Computational-experimental studies of tail rotor characteristics at helicopter yawing rotation mode

Аuthors

Leont'ev V. A.^1*, Krymskii V. S.^2**, Ignatkin Y. M.^2***, Makeev P. V.^****

1. Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia
2. Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

*e-mail: spintest@tsagi.ru
**e-mail: vovan5490@yandex.ru
***e-mail: k102@mai.ru; ignatkinym@mai.ru
****e-mail: vaultcity13@gmail.com

Abstract

In this paper, the computational-experimental studies results of the tail rotor (TR) aerodynamic characteristics at the helicopter yawing rotation mode, at hover are shown.

The experimental studies have been carried out by using the experimental model, developed in TsAGI. The experimental model main rotor (MR) diameter D_MR=2,5 m, the tail rotor diameter D_TR=0,586 m. The computational studies have been carried out using two models: the helicopter mathematical model, developed by TsAGI and the non-linear blade vortical model of a rotor, created by «Helicopter Design» department of MAI.

The computational-experimental relationships between the tail rotor thrust coefficient С_t and a yaw angular velocity ω_у of the helicopter model showed, that for small values of the tail rotor pitch about φ_TR=3,8º an increase of ω_у resulted in С_t increase, however starting from the tail rotor pitch φ_TR=9,2º and higher, the coefficient С_t decreased. The experimental results confirm the analytical and the mathematical modeling results in the paper [10].

Analysis of the computational-experimental studies results showed that when the angular velocity ω_у is growing TR blades are subjected to high Coriolis forces in addition to aerodynamic forces. Coriolis forces have different direction from one side of the TR to the other and therefore, flapping motion of the TR is increasing. By reaching some rotation rate ω_у, one side of the TR goes beyond stall, hence the TR thrust ceases to increase. On the other side of the TR blades angles of attack decrease reducing the total TR thrust.

The computational relationships С_t=f(ω_у) and m_k=f(ω_у) of the TR at the helicopter yawing rotation mode with the MR are in general agreement with the experimental results. They show that the MR vortex wake insignificantly affects on the TR aerodynamic characteristics.

Keywords:

single-rotor helicopter, hover, yawing rotation, main rotor, tail rotor, interference of rotors, experiment, computational studies

References

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