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helicopter Engine
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helicopter Engine

helicopter Engine

 

 

The engine of the helicopter is used for rotation of the rotor. If there are several helicopter rotors, they may be rotated by a common motor or from a separate motor, but so that the rotation of the screws was strictly synchronized.

Assignment engine helicopter differs from the purpose of the engine on the aircraft, a gyroplane, airship, as in the first case, he rotates the rotor through which creates both thrust and lift, in other cases, it rotates the tractor propeller, creating only thrust "whether the reaction force of the gas jet (a jet) also gives only traction.

If a helicopter mounted reciprocating engine, in its design must take into account several features inherent in the helicopter.

 

Engine helicopter 2

The engine of the helicopter

 

The helicopter can fly in the absence of forward speed, t. E. Hanging motionless relative to the air. In this case, there is no airflow and engine cooling, water-radiator and oil cooler, resulting in possible overheating of the engine and its failure. Therefore, the helicopter engine is not advisable to use water and air cooling, as the latter does not require heavy and bulky liquid cooling system, for which a helicopter would take a very large cooling surface.

Engine air cooling, usually mounted in a helicopter in a tunnel should be driven fan forced airflow that cools the engine in the hover and forward flight when the rate is relatively low.

In the same tunnel installed oil cooler. Adjusting the temperature and the engine oil may be achieved by changing the value of the input or output openings of the tunnel by means of movable flaps, controlled from the cockpit by hand or automatically.

Aircraft piston engine generally has a nominal speed of about 2000 minute. It is understood that the total number of revolutions of the engine can not be transmitted to the screw, as this will limit the speed of the blades so large that cause the appearance of a high-speed stall. For these reasons, the number of M on the ends of the blades should not be more than 0,7-0,8. Furthermore, at high rotor centrifugal forces would heavy construction.

Calculate what the maximum allowable rotor speed 12 m in diameter, where the number M is less than the ends of the blades for the 0,7 5000 altitude in meters at a speed of flight 180 km / h,

 

Engine helicopter 2

The engine of the helicopter

 

So engine helicopter must have a gearbox with a high degree of reduction.

The aircraft engine always rigidly connected to the screw. Durable, all-metal screw small diameter can easily withstand jerks accompanying the launch of the piston engine, when he abruptly gaining several hundred rpm. Helicopter rotor having a large diameter, spaced away from the axis of rotation of the mass n, therefore, a large moment of inertia, is not designed for load abrupt change in the plane of rotation; startup may cause damage to the blades of the starting jerk.

Therefore it is necessary to start at the main rotor of the helicopter has been disconnected from the engine, t. E. The engine must run idle without load. Typically, this is accomplished by introducing to the engine friction and jaw clutch.

Before starting the engine, the clutch should be switched off while the rotation of the motor shaft and rotor is not transmitted.

However, the no-load motor can develop a very large turnover (to promotion), which will cause its destruction. Therefore, when you start to engage the clutches can not fully open the throttle and the engine carburetor exceed the set number of turns.

 

helicopter Engine

The engine of the helicopter

 

When the engine is already running, you must connect it to the rotor by means of a friction clutch.

As a friction clutch, a hydraulic clutch consisting of several metal discs coated with a material with a high coefficient of friction can serve. Some of the discs are connected to the shaft of the motor reducer, and intermediate discs are connected to the main shaft drive to the rotor. Until the discs are compressed, they rotate freely relative to each other. Compression of disks is carried out by the piston. Supplying oil with high pressure under the piston causes the piston to move and gradually compress the disks. At the same time, the torque from the engine is transferred to the screw gradually, gradually unwinding the screw.

Revolution counters installed in the cab, indicates the number of revolutions of the engine and propeller. When the engine RPM and propeller are equal, it means that drives the hydraulic clutch tight against each other and it can be assumed that the clutch is connected by rigid type couplings. At this point, it can be smoothly (without jerks) including cam sleeve.

Finally, to allow the autorotation, the rotor is necessary, the screw is automatically disconnected from the engine. As long as the engine is running and the screw rotates, the cam clutch is engaged. When the engine failure of its turnover decrease rapidly, but the rotor for a while by inertia continues to rotate with the same speed; at this point dog clutch disengages.

Rotor detached from the engine can then continue rotation mode, autorotation.

Flight in the mode of self-rotation with training purposes is performed with the engine off or with the engine running, in the latter case its speed is reduced so that the screw (taking into account the reduction) makes a greater number of revolutions than the crankshaft of the engine.

After landing the helicopter engine speed is first reduced, turn off the clutch, and then stops the engine. When parked helicopter propeller should always be inhibited, or he can start to rotate in the wind.

 

Engine helicopter 434

The engine of the helicopter

 

Engine power helicopters spent on overcoming the resistance of rotation of the rotor, the rotation of the tail rotor (6-8%), the rotation of the fan (4-6%) and to overcome the losses in the transmission (5-7%).

Thus, the rotor does not use all the power of the engine, only part of it. Using a screw motor power factor is taken into account, which shows how much of the power of the engine uses a rotor. The higher the ratio, the more perfect the design of the helicopter. Usually = 0,8, t. E. The screw using 80% engine power:

Power reciprocating engine dependent on the weight of the charge air drawn into the cylinders, or the density of the surrounding air. Due to the fact that, by raising the height of the ambient air density decreases continuously as the engine power drops. This engine is called nevysotnogo. With raised to a height of 5000-6000 th power of the engine is reduced by about half.

Up to a certain height not only the power of the engine falls, and even increasing, the suction line to the engine air blower put, increasing the density of intake air. Due to the blower motor power to a certain height, called the estimated increases, and then decreases in the same manner as in nevysotnogo.

The supercharger is driven in rotation by the crankshaft of the engine room. If transmission from the crankshaft to the supercharger has two speeds, and when the second speed increasing momentum blower, then a show at the height you can double provides increased capacity. This engine has already calculated the height of the two.

Helicopters usually installed engines with superchargers.

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About the liquid cooling system nya :) Is it possible to provide the engine with an enhanced system of measures? For example, if the temperature of the working chamber is high, and a strong heat exchanger must be created, with a small usual area. For example, to remove heat from the working area at first with a compressed substance, since in this case the heat transfer under pressure will be much stronger, etc., that in occasion of the load0 I want to propose a multifriction channel that will work at higher speeds and in case of emergency acceleration, the channel will overlap and additional power will go into compression karoch

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