7. Theoretical Models of Sound Speed Increase Effects in Gas Duct with Corrugated Wall

7. Theoretical Models of Sound Speed Increase Effects in Gas Duct with Corrugated Wall

Konokh V. I., Shevchenko S. A., Grigor’ev A. L.

Yangel Yuzhnoye State Design Office, Dnipro, Ukraine

National Technical University “Kharkiv Polytechnic Institute”, Kharkiv, Ukraine

Kosm. teh. Raket. vooruž. 2018, (2); 57-67
Language: Russian
During experimental investigation of the dynamic characteristics of a pneumatic test bench for testing liquid rocket engine high-flowrate automatic units, the effect was detected of 20-35% sound speed increase in the gas flow moving along the channel with corrugated wall (metal hose) which is a part of test bench drain system. The article presents the results of experiments and the task of theoretical justification of the effect is solved. It is indicated that its causes may be two mutually complementary factors – a decrease of gas compressibility at eddy motion and oscillations of metal hose wall. The physical model is considered that describes variation of gas elasticity and density in the conditions of high flow vorticity. It is supposed that in the near-wall layer of the channel, toroidal vortexes (vortex rings) are formed, which move into turbulent core of the flow where their size decreases and the velocity of rotation around the ring axis of torus increases. The spiral shape of the corrugation ensures also axial rotation, which increases vortexes stability. The intensive rotation around the ring axis creates considerable centrifugal forces; as a result, the dependence of pressure on gas density and the sound speed increase. The mathematical model has been developed that describes coupled longitudinal-lateral oscillations of gas and channel’s corrugated shell. It is indicated that in the investigated system, two mutually influencing wave types are present – longitudinal, which mainly transfer gas pressure pulses along the channel and lateral ones, which transfer the shell radial deformation pulses. As a result of modeling, it has been ascertained that because of the lateral oscillations of the wall, the propagation rate of gas pressure longitudinal waves (having the same wave length as in the experiments at test bench) turns out to be higher than adiabatic sound speed.
Key words: rocket engine automatic units, pneumatic test bench, metal hose, corrugated shell, toroidal vortex, longitudinal-lateral oscillations


1. Shevchenko S. A. Experimental Investigation of Dynamic Characteristics of Gas Pressure Regulator in Multiple Ignition LRE Starting System. Problems of Designing and Manufacturing Flying Vehicle Structures: Collection of scientific works. 2015. Issue 4 (84). P. 49-68.
2. Shevchenko S. A., Valivakhin S. A. Results of Mathematical Modeling of Transient Processes in Gas Pressure Regulator. NTU “KhPI” News. 2014. No. 39 (1082). P. 198-206.
3. Shevchenko S. A., Valivakhin S. A. Mathematical Model of Gas Pressure Regulator. NTU “KhPI” News. 2014. No. 38 (1061). P. 195-209.
4. Shevchenko S. A., Konokh V. I., Makoter A. P. Gas Dynamic Resistance and Sound Speed in Channel with Corrugated Wall. NTU “KhPI” News. 2016. No. 20 (1192). P. 94-101.
5. Flexible Metal Hoses. Catalogue. Ufimsky Aggregate Company “Hydraulics”, 2001.
6. Loytsyansky L.G. Liquid and Gas Mechanics. М., 1978. 736 p.
7. Prisnyakov V. F. et al. Determination of Gas Parameters at Vessel Emptying Taking into Account Compressibility and Manifold Resistance. Problems of High-Temperature Engineering: Collection of scientific works. 1981. P. 86-94.
8. Kirillin V. A., Sychyov V. V., Sheydlin A. E. Technical Thermodynamics. М., 2008. 486 p.
9. Grekhov L. V., Ivashchenko N. A., Markov V. A. Propellant Equipment and Control Systems of Diesels. М., 2004. 344 p.
10. Sychyov V. V., Vasserman A. A., Kozlov A. D. et al. Thermodynamic Properties of Air. М., 1978. 276 p.
11. Shariff K., Leonard A. Vortex rings. Annu. Rev. Fluid Mech. 1992. Vol. 24. P. 235-279. https://doi.org/10.1146/annurev.fl.24.010192.001315
12. Saffman F. Vortex Dynamics. М., 2000. 376 p.
13. Akhmetov D. G. Formation and Basic Parameters of Vortex Rings. Applied Mechanics and Theoretical Physics. 2001. Vol. 42, No 5. P. 70–83.
14. Shevchenko S. A., Grigor’yev A. L., Stepanov M. S. Refinement of Invariant Method for Calculation of Gas Dynamic Parameters in Rocket Engine Starting Pneumatic System Pipelines. NTU “KhPI” News. 2015. No. 6 (1115). P. 156-181.

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