Design and Analysis of Low-Pressure Propellant Feed System for the X-34 Flight Vehicle

Photo of Jason Wrobel, Michael Ohlson, Travis Hampton Students: Jason Wrobel, Michael Ohlson, Travis Hampton

Sponsor: NASA

Date: Fall 2011

Requirements:
Because little public information is available on NASA's proprietary designs, the team performed an extensive literature review to understand the X-34's PFS. The fuel tanks were required to have mass flow rates of approximately 140 lbm/s and 65 lbm/s for LOx and RP-1 tanks, respectively, to empty the majority of the propellant contents. Turbopump inlet pressures must be maintained near pressures of 46 and 28 psia for the LOx and RP-1 lines, respectively, to avoid cavitation. To fulfill these demands, a helium pressurization system is included in the system to pressurize the propellants, as well as to operate pneumatic control valves to ensure low-pressure PFS functions as intended.

Problem:
The objective of this design project is to perform a complete design investigation and analysis of the main Propellant Feed System (PFS) of the X-34 flight vehicle, and to provide a final low-pressure plumbing system design recommendation backed by thorough analysis. The project focuses on the vehicle's Fastrac engine's low-pressure plumbing system, originating at the fuel, oxidizer, and helium storage tanks and terminating at the main propellant exit flows of the turbopump.

Solution:
The team accomplished its goals with the aid of NASA's Generalized Fluid System Simulation Program, GFSSP. After building models for the LOx, RP-1 and helium systems using a fundamental fluid mechanics approach, the team verified their results by comparing GFSSP results to given steady state head losses of the system. This allowed the team to combine the three different models and perform a transient analysis on the X-34's low-pressure plumbing system. After the team verified the transient model's performance by comparing the simulation results to published NASA technical documents, the team continued their work by analyzing concept variant design parameters. This work yielded a final design recommendation of decreasing the RP-1 pipe diameter to 3.75" and increasing the LOx diameter to 4.9". Also, the helium line diameter was increased to 1", 0.9" to feed the LOx, and 0.75" to feed the RP-1.

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