Procedure for determining the constants of JH-2 (Johnson – Holmquist) dynamic fracture model for brittle materials

2021 ◽  
Vol 87 (12) ◽  
pp. 48-54
Author(s):  
O. G. Krutova ◽  
N. N. Berendeev ◽  
V. N. Chuvildeev ◽  
N. V. Melekhin
Keyword(s):  
Experimental Data ◽  
Aluminum Oxide ◽  
Dynamic Fracture ◽  
High Speed ◽  
Brittle Materials ◽  
The Third ◽  
Classical Procedure ◽  
Simplified Method ◽  
Corundum Plate ◽  
Independent Parameters

A simplified method for evaluating the constants in the JH-2 (Johnson – Holmqvist) model of the dynamic fracture for brittle materials is presented. The classical procedure suggests the use of 21 independent parameters describe the material, and the problem of their determination entails a large number of calculations experiments which hamper the use of the JH-2 model. The proposed technique requires fewer complex calculations and experimental data to determine the parameters of the material thus making it more feasible in use. In this work, the technique is used to search for the parameters of aluminum oxide (Al2O3) with a density of 99.5%, which is the material of a ceramic barrier subjected to high-speed interaction with the impactor. We present the results of three tests for penetration of a corundum plate: two of them are used to determine the constants of the model, and the third is used to verify the obtained values. Note that, the results obtained using the presented approach match quite accurately the experimental data, which is demonstrated in the course verification of the procedure.

Simulation of Gasless Combustion of Mechanically Activated Solid Powder Mixtures

2010 ◽  
Vol 63 ◽  
pp. 213-221 ◽  
Author(s):  
Sergey Rashkovskiy
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Gasless Combustion ◽  
Digital Recording ◽  
Powder Mixtures ◽  
Second Stage ◽  
The Third ◽  
Third Stage ◽  
Three Stages ◽  
Ignition And Combustion

The direct 3D method of numerical simulation of gasless combustion of mechanically activated solid powder mixtures is developed. The method under consideration falls into three stages. On the first stage, a simulation of mixture structure is performed. An analysis of the structure obtained in simulations is carried out. On the second stage, the thermal conductivity of solid powder mixture is calculated. On the third stage of simulation, the ignition and combustion of each particle of the mixture is considered with taking into account of heat exchange between contacting particles. The results of numerical simulations are represented dynamically and compared with the experimental data, obtained by high-speed digital recording of mechanically activated SHS systems combustion.

Selecting Cavity Geometries for Improving the Aerodynamic Performance of an Axial Compressor

2014 ◽  
Author(s):  
Diego Flores ◽  
Joerg R. Seume
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Flow Direction ◽  
Axial Compressor ◽  
Turbulence Models ◽  
Flow Path ◽  
Main Flow ◽  
Tip Clearance ◽  
The Third ◽  
Radial Profiles

Designers and researchers have traditionally sought to minimize aerodynamic losses in turbomachinery without considering the influence of fillets, seals and cavities. The validity of this assumption is investigated in the present paper. Three different cavity geometries have been implemented in the third stage of a four-stage high-speed axial compressor. To better understand the interaction between the main flow path and the secondary flow caused by leakage through labyrinth seals, three different cavity outlet angles have been investigated: 90°, 45°, and 135° with respect to the main flow path direction. Moreover, three different clearances between the seal tips and the stator have been used in order to investigate the leakage mass flow inside the cavity. Three-dimensional steady RANS simulations with two different turbulence models using the TRACE solver by DLR have been performed in all cases. The SST turbulence model showed higher fidelity when compared to experimental data and proved more sensitive to variations of parameters studied. A comparison of aero-thermodynamic results in the main flow path for the different configurations at the inlet and outlet of the cavities shows that the radial profiles are strongly influenced by clearance height H and cavity outlet angle a in the third stator as well as rotor. A cavity outlet directed against the main flow direction gives the best results in terms of compressor overall efficiency. The results also reveal some modeling limitations in that neither of the two turbulence models can precisely predict the progressive temperature rise noticed in the experimental data above of 55% blade height in the third stator and rotor, pointing at deficiencies in modeling the tip clearance vortex.

Vapour-liquid equilibrium in the isobutyl formate-isobutyl alcohol and n-butyl formate-isobutyl alcohol systems at atmospheric pressure

1979 ◽  
Vol 44 (12) ◽  
pp. 3501-3508 ◽  
Author(s):  
Jan Linek
Keyword(s):  
Experimental Data ◽  
Fourth Order ◽  
Atmospheric Pressure ◽  
Isobutyl Alcohol ◽  
Liquid Equilibrium ◽  
The Third

Isobaric vapour-liquid equilibria in the isobutyl formate-isobutyl alcohol and n-butyl formate-isobutyl alcohol systems have been measured at atmospheric pressure. A modified circulation still of the Gillespie type has been used for the measurements. The experimental data have been correlated by means of the third- and fourth-order Margules equations.

Development and Validation of a Three-Dimensional Multiphase Flow CFD Analysis for Journal Bearings in Steam and Heavy Duty Gas Turbines

2012 ◽  
Author(s):  
Stephan Uhkoetter ◽  
Stefan aus der Wiesche ◽  
Michael Kursch ◽  
Christian Beck
Keyword(s):  
Experimental Data ◽  
Multiphase Flow ◽  
Gas Turbines ◽  
High Speed ◽  
Three Dimensional ◽  
Air Entrainment ◽  
Journal Bearings ◽  
Heavy Duty ◽  
Present Contribution ◽  
Two Phase

The traditional method for hydrodynamic journal bearing analysis usually applies the lubrication theory based on the Reynolds equation and suitable empirical modifications to cover turbulence, heat transfer, and cavitation. In cases of complex bearing geometries for steam and heavy-duty gas turbines this approach has its obvious restrictions in regard to detail flow recirculation, mixing, mass balance, and filling level phenomena. These limitations could be circumvented by applying a computational fluid dynamics (CFD) approach resting closer to the fundamental physical laws. The present contribution reports about the state of the art of such a fully three-dimensional multiphase-flow CFD approach including cavitation and air entrainment for high-speed turbo-machinery journal bearings. It has been developed and validated using experimental data. Due to the high ambient shear rates in bearings, the multiphase-flow model for journal bearings requires substantial modifications in comparison to common two-phase flow simulations. Based on experimental data, it is found, that particular cavitation phenomena are essential for the understanding of steam and heavy-duty type gas turbine journal bearings.

Theoretical and Experimental Investigation of Pipe Wall Thinning Detection Using Guided Waves

2008 ◽  
Author(s):  
Isoharu Nishiguchi ◽  
Fumitoshi Sakata ◽  
Seiichi Hamada
Keyword(s):  
Experimental Data ◽  
Power Generation ◽  
Experimental Investigation ◽  
Reflection Coefficient ◽  
Guided Waves ◽  
Pipe Wall ◽  
Thermal Power ◽  
Wall Thinning ◽  
Torsional Waves ◽  
Simplified Method

A method to investigate pipe wall thinning using guided waves has been developed for pipes in thermal power generation facilities. In this paper, the reflection coefficient and the transmission coefficient are derived for the torsional waves which propagate along a pipe and a simplified method to predict the waveform is proposed. The predictions of the waveforms by the FEM and a simplified method based on the reflection of torsional waves are also examined by comparing with experimental data.

Effects of vessel baffling on the drawdown of floating solids

2009 ◽  
Vol 63 (2) ◽  
Author(s):  
Joanna Karcz ◽  
Beata Mackiewicz
Keyword(s):  
Experimental Data ◽  
Power Consumption ◽  
Strain Gauge ◽  
High Speed ◽  
Vessel Diameter ◽  
Rushton Turbine ◽  
Agitated Vessel ◽  
Dimensionless Equation ◽  
Inner Diameter ◽  
Floating Particles

AbstractThe effects of baffling of an agitated vessel on the production of floating particles suspension are presented in this paper. Critical agitator speed, needed for particles dispersion in a liquid agitated in a vessel of the inner diameter of 0.295 m, was determined. The just drawdown agitator speeds were defined analogously to the Zwietering criterion. Specific agitation energy was calculated from the power consumption experimental data obtained by means of the strain gauge method. The experiments were carried out for twelve configurations of the baffles differing in number, length and their arrangement in the vessels. The following high-speed impellers were used: up- and downpumping six blade pitched blade turbines, Rushton turbine, and propeller. The impeller was located in the vessel in the height equal to two-thirds or one-third of the vessel diameter from the bottom of the vessel. The results were described in the form of a dimensionless equation.

Loss Generation in Transonic Turbine Blading

2017 ◽  
Author(s):  
Penghao Duan ◽  
Choon S. Tan ◽  
Andrew Scribner ◽  
Anthony Malandra
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Mach Number ◽  
High Speed ◽  
Turbine Blades ◽  
Surface Boundary ◽  
Loss Model ◽  
Exit Mach Number ◽  
Loss Characteristic ◽  
Shock Loss

The measured loss characteristic in a high-speed cascade tunnel of two turbine blades of different designs showed distinctly different trend with exit Mach number ranging from 0.8 to 1.4. Assessments using steady RANS computation of the flow in the two turbine blades, complemented with control volume analyses and loss modelling, elucidate why the measured loss characteristic looks the way it is. The loss model categorizes the total loss in terms of boundary layer loss, trailing edge loss and shock loss; it yields results in good agreement with the experimental data as well as steady RANS computed results. Thus RANS is an adequate tool for determining the loss variations with exit isentropic Mach number and the loss model serves as an effective tool to interpret both the computational and experimental data. The measured loss plateau in Blade 1 for exit Mach number of 1 to 1.4 is due to a balance between a decrease of blade surface boundary layer loss and an increase in the attendant shock loss with Mach number; this plateau is absent in Blade 2 due to a greater rate in shock loss increase than the corresponding decrease in boundary layer loss. For exit Mach number from 0.85 to 1, the higher loss associated with shock system in Blade 1 is due to the larger divergent angle downstream of the throat than that in Blade 2. However when exit Mach number is between 1.00 and 1.30, Blade 2 has higher shock loss. For exit Mach number above around 1.4, the shock loss for the two blades is similar as the flow downstream of the throat is completely supersonic. In the transonic to supersonic flow regime, the turbine design can be tailored to yield a shock pattern the loss of which can be mitigated in near equal amount of that from the boundary layer with increasing exit Mach number, hence yielding a loss plateau in transonic-supersonic regime.

Measured Film Cooling Effectiveness of Three Multihole Patterns

2005 ◽  
Vol 128 (2) ◽  
pp. 192-197 ◽  
Author(s):  
Yuzhen Lin ◽  
Bo Song ◽  
Bin Li ◽  
Gaoen Liu
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Film Cooling ◽  
Row Spacing ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Analogy Method ◽  
Blowing Ratio ◽  
The Third ◽  
Coolant Injection

As an advanced cooling scheme to meet increasingly stringent combustor cooling requirements, multihole film cooling has received considerable attention. Experimental data of this cooling scheme are limited in the open literature in terms of different hole patterns and blowing ratios. The heat-mass transfer analogy method was employed to measure adiabatic film cooling effectiveness of three multihole patterns. Three hole patterns differed in streamwise row spacing (S), spanwise hole pitch (P), and hole inclination angle (α), with the first pattern S∕P=2 and α=30°, the second S∕P=1 and α=30°, and the third S∕P=2 and α=150°. Measurements were performed at different blow ratios (M=1-4). Streamwise coolant injection offers high cooling protection for downstream rows. Reverse coolant injection provides superior cooling protection for initial rows. The effect of blowing ratio on cooling effectiveness is small for streamwise injection but significant for reversion injection.

Study on Performance Optimization of Car Diesel Engine with VNT Based on One-Dimensional Simulation and Experimental Verification

2012 ◽  
Vol 155-156 ◽  
pp. 12-17 ◽  
Author(s):  
Lian Xu Wang ◽  
Da Wei Qu ◽  
Chang Qing Song ◽  
Ye Tian
Keyword(s):  
Experimental Data ◽  
Diesel Engine ◽  
Performance Optimization ◽  
High Speed ◽  
Turbine Blades ◽  
Simulation Software ◽  
Engine Operation ◽  
One Dimensional ◽  
Distribution Phase ◽  
Dimensional Simulation

To research the performance optimization of high speed car diesel engine，firstly according to the characteristic of car diesel engine with Variable Nozzle Turbocharger (VNT)， one-dimensional cycle model of the engine was established by using simulation software BOOST and validated by experimental data in this paper. The turbine blades’ opening corresponding to different speed was determined. Therefore the problem that the VNT surges at low engine speed and the inlet air flow is insufficient at high speed was solved. Based on the above model, this paper improved the efficiency of the engine by optimizing the compression ratio and the distribution phase of camshaft and then used the experimental data to check the simulation results. Meanwhile the fuel consumption and the possibility of the engine operation roughness decreased.

Study on Mathematical Model of High Speed Milling Force for Plastic Mold Steel 3Cr2Mo

2011 ◽  
Vol 291-294 ◽  
pp. 710-714
Author(s):  
Jun Min Xiao ◽  
Ying Xu
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
High Speed ◽  
High Hardness ◽  
Milling Force ◽  
High Speed Milling ◽  
Engineering Requirement ◽  
Practical Engineering ◽  
Cad Cam ◽  
Plastic Mold

Mold steel 3Cr2Mo has been used widely in manufacturing of plastic mold formed parts, owing to fine mechanical properties. However, it is also very difficult to cut mold formed parts of steel 3Cr2Mo due to high hardness. Ordinary NC cutting method of steel 3Cr2Mo is unable to relate to modern mold manufacturing due to bad cutting property, so it is extremely significant for improving cutting property of steel 3Cr2Mo to study the high speed milling technology. On the basis of improving the traditional cutting force formula, the mathematical model of high speed milling force for steel 3Cr2Mo was derived and solved by using the experimental data and constructing matrix equation based on MATLAB software. Comparing with experimental data, the error of mathematical model of high speed milling force could be controlled within 6 percent. Due to high precision the model of high speed milling force can meet practical engineering requirement and has great value in the fields of CAD/CAM/CAE.

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