About Jean-Pierre Petit
Jean-Pierre Petit is a French scientist, senior researcher at National Scientific Research Center (CNRS) now retired. Gratuated from Supaero (French National Higher School of Aeronautics and Space) in 1961, Sc.D. in 1972, he is astrophysicist, fluid mechanician, plasma physicist, magnetohydrodynamics specialist. His carrier in the field of MHD is well-know: 1st method of eletrothermal instability control and 1st usable MHD generator with non-equilibrium ionized gas (1967); Non-equilibrium plasma kinetic theory (1972); MHD aerodynes with HF ionization control (1975); Shock wave cancellation by MHD force field around a cylindrical profile imbedded in a liquid flow (1976); 2nd method of electrothermal instability control by magnetic pressure gradient in a MHD accelerator (1981); Thesis director about shock wave annihilation around a flat wing in a hot supersonic gas flow: Resolution of Navier-Stokes equations within an MHD force field with the method of characteristics (1987). See the list of his publications about MHD in homepage references.
1 For a brief explanation of magnetohydrodynamics (MHD) and its engineering applications (power generation and propulsion), please go back to MHD Prospects homepage.
2 A gas with a non-equilibrium ionization (also called a two-temperature or bitemperature plasma, non-thermal plasma, cold plasma or non-Lorentzian plasma) is a plasma where the electron temperature Te is much greater than the ion temperature Ti which drives the global gas temperature.
3 The electrothermal instability, also known as the ionization instability or Velikhov instability, was discovered by Russian physicist Evgeny Velikhov in 1962. It arises in a few microseconds within non-thermal plasmas in MHD converters, when the Hall parameter due to the ambiant strong magnetic field reaches a critical value (β ~ 2 in a Coulomb-dominated plasma at standard atmospheric pressure). The plasma becomes stratified with a succession of high electron density then poor electron density layers, and the global efficiency slumps.
4 Above Mach 4-5, an air flow in considered as hypersonic. The main problem is then the "heat barrier" or "thermal barrier", because the temperature, caused by brutal gas recompression behind shock waves, increases like the Mach number squared. Materials, and especially moving parts of turbojets (compressor, turbine) cannot endure the thermal flux anymore.