Exhaust emission of automotives using oil fuel is the main source of air pollution in cities. Promoting the replacement of gasoline and diesel with natural gas as the new fuel of automotives is the important way to effectively reduce the exhaust pollution of automotives. With the country's emphasis on clean energy and the enhancement of people's environmental protection consciousness, as the best alternative source the natural gas is gradually entering into every aspect of our daily life. It is most widely used in automotive industry. Mass flowmeter is one of the most important technological means of trade settlement in CNG industry. Study on high pressure gas flowmeter technology is the inevitable trend of our country to develop automotives with clean and environment-friendly natural gas.
An important standard deciding the quality of flowmeter performance is whether the design of vibration isolation system is reasonable. The main function of the vibration isolation system is to separate the vibration frequency of the measuring tube, and avoid the impact of external vibration on vibration of measuring tube. At present, the mass flowmeter on the market usually adopts the single vibration isolation system, which is a single vibration isolation block (as shown in FIG. 1). Some mass flowmeters use double vibration isolation system (as shown in FIG. 2). It means that two pieces of vibration isolation blocks with the same mass, size and shape are used to form the vibration isolation system.
Through the theoretical research and experiment, it is found that the two kinds of vibration isolation systems have different stress distribution. The stress area of the first vibration isolation form is mainly concentrated on the axis with the same direction of the vibration of measuring tube. The stress form is mainly normal stress (as shown in FIG. 3). The stress area of the second vibration isolation form is mainly concentrated on the axis perpendicular to the vibration of measuring tube. The stress form is mainly shear stress. It has asymmetric distribution (as shown in FIG. 4).
In fact, the stress area on these vibration isolation systems is the welding part of the measuring tube and vibration isolation block. Its strength is determined by the welding material and process. Therefore, whether it is normal stress or shear stress, as long as stress concentration is formed in the welding area, the defects in welding material and process will influence the vibration of the measuring tube.