Search

An accurate life prediction is important to the design of a high-speed rotary blade subjected to multilevel cyclic loads. The widely used Miner’s rule and uniaxial stress prediction method always deviate from actual life of the blade. A prediction method based on Chaboche’s nonlinear damage evolution model is utilized to predict the multilevel cyclic fatigue life of a compressor blade subjected to start-up centrifugal force and working aerodynamic force. Chaboche’s model is verified by comparing with experimental data of different materials. The blade life predicted by Chaboche’s rule and Miner’s rule are compared, and it is found that Miner’s rule might overestimate the blade life under the typical loading spectrum of start-up centrifugal force and working aerodynamic force. To study the impact of multiaxial stress state on the blade life, the life predicted by uniaxial stress method is compared to that predicted by multiaxial stress method, and it demonstrates that the multiaxial stress state of the blade should not be neglected. Finally, the crack propagation of the blade under multiaxial fatigue loads is simulated successfully by element deletion technique, which is conducted by translating Chaboche’s multiaxial model into a user defined UMAT program in ABAQUS. The predicted crack propagation life is compared with that predicted by an approximate Paris law method plate model. This research proves that the method to predict the blade life subjected to multilevel cyclic loads based on multiaxial Chaboche’s model could provide a valuable reference for engineering blade fatigue design.

The asymmetric pressure wave caused by Loss of Coolant Accident (LOCA) transients in multi-loop type Pressurized Water Reactor (PWR) leads to great shock to the reactor core barrel. The instantaneous shock causes severe damage to the reactor vessel structure integrity. In this paper, a new method for reactor core barrel instantaneous force calculation was proposed based on the widely accepted reactor system analysis code RELAP5. The reliability of RELAP5 code for pipe blow down and pressure wave propagation simulation was assessed against Edward pipe problem firstly. Then the typical three-loop PWR system model was established utilizing Symbolic Nuclear Analysis Package (SNAP) software and the small break LOCA scenarios with different break diameters and break locations were analyzed. The maximum instantaneous asymmetric force applied on the reactor core barrel was achieved under various break conditions, providing the boundary conditions for the core barrel stress distribution and deformation calculation. Results show that the cold leg break LOCA transient leads to great instantaneous asymmetric force, while the hot leg break LOCA transient has no obvious asymmetric force generated. The core barrel instantaneous stress concentration and deformation were discovered. This research could contribute to the reliability assessment of PWR core barrel under LOCA scenarios.

A systematic uncertainty analysis strategy based on stochastic sampling method is developed for best estimate analysis of the rod ejection accident in pressurized water reactor (PWR). Self-developed SAMP module and DAKOTA code are used to randomly sample the multigroup nuclear data, important neutronics and thermal-hydraulic (T-H) input parameters respectively. The 3D coupled reactor core model for Almaraz PWR plant is established using RELAP5/PARCS code system and the uncertainties of the core power, fuel enthalpy and local power distribution are obtained. The results indicate that the uncertainties of nuclear data and input parameters can result in large uncertainty on the results which should be carefully considered.

In this paper numerical simulation of PRHR HX and IRWST is demonstrated using FLUENT, and different numbers of C-type heat transfer tubes and coolant inlet temperature’s effects for the residual heat removal capacity of PRHR HX, IRWST thermal stratification and natural circulation have been researched. It’s found that at a constant flow area when heat transfer tubes’ number increased outlet temperature of PRHR HX is lower, the whole water temperature of IRWST is higher, thermal stratification and natural circulation are more oblivious. At a constant mass flow when inlet temperature of PRHR HX increased, inlet flow velocity increases and outlet temperature is higher. But on the other hand the cooling rate increases at the same time, the average temperature of IRWST is higher, the range of thermal stratification expands and the velocity of natural circulation increases.

The initiation events analysis and evaluation were the beginning of nuclear safety analysis and probabilistic safety assessment, and it was the key points of the nuclear safety analysis. The main methods of the initiation events analysis are reference to existing lists and reports, operating experience, project evaluation and logic diagrams analysis. Currently, the initiation events analysis method and experiences both focused on pressurized water reactor but there are no general theories for Fluoride Salt-Cooled High Temperature Reactor (FHR). With FHR’s research and development, the initiation events analysis and evaluation was increasingly important. Based on the FHR’s design, the theories and methods of initiation events analysis would be researched and developed. From the FHR’s design, the systems, subsystems and components are divided to identify the safety functions of them. Base on the safety functions, the logical analysis and accident analysis calculation method would be combined to study FHR’s initiation events. The theory of analysis would be developed and the analysis method system would be discussed. Finally, the preliminary initiation events list of FHR will be discussed and researched. The results would help TMSR’s reactor designs and nuclear safety analysis.

Cold airflow experiments on a small-scale burner model, as well as in situ experiments on a centrally fuel-rich swirl coal combustion burner were conducted. Measurements were taken from within a 300 MW e wall-fired pulverized-coal utility boiler installed with eight of centrally fuel-rich swirl coal combustion burners in the bottom row of the furnace during experiments. Various primary air ratios, flow characteristics, gas temperature and gas species concentrations in the burner region were measured. The results of these analyses show that with decreasing primary air ratio, the swirl intensity of air, divergence angles and maximum length and diameter of the central recirculation zone all increased, and the turbulence intensity of the jet flow peaked but decayed quickly. In the burner nozzle region, gas temperature, temperature gradient and CO concentration increased with decreasing primary air ratio, while O 2 and NO x concentration decreased. Different primary air ratios, the gas temperatures and gas species concentrations in the side-wall region varied slightly.

Due to the limits of reserves and price for the high rank coal, the low rank coal has been employed as fuel for power generation in China and will be eventually employed in the world. To burn low rank coal, centrally fuel-rich swirl coal combustion burner has been studied in Harbin Institute of Technology. This paper reviews and analyzes the major research results. The work has included both experiments and numerical simulation. The experiments were conducted using small-scale single-phase experimental equipment, a gas/particle two-phase test facility and 200- and 300-MWe wall-fired utility boilers. For the burner, the primary air and glass beads partially penetrate the central recirculation zone and are then deflected radially. At the center of the central recirculation zone, there is high particle volume flux and large particle size. For the burners the local mean CO concentrations, gas temperatures and temperature gradient are higher, and the mean concentrations of O2 and NOx in the jet flow direction in the burner region are lower. Moreover, the mean O2 concentration is higher and the gas temperature and mean CO concentration are lower in the side wall region. Centrally fuel-rich burners have been successfully used in 200- and 300-MWe wall-fired pulverized coal utility boilers.

A three-component particle-dynamics anemometer is used to measure, in the near-burner region, the influence of the outer secondary air vane angle on the gas/particle flow characteristics of a double swirl flow burner, in conjunction with a gas/particle two-phase test facility. Velocities, particle volume flux profiles and normalized particle number concentrations were obtained. For three different outer secondary air vane angles, annular recirculation zones formed only in the region of r/d = 0.3–0.6 at x/d = 0.1–0.3. With a decreasing outer secondary air vane angle, the peaks of (RMS) root mean square axial fluctuation velocities, radial mean velocities near the wall, RMS radial fluctuation velocities and tangential velocities all increased, and the recirculation increased slightly. There was a low particle volume flux in the central zone of the burner. At x/d = 0.1–1.0, the profiles of particle volume flux had two peaks in the secondary air flow zone and near the wall, and the two peaks increased as the outer secondary air vane angle decreased. In the section x/d = 0.1–0.5, the particle diameter in the central zone of the burner was always less than the particle diameter at other locations.

Measurements were taken for a 300 MWe wall-fired pulverized-coal utility boiler installed with eight centrally fuel rich swirl coal combustion burners in the bottom row of the furnace during experiments. For various outer secondary air vane angle settings, flow characteristics, gas temperature and gas species concentrations in the burner region were measured. The results show that with decreasing outer secondary air vane angle, the swirl intensity of air, divergence angles and maximum length and diameter of the central recirculation zone all increased; the turbulence intensity of the jet flow first increased and then quickly decreased. With decreasing outer secondary air vane angle, the rate of increase in the gas temperature in the early stage and the rate of decrease in the later stage increased along the jet flow direction. For outer secondary air vane angle of 25°, the O2 concentration along the jet flow direction in the burner region was low, and the CO concentration decreased with increasing outer s...

Measurements were performed on a 200 MWe, wall-fired, lignite utility boiler. For different overfire air (OFA) damper openings, the gas temperature, gas species concentration, coal burnout, release rates of components (C, H, and N), furnace temperature, and heat flux and boiler efficiency were measured. Cold air experiments for a single burner were conducted in the laboratory. The double-swirl flow pulverized-coal burner has two ring recirculation zones starting in the secondary air region in the burner. As the secondary air flow increases, the axial velocity of air flow increases, the maxima of radial velocity, tangential velocity and turbulence intensity all increase, and the swirl intensity of air flow and the size of recirculation zones increase slightly. In the central region of the burner, as the OFA damper opening widens, the gas temperature and CO concentration increase, while the O{sub 2} concentration, NOx concentration, coal burnout, and release rates of components (C, H, and N) decrease, and coal particles ignite earlier. In the secondary air region of the burner, the O{sub 2} concentration, NOx concentration, coal burnout, and release rates of components (C, H, and N) decrease, and the gas temperature and CO concentration vary slightly. In the sidewall region, the gasmore » temperature, O{sub 2} concentration, and NOx concentration decrease, while the CO concentration increases and the gas temperature varies slightly. The furnace temperature and heat flux in the main burning region decrease appreciably, but increase slightly in the burnout region. The NOx emission decreases from 1203.6 mg/m{sup 3} (6% O{sub 2}) for a damper opening of 0% to 511.7 mg/m{sup 3} (6% O{sub 2}) for a damper opening of 80% and the boiler efficiency decreases from 92.59 to 91.9%. 15 refs., 17 figs., 3 tabs.« less

The diagnosis for multiple faults is still a big challenge for monitoring and maintenance of rotating machinery. In this study, the blind source separation (BSS) technique is proposed to separate the vibrational features produced by several faults existing in a rotor. A statistic variable-based algorithm, decorrelation method, is employed to analyze the signals of the rotors with multi-faults, which are simulated by numerical and experimental methods. The separation results show that the typical feature components of the frequency spectrum of each fault are separated successfully. The investigation demonstrates that it is feasible and helpful to adopt BSS technique to diagnose the multi-faults of a rotor.

Computational fluid dynamics (CFD) has been applied to evaluate two NO x reducing schemes in a 100 MWe per hour (p/h) boiler that uses double volute burners without over-fire-air (OFA). The new schemes involve: a) changing the double volute burners for centrally fuel rich (CFR) burners, and b) using the OFA system in conjunction with a). In analyzing the results of these two schemes, various conclusions were drawn: 1) gas temperatures and related rise rates in the central zone of burners were higher, O2 and NO x concentrations were lower; and 2) cross-sectional gas temperature distributions through the burner centers in scheme employing b) is higher than that of original furnace set-up, and lower than that of scheme employing a). Comparing the b) scheme with those of the a) scheme and the original set-up, which is 277 mg/m3 (at 6% O2) at the furnace outlet, the peak value of NO x concentration has decreased 571 mg/m3 (67.4%) and 436 mg/m3 (61.2%), respectively.

Experiments with a small-scale cyclone burner used for burner enrichment in a down-fired pulverized-coal 300 MWe utility have been conducted on an air/particle test facility. Particle separating efficiency was obtained with different positions of an adjustable vane. Industrial experiments were performed on a full-scale boiler. The gas temperature distribution along the primary air and coal mixture flow, gas temperature distribution of the furnace, and gas components such as O2, CO, CO2 and NOX in the near-wall region were measured for the first time. The influence of the adjustable vane position on coal combustion in the furnace was determined. With the adjustable vanes at the nozzle, ignition of the primary air and pulverized-coal mixture was delayed and the gas temperature peak was above the burner arch, with high NOX emission. Raising the vanes can bring forward the ignition point but results in the fuel-rich flow being up ahead of time, leading to a rise in carbon content in fly ash and NOX emission.

A three-component particle-dynamics anemometer is used to measure, in the near-burner region, the influence of the particle bias in the primary air duct on the gas/particle flow characteristics for a centrally fuel rich swirl coal combustion burner, in conjunction with a gas/particle two-phase test facility. Velocities, particle volume flux profiles and normalized particle number concentrations were obtained. Compared with a common burner (a centrally fuel rich burner without a particle concentrator), the degree of penetration for the centrally fuel rich burner is higher, the residence time of particles in the central recirculation zone is longer and the central recirculation zone is larger. The particle volume flux and normalized particle number concentration for the centrally fuel rich burner are much larger near the chamber axis. The influence of gas/particle flow characteristics on combustion has been analyzed.

The system state trajectory, Poincare maps, largest Lyapunov exponents, frequency spectra and bifurcation diagrams were used to investigate the non-linear dynamic behaviors of a rotor-bearing-seal coupled system and to analyze the influence of the seal and bearing on the nonlinear characteristics of the rotor system. Various nonlinear phenomena in the rotor-bearing-seal system, such as periodic motion, double-periodic motion, multi-periodic motion and quasi-periodic motion were investigated. The results may contribute to a further understanding of the non-linear dynamics of the rotor-bearing-seal coupled system.

The rotor—bearing—seal system is simulated by a model consisting of the rotor, the bearing, the foundation, and the labyrinth seal. Governing equations are set up theoretically using the finite-element method. The equivalent model of the bearing—foundation support system is analysed. Forces from the bearing—foundation support and gas-excited forces in the labyrinth seal are imposed in the finite-element equations. Then an experimental rotor—bearing—seal device is designed and many tests are carried out. The Bode, orbit, and waterfall plots are all constructed from the experimental data. An experimental rotor system is studied using the developed equations. Theoretical results from the developed model are in agreement with the ones from the experiment. Analysis proves that although the gas-excited force in the labyrinth seal can improve the stable region of the rotor—bearing—seal system, it makes the rotor vibrate more violently and initiates destructive impacts within the rotor system when the rotor running speed reaches a certain level. Oil whirl and oil whip of journal bearings are found in both the theoretical calculation and the experiment.

A three-component particle-dynamics anemometer is used to measure the characteristics of two-phase gas/particle flows in the near-burner region for a centrally fuel rich swirl coal combustion burner using a gas/particle two-phase test facility. Velocities, mean particle diameters and particle-volume flux profiles were obtained. The primary air and glass beads partially penetrate the central recirculation zone and are then deflected radially. At the center of the central recirculation zone, the mean radial velocities and tangential velocities are low and a zone of high particle-volume flux and large particle size is formed. The influence of gas/particle flow characteristics on combustion is analyzed.

Measurements were performed in a 300-MWe wall-fired pulverized-coal utility boiler. Enhanced ignition-dual register (EI-DR) burners and centrally fuel rich (CFR) swirl coal combustion burners were installed in the bottom row of the furnace during experiments. Local mean concentrations of O2, CO, CO2 and NO x gas species, gas temperatures, and char burnout were determined in the region of the two types of burners. For centrally fuel rich swirl coal combustion burners, local mean CO concentrations, gas temperatures and the temperature gradient are higher and mean concentrations of O2 and NO x along the jet flow direction in the burner region are lower than for the enhanced ignition-dual register burners. Moreover, the mean O2 concentration is higher and the gas temperature and mean CO concentration are lower in the side wall region. For centrally fuel rich swirl coal combustion burners in the bottom row, the combustion efficiency of the boiler increases from 96.73% to 97.09%, and NO x emission decreases fro...

To investigate the effect of foundation excitation on the dynamical behavior of a turbocharger, a dynamic model of a turbocharger rotor-bearing system is established which includes the engine’s foundation excitation and nonlinear lubricant force. The rotor vibration response of eccentricity is simulated by numerical calculation. The bifurcation and chaos behaviors of nonlinear rotor dynamics with various rotational speeds are studied. The results obtained by numerical simulation show that the differences of dynamic behavior between the turbocharger rotor systems with/without foundation excitation are obviously. With the foundation excitation, the dynamic behavior of rotor becomes more complicated, and develops into chaos state at a very low rotational speed.

A Printing Pressure expectation system based on fuzzy inference has been installed in a liquid crystal display panel (LCD) production plant to solve problems in determining the printer printing pressure in real-world LCD production, in which the recognition of printing pressure conditions and control are very important and difficult, influencing product quality. This is usually done conducted by skilled engineers, whose performance depends on tacit knowledge. We propose using fuzzy inference to solve this problem. Printing area images are observed with cameras and abstract features extracted using image processing. System output is the status of printing pressure, divided into excessive pressure (EP), good pressure (GP), and low pressure (LP). Based on abstract features, the state is calculated using fuzzy membership functions. Shapes of membership functions are determined based on sampled glass obtained in actual LCD production line. Experiments are conducted using 2000 samples of glass printed using actual printers, or which results are compared to those of skilled engineers. We found that the proposed system yields quality higher than that of skilled engineers. We installed our system on an actual production line, where it is expected to increase product quality and production speed while and cutting production costs.

The non-linear dynamic behaviors of a rotor–bearing–seal coupled system are investigated. The influence of parameters, such as the rotation speed, seal clearance and eccentricity of rotor are analyzed by state trajectory, Poincare maps, frequency spectra and bifurcation diagrams. Various non-linear phenomena compressing periodic and quasi-periodic motion in the rotor–bearing–seal system are investigated. The comparison between the analytical results of the numerical and the experimental findings shows that the predictive results agree with the experimental results. It is indicated that this study may contribute to a further understanding of the non-linear dynamics of such a rotor–bearing–seal coupled system.

The coupled torsional-lateral model of the rotor system is set up and governing equations are derived using the Lagrange approach with six degrees of freedom. The gyroscopic effect and gravity are included. Two kinds of unbalance, namely static unbalance and dynamic unbalance, are considered in the rotor system. Torsional and lateral motions are subjected to external excitations. Through numerical simulation, the developed model is used and the coupled torsional-lateral vibrations of the unbalanced rotor system under external excitations are investigated. Some new phenomena are found and discussed.

Seal and bearing characteristic is an important factor affecting the performance of the rotor system. The non-linear dynamic behaviours of a rotor-bearing-seal coupled system are investigated. Dynamic trajectories, Poincaré maps, largest Lyapunov exponents, frequency spectra, and bifurcation diagrams which are applied to analyse the features of the rotor-bearing-seal system in various parameters. Various non-linear phenomena in the rotor-bearing-seal system, such as periodic motion, double-periodic motion, multi-periodic, and quasi-periodic motion are investigated. The results of this study may contribute to a further understanding of the non-linear dynamics of such a rotor-bearing-seal coupled system.

The non-linear dynamic behaviors of a rotor-bearing-seal coupled system are investigated by using Muszynska’s non-linear seal fluid dynamic force model and non-linear oil film force, and the result from the numerical analysis is in agreement with the one from the experiment. The bifurcation of the coupled system is analyzed under different operating conditions. It is indicated that the dynamic behavior of the rotor-bearing-seal system depends on the rotation speed, seal clearance and seal pressure of the rotor-bearing-seal system. The system state trajectory, Poincare maps, frequency spectra and bifurcation diagrams are constructed to analyze the dynamic behavior of the rotor center. Various non-linear phenomena in the coupled system, such as periodic motion and quasi-periodic motion are investigated. The results show that the system has the potential for chaotic motion. The study may contribute to a further understanding of the non-linear dynamics of such a rotor-bearing-seal coupled system.

A nonlinear Continuum Damage Mechanics model (CDM) is proposed to assess the low cycle fatigue life of a steam turbine rotor, in which the effects of mean stress are taken into account and the damage is accumulated nonlinearly. The model is applied to a 200 MW steam turbine under cold start and sliding parameter stop. The results are compared with those from the linear accumulation theory that is dominant in life assessment of steam turbine rotors at present. The comparison results show that the nonlinear CDM model describes the accumulation and development of damage better than the linear accumulation theory.

A three–component particle–dynamics anemometer is used to measure, in the near–burner region, the influence of the primary air ratio on the gas/particle two–phase characteristics for a centrally fuel rich swirl coal combustion burner, on a gas/particle two phase test facility. Velocities, particle volume flux profiles and particle relative number concentrations were obtained. With a low primary air ratio, the axial velocities for gas and particles on the chamber axis are always small and easily reach the negative, and the central recirculation zone is easily formed and much closer to the outlet of the burner. In each cross–section, in the radius range from R

Linear and nonlinear dynamics and stability of the rotor-bearing-seal system are investigated both theoretically and experimentally. First the system is modeled with the finite element method. The rotordynamic behavior of the journal bearing and the labyrinth seal are represented by eight linearized dynamic force coefficients. An experimental rotor-bearing-seal device is designed and tests are carried out. The experimental system is studied using the developed linear equations. Complex eigenvalues are solved. Corresponding critical speeds and logarithmic decrements to determine the thresholds of instability are calculated. Then the experimental rotor system is simplified as the Jeffcott rotor. The nonlinear oil-film forces are got under the short bearing theory and Muszynska nonlinear seal force model is used. Numerical method is utilized to solve the nonlinear governing equations. Bifurcation diagrams, Poincare´ maps, spectrum plots and rotor orbits are drawn to analyze various nonlinear phenomena and system unstable process. Theoretical results from the linear and nonlinear analysis are in good agreement with results from experiments. Conclusions are drawn and prove that this study will contribute to the further understanding of dynamics and stability of the rotor system with the fluid-induced forces from oil-film bearings and the seals.

Solder joint reliability (SJR) under drop impact is a big concern for hand-held device such as mobile phone and PDA. In the semiconductor industry, generally board level drop test is used to assess solder joint performance under drop impact. JEDEC published a standard on drop test which defines drop impact pulse and test board configuration, and thus when the standard is strictly followed SJR drop test carried out by different semiconductor component manufacturers can be compared. However when the JEDEC drop test board is used for package qualification, there are some limitations. Firstly, the JEDEC test board provided so many solder joint loading conditions which are sometimes not necessary because the main drop test indicator is the earliest drop test failure which is dominated by the worst loading condition. Secondly, so many loading conditions reduce the sample size of each loading condition when the data are statistically processed. Here we propose an alternative test board design with only one loading condition and sufficiently large sample size, which is more suitable for package qualification statistically. Except the board shape and size and package component layout, all other board design requirement strictly follows the JEDEC standard so that it can be easily implemented.

The nonlinear dynamic behavior of a rotor-bearing system is analyzed based on a continuum model. The finite element method is adopted in the analysis. Emphasis is given on the so called “Oil-Whirl phenomena” which might lead to the failure of the rotor system. The dynamic response of the system in unbalanced condition is approached by direct integration method and mode superposition method, it is found that a typical “Oil-Whirl phenomenon” is successfully produced. Furthermore, the bifurcation behavior of the Oil-Whirl phenomenon that is much concerned in recent nonlinear dynamics research is analyzed. The rotor-bearing system is also examined by the simple discrete model. Significant differences are found between these two models. It is suggested that a careful examination should be made in modeling such nonlinear dynamic behavior of the rotor system.

Electro-hydraulic servo valve is a typical complicated multi-domain system constituted by mechanical, electric, hydraulic and magnetic components, which is widely used in electro-hydraulic servo systems such as construction machinery, heavy equipment, weapon and so forth. The traditional method of modeling and simulation of servo valve is based on block diagram or signal flow, which cannot describe the servo valve system from components level nor be used in modeling and simulation of overall servo systems. In the procedure of traditional method, computational causality must be involved in modeling of servo valve, which is inconvenient to execute modification on components or parameters. Modelica is an object-oriented modeling language which is suited for large, complex, heterogeneous and multi-domain systems. The key features of Modelica are multi-domain, object-oriented and non-causal, which are suitable for modeling of servo valve and make the model readable, reusable, and easy to modify. The simulation results show similar curves with traditional method. This new servo valve modeling and simulation method can provide the engineers a more efficient way to design and optimize a servo valve and an overall servo system.