With the development of economy, over the past few years, major engine companies and internal combustion engine research institutes have successively built engine test rooms in order to develop and improve the performance and quality of various aspects of the engine.
However, due to the large disturbance and vibration generated when the engine is tested on the test bench, the control of vibration and noise is particularly important. The routine test of an engine before leaving the factory is generally about 1-2 hours, and the durability test of the engine usually takes 3000 hours or even longer continuous tests. The continuous vibration and noise generated by the engine at this time is greater. If vibration isolation measures are not taken, it will have adverse effects on the normal use of surrounding precision instruments and instruments, working environment, and construction facilities. Therefore, vibration isolation measures must be taken. Vibration is eliminated, noise is reduced, the environment is protected, and the environment is beautified. It also provides a comfortable workplace for staff.
In vibration control, vibration isolation is a small investment, but it is a very effective approach, especially when the space is limited or the land is very expensive or the process requires, the distance between the vibration source and the vibration object cannot be increased. More shows the superiority of vibration isolation measures. The traditional vibration reduction measures are in the form of vibration isolation trenches. For shock vibrations or vibrations with frequencies greater than 30 Hz, vibration isolation trenches have a certain vibration isolation effect. For low-frequency vibrations, they have little effect and even have little effect. Nowadays, the most effective measure is to install shock absorbers under the test bench and use elastic foundations to isolate the vibration. The isolator must have low natural frequency, good vibration isolation effect, large damping ratio, stable performance, easy installation, and use. Long life and other advantages.
Vibration isolation of the test bench must be taken into consideration when the engine speed changes greatly and the interference frequency range is large. For example, the lower engine speed is 500rpm. At this time the interference frequency f = 8.33Hz, and compared to the speed of 3000rpm, at this time the interference frequency f = 5Hz, the choice of shock absorbers need to consider the vibration isolation effect of low frequency and high frequency. Therefore, a low-frequency damping Spring shock absorber is used, and the natural frequency (f0) of the shock absorber should be below 3 Hz to ensure good vibration isolation efficiency. Taking the natural frequency of the isolator as 2.5Hz as an example, when the engine speed frequency f is equal to the natural frequency f0 of the isolator, that is, f/f0=1, it is a resonance point, and the engine speed is 150 rpm; when the engine speed is 106 -Resonance zone at -212rpm; No vibration isolation effect when the engine speed is below 106rpm; Better isolation of engine speed above 375rpm, up to 80%; Above 792rpm vibration isolation efficiency up to 96%, solid sound transmission is also basic Sparing, the effect is very good. The damping ratio of the vibration isolator should be ≥ 0.065. When the engine rotates at a high speed, the interference frequency is high, which can suppress the vibration caused by the vibration isolator when the high-frequency impact occurs. At the same time, the engine starts and shuts down rapidly when passing through the resonance area. After installation of the shock absorber between the test stand and the foundation, consideration shall also be given to the installation of rubber flexible hoses or metal hoses for the water pipes, oil pipes (its rigidity should be less than that of the isolator) in order to prevent vibration transmission. The same measures are taken for real equipment such as wind turbines and water pumps in the laboratory. Pipes pass through the wall and pass through. The pipes and walls shall be separated and elastic materials shall be used to prevent vibration from transmitting through the wall. A certain distance to set up the vibration isolation hanger and vibration isolation bearings.
Laboratory doors and windows need to use double sound insulation devices, and sound-absorbing materials are installed on the top of the wall to reduce indoor noise and control noise pollution to the surrounding environment. After using a vibration isolator between the test bench and the foundation, the bench amplitude and acceleration of the test bench shall also be considered. Generally, the amplitude of the test bench is controlled to be less than 0.05mm. The amplitude of the mesa, the weight of the mass, and the mass are usually calculated using concrete slabs or T-blocks. The T-block can lower the center of gravity and improve the horizontal stiffness.
Wujiang Jinnuo Shock Absorber Factory Design Department has cooperated with relevant design institutes for several years to design vibration isolation and noise reduction projects for engine test rooms, such as Changzhou Diesel Generator Co., Ltd., Dalian Diesel Engine Co., Ltd., and Tianjin Diesel Engine Co., Ltd. Engine Test Benches. The vibration isolation, and the use of the "Jinnuo" brand ZT low frequency damping spring isolator manufactured by Wujiang Jinnuo Shock Absorber Factory, due to the low natural frequency of the above isolator, the better load is about 2.3Hz, the damping ratio Larger, has achieved good results in the vibration isolation project.
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