EFFECT OF RADIATION ON HEAT TRANSFER INSIDE AEROENGINE COMPRESSOR ROTORS

The blade clearance in aero-engine compressors is mainly controlled by the radial growth of the compressor discs, to which the blades are attached. This growth depends on the radial distribution of the disc temperature, which in turn is determined by the heat transfer inside the internal rotating cavity between adjacent discs. The buoyancy-induced convection inside the cavity is significantly weaker than that associated with the forced convection in the external mainstream flow, and consequently radiation between the cavity surfaces cannot be ignored in the calculation of the disc temperatures. In this paper, both the Monte Carlo Ray-Trace Method and the view factor method are used to calculate the radiative flux when the temperatures of the discs, shroud and inner shaft of the compressor vary radially and axially. Given distributions of surface temperatures, the blackbody and grey body heat fluxes were calculated for the discs, shroud and inner shaft in two experimental compressor rigs and in a simulated compressor stage. For the experimental rigs, although the effect of radiation was relatively small for the case of large Grashof numbers, the relative effect of radiation increases as Gr (and consequently the convective heat transfer) decreases. For the simulated compressor, with a pressure ratio of 50:1 for state-of-art aircraft engines, radiation could have a significant effect on the disc temperature and consequently on the blade clearance; the effect is predicted to be more prominent for next generation of aircraft engines with pressure ratios up to 70:1.

Thermo-Structural Analysis of High-Pressure Turbine Blade

Turbine blade tip clearance plays major role in smooth running of axial turbines. The turbine blade clearance contributes 20-40% of total loss in gas turbine. In Rolls Royce MT2 Turbine with 2% tip to span clearance ratio, tip clearance accounts for 40% of total losses. Turbine blade clearance is necessary as the turbine blade operates at very high temperature up to 1700 ºC and very high centrifugal load. Small turbine tip clearance may forbid expansion of turbine blade which will result in turbine tip rubbing with the casing. High pressure turbine blade experiences high thermal and centrifugal stress. The objective of this paper is to study the individual and combined effect of these stress. The material used for analysis is cast based nickel alloy IN-738. The melting range of this alloy is 1230-1315 ºC with thermal expansion coefficient of 15.39E-6 per ºC. The turbine blade geometry with height 120 mm is used for analysis. The Mathematical modelling of above geometry shows that the centrifugal force with rotation velocity 100 rad/s produces 0.00252424 mm elongation and combined thermal-centrifugal loading produces 1.46520576 mm elongation. The results form ANSYS is used for verification and the elongation due to centrifugal stress is 0.0014885 mm and combined stress produces elongation of 1.2608 mm. The total elongation from analytical method and ANSYS are similar. It shows that the effect due to centrifugal force on turbine blade is less compared to thermal effect. For operating condition of 816 ºC temperature and 100 rad/s rotational velocity, the overall stress contributes around 1.22 % elongation of turbine blade span.

Lateral Forces in Rolling-Cut Shearing and Their Consequences on Common Edge Defects

This paper deals with the detailed analysis of the lateral process forces in rolling-cut shearing of heavy steel plates and their impact on edge defects. Rolling-cut shearing is still the most common method of heavy-plate side trimming. However, this method can entail edge defects like uneven longitudinal shape as well as burr and fractures in the area of the cut-changeover (beginning and end of the periodical cuts). In the existing literature, neither the root cause of these edge defects nor their nexus with the upper blade trajectory (blade drive-kinematics) has been analyzed in detail. In this work, these issues will be explored based on the finite element method (FEM) simulations and measurements from an industrial plant. The complex interrelation between drive-kinematics, varying lateral force, unintended lateral motion of the upper blade, unintended variation of the blade clearance, and quality defects is analyzed. The variation of the lateral force is identified as the root cause of such quality defects and a physical explanation for variations of the lateral force is given. The detailed understanding of the shearing process serves as a solid basis for an optimization and re-design of the drive-kinematics in a future work. Measurements from an industrial plant and simulation results show good agreement and thus confirm the theory. The results are transferable to other rolling-cut trimming shears.

Coupled Aerothermal Modeling of a Rotating Cavity With Radial Inflow

Flow and heat transfer in an aero-engine compressor disk cavity with radial inflow has been studied using computational fluid dynamics (CFD), large eddy simulation (LES), and coupled fluid/solid modeling. Standalone CFD investigations were conducted using a set of popular turbulence models along with 0.2 deg axisymmetric and a 22.5 deg discrete sector CFD models. The overall agreement between the CFD predictions is good, and solutions are comparable to an established integral method solution in the major part of the cavity. The LES simulation demonstrates that flow unsteadiness in the cavity due to the unstable thermal stratification is largely suppressed by the radial inflow. Steady flow CFD modeling using the axisymmetric sector model and the Spalart–Allmaras turbulence model was coupled with a finite element (FE) thermal model of the rotating cavity. Good agreement was obtained between the coupled solution and rig test data in terms of metal temperature. Analysis confirms that using a small radial bleed flow in compressor cavities is effective in reducing thermal response times for the compressor disks and that this could be applied in management of compressor blade clearance.

Coupled Aero-Thermal Modeling of a Rotating Cavity With Radial Inflow

Flow and heat transfer in an aero-engine compressor disc cavity with radial inflow has been studied using computational fluid dynamics (CFD), large eddy simulation (LES) and coupled fluid/solid modelling. Standalone CFD investigations were conducted using a set of popular turbulence models along with 0.2° axisymmetric and a 22.5° discrete sector CFD models. The overall agreement between the CFD predictions is good, and solutions are comparable to an established integral method solution in the major part of the cavity. The LES simulation demonstrates that flow unsteadiness in the cavity due to the unstable thermal stratification is largely suppressed by the radial inflow. Steady flow CFD modelling using the axisymmetric sector model and the Spalart-Allmaras turbulence model was coupled with a finite element (FE) thermal model of the rotating cavity. Good agreement was obtained between the coupled solution and rig test data in terms of metal temperature. Analysis confirms that use of a small radial bleed flow in compressor cavities is effective in reducing thermal response times for the compressor discs and that this could be applied in management of compressor blade clearance.

Waste Tire Crushing and Shearing Machine Tools Working Methods of the Gap

The fine particles of tire shear blade gap adjustment requirements quickly and gap value can be controlled . Thus raised the following two questions. One is how to adjust the gap , and the second is to determine the value gap . For the above two issues are now designed shears no solution. The reason is that the tool cutting edge after installation manual measurement gap not .Machinery and no set automatic detection devices. Inserts knife blocks knife is not conducive to the gap between the tool to adjust. Size of the gap of the tool cutting of the rubber particles under conditions not very clear , the blade clearance can be adjusted using the structural design . Change processing means for processing pole . Setback legitimate work method can reduce the impact on the processing tool clearance . Cutting edge in multi-processing methods . Blade gap introduced into the gap and squeeze setback cut gap . Powder particles in the gap after being introduced to squeeze into the machining gap cutting machining . Particles larger than the machining gap will be extrusion . Cutting tool clearance is no longer the main influence .

The Finite Element Imitate of the Best Adjusting of Shear Blade Clearance of Disk Shear in Cutting Plate

In this paper the main factors of impacting the quality in cutting the plate between the Shear blade clearance adjustment and control were analyzed, Focused on further analyzing all relevant factors on adjusting the Shear blade clearance , combined with the accumulated process parameters in production of one certain Thick Steel Plate Plant . Proposed for the first time the mathematical models of the best adjusting of Shear blade clearance of disk shear in cutting plate，and also make a imitate testing of finite element.

The Theory Analysis of the Blade Gap’s Adjusting for Rolling Shear

The horizontal blade gap is a key problem in rolling shear. The mathematical model is established in this paper. This model is optimized based on traditional model. The optimized formula of blade clearance is obtained and the stress is analyzed in cutting process. It is benefit for improving shear quality.