The results are given of experimental investigations of the continuous-electrode channel of a pulsed Faraday MHD generator of the Pamir type [1–4]. In the channel, the most heat-stressed inlet section is paste-cooled. The channel may be readily disassembled, which enables one to exchange the structures of both electrode and insulating walls during the runs with a view to investigating the effect of the structure on the power performance. The runs are performed with a solid-fuel plasma generator (with the pressure and temperature in the combustor of ~4.5 MPa and 3750 K) in different modes, namely, with applied electric field in order to determine the electrical conductivity of the working medium and the effect of the injection of decomposition products on the electrical conductivity, and in modes with induced field (independent excitation and self-excitation with reaching the extreme operating mode such as short-circuiting) in order to compare the power performance of the channel for different techniques of injection and removal of the cooling agent decomposition products. A sublimating pastelike cooling agent on the basis of ammonium oxalate is used. It is demonstrated that the injection of the products of decomposition of cooling agent on the insulating walls has no effect on the power performance of the channel. The experiments have revealed a high resistance and desired insulating properties of paste-cooled structures under conditions of repeated operation, as well as the agreement in the power performance between paste-cooled and uncooled channels. The obtained results point to the possibility of developing paste-cooled channels of pulsed MHD generators.

A large-scale model of the channel of a pulsed MHD generator is investigated in an applied electric field. It is demonstrated that the flow of plasma under conditions of wall protection by way of injecting the products of decomposition of a pastelike coolant is realized with a clearly pronounced core and thin boundary layers. In the case of injection on the insulating walls alone, the integral electrical conductivity of flow remains almost constant in a wide range of injection intensity up to the value of 4%. The injection into the electrode boundary layer causes a considerable reduction of its electrical conductivity

The results are given of the test development of different structural options of full-scale pastecooled modules of the insulating wall of the channel of a pulsed MHD generator of the Pamir type [1,2] under conditions of repeated heat loading in the jet of a plasma generator. Two cooling agents are employed for this development, which are characterized by different fillers, namely, ammonium oxalate and carbamide. A module in the form of a perforated cup exhibits the best results.

Without Abstract

The results are given of experimental investigation of the heat resistance of elements of the structure of the inlet portion of the paste-cooled channel of a reusable pulsed MHD generator. The gas generator is provided by a test-bed rocket engine utilizing Tonka-250 + HNO3 propellant. The basic tests are performed using the above-identified propellant with the addition of aluminum powder, this making the combustion products of such a gas generator similar to the combustion products of standard solid propellant as regards their composition and effect on structural materials. The square-throat nozzle of the engine has paste-cooled copper walls. The wall design is analogous to that of the inlet portion of the MHD channel wall. Two pastelike cooling agents are tested, namely, a carbamide-based melting agent and an ammonium oxalate-based sublimating agent. Firing tests prove the operating efficiency of the copper walls when cooled by pastelike cooling agents of the two types under conditions of repeated heat loading. The duration of a single test is 4 to 15 s, the heat flux is up to 9.5 MW/m(2), and the flow rate of the sublimating cooling agent is up to 4.8 kg/m(2) s. It is confirmed that a liquid-propellant gas generator is a convenient tool in development testing of MHD channel structures for heat resistance under conditions of repeated operation.

The results are given of experimental investigation of electrodes of different configurations (discrete bracket electrodes protruding into the flow; flat continuous electrodes made of graphite and tungsten-copper pseudoalloy) in the channel of a high-power self-excited pulsed MHD generator with the working volume V = 0.154 m(3) and the plasma now rate of 125 kg/s, It is demonstrated that the process of self-excitation is more intense in the case of bracket electrodes protruding into the flow. In the case of the maximum parameters of MI-ID interaction, the parameters in channels with discrete bracket electrodes and flat continuous electrodes, in the vicinity of which the state of the boundary layers is substantially different, are perturbed sharply (separated flows emerge) under conditions of virtually the same parameters of MHD interaction, this being indicative of the decisive effect of volume electrodynamic forces on these processes.

The results are given of experimental investigation of a Faraday-type pulsed MHD generator with discrete bracket-shaped wire electrodes protruding into the flow. The process of self-excitation is more intensive than in the case of conventional flat continuous electrodes. For the maximum parameters of MHD interaction, the parameters in channels with discrete bracket electrodes and flat continuous electrodes, in the vicinity of which the state of the boundary layers is respectively different, are perturbed sharply under conditions of virtually the same parameters of MHD interaction, this being indicative of the decisive effect of volume electrodynamic forces on these processes.