Research On Fluid Characteristic Within The Rotating-wing Machinery Based On Fluid Structure Interaction Model

With the reform of charge system of heating supply,the heat meter is used widely in China.Most heat meter use rotating-wing flux meter to measure flux. Compared with the foreign products,the technological level of the domestic heat meter is still quite low and can't measure flux accurately.In order to improve the measurement accuracy of heat meter,the flow characteristic of heat meter must be researched.Using Computational Fluid Dynamics to carry out numerical calculation is the main method of researching the flow characteristic.Compared with other rotating machinery,heat meter have own specialty:first,the water temperature scope of heat meter is 5-95℃,the heat meter should measure flux accurately while water temperature changes obviously.Secondly,the inner parts of heat meter are made by plastic material,the stiffness and strength of plastic material can decrease with the rising of temperature.The elastic deformation of inner structure can obviously influence the flow characteristic and performance of heat meter while flux and temperature reach the maximum.Thirdly,the impeller rotate speed is determined by flow and must be calculated by numerical calculation.According to flow characteristic of heat meter,the fluid structure interaction(FSI) model must be used while numerical calculation is carded out.The research uses FSI model to carry out numerical calculation.The ALE (arbitrary Lagrange -Euler) method is used to deal with the interface between the fluid and structure domain.FSI model is used to calculate the elastic deformation of structure and research how elastic deformation influences the flow characteristic of heat meter.The results of numerical calculation can be proved by experimental results, using non-magnetic method to measure the flux signal in special experimental instrument for heat meter and calculate the meter coefficient K.This paper designs a new type two flow-channel flow meter,a triangle deflector is located at the inlet,and it changes the direction of flow and divides the water flow into two parts.The water flows into the impeller cell and pushes the impeller to rotate. The impeller cell and deflector are made by MPPO material.Experimental results show meter coefficient K increase with the increasing of water flux,when water temperature is 80℃,the meter coefficient K increase more quickly than water temperature is 25℃with the increasing of water flux.The numerical calculation that elastic deformation is not considered is used to research the performance of two flow-channel flow meter,the calculated results show the meter coefficient K don't change when temperature and flux increase.The difference between calculated results and experimental results show the numerical model that elastic deformation is not considered can not reflect the real situation.According to the structure characteristic of two flow-channel flux meter,the deflector is weak and maybe be deformed obviously and influence the measure performance with the increasing the temperature and flow flux.So the FSI model that elastic deformation is considered is used to carry out numerical calculation to analyze the effect of elastic deformation of deflector on measure performance of heat meter.The calculation results of FSI model show the deflector deforms obviously as the water temperature and flux increase,the maximum horizontal deformation can reach 0.948mm while temperature is 80℃and flux is 5m~3/h.The deformation of deflector changes the flow characteristic and causes the meter coefficient K increases while flux increases.The stiffness of MPPO decreases while temperature rises,so the deformation of deflector is more obviously and the meter coefficient K increases more quickly when temperature rises.The results of experiments can prove the calculation results are valid and show the elastic deformation of deflector influence the performance of measure.In order to reduce the deformation of deflector,the thickness of deflector is increased and using PPS instead of MPPO produces impeller cell and deflector.The experiment and calculation results prove new structure and material of deflector improve the stiffness and the meter coefficient K don't change when flux and temperature changes.Based on the improved structure and material of deflector,the effects of structure element on performance of heat meter are researched.The experiment and calculation results show the length of straight tube located at the meter inlet should be 10 times as long as tube diameter for guarantee the measure accuracy when no screen is located at the inlet.While 3×3mm screen is located at the meter inlet,only 4D(D is the diameter of inlet) straight tube can guarantee the measure accuracy of heat meter.The researches also show the adjusting rib located at the top of impeller cell can adjust meter K;the optimal number of blade should be 6 or 7;the rib located at the bottom of impeller cell can stabilities the rotate speed of impeller.The pressure loss of two flow-channel heat meter is also researched,the pressure loss is 22.26kPa when screen is located at the inlet and flux is 2.5m~3/h.The pressure loss of two flow-channel meter can meet the requirement of heat meter standard.The paper design a multi-channel flow meter,the water flow is deflected 90°to enter impeller cell and push the impeller to rotate.Experiments show meter coefficient K increases while water temperature rises.The FSI model is used to research the flow characteristic of multi-channel flow meter,calculated results show thermo-expansion is main factor of influencing measure performance of multi-channel flow meter.Acceding to the calculated results,meter coefficient K must be revised while water temperature changes.Numerical and experimental method is used to research the flow characteristic and measure performance of multi-channel flow meter.The researches show the influence of swirl in inlet can be eliminated and measure accuracy can be guaranteed when the length of straight tube located an inlet is 4 times as long as tube diameter. Numerical and experimental researches prove the pressure loss of multi-channel reaches 28.2kPa,exceed 25kPa-the value required by heat meter standard.In order to reduce pressure loss,4 schemes are designed and researched by numerical calculation. Numerical calculation show drill a 2×8mm rectangle hole at the backside that can not be impacted by inlet flow is the best way to reduce pressure loss.The experimental results prove the calculation results are correct.The paper uses FSI model calculate the elastic deformation caused by thermo-expansion and water flow impact,analyses the effect of elastic deformation of structure on flow characteristic and measure performance.The model and calculation method used in this paper can provide reference for similar problem.This paper also researches the flow characteristic of rotating-wing heat meter,analyzes the key factor influence measure performance,and determines the install condition of heat meter. The results of this paper can direct the design and reduce development cost of heat meter.