I'm totally lost with understanding this process. Can anyone describe the
physical mechanism that enables PDEs to "theoretically" operate in a constant
volume process?
Constant volume processes (to me) implies no work done by the working fluid.
Yes there will be higher pressure and temperature outcomes because there's no
work being done - but obviously I'm missing something.
I'm guessing the detonation mechanism somehow uses more available energy for
molecular translation and less going into molecular rotation? I'm curious to
understand the mechanism.
Thanks,
Troy
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On
Behalf Of Norman Yarvin
Sent: Friday, 31 January 2020 11:12 AM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Orions and PDEs (was Re: More MAX delays.)
On Thu, Jan 30, 2020 at 04:00:08PM -0600, Jim Davis wrote:
But rockets don't spend nearly as much energy on compression as jet
engines do: they're pumping liquid, not gas, and that's much lower
volume. They also don't have the fan; if you were to extract
mechanical horsepower from a rocket engine, there'd be nothing to
spend it on that could boost thrust -- or at least nothing comparable
to leaving the energy in the combustion chamber and letting it boost
thrust that way.
You're completely missing the point. For a given amount of heat
addition the constant volume process has a higher pressure rise, a
higher temperature rise, and (most importantly) a lower entropy
increase. This means that more of the energy is available to accelerate
the fluid and less has to be rejected as heat.
I thought you'd agreed that (in a rocket) you can get all those benefits
equally
well just from upping the pressure, and that the only real downside of the
conventional approach was the need to have higher pressure turbopumps.
