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J79 versus AL-21

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  • Multirole
    Rank 5 Registered User

    J79 versus AL-21

    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)
    pb::
  • aerospacetech
    Rank 5 Registered User

    #2
    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: 954C
    AL-21F-3A turbine entry temperature: 1093C

    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.
    Available now: my book Hawker P.1103 and P.1121: Camm's Last Fighter Projects from Blue Envoy Press

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    • mandeb48
      Rank 5 Registered User

      #3
      In the AL-21F is used the alloy "ЖС6U" in turbine blades?

      Comment

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