bluuebunny/crossref_metadata_2025 huggingface dataset:
On Linearizing the Steam Mass Flow Relative to the Controller Output
Authors: Zimmer Gerta , Hiss Florian C.
Published: March 2012

In order to develop efficient control and to predict a steam turbine’s power output precisely, it is desirable to have a linear relationship between controller output, RA, and steam mass flow. Unfortunately, steam mass flow through a turbine is not only determined by the control valve stroke but also by the pressure in front of these valves. Even at constant pressure the relation between valve stroke and steam flow through the turbine is extremely non linear. The complexity is increased by the fact that a turbine is generally operated by two or four control valves which do not necessarily work parallel over the complete operational range. Additionally, the pressure in front of the control valve changes with the admitted steam mass flow. A counterbalancing method was developed that allows to include individual process data, such as pressure in front of the valves and at the turbine inlet in dependence of steam mass flow and valve throttle characteristics, as well as process engineering constraints, like valve staggering, for example. The developed method is applicable to new steam power plants as well as to retrofits. With the developed method it is also possible to predict individual valve strokes at valve testing or at deviating exterior conditions. The later feature is extremely useful for retrofit applications. Firstly, the correctness of the implementation with respect to the ‘old’ set-up can be verified, and then, secondly, the characteristics of the retrofitted components and thermodynamic conditions, respectively, can be substituted. The developed method was successfully applied for several power plants. A comparison of predicted data and commissioning data will be provided.
Distributed Combustion With Swirl for Gas Turbine Application Using Low Calorific Value Fuel
Authors: Khalil Ahmed E. E. , Gupta Ashwani K.
Published: March 2012

Distributed Combustion offers significant potential for improved performance and near zero emissions for gas turbine and other industrial applications. Our quest for zero emission distributed combustion is further explored here by utilizing swirl to the flow. The beneficial aspects of distributed swirl combustion are examined with special focus on near zero emissions of NO and CO, and significantly improved pattern factor of the combustor using low calorific value fuel. Methane gas diluted with inert gas is used to simulate the low heating value fuel. A cylindrical geometry is used for combustor with air injected tangentially to impart swirl to the flow. The combustion behavior is evaluated using normal and preheated air at inlet to the combustor. Experimental results from the distributed combustor design using methane fuel showed low levels of NO (<8PPM) and low CO (∼21PPM) under non premixed conditions at an equivalence ratio of 0.7 and high heat release intensity of 36MW/m3-atm. With preheated air to the combustor, results showed overall NO levels of <15PPM and CO ∼12 PPM for non premixed combustion at an equivalence ratio of 0.6 under high heat release intensity of 27MW/m3-atm. Low heating value gas resulted in a dramatic decrease in NO emissions (30–50%) with minimal effect on CO for all the conditions examined here. Results obtained with different calorific value fuels on the emissions of NO and CO, lean stability limit and OH* chemiluminescence are presented.
Retrofit of a 75T/H PC-Fired Boiler Into a Coal/Gas Co-Firing One
Authors: Wen Dazhui , Chen Donglin , Xu Huifang
Published: March 2012

For full use of low heat value of coke oven gas and operation under conditions of coal, gas and coal/gas, a previously 75t/h PC-fired boiler was retrofitted: six gas burners with dual-passage were installed under the originally PC-fired burners and tangentially arranged with a larger combustion circle and declined axes; the pulverized coal fired burners were declined downward 8∼10° so as to control the flame center; the heating surface of slag cooling tube and economizer were extended. The operation and test after the retrofit showed that: the combustion was very stable and temperature of the superheated steam was between the normal range under all conditions of load and fuel; the maximum steam rate was 59t/h and temperature of the exhaust flue gas was lower than 160°C under gas condition while gas flow was at 26000 Nm3/h; the maximum steam rate was 81t/h and temperature of the exhaust flue gas was lower than 147°C under coal condition; the maximum steam rate was 77t/h and temperature of the exhaust flue gas was about 155°C under coal/gas condition.
Reliability Assessment and Useful Life of Turbine Blades Using Probabilistic Methods
Authors: Rodri´guez J. A. , Garci´a J. C. , Urquiza G. , Basurto M. , Sierra F.
Published: March 2012

Steam turbines have numerous applications in various sectors of industry and it is known by experience that blade failures are the most common origin of breakdown in these machines, causing significant economic losses in turbomachinery industry. The turbines are designed to work in stable conditions of operation; nevertheless, failure in blades could appear after a short time of work. Failures are attributed to resonance of the blades to certain excitation frequencies. The vibration stresses reached by resonance conditions and the combination of other random variables could determine the useful life of the blades. In the deterministic design of turbines, the failure possibility is reduced in acceptable small levels by means of safety factors based on the good judgment. However, the possibility of failure could be reduced by using probabilistic methods. In the probabilistic approach, the variability in the properties of the material, tolerances in manufacture and uncertainties in the load are considered with statistical methods. The probabilistic method allows to evaluate the uncertainty or randomness present in some variables which translates in a high level of reliability in the results and a better operation analysis of the turbines. There are a lot of variables in the operation of the turbomachineries, in its design and construction. These variables are conceived under a certain degree of uncertainty, that is to say, these cannot be totally controlled. Generally, repeated measurements of mechanical phenomena generate a lot of input variables each one with certain instability in their magnitude that contributes to increase the probability of failure before the estimated time. In this work the reliability and useful life of blade steam turbines of 110 MW of the L-0 stage are analyzed using deterministic numerical methods and a probabilistic approach. Curves of the useful life for both cases are obtained. The probabilistic approach shows that failure occurs when a combination of variables and the presence of failure are combined.
Fixed Duct Burner Heat Input Approach for Combined Cycle Power Plant ASME PTC 46 Performance Testing
Authors: Kirkpatrick Thomas K. , Pastorik Bernard J. , Newland Wesley M.
Published: March 2012

Since its publication in 1996, ASME PTC 46 Performance Test Code on Overall Plant Performance has established itself as the premier test code for conducting overall plant performance within the power industry, especially for combined cycle power plants. The current text within ASME PTC 46, which is currently under revision by the ASME PTC 46 Committee, describes in Section 5.3.4 Specified Measured Net Power that “This test is conducted for a combined cycle power plant with duct firing or other form of power augmentation, such as steam or water injection when used for that purpose.” Further, the only example problem for a combined cycle with duct firing is provided in Appendix B of the code utilizing the Specified Measured Net Power Test Method. Though the text and example are correctly presented within the code, it resulted in misinterpretation within the industry that the only correct way to test a combined cycle plant with duct firing was to conduct a Specified Measured Net Power Test. Though the Specified Measured Net Power Test Method is an acceptable and accurate method in determining the performance of a combined cycle plant with duct firing in operation, it lends to being inflexible to the weather conditions for the plant operation. When the weather is too cold, the exhaust energy from the combustion turbines may be at such a magnitude as to not allow the duct burners to be fired due to limitations within the heat recovery steam generator and steam turbine systems to take the load, thus limiting the plant testing to take place when the weather is warm enough to allow the plant to be operated with duct firing. The opposite condition can also exist where the ambient conditions are too hot so that the duct burner capacity is unable to achieve the specified measured net power allowing the test to be conducted. The limitations stated herein are the reasons that an alternative approach with more flexibility is necessary. This paper will present an alternative approach referred to as the Fixed Duct Burner Heat Input Test Method to testing combined cycle plants where the duct burner heat input (Fuel Flow) is held fixed while the plant net power and heat rate are left to float with ambient conditions. Corrections for both power and heat rate will be developed for ambient conditions per ASME PTC 46 guidelines. This paper will further present a comparison between the Specified Measured Net Power Test Method and the Fixed Duct Burner Heat Input Test Method in the areas of the flexibility of the methods for various ambient conditions, and the method uncertainty associated with each method’s ability to correct to reference conditions.
Steam Turbine Valve Testing, Inspection and Maintenance to Avoid Turbine Overspeed Events
Authors: Mutama Kuda R.
Published: March 2012

Steam turbine valves are the most important components before a steam turbine for the admission and control of steam flow. Steam turbine valve configurations can be all in one body or as individual valves for the large units, for the main stop (throttle) and control functions for each section of the steam turbine. Today’s thermal power plants for drum or once-through type supercritical boilers produce very high temperature steam in the final superheat and reheat section of 1055 °F or higher requiring special boiler tube metal alloys, some of which are subject to steam oxidation as in austenitic steels. The oxidation material is mainly in the form of iron oxide or magnetite which is subject to exfoliation. The exfoliated oxide material is carried over to the steam turbine valves and to the high and intermediate pressure turbines. The effect of exfoliated oxide material in valve and turbine components is to cause solid particle erosion (SPE) and therefore shortening the life of those parts due to damage. As time goes by if valves are not tested and do not meet their inspection and maintenance schedule they will build up oxidation material to form scale material called blue blush and eventually they stick and will not shut properly.
Tampa Electric Company - Big Bend Station, The First Complete Station Titanium-Tubed Modular Condenser Changeout - Units 1–4: A Case Study
Authors: Clarke Patrick , Nightingale Darren M. , Proud Earl , Schumerth Dennis J.
Published: March 2012

Tampa Electric Company, (a TECO Energy Company) Big Bend Power Station is located on the east shore of Tampa Bay, in Hillsborough County, Florida. The station operates four (4) coal-fired units as described in Table 1A. The condensers for these units are cooled with sea water taken from Tampa Bay. In 2005, as part of a management sanctioned effort to restore plant capacity, and improve long-term plant reliability and availability, it was concluded that, among other plant upgrade considerations, titanium-tubed modular condensers should replace all four existing units. In support of this effort, our case study will highlight and present salient issues relating to this specific project conception, evaluation and implementation. Ancillary issues including integration of existing ball cleaning systems, constraints on circulating water pump flow, environmentally-driven limitations on temperature discharge, localized MIC attack, material selection considerations and installation logistics and constraints will also be discussed. The paper will present a rigorous evaluation covering the long-term benefits when comparing a modular changeout vs. the direct condenser retube option. Since unit performance prior to the revamping was well documented in advance of workscope completion, the newly installed system could be directly compared against historical norms. As a result, expanded coverage of the successful Unit 1 & 2 results of this unique comparison capability will be identified. In terms of industry precedence, the documented success of this project demonstrates that this first-of-a-kind sequential modular condenser installation at a multiple-unit, coal-fired power station has satisfied management expectations providing the Big Bend Stations with sustainable power generation reliability for the future, restored unit capacity and created an innovative and cooperative interconnectivity between the utility and vendor alike.
Qualitative Analysis of an Axial Compressor Model With Non-Constant Speed
Authors: Sari Gh. , Akhrif O. , Saydy L.
Published: March 2012

In this research we have addressed the study of the qualitative behavior of nonlinear variable speed axial compressors model exhibiting surge and stall instabilities. Such a study can shed some light on the development of an effective control approach being capable of simultaneously controlling the speed and instabilities. The controller can stabilize the system around an effective operating point and improve performance and reliability of variable speed axial compressors widely used in aeronautic industries. Although previous studies [1, 2] have focused on developing a model for non-constant speed axial compressors, qualitative characteristic of such a model is still unclear and its active control including both rotating stall and compressor speed is still a challenging problem. In this study we are particularly interested in investigating effects of the acceleration of the compressor rotor on qualitative properties of the model. To this end, bifurcation analysis of an axial compressor model with spool dynamics was performed and the simulation of the model was developed along the way. Preliminary surprising results revealed that the type of instability, surge or rotating stall, not only depends on the final speed as thought before but is also deeply affected by the rate of the rotor acceleration. Impacts of the initial speed on the qualitative properties of the model were demonstrated as well. Furthermore previous work [1, 2] showed that amplitudes of stall harmonics grow during the speed transition and cause a temporary pressure drop at the compressor output. Our simulation results supporting the bifurcation analysis of the model revealed that during speed transitions both amplitudes of high order stall harmonics and the number of dominant harmonics also depend on the rate of the acceleration and the initial speed.
Debris Laden Backwash Pump Performance Evaluation
Authors: Humphrey Amie M. , Haber Ludwig C. , Smith James M. , Wiggin James N.
Published: March 2012

McGuire Nuclear Station and Alden Research Laboratory recently completed an extensive computational and experimental study characterizing the operating fluid mechanics and debris clean-out behavior of a rotating-drum strainer. The strainers are used in the plant for raw water (RN) and are installed on the suction side of the RN system pumps. The study served a twofold purpose. The first part of the study identified the requirements for flow withdrawal from the strainer to ensure adequate cleaning performance. It also identified the maximum debris loading rate at which the strainer could reject debris into the outlet channel [1]. The findings defined input to the second part of the study, the backwash pump performance evaluation, which is the focus of this paper. The backwash pumps will be installed to backwash the strainers with performance requirements based on the results of part one of the study. MPR Associates joined the effort to evaluate different pumps for performance under normal operating and design basis conditions. A test loop was constructed that allowed controlled debris injection at atmospheric and vacuum conditions. Vacuum condition performance is required since some operating conditions generate pressures inside the strainer near 9 ft abs. This paper summarizes the performance differences by pump type and discusses the characteristics of debris-laden performance relative to standard performance and the influence of degraded conditions on debris handling.
Solar Receiver Steam Generator Design for the Ivanpah Solar Electric Generating System
Authors: Plotkin Andrew R. , Toupin Kevin M. , Gillum Craig B. , Rancatore Robert J. , Yang Tianliang , Mier Diego
Published: March 2012

The movement for energy independence coupled with aggressive renewable energy goals and government investment incentives has led the power industry to develop efficient and reliable sources of renewable power. In a power tower system a central Solar Receiver Steam Generator (SRSG) is surrounded by a field of mirrors (heliostats) that focus and concentrate sunlight onto the receiver tubes. The energy from the sunlight is used to generate and superheat steam for electric production. The Ivanpah Solar Electric Generating System (ISEGS) project, located in Ivanpah, CA, consists of three 126 MWg units, to power approximately 140,000 homes. The Ivanpah SRSG’s are forced circulation drum-type boilers with single reheat; located on top of a 400 ft (122 m) steel tower [1]. This paper will discuss the development, constraints, and unique design challenges of the Riley Power Inc. (RPI) SRSG selected for the Ivanpah project. Process descriptions and predicted unit performance are presented, along with comparisons to typical fossil boilers. First of kind concepts and engineering design achievements are discussed for what will be the largest power tower project in the world.
Burner Component Upgrades for Wall-Fired Coal Burners: RPI Results and Experiences
Authors: Black Stephen W. , Yaldizli Murat
Published: March 2012

Improving the operation and emissions performance of coal fired utility boilers equipped with first and second-generation wall fired low NOx coal burners is of significant interest to many utility companies today. The recent development of cost effective components for existing first and second-generation wall fired burners permits better combustion performance, increased wear life reliability, and decreased NOx emissions. Existing air register systems can typically remain in place, resulting in reduced capital cost and reduced outage time for installation. Computational fluid dynamic (CFD) modeling is used to assist in the design of key burner components and operating conditions that enable further reduction of NOx emissions. Results include better flame attachment, better airflow recirculation patterns, and early ignition and pyrolysis of the coal in a more controlled primary combustion zone. NOx reductions of 10–20% have been demonstrated using burner component upgrades with improved overall boiler operation. This paper gives a brief description of the component-only retrofit design methodology that Riley Power Inc., a Babcock Power Inc. company developed for other OEM’s low NOx burners in wall-fired furnaces. The numerical modeling to assist in the design of these low NOx systems and the corresponding CFD results are also discussed.
Analysis of an Integrated Downdraft Gasifier/SOFC System Biomass Fueled
Authors: Campitelli Gennaro , Mulone Vincenzo , Cordiner Stefano , Gautam Mridul
Published: March 2012

The connection between combined power and heat generation, and the concept of distributed generation is a relevant issue viz. improvement of the overall efficiency of energy conversion and distribution. In this context, the use of biomass may be of particular interest due to its potentially very low CO2 emissions as well as low kWh production cost with respect to other renewable energy sources. Traditional methods to convert biomass involve micro-turbines or steam power plants. However, both electrical and overall efficiencies may not be particularly high for both technological and thermodynamic reasons; the latter being hard to supersede. High temperature Solid Oxide Fuel Cells (SOFCs) offer an attractive solution because they are characterized by electrical efficiencies in the range of 35% to 48% [1], and present a significant potential for integrating with the biomass gasification process; thus, exploiting advantages of high operating temperatures. Moreover, thermal integration is of prime importance. In fact, optimal management of thermal integration may allow operation with high moisture content feedstocks and with high water concentration in the SOFC; thus, promoting further hydrogen production via the water gas shift reaction [2]. In this paper, an integrated solid oxide fuel cell-gasifier system is modeled to identify the main effects on fuel cell performance under several operating conditions in terms of biomass flow rates and moisture contents. The SOFC and the gasifier are modeled by a zero dimensional approach to perform a sensitivity analysis with a numerical tool which requires less computational effort compared to those previously presented. The thermochemical phenomena are taken into account with a high degree of detail, and model validation is also showed via comparison with literature available data. Results highlight the impact of biomass feedstock and its moisture content on the electrical current density value. Final performance depends on the interaction among gasifier thermal sustainability, SOFC operating temperature and chemical equilibrium concentrations, via water gas shift reactions. In particular, it has been shown that thermal integration allows operation with higher moisture content biomass, thereby further exploiting H2O conversion into H2 via water gas shift reactions and high fuel utilization operating conditions. The importance of thermal integration and advanced control of SOFC based biomass fueled systems is demonstrated by this study, as well as the use of a fast and reliable zero-dimensional modeling for system design and control purpose.
Turbogenerator Spark Erosion Inspection and Repair
Authors: Jensen John , Laforet Alfred
Published: March 2012

Spark erosion has re-emerged in a number of air-cooled generator units installed in the United States from 1998 to 2006. The purpose of this technical paper and presentation is to review new inspection & repair methods to help operators to determine the best repair options. To develop better inspection methods one has to understand the root cause for spark erosion in generator stators. The theory of two different spark erosion phenomena is discussed in this paper. Spark erosion caused by capacitive slot discharges (partial discharges) is a well known effect in high voltage (HV) machines and very dangerous in respect to insulation damage. The vibration sparking phenomenon will also be explained, which is different from the partial discharge (PD) effect caused by interruption of current paths. As a next step inspection methods are described. In the past, inspections to identify spark erosion used only the visual method. This method could only provide the subjective opinion of the inspector and was a single input to decide the condition of the generator stator windings and possible life extension (rewind) solution. In order to give the operators more options, Alstom developed advanced electrical test methods to allow a more accurate condition assessment. The result of multiple inspection methods allows a much better understanding of the stator winding condition. Since spark erosion is a process that deteriorates the insulation of the stator bar over time, additional data points (multiple test methods) can help to utilize multiple repair options that will not require complete rewinding of the stator to reach expected reliability of the generator. Alternative repair options are then discussed in the paper.
The Corresponding Relationship Between Heat, Mass Transfer Coefficients and the Flow Regime in Dual-Contact-Flow Absorption Tower
Authors: Zhang Yafei , Zhou Qulan , Zhang Yi , Zhao Qinxin , Hui Shi’en
Published: March 2012

The flow, heat and mass transfer performance under different nozzle arrays in the dual-contact-flow absorption tower has been studied, together with the interrelation between the probability dense function (PDF) and the flow, heat and mass transfer characteristics. The experimental results show that, for the same nozzle array, both the heat and mass transfer coefficients (h and hm) increase with the gas velocity increasing at first; However, both coefficients (h and hm) start to decrease due to the reduction of the liquid-gas contact time after approaching a certain extent. Moreover, with the increase of liquid injection rate νp0, the two coefficients (h and hm) decrease, while the total heat and mass transfer values rise. In addition, the mass transfer coefficient decrease with the increase of nozzle number. In the absorption tower, the leading role gradually transfers to gas phase from liquid phase with the increase of gas velocity. The flow regimes’ transition process can be explained as follows: the liquid column flow type, the liquid screen flow type, the convergent liquid screen flow type, and the gasping flow type. Moreover, the increase of gas velocity has effects on the probability dense function (PDF). With the flow regimes’ transition, change of PDF performs as follows: the number of the PDF peaks increases from one to a larger quantity and finally decreases to a single one after that; the average pressure drop ΔPmean increases as well as the peak-peak spacing δpeak. However, the pressure drop distribution range lΔP first increases and then decreases.
Numerical Simulation Research on 600MW Boiler With Different Single Burner Heat Power
Authors: Luo Rui , Li Na , Zhou Qulan , Hui Shi’en , Zhao Qinxin
Published: March 2012

With the increasement of pulverized coal utility boiler capacity, whether increasing the single burner heat power or not has not been confirmed. The mathematic model of realizable k-ε and discrete particle model (DPM) are used to describe the gas and solid phase flowing. The P-1 radiation model and the probability density function (PDF) model are utilized to solve radiation heat transfer and heat chemical calculation. The calculation results display the detailed aerodynamics field and temperature distribution in 600MW utility boiler which satisfies with actual operation conditions. The burners and OFA effectively organize the aerodynamic field in boiler. Pulverized coal starts burning after a short time away from spouts. Through discussing ignition distance, fuel conversion, NOx emission, outlet velocity and temperature, and hot corrosion tendency, it is found that burner single power obviously affected ignition distance and hot corrosion. The condition of furnace with 48 burners installed in 600MW boiler is considered having a better performance.
Studies on Flow and Pipe Wall Thinning and the Reduction in the Downstream of Orifice Nozzle
Authors: Shakouchi Toshihiko , Suzuki Takayuki , Yuya Hideki , Naruse Masaki , Tsujimoto Koichi , Ando Toshitake
Published: March 2012

In a piping system of power plant, pipe wall thinning by Flow Accelerated Corrosion, FAC, Liquid Droplet Impingement Erosion, LDI, and Cavitation Erosion, C/E, are very serious problems because they give a damage and lead to the destructtion of the piping system[1]–[6]. In this study, the pipe wall thinning by FAC in the downstream of orifice nozzle, flow meter, is examined. Namely, the characteristics of FAC, generation mechanism, and prediction of the thinning and the reduction are made clear by experimental analysis. As a results, it was made clear that (1) the thinning is occurred mainly according to the size of the pressure fluctuation p′ on the pipe wall and the thinning can be estimated by it, and (2) the suppression of p′ can be realized by replacing the orifice to a taper shaped one having an angle to the upstream.
Application Study of Newly Developed Turbo Heat Pump for 130 Degrees Celsius Water for an Industrial Process
Authors: Umezawa Shuichi , Amari Haruo , Shimada Hiroyuki , Matsuhisa Takashi , Fukushima Ryo , Ueda Kenji
Published: March 2012

This paper reports application study of newly developed turbo heat pump for 130 degrees Celsius (°C) water for an industrial process in an actual factory. The heat pump is characterized by high efficiency and large heat output, by using a state-of-the-art turbo compressor. The heat pump requires a low temperature heat source in order to achieve high efficiency. The heat demand is for several drying furnaces in the factory, which requires producing hot air of 120 °C. The heat exchanger was designed to produce the hot air. Experiments were conducted to confirm the performance of the heat exchanger under a reduced size of the heat exchanger. Low temperature heat sources are from both exhaust gas of the drying furnaces and that of an annealing furnace. The heat exchangers were also designed to recover heat of the exhaust gas from the two types of furnace. A thermal storage tank was prepared for the low temperature heat source, and for adjusting the time difference between the heat demand and the low temperature heat source. The size of the tank was determined by considering the schedule of furnaces operations. As a result of the present study, it was confirmed that the heat pump was able to satisfy the present heat demand while retaining high efficiency. Primary energy consumption and CO2 emission of the heat pump were calculated on the basis of the present results in order to compare them with those of the boilers.
Optimization of a Biogas-Fuelled Cogeneration System in a Sewage Treatment Plant
Authors: Basrawi M. Firdaus B. , Yamada Takanobu , Nakanishi Kimio
Published: March 2012

Efficient utilization of biomass by a cogeneration system (CGS) is a promising technology for promoting sustainable energy development. Sewage treatment plants are facilities that have been continuously producing biogas by anaerobic digestion. Thus, the potential of a biogas-fuelled CGS in a sewage treatment plant is estimated to be very high. However, there have been few reports on the performance of a biogas-fuelled CGS, particularly regarding the effect of ambient temperature on its performance, and the most efficient arrangement of a biogas-fuelled CGS remains unknown. In this study, performance of a biogas-fuelled CGS was simulated under three typical ambient temperature (low, medium and high) conditions using actual data for a CGS with a micro gas turbine. In the beginning of this study, the relation of energy balance of the plant and ambient temperature was clarified. It was found that the amount of heat demand is ambient temperature-dependent but that the amount of biogas fuel produced is almost constant throughout the year. When a boiler is replaced with a biogas-fuelled CGS to utilize the biogas, under a high temperature condition, the CGS is not able to fully utilize all of the biogas produced, and therefore another pathway of biogas utilization is needed. Under a medium temperature condition, a gas storage system is needed for using biogas efficiently. However, some of the biogas still cannot be utilized efficiently. Under a low temperature condition, since ambient temperature varies greatly between summer and winter, the amount of heat demand of the plant also varies greatly throughout the year. This leads to an imbalance in biogas production and heat demand, and therefore attention must be given to energy management in this condition. The combination of other auxiliary equipment such as a boiler, heat pump and gas storage with the CGS is required in order to cover the total heat demand throughout the year. Four possible arrangements of the CGS with different auxiliary components were proposed and their performances were compared. It was found that all of the proposed CGS arrangements can sufficiently cover the total heat demand by only using biogas produced in the facility. Compared to the conventional system, all proposed CGS arrangements can reduce electrical power demand by 23∼28%, recover 74∼77% of the energy of biogas produced, and utilize almost 100% of the biogas produced. The arrangement with a heat pump is more efficient than the arrangement with a boiler. It was also found that excess biogas in summer can be used in winter by storing the biogas. Thus, a CGS arrangement that includes a gas storage system will enable efficient utilization of biogas and recovered exhaust heat.
Three-Dimensional Visualization of Water Behavior in Polymer Electrolyte Fuel Cell by Using Neutron Radiography
Authors: Hashimoto Michinori , Murakawa Hideki , Sugimoto Katsumi , Asano Hitoshi , Takenaka Nobuyuki , Mochiki Koh-ichi
Published: March 2012

Visualization of dynamic three-dimensional water behavior in a PEFC stack was carried out by neutron CT using a neutron image intensifier for clarifying water effects on performances of a Polymer Electrolyte Fuel Cell (PEFC) stack. Neutron radiography system at JRR-3 in Japan Atomic Energy Agency was used. An operating stack with three cells based on Japan Automobile Research Institute standard was visualized. A consecutive CT reconstruction method by rotating the fuel stack continuously was developed by using a neutron image intensifier and a C-MOS high speed video camera. The dynamic water behavior in channels in the operating PEFC stack was clearly visualized 15 sec in interval by the developed dynamic neutron CT system. From the CT reconstructed images, evaluation of water amount in each cell was carried out. It was shown that the water distribution in each cell was correlated well with power generation characteristics in each cell.
Study on Thermal Hydraulic Characteristics of the Stacked High Pressure Resistance Microchannel Heat Exchanger
Authors: Asaba Shingo , Iiyama Koji , Kaneko Akiko , Abe Yutaka , Suzuki Yutaka
Published: March 2012

Recently, development of a small size and high efficient heat exchanger, which is utilized in a fuel battery and a heat pump system for CO2 refrigerant and so on, is strongly required. In author’s previous studies, the prototype of the stacked high pressure resistance microchannel heat exchanger manufactured with diffusing bond technique has been proposed. The objectives of the present study are to reveal flow and heat-transfer properties of counter-flow microchannel heat exchanger and to reveal the heat transfer mechanism with condensation in a microchannel. As the results, it is found that heat transfer rate of the present heat exchanger with high- and low-temperature water as working fluids is approximately 8 kW which is 2 kW higher than that of the existing heat exchangers. It is suggested that the flow pattern in a microchannel transits from annular flow to injection flow, and finally it becomes bubbly flow.
Hydrogen Production by a Steam Reforming Reactor for Heavy Hydrocarbons
Authors: Fujimoto Yasutaka , Shinoki Toshio , Tanigawa Hirochika , Funaki Jiro , Hirata Katsuya
Published: March 2012

The authors develop a small and simple steam-reforming reactor in a home-use size for n-dodecane as a heavy-hydrocarbons fuel. Under the thermal condition controlled by electric heaters and a gas burner with a thermal diffuser, the authors measure the inside-temperature profile and the hydrogen-molecule ratio (concentration) RH2, together with the molecule ratios RCH4, RCO and RCO2 of other main gas components such as CH4, CO and CO2, respectively. Besides, the authors conduct numerical simulations based on a thermal-equilibrium theory, in addition to experiments. As a result, the authors successfully achieve suitable inside-temperature profiles. And, the effects of the liquid-hourly-space velocity LHSV upon RH2, RCH4, RCO and RCO2 are shown, experimentally. For LHSV ≤ 1, the experimental results agree well with the thermal equilibrium theory. This is in consistent with high conversion ratio XC12H26 ≳ 80%. Furthermore, the authors reveal the effects of the temperature T inside the reactor upon the molecule ratios, comparing with the thermal-equilibrium theory.
Film Cooling With Swirling Coolant Flow Controlled by Impingement Cooling in a Closed Cavity
Authors: Takeishi Kenichiro , Oda Yutaka , Egawa Yuta , Hada Satoshi
Published: March 2012

A new film cooling concept has been developed by managing the swirled film coolant induced inside a hexagonal plenum by two slant impingement jets, which are inclined at α degree toward the vertical direction and installed in a staggered position on the plenum chamber wall. Film cooling tests have been conducted by using a circular film cooling hole model mounted on a low speed wind tunnel. Heat transfer coefficient distributions of inclined jet impingements in a closed cavity was measured by naphthalene sublimation method and the film cooling effectiveness on the surface of the wind tunnel was measured by pressure sensitive paint (PSP). It appeared from experimental results that the swirled film coolant flow deteriorated the film cooling effectiveness at low swirl number but improved it at high swirl number. To investigate the mechanism of the improved film cooling effectiveness by the swirled coolant, the spatial distribution of the film cooling effectiveness and flow field were measured by laser induced fluorescence (LIF) and particle image velocimetry (PIV), respectively. The coolant jet penetration into mainstream is suppressed by the strong swirling motion of the coolant. As a result the film cooling effectiveness distribution on the wall keeps higher value behind the cooling hole over a long range. Additionally, kidney vortex structure was disappeared at high swirl number.
Influence of a Flow Obstacle on Boiling Two-Phase Flow
Authors: Ami Takeyuki , Umekawa Hisashi , Ozawa Mamoru
Published: March 2012

The spacer of Boiling Water Reactor (BWR) becomes the flow obstacle. Moreover the clearance between fuel rods of the innovative Water Reactor for Flexible fuel cycle (FLWR) becomes very narrow. Thus understanding of the thermal-fluid characteristics in the boiling channel equipped with the flow obstacle becomes more important. In this study, to clarify the flow obstacle effect, the experimental investigation was conducted with the forced convective boiling system. The test section was 8 mm in inner diameter, and the rod-type flow obstacle, which had 3.6 mm in diameter and 20 mm in length, was installed. The blockage ratio β = 20.3% which was the similar value of the present BWR reactor. The heating length LT was taken three different lengths, LT = 810, 840 and 900 mm. As the experimental results, the CHF was increased by the installing of the flow obstacle, and it was strongly influenced by the axial position of the flow obstacle. In the most of the case, the liquid film dryout was detected at the exit of the test section, while the CHF was observed at the upstream of the flow obstacle in the case of the LT = 810 mm. The calculation results of the liquid film flow model have shown a good agreement with these experimental results by using the presented influence length of the flow obstacle.
Numerical Investigation on Aerodynamic Similitude for Axial Microfan
Authors: Wang Qikun
Published: March 2012

Axial microfan is widely used as cooling equipment for electronic devices such as PCs. Currently, the PC size becomes smaller and smaller while their operating speed becomes faster and faster, which calls for better cooling performance of axial microfan. As an important and effective design approach, the similitude design has been widely used in the design of large and medium fans, but not yet in the design of axial microfan. The traditional similitude design approach may work well in self-similitude area for Reynolds number, such as the flow inside the large and medium fans, where simple geometric similitude can promise the aerodynamic similitude. But the flow inside the microfan locates in non self-similitude area for Reynolds number, where the traditional similitude design for large and medium fans may be out of work on microfans, which results in poor performance of the microfan designed by the traditional similitude approach. In this paper, the aerodynamic similitude conditions for axial microfan are presented according to the similitude principle for aerodynamics. Compared to large and medium fans in self-similitude area, a new criterion called ‘Chord Reynolds Number Criterion’ suitable to the flow in non self-similitude area is proposed and is numerically validated with discussions on its applicability and limitation. Results indicate that ‘Chord Reynolds Number Criterion’ can well realize the aerodynamic similitude for the axial microfan but it requires that the revolution speed of the impeller should be in direct proportion to the squared minification of the model impeller, so the reduced scale of model impeller shall not be too large, otherwise new non similitude factors may occur again due to too high revolution speed.
Dissolution Rate of Limestone for Wet Flue Gas Desulfurization in the Presence of Citric Acid
Authors: Guo Rui-tang , Pan Wei-guo , Zhang Xiao-bo , Wu Jiang , Ren Jian-xing
Published: March 2012

Dissolution rate of limestone for wet flue gas desulfurization in the presence of citric acid was measured by pH-stat method. It was found that limestone dissolution rate in the presence of citric acid was controlled by mass transfer. As can be seen from the experimental results, in the presence of citric acid, limestone dissolution rate increased with increasing stirring speed and reaction temperature. When pH value was greater than or equal to 5.5, due to the formation of calcium citrate, citric acid would inhibit the dissolution process of limestone. And the inhibition effect was more obvious at higher pH value.
Fast Transient and Intensified Heat Dissipation Applicable to High Heat Flux Density
Authors: Li Jing , Fan Shuanshi , Yao Zemin , Li Jing , Wei Xinli
Published: March 2012

In this paper, in order to solve the problem of intensified heat dissipation in high power electronic devices, a fast transient and intensified heat dissipation technology was put forward by comparing many heat transfer modes based on the analytical study on the existing technologies about heat dissipation at high heat flux density and about fast heat transport. This technology combined spray cooling technology with fast endothermic chemical reaction processes; we summarized the characteristics of media applicable to an environment with transient high heat flux density by comparing various parameters of many sprayed media in the spray cooling process. According to the energy balance of endothermic chemical reactions of relevant media, we determined the media (mainly carbon dioxide hydrate) applicable to the fast transient and intensified heat dissipation technology and presented the conditions for the chemical reactions. We analyzed the methods controlling the instantaneous chemical reaction rate and proposed the structural characteristics of the chemical reactor so as to ensure that the time for heat removal will be control to around 0.01 second. Thus, the problem of fast transient heat dissipation in high power electronic devices, etc. would be radically solved.
Test Research of the Leakage Performance in Steam Seal
Authors: Cui Qi , Zhang Zhao-he , Liu Wang-kou , Li Chang-jie
Published: March 2012

Steam seal is an important part in steam turbine, the leakage performance of seal has a significant impact on turbine efficiency. Research of seal is greatly emphasized with the development of design and manufacture technology, more professionals committed to the research and develop of new-type seal. Researchers from Shanghai power equipment research institute have conducted leakage performance test of different kinds of steam seal on the seal test bed. This paper introduce result of four kinds of seal, including labyrinth seal, honeycomb seal, touched seal and brush seal. The test analyzed blocked performance of different kinds of seals and concluded the suited scope of different seals.
The Simulation of Apparent Directional Emissivity in a Three-Dimensional Non-Isothermal Medium by the DRESOR Method
Authors: Cheng Qiang , Zhang Xiang-Yu , Wang Zhi-Chao , Zhou Huai-Chun , Wu Lv-Bin
Published: March 2012

The emissivity as a thermal property plays an important role required for heat transfer calculations and temperature measurement. In an isothermal purely absorption medium, the emissivity can be calculated by the formula, but no general formula for the emissivity will suit the system with scattering of medium and reflection of walls in a coal-fired boiler or an industrial heating furnace. In this study, a new approach was proposed to scale the apparent field directional emissivity by DRESOR method combined with two-color method in a three-dimensional non-isothermal participating medium with reflection of walls. The results obtained by the new method were compared with those calculated by the formula to verify the validity and accuracy of new method in an isothermal purely absorption medium. Then the new method was extended to examine the effect of absorption coefficient, scattering coefficient and reflection of walls on the apparent directional emissivity in the isothermal and non-isothermal cases. It is found that when there is scattering in the medium, the emissivity cannot be equal to the entity, even if the medium is optically thick. In the condition of walls with cold or low temperature, such as in the case of a coal-fired boiler, the apparent emissivity increases with the increase of absorption coefficient and reflectivity of walls, because radiation from hot media plays a dominated role in emissivity in this situation; Meanwhile, in the case of walls with high temperature, such as in the case of an industrial heating furnace in metallurgy or glass melting industry, the apparent emissivity decreases with the increase of absorption coefficient, because the emissivity is mainly determined by the wall radiation in this situation. And when scattering coefficient increases, the apparent emissivity decreases for all isothermal and non-isothermal cases.
Risk Evaluation Based on Run Vulnerability for Power Generation Equipment
Authors: Li Jianlan , Yang Tao , Wang Kun , Zhang Yanping , Huang Shuhong
Published: March 2012

Accurate risk assessment is an important scientific basis for maintenance decision making. Based on the reliability analysis, prediction technology and fault dialogue technology, this paper defines a risk index, run vulnerability, which considers factors of equipment status, consequences of potential failures and run trend, thus, it reflects equipment risk more comprehensive than that of traditional risk index do. This paper presents a new risk evaluation model based on run vulnerability for power generation equipment. The model process all factors affecting run vulnerability with the quantification of fuzzy rules, and constructs a three-dimensional surface run vulnerability map to achieve the risk assessment of power generation equipment. The example of feed water pump’s risk evaluation validates the model.