Pub Date : 1900-01-01DOI: 10.1109/IBCAST.2013.6512159
M. A. Chishty, H. Hamdani, K. Parvez
Flow controlling of boundary layers separation of low-pressure (LP) turbine blade is still a high leverage area for advent of high lift and ultra-high lift LP turbines. At cruising conditions, the Reynolds number in the LP turbine reduces (due to the decrease in air density) to the critical value that flow starts to separate from the blade suction surface. In the present study, cascade T106A is used to control the laminar separation bubble on the suction side of the blade. Fluent® commercial CFD code with gamma theta transition model has been employed to study the boundary layer separation at various different turbulent intensities. Numerical results are validated with the available experimental data and are in good agreement. An optimize dimple is used to control the boundary layer separation at low and intermediate turbulent intensities. Normalized loss coefficient is reduced to about 5% with the help of optimal dimple size and location, which increase the LP turbine efficiency. Cp plots and boundary layers profiles are made for flow visualization.
{"title":"Effect of turbulence intensities and passive flow control on LP turbine","authors":"M. A. Chishty, H. Hamdani, K. Parvez","doi":"10.1109/IBCAST.2013.6512159","DOIUrl":"https://doi.org/10.1109/IBCAST.2013.6512159","url":null,"abstract":"Flow controlling of boundary layers separation of low-pressure (LP) turbine blade is still a high leverage area for advent of high lift and ultra-high lift LP turbines. At cruising conditions, the Reynolds number in the LP turbine reduces (due to the decrease in air density) to the critical value that flow starts to separate from the blade suction surface. In the present study, cascade T106A is used to control the laminar separation bubble on the suction side of the blade. Fluent® commercial CFD code with gamma theta transition model has been employed to study the boundary layer separation at various different turbulent intensities. Numerical results are validated with the available experimental data and are in good agreement. An optimize dimple is used to control the boundary layer separation at low and intermediate turbulent intensities. Normalized loss coefficient is reduced to about 5% with the help of optimal dimple size and location, which increase the LP turbine efficiency. Cp plots and boundary layers profiles are made for flow visualization.","PeriodicalId":276834,"journal":{"name":"Proceedings of 2013 10th International Bhurban Conference on Applied Sciences & Technology (IBCAST)","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114498368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1109/IBCAST.2013.6512179
J. Yousaf, Muhammad Amin, S. Iqbal, H. Durrani, M. K. Amin
At low frequencies, DC-DC converter is one of the noisiest components that can adversely affect conducted emission (CE) measurements. Since DC-DC converter does the switching at a frequency that is proportional to the load, there is a strong component of interference signal in a certain frequency band that depends upon the load. It not only includes the fundamental frequency but also its harmonics. The dynamic range of the amplitude and frequency of this interference signal is important to analyze for the design of proper pre-filtering stage. In this paper, we shall present the experimental measurements of conducted emissions for DC-DC converter with and without using the filter and would show the importance of proper filter design to bring the conducted emissions within the envelope of MILSTD-461F. The measurements indicate that without filter there is a strong interference signal at the fundamental frequency and its harmonics which are well above the threshold value. As the properly designed filter is inserted, the conducted emissions fall within the envelope of MIL STD-461F.
{"title":"Conducted emission analysis of DC-DC converters and proper selection of pre-filtering stage","authors":"J. Yousaf, Muhammad Amin, S. Iqbal, H. Durrani, M. K. Amin","doi":"10.1109/IBCAST.2013.6512179","DOIUrl":"https://doi.org/10.1109/IBCAST.2013.6512179","url":null,"abstract":"At low frequencies, DC-DC converter is one of the noisiest components that can adversely affect conducted emission (CE) measurements. Since DC-DC converter does the switching at a frequency that is proportional to the load, there is a strong component of interference signal in a certain frequency band that depends upon the load. It not only includes the fundamental frequency but also its harmonics. The dynamic range of the amplitude and frequency of this interference signal is important to analyze for the design of proper pre-filtering stage. In this paper, we shall present the experimental measurements of conducted emissions for DC-DC converter with and without using the filter and would show the importance of proper filter design to bring the conducted emissions within the envelope of MILSTD-461F. The measurements indicate that without filter there is a strong interference signal at the fundamental frequency and its harmonics which are well above the threshold value. As the properly designed filter is inserted, the conducted emissions fall within the envelope of MIL STD-461F.","PeriodicalId":276834,"journal":{"name":"Proceedings of 2013 10th International Bhurban Conference on Applied Sciences & Technology (IBCAST)","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127156764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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