The paper presents results of complex research of vibration behavior of the differential reduction gear unit of a turboprop engine on the basis of statistics of products with repaired reduction gears and those placed under repair. The conducted research made it possible to establish the source of resonant oscillations of the compressor design elements leading to their breakage. It is established that this source is determined by the kinematics of the reduction gear unit and is associated with the wear of its gear teeth. Standards for the intensity of the appropriate discrete component of the reduction gear vibration spectrum and those for the amount of permissible wear are substantiated and established on the basis of the work carried out. A complex of diagnostic parameters of wear based on intensity components of the auto-spectrum and the spectrum of maxima, the depth of amplitude modulation in some narrow-band processes, their characteristics based on the parameters of the current frequency and mutual characteristics was identified. It is shown that for the whole complex of the diagnostic parameters obtained their dependence on the wear value is satisfactorily approximated by a linear characteristic. The obtained results can serve as a basis for the development of a complex of methods of differential reduction gear vibration diagnostics.

The article deals with the design of an advanced throttle valve with an elastic tubular element designed to reduce the vibration and noise of hydraulic systems upon which strict requirements for vibro-acoustic characteristics are imposed. The analysis of known similar devices is carried out and the design of the throttle valve is justified. A detailed analysis of the strained state of the elastic tubular element is performed and the relationship between the deformations of this element and the hydraulic parameters of the working medium in the flow part of the valve is shown. The experimental flow characteristics of the valve under study are analyzed. The analysis made it possible to identify the parts of the characteristics at which the flow rate remains constant when the pressure differential across the valve changes. This feature of the hydraulic characteristics of a valve with an elastic element is substantiated. Ways of further directions of the prospective valve research are shown.

The common growth criterion of fatigue cracks is offered for different degree of the biaxial tension. The specimen tension is investigated. Influence of biaxial loading on growth rate of a fatigue crack and its connection with a triaxial coefficient of a tension which can be calculated in an environ of a crack top is install.

It is shown that analyzing the signals from standard sensors of gas-turbine engine shaft speed we can resolve some issues of diagnostics of the technical condition of the reduction gearbox without installing any additional vibration transducers. It was found, in particular, that the vibration spectrum component generated by the wear of the differential reduction devices gear teeth causing resonant oscillations of the turbocharger blades produces torsional vibration at the appropriate frequency. The analysis of the parameters of the instantaneous rotational speed of the reduction gear output link (the shaft of the rear screw) made it possible to obtain some diagnostic indicators of the value of the reduction gear teeth wear on the basis of evaluation of the frequency deviations variance. It was established that the value of the diagnostic indicator is linearly dependent on the value of wear. The norm for this indicator was established for the engine under investigation. Significant influence of the load on its level was shown.

We present the results of modeling a feed water control system. The system contains two regulatory devices the feed valve to control the flow rate, with electrohydraulic control, and the throttle valve to maintain constant pressure differential on the feed valve, with hydromechanical control. The valves have perforated flow parts to reduce hydrodynamic noise and vibration, which necessitates checking the dynamical characteristics of the system. The model was developed on the basis of equations describing the electrohydraulic converter dynamics, a differential pressure meter, a servo drive and flow parts with the use of Matlab Simulink. The modeling of dynamical processes caused by various disturbance inputs and control actions showed the compliance of the system with the requirements imposed on it.