bluuebunny/crossref_metadata_2025 huggingface dataset:
A Pragmatic Optimization of Axial Stack-Radial Passive Magnetic Bearings
Authors: Lijesh K. P. , Doddamani Mrityunjay , Bekinal S. I.
Published: September 2017

Passive magnetic bearing's (PMB) adaptability for both lower and higher speed applications demands detailed and critical analysis of design, performance optimization, and manufacturability. Optimization techniques for stacked PMB published in recent past are less accurate with respect to complete optimum solution. In this context, the present work deals with a pragmatic optimization of axially stacked PMBs for the maximum radial load using three-dimensional (3D) equations. Optimization for three different PMB configurations, monolithic, conventional, and rotational magnetized direction (RMD), is presented based on the constraints, constants, and bounds of the dimensions obtained from published literature. Further, to assist the designers, equations to estimate the mean radius and clearance being crucial parameters are provided for the given axial length and outer radius of the stator with the objective of achieving maximum load-carrying capacity. A comparison of the load-carrying capacity of conventional stacked PMB using the proposed equation with the equation provided in literature is compared. Finally, effectiveness of the proposed pragmatic optimization technique is demonstrated by analyzing three examples with reference to available literature.
The Oriented Spray Cooling System for Supplementing Cooling Lakes
Authors: Bowman Charles F.
Published: September 2017

With ever-increasing ambient temperatures many electric power plants that employ cooling lakes to reject their waste heat into the environment are struggling to maintain reasonable turbine backpressures during the hot summer months when electric load demand is often the greatest. Some consider adding mechanical draft cooling towers (MDCT) to further cool the condenser circulating water (CCW) prior to entering the main condenser, but the additional auxiliary power required to drive MDCT fans often consume the additional generator output resulting from the lower backpressure. Spray ponds offer significant advantages over MDCT including superior simplicity and operability, lower power requirements, and lower capital and maintenance costs. The Oriented Spray Cooling System (OSCS) is an evolutionary spray pond design. Unlike a conventional spray pond in which spray nozzles are arranged in a flat bed and spray upward, blocking the ambient air flow to the spray region as it travels down to the pond below, the OSCS nozzles are mounted on spray trees arranged in a circle and are tilted at an angle oriented towards the center of the circle. As a result, the water droplets drag air into the spray region while the warm air concentrated in the center of the circle rises. Both of these effects work together to increase air flow through the spray region. Increased air flow reduces the local wet-bulb temperature (LWBT) of the air in the spray pattern, promoting heat transfer and more efficient cooling. During the late 1970’s the author developed a purely analytical model to predict the thermal performance of the OSCS which was successfully compared with the OSCS at the Columbia Generating Station (CGS) in the mid 1980’s. This paper describes how the OSCS may be employed to supplement the cooling capacity of an existing cooling lake to reduce the temperature of the CCW prior to entering a power plant, resulting in lower main condenser pressures and more net plant output.
Numerical Analysis of Mild Combustion Regimes Under Air and Oxyfuel Conditions
Authors: Lin Wang , Zhaohui Liu , Axelbaum Richard L.
Published: September 2017

Reactive structures of hot diluted methane counter-flow diffusion flames have been characterized under air-fuel and oxy-fuel combustion condition, by using a standard OPPDIF code with a WSGGM model and a validated detail chemical mechanism. The result shows the gaseous radiation makes the peak temperature be lower and the distributions of temperature change greatly.

Characteristic of vanishing of pyrolytic region and increasing of thickness of heat release zones are investigated in detail. The reason for these is the overlap of zones for the positive heat release and the negative heat release. Meanwhile, the combustion regions are established based on Xf –Tf –ΔT sketch map. The results show that MILD combustion is easier to be achieved under oxy-fuel conditions but it is also easier to blown off.

Moreover, reaction pathways for feedback combustion and MILD combustion under both air- and oxy-fuel conditions are analyzed. The chemical reaction rate decreases one order of magnitude under MILD combustion. Also, the decreasing of the production of OH and H and the addition of CO2 makes the C1 branch the C2 branch changes greatly under both conditions for MILD combustion.
Pilot Experimental Study of New Urea Hydrolysis for DeNOx in Coal Plant
Authors: Xiaofeng Xiang
Published: September 2017

Based on the domestically developed urea hydrolysis reactor and urea hydrolysis ammonia process, a pilot test of urea hydrolysis was established with 10kg/h ammonia production for the flue gas denitration reductant, to reduce pollution of NOx emission from coal plant and avoid the environmental risk of liquid ammonia.The results show that urea hydrolysis reaction rate was controlled by the temperature monotonically. Steam consumption increases with the increase of pressure, especially when pressure is greater than 0.6 MPa and bring about lower economy. The higher feed concentration, the lower energy loss for the water latent heat of vaporization, and the lower operation cost of device. The maximum ammonia production is 16 kg/h, the hydrolysis conversion is greater than 98%, and the ammonia mass fraction of product gas is 22.6–34% (volume fraction of 28.5–48.0%) during the tests, at the feed concentration of 40–60%, the operating pressure and temperature of 0.6MPa and 160°C.
Advanced Power Plant Concept With Application of Exhaust CO2 to Liquid Fuel Production
Authors: Chudnovsky B. , Levin L. , Talanker A. , Kunin A. , Cohen J. , Harpaz R. , Karni J.
Published: September 2017

Today there is a growing concern about the ramifications of global warming resulting from the use of fossil fuels and the associated carbon dioxide emissions. Oxy-fuel combustion is a promising response to this issue, since the product of the combustion is a CO2 rich flue gas, which requires no further separation from other emission gases and thus can be sequestrated, or utilized.

Here we present an analysis of a novel technology for combining oxy-fuel combustion with utilization of the CO2 rich flue gas for syntetic fuel production. The technology concept involves a new method of using concentrated solar energy for the dissociation of carbon dioxide (CO2) to carbon monoxide (CO) and oxygen (O2). Simultaneously, the same device can dissociate water (H2O) to hydrogen (H2) and oxygen (O2). The CO, or the mixture of CO and H2 (called Syngas), can then be used as a gaseous fuel (e.g. in power plants), or converted to a liquid fuel (e.g. methanol), which is relatively easy to store and transport, and can be used in motor vehicles and electricity generation facilities. The oxygen produced in the process can be used in oxy-fuel combustion or other advanced combustion methods in power plants.

In this study it is assumed that a typical sub-critical, 575 MW, coal firing power plant is converted to oxy-fuel combustion. The flue gases from that power plant are then used as raw material for fuel production. The aim of the study is to estimate the optimal conceptual design of a power generation plant, including liquid/gaseous fuel generation facility.

In the present study we used a series of special models for simulating the heat balance, heat transfer, performance and emissions of an oxy-fuel converted utility boiler. We also employed cycle simulation software that facilitates the optimization of an electricity generation plant with CO2 conversion to liquid fuel and usage of the fuel produced from CO2 for additional electricity production.

The simulation results show that the amount of fuel produced, additional power generated and power station self consumption may be changed over a wide range, depending on the size of the solar field, which provides the energy for the liquid fuel production.

The paper includes an overview of some of the key technical considerations of the new concept of CO2 conversion to fuel. Based on the obtained results it may be concluded that the methodology presented in this study is an attractive option for CO2 emission reduction, which can be implemented in existing and/or new power generation units. The technology proposed in this paper is not indented as an alternative for replacing coal combustion with natural gas, however may be used effectively with oxy-fuel combustion of either coal or natural gas.
Development of a Durable Vapor Phase Deposited Superhydrophobic Coating for Steam Cycle Power Generation Condenser Tubes
Authors: Duron Christopher M. , Zhong Jie , David Allan E. , Ashurst William R. , Bhavnani Sushil H. , Morris Jacob R. , Bates Andrew C.
Published: September 2017

The condenser performance benefits afforded by dropwise condensation have long been unattainable in steam cycle power plant condensers due to the unavailability of durable and long lasting wetting inhibiting surface treatments. However, recent work in superhydrophobic coating technology shows promise that durable coatings appropriate for use on condenser tubes in steam cycle power generation systems may soon become a reality. This work presents a nano-scale, vapor phase deposited superhydrophobic coating with improved durability comprised of several layers of rough alumina nano-particles and catalyzed silica with a finishing layer of perfluorinated silane. This coating was applied to solid, hemi-cylindrical test surfaces fabricated from several common condenser tube materials used in power generation system condensers: Titanium, Admiralty brass, Cupronickel, and Sea Cure stainless steel condenser tube materials as well as 304 stainless steel stock. The development evolution of the coating and its effect on condensation behavior on the above materials are presented. Results show that the performance enhancement, measured in rate of heat transfer spikes corresponding to condensate roll-off events, was best for the titanium surface which produced 64% more events than the next most active material when coated using the most durable surface treatment tested in this work.
Risk Analysis of Power-Gen Gas Turbines With GADS Outage Data
Authors: Zhou Bin
Published: September 2017

According to FM Global proprietary data, power-gen gas turbine losses have consistently represented a dominant share of the overall equipment-based loss value over the past decade. Effective assessment of loss exposure or risk related to gas turbines has become and will continue to be a critical but challenging task for property insurers and their clients. Such systematic gas turbine risk assessment is a necessary step to develop strategies for turbine risk mitigation and loss prevention. This paper presents a study of outage data from the Generating Availability Data System (GADS) by the North American Electric Reliability Corporation (NERC). The risk of forced outages in turbines was evaluated in terms of outage days and number of outages per unit-year. In order to understand the drivers of the forced outages, the influence of variables including turbine age, capacity, type, loading characteristic, and event cause codes were analyzed by grouping the outage events based on the chosen values (or ranges of values) of these variables. A list of major findings related to the effect of these variables on the risk of forced outage is discussed.
The Enlightenment of Updated Development of the USC Coal Fired Units
Authors: Wenhao Ji , Daolin Li , Xingsheng Hu , Peng Wan
Published: September 2017

An comparison of technical specification and updated operation results between two USC coal fired boilers namely RDK-8, Germany and WGQ-3, China has been considered under the global scenario related to the variation of industrial production structure, power demand cut down, more stringent carbon dioxide depression and larger quantity of renewable units engaged into the grid, in this respect a discussion and analysis have been carried out subjected to low grade heat recovering and harmful emission prevention from boiler flue gas and introduction carbon harmful emission prevention from boiler flue gas and their multiple benefits on energy saving and environmental protection, moreover the experience and gains in the field of flue gas heat recovering and mitigating pollution, including the proprietary technique (WGGH) by SPERI are briefly stated, thereby a conclusion of enlightenment for further development of these units is mentioned.
A GPSS Based on Active Power Signal and its Effective Frequency Boundary
Authors: Li Yanghai , Yang Tao
Published: September 2017

Low frequency oscillation is one of the most important factors that restrict the tie-line power flow of network. Its effective suppression is necessary to ensure safety and stability of the power system. The conventional power system stabilizer (PSS) is still insufficient in suppressing consider the frequency range and types of oscillation, so it is necessary to study the auxiliary suppression of the oscillation from the turbine side by using the electro-mechanical coupling theory. In this paper, a governorside power system stabilizer (GPSS) based on active power signal is designed, and its working principle, system structure and parameter setting method are introduced, the effective response frequency boundary of oscillation is also analyzed. Theoretical analysis and simulation results show that this GPSS can suppress in the whole frequency range of low frequency oscillation, and it is suitable as an auxiliary means of low frequency oscillation suppression. (CSPE)
Position Control of the Hydraulically Actuated Francis Turbine Inlet Guide Vane
Authors: Venkaiah Paladugu , Sarkar Bikash Kr.
Published: September 2017

Development of the renewable source of energy has become an area of interest due to increasing power demand and fixed fossil fuels in the universe. To increase efficiency of the renewable source of energy like, hydro power become important. In the present work, adaptive feedforward fuzzy PID controller has been developed for position control of the electrohydraulic actuation turbine IGV system. Electrohydraulic turbine governing systems are superior to the electromechanical governing system due to the high power availability, very good controllability, self lubrication property etc. NACA 0012 aerofoil blade configuration has been considered for the turbine IGV system due to the less lift force which lead to the less effort required to governing action. Low cost proportional valve control electrohydraulic system configuration has been considered. Simulation study has been carried in Matlab Simulink environment. The system IGV position control has been studied for step, sinusoidal and arbitrary position demand.
Energy Analysis of a Lignite-Fueled Power Plant With a Two-Stage Predrying System
Authors: Zhu Xin , Wang Chang’an , Tang Chunli , Che Defu
Published: September 2017

Performance of lignite-fueled power plants can be improved by predrying the lignite and it is influenced by the characteristics of drying heat source. Heat source for lignite predrying in power plants can be high-temperature flue gas, boiler exhaust gas and extraction steam. Nevertheless, balance point among drying safety, lignite drying degree and drying thermal economy cannot be located using single drying heat source. In this study, a lignite-fueled power plant with a two-stage drying system was proposed. The drying system mainly contains two fluidized bed dryers — the first stage dryer and the second stage dryer. Boiler exhaust gas and extraction steam supply the heat, respectively. The proposed power plant can attain higher lignite drying degree than the power plant in which only boiler exhaust was employed. The new power plant also features higher overall efficiency for the same lignite drying degree compared with extraction steam drying power plant..
Designing of Micro Gravitational Vortex Turbine’s Vortex Pool
Authors: Rehman Wajiha , Ijaz Masooma , Munir Asma
Published: September 2017

Water is one of the major sources of renewable energy and many hydropower plants are working across the world but they require specific values of head and flow rate for their operation and optimum results. There are many sites where limited head and flow rate is available but these resources cannot be exploited due to inefficient technologies. Gravitational vortex turbine (GVT) is a novel technology that is suitable for micro-level power production where low head and flow rate is available. It consists of two main parts: vortex pool for vortex generation and turbine blades. This paper focuses on parametrical analysis of GVT to determine the geometrical characteristics which gives the best performance. These parameters would address; effect of velocity and symmetry of vortex with the ratio of upper diameter of funnel (D) to outlet diameter (d), effect of the angle of rectangular inlet passage on the vortex formation. It will also analyze flow in rectangular passage with constant cross section vs. converging cross section. All of these parameters have major impact on the velocity and symmetry of flow. Results show that outlet of the funnel should be 40% of the upper diameter while highest velocity was achieved when rectangular passage was at 60 degrees with pre-rotational plate at 30 degrees.
A Theoretical and Experimental Study of HFE-7000 in a Small Scale Solar Organic Rankine Cycle As a Thermofluid
Authors: Helvaci Huseyin Utku , Khan Zulfiqar Ahmad
Published: September 2017

Renewable energy technologies and sources have been playing a key role in reducing CO2 emissions and its footprint. Solar energy which is one of the major renewable energy sources can be utilized by means of solar Photovoltaic (PV) or solar collectors. Concentrating solar collectors supply thermal energy from medium to high grade where as non-concentrating collectors (flat plate) delivers low-grade thermal energy. The use of thermofluids with boiling temperatures lower than water, allows the operation of low grade solar thermal systems on an Organic Rankine Cycle (ORC) to generate both mechanical and heat energy. At the same time, the selection of an appropriate thermofluid is an important process and has a significant effect both on the system performance and the environment. Hydrofluoroethers (HFEs) are non-ozone depleting substances and they have relatively low global warming potential (GWP). In this study, a solar ORC is designed and commissioned to use HFE 7000 as a thermofluid. The proposed system consists of a flat-plate solar collector, a vane expander, a condenser and a pump where the collector and the expander are used as the heat source and prime mover of the cycle respectively. The performance of the system is determined through energy analysis. Then, a mathematical model of the cycle is developed to perform the simulations using HFE-7000 at various expander pressure values. Experimental data indicates that the efficiency and the net mechanical work output of the cycle were found to be 3.81% and 135.96 W respectively. The simulation results show that increasing the pressure ratio of the cycle decreased the amount of the heat that is transferred to HFE 7000 in the collector due to the increased heat loss from the collector to the environment. Furthermore, the net output of the system followed a linear augmentation as the pressure ratio of the system increased. In conclusion, both the experimental and theoretical research indicates that HFE 7000 offers a viable alternative to be used efficiently in small scale solar ORCs to generate mechanical and heat energy.
Investigation of Thermal Conductivity Variation of Biomass Products With Moisture
Authors: Dikici Birce , Narasimha Parvesh R. B. , Kamdar Shruti D.
Published: September 2017

The aim of this paper is to investigate the thermal conductivity of various biomass products and investigate the thermal conductivity when moisture is added. In this study, the biomass used was seeds from Bermuda grass and a mix of wildflowers (e.g. Lupine, flax, Coreopsis and Shasta daisy).

Thermal diffusivity is calculated with a transient, one-dimensional conduction experiment. The experiments on aluminum is performed to test the experimental test setup to ensure the accuracy of the technique. Before obtaining the biomass thermal conductivity tests, the actual thermal conductivity values are obtained with the C-Therm TCi Thermal Conductivity Analyzer and the tests are carried out and compared with these values. Next, moisture is infused into biomass samples by addition of water from 10% to 30% with increments of 5%. An increase in thermal conductivity with moisture is observed for both biomass samples and the results are presented. In our tests, the moisture increased the thermal conductivity about 78% for Bermuda grass seed and 122% for Wild Flower seed.
Creep Damage Assessment of Notched Material Made of a Solidification Control Ni-Base Superalloy Using the EBSD Method
Authors: Kobayashi Daisuke , Takeuchi Tsutomu , Nakabeppu Katsushi
Published: September 2017

Changes in misorientation with deformation were measured by various misorientation analysis methods using the electron backscattered diffraction (EBSD) method, and quantitative assessments were attempted to estimate the amount of strain or damage. Misorientations were correlated with macroscopic plastic or creep strains for comparative well-strained materials such as austenitic stainless steels.

Ni-base superalloys used for components requiring high temperature strength such as gas turbine blades, have low ductility with precipitation of the γ’ phase in grains, therefore the change of crystal orientation was considered to be extremely suppressed in comparison with austenitic stainless steels. In addition, it was anticipated that the extremely large grains of Ni-base superalloys made it difficult to properly assess the damage as misorientation. However, with the current advances in the EBSD acquisition systems in conjunction with scanning electron microscopy, it has become possible to make unprecedented resolved measurements of the local crystal structure distribution at a millimeter scale.

In particular, in order to assess the damage of gas turbine blades, the complex blade inner cooling system complicates the distribution of temperatures and stresses in the blades, which implies that it is required to assess the influence of geometry at stress concentrated regions in addition to the condition of temperatures, stresses and creep fatigue wave forms.

To date, in the case of the conventional casting material or the same geometry notched specimen of the directionally solidified (DS) superalloy, the average misorientation which means the grain reference orientation deviation (GROD) within grains in a certain predetermined evaluation area including the notch increases linearly up to the initiation of creep cracks regardless of the testing temperatures, strain rates and the effect of fatigue under the creep dominant condition. However, the different notch geometry of the DS superalloy shows the different characteristics of the misorientation development.

This paper focuses on a misorientation parameter which can assess the creep crack initiation life independent of the geometry at stress concentrated regions. In order to assess the creep crack initiation life at various stress concentrated areas of the DS superalloy, the development of a unified life assessment method independent of the individual notch geometries was discussed. As a result of this study, a parameter dividing the GROD by the initial notch opening value, φ0, was proposed and it was confirmed that the proposed parameter, GROD/φ0 shows similar characteristics with the relative notch opening displacement (RNOD) curves which correspond to the local strain energy and the initiation of creep crack at the notch tip independent of the geometry at a stress concentrated region.
Experimental and Numerical Study of Cold Gas-Solid Flow Regimes in a Fluidized Bed Gasifier
Authors: Pylypenko Anton , Rastigejev Yevgenii , Wang Lijun , Shahbazi Abolghasem
Published: September 2017

The objective of this work is to analyze the dynamics and regimes of cold gas-solid flow in a biomass gasifier that is built at North Carolina Agricultural and Technical State University and to identify its corresponding ranges of operating conditions. The value of the minimum fluidization velocity Umf ≈ 8 cm/s has been found experimentally in a series of measurements of a pressure drop in the fluidized bed filled with Gledart type-B silica sand for the range of superficial gas velocities between 0 and 40 cm/s. To complement the experimental results, a set of three-dimensional numerical simulations of the isothermal gas-solid flow based on Eulerian-Eulerian approach has been performed. The analysis of the fluidization characteristics such as axial void fraction distributions has allowed us to evaluate the dependence of the bed expansion ratios from the flow superficial velocity. Good agreement between experimental and numerical results for the considered operating conditions of the gasifier has been observed.
Catalytic Combustion of Ultra-Low Heating Value Fuels Over 0.5%Pd/ZrO2/γ-Al2O3 Catalyst
Authors: Lv Xiaojing , Ding Xiaoyi , Weng Yiwu
Published: September 2017

Catalytic combustion of ultra-low heat value fuel over 0.5%Pd/ZrO2/γ-Al2O3 was investigated to offer an opportunity for scientifically using such fuel sources. The experimental studies were performed using single fuel, synthetic mixtures and different kinds of gasified biomasses, respectively. The effects of varied combustible gas concentration, inlet temperature and flow velocity on the conversion rate were also studied. The results showed that the ignition temperature of 1.4% CH4 over the catalyst used is lower 210 °C than that in the oxidation absence of catalyst. Conversion of CH4 increased with decreasing flow velocity and increasing combustible gas concentration. The influence of the flow velocity on the conversation is more significant when further increasing the CH4 concentration to a certain degree. The ignition temperature for CO, H2, CH4 decreased with increasing concentration, and the specific order is TCH4, TCO, TH2. The experimental data showed that the influence of H2 is very obvious for CH4 combustion-supporting character by adding different concentration of H2. Among the experiments of three kinds of gasified biomasses, the catalytic combustion characteristics of wood chip gas is best, followed by grape seed gas and cotton wood gas. These studies would provide the experimental analysis and technical support for catalytic combustion technology application in ultra-low heat value fuel.
Experimental Study of Heat Transfer and Resistance Characteristics of Single H-Type and Double H-Type Finned Tubes
Authors: Wei Wei , Sun Fengzhong , Shi Yuetao , Ma Lei , Liu Jiayou
Published: September 2017

There are various finned tube heat exchanges with diverse thermo-flow performance being widely applied in the power plants. Wherein, the H-type finned tubes are widely used in the economizer to improve the waste heat utilization efficiency of the coal fired boiler. The experimental studies regarding the heat transfer and resistance characteristics of single H-type and double H-type finned tubes have obtained the thermo-flow performances under different conditions. In addition, the test facility of double channels is specially designed to ensure the test accuracy. Correlations for Euler number Eu, Nusselt number Nu and Performance evaluation index Pec with Reynolds number Re are presented by analyzing the thermo-flow performances of the used bundles. The results show that the single H-type finned tube performs better heat transfer characteristic and relatively worse resistance characteristic than the double H-type finned tube. Consequently, the double H-type finned tube is recommended in the practical application considering the higher manufacturing installation efficiency. (CSPE)
The Interaction Effect Study of Ash Deposition and Acid Condensation on Low-Temperature Heat Transfer Surface in Boiler Flue Gas
Authors: Ma Lei , Sun Fengzhong , Wei Wei , Liu Jiayou , Shi Yuetao
Published: September 2017

The ash deposition on low-temperature heat transfer surface is a key factor that deteriorates the heat transfer performance and leads to corrosion in the low pressure economizer. In the low temperature flue gas, ash deposition is closely related with acid condensation. The sulfuric acid vapor and water vapor contained in the flue gas will condense on heat transfer surface under low flue temperature, which will aggravate ash deposition. In order to evaluate the influence factors of ash deposition on low-temperature heat transfer surface, a laboratory experiment is carried out in this paper. The acid concentration of flue gas, the ash content, the ash component, the flue temperature and the temperature of heat transfer surface are considered to be the most important influence factors on ash deposition characteristics. The viscosity of ash deposition samples on the outer wall of the double-pipe is measured to describe ash deposition characteristics. The fouling factor is calculated. Meanwhile, the scanning electron microscope SEM is used to the analysis of ash samples obtained from the outer wall of the double-pipe. As conclusion, the changing regulation of viscosity of ash deposition on low-temperature heat transfer surface is obtained. (CSPE)
Axial Flow Compressor Real-Time Tip Clearance Analysis and Experimental Verification
Authors: Cheng Lu , Zhao Shizhi , Liu Weibing , Ai Song , Fan Xiaoping
Published: September 2017

The tip clearance of the compressor has always been a key part in both the design and operation of gas turbine. Surge margin and aerodynamic performance of the compressor will be affected if the tip clearance is too large, while risk of rubbing between the blades and casing will arise if the tip clearance is too small. Generally speaking, the calculation and analysis of tip clearance under stable design condition is relatively easy, because the metal temperature field of both rotor and stator components that significantly affect the tip clearance is in stable condition at that time. However, the transient tip clearance under start-up and shut-down condition is difficult to be calculated and analyzed, due to the fact that both the aerodynamic parameters and metal temperature field are instable, and complicated heat-exchange occurs between the metal components and gas.

In this paper, the transient deformation of both rotor and stator components of compressor of a certain gas turbine is analyzed in detail by using thermo-solid coupling analysis technology, finally obtained real-time tip clearance. The non-contact measurement technology is used to measure the tip clearance during operation of the unit. The experimental result indicates that the real-time tip clearance value obtained by the calculation method in the paper is in a very good agreement with the measured value. In addition, both the analysis and experimental results show that the moment of smallest tip clearance usually happens at shut-down progress and the influence of tip clearance must be considered when designing unit’s running curve.
Exergoenvironmental Evaluation for a Coal-Fired Power Plant of Near-Zero Air Pollutant Emission
Authors: Hong Xiliang , Chen Jianhong , Sheng Deren , Li Wei
Published: September 2017

Owing to the growing environmental concerns, super-critical and ultra-supercritical coal-fired power plants dominate the electricity generation with the demand of near-zero air pollutant emission in China. Therefore, it is highly expected to assess the environmental impact and optimize the design at global and local levels. Exergoenvironmental analysis is a valid approach to investigate the formation of environmental impacts (EIs) associated with energy conversion systems at the component level. It generates information crucial for designing systems with a lower overall environmental impact, based on life cycle assessment (LCA) and exergy analysis.

A 600 MW supercritical coal-fired system with and without dust, SO2 and NOx mitigation controls was analyzed. Heat transfer in the boiler, condenser (CND), low pressure cylinder (LP), air preheater (APH) show high potential to decrease the environmental impact due to high exergy destructions. The deaerator (DEA), induced draft fan (IDF), forced draft fan (FDF) should be focussed on construction design and manufacturing optimization. Purification units reveal high benefit for reducing EI produced by coal combustion, but there is a large space for the EI saving for it. The specific EI of electricity in China is much greater than European.
Study on Calculation Method of Cooling Oil Flow Rate Allocation for Natural Oil Circulation Transformer
Authors: Xie Rong , Wang Na , Lu Zifu , Cheng Zhonglin , Xu Baopeng
Published: September 2017

For the natural oil circulation power transformer, the hot spot temperature and winding temperature should be within prescribed limits so as to ensure its life and reliability. Temperature rise of inner windings not only depends on the transformer loss, but relates to oil flow closely. Therefore, whether the oil flow of transformer and oil flow distribution rules among the three windings can be predicted or not, relates to success or failure of the winding temperature rise research. According to the structural characteristics of transformer, a three-dimensional computational model including windings and external radiators was built by a three-dimensional modeling software. Initially, from the view of flow, the flow resistance of natural oil circulation power transformer windings has been calculated and analyzed using the CFD methodology, and the resistance characteristic curves about high voltage windings, middle voltage windings, low voltage windings, radiators and pipelines were fitted respectively by the least square method. And then, on the basis of above, the porous media model was applied to simplify the integral model of transformer so as to build a three-dimensional coupled porous media-pure fluid computational model. Meanwhile, the author calculated porosities and linear resistance coefficients of high voltage, middle voltage and low voltage windings. At the end of this paper, to obtain the relationship of oil flow distribution among three windings, the pressure loss was calculated by numerical simulation. Compared with the theoretical calculation results which was based on the part of experimental data, the numerical calculation results are in agreement with these data. And the error between them is within 6 percent. Therefore, the feasibility and accuracy of calculation method, which was used to calculate oil flow of natural oil circulation power transformer windings by the porous media model, has been verified as well. There are two kinds of conventional method to calculate oil flow, including an empirical method and an experimental method. On the one hand, although the former kind of method can be applied conveniently, it cannot consider all the factors so that the accuracy cannot be guaranteed. On the other hand, experimental method to calculate the flow can present high accuracy, but the cost of carrying out experimental study is high. Therefore, this paper presents another calculation method aimed to the flow resistance and oil flow by CFD. And the calculation method presented has higher calculation accuracy compared to above. Meanwhile, the new method provides a theoretical reference about oil flow distribution for the design of the power transformer.
Economic Analysis for Nozzle Governing With Overload Valve Regulation Technology
Authors: Fangbo Jing , Qiang Lai , Dongliang Wei , Xianhui Chen , Yongqiang Yuan
Published: September 2017

With the implementation of low-carbon economy policy, clean energy (such as wind and solar energy) has been developing rapidly, and the percentage is increasing year by year; On the other hand, with a steadily growing percentage of residential electricity consumption and commercial electricity consumption, resulting in large electricity load difference between peak and valley, the load related requirements of modern steam power plants are noticeably changing. Whereas the past units being designed in base load now have to take part in peak load, and usually in a low load operation, unable to play its advantages of high efficiency in design load.

In the article the current three main governing methods (i.e. nozzle governing, throttling governing and bypass governing) for steam turbine will be discussed and evaluated under economical criteria focused on the above described challenges for future power generating technologies. A new governing method is Nozzle governing with Overload Valve Regulation, which keeps the advantage that main steam pressure of the Nozzle governing steam turbine is higher under partial load conditions, and weakens the influence of the low efficiency of governing stage on high pressure turbine, effectively improves the efficiency of steam turbine unit under partial load conditions.

In the turbine adopted the new governing method of Nozzle governing with Overload Valve Regulation, the first stage is governing stage, divided into several groups. Main steam from boiler goes through the main stop valve and main steam control valve in sequence, and then turns to the governing stage. When the load is below 85%THA, main steam control valve I, II and III are fully opened, main steam control valve IV is fully closed, and the unit is in sliding pressure operation. When the load is 85%THA, the main steam pressure can reach the rated pressure. With the load increasing, main steam control valve IV starts to open, but the main steam pressure maintains the rated pressure, adjusted to THA when main steam control valve IV is fully opened and the flowrate of governing stage reaches the maximum. In the load more than THA condition, the bypass valve starts to open, the main steam goes through the bypass steam room into the certain stage (as fourth), to meet the requirements of the super load, adjusted to VWO (about 108%THA) when the bypass valve is fully opened.

Through the detailed description about the scheme set and calculation analysis about economy benefit of the new regulation technology of Nozzle governing with Overload Valve Regulation, it shows that with the annual load range of 40%THA–85%THA, the economy of turbine adopted the new regulation technology is better than bypass governing by about 21.6 kJ/kW.h. (CSPE)
A Unified Approach for the Explosion Limits of the Hydrogen-Oxygen System
Authors: Lidor Alon , Weihs Daniel , Sher Eran
Published: September 2017

We present a new model for the prediction of the explosion limits of the hydrogen-oxygen system. Our model is based on the principle of ignition delay time, postulating that crossing the explosion limit (by increasing the pressure or temperature above it) causes a sharp decrease in the ignition delay time. By using fundamentals of the chain ignition theory, and by employing the Le-Chatelier rule for the explosion limits of fuel mixtures, we develop our model equations. We use numerical analysis to calibrate the constants, and show that our proposed model can accurately capture the unique trend of the peninsula shaped explosion limits. We believe that the relative simplicity of our model will be useful in the analysis of more complex hydrocarbon fuels.
Out Line of the Osaki CoolGen Project
Authors: Ishida Keiichi
Published: September 2017

Coal is a valuable primary energy source that has excellent supply stability and economic efficiency. Japan has extremely low energy self-sufficiency and coal-fired power generation is positioned as an important base load power supply. One urgent issue we face is to find realistic countermeasures that greatly reduce CO2 emissions from coal-fired power plants which produce a large volume of CO2 emissions. Therefore, we have launched the Osaki CoolGen Project since April 2012 as an “Integrated Coal Gasification Fuel Cell Combined Cycle (IGFC) Demonstration Project” subsidized by the Ministry of Economy, Trade and Industry (until 2015 FY) and New Energy and Industrial Technology Development Organization (from 2016 FY). This project aims to realize innovative low-carbon coal-fired power generation that combines an IGFC, an extremely efficient coal-fired power generation technology with high-performance CO2 capture technology for the purpose of dramatically reducing CO2 emissions from coal-fired power generation. This project consists of three steps. The first step will implement demonstration tests of the oxygen-blown Integrated coal Gasification Combined Cycle (IGCC) which is the base technology for IGFC.

Toward the start of demonstration testing in March 2017, construction was started in March 2013 and commissioning was started in April 2016. In the second step, we plan to carry out demonstration tests of the oxygen-blown IGCC with CO2 capture equipment. In the third step, we plan to demonstrate an IGFC system combining the demonstration plant of the second step with a fuel cell.
Removal of Calcium Carbonate Build-Up in Condenser Tubes Restores Efficiency
Authors: Iervoline Larry (Irv)
Published: September 2017

Water is essential to the power generation process, and for many power generation plants that rely on cooling water systems to condense steam, total hardness in source water is a problem. The high mineral content in many sources of cooling water results in hardened, calcified scale deposits forming on the walls of condenser tubes. These deposits form an insulation barrier inhibiting heat transfer. The scale also reduces the inner diameter of the tubes, restricting the flow of cooling water and further reducing heat transfer. As the heat transfer rate falls, performance of the condenser degrades, which can lead to decreasing megawatt output of the plant.

A power station in the United States sources hard lakewater for cooling. Like many plants utilizing hard water, the station relies on a water treatment program to control the formation of hard scale deposits. However, when the plant opened a closed cooling water exchanger (CCW) in its Unit 1, a layer of calcium carbonate was found on the tube walls throughout the bundle.

The CCW exchanger was shot with a variety of mechanical cleaners to thoroughly remove the scale and other deposits and debris from the tubes. Plant management suspected that the same problem might be occurring in the main condenser, and they understood that if scale was forming inside the condenser, the resulting loss in heat transfer rate would be a contributing factor in the decreased efficiency of the unit.

Since the plant was planning an eddy current test on 100% of the more than 12,000 stainless steel tubes in the main condenser, the tubes were required to be thoroughly cleaned. Upon opening the main condenser, technicians verified the presence of calcium carbonate fouling, confirming their suspicions. While not knowing the condition of the tubes underneath the deposit, plant engineers were concerned about the underlying tube condition. They were also looking for alternative cleaning methods to provide relief from environmental concerns often associated with chemical cleaning. To preserve tube integrity and assure thorough removal of deposits, the plant decided to clean the condenser tubes utilizing the same mechanical cleaning method as the CCW unit. The condenser tubes would be shot with a series of specialized mechanical tube cleaners, one designed to fracture the calcium carbonate and a second designed to remove the fractured scale and other deposits from the tubes.

This paper highlights the role of hard water in condenser tube fouling, the need to remove scale from condenser tubes and the mechanical cleaning process that was used to restore condenser performance at a prototypical coal fired power station in the United States.
New Structure and Manufacturing Process of Integral Nozzle Block
Authors: Cai Zhenming , Zhou Huifeng
Published: September 2017

The nozzle block is one of the most important parts of steam turbine. It puts the steam heat energy into kinetic energy and plays a guiding role to the steam flow. The open integral nozzle block is a very unique structure. Due to the restriction of the large steam passage bending degree and the small nozzle mouth, the traditional process is difficult and the production efficiency is low. This paper mainly studies the structure and processing method of a new open integral nozzle block. The difficulties of the manufacturing process are being solved one by one by the way of developing the five-axis NC program, designing the special tooling and making the process technical solution. The process technical solution is to split the whole complex structure into three main parts which are easy to machine. It can easily realize the surface finishing of the steam passage and guarantee the geometric dimension of each steam blade. The surface roughness of the steam passage can reach Ra0.8. The precision requirements for machining and assembling of the open integral nozzle block can be fully met. It has a wide application prospect in promoting the scientific and technological progress of the new structure and the new process.
Numerical Study on the Erosion Characteristics of U-Type Bend for Gas Solid Flow
Authors: Wang Yu , He Qi , Liu Ming , Chen Weixiong , Yan Junjie
Published: September 2017

In pulverized coal-fired plant, the U-type bend is commonly used in flue gas and pulverized coal pipe system to due to the constraints of outer space. And gas-solid two-phase flow exists in these pipelines. The erosion of the pipe has significant effect on the safety and reliability of pipelines. In present paper, the erosion characteristics of U-type bend were investigated through CFD (Computational Fluid Dynamics) method. The wear distribution on the pipe wall was obtained. And the particle flow characteristics in U-type bend were analyzed. The influence of inlet velocity, mass loading rate and particle size on the erosion rate was studied as well. Result suggested that the maximum erosion rate increases exponentially with the increase of inlet velocity. And maximum erosion rate increases linearly with the increasing mass loading rate. Increasing particle size can aggravate the wear on the pipe wall.
Investigation of Catalytic Combustion in the Rotary Regenerator Type Catalytic Combustor at Different Inlet Velocities
Authors: Sang Zhenkun , Lv Xiaojing , Bo Zemin , Weng Yiwu
Published: September 2017

Ultra low calorific value gas (ULCVG) is hard to be realized by the conventional combustion technology. Most of them are discarded into atmosphere directly, causing the inadvertent waste and serous pollution. Currently, a new type gas turbine with catalytic combustion and rotary regenerator can be used to utilize these fuels and mitigate pollution. Differing from the conventional gas turbine, the chamber and regenerator of the new gas turbine is combined into one component, which is named rotary recuperative type catalytic chamber (RRTCC). The catalytic combustion is applied for RRTCC. The catalytic combustion characteristic of RRTCC is studied using the computational fluid dynamics (CFD). The results indicate that when the inlet velocity is 20 m/s, the methane conversion rate is 90%∼95%, and the corresponding outlet gas temperature is 1030∼1200K. When there is a variation of ±25% in the inlet velocity, the variation of methane conversation rate is −15% and 5% respectively, and the variation of outlet gas temperature is −6% and 2% respectively. Additionally, it is found that the hotspot temperature of combustor wall decreases with the increase of inlet velocity. The lowest value of hotspot temperature is about 1000K, which is higher than the ignition temperature of CH4. Therefore, the existence of hotspot temperature is useful for the catalytic ignition. The temperature distribution on the combustion side exhibits a smoking-pipe-like shape, as well as the recuperative side. The results can provide data reference for RRTCC design.