The research on the calculation of the filling process of the ship's air compressor is in the middle of the ship's 704th research institute Tian Tao Wang Rende Jiang Yuhua is an urgent problem to be solved. According to the characteristics of the ship's air compressor filling bottle, a simple calculation model is proposed. Through this model, the displacement of the ship's air compressor can be accurately calculated. 1 Introduction The ship air compressor is an important auxiliary machine for ships. It has certain requirements for the classification of high-pressure air compressors in ships around the world. The air in the ship is generally used after filling the bottle. The air compressor and the gas cylinder are directly connected through the pipeline. When the air compressor is used, the pressure in the cylinder will be directly fed back to the exhaust port of the air compressor, so that the air compressor is The pressure is rising. The displacement of the ship's air compressor is extremely sensitive to pressure, and the displacement of the air compressor varies with the change of the exhaust pressure. The determination of the rated displacement of air compressors in China is carried out according to GB T1548795 "Measurement method for flow rate of volumetric compressors", and the pressure is kept stable during the measurement. Therefore, the rated displacement measured according to the "Measurement Method of Volumetric Compressor Flow" does not reflect the filling displacement of the ship's air compressor, and it has a certain difference from the rated displacement. There are two cases in the actual use of the ship air compressor: (1) Initial filling, the pressure inside the cylinder rises from atmospheric pressure to the rated exhaust pressure (2) The middle air is filled with the bottle, and the pressure inside the cylinder is controlled by an intermediate pressure. Rise to the rated exhaust pressure. The literature [1, 2] uses a simple method to convert the measured nominal displacement into the filling displacement, but it ignores the effect of the compression factor, while in the case of high pressure, the compression factor is applied to the filling of the air compressor. The quantity has a great influence, so how to accurately calculate the bottle displacement of the ship air compressor under various working conditions is an important problem that needs to be solved urgently. 2 Filling process simulates the ship air compressor in actual use, the compressor outlet is directly connected to the cylinder inlet, so that the cylinder pressure rises from the pressure P to the rated discharge pressure, the required time and the temperature of each part are measured, and then according to the formula (1) The filling capacity of the air compressor at the pressure P can be determined. However, the temperature inside the cylinder is often difficult to accurately measure, so the displacement calculated according to equation (1) is an approximation. In the formula Q --- bottle displacement, L min --" cylinder volume, L --- suction temperature, K -- cylinder temperature, K according to the characteristics of the filling process, can assume that the air compressor is When the temperature is constant during the filling process, the filling process can be simplified into a simple model: the air compressor is filled with the bottle, the pressure of the cylinder causes the pressure to rise, the displacement of the air compressor changes, and the air compressor continues to fill the bottle until the gas The bottle pressure is up to the specified pressure. In the filling process, the working condition of the hollow press is constantly changing, and the pressure of the press increases with the increase of the filling time. The pressure increase of the air compressor from a certain discharge pressure to the rated discharge pressure is a continuous process, and the amount of gas per moment is difficult to determine, so we can statically process the filling process, that is, press under various pressures. GB T1548795 uses the nozzle method to measure the displacement of the air compressor, and then fits the displacement of the air compressor - the pressure discharge relationship. The expression is: y - air compressor displacement Because the nozzle displacement is the free state displacement, the volume of the free state gas filled into the cylinder within a certain period of time is: The atmospheric pressure volume in the gas cylinder increases as the gas charged into the gas cylinder increases, and the gas pressure in the gas cylinder increases. Since the filling process is simplified to an isothermal process, the instantaneous pressure in the cylinder is: ξ--the compression factor air can be treated as an ideal gas under low pressure, and the compression factor ξ is 1. Under high pressure, the air is compressed. The factor ξ has changed a lot and cannot be treated as an ideal gas. It is difficult to meet the fast and accurate requirements by using the method of checking the hand to calculate the compression factor. The RKS state equation (4) proposed by Soave to the RedlichKwong equation has the advantages of simple iteration and convenient application, which is very suitable for engineering calculation. The RKS state equation is: the form of the compression factor ξ is written as: the cubic equation of the RKS equation is actually the compression factor. The Newton iteration method can be used to solve the compression factor under various pressures and set appropriate precision control, which can be easily solved. Fitting the displacement-pressure curve of the air compressor itself, the relationship between the displacement of the air compressor and the pressure is obtained, and a small time increment is given. The increase of the gas volume is obtained according to formula (3). The compression factor is obtained from the RKS equation iteration, and the pressure is obtained by the equation (4). The displacement is obtained by the equation (2). By repeating the calculation, the actual filling process of the air compressor can be simulated. The calculation block diagram is shown in Figure 1. 3 Test results and analysis For a certain type of air compressor, the displacement of the air compressor under different pressures measured by the nozzle method for the two units is as shown in Table 1. According to the actual use characteristics of the ship, the air compressor is The outlet is directly connected to the gas cylinder, and several sets of filling experiments are carried out. According to formula (1), the test value of the filling displacement is compared with the calculated value of the model. The cylinder temperature is the average temperature of the upper, middle and lower temperatures of the cylinder. value. Unit 1, unit 2 air compressor discharge pressure - displacement test data unit 1 displacement (m unit 2 displacement (m through the least squares method to fit the displacement - pressure equation, the fitting results are shown in Figure 2, 3) The dot in the figure is the test value. The displacement of the unit 1 - the pressure displacement equation is: the correlation coefficient is 0.997338. The displacement of the unit 2 - the displacement equation is: the correlation coefficient is 0.972627. The standard state gas is fitted with the model, and the actual charge is filled to 20 MPa under different pressures. Bottle process. When the cylinder volume is 423L, the simulation results of unit 1 and unit 2 are compared with the test values ​​calculated according to equation (1). Comparison of calculated value of filled bottle volume and test value Filling process Unit 1 Filling capacity (L min) Unit 2 Filling volume (L min) Filling time (min) Cylinder temperature (°C) Test value calculated value Filling time (min) cylinder temperature (°C) test value calculation value Note: The suction temperature of unit 1 test is 14 °C, and the suction temperature of unit 2 is 15 °C. It can be seen from the test data and calculation results. The displacement of the sample from 0 to 20 MPa is about 18 L min, and the displacement measured by the nozzle method at 20 MPa is only 15.9 L min, which means that the capacity of the unit is larger than the rated displacement of the unit. the amount. It can be seen from Table 2 that the calculated values ​​of the model are basically consistent with the experimental values, which indicates that the calculation model can well simulate the actual filling process of the ship air compressor. However, as the pressure difference of the filling bottle decreases, the error between the calculated value and the experimental value increases from 1.1 to 0 to 20 MPa to 7.9 to 15 to 20 MPa. This is mainly because the filling time is short when the pressure difference is small during the test. Insufficient gas heat transfer in the gas cylinder brings a large temperature measurement error. For the test prototype, according to the unit displacement-discharge equation, the model calculates the displacement of the bottle when the unit is charged from 0 to a certain pressure. The comparison between the theoretical calculated value and the actual bottle filling value is shown in Fig. 4. The circle in the figure is the actual value of the unit, taken from the literature, and the black line is the theoretical calculation curve. It can be seen that the model calculation curve reflects the unit well. The performance of the filling bottle. 4 Conclusions (1) There is a big difference between the rated displacement of the air compressor and the displacement of the bottle. The volume of the bottle is greater than the rated displacement. This must be taken into account when designing and using the ship air compressor. According to the characteristics of the filling process of the ship air compressor, considering the influence of the compression factor of the air at high pressure, the calculation model proposed can accurately simulate the filling process of the ship air compressor and calculate the air compressor of the ship. Filling the bottle. 1 Li Qi. The displacement of the marine air compressor is measured. Fluid Engineering, 2 Li Qi. Research on the filling characteristics of marine air compressors. Fluid 3 Liu Rong and so on. Submarine assisted machinery. The Naval Engineering College published research and published many papers. Address: Room 2, 704, No. 10, Hengshan Road, Shanghai 200031. China leading manufacturers and suppliers of Roll Forming Machine Accessories, and we are specialize in Roll Forming Machine Parts,Hydraulic Roll Forming Machine Auto Decoiler, etc. Roll Forming Machine Accessories Roll Forming Machine Accessories,Roll Forming Machine Parts,Hydraulic Roll Forming Machine Auto Decoiler Xianfa Roll Forming Machine Factory , http://www.btxianfa.com