Turboprop rotation frequency stabilization while its testing together with water brake

Аuthors

Gimavied A. G.^1*, Bukin V. A.², Gareev A. M.^1**, Greshnyakov P. I.^1***, Kutuev S. S.^1****

1. Samara National Research University named after Academician S.P. Korolev, 34, Moskovskoye shosse, Samara, 443086, Russia
2. “Kuznetsov”, 29, Zavodskoye shosse, Samara, 443009, Russia

*e-mail: gimadiev_ag@mail.ru
**e-mail: gareyev@ssau.ru
***e-mail: pavel.ssau@gmail.com
****e-mail: kutuevstas@outlook.com

Abstract

While a turboprop design and operation a necessity occurs to determine their developed power and compressor gas-dynamic stability margin. Depending on the engine power water brake, electric and other installations are employed. However, water brake which shaft was connected to the turbo-compressor shaft through the clutch, was traditionally employed for the powerful engines. Disturbances from the water brake side in the form of water pressure (consumption) oscillations often occur while the engine testing. These disturbances lead to its rotor rotation frequency oscillations, which do not allow accurate determining the engine power or the compressor stability margin. The available information on stability provision of the engine rotation frequency while its testing on hydraulic braking installation, is insufficient. The article presents results of theoretical and experimental studies of speed oscillations of the turboprop engine rotor connected with the water brake. It is shown that in the engine-water brake system, the torque oscillations are excited by the frequencies:

– rotary frequency of 140 Hz;

– resonance of the water brake frame with the engine of 14.5...15.5 Hz;

– fluctuations of water in the water brake supply pipes of 3...5 Hz;

– the processes in the water brake rotating disk cavities and the of the test bench hydro mechanical engine speed regulator functioning of 0.15 ... 0.30 Hz.

Oscillations of the engine rotor speed occur in the low frequency range of 0.15...0.30 Hz due to its inertia. From all measures of the engine rotor speed stabilization, the best result was achieved by employing hydraulic dampers for pressure fluctuations at the inlets of water brake throttle valves. It ensured the amplitude of the engine rotor rotation frequency oscillations at 15...25 rpm at maximum mode, and the joint point of operation of the engine with water brakes. However, when determining the compressor gas-dynamic stability margin, an oscillatory process is observed, slightly exceeding the permissible amplitude values. Further turboprop engine rotor speed stabilization at this water brake installation, at which the compressor gas-dynamic stability margin determining is possible, can be performed by improving its test bench system for engine speed automatic regulation.

Keywords:

engine, water brake, torque, rotation frequency, tests, oscillations, absorber, analysis

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