Re: Hydrogen Powered Supersonic Concorde Replacement

Black propaganda purports to support their target, even while they
undermine it. So, obviously, you would support my views as part of a
black propaganda effort. lol. Whether are supporting my views
honestly, or not, doesn't matter as far as the black propaganda
effects are concerned.

As far as your more serious question about NOx - here is what I posted
elsewhere, and repeat here below.

You had mentioned in one of your posts about carrying oxygen along.
Well, there is a way to do that in the Scimitar/Sabre engine proposed
for this hypersonic plane

http://www.theregister.co.uk/2007/10/24/hypersonic_hydrogen_rocket_airliner/

The air gets liquified at high speed. First there's a massive
compression wave, and a lot of heat radiated away. The radiatively
cooled air is then expanded through a series of shock waves and it is
liquified.


http://www.reactionengines.co.uk/lapcat_scim.html

Since liquid nitrogen and liquid oxygen have different densities and
different boiling points, it is theoretically possible that the
nitrogen may be removed and oxygen passed through the engine while the
nitrogen is passed around the engine and heated to a lower
temperature.

Oxygen: -297F 71.2 lbs/ft3
Nitrogen: -321F 50.5 lbs/ft3

The configuration to achieve this would be a little different than
Reaction Engines' design. There would be a swirl introduced to the
gas before it reached the cooling heat exchangers, and the oxygen
would precipitate out, and because the air mass was spinning, would be
thrown to the outside of the engine, there, it would enter a plenum
separating it from the gaseous nitrogen. This plenum would exclude
about 98% of the nitrogen gas. In the plenum, the oxygen would be
heated by contact with a radiator that was connected via heat pipe to
the cooling heat exchangers. The warmed oxygen would then mixed with
hydrogen and put through a staged reaction, the heat of which would be
passed to the enclosed (but separate) nitrogen flow - warming it to
exit temps, but not in excess of 2,300F

This speculative design would eliminate nearly all NOx.

There are less speculative approaches however such as those described
below;

* * * *

The formation of "thermal NOx" increases with increases in the
concentrations (amounts per unit volume) of nitrogen, oxygen, and the
combustion temperature. At
combustion temperatures below 2,370F, smaller concentrations of NOx
are formed, and below 1400F almost no NOx is formed. The methods for
the reduction of NOx formation are all based on controlling the
temperature and/or by limiting one or more of the concentrations of
oxygen, nitrogen, or the fuel.


1. Less Excess Air


Air in excess of that required to completely oxidize the fuel has been
shown to correlate with the amount of NOx formed. Limiting the net
excess air flow to under 2% limits the amount of excess oxygen
available for the formation of NOx


2. Air Staging


To effect air staging, the air is divided into two streams. In the
first stream, fuel is mixed with an insufficient amount of air for
complete combustion. The second air
stream is injected downstream from the flame and results in a slight
excess of air. This technique is used to keep the temperature
relatively low as well as the oxygen concentration in the primary
combustion area. High efficiencies have been reported with the use of
this technology.


3. Over Fire Air


This is another technique for reducing the combustion temperature by
staging the main combustion zone such that the combustion temperature
is lowered thereby lowering the formation of NOx. In this approach,
the primary combustion is carried
out with a fuel-rich mixture. The lack of oxygen needed for complete
combustion holds down the combustion rate which in turn limits the
combustion temperature. After the stages of combustion have been
completed, the remainder of the fuel is oxidized in over fire air. In
this process, some excess of air is used


4. Fuel Reburning


When cooled combustion gas and additional fuel are recirculated, some
of the heat of combustion is absorbed by the cooled combustion gas
thereby lowering the temperature and the NOx production. Also, when
the cooled combustion gas and fuel are added as a secondary combustion
stage, the oxygen in the NOx tends to oxidize the fuel producing
molecular nitrogen (N2) and oxygen (O2). Burning of the remaining fuel
is completed in a later stage using either combustion air nozzles or
over fire air. This technique has been demonstrated to be effective
with residence times from 0.2 seconds up to 1.2 seconds. Reductions of
NOx up to 76% have been achieved by this technique


5. Low NOx Burners


In a low NOx burner, a stable flame is provided over several different
zones. As an
example, the first zone can be primary combustion, and the second may
be fuel reburning in which fuel is added to chemically reduce the NOx
to molecular nitrogen (N2) and oxygen (O2). The third zone may consist
of the final combustion which is carried out with low excess air to
limit the temperature. Many variations of the above LNB for the
reduction of NOx exist.1,4 The LNB control technology has the largest
experience base of any technology in the United States. Over the last
decade, several generations of low NOx burners have evolved; see for
example Bab*** Borsig Power, DB Riley.7 The low NOx burners (LNB)
have achieved up to 80% reduction of NOx.


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