J79 versus AL-21

Read the forum code of contact

Member for

24 years 2 months

Posts: 805

I was under the impression the AL-21 was based on the J79 engine, specifically it copied the variable stator design. Looking at the specs, the AL-21 seems to be a physical copy as well.

According to Wikipedia their dimensions and weight were practically identical. However AL-21 delivers far more thrust. 6.6:1 compared to the J79's 4.6:1. The performance puts it in almost a different generation. What advancements does the Soviet engine have to account for this?

J79-GE-17

Length: 17.4 ft (5.3 m)
Diameter: 3.2 ft (1.0 m)
Dry weight: 3,850 lb (1,750 kg)

11,905 lbf (52.9 kN) dry
17,835 lbf (79.3 kN) with afterburner
Thrust-to-weight ratio: 4.6:1 (45.4 N/kg)
_____________

AL-21F3

Length: 5,300 mm (209 in)
Diameter: 1,000 mm (39 in)
Dry weight: 1,700 kg (3,740 lb)

76.4 kN (17,175 lbf) dry
109.8 kN (24,675 lbf) with afterburner
Thrust-to-weight ratio: 64.7 N/kg (6.6:1)

Original post

Member for

24 years 2 months

Posts: 1,437

J-79-8 configuration: 17 stage compressor, 3 stage turbine
AL-21F-3A configuration: 14 stage compressor, 3 stage turbine

J-79-8 length: 5.3m
AL-21F-3A length: 5.16m

J-79-8 compression ratio: 13:1
AL-21F-3A compression ratio: 14.55:1

J-79-8 Mass flow: 76.7kg/sec
AL-21F-3A Mass flow: 104kg/sec

J-79 turbine entry temperature: 954°C
AL-21F-3A turbine entry temperature: 1093°C

No great magic - it sucks in more air, compresses it more, and burns it hotter. AL-21F is a later design and superior in all respects. It used some technology from recovered J-79s, but it is certainly NOT the same design. Its compressor is much more advanced getting more compression from less stages.

Member for

13 years 9 months

Posts: 33

In the AL-21F is used the alloy "ЖС6U" in turbine blades?