Study On Internal Flow Characteristics In Aviation Fuel Cam Pump

With the rapid development of social economy,the construction speed of maritime industry and military surface ships has been accelerated,and the demand for port transportation and shipping of refined oil products has become more diversified,and the use of rubber-coated cam pumps for pumping and oil delivery under low liquid level conditions in oil tanks is proposed.In recent years,there has been great progress in the design and simulation of cam pump profiles at home and abroad,not only designing rotor profiles with larger displacement,but also predicting the flow pulsation and vibration noise by means of numerical simulation,and optimizing the internal structure of cam pumps based on this,so as to improve the overall performance of cam pumps.In this paper,based on the original rotor of the RDB5 cam pump,the rotor profile is mapped and modeled in three dimensions,and on this basis,an involute profile with the same outer diameter is derived.In order to study the internal flow mechanism of the rotor chamber of the cam pump,the internal flow characteristics of the cam pump when conveying finished fuel were calculated numerically based on Pumplinx,and the internal flow characteristics of the cam pump were predicted at different rotational speeds and outlet pressures;in addition,the flow characteristics and cavitation characteristics of the cam pump with different profiles at the different self-priming height were numerically simulated by introducing the cavitation model and reducing the absolute inlet pressure.In addition,numerical simulations were conducted to analyze the effect of self-priming height on the flow decay and internal cavitation distribution of the cam pump by introducing a cavitation model and reducing the absolute inlet pressure,and to obtain the outlet flow rate values under various operating conditions and to verify the accuracy of the numerical calculation results.This paper analyzes the internal flow characteristics of lobe pumps with different rotor lines and compares and selects the line with better flow characteristics and cavitation characteristics under low liquid level conditions to provide a theoretical basis for the application of lobe pumps in the field of aviation fuel transfer.The main conclusions of this paper are as follows:(1)The volume utilization coefficient of the original cycloidal line the average outlet flow rate are low,but it has high volumetric efficiency as well as flow pulsation stability,and its volumetric efficiency can reach 91.89%at rated working conditions;while the volume utilization coefficient of the involute line is 48.00%,which is 18.16%higher compared with the cycloidal line,which is consistent with its higher outlet flow rate in the numerical calculation results,but under different working conditions,its volumetric efficiency However,the volumetric efficiency is lower than that of the cycloidal rotor at different operating conditions,and the flow pulsation coefficient is higher.The difference between the two profiles in terms of radial force on the rotor is not significant,but mainly in the radial force component in the x-direction,with the involute rotor having an additional radial force pulsation,which causes an increase in shaft vibration.The overall internal flow rate of the involute rotor cavity is higher than that of the cycloidal rotor,but the leakage at its rotor engagement is also higher,resulting in a higher outlet flow rate but slightly lower volumetric efficiency.(2)The self-priming performance test of the cam pump was conducted to verify the performance of the cam pump under sweeping conditions,and the test results proved that it can be used in sweeping conditions.Through the numerical calculation of the cam pump,it was found that the volumetric efficiency of the involute rotor declined less than that of the cycloidal rotor at a self-priming height of 5m,only by2.606%,and the degree of cavitation in the rotor cavity was also lower,with an average gas volume fraction of 1.623%,which was lower than that of the cycloidal rotor at1.733%;with the increase of the self-priming height,the volumetric efficiency of both types of rotors decreased continuously,but the volumetric efficiency of the involute rotor decreased faster than that of the cycloidal rotor.Compared with 1m self-priming height,the volumetric efficiency of 6m self-priming height only decreases by 1.904%,which is less than 2.343%of the cycloid rotor;comprehensive analysis shows that the involute line can reduce the volume fraction of free gas in the chambers on both sides of the pump and reduce the influence of cavitation on the flow characteristics.(3)Based on the cost consideration of producing a new type of linear rotor cam pump,a 4-lobe involute profile with the same center distance as the cycloid profile is proposed,in which the newly machined rotor can be directly installed in the pump chamber of the prototype pump,reducing the design and machining costs of the remaining parts of the cam pump.Although the outlet flow rate is only increased by0.011 m~3/h,the intensity of flow pulsation and pressure pulsation is suppressed;the 4-lobe involute rotor has an average gas volume fraction similar to that of the 3-lobe involute rotor,which indicates that it still has the advantage of suppressing cavitation inside the pump chamber;in a comprehensive analysis,the 4-lobe involute rotor can be used to replace the cycloidal rotor in the prototype pump to improve its output flow stability and cavitation performance.This paper is based on the optimization of a variety of oil transfer conditions.This paper aims to optimize the performance of the cam pump under various oil delivery conditions,and provides theoretical guidance for the selection of the cam pump profile for fuel delivery by establishing different rotor profiles and analyzing their effects on the performance of the cam pump under multiple operating conditions.