[Q&A Question 126] 2017.05.06
Thread Content
This post was last edited by 955559 on 2017-7-21 22:58. [Q&A Question 126] 2017.05.06: Why is a large-diameter flywheel required in reciprocating compressors? The reference answers will be visible after responding; points are awarded by identifying the key points. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) A flywheel, also known as an inertial wheel, has a large diameter and weight; as a result, it possesses high inertia. It is this inertia that helps to compensate for the changes in torque of the prime mover caused by variations in the force exerted by the compressor piston. This enables the piston to move evenly while keeping the prime mover torque constant. As the piston moves back and forth, the magnitude of its acceleration changes, which in turn causes the inertial force acting on the piston to vary as well. Additionally, the pressure exerted by the gas on the piston is not uniform, leading to constant changes in the load on the motor. The function of the flywheel is to balance this load on the motor. Scoring criteria: 2 Wealth points for incorrect attempts; 3–8 points for *incomplete* answers. 10 Wealth points for correct answers, provided with a detailed explanation; 15–20 Wealth points if the answer is correct but lacks sufficient details. Please score according to these criteria. 2017 Q&A Summary Thread (updates available) http://bbs.hcbbs.com/thread-1657793-1-1.html 2017 Daily Question Summary Thread (updates available) http://bbs.hcbbs.com/thread-1657794-1-1.html 2016 Q&A Summary Thread (fully updated) http://bbs.hcbbs.com/thread-1597792-1-1.html Why do reciprocating compressors require a large-diameter flywheel? The reference answers will be visible after responding; points are awarded by identifying the key points. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) A flywheel, also known as an inertial wheel, has a large diameter and weight; as a result, it possesses high inertia. It is this inertia that helps to compensate for the changes in torque of the prime mover caused by variations in the force exerted by the compressor piston. This enables the piston to move evenly while keeping the prime mover torque constant. As the piston moves back and forth, the magnitude of its acceleration changes, which in turn causes the inertial force acting on the piston to vary as well. Additionally, the pressure exerted by the gas on the piston is not uniform, leading to constant changes in the load on the motor. The function of the flywheel is to balance this load on the motor. Scoring criteria: 2 Wealth points for incorrect attempts; 3–8 points for *incomplete* answers. 10 Wealth points for correct answers, provided with a detailed explanation; 15–20 Wealth points if the answer is correct but lacks sufficient details. Please score according to these criteria. 2017 Q&A Summary Thread (updates starting now) http://bbs.hcbbs.com/thread-1657793-1-1.html 2017 Daily Question Summary Thread (updates starting now) http://bbs.hcbbs.com/thread-1657794-1-1.html 2016 Q&A Summary Thread (updates completed) http://bbs.hcbbs.com/thread-1597792-1-1.html
The flywheel ensures sufficient flywheel torque and a uniform tangential force; the energy stored during the rotation of the flywheel is used to cushion fluctuations in the rotation angle of the piston reciprocating compressor.
Since the working principle of a reciprocating compressor is to convert the motion of the crankshaft into reciprocating motion, the biggest drawback of such machines during rotation is uneven rotation, with dead zones present. This uneven rotation generates additional dynamic loads on the moving parts, increasing the load on the couplings and reducing their lifespan. It can also cause fluctuations in current levels in the motor and throughout the entire plant. A flywheel helps ensure sufficient flywheel torque and uniform tangential forces; the energy stored during the flywheel’s rotation is used to cushion the fluctuations in the rotation angle of the piston-type reciprocating compressor.
Reference answer: (1) The turntable device is driven to rotate through the meshing of gears. (2) During operation, the flywheel serves to convert, store, and release energy, without itself consuming any work. (3) It effectively balances the inertial forces of the crankshaft, resolves the imbalance between the driving torque and the resistive torque, and reduces vibrations in the compressor’s foundation. (4) It ensures a uniform rotation speed of the compressor, and reduces the amplitude of fluctuations in current and voltage in the motor and the power grid.
The flywheel has a large diameter and weight, which gives it high inertia; it is this inertia that helps to compensate for the changes in torque of the prime mover caused by variations in the pressure of the compressor piston. This allows the piston to move evenly, while keeping the torque of the prime mover constant. As the piston moves back and forth, its acceleration changes, which means that the inertial force acting on the piston also varies. Additionally, the pressure exerted by the gas on the piston is not uniform, resulting in constant changes in the load on the motor. The function of the flywheel is to balance this load on the motor.
Increasing inertial force is better than the dead point!
Its purpose is to compensate for the alternating load of reciprocating compressors. The volume and pressure in the compressor cylinder change over time, and these changes cause fluctuations in the load on the crankshaft, which are compensated for by the flywheel. The inertial force generated by rotation moves the connecting rod past the dead center.
Since the working principle of a reciprocating compressor is to convert the motion of the crankshaft into reciprocating motion, the biggest drawback of its rotation is uneven rotation. This uneven rotation generates additional dynamic loads on the moving parts, increasing the load on the couplings and reducing their lifespan. It can also cause fluctuations in current in the motor and throughout the entire plant. Therefore, a flywheel is used to ensure sufficient flywheel torque and a uniform tangential force; the energy stored during the rotation of the flywheel helps to cushion the fluctuations in the rotation angle of the piston-type reciprocating compressor. During the operation of the compressor, the crankshaft is subjected to a driving torque and a resisting torque; in one full rotation of the crankshaft, the work consumed by the resisting torque is equal to the work supplied by the driving mechanism. However, the resistance torque of the crankshaft is a torque that varies with the angle of rotation of the crankshaft, while the driving torque remains essentially constant. As a result, their instantaneous values during one rotation are often unbalanced, which causes the crankshaft to accelerate or decelerate. That is: Md – Mk = Jε. Here, Md and Mk represent the driving torque and the resisting torque respectively; J is the moment of inertia of all the rotating masses within the compressor unit; ε is the instantaneous angular acceleration of the compressor’s crankshaft – it is positive during acceleration and negative during deceleration. During operation of the compressor, it is not desirable for the angular velocity to experience large fluctuations. Therefore, during design, the moment of inertia J can be increased artificially by using flywheels, in order to reduce the instantaneous angular acceleration ε. If the mass of the rotating mechanism is artificially increased, that is, if its moment of inertia J is increased, then under the same torque difference, the angular acceleration ε of the shaft can be reduced, which helps to make the operation of the compressor more stable. A flywheel is a component with a large moment of inertia; installing a flywheel on the compressor’s shaft serves to stabilize the compressor’s rotation speed. < During the operation of a compressor, the flywheel plays a role in converting energy, storing it, and releasing it, without itself consuming any work. When Md > Mk, that is, when there is excess work available, both the flywheel and the rotor accelerate together; this excess work is converted into kinetic energy of the flywheel, which is stored within it to prevent further acceleration of the rotor ； When Md＜Mk, the loss of work causes the flywheel to slow down, and the flywheel then releases kinetic energy to compensate for the deficiency in driving power, thereby preventing further acceleration of the rotor. It is in this way that the flywheel regulates the angular velocity of the compressor during one rotation by storing and releasing energy (kinetic energy), thereby smoothing out the speed.
Flywheels are further divided into inertia wheels; these have a larger diameter and weight, which results in greater inertia when they rotate. It is this inertia that helps to compensate for the changes in torque of the prime mover caused by variations in the pressure of the compressor piston. This allows the piston to move evenly, while keeping the torque of the prime mover constant. As the piston moves back and forth, its acceleration changes continuously; as a result, the inertial force acting on the piston also changes. Meanwhile, the pressure of the gas acting on the piston is not uniform either. This leads to fluctuations in the load on the motor, and it is the function of the flywheel to balance this load.
A flywheel, also known as an inertial wheel, has a large diameter and weight; as a result, it possesses high inertia. It is this inertia that helps to compensate for the changes in torque of the prime mover caused by variations in the force exerted by the compressor piston. This enables the piston to move evenly while keeping the prime mover torque constant. As the piston moves back and forth, the magnitude of its acceleration changes, which in turn causes the inertial force acting on the piston to vary as well. Additionally, the pressure exerted by the gas on the piston is not uniform, leading to constant changes in the load on the motor. The function of the flywheel is to balance this load on the motor.