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Numerical modeling of operation of high-pressure detonation MHD-generator
Derevianko V. V.
Thermophysics and Aeromechanics, 2001, Vol. 8, No. 3
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Abstract
The numerical modeling of the operation of a detonation MHD generator with T-layer has been performed at large pressures in the duct. It is shown that the radiation absorption inside the T-layer leads to a considerable varia-tion of the layer characteristics, increase in the specific power and generator efficiency.
Introduction
As was shown in [1], at the duct pressures P ≥100 atm. the effect of radiation choking is manifested in the T-layer of the detonation MHD generator.
In this connection, a correct consideration of both radiation and absorption in the flow are needed.
An analysis of the operation of detonation MHD generator with T-layer at a small pressure in the flow has shown that the T-layer motion
velocity behind the detonation wave front is small in the constant section duct and decreases as the wave propagates along the channel.
Therefore, we have considered in the present computation a variable section duct enabling one to increase the flow velocity.
In the previous model of the detonation MHD generator the loading coefficient was assumed to be constant,
what was accept-able for preliminary computations. However, while passing to large pressures the initia-tion energy increases proportionally
to the pressure increase. In this connection, the use of the flow energy for the heating of T-layer is well justified. An intense heating of the latter is possible at small loading coefficients, whereas it is necessary to increase it for increasing the energy production and efficiency. This seeming contradiction is quite solvable if the loading coefficient increases at the T-layer heating.
Such a regime can be realized when using a constant loading resistance.
This is more justified also from the viewpoint of the design of the electric scheme of the MHD duct, because in this case the condition of the
absence of the voltage gradient along the continuous conductive elec-trodes is satisfied.
The gas dynamic flow characteristics at large temperature and pres-sure gradients naturally depend very strongly on the local molecular mass and the adia-batic exponent.
The ideal solution would be the use of the real gas model.
However, at the given stage with regard for problem complexity one had to restrict oneself to the politropic gas model, that is to compute the local molecular mass, and to assume the adiabatic exponent to be constant.
Its value was determined from the analysis of the g(p, T) dependence in the operation range of the pressure and temperature variation.
The task of the optimization of the generator power characteristics was not posed in the pre-sent work.
The main attention was paid to the analysis of the pressure effect on flow characteristics for the purpose of determining the direction of further research.
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