On 2020-06-07 9:13 PM, JF Mezei wrote:
Not sure of attriobutions anymore, sorry.

https://upload.wikimedia.org/wikiped...Scheme.svg.png

Is it corect to state that "Methane preburner" is the yellow area with
the text "512 bar, 811K?

Yes

Or does pre-burner include the plumbing to take some liquid methane for
a trip aroiund the engine bell and then back to the bottom of that area
labeled 512bar 811K ?

No. That is for bell and nozzle cooling and pre-heating the methane.

When liquid methane the turbopump, does it exit either to the left,
going to the engine bell to get warm or to the right, going to the input
of the LOX turbopump? Or does some flow straight down to what I assume
is the pre-burner combustion chamber?

The diagram suggests that the flow is around the nozzle and bell housing
before entering the pre-burner. Exit to the left.


In that scmatic, would it be correct to state that the "business end"
from a thrust point of view is the narrow liquid methane pipe from the
methan turbopump that goes to the input of LOX turbopump, the two get
mixed together in turbopump, then go through a heat excanger (warmed up
by the pre burner) and into the main engine combustion to produce thrust?

No. The "business ends" are the yellow and purple parts. The yellow
preburner output of hot gas labeled 321 bar (774K) is methane rich
exhaust from the methane preburner that is capable of further combustion
with additional oxidizer. The purple part labeled 377 bar (748K) is
oxygen rich hot gas from the preburner output of the oxygen preburner.
These are 'partially' combusted gases that get mix at the top of the
nozzle (in pink) are ignited at 300 bar and pass on through the nozzle
pinch to the expansion bell housing. You can visualize the flow by
knowing that gas flows from higher pressure to lower pressure, which
will give you a feel for the flow through the engine, AFTER the
turbopumps. The width of the pipes is also a clue.

The schematic seems to put a lot of emphasis on the pre-burner so not
sure how much of the fuel destined for actual thrust flows through
pre-burner vs going directly to the LOX turbopump.

It all goes through the pre-burners, it is a closed cycle. See this
awesome tutorial about the Raptor and other rocket engine design he

https://everydayastronaut.com/raptor-engine/


Also, silly question, but where do turbopumps get the mechanical energy
to turn and pus liquid to freat pressures?
In the case of mechane, if I read the graph right, would the preburner
output spin a turbine as it travels up and then right to engine and that
turbine then spins the turbp pump that suck liquid methane down?

Yes

In the case of the turbopump for LOX where does it gets it mechanical
energy?

In the same fashion. See the link above for a complete explanation. One
turbopump pre-burner is running methane rich and is powering the liquid
methane turbopump, while the second turbopump preburner is running
oxygen rich and powering the liquid oxygen turbopump. The above link
does a pretty decent job of explaining these differences. By 'rich' the
meaning here is not fully combusted, only partially so. Leaving plenty
of fuel and oxidizer to be combined and combusted in the main engine
chamber.

There are two turbopumps. One for liquid methane and one for liquid
oxygen. If you look closely at the diagram you can see it tries to
depict them simplistically at two white shafts with black lines
depicting the base of the turbopump rotors. For the methane turbopump
it actually looks like there are two axial pump compressors one feeding
the other, the other is the oxygen turbopump with one axial compressor.
Without getting into too much detail, here is a Wikipedia article that
describes how a turbopump works:

https://en.wikipedia.org/wiki/Turbopump

To crudely summarize: A turbopump consists of two axial turbines
connected to a common rotor shaft. One turbine is a compressor and is
used to compress the input fluid (the pump part) and the other turbine
is a true turbine and is using the expansion of a combusted gas to turn
the rotor that powers the pump turbine.

The flow of hot gas out of the preburners is passed through the turbine
part of each turbo pump to power the pumps. Note that the pressure drops
from the input of the preburner to the output, part of that drop is
because the hot gas is doing work to turn the pump rotors.
This is how turbopumps work. Whether it be in a SpaceX Raptor rocket
engine or a "turbocharged" car.

Hope This Helps,
Dave