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Statement of Work

Title

Development of a Numerical Simulation Tool for Predicting Transient Start-up of Cryogenic Screen Channel LADs

Introduction

Screen channel liquid acquisition devices (LADs) are being considered for several vehicles under the HLS architecture, including the ascent and descent elements, refueling element, and transfer (tug) element. Regardless of the choice of propellant (i.e. storable or cryogenic), LADs will be required to ensure single phase liquid delivery from the storage tank to an engine or receiver tank (in the case of refueling element). The ascent element may require simplified windowed sumps to feed main propulsion system but more importantly reaction control system during maneuvers in low-g during return to Gateway. The descent stage element may require a simplified screen channel LAD to maintain favorable position of liquid over the outlet despite potential high g-levels. Meanwhile the transfer element and refueling element may require a full communication screen channel LAD to access propellant in an unsettled condition in microgravity. Even if other LADs are baselined as the main acquisition system, screened sumps are commonly used as secondary acquisition devices.

NASA has developed steady state models for designing, analyzing, and sizing screen channel LADs for both storable and cryogenic propellants. However, transients are the design-limiting case, and the industry preferred method for sizing worst-case performance. Currently, NASA does not have an unsteady compliance solver for screen channel LADs. The proposed work would therefore develop an unsteady solver modeling tool, anchored to test data, that can predict screen channel behavior at the transient start of flow demand as a function of operational parameters (e.g. screen type, propellant type, valve response time, flow demand, etc.). The proposed work would perform and ensure the necessary coupling between transient and steady state solutions to allow seamless transition and enable full simulation of tank drain through the

LAD.

Period of Performance

Start Date 12/1/2019

End Date 6/30/2021

Milestones and Deliverables

There are two objectives under this project. First, the contractor will develop the necessary input functions and equations of state into the unsteady Navier Stokes LAD solver. The second objective is to develop the transient flow solver, perform a parametric analysis of the operational parameters of interest, and develop seamless coupling between unsteady and steady solvers for flow through the screen and LAD channel. Specific milestones and deliverables are enumerated as follows:

Contractor shall develop an updated data anchored equation of state for the screen deflection (pressure differential versus screen deflection distance) for the screens listed in Table 1. The equation of state must be determined experimentally. The equation must take into account both linear and nonlinear portions of deflection.

Contractor shall develop a data-anchored correlation for determining the deflection as a function of aspect ratio as defined in Table 2. The correlation must come from experiments on screens of differing aspect ratios.

Contractor shall determine candidate tank outlet valve opening times, times to steady state, and mass flow rate profiles.

Contractor will develop the transient solver for flow through the screen and channel. The contractor shall incorporate the deflection equation of state, correlation for aspect ratio, as well as cryogenic bubble point equation from [1]. The contractor shall also demonstrate that the transient flow solver is time and grid independent.

Contractor shall conduct a parametric analysis of operational parameters of interest listed subsequently:

a. Steady state demand mass flow rate between 0.001 and 0.1 kg/s

b. 3 different tank outlet valve opening time

c. 3 different times to steady state

d. 3 different profiles from 0 to steady state demand mass flow rate

e. Screen types listed in Table 1 and aspect ratios listed in Table 2.

Contractor shall develop seamless coupling to existing steady state solver from [2].

Contractor shall conduct monthly telecons to status the tasks.

Contractor shall write a final technical report outlining compliance equation of state, aspect ratio correlation, Initial simulations should focus on simulant or room temperature fluids, but final simulations should focus on cryogens like oxygen and hydrogen.

Table 1 – List of Screens and Metal Types

Table 2 – Aspect Ratios

References

1. Hartwig, J.W. and Kamotani, Y. “The Static Bubble Point Pressure Model for Cryogenic Screen Channel Liquid Acquisition Devices” International Journal of Heat and Mass Transfer 101, 502 – 516. 2016.

2. Darr, S.R., Camarotti, C.C., Hartwig, J.W., and Chung, J.N. “Hydrodynamic Model of Screen Channel Liquid Acquisition Devices for In-Space Cryogenic Propellant Management” Physics of Fluids 29. 017101. 2017.