modeling the thrust regulator of a liquid rocket engine · modeling the thrust regulator of a...
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Mathew Saxon A.
Vishnu Suresh Nair
Sajeev.P
Bejoy John
Liquid Propulsion System Centre.
ISRO.
Modeling the Thrust Regulator of a Liquid Rocket
Engine
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Thrust Developed by Liquid Rocket Engine
Mass flow rate
Exit velocity
Exit Area
Exit pressure
Ambient pressure.
Thrust,
For a Given Nozzle Mass Flow rate α Chamber
Pressure and At
Thrust can be maintained constant by regulating chamber
pressure, Pc
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Problem Statement
Modeling the Thrust Regulation System of a Bipropellant
Liquid Rocket Engine.
Capturing the Behavior During Shut Down Transient
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Thrust Regulation System
Chamber Pressure
Feedback.
Reference Pressure.
Three Regulators
Fuel
Oxidiser
Water
Thrust Regulation System control the mass flow rate
to GG to keep the turbine power at the level necessary
to achieve the required thrust chamber pressure.
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Modeling Approach
Governing Equations from First Principles
Parameter Estimation
Using Measured
Data
Integrated Nonlinear
Model
Grey Box Modeling
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Working Principle of Regulator
Flow
Pre
f
Pin
P out
The regulators work on the principle of pressure balance over the faces of the regulator
piston.
Any difference in the balancing pressures, makes the piston to move.
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Modeling of Regulator
Dynamics Of Regulator Piston
M - Mass of the piston B - Damping constant X- Piston Position Pin – Inlet Pressure. Pref – Reference Pressure Pout- Regulated Pressure
Conservation of Momentum
Substituting
. Flow Through Variable Area Orifice
------------(1)
-----(2)
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Model Formulation
Pin
Pref
Pout
Calibration
Orifice
GG Q
Pgg
Regulator
+ -
+
-
To
Turbine
Typical Fluid Circuit Line Of The Thrust Regulation
System
------------(1)
------------(2)
------------(3) Equations 1,2 and 3
completely represent one
typical fluid circuit line of
the thrust regulation
system.
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Parameter Estimation
Create File Describing model structure
Provide Model Orders
Initial States
Use' idnlgrey ' to create Non Linear grey Model
Iddata from measured data
Use 'pem ' to estimate parameters
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Model Validation
Data acquired in one of the tests is
used for validating the model. Shut
down transient regime after the
shutdown command is issued is
considered for model validation.
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Conclusion
Model validation indicates that the predicted regulator outlet
pressure during transient is fairly accurate.
The model has been developed by using System Identification
Toolbox available in MATLAB.
The regulator outlet pressure decides the propellant flow rate to
GG and thereby controls the thrust chamber pressure.
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Thank you …..