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Measurements and Experimental Techniques

Relatori: Prof. Bortolino Saggin, Ing. Diego Scaccabarozzi

Tutor: Prof.ssa Barbara Previtali

Università di Provenienza: Politecnico di Milano - Ingegneria Meccanica

Titolo della Tesi: Dust Monitoring in Martian environment

Dust monitoring in Martian environment

Introduction

The research is addressed to the development of a particle analyzer operating in Martian atmosphere. The instrument MicroMED (MMED) is an optical particle analyzer with measurement targets particle size distribution and density in terms of particles per unit of atmosphere volume. The latter target involves the development of the instrument flowrate measurement system, compatible with Martian environment.

Objectives

  • Development of a flowrate measurement system for low-pressure gases to be used as reference in laboratory tests
  • Performance assessment of the instrument pump in the expected working conditions
  • Specification of the required pressure transducer for the instrument and its characterization in the expected environmental conditions
  • Experimental characterization of the instrument’s inlet-outlet fluidic resistances for different operating conditions

Results

  • The laboratory-use flowrate measurement system, based on a bellow as control volume, allows low-pressure gases flowrate measurement with the required accuracy. The MMED’s pump performance characterization can be performed in operating-like conditions thanks to this flowrate measuring device. Gas compressibility at the low pressures must be accounted for, flowrate is therefore given by The Fig.3 (Comparison of commercial pump performances in low environmental pressures of 10 and 3 mbar)
  • Flight-qualification of MMED’s differential pressure sensor has required calibration in the expected range of mission environmental conditions of temperature and pressure (Fig.5 -Pressure sensors’ Sensitivity curves at low operational condition (-25,7°C) constant 1.5 mA current excitation).
  • Characterization of the inlet-outlet fluidic system resistance curve with air and CO2 as working gas in Martian-like conditions has been performed to allow deriving the flowrate measurement from the pressure drop one. The analytical flowrate measurement scheme for the instrument considers: Q = f(TM,PM,TS,ΔP) (Fig.6 - Experimental setup for characterization of inlet-outlet system of MicroMED instrument; Fig.7 & Fig.8 - Performances of the pump with the inlet-outlet fluidic resistance – Measurements of the two differential pressure sensors (on the right top) and the chamber pressure (on the bottom) for a test with Air at 6 mbar chamber pressure)
  • Translation of the flowrates to the inlet (from point 3 to 1), and derivation of the inlet-outlet fluidic resistances (Fig.9 & Fig.10 - Fluidic resistances of the instrument's inlet-outlet system at environmental pressure 8 and 6 mbar vs. DPSM1 – experiments with Air (ambient and heated conditions) and CO2).

Conclusions

  • A flowrate measurement system for low pressure gases was developed and verified. The system was used to evaluate the performance of pumping subsystem of MicroMED in expected Martian condition. The uncertainty assessment of the flowrate measurement system was performed, and a maximum value of ±0.4 l/min was determined for its measurement in the conditions of interest.
  • The selected candidate pressure sensor was characterized in Martian conditions and qualified for flight onboard ExoMars Mission.
  • The fluidic resistance of the inlet-outlet system of the instrument’s was measured in different working conditions. That is the experimental methodology for calibration of the flowrate measurement system of MicroMED.

References

B. Saggin et al., F. Esposito et al., A. Martin-Ortega et al., Designvalidation of MicroMED, a particle analyzer for ExoMars 2020, IEEE MetroAeroSpace 2019 Proceedings, Turin June 2019, pp. 118-122.
B. Saggin, D. Scaccabarozzi, C. Pagliara, A. Valiesfahani, F. Esposito et al., Design of a flowrate measurement system for low-pressure gases, IEEE MetroAeroSpace 2018 Proceedings, Rome June 2018, pp. 279-283.
B. Saggin, D. Scaccabarozzi, A. Valiesfahani, P. Valnegri, R. Somaschini, Qualification of MEMS differential pressure sensors in Martian-like environment, IEEE MetroAeroSpace 2019 Proceedings, Turin June 2019, pp. 476-480.
G. Mongelluzzo et al., Optimization of the fluid dynamic design of the Dust Suite-MicroMED sensor for the ExoMars 2020 mission, 2018 5th IEEE International Workshop on Metrology for AeroSpace (MetroAeroSpace) IEEE, 2018.