Experimental and numerical investigations of plasma of products of combustion of pyrotechnic fuel in air

Abstract

Results are given of experimental and numerical investigations of plasma of products of combustion of pyrotechnic fuel [(64-69%)Mg+(35-30%)KNO 3 +1% process additions] in air for the oxidizer excess coefficient α in the range from 0.8 to 1.1 and for different conditions in the combustor and MHD channel. The choice of the optimal formula of pyrotechnic fuel for use in experiments is analyzed and validated. The structural scheme and description are given of the Pamir-0-KT experimental facility. The operating time of the MHD facility was 3.6 s, with the flow rate of combustion products of about 2 kg/s at a pressure in the plasma generator of p ch ≈ 4 MPa. The maximal value of the MHD-channel cross-section average plasma conductivity of 23 S/m at an electron mobility of 0.45 T -1 is obtained for the composition of pyrotechnic fuel of 64%Mg+35%KNO 3 at α = 0.96, pressure of 0.08 MPa, temperature of 2700 K, and flow velocity of 1900 m/s. It is demonstrated numerically that the value of conductivity σ 0 in the flow core is at least 50 S/m. The dependences of electrode voltage drops on current density are determined. The possibility is demonstrated of non-contracted flow of current to the surface of "cold" (800 K) electrode at average current densities up to 3×10 4 A/m 2 and α ≈ 0.9.

Evaporation of additive droplets in a pulse MHD generator

“…Reactions (1) and (3) proceed at the sur face of the droplet and within it. Further, it is believed that the content of water vapors in combustion prod ucts is substantially greater (~10% [4]) than that of additives (~1% [3]). Therefore, reaction (2) becomes possible.…”

“…To solve problems related to the application of solid rocket propellant in pulse MHD generators, powdered fuels based on carbon and metals (aluminum and magnesium) were proposed [3]. The oxidizing agent in this case is air or oxygen.…”

“…Powdered fuels give the possibility for deep control of the MHD generator power by vari ation in the component consumption and provide for its long operation. In addition, the fuel based on pow dered carbon is substantially less expensive than the solid rocket propellant [3]. In the case of the operation of the pulse MHD generator on powdered fuels, an additive (K 2 CO 3 or Cs 2 CO 3 ) is introduced in the chamber also in dispersed form.…”