Certain feasibilities and features were discussed in typhoon detection by radar with a negative elevation angle according to the relationship between the remote detecting range and the elevation angle of the new gener...Certain feasibilities and features were discussed in typhoon detection by radar with a negative elevation angle according to the relationship between the remote detecting range and the elevation angle of the new generation weather radar, in order to rectify the disadvantages of detecting capability for remote low-level echo with a lowest elevation angle of 0.5° in the common detecting mode. The data obtained from detecting the typhoon of Haitang and Changmi with radar for their negative elevation angles and the observed data for the common lowest elevation angle of 0.5° were compared to each other. The results showed that the detection of remote low level cloud system with radar could be improved by using the negative elevation angle, and the structure and the evolution trend of a typhoon could be better judged. The increasing degree of detection for negative elevation angles in the current volume scanning mode should be helpful for predicting the intensity and developing trend of windstorms, to further improve the capability of warning and nowcasting. The detection of negative elevation angle could also help reveal the development and change of typhoon＇s low level cloud system. As far as the typhoons of Haitang and Changmi were concerned, the detecting area of Changmi was increased by 1.09 times with the negative elevation angle of 0.31°, compared with the elevation angle of 0.48° if the threshold value for the sea echo within 100 km was eliminated. Several volume scans of Haitang were increased by 2.1%-7.9% for the negative elevation angle of 0.36° compared with the elevation angle of 0.49° . Therefore, the radar detecting capability of typhoons could be improved by the detection of negative elevation angles to some extent. This could make up for the disadvantages of a low detecting capability for remote low-level echo in the common detecting mode. At the same time, a negative elevation angle could be easily influenced by the ground clutter and the close sea wave clutter which interfered with the assessment of the typhoon structure at times. Assessing these advantages and disadvantages, some advantages for using negative elevation angle were discovered from the observation of the typhoons Haitang and Changmi, if the negative elevation angle with radar was selected reasonably in some conditions. As a result, a certain value arose for improving and monitoring the early warning system for typhoons, paying close attention to the detection of negative elevation angles.展开更多
The study aimed to discuss the application of CINRAD/SA radar using negative elevation angle mode in observation of tropical cyclone. Firstly, the calculation formula of the lowest detecting height of CINRAD/SA radar ...The study aimed to discuss the application of CINRAD/SA radar using negative elevation angle mode in observation of tropical cyclone. Firstly, the calculation formula of the lowest detecting height of CINRAD/SA radar was educed, and then the application of negative angle mode in Changle Radar Station was introduced. Through analyzing different observing abilities for tropical cyclone detected at different elevation angles, we discussed the limitation of CINRAD/SA radar using negative angle mode, and finally proposed some suggestions on CINRAD/SA radar using nega- tive elevation angle mode to observe tropical cyclone.展开更多
To address the deficiency in loss diagnostic methods for turbines working at off-design angles of attack,a novel loss decomposition method suitable for cascade flow with large separation is proposed.The method propose...To address the deficiency in loss diagnostic methods for turbines working at off-design angles of attack,a novel loss decomposition method suitable for cascade flow with large separation is proposed.The method proposed has the following advantages over existing methods:(A)It enables refined loss decomposition for cascade flows,capable of identifying the spatial range of specific regions such as shear layers and backflow regions,thereby obtaining the loss characteristics of these regions.(B)The region identification criteria in this method have clear physical meanings,rather than relying on arbitrary area division.(C)The method has good applicability and is suitable for cascade flows under various angles of attack.Validation shows that this method achieves satisfactory results.Based on this method,the loss mechanisms of a low-pressure turbine cascade at a low Reynolds number of 4.3×10^(4)and angles of attack of-5°,-20°,and-45°are investigated using Large Eddy Simulations(LESs).Entropy analysis quantitatively demonstrates significant differences in the composition of losses among flow regions,due to their different flow characteristics.From the perspective of flow regions,wake loss dominates total loss,while loss in backflow region is negligible.Furthermore,the variation mechanisms of loss with incidence differ among different flow regions.展开更多
To meet the requirements of the homogeneous charge compression ignition gasoline engine’s rapid cylinder exhaust gas rate and accurate control of combustion phasing,a residual exhaust gas rate model was proposed.A he...To meet the requirements of the homogeneous charge compression ignition gasoline engine’s rapid cylinder exhaust gas rate and accurate control of combustion phasing,a residual exhaust gas rate model was proposed.A heat dissipation model for gas flow in the exhaust passage and exhaust pipe was established,and the exhaust gas was established.Flow through the exhaust valve was considered as an adiabatic expansion process,the exhaust temperature was used to estimate the temperature in the cylinder at the time that the valve was closed,and the cylinder exhaust gas rate was calculated.To meet the requirements of transient operating conditions,a first-order inertial link was used to correct the thermocouple temperature measurement.Addressing this delay problem and modification of the exhaust wall temperature according to different conditions effectively improved the accuracy of the model.The relative error between the calculated results of this model and the simulation results determined using GT-POWER software was within 3.5%.展开更多
基金funded by the Emphasis Opening Laboratory of Atmospheric Sounding, China Meteorological Administrationthe State Key Laboratory of Disaster Weather, Chinese Academy of Meteoro-logical Science (2007Y004)
文摘Certain feasibilities and features were discussed in typhoon detection by radar with a negative elevation angle according to the relationship between the remote detecting range and the elevation angle of the new generation weather radar, in order to rectify the disadvantages of detecting capability for remote low-level echo with a lowest elevation angle of 0.5° in the common detecting mode. The data obtained from detecting the typhoon of Haitang and Changmi with radar for their negative elevation angles and the observed data for the common lowest elevation angle of 0.5° were compared to each other. The results showed that the detection of remote low level cloud system with radar could be improved by using the negative elevation angle, and the structure and the evolution trend of a typhoon could be better judged. The increasing degree of detection for negative elevation angles in the current volume scanning mode should be helpful for predicting the intensity and developing trend of windstorms, to further improve the capability of warning and nowcasting. The detection of negative elevation angle could also help reveal the development and change of typhoon＇s low level cloud system. As far as the typhoons of Haitang and Changmi were concerned, the detecting area of Changmi was increased by 1.09 times with the negative elevation angle of 0.31°, compared with the elevation angle of 0.48° if the threshold value for the sea echo within 100 km was eliminated. Several volume scans of Haitang were increased by 2.1%-7.9% for the negative elevation angle of 0.36° compared with the elevation angle of 0.49° . Therefore, the radar detecting capability of typhoons could be improved by the detection of negative elevation angles to some extent. This could make up for the disadvantages of a low detecting capability for remote low-level echo in the common detecting mode. At the same time, a negative elevation angle could be easily influenced by the ground clutter and the close sea wave clutter which interfered with the assessment of the typhoon structure at times. Assessing these advantages and disadvantages, some advantages for using negative elevation angle were discovered from the observation of the typhoons Haitang and Changmi, if the negative elevation angle with radar was selected reasonably in some conditions. As a result, a certain value arose for improving and monitoring the early warning system for typhoons, paying close attention to the detection of negative elevation angles.
文摘The study aimed to discuss the application of CINRAD/SA radar using negative elevation angle mode in observation of tropical cyclone. Firstly, the calculation formula of the lowest detecting height of CINRAD/SA radar was educed, and then the application of negative angle mode in Changle Radar Station was introduced. Through analyzing different observing abilities for tropical cyclone detected at different elevation angles, we discussed the limitation of CINRAD/SA radar using negative angle mode, and finally proposed some suggestions on CINRAD/SA radar using nega- tive elevation angle mode to observe tropical cyclone.
基金co-supported by the National Natural Science Foundation of China(No.52176033)the National Science and Technology Major Project,China(No.J2019-II-0012-0032)the Science Center for Gas Turbine Project,China(No.P2022-B-II-009-001)。
文摘To address the deficiency in loss diagnostic methods for turbines working at off-design angles of attack,a novel loss decomposition method suitable for cascade flow with large separation is proposed.The method proposed has the following advantages over existing methods:(A)It enables refined loss decomposition for cascade flows,capable of identifying the spatial range of specific regions such as shear layers and backflow regions,thereby obtaining the loss characteristics of these regions.(B)The region identification criteria in this method have clear physical meanings,rather than relying on arbitrary area division.(C)The method has good applicability and is suitable for cascade flows under various angles of attack.Validation shows that this method achieves satisfactory results.Based on this method,the loss mechanisms of a low-pressure turbine cascade at a low Reynolds number of 4.3×10^(4)and angles of attack of-5°,-20°,and-45°are investigated using Large Eddy Simulations(LESs).Entropy analysis quantitatively demonstrates significant differences in the composition of losses among flow regions,due to their different flow characteristics.From the perspective of flow regions,wake loss dominates total loss,while loss in backflow region is negligible.Furthermore,the variation mechanisms of loss with incidence differ among different flow regions.
基金Hebei Provincial Science and Technology Research Project(Grant No.Z2015092)Langfang Science and Technology Bureau High-Tech Support Project(Grant No.2016011018)Yanjing Institute of Technology Research Project(Grant No.2017YITSRF105)are thanked for joint funding.
文摘To meet the requirements of the homogeneous charge compression ignition gasoline engine’s rapid cylinder exhaust gas rate and accurate control of combustion phasing,a residual exhaust gas rate model was proposed.A heat dissipation model for gas flow in the exhaust passage and exhaust pipe was established,and the exhaust gas was established.Flow through the exhaust valve was considered as an adiabatic expansion process,the exhaust temperature was used to estimate the temperature in the cylinder at the time that the valve was closed,and the cylinder exhaust gas rate was calculated.To meet the requirements of transient operating conditions,a first-order inertial link was used to correct the thermocouple temperature measurement.Addressing this delay problem and modification of the exhaust wall temperature according to different conditions effectively improved the accuracy of the model.The relative error between the calculated results of this model and the simulation results determined using GT-POWER software was within 3.5%.
