分类： 动力与电气工程 >> 工程热物理学 提交时间： 2017-06-26 合作期刊: 《热科学学报》
摘要： The advantage of high efficiency, low SFC (Specific Fuel Consumption), ultra-high bypass ratio turbofan engine attracts more and more attention in modern commercial engine. The intermediate turbine duct (ITD), which connects high pressure turbine (HPT) with low pressure turbine (LPT), has a critical impact on the overall performance of turbine by guiding flow coming from HPT to LPT without too much loss. Therefore, it becomes more and more urgent to master the technique of designing aggressive, even super-aggressive ITD. Much more concerns have been concentrated on the duct. However, in order to further improve turbine, LPT nozzle is arranged into ITD to shorten low pressure axle. With such design concept, it is obvious that LPT nozzle flow field is easily influenced by upstream duct structure, but receives much less interests on the contrary. In this paper, numerical method is used to investigate the effects of length of ITD with upstream swirl blades on LPT nozzle. Nine models with the same swirl and nozzle blades, while the length of ITD is the only parameter to be changed, will be discussed. Finally, several conclusions and advices for designers are summarized. After changing axial length of ducts, inlet and outlet flow field of nozzle differs, correspondingly. On the other hand, the shearing stress on nozzle blade (suction and pressure) surface presents individual feature under various inlet flow. In addition to that, "Clocking-like effect" is described in this paper, which will contribute much to the pressure loss and should be paid enough attention.
分类： 物理学 >> 核物理学 提交时间： 2023-07-06
摘要： Proton computed tomography (CT) has a distinct practical significance in clinical applications. It eliminates 35% errors caused by the transformation of Hounsfield unit (HU) to relative stopping power (RSP) valueswhen using X-ray CT for positioning andtreatment planning systems (TPSs). Following the development of FLASH proton therapy, there are increased requirements for accurate and rapid positioning in TPSs. Thus, anewrapid proton CT imaging mode is proposed based on sparsely sampled projections. The proton beam wasboosted to 350 MeV by a compact proton linear accelerator (linac). In this study,thecomparisons of the proton scattering with the energyof 350 MeV and 230 MeV are conducted based on GEANT4simulations.Asthe sparsely sampledinformation associated with beam acquisitions at 12angles is not enough for reconstruction, X-ray CT is used as a prior image. The RSP map generated by converting the X-ray CT was constructed based onMonte Carlo simulations. Consideringtheestimationof the most likely path (MLP), the prior image-constrained compressed sensing (PICCS) algorithm isused to reconstruct images from twodifferent phantoms using sparse protonprojections of 350 MeV parallel proton beam. The results show that it is feasible to realize the proton image reconstruction with the rapid protonCT imaging proposed in this paper. It can produce RSP maps withmuchhigher accuracy for TPSs and fast positioning to achieve ultra-fast imaging for real-time image-guided radiotherapy(IGRT) in clinical proton therapyapplications.
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