Overview
A
new advanced-cycle rocket engine system has recently
undergone testing for the United States Government.
The system uses Liquid Hydrogen and Liquid Oxygen
propellants. This engine system represents a fundamental
advance in the state-of-the-art in both system and
component-level technologies.
A
modeling task was recently undertaken in an attempt
to validate SINDA/FLUINT Version 5.0 against the
Oxidizer Turbopump of the above-mentioned rocket
engine system. A model of the Oxidizer Turbopump
and its components was constructed in Thermal Desktop.
This model is relatively detailed and includes inducer
and impeller pumping elements, fluid-operated bearings,
hot-gas turbine drive system, and the internal axial
thrust control system. Data for this model was obtained
from design reports and engineering drawings. Since
the purpose of this modeling exercise was validation
of a new computational tool, no attempt was made
to “tune” or otherwise
adjust the model to “fit” experimental
data. Formulation of the model elements was limited
to “best
practices” available. The hardware being simulated
is under ITAR export control, so no detailed description
can be provided in published form.
Steady
State (Primary and Secondary Flows, Axial Thrust
Control)
When
the model was compared to “flange-to-flange” experimental
data (both pump and turbine through-flow under varying
circumstances), differences between the model and
experimental data were negligible (usually less than
1%).
A
more demanding validation test is that of modeling
the turbopump internal (or “secondary”)
flows and axial thrust balance.
The
model was used to simulate a number of steady-state
operating points for which data existed. For flow
through various bearings and seals (as well as the
axial thrust control system), the differences between
the model and data were typically less than 10%.
It should be borne in mind that this constitutes
10% of a mass flow that is itself approximately 10%
of the total pump through-flow. It could therefore
be stated the differences between model and data
for these secondary flows is in a range comparable
to that of the “error
bars” of the flow data.
Rotor
Start-up Transient (Primary Flows, Torques)
A
final validation with experiment consisted of comparison
of model results with that of a transient run of
the Oxidizer Turbopump. The period simulated began
during the initial acceleration of the turbopump,
and lasted until steady-state conditions were achieved—approximately
15 seconds. Data from the turbopump test was compared
with simulation data at 4 points that represent characteristic “peaks” and “valleys” of
the test. In particular, data on shaft speed, pump
discharge pressure, and turbine exit temperature
were compared to model predictions. The largest difference
between model and test data at any given point was
13%. The quantity in question was the turbine exit
temperature during the period of highest system acceleration.
At all other times (and for all other parameters)
the differences between model and data were between
1.5% and 9.5%, with 4% to 5% being a representative
average.
Conclusion
SINDA/FLUINT
V5.0 was used to simulate the behavior of an advanced
Liquid Oxygen Turbopump. The model was built to simulate
all of the major pump internal flows that affect
efficiency and axial thrust. Validation with both
steady-state and transient experimental data was
conducted. The correlation with steady-state experimental
data was relatively good, with negligible errors
between model and data for “flange-to-flange” operating
characteristics. Internal secondary flows and their
influence on axial thrust were also modeled. The
maximum error in steady-state axial thrust potential
between model and data was approximately 4%. The
correlation with data from a transient hot-fire test
of the turbopump was also good. The maximum error
between model and data for this test was 13% for
the turbine exit temperature. This occurred when
system acceleration was near its peak. The average
differences between model and data for all other
times of the transient was 4% to 5% for “flange-to-flange” interface
parameters.
For
More Information
The
hardware being modeled in this exercise (and therefore
the model) is under ITAR export control. US Government
employees wishing to view the data may refer to SBIR
Contract FA9300-06-M-3011. For non-government personnel,
additional information is available via the contact
list below.
Dave
Mohr
D&E
Propulsion and Power
Phone:
1-321-267-6296.
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