Public Member Functions
float	mixture_ratio (self)
float	face_ratio (self)
float	feed_term (self)
float	residual (self)
float	design_error (self)
float	feed_term_for_design (self)
float	trim_pressure (self)
list[str]	notes (self)

Public Attributes
	design_error
	oxidiser
	fuel

Static Public Attributes
float	design_ratio = 0.0

Detailed Description

The O/F, split into the half the engine owns and the half the stand does.

``mixture_ratio == face_ratio * feed_term`` holds to solver tolerance. It is
an identity, not a fit, so a discrepancy between the two sides of it means
the flows and pressure drops handed in are not self-consistent -- which is
itself worth knowing, and is what :attr:`residual` reports.

Definition at line 142 of file balance.py.

Member Function Documentation

◆ design_error()

float feedtwin.engine.balance.MixtureBalance.design_error ( self )

Relative distance from the design mixture ratio [-].

Definition at line 208 of file balance.py.

References design_ratio, and mixture_ratio().

◆ face_ratio()

float feedtwin.engine.balance.MixtureBalance.face_ratio ( self )

O/F the face alone would deliver, at equal injector pressure drop.

The number the injector was drilled to. Independent of the stand, the
tanks, and the run -- change the plumbing and this does not move.

Definition at line 166 of file balance.py.

References fuel, max, and oxidiser.

Referenced by feed_term_for_design(), and residual().

◆ feed_term()

float feedtwin.engine.balance.MixtureBalance.feed_term ( self )

``sqrt(dp_ox / dp_fuel)`` [-]. Everything the stand contributes.

One when both legs drop the same across the face. Above one when the
fuel leg is the more restrictive one upstream, because then the fuel
arrives at a lower pressure and spends less of it at the face.

Definition at line 179 of file balance.py.

References fuel, and oxidiser.

Referenced by residual().

◆ feed_term_for_design()

float feedtwin.engine.balance.MixtureBalance.feed_term_for_design ( self )

The feed term that would land the design O/F on this face.

What the stand would have to do, taking the injector as built. Compared
against :attr:`feed_term`, it says how far the plumbing is from
delivering what the engine was drilled for.

Definition at line 217 of file balance.py.

References design_ratio, and face_ratio().

Referenced by trim_pressure().

◆ mixture_ratio()

float feedtwin.engine.balance.MixtureBalance.mixture_ratio ( self )

Delivered O/F, straight from the flows.

Definition at line 159 of file balance.py.

References fuel, and oxidiser.

Referenced by design_error(), and residual().

◆ notes()

list[str] feedtwin.engine.balance.MixtureBalance.notes ( self )

Findings, in the order an operator would want to read them.

Written as sentences rather than codes because they land in a report
that a person reads once, before a test, and the cost of a
misinterpreted code there is higher than the cost of a long line.

Definition at line 245 of file balance.py.

◆ residual()

float feedtwin.engine.balance.MixtureBalance.residual ( self )

Relative gap between the identity and the delivered ratio [-].

Should be at solver tolerance. Anything larger means the pressure drops
and the flows disagree, so the decomposition below is not describing
the run it claims to.

Definition at line 194 of file balance.py.

References face_ratio(), feed_term(), and mixture_ratio().

◆ trim_pressure()

float feedtwin.engine.balance.MixtureBalance.trim_pressure ( self )

Extra fuel-side supply pressure that would restore the design O/F [Pa].

Holding the ox leg where it is, the fuel injector drop has to rise to
``dp_ox / feed_target^2``; every pascal of that has to come from the
fuel tank, *plus* the extra the fuel plumbing eats at the higher flow.
The second part is why this is a first step and not an answer: it is
computed at the present flow, so it under-states the true requirement.
Positive means the fuel side needs more pressure.

Definition at line 229 of file balance.py.

References feed_term_for_design(), fuel, and oxidiser.

Member Data Documentation

◆ design_error

feedtwin.engine.balance.MixtureBalance.design_error

Definition at line 255 of file balance.py.

◆ design_ratio

feedtwin.engine.balance.MixtureBalance.design_ratio = 0.0

static

Definition at line 154 of file balance.py.

Referenced by design_error(), and feed_term_for_design().

◆ fuel

feedtwin.engine.balance.MixtureBalance.fuel

Definition at line 278 of file balance.py.

Referenced by face_ratio(), feed_term(), mixture_ratio(), and trim_pressure().

◆ oxidiser

feedtwin.engine.balance.MixtureBalance.oxidiser