.1) on page 157. This gives a
graphical soln for T and alpha^2/(1-alpha). From this you can
determine alpha of course.

hope this helps a bit....

[Josh Duckett]

How will the density be constant for a wind tunnel...isn't the point that the hotshot energized the air and it flows out of the resevoir?

Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Ashveen Tewarie <ashv...@gmail.com>
Date: Mon, 29 Mar 2010 04:06:41
To: MAE 562<mae...@googlegroups.com>
Subject: Re: Ex. 6.2

[Ashveen Tewarie]

First the heat is added to a fixed volume (closed system) and this
causes P and T to increase. After this process has taken place the air
is released. But this problem is about the first part where heat is
added to the fixed volume of the tunnel. Thus total mass and total
volume remain constant, so rho is constant. We are dealing with a
closed system here.

The second part of the problem, where the air is released is not part
of the HW problem but will be assigned in the next HW I guess.

[Josh Duckett]

Got it...that makes sense

Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Ashveen Tewarie <ashv...@gmail.com>
Date: Mon, 29 Mar 2010 09:09:35
To: MAE 562<mae...@googlegroups.com>
Subject: Re: Ex. 6.2

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