Liquid Propulsion

Liquid Propulsion Modeling and Fluid Flow Design

The NASA standard tool for heat transfer and fluid flow analysis, SINDA/FLUINT, includes thermodynamic and hydrodynamic solutions specifically targeted at the growing demand for design and analysis of liquid propulsion systems.

Many organizations have previously used separate in-house tools specialized for each of the above applications. However, these organizations typically do not have the resources nor infrastructure to maintain these codes when cognizant engineers are lost, nor to modify and validate them for new vehicles or applications, nor to train new engineers on their use. The use of a single general-purpose tool to encompass all such analyses offers not only solutions to these problems, but also enables integrated analyses and the ability to communicate with vendors and customers.

An extensive set of generalized thermal/fluid modeling tools exists that was developed to satisfy the specialized needs of liquid propulsion system design and analysis. These tools can uniquely provide integrated modeling of an entire fuel tank system including pressurization system, feedline, and turbopump. They can also link intimately with thermal models of the structure and environment. Included are high-level design synthesis, statistical design, and model correlation modules. An extensive infrastructure exists of pre- and postprocessing software, training, and user support. While the models made using these tools might be proprietary, the tools themselves are readily available to all organizations, overcoming significant limitations of in-house codes.

Propulsion Design Applications

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For further information, please contact CRTech

dispersed vs. coalesced front

Tuesday, June 26, 2018, 1-2pm PT, 4-5pm ET

This webinar describes flat-front modeling, including where it is useful and how it works. A flat-front assumption is a specialized two-phase flow method that is particularly useful in the priming (filling or re-filling with liquid) of gas-filled or evacuated lines. It also finds use in simulating the gas purging of liquid-filled lines, and in modeling vertical large-diameter piping.

Prerequisites: It is helpful to have a background in two-phase flow, and to have some previous experience with FloCAD Pipes.

Register here for this webinar

FloCAD model of a loop heat pipe

Since a significant portion of LHPs consists of simple tubing, they are more flexible and easier to integrate into thermal structures than their traditional linear cousins: constant conductance and variable conductance heat pipes (CCHPs, VCHPs). LHPs are also less constrained by orientation and able to transport more power. LHPs have been used successfully in many applications, and have become a proven tool for spacecraft thermal control systems.

However, LHPs are not simple, neither in the details of their evaporator and compensation chamber (CC) structures nor in their surprising range of behaviors. Furthermore, there are uncertainties in their performance that must be treated with safety factors and bracketing methods for design verification.

Fortunately, some of the authors of CRTech fluid analysis tools also happened to have been involved in the early days of LHP technology development, so it is no accident that Thermal Desktop ("TD") and FloCAD have the unique capabilities necessary to model LHPs. Some features are useful at a system level analysis (including preliminary design), and others are necessary to achieve a detailed level of simulation (transients, off-design, condenser gradients).

CRTech is offering a four-part webinar series on LHPs and approaches to modeling them. Each webinar is designed to be attended in the order they were presented. While the first webinar presumes little knowledge of LHPs or their analysis, for the last three webinars you are presumed to have a basic knowledge TD/FloCAD two-phase modeling.

Part 1 provides an overview of LHP operation and unique characteristics
Part 2 introduces system-level modeling of LHPs using TD/FloCAD.
Part 3 covers an important aspect of getting the right answers: back-conduction and core state variability.
Part 4 covers detailed modeling of LHPs in TD/FloCAD such that transient operations such as start-up, gravity assist, and thermostatic control can be simulated.