Працездатність підшипників ковзання як опор шестерень основного паливного насосу ГТД

Abstract

The paper is about the performance capability of the journal bearings as a support of the fuel gear pump for gas turbine engines (GTE). Supports of the external gear pump usually operate in semi-dry friction conditions, which reduces residual life and is one of the limiting factors. For this investigation, the serial gear pump was chosen with the following parameters: the number of teeth z = 14, module m = 3.8, gear-loading Р = 7800 N. The authors have studied options for a pump with an electrical and mechanical (from the rotor of the GTE) drive. The main criterion for studying the bearing capacity is the minimum thickness of the working layer of a fluid with low viscosity (kerosene). For modeling, a common theory is used based on solutions of differential equations of the viscous fluid hydrodynamics, which relate pressure, velocity, and viscous shear resistance. For technological reasons, the minimum allowable kerosene layer is limited to 5 μm. The conducted analysis considers the multi-lobe (2-, 3- and 4-lobe) bearings with different lobe orientations relative to the force vector. It was found that the 2-lobe bearing has the best load capacity (provides the largest layer of kerosene). According to the results of the previous investigation for further work, the 2-lobe bearing was chosen. The influence of load, setting gap, eccentricity, the specific radius of lobe curvature, shaft length on the bearing load capacity was analyzed. A rational type of bearing design was proposed based on the load capacity criterion (the minimum layer of working fluid). It was shown that the hydrodynamic 2-lobe bearing can be sufficiently effective for the supports of the gear fuel pumps of GTE. Based on the results of the investigation, 2 variants of the pumping unit designs were proposed. The first one for the pump driven by the gas turbine engine rotor with parameters z = 19, m = 3.3, gears width B = 34, shaft diameter DS = 48, and shaft length LS = 56 (P = 10.2kN). The second one for the electrically driven pump, z = 28, m = 1,8, B = 15, DS = 34, and LS = 41 (P = 3.8 kN). The minimum angular velocity for the pump variants is 470 and 1055 rad/s, respectively. According to the investigation results, it was proposed to conduct related studies of the working process in pumps and bearings.