This study presents the void fraction â estimation by multi-layer long short-term memory with sparse model implemented in multi-layer current-voltage system (mlLSTM-SM-CV) in a vertical gas-liquid flow. In mlLSTM-SM-CV, the voltage vector _lVⁿ is measured at measurement time number n, in two layers l which are upstream-layer u and downstream-layer d, for each measurement pair k, under condition numbers c. SM determines which k is indispensable to â estimation resulting in sparse voltage vector _lVⁿ in l. Here, the upstream-layer sparse voltage vector _u^cVⁿ and downstream-layer sparse voltage vector _d^cVⁿ are reflected by the spatial distribution of bubbles in gas-liquid flow. mlLSTM-SM-CV system consists of two LSTM layers which are 1^st LSTM layer and 2^nd LSTM layer. In the 1^st LSTM layer, both _lVⁿ are arranged based on the time series of each l. In the 2^nd LSTM layer, arranged _lVⁿ are used for â estimation. For train dataset, both _lVⁿ were experimentally measured under c = 30 of the temporal-mean true void fraction ă_true calculated by the drift flux model under all c. For the test dataset, both _lVⁿ were measured under c = 18 of ă_true. Model parameters are optimized resulting in the best parameters of Sid = 64, M1 = 10, M2 = 50 with RMSE = 0.0134 and MAPE = 5.3%, respectively.

Mitsubishi Power, Ltd. (Mitsubishi Power) has focused on developing highly efficient power generation equipment to contribute to the worldwide efforts to reduce global warming and supply stable power. JAC gas turbine with turbine inlet temperature of 1650℃ was developed to meet the market needs for larger plant output and higher efficiency. For the purpose of achieving 1650℃ class gas turbine and high efficiency, key technologies such as enhanced air-cooled system, thicker advanced thermal barrier coating (TBC) and high pressure compressor were applied in JAC gas turbine. The verification of these technologies and long-term reliability of JAC gas turbine has been conducted by actual operation of JAC gas turbine at in-house verification combined cycle power plant, called T-point 2, since January 2020. This paper describes the verification results.

Crack growth tests were carried out in a superheated steam environment under a cyclic loading frequency condition in which crack propagation is expected with a transgranular and intergranular (IG) mixed mode. The oxide and precipitations that formed near the crack tip were analyzed by a transmission electron microscope. The crack propagated transgranularly through the grains, then turned to the IG path up to the crack tip. Cr-rich oxide, Al oxide, and a Cr-depleted zone beneath the oxide formed around the IG crack. Comparisons were made with a fully developed IG crack. The tendency to form more Cr oxide than Al oxide was also observed. No formation of a Cr-depleted zone was confirmed in the vicinity of the Cr oxide in the crack. A more detailed analysis of the grain boundary precipitation behavior, such as nucleation, coherency, and growth, is necessary. However, it was suggested that the depletion zone that developed near the grain boundaries could be the preferred pathway of the crack after its transition to the IG path.

Biodiesel as an environmental-friendly and renewable fuel assigns a great potential to substitution of petroleum diesel. Iodine value (IV) is an indicator to evaluate the degree of unsaturation (DU) of biodiesel. It reflects the biodiesel degradation and oxidation stability (OS) and also has an effect on viscosity, low-temperature flow properties, and the combustion performance. The main aim of this present work was to develop an accurate model based on RF-WOA-LSSVM algorithm to estimate biodiesel IV. The 14 fatty acid methyl esters (FAMEs) are involved variables for development of the models. The performance of developed RF-WOA-LSSVM model was compared using statistical criteria such as correlation coefficient (R²), root mean square error (RMSE) and mean absolute percent error (MAPE). It was determined that R² of RF-WOA-LSSVM model was 0.9989. In addition, the outcomes of the proposed model are compared with those from Knothe (2002)’s model indicating the great potential of the RF-WOA-LSSVM model to estimate the biodiesel IV.

Turbine vanes and blades are important components in steam turbines and gas turbines to convert thermal energy into mechanical energy. Since the turbine operates for a long period of time under a harsh environment, the turbine performance tends to deteriorate in a gradual manner due to increase in surface roughness or deformation due to wear, dent, chipping or thermal expansion. It is preferable from a viewpoint of developing a new type of real-time health monitoring technique of the turbine if one could detect any change in surface condition or shape of turbine vanes and blades from the information of the turbine performance deterioration. As one of the representative geometrical changes in turbine, the study focuses on the size of the trailing edge diameter of upstream turbine nozzle, emulating possible change in shape of trailing edge due to wear, chipping or deposition of foreign object or scale on the nozzle surface. A low-speed wind tunnel in Iwate University is used to investigate how and to what extent the change in trailing edge size affects the aerodynamic performance of the subsequent turbine blade.

Kawasaki Heavy Industries (KHI) has been promoting research and development projects for the future hydrogen society. The use of large amounts of hydrogen in power plants can induce large-scale hydrogen distribution and reduce hydrogen costs. For this purpose, KHI has developed hydrogen gas turbine technology for power generation. KHI has developed two types of hydrogen combustors for 1 MW class gas turbines: a water injection diffusion combustor (wet type) for reducing NOx emissions and a dry type low NOx combustor (dry type) applying micro-mix combustion technology. A demonstration project was also conducted to supply heat and electric power generated by a hydrogen gas turbine co-generation system to public facilities in a city area by installing them in an actual gas turbine. In this demonstration, both combustors achieved stable operation using hydrogen as fuel and sufficient performance for NOx reduction.

To understand crack growth mechanisms for structural components used in power plants, crack growth tests were conducted in steam and air environments at 600 °C at cyclic loading frequencies from 0.1 Hz to 0.01 Hz using a compact tension specimen, aiming to clarify the specific environmental effect on the crack growth rate (CGR) and the acceleration factor in steam and dry air environments. After the tests, the morphology and elemental distributions of formed oxides and precipitates on the fracture surfaces and at around fatigue crack tip region were analyzed scanning electron microscopy. The fracture surfaces of the crack that propagated in a steam environment were more undulated compared to those observed in a dry air environment irrespective of the loading frequency. All the examined crack tips were filled with oxides. The relationship between the CGR and the thickness of formed oxides were obtained. A linear dependence was exhibited in each loading frequency irrespective of the tested environments. It was revealed that the increase in the oxide formation was an acceleration factor of the CGRs.

To reduce greenhouse gas emission from gas turbine, the liquid ammonia direct spray combustor has been developed. Demonstration test used 2MW-class gas turbine was conducted, and performance of the combustor was evaluated. As a result, it confirmed that the supply system of liquid ammonia is simpler than that of gaseous ammonia, which is effective in saving footprint and shortening the start-up time of gas turbine. It found that liquid ammonia burns stably and unburnt NH₃ emission was suppressed up to a co-firing ratio of 70%. On the other hand, NOx concentration is higher than that of gaseous ammonia combustion, but it can be reduced below very low level by a standard NOx removal catalyst. N₂O concentration slightly increase with increasing liquid ammonia supply rate. It indicates that flame temperature decreases due to latent heat of vaporization of liquid ammonia. However, the effect of N₂O emission on greenhouse reduction ratio was minor, greenhouse gas reduced up to 68% comparing with natural gas alone firing. These results show liquid ammonia can be used for gas turbine fuel.

A temperature-controlled microextrusion printing technique is proposed to increase the aspect ratio of the deposited ink filament and applied to the fabrication of solid oxide fuel cells to enhance their performance by enlarging the electrode–electrolyte interfacial area. A terpineol-based anode ink is prepared with yttria-stabilized zirconia and nickel oxide powder and its viscosity and wettability to an anode support disc were experimentally studied under various temperatures. The results show that at low temperature the viscosity of the anode ink is reduced and the wettability of the anode ink to substrate is decreased. This suggests that it is beneficial to fabricate anode filament on a cooled anode-support disc in the sense of aspect ratio. A patterned anode-supported SOFC was fabricated by temperature-controlled microextrusion printing technique. The cross-sectional structure investigation showed that the aspect ratio of the deposited anode filament is increase from 0.16 to 0.28 by employing the temperature-control method, yielding a greater interfacial enlargement, this results in further improvement in the electrochemical performance of the cell.

In floating offshore wind turbine-generator systems, wind and wave variations cause platform motion and increase fatigue loads. A feedforward control based on the preview of the inflow wind speed to the wind turbine is combined with gain-scheduling feedback control of the generator speed to stabilize platform motion and reduce dynamic load variations at high wind speeds. In this feedforward control, the blade pitch is manipulated in response to the previewed wind speed so that the generator speed is maintained at the rated value. An aero-elastic-hydro-control coupled simulation using the developed feedback-feedforward controller is performed for a 5-MW floating offshore wind turbine-generator system. The simulation results under turbulent wind fields and irregular wave height variations reveal that the stabilization of the platform motion and the reduction in the dynamic load variations at the tower base and blade root, as well as the low-speed shaft, are achieved by using the spatial mean wind speed as the previewed wind speed.

Over the past three decades, solar energy has gained a lot of attention because of its energy potential and environmental-friendly aspect. To estimate its energy potential, most researchers use satellite approximation solar radiation data or imagery as their only data source, which is not sufficient as the images are taken high above the ground which results in the loss of the part of the resolution, and besides that, they also lack the hourly or daily variations, which is a critical component for an accurate estimation. This paper aims to provide the renewable energy research community with a low-cost and portable remote sensor for ground-based solar radiation and related data measurement. The remote sensor comprises a series of low-cost and accurate sensors, a single board computer, two Arduino micro-controllers, two Real Time Clocks, two mini-solar panels, an internet modem, two onboard batteries and six (6) relays, all interfaced in the Python Programming Language. The operation of the remote sensor is discussed in this paper along with a survey of its energy consumption. Data validation was done by comparing our recorded data with the Japan Weather Station data, and the result showed an accuracy of about 90%.

Film cooling is a complex flow and unsteady phenomenon due to the mixing of mainstream and coolant flow. Therefore, it is important to evaluate the unsteady behavior to improve the performance of film cooling. In addition, since the vane surface curvature and secondary flow have a significant effect on the film cooling, it is essential to measure the film cooling on the vane pressure-side surface as well as on a simple flat plate. In this study, unsteady film cooling was measured using PC-PSP (Polymer Ceramic Pressure Sensitive Paint), which is a fast response PSP prepared in-house. The PC-PSP was dynamically calibrated by a shock tube, and its response time was confirmed to be less than 500μs. PC-PSP measurements were performed on the vane pressure surface with blowing ratios (BR) of 0.50 to 2.0. The effect of mainstream turbulence intensity and cooling hole geometry were evaluated from mean film cooling effectiveness and time-average RMS of film cooling effectiveness.

This paper described the heating performance evaluation of an agricultural air-conditioning system using groundwater in winter and the reduction of the groundwater consumption for this system. This system consisted of an air-conditioning room for horticulture in a greenhouse and a water circulation system of groundwater. The pumped groundwater is passed through the heat exchange panels and then discharged as sewage. Although it has been confirmed that this system can be sufficiently heated in winter, it has an issue of wasting underground aquifer resources. Therefore, we have improved the system by water recirculation in the air-conditioning room to solve this problem. Results showed that the room temperature could be successfully maintained up to 20°C during the daytime when the outside temperature is 5°C, and above 5°C even during the nighttime when the temperature is below freezing in winter during a three days experiment. The experiment was conducted in Yamanashi prefecture. Whereas, the heating performance decreased when the circulating water was used at night. Therefore, we used groundwater from 10p.m. to 10a.m. The results showed that the room temperature at night was about 3°C higher than when using the circulating water in same outdoor temperature. Thereby, the consumption of underground aquifers per day would be reduced by 50% while maintaining sufficient heating performance. In addition, we measured the room temperature of the system when it was in operation and when it was not in operation, and found that the room temperature during the daytime when the system was not in operation exceeded 35°C despite winter conditions.

Increasing attention has been focused on hydrogen as a boiler fuel due to the carbon-free fuels. On the hydrogen combustion as the boiler fuel, the hydrogen burner should be applied the diffusion combustion to avoid the flashback because of the high burning velocity of hydrogen. Thus, the NOx reduction is important for hydrogen burner. This study investigated the NOx reduction by two-stage combustion of city gas and hydrogen mixed combustion. The lean premixed tubular flame of city gas / air mixture is formed on the first stage combustion. Combustion rate and air ratio of the first stage are 4 kW and 1.8. Downstream of the first stage combustor, hydrogen was injected at 7.4 m/s from three nozzles located around the combustion chamber. The stable diffusion flame of hydrogen was achieved in the swirling flow at the 3 kW of combustion rate. The NOx emission was suppressed to only 21.4 ppm because of the slow combustion reaction and the mild temperature rise. In the case of the single stage hydrogen diffusion combustion, the NOx emission increased to 289 ppm. The NOx reduction by using the two-stage combustion is effective for the hydrogen combustion.

Falling film-type evaporators are expected to be an alternative to flooded-type evaporators to reduce the amount of refrigerant charging needed. The required conditions for falling film-type evaporators are a wet evaporator surface and higher heat transfer through liquid film.

In this study, the falling film heat transfer characteristics of R1233zd(E) on two horizontally installed porous body tubes of different thicknesses were experimentally investigated. The horizontal tubes were 19.05 mm in diameter and 400 mm in heat transfer length. The experiment covered heat fluxes from 3 to 40 kW m^–2 with several different amounts of liquid flowing down. The heat transfer coefficient of a tube with 1 mm porous bodies thickness was higher than that of a tube with 2 mm porous bodies thickness. Thus, the porous bodies had an appropriate thickness.

The NO-reburning technology can significantly reduce the NOx emission during combustion. Although substantial progress has been made for NO-reburning chemistry in conventional flame combustion, the homogeneous NO-reburning mechanism in flameless combustion has not been systematically investigated. This paper performs a detailed comparative study between flameless combustion and conventional swirl flame combustion for NO-reburning by both experiments and numerical simulations. The finite-rate reaction is modeled by the eddy dissipation concept combustion model coupled with a well-developed skeletal mechanism for NO-reburning and the simulations are validated with experiments. To insulate the effect of NO formation, substantial amount of NO is added to the initial fuel and thus the NO-reburning can be investigated by assessing the NO reduction during combustion. For both flameless and swirl flame combustion, the initial addition of NO significantly increases the furnace temperature and the NO emission. Interestingly, the present study for the first time found that flameless combustion can increase the NO-reburning reaction by 30%, relative to the swirl flame combustion. The reaction pathway of the NO-reburning during flameless combustion is also analyzed. Moreover, with the equivalence ratio (Φ) increasing from 0.7 to 0.9, it is found that Φ plays an insignificant role in the NO-reburning during flameless combustion, although the CO formation is rapidly increased to extremely high when Φ > 0.83. Therefore, to minimize both the emissions of NO and CO and the exhaust gas flow rate in flameless combustion, an optimal Φ is found and this optimal Φ is about 0.83 for the present study. The present study reports the advantage of flameless combustion using low preheating temperature air for significant NO reduction by reburning and provides new fundamental understandings of the NO-reburning mechanism.

CRIEPI is developing a methodology for evaluating the contribution of operational flexibility of thermal power plants to the stability of the electric power supply as the share of intermittent renewable energy sources increases. This paper calculates the thermal efficiency during flexible operation of a 700 MW class ultra-supercritical coal-fired power plant. Coal-fired power plants generally need a longer time to change the flow rate of pulverized coal when their output power changes, which is responsible for the time lag in the load change of the plants. In order to minimize the time lag, the throttle valve of a high-pressure steam turbine needs to be partially closed and rapidly controlled to provide speed governing and load frequency control operation for stabilizing the frequency of the power grid. In this operation, the thermal efficiency of the power plant decreases owing to the steam pressure drop of the throttle valve in the high-pressure steam turbine. The thermal efficiency of the coal-fired power plant during partial load and partially closed operation of the throttling valve in a high-pressure turbine is calculated using a material and heat balance calculation method. The decrease in the efficiency is responsible for the cost increase in backup operation for the intermittency of renewable energies.

In this study, the MW plasma was applied to a non-catalytic reaction between CO₂ and CH₄ at atmospheric pressure. When CO₂ and CH₄ were fed to MW plasma of argon in a quartz glass tubular reactor with a packed bed of char made of wood, yields of ethylene, acetylene and other hydrocarbon products were recognized. The effect of different powers, ratio of methane to carbon dioxide was examined on the conversion and the yields and selectivity of those hydrocarbons. The results show that increasing the power promotes the reaction and increases the yield of hydrocarbons. Increasing the ratio of methane feed gas helps hydrocarbon yield, while reducing the ratio of methane increases the conversion rate of raw gas.

In this paper, solar power tower stations with different configurations of steam generators are proposed, and a detailed dynamic model of one-dimensional distributed parameters is established and verified. The response characteristics of the two systems under the disturbance of the main controllable variables are calculated, and the results are analyzed and compared. It is concluded that, compared with steam turbines, steam generation systems have significant thermal inertia, and different steam generation system schemes will have a significant impact on the dynamic performance of the system. For a natural circulation-driven system, the energy balance and power output are more sensitive to the hot salt mass flow rate, and mass balance would be adjusted by the feedwater mass flow. For a once-through-driven system, the energy balance is controlled by hot salt mass flow, but the mass balance and power output should be adjusted by the feedwater mass flow.

In recent years, water electrolysis technology that converts renewable energy into hydrogen has attracted attention to build a hydrogen energy system. Improving efficiency is essential for the future commercialization of proton exchange membrane (PEM) water electrolysis. One of the serious problems is that the staying of generated oxygen bubbles on the reaction site inhibits the water supply and significantly reduces the reaction efficiency. However, the mechanism of generation, growth, and detachment of oxygen bubbles in PEM water electrolysis cells has not been clarified. Therefore, it is necessary to understand these behaviors. In this study, the bubble behavior was observed on two types of anode porous transport layer (PTL) with non-treated and hydrophobic surface by using a high-speed camera. The oxygen bubble detachment speed was faster with a non-treated anode PTL than with a hydrophobic anode PTL. Moreover, a hydrophobic anode PTL hold more bubbles on the surface of PTL than a non-treated anode PTL. Therefore, it was assumed that the oxygen bubble behavior depend on the hydrophobicity of the anode PTL.

Pure electric vehicles have the advantages of wide energy sources, low emissions, and high efficiency.It is necessary to be improved of economic performance of electric vehicles due to the shortage of global energy. In this paper, fuzzy control theory is used to identify the driver's intention and control the torque output and energy recovery. With the goal of improving the economy of the whole vehicle, a combination of reference torque, compensation torque and torque limit under special conditions is designed to realize the economic optimization of torque output. At the same time, with the goal of recovering the energy in the braking process of the whole vehicle, a real-time energy recovery strategy has been developed to improve the economy of the vehicle. Based on the "Simulink" platform, a forward simulation model of the vehicle is established to simulate the running process of the vehicle. Establish a fuzzy control strategy model, and study the fuel consumption per 100 kilometers and energy recovery efficiency when the control strategy is adopted by simulating the operation of the entire vehicle. The results show that when using this control strategy, the actual vehicle test reduces the fuel consumption per 100 kilometers by 18.3% compared with the original vehicle control strategy. Through simulation under NEDC operating conditions, the fuzzy control strategy is obviously better than the original vehicle control strategy. It shows that using this strategy can effectively improve the vehicle economy and energy recovery efficiency, so as to achieve the purpose of energy-saving.

One of the most promising ways to reduce the environmental load associated with steam power generation is the improvement of thermal efficiency by increasing steam temperature. Ni-based alloys are usually used in structural components at temperatures exceeding 700°C, due to their excellent high-temperature creep strength. However, at these temperature ranges, the environment affect the damage caused by oxidation. Carbides and intermetallic compounds precipitate by aging and affects oxidation behavior of Ni-based alloys. In this study, oxidation tests using as-received and aged alloy 617 were carried out in supercritical water at 750°C. In the case of the as-received material, there was preferential formation of oxide on the grain boundaries. The amount of such oxide increased with the testing time. In the aged material, an aging precipitation phase accumulated along the grain boundaries. Additionally, the width and continuity of these surface oxides preferentially formed on the grain boundaries were larger than those in the as-received material. These precipitates were also assumed to continue growing further during the oxidation test, suggesting that the aging precipitation phase significantly affects the localized oxidation behavior.

The Mitsubishi Heavy Industries Group has successfully developed a new generation of high-efficiency steam turbines. The turbine is based on a reliable 33.7inch Low pressure end blade that has been in operation for many plants. In addition, the turbine performs high efficiency because that applied the latest analysis technology, which has been established based on the development technology and extensive operational experience accumulated over many years. Furthermore, the turbine is designed for sideward exhaust that discharges exhaust steam in the horizontal direction, making it possible to reduce the base height of the turbine as small as that of the axial exhaust. This makes it possible to significantly reduce building costs compared to conventional downward exhaust. In addition, performance and reliability have been verified under the same conditions as those of actual machines using the demonstration test facilities owned by our company. Regarding the last stage rotating blade, the pressure and velocity field were assessed by traverse measurement and blade vibration stress was assessed by strain gauge measurement. The predictions of the pressure and velocity field of the last stage rotating blade were in well agreement with verification test results.

The Winter-Kennedy method, as a common method to obtain turbine operation characteristics, is usually used in the index test of hydraulic turbine. IEC60041 clearly pointed out that the index test can only be used for determining the index efficiency of the turbine. However, the turbine model test may have been carried out during the design period of the hydropower project, and the Winter-Kennedy coefficients of the prototype have been obtained by conversion from the model test result. Therefore, based on the turbine model test result and initial Winter-Kennedy coefficients, we carry out a turbine index test, then with the actual size of the spiral case and the dimensions of differential pressure measuring points, establish the geometric model for the model runner through the Unigraphics NX software platform, and then use ANSYS CFX to simulate the internal flow of the turbine. From the turbulence model and prediction result, we can analyze and verify the Winter-Kennedy coefficients, then we can get the actual flow discharge and efficiency of the turbine. With an example we performed, we could find that the method has good accuracy, as it does not need absolute flow measurement, it is practical and applicable for similar measurements.

The present study numerically investigates the effect of biomass addition on the characteristics of coal moderate or intense low-oxygen dilution (Oxy-MILD) combustion. The eddy dissipation concept combustion model with a refined global mechanism for oxy-fuel combustion is used in the modeling. The detailed in-furnace velocity, temperature, species concentrations of O2, NO emissions are validated with experiments. It is found that the furnace temperature has resulted from the effect of a high amount of volatile. The effect of biomass moisture on the furnace temperature is insignificant when the mass fraction of biomass in the fuel is less than 30%. Moreover, the exhaust NO emission is notably decreased by 30-52% with increasing biomass addition due to the low nitrogen content and the intermediate NH3 of biomass fuel N. Furthermore, the fuel-NO is found to dominate the NOx production and it accounts for more than 97% NOx formation. The NO-reburning is also different at equilibrium components CH4 or CH2. The relative contributions of the coal-source and biomass-source nitrogen, as well as the volatile and char nitrogen conversion, are investigated and discussed in detail. The present study presents the advantages of MILD combustion for suppressing NO formation during the MILD oxy-combustion of biomass-coal fuel blends.

The present study deals with performance analyses of solid oxide fuel cell (SOFC) systems combined with various bottoming cycles. The SOFC considered in the study is fueled with natural gas reformed via direct internal reforming by anode gas recirculation. For bottoming cycles, subcritical steam cycle (SubC), supercritical steam cycle (SupC), ultra-supercritical steam cycle (USC), advanced ultra-supercritical steam cycle (A-USC), and the supercritical CO2 cycle (sCO2) are investigated. The results show that the energy efficiencies of the combined SOFC systems vary from 72.76 %LHV for the SubC to 74.83 %LHV for the A-USC steam cycles. Although 10.25 % points efficiency difference exists between the standalone SubC and A-USC steam cycles, the difference in overall system efficiency is only 2.07% points between the SubC- and A-USC- combined SOFC systems. On the other hand, the SOFC system with the sCO2 bottoming cycle achieved 74.28 %LHV, which is comparable to the A-USC combined system. This is attributed to the highly efficient turbomachinery for the sCO2 cycle. In addition to its performance, the sCO2 cycle also offers around ten times reduction in the size of the turbomachinery components. Finally, exergy analysis is conducted to understand the various exergy destructions occurring within the system.

The present study investigates the effect of ammonia addition on the oxidation of methane by both experiments and numerical simulations. The experiments are carried out in a spherical quartz jet stirred reactor at different reaction temperatures (T = 600−1300 K), equivalence ratio (Φ = 0.5−2), NH₃/CH₄ ratio, CO₂ mole fraction, and residence times (τ = 0.96−1.67 s).

Preliminary results show that by adding ammonia with the same concentration as methane, the minimum reaction temperature required for the oxidation of ammonia under the three equivalent ratios is lower than that without the addition of methane. When Φ=0.5, with the methane added, the temperature at which ammonia starts to oxidize has been advanced by 1300K compared to that no methane was added, and the NO produced finally by the former was almost twice as much as the latter. The two results described earlier show that methane promotes the oxidation of ammonia.

In order to explore the specific role of methane in the process of promoting ammonia oxidation, the simulation was performed using the psr module in the Chemkin Pro software. The parameter settings were as same as the experiment. The chemical reaction mechanism was simulated by the konnov06 mechanism developed by Konnov et al. in 2009. The macroscopic results showed similar results to the experiment. It could be found through the sensitivity analysis and the analysis of the rate of production that, when the Φ=1 and T=1350K, whether methane was added, the most sensitive reaction for the oxidation of ammonia to NO was H+O₂↔OH+O. The NH₃→NH₂→HNO→NO reaction promotes the ammonia oxidation process to the greatest extent. With the addition of methane, the H and OH radicals increase through two representative reactions which was CH₄(+M) ↔CH₃+H(M) and H+O₂↔OH+O, so the transformation through NH₃ to NO was promoted by the adding methane.

Coal firing power plant operated as one of main power sources in many countries must apply significant CO2 reduction technology immediately. Recently ammonia utilization has been investigated as one of effective solutions for CO2 reduction. IHI has developed ammonia co-firing burner and the related combustion technology, then ammonia co-firing burner for demonstration was designed and verified up to now. Ammonia combustion is expected NOx increasing when ammonia combustion in coal fired power plant due to much nitrogen content. Therefore, it is required for ammonia combustion to maintain NOx emission and unburnt combustible in ash simultaneously as same level as coal firing condition. IHI designed some ammonia co-firing burners for demonstration in commercial plant and conducted combustion testing in considering with actual plant operating condition. Co-firing rate of ammonia is set at 20% in calorific value basis. As the result of investigation by combustion testing and study for ammonia combustion at 20% co-firing, IHI found out the burner design condition for ammonia co-firing to maintain NOx and unburnt combustible at the all condition of plant operation and has developed ammonia co-firing burner for demonstration.

Ammonia is a promising carbon-neutral renewable energy source and can blend with hydrogen to increase its reactivity. Ammonia is also a fuel-nitrogen source and it is significant to suppress its fuel-NOx production. This study presents new experimental results on ammonia-hydrogen oxidation in a jet-stirred reactor. The effects of reaction temperature (T: 800 – 1400 K), equivalence ratio (Φ: 0.5 – 2.5) are experimentally investigated. The onset temperature of NH₃ oxidation is 900 K when mixed with equivalent H₂, which is 225 K earlier than that of pure NH₃. For NH₃/H₂ mixture, the NO begins to generate at approximately 1150 K, at which NH₃ is almost completely consumed. When T = 1200 K and 1400 K, the decrease of Φ promotes ammonia consumption and NO emission, and Φ =1.1 and 1.3 are recommended respectively to minimize NO and NH₃ emissions. The addition of H₂ contributes to the oxidation of NH₃, especially in fuel-rich conditions.

To actively control the operation of vapor-compression type air-conditioning systems for energy-saving, a hierarchical optimization framework of their operating condition was developed. The optimization problem to find the operating condition to minimize the power consumption subject to the satisfaction of the predicted air-conditioning loads results in a nonlinear programming problem. To improve the computational efficiency of the optimization, the operating condition is searched using a genetic algorithm at the upper level and the performances of the air-conditioning system with the searched operating condition are calculated using our steady-state cycle simulation at the lower level. A case study for a vapor-compression type air-conditioning system using R454C as the working refrigerant revealed a fine searching capability of the operating condition and high energy-saving performance relative to the conventional operating condition fixing the compressor inlet pressure and employing intermittent operation.

As the attention for energy conservation and environment protection increases, how to enhance the recovery of waste heat becomes a severe problem. This paper proposes a novel cycle configuration for waste heat recovery by introducing an ejector refrigeration cycle (ERC) to combined gas turbine (GT) and Kalina cycle (KC). The analysis results show that when refrigerant of ERC is R290, the total energy efficiency reaches its maximum value of 53.02%, while R600a leads to more system net power output than R290 and R1234ze.

Ground source heat pumps (GSHPs) use buried pipes to extract heat from the ground and to release heat to the ground. This heat can be used for air conditioning, underfloor and warm-air heating systems, and hot water heaters in dwellings. In ground source heat pumps, two types of systems are applied, namely, an indirect method and a direct expansion method. In the direct expansion method, a refrigerant transfers thermal energy through a primary loop without mediation. In the present study, the ground source heat pump that uses direct expansion method using the underground heat exchanger which used the narrow copper tubes directly inserted into a casing pipe filled with water. In the experiment, the borehole depth was set to 25 m and R410A refrigerant was used. The heat exchanger of an existing air conditioner was replaced with a underground heat exchanger.The ground heat exchanger was inserted into each of the three bore holes. The purpose of this study is to evaluate the performance of the GSHP using the direct expansion method in the cooling mode. The performance was evaluated by the Coefficient of Performance (COP), which is determined by the ratio of the amount of heat exchanged to the power consumption of the compressor. The experimental results showed that the average COP exceeded 8.2 in the cooling mode.

As a clean combustion technology, the moderate or intense low-oxygen dilution (MILD) combustion can achieve semi-uniform temperature distribution and extremely low NOx emissions. This technology can be combined with the oxy-fuel combustion to achieve MILD oxy-combustion, which can be operated at pressurized conditions to further increase the system efficiency. The present paper numerically investigates the effect of the operating pressure on the characteristics of MILD combustion of pulverized coal in both O₂/N₂ and O₂/CO₂ atmospheres. The finite-rate reactions are modeled by the eddy dissipation concept combustion model coupled with an optimized skeletal mechanism. It is found that in both two atmospheres, the high system pressure can enhance the chemical reaction kinetics and local heat release, thus promoting the devolatilization of pulverized coal and leading to a higher temperature zone. The high combustion reaction rates can also cause local hypoxia condition, thus CO generation especially under O₂/CO₂ atmosphere. The convective heat transfer gets more enhanced than radiation with the increase of pressure due to the higher diffusion rate of flue gas in furnace. NOx emission tends to decrease first and then increase under O₂/N₂ condition, while it continues to decrease under O₂/CO₂ condition with the increase of pressure.

Although substantial progress has been made for the development of reaction mechanisms for syngas combustion, most previous studies focus on air-fuel conditions. The chemical kinetics under oxy-fuel conditions is significantly different from air-fuel conditions due to the effect of high CO₂ concentrations. The present study proposes a new 16-species, 12-step reduced mechanism for syngas combustion and NO-reburning under both air and oxy-fuel conditions by systematical mechanism evaluation, reduction, and validation. Firstly, based on a large set of experimental data of syngas oxy-fuel combustion, including ignition delay times (180 data points in 5 datasets), laminar flame speeds (334 data points in 8 datasets), species concentrations (114 data points from a flow reactor and 558 data points from our jet stirring reactor), 16 existing frequently-used syngas mechanisms are evaluated for both the fuel oxidation and NO reburning. Secondly, the optimal detailed mechanism is thoroughly reduced by both skeletal and time-scale methods. Finally, the reduced mechanism is validated with the detailed mechanism as well as experiments in predictions of ignition, flame propagation, concentration prediction, and extinction. The relative errors between the reduced and detailed mechanisms are less than 10%.

This study proposes a new 64-species, 793-step skeletal mechanism and a new 41-species, 73-step reduced mechanism for propane combustion in both air- and oxy-combustion conditions. First, through quantitative error evaluation against 10 sets of experiments (996 data points in total), we find CRECK2003-2020 performs best in overall predictions among 10 widely-used detailed mechanisms in both air- and oxy-combustion conditions. Then, by applying directed relation graph with error propagation (DRGEP), directed relation graph with error propagation-aided sensitivity analysis (DRGEPASA), quasi-steady-state approximation (QSSA), and computational singular perturbation (CSP) in order, CRECK2003-2020 is comprehensively reduced (including both skeletal and time-scale reduction) in a wide range of air- and oxy-fuel conditions. Finally, the skeletal and reduced mechanisms are thoroughly validated. Relative to the published mechanisms, this specially developed reduced mechanism can not only well predict the propane combustion in both air- and oxy-fuel conditions, but also has minimal species and reactions.

Local heat transfer around a tube in in-line and staggered tube bundles were investigated in two-phase flows under adiabatic and atmospheric pressure conditions. The working fluids were air and water. The test section was vertical duct with inner dimensions of 90 × 90 mm2. In-line and staggered tube bundles, each containing five columns and eight rows, were employed for the measurements as the test sections. The tube diameter of each was 18 mm, and the pitch-to-diameter ratio was 1.25 for both bundles. The local heat-transfer coefficients were measured using a platinum wire electrode placed on a tube that could be rotated. Improvement of the heat transfer caused by liquid agitation in bubbly flow was remarkable for the in-line tube bundle, but not for the staggered tube bundle. In intermittent flow, the heat transfer was improved significantly for the both bundles. This is because the liquid phase is agitated by the reverse flow generated by the passage of large bubbles. However, this effect became smaller as the gas phase flow rate increased, especially for the staggered arrangement. It is considered that the lower the void fraction is, the more remarkable the improvement of the heat transfer coefficient is due to the liquid agitation by bubbles motion.

Intelligent methods have become powerful tools for modeling and optimization of complex systems. In this study, a Deep Belief Network (DBN) is employed to predict the current density of a Proton Exchange Membrane Fuel Cell (PEMFC), and a multi-objective optimization framework is proposed as well. Firstly, a single PEMFC CFD model is developed as the basic model, which is verified by the experiment data. Secondly, the DBN is employed to construct a performance prediction model of PEMFC. The DBN hyper-parameters are determined by cross validation method, and the DBN model is compared with other datadriven models to prove its superiority. Finally, a multi-objective optimization framework combining significant variables recognition, surrogate models and a multi-objective genetic algorithm is proposed. Results show that the DBN model predicts the PEMFC current density precisely, and the DBN prediction accuracy is superior to that of other intelligent methods. The multi-objective optimization framework can find the final Pareto front in only ten minutes, which improves the optimization efficiency significantly. This study provides efficient tools for PEMFC performance prediction and optimization, and can be a guide for engineering applications.

This article tells that S Group is facing the challenge of the new normal of quality management, through the establishment of a quality supervision team, structural optimization of the original inspection personnel and external inspection personnel, through selection, training and assessment, optimization The staff structure of the quality supervision and manufacturing team has been improved to better meet the needs of the group’s resource integration. At the same time, the establishment of the team was standardized and the follow-up quality team construction was put forward.

Solar cavity receiver has better thermal performance, but bears large thermal stress. To ensure the safe and efficient operation of the receiver, it is necessary to study its thermal performance and thermal stress characteristics. In this paper, the thermal model and mechanical model were built for the conical cavity receiver with built-in helical tube. Based on these models, the influence of flow directions (up-flow and down-flow) and direct normal irradiance (DNI) on thermal performance and thermal stress of the receiver were investigated by numerical simulation. The results showed that the thermal performance of the solar receiver in up-flow was always better than that in down-flow, but the maximum thermal stress was larger than that in down-flow. The increase of DNI can improve the thermal performance of the receiver, but it also increased the thermal stress of the receiver.

Secondary flow effect was brought by the U-bend in the heat exchange system. Under the effect of secondary flow, bubble behavior in subcooled boiling is more complicated, the flow process is obviously different from that of the straight pipe. It is crucial to investigate the influence of the U-bend on the two-phase heat transfer characteristics for the accurate prediction and design of the boiling heat transfer in the tube. Present work shows that: U-bend have a significant effect on distribution of mean void fraction and wall temperature. For onset of fully developed boiling, the bend with smaller curvature has less effect. The result of mean void fraction is under the combined effect of secondary flow and increase effect of onset of fully developed boiling. For the critical heat flux of U-tube, when position of bend is near the deterioration position of straight pipe, bend aggravated the deterioration, wall temperature increased more obvious. Also results show that and the critical heat flux in the U-tube is lower than that of the straight pipe.

Alloy Hastelloy-X was fabricated by a typical metal additive manufacturing process-selective laser melting (SLM), and the effects of heat treatment processes, forming orientation/position, powder’s O and N composition on microstructures and tensile properties of this alloy were investigated. The metallographic analysis results show both heat treatment (HT) and hot isostatic pressing (HIP) can facilitate the grains transformation from columnar to equiaxed ones and homogenize the microstructure, while HIP can further close cracks, pores and lead to precipitates formation along the grain boundary. As a result, HTed and HITed alloy have a higher ductility but a lower strength compared with as-deposited ones, for especially the HIPed alloy has an elongation up to 50%, far beyond the wrought HX specification value (12%). It is also revealed that both vertical and horizontal formed SLM alloy can reach to wrought HX’s tensile properties (refer to AMS 5536), but the horizontal one has a better ductility and slightly lower yield strength due to its grain orientation distribution. In order to keep the alloys’ strength and ductility reach to requirements of AMS 5536, the O composition should be below 100 ppm and N should be below 80 ppm

As the connecting part of the compressor blade-disk structure, the groove bears a variety of loads and is one of the most important parts, especially in the field of gas turbines. The strength analysis and structure optimization of the dovetail compressor blade disk were carried out. Based on the blade-disk model, using standard strength analysis, under the full load calculation of temperature, rotating speed, and aerodynamic pressure, the sensitivity analysis of structural parameters such as stagger angle, root length and root-groove location height was performed. Finally, combined with the sensitivity analysis, the optimization of the blade-disk structure was studied. The results show that reducing stagger angle of the blade root and increasing the height of the root groove position can effectively reduce the groove stress.

Understanding the wake impacts of a wind farm is critical for layout planning and turbine design. The main goal of this study is to model a Mass Flow Conserving Superposition (MFCS) and compare the Linear Wake superposition (LWS) while considering the wake and boundary interaction. This study factors the changes in thrust and momentum inside a wind farm cross-sectional area as the wake develops flows and interacts across five spans. We derived the mass flow conserving wake superposition approach that considers the mass continuity across the wind farm area to calculate the wake evolution between spans. The results for the wake profiles depict a quasi-periodic behavior that peaks at the last span in both the MFCS and LWS approaches. However, the MFCS approach has a more significant shift wake profile between spans than the LWS approach because it accounts for the thrust and boundary interactions changes. The MFCS approach's centerline wake velocity deficit reduces 0.47 to 0.34 m s⁻¹ while the LWS approach's centerline wake velocity deficit remains constant around 0.6 at m s⁻¹. A substantial shift in the MFCS approach's velocity deficit compared to the LWS approach can be attributed to changes in thrust and momentum.

It is proposed that the heat transfer method of two phase flow boiling is one of the most suitable solutions for solving the high heat flux in small spaces. And it is known that bubble elongation in an expanding channel produces a forward additional pressure caused by surface tension difference on both sides, which can relieve reverse flow. In order to utilize two phase flow effectively and stably, a kind of radial expanding micro heat sink (REMHS) has been designed for the flow boiling process. The thermal performances of REMHS are inspected with visualization experiments under low flow inertia. The average mass flux ranges from 12.0~110.5 kg·m^-2s^-1 and heat flux spans from 79.6~176.4 kW/m². The experimental results illustrate that flow instability is substantially relieved in REMHS with a gentle temperature fluctuation (below 1.5 K). The inlet flow status in REMHS is barely affected by the flow instability at the downstream. Besides, the wall temperatures of REMHS display a good symmetry, showing an even flow distribution among the radial expanding channel array. And the heat transfer coefficient increases with xout and reaches 28 kW·m^-2K^-1 at x_out=0.52, which proves that the design and proposal of this expanding micro channel heat sink is a effective method to stabilize the flow instability and make full use of the heat transfer capacity of two phase flow boiling.