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Jet drive a helicopter rotor
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Jet drive a helicopter rotor

Jet drive a helicopter rotor

 

 

The main difference between the jet engine of the piston is in a jet engine the energy of combustible fuel is used to create a traction force directly, by dropping back with high velocity air and combustion products, whereas in a piston engine energy combusted fuel is used to rotate the propeller, which creates with the necessary traction for movement.

From this, we can conclude that the easiest way of rotation of the main rotor of the helicopter by means of jet engines is the installation at the ends of the blades of the rotor.

Therefore, the thrust of each engine must be equal 38,2 kg. Jet engine with the thrust will weigh quite a bit about 10 kg. The weight of all three engines will be 30 kg.

In single-rotor helicopter with tail rotor weight 1500 kg weight of the engine will be about 300 kg, and the weight of the transmission - about 100 kg.

When compared with a helicopter jet engine helicopter, having a piston engine, the difference in weight of their composition for this example 370 kg. Due to this difference can be increased fuel capacity. As a result, the range of the jet engine, despite the high cost of fuel, can be the same as a helicopter with a piston engine. Using a helicopter jet at small distances by the incomplete filling of fuel can significantly increase its capacity.

The propulsion drive of the main rotor has many advantages over the piston engine drive. When installing jet engines at the ends of the blades, there is absolutely no need for transmissions, i.e. gearboxes, shafts, etc. For such a helicopter, the helmsman's screw is needed only for providing the track control, since there is no reactive torque from the screw to the fuselage, On the screw itself; In this case the steering screw will consume less power, since its diameter will be small. The weight of the helicopter as a whole will be much less. So, in the case of using a single-jet jet engine instead of a piston engine, the weight of a helicopter with the same lifting capacity will be about 30 ° / o less.

However, along with the jet drive is typical number of shortcomings. The main one is that the jet engines have low efficiency, leading to higher fuel consumption. Moreover, the jet drive is difficult to implement, since

it is necessary to simultaneously satisfy a number of conflicting requirements.

If at the end of the rotor blade mounted jet engine, the change of the blade setting angle results in a change in the direction of the engine thrust. For example, by increasing the setting angle a thrust no longer lies in the plane of rotation, and make it a certain angle a, so that the thrust will give two components: in-plane rotation that will generate torque, and the rotational axis of the screw, which go directly to increase the lift and increase the angle of the blade stroke.

The magnitude of these components traction during one revolution will change all the time, which will cause the appearance of a large vibration of the helicopter. To eliminate this drawback, it is necessary to mount the engine on a rod or tube around which the movable blade is positioned so as to change the angle of attack of the blade going around this rod or pipe without deviating the axis of the engine.

The pipe may serve as backbone for supplying fuel to jet engines.

The difficulty installing the motor at the ends of the rotor blades is also that the jet engine is operating with a high effect only at high peripheral speed of the blades, since in this case, a sufficient dynamic pressure at the inlet of the diffuser of the engine. On the other hand, the large circumferential speed leads to the fact that on the profile of the blades stall flow arises, which reduces the efficiency of the propeller.

However, this is far from all difficulties. No matter how light a jet engine is, it is a concentrated load on the tip of the blade and greatly increases the centrifugal force tending to break the blade. Therefore, compared to a rotor-driven rotor from a reciprocating engine, the strength of the rotor blades with jet engines should be increased. In addition, the separation of the masses of the blades from the axis of rotation creates a large moment of inertia of the screw, and the resistance force of the engine, which is at a great distance from the axis, creates a great moment of resistance. All this, taken together, worsens the ability of the main rotor to self-rotate during the transition to a non-motor flight in the event of failure of jet engines.

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A major drawback of existing models with jet propulsion is the need for a tail propeller, which makes the design in principle not differ from the classical scheme with a tail-compensator, from which it would be desirable to get rid of as a very uncomfortable element. To achieve the possibility of controlling a helicopter without a tail rotor. For this, the screw must for some time not work on the jet drive; It is possible, by making a gas generating plant outside the screw itself, to start its gases first through the active turbine on the axis of the screw, and then to withdraw it into the blades with jet nozzles. To change the operating modes of the system before the gas channels, to make the dampers, which will temporarily disable reactive compensation, this will ensure Turn the helicopter.

It is clear that the direction has been closed. "Do not let it happen."

Problems of construction look like routine tasks for designers, developers, and served as the fundamental law of conservation of the type of barriers. Limit jet engine can be made easier; You can penetrate the blade rope, on which to string airfoil and which will take over the load; the engine itself can provide additional steering planes turn it into airplane-lift, the benefit of the microprocessor pull any complex control algorithm ... and so on.

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