The goal of this study is to develop an airflow meter sensor for vehicle intake system detection in internal combustion engines. The study uses micro-electromechanical process technology to develop a hot-film flow met...The goal of this study is to develop an airflow meter sensor for vehicle intake system detection in internal combustion engines. The study uses micro-electromechanical process technology to develop a hot-film flow meter with an alumina substrate and platinum film heater;the hotline method is used to create a micro airflow anemometry meter sensor relying on variations in resistance of the platinum film corresponding to different wind velocity at the set temperatures. The micro-sensor is less bulky and simpler structure than ordinary meters, and its small size enables it to provide good sensitivity and measurement precision. The alumina plate used in this study is produced by polishing an alumina substrate, a platinum film is then deposited on the plate to complete the micro-heater used in the sensor. Resistance on the sensor side varies as gas flows through the sensor, and the instrument determines airflow velocity on the basis of the changes in resistance caused by gas flow differences. Airflow velocity form 10 m/s to 60 m/s are used to test. Resistance displays a regular slope, indicating the relationship between airflow velocities varies remain predictable throughout the sensing range. Therefore, the sensor can achieve its airflow measurement purpose completely.展开更多
Background Turbulent shear stress （TSS） plays an important role in the research of fluid dynamics of heart valves. This study aimed to perform a quantitative study of TSS downstream of porcine artificial mitral valv...Background Turbulent shear stress （TSS） plays an important role in the research of fluid dynamics of heart valves. This study aimed to perform a quantitative study of TSS downstream of porcine artificial mitral valves in order to verify the correlation of hot-film anemometry （HFA） and Doppler echocardiography combined with computer-aided image analysis for the detection of TSS. Methods A porcine model of mitral valve replacement was established. HFA and Doppler ultrasound techniques were used to directly and indirectly measure TSS-relevant parameters of the artificial mitral valve following different mitral valve replacements： different approaches were used to reserve the subvalvular apparatus of the mitral valve. A correlation analysis was then carried out. Results There was a significant correlation between the HFA and Doppler ultrasound combined with computer-aided image analysis of the TSS at the same time and at the same site. No significant difference was found in the TSS measured by the two methods. Conclusions Compared with HFA, Doppler echocardiography combined with computer-aided image analysis is a safe, non-invasive, and real-time method that enables accurate and quantitative detection of TSS downstream in vivo, objectively reflecting the flow field downstream of the artificial mitral valve. Doppler ultrasound combined with computer- aided image analysis can be employed for quantitatively evaluating the downstream hemodynamic performance of the mitral valve.展开更多
In this letter we present a novel wall shear stress measurement technique for a turbulent boundary layer using sandwiched hot-film sensors. Under certain conditions, satisfactory results can be obtained using only the...In this letter we present a novel wall shear stress measurement technique for a turbulent boundary layer using sandwiched hot-film sensors. Under certain conditions, satisfactory results can be obtained using only the heat generated by one of the hot-film and a calibration of the sensors is not required. Two thin Nickel films with the same size were used in this study, separated by an electrical insulating layer. The upper film served as a sensor and the bottom one served as a guard heater. The two Nickel films were operated at a same temperature, so that the Joule heat flux generated by the sensor film transferred to the air with a minimum loss or gain depending on the uncertainties in the film temperature measurements. Analytical solution of the shear stress based on the aforementioned heat flux was obtained. The preliminary results were promising and the estimated wall shear stresses agreed reasonablywell with the directly measured values （with errors less than 20%） in a fully developed turbulent pipe flow. The proposed technique can be improved to further increase precisions.展开更多
Prevention and control measures of spontaneous combustion of coal and gas accumulation in a goaf require an accurate description of its gas flow state.However,the commonly used fluid dynamics in porous media is not su...Prevention and control measures of spontaneous combustion of coal and gas accumulation in a goaf require an accurate description of its gas flow state.However,the commonly used fluid dynamics in porous media is not suitable for the new-born goaf with fracture cavity combination,multi-scale,and large blocks.In this study,we propose a cavity flow algorithm to accurately describe the gas flow state in the new-born goaf.The genetic algorithm(GA)is used to randomly generate the binary matrix of a goaf caving shape.The difference between the gas flow state calculated by the lattice Boltzmann method(LBM)and the measured data at the boundary or internal measuring points of the real goaf is taken as the GA fitness value,and the real goaf caving shape and the gas flow state are quickly addressed by GA.The experimental model of new-born goaf is established,and the laser Doppler anemometry(LDA)experiment is carried out.The results show that the Jaccard similarity coefficient between the reconstructed caving shape and the real caving shape is 0.7473,the mean square error between the calculated wind speed and the LDA-measured value is 0.0244,and the R2 coefficient is 0.8986,which verify the feasibility of the algorithm.展开更多
文摘The goal of this study is to develop an airflow meter sensor for vehicle intake system detection in internal combustion engines. The study uses micro-electromechanical process technology to develop a hot-film flow meter with an alumina substrate and platinum film heater;the hotline method is used to create a micro airflow anemometry meter sensor relying on variations in resistance of the platinum film corresponding to different wind velocity at the set temperatures. The micro-sensor is less bulky and simpler structure than ordinary meters, and its small size enables it to provide good sensitivity and measurement precision. The alumina plate used in this study is produced by polishing an alumina substrate, a platinum film is then deposited on the plate to complete the micro-heater used in the sensor. Resistance on the sensor side varies as gas flows through the sensor, and the instrument determines airflow velocity on the basis of the changes in resistance caused by gas flow differences. Airflow velocity form 10 m/s to 60 m/s are used to test. Resistance displays a regular slope, indicating the relationship between airflow velocities varies remain predictable throughout the sensing range. Therefore, the sensor can achieve its airflow measurement purpose completely.
基金This study was supported by grants from the National Natural Science Foundation of China （No. 30860297） and the United Specialized Foundation of Science and Technology Agency of Yunnan Province and Kunming Medical University （No. 2011FB 185）.
文摘Background Turbulent shear stress （TSS） plays an important role in the research of fluid dynamics of heart valves. This study aimed to perform a quantitative study of TSS downstream of porcine artificial mitral valves in order to verify the correlation of hot-film anemometry （HFA） and Doppler echocardiography combined with computer-aided image analysis for the detection of TSS. Methods A porcine model of mitral valve replacement was established. HFA and Doppler ultrasound techniques were used to directly and indirectly measure TSS-relevant parameters of the artificial mitral valve following different mitral valve replacements： different approaches were used to reserve the subvalvular apparatus of the mitral valve. A correlation analysis was then carried out. Results There was a significant correlation between the HFA and Doppler ultrasound combined with computer-aided image analysis of the TSS at the same time and at the same site. No significant difference was found in the TSS measured by the two methods. Conclusions Compared with HFA, Doppler echocardiography combined with computer-aided image analysis is a safe, non-invasive, and real-time method that enables accurate and quantitative detection of TSS downstream in vivo, objectively reflecting the flow field downstream of the artificial mitral valve. Doppler ultrasound combined with computer- aided image analysis can be employed for quantitatively evaluating the downstream hemodynamic performance of the mitral valve.
基金funded by the National Natural Science Foundation of China (11572078 and 91752101)973 Plan (2014CB744100)
文摘In this letter we present a novel wall shear stress measurement technique for a turbulent boundary layer using sandwiched hot-film sensors. Under certain conditions, satisfactory results can be obtained using only the heat generated by one of the hot-film and a calibration of the sensors is not required. Two thin Nickel films with the same size were used in this study, separated by an electrical insulating layer. The upper film served as a sensor and the bottom one served as a guard heater. The two Nickel films were operated at a same temperature, so that the Joule heat flux generated by the sensor film transferred to the air with a minimum loss or gain depending on the uncertainties in the film temperature measurements. Analytical solution of the shear stress based on the aforementioned heat flux was obtained. The preliminary results were promising and the estimated wall shear stresses agreed reasonablywell with the directly measured values （with errors less than 20%） in a fully developed turbulent pipe flow. The proposed technique can be improved to further increase precisions.
基金This work was supported by the Natural Science Foundation of China(Nos.51774169 and 51574142)the National Key Research and Development Program of China(No.2017YFC0804401).
文摘Prevention and control measures of spontaneous combustion of coal and gas accumulation in a goaf require an accurate description of its gas flow state.However,the commonly used fluid dynamics in porous media is not suitable for the new-born goaf with fracture cavity combination,multi-scale,and large blocks.In this study,we propose a cavity flow algorithm to accurately describe the gas flow state in the new-born goaf.The genetic algorithm(GA)is used to randomly generate the binary matrix of a goaf caving shape.The difference between the gas flow state calculated by the lattice Boltzmann method(LBM)and the measured data at the boundary or internal measuring points of the real goaf is taken as the GA fitness value,and the real goaf caving shape and the gas flow state are quickly addressed by GA.The experimental model of new-born goaf is established,and the laser Doppler anemometry(LDA)experiment is carried out.The results show that the Jaccard similarity coefficient between the reconstructed caving shape and the real caving shape is 0.7473,the mean square error between the calculated wind speed and the LDA-measured value is 0.0244,and the R2 coefficient is 0.8986,which verify the feasibility of the algorithm.
