Shuiting Ding

Active Control Thermal-Loading Method to Ameliorate Stress in Aeroengine Turbine Disk

An active control thermal loading method to ameliorate stress in an aeroengine turbine disk has been theoretically and numerically investigated on a rotating uniform thickness disk model under equal consumption of cooling air and heating energy conditions. The hub of the disk is actively heated to achieve energy redistribution and analogous V-shaped temperature distribution of the disk. The relationship between energy distribution and stress level of the disk is first built by theoretical analysis, and then the computational fluid dynamics and finite element simulations are carried out to validate the feasibility and validity of the theoretical analysis. The comparison between computed data and theoretical results is also performed. Results show that the pulling effect from an active produced reverse temperature gradient can counteract the thermal stress caused by a positive temperature gradient, and parts of stress from centrifugal force, enabling the stress level of the disk to be declined. In addition,...

Evaluation of Thermal Loadings to Ameliorate Stress in a Rotating Disk

For the purpose of safety design of a turbine disk, the fundamental termoelasticity mechanics associated with the thermal loadings imposed on the inner and outer surfaces of a rotating disk have been studied theoretically and numerically. The relationship between the stress level and the thermal boundary loadings was obtained theoretically to identify the existence of four possible stress states of the disk. Then, the computational fluid dynamics and finite element simulations were carried out to validate the theoretical analysis. Results showed that the existence and extent of the four stress states were governed by the thermal loading combination (Q˜e−Φ) on the inner and outer surface, respectively, and then their regimes had been delineated. After the thermal loading design was employed, the maximum equivalent stress against the conventional model (Φ=0) had fallen, except in some cases of state 4. Hence, the thermal loadings on the boundaries of the disk should be designed in an adequate range in order...

Optimal Design Process for Aeroengine Turbine Disks Based on Energy Management

The objective of the optimal design process for aeroengine turbine disks is to acquire configurations with minimum weight, satisfying the strength demand. In this paper, an optimal design process for aeroengine turbine disks based on energy-management technology was presented and the effect of different energy-management strategies on stress level and disk configuration was investigated. In this process, thermal conditions were taken as variables rather than passively accepted as conditions in a conventional optimal design process. That is, under the constant cooling condition, the heating energy was redistributed by energy-management strategies, and part of the heating energy was transferred to actively heat the inner rim of the disk. Then, the temperature and stress distribution correspondingly varied, and consequently determined the optimal configuration. Using the proposed optimal design process and the general optimization method of inscribed hyperspheres, a simplified aeroengine turbine disk was opt...

Flow and Heat Transfer in a Rotating and Non-Rotating Wedge-Shaped Cooling Passage with Ribs and Pin Fins

Cooling the trailing edge of a gas-turbine vane/blade typically involves an embedded wedge-shaped duct in a very confined volume, where coolant enters the duct radially and then directed to flow axially by ribs and pin fins to cool the entire trailing-edge region as efficiently and uniformly as possible. CFD simulations based on steady RANS – compressible formulation with temperature-dependent properties closed by the shearstress transport turbulence model – were performed to study the flow and heat transfer in a wedge-shaped duct with ribs and pin fins under rotating and non-rotating conditions. The objective of this study is twofold. The first is to understand the flow mechanisms by which ribs and pin fins turn radially outward flow to flow in the axial direction. The second is to understand what features of the flow and heat transfer obtained under laboratory conditions – where measurements have been made to validate this computational study – can be extrapolated to engine-relevant operating conditions. Results obtained show pin fins judiciously placed around the turn of the wedge-shaped duct to greatly reduce the size of the separated region when the coolant jets radially into the wedge-shaped duct. Also, pin fins provide flow resistance to control the flow direction, and the uniformity of the flow along the cross section of the wedge-shaped duct in addition to enhancing surface heat transfer via horseshoe vortices about each pin fin. The staggered array of ribs along the radial direction of the wedge-shaped duct was found to create up to three sets of recirculating flows that cause the flow entering the duct in the radial direction to spiral towards the axial direction with one created by the stagnation region upstream of each rib, one by the separation at the downstream edge of each rib, and one by the cavity-like flow between the aforementioned recirculating flows. When there is rotation, the staggered array of ribs was found to minimize the adverse effects of centrifugal buoyancy by confining flow separation to be between the ribs on the leading face. On what could be learned under laboratory condition that are meaningful for engine-relevant conditions, all of the aforementioned flow mechanisms are the same and the flow features are qualitatively similar. The exception is the size of the separated region at the tip of the wedge-shaped duct under non-rotating conditions, which is very large for the laboratory condition and very small for the engine-relevant condition.

Investigation of Flow and Heat Transfer Instabilities in a Rotating Cavity With Axial Throughflow of Cooling Air

To study the instability of flow and heat transfer within the rotation frame, a rotating cavity with air axial throughflow was studied numerically and efforts were focused upon the flow structure evolution with the increase of Rayleigh number. The cavity can be divided into two typical zones: the Rayleigh_Benard-like convection zone occupying the upper cavity and the forced convection zone down under. These two zones interact with each other via the exchange of mass, momentum and energy. Numerical analysis indicated that, for a fixed inlet Reynolds number, there always exists a critical Rayleigh number Rac , below which the flow is stable and over which the flow becomes unstable and time-dependent. Among all the forces in momentum equations, the centrifugal induced buoyancy force was found to be the key factor leading to instability, while the Coriolis force pays its contribution to instability by inducing its occurrence earlier and the flow structure more complicated though it may not lead to instable by itself. The instability originated in the upper R-B-like convection zone develops into the whole region with the increase of Rayleigh number. For the heat transfer, the characteristic distribution of local Nur along the disk surface is remarkably different before and right after the occurrence of instability due to flow structure variation though the averaged Nuav varies slightly. It was found that the heat transfer, however, does experience a sudden increase when the flow instability develops further with Ra increase.Copyright

Heat Transfer Coefficients of Film Cooling on a Rotating Turbine Blade Model—Part I: Effect of Blowing Ratio

Experimental investigations were performed to measure the local heat transfer coefficient (hg ) distributions of film cooling over a flat blade under both stationary and rotating conditions. Film cooling was via a straight circular hole of 4 mm in diameter located in the middle section of the blade angled 30° along the streamwise direction and 90° along the spanwise direction. The Reynolds (ReD ) number based on the mainstream velocity and the film hole diameter was fixed to be 3191 and the rotating speeds (ω) were either 0 and 800 rpm; the film cooling blowing ratios ranged from 0.4 to 2.0 and two averaged density ratios of 1.02 and 1.53 were employed with air and carbon dioxide (CO2 ) as the coolant respectively. Thermochromic liquid crystal (TLC) was used to measure the solid surface temperature distributions. Experimental results showed that (1) in the stationary case, the blowing ratio has a significant influence on the non-dimensional heat transfer coefficient (hg /h0 ) especially in the near hole region. (2) the film trajectory in rotation had an obvious deflection in the spanwise direction, and the deflection angles on the suction surface are larger than that on the pressure surface. This was attributed to the combined action of the Coriolis force and centrifugal force. (3) in the rotating case, for CO2 injection, the magnitude of heat transfer coefficient on the pressure surface is reduced compared with the stationary case and the blowing ratio has smaller effects on hg /h0 distribution. However, on the suction surface, the heat transfer coefficient at x/D<1.0 is enhanced and then rapidly reduced to be also below the stationary values. For air injection, rotation also depresses the hg /h0 for both the pressure and the suction surface. (4) the density ratio shows a considerable effect on the streamwise heat transfer coefficient distributions especially for the rotating cases.

Heat Transfer Coefficients of Film Cooling on a Rotating Turbine Blade Model: Part I—Effect of Blowing Ratio

Experimental investigations were performed to measure the local heat transfer coefficient (hg ) distributions of film cooling over a flat blade under both stationary and rotating conditions. Film cooling was via a straight circular hole of 4 mm in diameter located in the middle section of the blade angled 30° along the streamwise direction and 90° along the spanwise direction. The Reynolds (ReD ) number based on the mainstream velocity and the film hole diameter was fixed to be 3191 and the rotating speeds (ω) were either 0 and 800 rpm; the film cooling blowing ratios ranged from 0.4 to 2.0 and two averaged density ratios of 1.02 and 1.53 were employed with air and carbon dioxide (CO2 ) as the coolant respectively. Thermochromic liquid crystal (TLC) was used to measure the solid surface temperature distributions. Experimental results showed that (1) in the stationary case, the blowing ratio has a significant influence on the non-dimensional heat transfer coefficient (hg /h0 ) especially in the near hole region. (2) the film trajectory in rotation had an obvious deflection in the spanwise direction, and the deflection angles on the suction surface are larger than that on the pressure surface. This was attributed to the combined action of the Coriolis force and centrifugal force. (3) in the rotating case, for CO2 injection, the magnitude of heat transfer coefficient on the pressure surface is reduced compared with the stationary case and the blowing ratio has smaller effects on hg /h0 distribution. However, on the suction surface, the heat transfer coefficient at x/D<1.0 is enhanced and then rapidly reduced to be also below the stationary values. For air injection, rotation also depresses the hg /h0 for both the pressure and the suction surface. (4) the density ratio shows a considerable effect on the streamwise heat transfer coefficient distributions especially for the rotating cases.Copyright

Efficient Probabilistic Risk Assessment for Aeroengine Turbine Disks Using Probability Density Evolution

For the risk assessment of turbine rotor disks, the probability of failure for a certain type of disk (after N flight cycles) is a vital criterion for estimating whether the disk is safe enough to ...

Experimental Study of Sister Hole Film Cooling Performance in a Rotating Flat Plate Model

Film cooling performance of a sister hole was investigated in a flat plate model by applying Thermochromic Liquid Crystal (TLC) technique under the stationary and rotating conditions. The flat plate model is installed in the test section. The sister hole include one main hole and two additional side holes with the smaller diameter in the spanwise direction. The diameter of the main hole is 4 mm and the injection angle is 30°. The density ratio of coolant to mainstream is 1.05. The Reynolds number (ReD) based on the velocity of mainstream and the diameter of the main hole are 2300, 3400 and 4500. Four rotational speeds of 200, 400, 600 and 800 rpm are conducted on both pressure side (trailing wall) and suction side (leading wall) with the blowing ratio varying from 0.14 to 3.5. The effects of blowing ratio, Reynolds number (ReD) and rotation number are mainly analyzed according to film coverage and film cooling effectiveness. The results show that the film performance firstly increases then decreases with the rising of blowing ratio, the optimal blowing ratio is about M=0.5. The film cooling performance is improved with higher Reynolds number (ReD). Under the rotation condition, the film trajectory has an obvious centrifugal deflection which can be enhanced by higher rotation number on the pressure side, and the film deflection moves a little centripetally on the suction side. The film cooling effectiveness on the suction side increases with the rising of rotation number and it is higher than that on the pressure side.Copyright

A NEW APPROACH TO SIMULATE THE FLUID NETWORK OF UNSTEADY FLOW

In this paper, a newly deduced numerical method is originally applied to solve the complicated transient fluid network in the engine and with that method a new program called UFSSP (Unsteady Fluid Network System Simulation) is developed. As a case study, the UFSSP has been applied to pressurization of a propellant tank, which has been provided a published correlation and numerically predicted by the advanced program in this field called General Fluid System Simulation Program (GFSSP) by NASAs Marshall Space Flight Center (MSFC). Comparisons among the numerical results of the UFSSP, those published data of the GFSSP and the results from the published correlation are presented. It is found that the numerical results of the UFSSP model are in better agreement with the results from the published correlation than those achieved from the GFSSP model. Furthermore, the proposed method leads to an improved computational algorithm and, as a consequence, a significant stability of the computation.