| Existing oil-gas multiphase pump expose the problem of low efficiency, poor reliability, without internal compression function, difficult to adapt to high gas content and high compression ratio condition, in order to solve these problems and meet the urgent need of torch elimination and natural gas recovery, a new type of reciprocating oil-gas multiphase pump is proposed. Given the related research of reciprocating oil-gas multiphase pump is still in starting stage, the working mechanism of its import and export check valve is not clear. This paper does some theoretical and numerical simulation research about flow field and lagging angle of combined valve, input power of the pump. At last, the operating characteristic of combined valve under gas-liquid two-phase condition is presented. The main studies are as follows.1. According to the structure of the combined valve, a simplified3-D geometry model of the flow field is established. The steady-state numerical simulation of internal flow field under different maximum open heights and gas-liquid ratio is done using software Fluent. This simulation get the valve gap flow velocity﹑pressure drop and discharge coefficient under the joint action of maximum open height and gas-liquid ratio.2. A simplified2-D axis-symmetry geometry model of the flow field is established, the unsteady opening-closing process of combined valve under different gas-liquid ratio is simulated. The simulation is based on standard k-ε turbulent model, dynamic mesh technology and User Defined Function. The relationship between pressure distribution on valve core, valve gap flow velocity, transient flow force, valve core total force and gas-liquid ratio, valve open height during opening-closing process of valve are obtained.3. The theoretical formula of lagging angle for reciprocating oil-gas multiphase pump combined valve is established, and the mathematical calculation method and step of lagging angle for this valve is achieved. Through the calculation and analysis of example, the variation characteristics of lagging angle for combined valve under different suction pressure, discharge pressure and gas-liquid ratio are obtained. The multiphase Mixture model and dynamic mesh technology are employed, and the numerical simulation of internal compression process for gas-liquid mixture is done. Compared the results of theoretical calculation and numerical simulation, the theoretical formula of lagging angle is confirmed. The study results can provide reference for lagging angle design of combined valve.4. Through analysis of working principle for reciprocating oil-gas multiphase pump, combined with the balance equation of opening pressure for combination valve and adiabatic internal compression process for gas-liquid mixture, the calculation formula of input power is deduced. Using an actual design example, the variation of input power for three-cylinder double-acting reciprocating oil-gas multiphase pump under different suction pressure, discharge pressure and gas-liquid ratio is summarized. |
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