Study On Characteristic Of Transporting Fruits And Vegetables By Annular Jet Pumps

With the development of the fruits and vegetables industry,the traditional mechanical transportation can not meet the requirements.As a kind of hydraulic transportation machinery,annular jet pump combine the transportation and cleaning.For now,the study of using annular jet pump to transport fruits and vegetables has not been reported,this article based on the test,high-speed video technology and MPM numerical simulatio to study the transportation capacity,damage and interaction with pump in the process of transportation.The main work and achievements include:(1)The efficiency,pressure ratio,water power and pressure change of annular jet pump under different structural parameters and hydraulic parameters is studied experimentally.With the increase of primary flow rate,the flow ratio,water power and efficiency increase,the pressure ratio decreases.Cavitation will occur when primary flow rate is large enough,then flow ratio,efficiency and pressure ratio decrease with the increase of it.The annular jet pump has large axial pressure gradient.(2)The transporting capacity under different structural and hydraulic parameters is studied experimentally.With the increase of primary flow rate,the transporting capacity and energy consumption per unit mass increased.Under the same water power,the annular jet pump with larger area ratio has larger transporting capacity.The transporting capacity decreases with the increase of conveying height,and the energy consumption per unit mass increases accordingly.The annular jet pump has the largest transporting capacity for potatoes and the lowest energy consumption per unit mass.The damage of fruits and vegetables in the process of transportation includes mass loss and surface damage.The main factors affecting the damage are speed and swing degree of fruits and vegetables,so the damage increases with the increase of primary flow rate.(3)The motion of fruits and vegetables in the pump is studied using high-speed video technology and numerical simulation.Fruits and vegetables will accrlerate when enter the annular jet pump,but when primary flow rate is small,fruits and vegetables will experience a brief deceleration process because the backflow phenomenon in suction chamber.Then fruits and vegetables enter the diffusion tube,the velocity of the fruits and vegetables decrease.The shape of potatoes,cherry tomatoes and kumquats are same,so their motion process in the pump is basically the same,while the acceleration of carrot in the pump is small due to its elongated shape,so its maximum speed in the pump is far less than others.The fruits and vegetables not only have translation movement,the carrots will swing while the ellipsoid fruits and vegetables will rotate because the strong shear flow in the annular jet pump,especially in the throat.(4)The external characteristic change of annular jet pump when frutis and vegetables transporting is studied experimentally.Among the four fruits and vegetables,potatoes has the greatest effect on flow rate,and kumquat has the weakest effect.With the primary flow rate increase,the effect on the flow rate increase.When the primary flow rate is 60 m~3/h,the wall pressure will drop first and then rise when the potatoes passing the pump;When the primary flow rate is80 m~3/h,the cavitation will cause two pressure drops.When the primary flow rate is 90 m~3/h,the wall pressure will drop for some time when potatoes passing pump due to the cavitation induced by it.When the primary flow rate is 100 m~3/h,the wall pressure in the throat will rise due to the passing of the potatoes,and the wall pressure in the diffusion tube will first rise,then fall and then rise.The pressure change caused by carrots is similar to potatoes at low flow rate but smaller.When the primary flow rate is 80 m~3/h,cavitation occurs in the middle of the carrots and only cause one pressure drop.When the primary flow rate is 100 m~3/h,carrots will promote cavitation and cause the decrease of downstream wall pressure,then carrots will prevent cavitation from spreading downsteam,so downsteam wall pressure will rise for a while.(5)The influence on the internal flow of annular jet pump cause by frutis and vegetables movements is studied using numerical simulation.Due to the blockage and acceleration and deceleration process of the fruits and vegetables,the inside velocity and pressure distribution of the annular jet pump is no longer symmetrical.The velocity and pressure distribution is different when fruits and vegetables move to the different position.Since the movement of fruits and vegetables mainly affects the primary flow in the throat,it has less influence on the internal flow of the annular jet pump with a larger area ratio and a smaller primary flow rate.