Aerospace Science and Technology
Mohammad Hossein Moghimi EsfandAbadi; Adnan Mohammadi; Mohammad Hassan Djavareshkian
Abstract
This research delves into the intricate realm of supersonic inlet design for ramjet engines, honing in on the critical aerodynamic considerations and optimization of performance factors. At Mach 2.5, the study meticulously scrutinizes pivotal design parameters, including the placement and number of inclined ...
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This research delves into the intricate realm of supersonic inlet design for ramjet engines, honing in on the critical aerodynamic considerations and optimization of performance factors. At Mach 2.5, the study meticulously scrutinizes pivotal design parameters, including the placement and number of inclined shocks, cowl-lip positioning, throat area, spike location, and diffuser length. Computational fluid dynamics simulations are harnessed to unravel the intricate flow dynamics and assess the proposed inlet geometry's performance.The findings reveal a nuanced relationship between back pressure and shock wave positioning, where increasing back pressure initiates a shift in the shock wave, impacting the flow state. The paper delineates this transition, emphasizing the pivotal back pressure range of 300,000 to 350,000 pascals, where optimal shock wave alignment corresponds with design parameters, achieving a supercritical state.However, elevating back pressure beyond this range triggers a sub-critical state and mass flow overflow as the shock exits the throat.the study explores various performance metrics, encompassing drag coefficient, distortion coefficient, mass flow ratio and total pressure recovery under varying back pressure conditions. The outcomes underscore the merits of higher back pressures, which mitigate drag coefficient and distortion while amplifying TPR.In the sub-critical state, MFR diminishes due to shock wave displacement beyond the intake opening.This research illuminates the intricate dance of aerodynamics within ramjet engine inlets and underscores the paramount significance of optimizing inlet geometry to unlock heightened performance. It effectively encapsulates the essence of the full article, enticing readers to embark on a deeper exploration of this crucial area of aerospace engineering.
Aerospace Science and Technology
G. R. Abdizadeh; Sahar Noori; Mohammad Saeedi; Hamidreza Tajik
Abstract
Designing flattened miniature heat pipes (FMHPs) for electronic devices is a challenging issue due to high heat flux and limited heat dissipation space. It requires understanding the combined effects of the sintered-grooved wick structure, double heat sources, and flat thickness on heat pipes' thermal ...
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Designing flattened miniature heat pipes (FMHPs) for electronic devices is a challenging issue due to high heat flux and limited heat dissipation space. It requires understanding the combined effects of the sintered-grooved wick structure, double heat sources, and flat thickness on heat pipes' thermal efficiency. Therefore, the aim of this study is to numerically investigate the effects of the FMHP with a hybrid wick on the thermal performance of its double heat sources acting as the CPU and GPU in notebook PCs. A transient 3D finite volume method was used to solve the governing equations and assisted boundary conditions. The cylindrical heat pipe with a 200 mm length and 6 mm outside diameter is flattened into 2, 2.5, 3, and 4 mm final thicknesses (FT). The obtained results show that the final critical thicknesses with the lowest thermal resistance are 2.5 and 3 mm for hybrid and grooved wick structures, respectively. Therefore, FMHP with hybrid wicks can be flattened about 8% more. Hybrid wick structures have the best effect on FMHP thermal performance at FT=2.5 mm
Aerospace Science and Technology
Sam Mohamad Hassan Pouryoussefi; Sohrab Gholamhosein Pouryoussefi
Abstract
Importance of study of pulsating heat pipes (PHPs) behavior and limitations in conducting experimental studies, the necessity of numerical simulations is getting critical in this area. In present work, numerical simulations are carried out for pulsating heat pipes. Thermal performance of closed loop ...
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Importance of study of pulsating heat pipes (PHPs) behavior and limitations in conducting experimental studies, the necessity of numerical simulations is getting critical in this area. In present work, numerical simulations are carried out for pulsating heat pipes. Thermal performance of closed loop pulsating heat pipes is investigated at different operating conditions such as evaporator heating power and filling ratio. Water, ethanol, methanol and acetone are employed as working fluids. A two-dimensional single loop PHP is used for present study. Computational Fluid Dynamics (CFD) video technique is employed for flow visualization purpose. Perfect match was observed between the present CFD video clip and previous experimental video-based studies in terms of flow pattern and behavior. Present study shows how researchers can benefit from developments of numerical tools to test pulsating heat pipes behavior at different operating conditions or different working fluids without facing difficulties and limitations of applying laboratory thermal measurement equipment or high-speed cameras. The CFD video clip as result of numerical simulation was found very informative for flow visualization purpose. The simulated clip made it much easier to capture phenomena occur in a pulsating heat pipe. The thermal performance investigation at different operating conditions and working fluids was found very informative in terms of application and design purposes especially for experimental studies. By increasing heating power greater than 60 W, circulation velocity was increased for most cases. Phase contour videos are inserted at the bottom of the article.
Aerospace Science and Technology
Hamed Arhami; Mohammad Mazidi Sharfabadi
Abstract
In this research, combustion modeling inside the combustion chamber of a typical turboprop engine has been investigated. The complex geometry of this combustion liner was modeled according to the technical drawings and the turbulent flow and internal combustion were simulated numerically and three-dimensionally. ...
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In this research, combustion modeling inside the combustion chamber of a typical turboprop engine has been investigated. The complex geometry of this combustion liner was modeled according to the technical drawings and the turbulent flow and internal combustion were simulated numerically and three-dimensionally. The non-premixed combustion model is used to simulate combustion and the K-ω method is used to simulate turbulent flow. This study investigated how the combustion phenomenon occurs, the internal temperature distribution, the outlet, and the wall of the combustion tube, for which comprehensive three-dimensional data were not previously available. These simulations have identified the weaknesses of the combustion tube and by eliminating these weaknesses, the problem of reducing the efficiency of several gas turbine engines has been solved. Comparison of the results of the present study with a similar numerical analysis showed that the results of this study are more in line with laboratory results. The results of the simulation of combustion pipe defects show that the combustion liner that had a welding line near the outlet had a 25% higher pressure drop than a typical combustion liner and the effective cross-sectional area of the fluid flow was reduced by 11%. The output of a repaired combustion tube is different from a typical type.
M.R. Salimi; M. Taeibi Rahni; Mahdi Ramezanizadeh
Volume 9, Issue 1 , March 2012
Abstract
A new design concept is introduced to control the near-wall integration between the hot-gas boundary layer and the cooling jets in order to enhance the adiabatic film cooling effectiveness of the gas turbine blades. In this new approach, another film cooling port, having a very low blowing ratio, which ...
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A new design concept is introduced to control the near-wall integration between the hot-gas boundary layer and the cooling jets in order to enhance the adiabatic film cooling effectiveness of the gas turbine blades. In this new approach, another film cooling port, having a very low blowing ratio, which prevents formation of the counter-rotating vortex pare, is applied just upstream of the main film cooling jet. The fluid injected from the small upstream port changes the flow pattern, resultsinwider horseshoe vortices in the span-wise direction, and generates a more uniform distribution of the coolant film. Also, this coolant fluid flows towards the low pressure region located just behind the main film-cooling hole. Therefore, by producing a cold layer of gas beneath the coolant jet and diverting the hot cross-flow gases into this area, it significantly improves the film cooling effectiveness, especially in the near field of the main jet. The obtained results show lower stream-wise velocity gradients near the wall, which considerably decreases the wall shear stresses, comparing to the regular film cooling holes.