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Subject: A parametric study of a plug nozzle, using the Liquid Propellant Program (LPP) CodeBy: Stuart S Dunn, Douglas E Coats, Software and Er.gineering Associates, Inc.
Abstract
The Liquid Propellant Program (LPP) computer code is a super-set of the industry
standard Two Dimensional Kinetics (TDK) computer code, which has been developed by
Software and Engineering Associates, Inc. (SEA, Inc.) over the past twelve years. The TDK
code uses a Two-Dimensional Method of Characteristics solution with fully coupled finite rate
kinctics for axially symmetric nozzles. The chemical reactions are modeled with a generalized
reaction package that includes 3rd body efficiencies and four reaction rate forms. The code
performs optional solutions for frozen or equilibrium flow. TDK evaluates discrete shocks, both
attached or induced. The Transonic module models variable mixture ratio profiles fl'om the
combustion chamber injector. The Mass Addition Boundary Layer module (MABL) calculates
the boundary parameters with the same chemistry options, and includes transpiration or tangential
slot injection of gas at the wall.
The LPP upgrades include: planar nozzles, scarfed nozzles, plug nozzles, and scrarnjct
nozzle configurations. The code evalu_.tes both upper and lower wall flow simulation, and
includes the interaction with the external flow. The MABL module evaluates equilibrium
radiation heat transfer for both upper and lower walls. In addition, the LPP code models
combustion effects due to injector inefficiencies with the Spray Combustion Analysis Program
(SCAP) module. The LPP package provides extensive post plotting capabilities for flow
visualization. The LPP is sufficiently fast and robust to provide performance predictions for
extensive parametric studies and sufficiently accurate to provide flow field and performance
solutions for detailed studies.
The evaluation of a planar or axially symmetric plug nozzle has received recent interest
dtte to the SSTO studies. The LPP code allows easy modeling of a plug nozzle configuration,
since the user is allowed to input an arbitrary inner and outer wall geometry (referred to as the
plug and the cowl). The transonic analysis models both planar or axially symmetric annular
flow, including straited and variable mixture ratio profiles. When the internal flow reaches the
exit of the outer wall, a PrandtI-Meyer fan allows the flow to expand to the external pressure.
At this point, a pressure boundary condition is apl2lied for either quiescent sub-sonic, or super-
sonic external flow. The MABL analyses is subsequently performed to evaluate the boundary
layer losses for both the inner and outer walls. Following JANNAF standard procedures, the
characteristic analysis is automatically repeated with the boundar) layer compensated wall
geometry.
The above procedure was employed to parame_.rically evaluate the performance of several
plug nozzle configurations at different flight conditions. The altitude compensating effects are
evaluated and related to ideal conventional nozzle performance. An optimization technique Js
presented, which includes chemistry, divergence, and boundary layer effects. Graphical output
includes flow field contours, and wall properly profiles.
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https://ntrs.nasa.gov/search.jsp?R=19960029260 2020-06-10T02:16:54+00:00Z
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