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Qualification of the European Shock-Tube for High Enthalpy Research

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... Several authors studied laser-induced spark ignition in different conditions and gas mixtures, and reported the minimum irradiance values for initiating combustion. These are summarized in Table I. 11 Bradley,[5] Air at 1 MPa 1×10 10 Phuoc, [4] Theoretical 1×10 12 Phuoc, [7] Air, CH4, O2, N2, H2 at 150 and 3040 Torr 1×10 14 Srivastava, [6] Drude model 1×10 12 Weinrotter, [1] H2-air 2.8 MPa air:fuel ratio 3 1×10 10 Lee, [8] Propane-air at 1 atm ...
... Several authors studied laser-induced spark ignition in different conditions and gas mixtures, and reported the minimum irradiance values for initiating combustion. These are summarized in Table I. 11 Bradley,[5] Air at 1 MPa 1×10 10 Phuoc, [4] Theoretical 1×10 12 Phuoc, [7] Air, CH4, O2, N2, H2 at 150 and 3040 Torr 1×10 14 Srivastava, [6] Drude model 1×10 12 Weinrotter, [1] H2-air 2.8 MPa air:fuel ratio 3 1×10 10 Lee, [8] Propane-air at 1 atm ...
... The European Shock Tube for High Enthalpy Research (ESTHER) [9,10] is a facility capable of reaching shockspeeds in excess of 10 km/s. The facility comprises a 50.3 liter combustion chamber driver where an hydrogen/oxygen mixture diluted in helium with filling pressures up to 100 bar is ignited to a post-combustion pressure up to 600 bar. ...
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We report consistent ignition of high-pressure (p > 20-30 bar) hydrogen-oxygen mixtures diluted with helium, using an unfocused Nd:YAG laser. This corresponds to laser irradiances several orders of magnitude below the minimum ignition energies reported in the literature. By placing a mirror inside a cylindrical vessel and filling it up to 100 bar with H2-He or O2-He non-combustible mixtures, we obtain the pressure-dependent absorptivity of the combustible He-H2-O2 mixture. We find no measurable absorption of the laser signal by the medium, for the overall pressure range, to the experimental apparatus sensitivity (about 1% of the laser irradiance). This leads credence to the theory that ignition stems from seed electrons created by autofocusing ionization of dust/impurities in the gas.
... Examples of such facilities are shock tunnels NASA HYPULSE (ATK GASL, USA) [24,25], TH2 (Aachen, Germany) [26] and Chinese shock facilities JF16 [27] and JFX [28]. The new detonation driven shock tube ESTHER (European Shock Tube for High Enthalpy Research) that is being commissioned at the Higher Institute of Technology (IST, Lisbon) is also designed to study radiation and chemical kinetics relevant to planetary entries [29]. In Russia, the large amount of information was obtained on the shock tubes of the Moscow Institute of Physics and Technology [30,31] and the Institute of Mechanics, Moscow State University [32][33][34]. ...
Article
This paper presents a description of the modernized detonation driven shock tube DDST-M, in which conditions that simulate the entry of spacecraft into the Earth's atmosphere at the super orbital velocity (11.2 km/s) are achieved. The modernization consists in the inclusion of an additional element in the shock tube design - the prechamber, which separates the end wall of the tube with the igniter from the main volume by the perforated disc. The presence of the prechamber increases the energy efficiency of the facility, primarily due to a more complete combustion of the combustible mixture in the high-pressure chamber, which makes it possible to obtain higher shock wave velocities in the low-pressure chamber. A series of experiments was carried out to study the radiation characteristics of high temperature air in the range of shock wave velocities VSW = 4.2 ÷ 11.4 km/s and initial gas pressures p0 = 0.25 ÷ 10 Torr. Analysis of the obtained data made it possible to distinguish the features of the radiation in different parts of the spectrum depending on the shock wave velocity and the initial gas pressure. The measurement results are compared with the results of other studies.
Conference Paper
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In the scope of the detailed definition phase for the upcoming ESA-sponsored EXOMARS mission, an analysis on the entry phase aerothermodynamics has been carried, with a particular emphasis on radiation. Mars atmosphere is majorly composed of CO2 (95%), yet the majority of the aerothermodynamic databases disregard the contribution of CO2 and CO Infrared (IR) radiation to the radiative fluxes whistanded by a spacecraft thermal protections. The contribution of such radiative fluxes to the overall power budget, in the specific case of the EXOMARS entry vehicle, was the main topic of the work described in this article. It has been found out that IR radiative fluxes are significantly dominant over the whole entry path (>99.5% of the overall radiative fluxes), with afterbody radiative fluxes roughly equivalent to the convective fluxes. Furthermore, as CO2 radiation is favored at temperatures around 1,500-3,000K, the radiative peak occurs much afer the convective peak, at lower entry velocities.
Article
The reduction of test time in low pressure shock tubes, due to a laminar wall boundary layer, has been analytically investigated. In previous studies by Roshko and Hooker the flow was considered in a contact surface fixed coordinate system. In the present study it was assumed that the shock moves with uniform velocity, and the flow was investigated in a shock fixed coordinate system. Unlike the previous studies, the variation of free stream conditions between the shock and contact surface was taken into account. It was found that β, a parameter defined by Roshko, is considerably larger than the estimates made by Roshko and Hooker except for very strong shocks. Since test time is proportional to β−2, previous estimates of test time are too large, particularly for weak shocks. The present estimates for β appear to agree with existing experimental data to within about 10 percent for shock Mach numbers greater than 5. In other respects, the basic theory is in general agreement with the previous results of Roshko.
Radiation From Simulated Atmospheric Entry Into the Gas Giants
  • C James
C. James, "Radiation From Simulated Atmospheric Entry Into the Gas Giants", Ph.D. Thesis, Mechanical and Mining Engineering Department, University of Queensland, Queensland, Australia.
Mapping of the Aerodynamic Performance of the ESTHER Shock-Tube
  • D Luis
D. Luis, "Mapping of the Aerodynamic Performance of the ESTHER Shock-Tube", Ms. C Thesis, Instituto Superior Técnico, Universidade de Lisboa, Sep. 2018, available at https://fenix.tecnico.ulisboa.pt/cursos/meaer/dissertacao/ 1972678479054139.
Development of a Combustion Driven Shock Tunnel
  • K C Hendershot
K. C. Hendershot, "Development of a Combustion Driven Shock Tunnel,", Symposium on Hypersonic Techniques, 20-21 October 1960, University of Denver Research Institute, (Institute of Aeronautical Sciences, New York, 1960).