Supersonic Compression Research Articles

Asymptotic solutions of the energy equation for viscous supersonic flow past corners

When a compressible laminar boundary layer encounters a corner, a viscous-inviscid interaction occurs. The correct mathematical structure for such interactions at large Reynolds numbers is provided by the asymptotic triple-deck theory. Within this framework, solutions of the energy equation for supersonic flow past compression and expansion corners are considered. The limiting structure for far upstream and downstream temperature profiles is examined and a linearized solution for wall heat transfer is derived for very small corner angles. For corners of larger angles, numerical solutions of the energy equation are presented, including cases with separation.

Pressure Recovery in a Diffuser for Gas Centrifuge

The pressure recovery of supersonic flow at very low density was studied in a vane-island type diffuser for gas centrifuge. A tester of diffuser with a rapidly rotating cylinder was used in experiments. Wall static pressures were measured at many points in the diffuser to observe the static pressure distribution. The change of pressure distribution with back pressure and the effect of flow rate were investigated. Pressure distribution showed that the pressure recovery occurred in the converging section. The pressure ratio increased linearly with the back pressure in this experimental range and the effect of flow rate was not observed. A numerical analysis of the pressure recovery in the channel section of the diffuser was made by applying the finite difference method to the slender-channel equations. The pressure distribution obtained in experiments could be explained as a result of supersonic compression with reverse flow.

Pressure Recovery in a Diffuser for Gas Centrifuge

The pressure recovery of supersonic flow at very low density was studied in a vane-island type diffuser for gas centrifuge. A tester of diffuser with a rapidly rotating cylinder was used in experiments. Wall static pressures were measured at many points in the diffuser to observe the static pressure distribution. The change of pressure distribution with back pressure and the effect of flow rate were investigated. Pressure distribution showed that the pressure recovery occurred in the converging section. The pressure ratio increased linearly with the back pressure in this experimental range and the effect of flow rate was not observed. A numerical analysis of the pressure recovery in the channel section of the diffuser was made by applying the finite difference method to the slender-channel equations. The pressure distribution obtained in experiments could be explained as a result of supersonic compression with reverse flow.

On the effect of kinetics of elementary reactions on ionization in stationary and nonstationary supersonic expansion and compression of gases

Investigations are presented which determine the degree of ionization of air in the absence and presence of alkali metal impurity for different laws of supersonic expansion for the range of the initial temperature in adiabatic expansion flow 2000 ≤T 0 ≤6000 o K, pressure 1.0≤ P 0 ≤100 atm and impurity content 10 −4 ≤ α Na ≤10 −2 . The results of the calculations indicate a significant departure of the ionization from equilibrium during the supersonic expansion (in the range 1.2≤ σ ≤10 at 1 cm ≤ l 0 ≤100 cm) and allowed the determination of the dependence of the ionization on the initial parameters, the law of the gasdynamic expansion, and a specific size of flow l 0 . It is shown that there is a flow region for some range of σ with a gradual transition from equilibrium ionization towards the frozen state while the size of the region significantly depends on the law of gasdynamic expansion. For example, the region of transition of σ for axisymmetric source is less by two or three times than for the conical nozzle with a small diverging angle. The latter condition results in the fact that for supersonic flow and during the expansion of the supersonic stream into vacuum., the limit of ionization is maximum and causes the creation of flow regions with negative dielectric constant. For laws of expansion with slower variation of σ=f(l) , during the flow in nozzles and the flow over a blunt body, it is typical that there exists a wide range of σ with insignificant deviation of α from the equilibrium value. At the same time the limit of the degree of ionization is significantly less than for the flow in a supersonic source. For example, at the initial values in the adiabatic expansion, flow T 0 =6000 o K, P 0 =1 atm, the ionization limit of air for the supersonic source is three or two and a half times greater than that during the expansion in the supersonic conical nozzle, ξ=10 o . Similar relations hold also in the presence of lakali metal impurity in the air but the limit of ionization is set in this case at greater values of σ.