Experimental investigations of spatial flows in nozzles of jet engines

Аuthors

Zaikovskii V. N.

Federal State Budgetary Institute of Science Khristianovich Institute of Theoretical and Applied Mechanics Siberian Branch of the Russian Academy of Sciences, 4/1, Institutskaya str., Novosibirsk, 630090, Russia

e-mail: zakkoskii@itam.nsc.ru

Abstract

The paper describes investigations of formation of large-scale longitudinal counter-rotating structures in the airflow duct of the subsonic and supersonic parts of nozzles of jet engines. The reason for their emergence is interaction of impinging jet flows with curvilinear surfaces in the transonic part of the nozzle. The governing effect of the free-stream velocity on the vortex intensity is demonstrated. The presence of spatial structures affects heat and mass transfer, as well as erosion of the inner surfaces of the engine duct. Three types of such spatial structures were investigated experimentally.

The first group includes spatial vortices observed in the free space behind solid-propellant charges with star-shaped channels, which were widely used in solid-propellant rocket engines. Based on experimental data, methods of effective suppression of the adverse effect induced by these structures were proposed.

Further, the results of ITAM SB RAS studies were considered, where formation of large-scale vortices in the free space behind the solid-propellant charge with a duct having a circular cross section was shown. The presence of solid-propellant charges with channels of different configurations in the engine duct inevitably leads to generation of spatial structures of different intensities.

The third type includes large-scale paired vortices formed in the nozzle with a permeable supersonic bell mouth. The following vortex formation mechanism is implied. Zones of gas ejection and injection are formed in the nozzle with a porous wall at a certain pressure in the settling chamber. A change in the flow regime leads to positive curvature of the streamlines. As the gas flow near the wall has a negative gradient ∂u/∂r < 0, this leads to violation of equilibrium between the pressure gradient and the centrifugal force. As a result, instability starts to form in the flow, which is finalized by formation of large-scale longitudinal vortices.

Keywords:

longitudinal vortexes, jet engine, supersonic engines, stream flows, heat and mass exchange, erosion, vortexes intensity, star shape, ridged surface

References

1. A.A.Kuraev., A.D.Kuraeva.,B.N.Petrova Emegence of shock waves in nozzles with vortices passing through the throat // Gas Dynamics and Physical Kinetics — Novosibirsk, 1974, рр. 90 — 91.

2. B.M. Melamed., V.N. Zaikovskii An experimental investigation of vortex structures in SRM duct with a star — shaped channel // Intern.Conf.on the Methods of Aerophys. Reseachr: Proc. Pt1. Novosibirsk, 2000. рр. 147 — 151.

3. V.N. Zaikovskii Materialy VII Mezhdunarodnoi konferentsii «Ustoichivost’ techenii gomogennykh i geterogennykh zhidkostei». Novosibirsk, 2000, issue 7, pp.183 — 186.

4. V.N. Zaikovskii, S.P. Kiselev, V.P. Kiselev Prikladnaya mekhanika i tekhnicheskaya fizika. 2005.vol. 46. no. 5. pp.68 — 75.

Download