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Development of a control algorithm for a dynamic gas mixing system

An algorithm was developed to control the partial pressures of N2, O2, and CO2
in a gas mixing tank. The gases were premixed before being introduced into the low
pressure Mars Dome. As an attempt to reduce the effects of pressure, the number of
moles of the component gases was calculated and used to determine when gases needed
to be added to the system or when gas concentrations needed to be diluted. There were
two trial runs during each of the two experiments carried out. The total pressures in both
the mixing tank and the Mars Dome remained within their limits of constraint during
both trials. For the mixing tank, the pressure was maintained between 170kPa and
180kPa with a setpoint of 175kPa. Gas composition was evaluated at 67kPa and 33kPa
in the Mars Dome. Again the pressure remained within its range of ±5kPa of its setpoint.
Adequate control of the partial pressures of N2, and O2 were achieved in the mixing tank
and the Mars Dome. With respect to the control of CO2, the algorithm was unable to
maintain the partial pressure within the operational limits specified. The tendency was
for CO2 to linger above its setpoint. Moreover, at 33kPa the CO2 sensor in the Mars
Dome began to reflect a lower concentration of CO2 in the system than what was
reported by the gas chromatograph or the CO2 sensor in the mixing tank. While
sufficient control of the partial pressures was achieved, there are modifications to be made that should further tighten the control limits of the system. Such modifications
include recalibrating the sensors in the system and adjusting gas flow rates.

Identiferoai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/3775
Date16 August 2006
CreatorsLovelady, April
ContributorsLacey, Ronald E.
PublisherTexas A&M University
Source SetsTexas A and M University
Languageen_US
Detected LanguageEnglish
TypeBook, Thesis, Electronic Thesis, text
Format1795346 bytes, electronic, application/pdf, born digital

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