| Contra-rotating |
Website Links For Propellers |
Information AboutContra-rotating |
| CATEGORIES ABOUT CONTRA-ROTATING PROPELLERS | |
| aircraft engines | |
| aircraft configurations | |
| propellers | |
|
Contra-rotating propellers, also referred to as ''coaxial contrarotating propellers'', are a complex way of applying the maximum power of a single Piston or Turboprop Aircraft Engine . Contra-rotating propellers are common in some marine transmission systems, in particular for medium to large size planing leisure crafts. Two Propeller s are arranged one behind the other, and power is transferred from the engine via a Planetary Gear Transmission . The configuration can also be used in Helicopter designs, where similar issues and principles of torque apply. When airspeed is low the Mass of the air going back through the propeller disk ( Thrust ) causes a significant amount of Tangential or rotational air flow to be created by the spinning blades. The energy of this tangential air flow is wasted in a single propeller design. To use this wasted effort the placement of a second propeller behind the first takes advantage of the already-disturbed airflow. If it is well-designed, a contra-rotating propeller will have no rotational air flow, pushing a maximum amount of air Uniformly through the propeller disk — resulting in high performance and low induced energy loss. It also serves to counter the Asymmetrical Torque effect felt from a conventional propeller. Some contra-rotating systems were designed to be used at take off, for maximum power and efficiency, allowing one of the twin propellers to be disabled during cruise to extend flight patrol time. The efficiency of a contra-rotating prop is somewhat offset by the mechanical complexity that comes with its design however. Nonetheless, contra-rotating propellers and Rotor s are moderately common in both the Military Aerospace industry and in Naval armaments such as Torpedo es, where the added maintenance is not a concern to government budgets. SIGNIFICANT AIRCRAFT helicopter]] While several nations experimented with contra-rotating propellers in aircraft, only the United Kingdom and Soviet Union produced them in large numbers. The U.S. worked with several prototypes, including the Tail-sitting Convair XFY and Lockheed XFV "Pogo" VTOL fighters, but Jet Engine technology was advancing rapidly and the designs were deemed unnecessary. Kaman Aircraft designed the H-43 Huskie and K-Max light utility helicopter with intermeshing contra-rotating blades. The British felt otherwise, however; some of the more successful British aircraft with contra-rotating propellers are the Avro Shackleton MR Mk 3 , powered by the Rolls-Royce Griffon engine, and the Fairey Gannet , which used the Double Mamba Mk.101 engine. Later variants of the Supermarine Spitfire and Seafire used the Griffon with contra-rotating props as well. In the Spitfire/Seafire and Shackleton's case the primary reason for using contra-rotating propellers was so as to increase the propeller blade-area, and hence absorb greater engine power, within a propeller diameter limited by the height of the aircraft's Undercarriage . Whilst this also applied to the Gannet, in addition this aircraft's engine had two separate power-sections each driving one propeller. Soviet and Russian s produced a large number of contra-rotating helicopters and aircraft. The Yak EG Kamov Ka-25 , Ka-32 , and Ka-50 Blackshark are particularly prominent examples. Helicopters have no need for a Tail Rotor when equipped with contra-rotating rotors, as the two rotors cancel out each others' angular momentum; this aids maneuverability and allows the design to be more compact. The Kamov Design Bureau in particular is virtually trademarked by contra-rotating rotor configurations at it appears in the majority of the firm's designs. An especially noteworthy Soviet design was the the Ukrainian design bureau Antonov is nearing certification of the An-70 heavy transport, powered by contra-rotating Propfan s. MARINE PROPULSION Contra-rotating propellers have benefits in providing thrust for boats too, for the same reasons. have launched the IPS (Inboard Performance System), an integrated diesel, transmission and pulling contra-rotating propellers for motor yachts. External links
|
|
|