Ongoing Research
Data Analysis, Future System Uses
A valuable lesson we learned from the previous hot-fire experience is that we cannot rely solely on commercial piping components, such as off-the-shelf valve regulators, to control the engine system accurately. Therefore, the ELLIE team is continuing as a long-term research group, focusing on advanced valve control.
A significant concern has been the droop in the system. It has severely impacted our engine performance, since only a fraction of the GOX flow truly occurred, which resulted in a fuel-rich burn. Here is the visualization of the issues caused by droop, plotted in MATLAB:
PT1 measures the pressure of the combustion chamber downstream, while PT2 measures the pressure of the GOX flow. It appears that the GOX regulator's droop was much higher than what we expected, since we have addressed droop by intentionally setting the regulated pressure higher than the nominal pressure. The result was a low-pressure, low-mass flow burn in the combustion chamber. This conclusion is supported by PT1 data with a high point of about 150 psi, which is 100 psi below the GOX pressure.
The ELLIE team is addressing this issue by designing a self-regulated valve. The valve will be able to adjust the flow rate according to real-time pressure changes to guarantee a desired mass flow rate.
Summary
Data Analysis (Refer to P&ID on Physical System for instrument locations):
Data:
Max Thrust: ~32 lbf
Combustion Chamber Pressure: ~145psi
Upstream GOX Pressure: 250psi
Upstream ETH Pressure: 335psi
Analysis:
Thrust was ~1/3 predicted:
GOX feed pressure was very low > sustained a low-pressure reaction in chamber
Low Combustion Chamber Pressure + low flowrates > low combustion chamber pressure.
Long-Term ELLIE system goals:
Use existing printed circuit board and fluid system for component testing of LE2
Build upon fluid system to test active flow control valves for LE3
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