MiG-21 Engines

The described engine is a modified version of the basic R-11 engine (R-11-37F-2S, short: R-11), the one of the MiG-21PFM/SPS/some M's and MiG-21US (Type 94, Type 68). However, it is very similar to the one (R-13F25-300, short: R-13) used in MiG-21MF. The MiG-21BIS has the R-25 engine which significantly differs from the previous R-11/13's. I'll add the R-25 schematics at a later time.

The Tumansky R-11 engine is an axial-flow two- spool turbojet with modulated afterburner. The compressor is twin- section twin-shaft construction with three-stage first (low pressure section) and three-stage second (high pressure) section. The combustion chamber has ten annular combustion liners. The turbine is also of twin-section twin-shaft construction. The front turbine section is on a common shaft with the second compressor section and the rear turbine section on a common shaft with the first compressor section.

The variable convergent nozzle is Iocated behind the afterburner. The Iow-pressure shaft is hinged by three bearings (front main roller bearing, middle auxiliary ball bearing and rear auxiliary roller bearing). The high pressure shaft is hinged by two main ball bearings in the shaft center and one main roller bearing in the rear shaft section. The auxiliary gear box is driven by a high-pressure shaft. The front oil pump is driven by a low-pressure shaft. The starter/generator drives the engine by multiple disc clutch and by ratchet or roller clutch.

The convergent variable nozzle optimalises jet engine power output. It has minimal diameter at maximal power without afterburner and from middle to full open diameter with afterburner on. The nozzle is also full open in engine idle power. The engine lubrication system consists of an oil tank, a pump with reduction and safety valves, jets, a suction pump, filters, coolers, and a pressure sensor.