Solving the problem of subsynchronous vibration of back-to-back compressor

High-pressure turbopumps and high-pressure compressors solve the sub-asynchronous vibration problem with a honeycomb seal. The turbine seal application of the honeycomb can improve the efficiency of the stage. After the honeycomb seal is used in the aircraft ship engine, the fuel consumption is reduced and the stability of the rotor is improved. Establish a real physical model of the honeycomb seal, combine experimental research, solve the average equation, reveal the mechanism of the honeycomb seal, and form the design method of the honeycomb seal. The vibration efficiency of the impeller mechanical honeycomb seal, with the development of modern impeller machinery towards the high parameter direction, the fluid induced vibration in the comb seal can cause the rotor to be unstable. Compared with comb seals, honeycomb seals not only have better sealing characteristics, but also better rotor dynamics.

The liquid oxygen turbine pump in the US space shuttle uses a honeycomb seal to eliminate the subsynchronous vibration of the turbine used in the nuclear power unit. The honeycomb seal is applied in the final stage and the secondary, and the high-efficiency centrifugal pressure is improved. Sealing solves the problem of sub-asynchronous vibration. After applying the honeycomb seal to the technical modification of China's military civil aircraft engine, it not only increases the thrust, reduces the fuel consumption, but also reduces the vibration.

At present, honeycomb sealing has been widely used in spacecraft high-power rocket military and civil aircraft and a variety of ship engines, as well as steam turbine compressors in the power petrochemical industry, in reducing leakage, improving efficiency and eliminating low-frequency vibration of the rotor. In terms of aspects, it played an important role. Honeycomb sealing rings are generally used as stators. The rotors usually have comb teeth, and some are smooth cylindrical surfaces. See the honeycomb seal. The application of the honeycomb seal in a centrifugal compressor. When the pressure difference between the two ends of the seal is high, the comb is combed. The strength of the tooth seal is unbearable. For this purpose, some high pressure compressors use a honeycomb seal.

In the 1920s, a large number of honeycomb seals were used, mainly by using their better damping characteristics to suppress the subsynchronous vibration of high-pressure centrifugal compressors. Tests and field operations have proven that honeycomb seals with jets can better address the problem of subsynchronous vibration of high pressure compressors. The centrifugal compressor adds radial jet flow in the inter-segment comb seal, which solves the problem of sub-synchronous vibration of this back-to-back compressor. In the same year, three back-to-back centrifugal compressors with a discharge pressure were used, and the interstage seal was a honeycomb seal with a jet flow, and a damper bearing was applied.

In the full load experiment, no obvious subsynchronous vibration was found, and the vibration of the first-order natural frequency was also well damped. The honeycomb seal can also be used as a balance disc seal with the largest differential pressure of a straight-through centrifugal compressor. The honeycomb seal of the balance plate of a natural gas compressor has a comb tooth on the rotating member (balance plate), which is a three-stage step structure, and the stator is a honeycomb seal. The application of honeycomb sealing in steam turbines to improve the efficiency of steam turbines is one of the hotspots pursued by the world's major steam turbine companies.

There is often no steam block on the top of the turbine, and the leakage loss is very large. The application of the honeycomb steam seal can greatly reduce the tip clearance, reduce leakage, prevent the wear of the bucket blades, improve the efficiency of the stage, and improve the stability of the rotor operation. For a steam turbine used in a nuclear power plant, a honeycomb seal is applied to the final stage and the final stage of the low pressure cylinder. The honeycomb steam seal base has a circumferentially passing comb sink.

There is no steam block at the top of the final stage and the last stage. The tip radius gap is about after the application of the honeycomb steam seal. The tip radius clearance is reduced to about a large amount of leakage. Especially in the final stage, the rotor has a comb. The teeth can be embedded in the honeycomb stator, and the sealing effect is better. Honeycomb Seals for Aero Engines In the United States, honeycomb seals are used extensively in engines ranging from one to one and sixteen passenger aircraft.

At the beginning of the 1900s, domestic aircraft engines were technically modified. One of the measures was to replace the comb seal with a honeycomb seal to reduce the seal gap, reduce leakage and improve efficiency. After the transformation, the engine power is unchanged, the fuel consumption is reduced. The honeycomb seal is used in the marine gas turbine. The gas turbine on a certain type of destroyer is used as a power turbine bearing seal device.

A gas turbine uses a large number of honeycomb seals in high-pressure compressor high-pressure turbine low-pressure turbines and power turbines to improve unit efficiency and ensure operational stability. Application of Honeycomb Seals in High Pressure Turbo Pumps The US Space Shuttle main engine is a high power rocket engine fueled by liquid oxygen and liquid hydrogen. A high-pressure turbo pump that supplies liquid oxygen and hydrogen to the fuel chamber. The boosting amplitude is a sub-asynchronous vibration caused by the inter-stage comb-tooth seal during the development of the high-pressure turbo pump, which reduces the life of the turbo pump rolling bearing. This interstage comb has a tooth with a tooth on the rotor and no swirl gate. At the beginning of the transformation, only the inner wall surface of the smooth casing was changed into a honeycomb seal. As a result, the vibration amplitude decreased significantly, but the subsynchronous vibration did not completely disappear. To this end, the honeycomb seal is equipped with a swirling shutter to completely eliminate the sub-asynchronous vibration.

Experimental Study of Honeycomb Seals Honeycomb seals are used in many fields of impeller machinery. However, until now, it is not clear how the structure size of several honeycomb seals affects its performance, and the sealing characteristics and damping mechanism of the honeycomb seal have not yet been recognized. In engineering practice, there is a lack of systematic design guidelines and generally rely on experience. The purpose of the experimental study is to explore the influence of the structural size of the honeycomb seal on its leakage characteristics and dynamic characteristics.

The cross-rigidity of the honeycomb seals all have positive values ​​corresponding to different honeycomb sizes, and the cross-stiffness has no obvious change rule. The cross stiffness is small or negative, which is beneficial to the stable operation of the rotor. The main stiffness of the seven honeycomb seals is positive and negative, and there is no obvious correspondence with the honeycomb size. The main stiffness of the gas seal does not directly affect the stability of the rotor. If the main stiffness is large, the critical speed of the rotor can be increased. The eddy frequency ratio is an index that comprehensively evaluates the sealing dynamic characteristics. The smaller the value, the more favorable the rotor stability.

When the pre-spinning of the fluid population coincides with the direction of rotation of the rotor, the eddy frequency ratio of the honeycomb seal is minimal, followed by the comb seal and the smooth seal. From the perspective of energy dissipation, the vibration damping mechanism of the honeycomb seal was experimentally studied. This indicates that the gas pulsation in the seal is composed of a large eddy motion, and the gas pulsation energy is high. The stator is a sealed cavity with comb teeth on the honeycomb sealed rotor. The power spectrum of the gas pulsation is multi-peak spectrum with small peaks. This shows that the gas pulsation in the honeycomb seal is composed of many different vortex motions, the energy is fully dissipated, and the viscous damping is large, which helps to suppress the vibration of the rotor. Theoretical Analysis of Honeycomb Seals When theoretically analyzing honeycomb seals, conventional volumetric flow methods (such as single control body methods) are commonly used to simplify the continuous equation momentum equations and energy equations describing fluid motion in seals into volumetric control equations.

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