In order to understand how the shape of the columnar oxygen carrier affect the component diffusion and complex interstitial flow, and ultimately affect the overall gas-solid heterogeneous reaction performance, a computational fluid dynamics (CFD) method was applied to numerically analyze the fixed-bed chemical looping combustion (CLC) process with columnar oxygen carriers of various diameter-to-height ratios. Results show that the larger the diameter-to-height ratio of columnar oxygen carrier particles is, the higher the airflow mean velocity and pressure drop in the packed bed reactor are. Compared with conventional cylindrical particles, thin lamellar or rod-shaped particles have larger specific surface area and shorter diffusion distance, which can alleviate the intra-particle diffusion limitation in porous oxygen carriers and thus accelerate the overall gas-solid heterogeneous reaction rate and oxygen carrier conversion. In addition, for the same diameter-to-height ratio, the thin lamellar particles exhibit greater diffusion and convective mass transfer rates, leading to a greater conjugate mass transfer capacity.

In order to improve the calculation accuracy of the main steam flow, a prediction model was established while the main steam flow based on the heat balance and flow balance calculation under the steady-state condition of the steam-water system was taken as the target value, and the input parameters were limited to the range of high-pressure cylinder. With the characteristics of almost no hysteresis among parameters caused by the high flow rate of steam in the high-pressure cylinder, the model trained with the data under steady-state conditions could be directly applied to unsteady working conditions. Finally,the proposed method was virified by an example. Results show that the method has a wide range of working conditions and is less disturbed by other factors. The actual case verifies the accuracy of the model which has practical application value in engineering.

When modeling rotor system, it is difficult to analyze high order of matrix equation due to coupling relationship between blade and disc. Therefore, blades were usually treated as equivalent additional moment of inertia, and the blade and disc were treated as a whole rigid disc. However, this modeling method would split the energy coupling relationship between the long blade and the rotor in the case of high speed, resulting in a sharp increase of model error. When the coupling of blade and disc was considered, the circumferential blade set in the finite element model was equivalent to an orthoisotropic rigid ring by taking the first-order critical speed and modal approximation as equivalent criterion, and the relation between the radius of the disc after equi-calibration and the original disc was obtained through theoretical derivation and calculation. Finally, ANSYS simulation comparison was carried out. Results show that equivalent method can significantly reduce the degree of freedom of blade-disc model and ensure the reliability of the equivalent model.

Considering the influence of the renewable energy fluctuation on the stability of regional comprehensive energy system, the configuration and optimal operation method of multiple energy storage systems were proposed. Firstly, the day-ahead and day-in dual time-scale optimization model of regional comprehensive energy system was established based on the wind/photovoltaic power fluctuation. Day-in optimization model took day-ahead operation scheme as a reference, and revised day-ahead optimization results. Results show that the economic index of active energy storage operation strategy is better than passive energy storage for the regional comprehensive energy system with multiple energy storage configuration. The economic index of multiple energy storage configuration is better than single energy storage.

The economic analysis of a 1 000 MW ultra supercritical coal-fired plant integrated carbon capture and storage (CCS) system was carried out using economic cost analysis. And the evaluation criteria of power supply cost, net present value (NPV), dynamic payback period and internal rate of return were taken as evaluation indicators to investigate the impact of coal price, carbon trading price, carbon tax, inflation rate and CO₂ price. Results show that the construction cost and energy consumption of plant integrated CCS system (PICCS) are relatively high, and the total investment and power consumption rate are 24.54% and 19.31% higher than that of the conventional unit. The power supply cost of the conventional unit is 0.307 5 yuan/(kW·h). The power supply cost of the PICCS is 35.87% higher than the conventional unit. The cost of CO₂ emission reduction is 171.47 yuan/t. The net present value of PICCS is 13.806 billion yuan, which is 2.23 times than that of the conventional unit, meanwhile, the dynamic payback period of the PICCS is 4.15 years, which is 1.94 years earlier than that of the conventional unit. Considering carbon tax, carbon trading and CO₂ sales simultaneously, the power supply cost of the PICCS is 0.196 4 yuan/(kW·h), which is 43.17% lower than that of the conventional unit. After the establishment of carbon trading, carbon tax policies and the CO₂ recycling market, the PICCS is more profitability than the conventional unit.

In order to study the heat transfer characteristics of flow boiling in narrow channels, the single-sided steam heating experiments were carried out in a vertical narrow rectangular channel. The influences of mass flow rate, inlet subcooling rate were analyzed, and the prediction equation of flow boiling heat transfer suitable for vertical narrow rectangular channels was established. Currently, most empirical formulas ignore the influence of inlet subcooling on bubble growth process, which results in low accuracy in predicting flow boiling heat transfer. Considering the size limitations of narrow rectangular channels and the influence of fluid surface tension, a new prediction model was established by introducing correlation coefficients. Results show that with the increase of mass flow rate or the decrease of inlet subcooling, the wall temperature increases first,then decreases and tends to be consistent finally. The decrease of the inlet subcooling will greatly improve the heat transfer coefficient, while the mass flow rate has little influence on the heat transfer coefficient. When the inlet subcooling is high, the influence of the mass flow rate is further weakened. The new predicted model could better predict the flow boiling heat transfer coefficient of narrow rectangular channel within the experimental conditions.

It is difficult to determine the fault type due to the strong nonlinearity characteristics of early vibration signal for the rolling bearing. Taking correlation kurtosis and Lyapunov index as comprehensive objective functions, the optimized variational mode decomposition (OVMD) parameter optimization method was proposed.The minimum value of comprehensive objective function was searched to determine the optimum combination of modal decomposition number and penalty factor. Noise reduction and feature extraction were realized to reconstruct the fault signal. The phase-space reconstruction method was adopted to restore the nonlinear structure of the system dynamics, and the pure signal was extracted by convolutional neural network (CNN).Results show that OVMD can effectively reduce noise and eliminate irrelevant components. After the reconstructed signal is learned by CNN, the attractor trajectories are shrunk, the signal nonlinearity is reduced, and the faults are separated. The OVMD-CNN diagnosis model has good robustness and generalization, which can realize the intelligent diagnosis of bearing faults.

In order to solve the problem of high exhaust temperature of a lignite boiler, the integrated system of steam turbine and boiler was designed. Through optimizing the design scheme of boiler heating surface, a pre-economizer was arranged upstream of the economizer. The inlet of the shunt economizer was the low temperature and high pressure water supplied from the upstream of a high pressure heater, and the lower exhaust temperature could be obtained by adjusting the design of air preheater according to the corresponding change of heat balance. Finally, the boundary conditions of an Indonesian lignite unit were calculated. Results show that when the exhaust temperature decreases from 171 ℃ to 107.8 ℃, the boiler efficiency is increased by 3.96%, but the heat consumption is increased by 99.12 kJ/(kW·h). Comprehensive coal saving is the common problem of all lignite units at present. The solutions in this paper have good guidance and reference significance for similar projects.

A multi-model γ incremental stepped generalized predictive cascade control strategy based on the feedforward of the inlet NO_x predicted value was proposed. Firstly, the γ-SGPC-PID cascade controller under three typical working conditions was designed, then the global controller was constructed by fuzzy gain scheduling, and finally the feedforward-feedback SCR denitration control system was constructed by taking the predicted value of inlet NO_x based on VMD-ARIMA as feedforward. Results show that the feedforward-feedback control system can adjust the ammonia mass flow rate accurately, reduce the fluctuation of NO_x mass concentration at the outlet, and improve the quality of SCR denitration control system under variable working conditions.

Under the background of zero discharge of wastewater in the whole plant, the scale inhibitors entering the desulfurization system with circulating sewage will prevent normal crystallization of gypsum. Gypsum crystallization experiments were performed with different scale inhibitors to explore the influence of scale inhibitor performance on nucleation characteristics of gypsum. Results show that scale inhibitor can prolong the induction time of gypsum crystallization and inhibit gypsum nucleation. The higher the mass concentration of scale inhibitor is, the more difficult the gypsum nucleation is. When the mass concentration of scale inhibitor is 10 mg/L, the induction time of gypsum crystallization increases by 17% to 48%, and the nucleation inhibition index ranges from 7% to 17%. The nucleation inhibition index of scale inhibitor F is minimum, and its nucleation inhibition effect is the weakest. After adding scale inhibitor D, the gypsum crystals appear as flakes, indicating that the complexation and dispersion performance of scale inhibitor D is strong, which seriously inhibited the gypsum nucleation. After adding scale inhibitor F, the gypsum crystals present as adhesive flakes and needle, indicating that the distortion performance of the scale inhibitor F is strong, and the nucleation is less affected. According to the morphology of gypsum samples with scale inhibitor added after crystallization, scale inhibitor F has the strongest distortion performance. Scale inhibitors with strong distortion performance have weak inhibitory effects on the gypsum nucleation process, and have a small nucleation inhibition index, which is more suitable for the requirement of the desulfurization safety operation.

To solve the issue of difficult hydrogen storage and transportation, and to achieve efficient and clean utilization of methanol fuel, a combined heat and power system coupling fuel cell and organic Rankine cycle based on methanol reforming was proposed. In the proposed system, the reforming reaction of methanol with water under mid-low temperature condition yielded hydrogen-rich syngas. The chemical energy contained in hydrogen-rich syngas was converted to electricity in the fuel cell. The high temperature exhaust gas from the fuel cell could be used to heat the air and as a heat source for the organic Rankine cycle, and energy cascade utilization was achieved. Under the system steady operation condition, energy, exergy and economic analyses were carried out for the new system. Results show that the total output power of the new system is 147.372 kW, the system efficiency is 51.29%, and the system exergy efficiency is 40.56%. The dynamic payback period of the new system is 4.97 years. With a 15-year life span, the net present value is 1.279 4 million yuan.

In order to facilitate the study on the effects of different structure parameters and working conditions on the fouling characteristics in multi-layer rotary air preheaters, and solve the difficult monitoring problem of layered fouling in preheater, a mathematical model for layered fouling monitoring of ash accumulation was established based on the finite difference method. Meanwhile, the rationality of the model was analyzed by a certain rotary air preheater with three sectors. Results show that as the measured temperature of each layer increases from 341 ℃, 241 ℃ and 104 ℃ to 367 ℃, 303 ℃ and 130 ℃, the clean factors decrease from 1 to 0.1, which indicates that the weakening of heat transfer is gradually aggravated. Accordingly, the deviation of the outlet temperature from the clean state increases from 0.8%, 2.6%, 2.8% to 7.8%, 26.1%, 25.2%. These data reflect that when fouling in a certain layer becomes more severe, the temperature difference between inlets and outlets decreases, indicating that the heat transfer capacity of the heat storage element is weakened. The proposed model has a great adaptability and can be applied to rotary air preheaters with any numbers of sectors and layers. A calculation can be completed within 2 s. If the data transmission delay of the power plant is ignored, the layered and real-time fouling monitoring of rotary air preheaters will be realized through the model.

Based on the measured earthquakes in China, the structural response and local damage characteristics of a 10 MW single-pile onshore wind turbine under earthquake and turbulent wind loads were studied. The effective earthquake duration was calculated using Arias intensity, so as to conduct time-domain analysis of wind turbines, a multi-physical field model considering turbulent wind, earthquake and soil structure coupling effects was constructed by using the shell element refined finite element model, and the structural dynamic research was conducted on a 10 MW single-pile onshore wind turbine. Results show that turbulent wind load and seismic load are the determining factors affecting the forward and backward displacement and lateral displacement of the wind turbine tower top, respectively. Different seismic loads lead to seismic-induced structural buckling modes change.

The steam generator in the Solar Two molten salt solar tower power plant was taken as the research object, the dynamic mathematical model of the steam generator was established based on the conservation equations of mass and energy. Based on the dynamic mathematical model, by analyzing the dynamic characteristics of the steam generator with disturbances at water side and molten salt side, the response curves of the outlet parameters and time constant of the steam generator were obtained. Results show that it takes 205 seconds for the steam generator to reach a new equilibrium after disturbance. However, due to the large heat capacity on the steam side, the response of parameters to disturbance is slow, and the quality of steam affects the safety and economy of the unit. Compared with molten salt, water and steam have higher specific volume and liquid storage capacity, the response speed of parameters at water side is much slower than that of molten salt side.

To analyze the unit exergy cost of various output energies in cogeneration systems, an exergy cost analysis method based on reversible work ratio was proposed. The unit exergy costs of different forms of energy output by a thermodynamic system in a reversible process were equivalent, and were equivalent with the mean unit exergy cost of input energy. Exergy cost balance equations was established based on the hypothesis and reversible work ratio—the ratio of work to the total energy in a reversible process, and the unit exergy costs of output energies of a gas turbine heat and power cogeneration system was analyzed. The exergy cost of a natural gas distributed energy system was calculated.Results show that the exergy cost is higher when the energy quality is higher.

In order to improve the efficiency of solid oxide fuel cell (SOFC) combined system and reduce carbon capture energy consumption, a combined system based on SOFC, gas turbine (GT), steam turbine (ST), organic rankine cycle (ORC) and ammonia absorption refrigeration cycle was proposed to liquefy and recover CO₂. A SOFC ontology model was built and verified by Aspen Plus software. By inputting thermodynamic parameters under design condition, the effects of current density, fuel utilization rate and steam-carbon ratio on the performance of the SOFC and the combined system were studied. Results show that under design conditions, the electrical efficiency of the SOFC, the combined system and the power-cooling supply efficiency are 55.5%, 76.5% and 92.6%, respectively. Compared with the existing systems, each efficiency of the proposed system has been improved. When current density increases to the limit current density, the concentration polarization loss increases rapidly, which has a negative impact on system performance. With the improvement of fuel utilization rate, work-cooling ratio decreases, while each efficiency shows a trend of first increasing and then decreasing. When the steam-carbon ratio is 2, the electrical efficiency of the combined system and the power-cooling supply efficiency reach the highest, which are 78.04% and 93.2% respectively.

In order to improve economy of the waste-to-electricity system while comprehensively utilizing waste resources, two novel design schemes combining anaerobic fermentation and incineration were developed. Taking a waste incineration plant as research case, the fluid thermodynamic parameters and the power generation efficiency of coupling system utilizing anaerobic fermentation biogas were simulated by EBSILON. The economy of the proposed system was evaluated and the reasons for the improved energy utilization were analyzed by thermodynamic method. Result show that waste-to-electricity efficiency of the two schemes is raised by 6.59% and 14.89% respectively compared with the example system while the biogas-to-electricity efficiency can reach up to 31.82% and 45.66%, and the dynamic payback period is only 4.01 years and 2.77 years.

In order to reveal the mechanism of the medium flow and viscosity in the atomization process of pressure nozzle, a simulation approach combining large eddy simulation (LES) and volume of fluid (VOF) was adopted to explore the flow in the nozzle, and the effects of inflow Reynolds number (Re) on flow coefficient, atomization angle and particle size were analyzed. Results show that the flow coefficient of the nozzle and the liquid film thickness at the nozzle outlet decrease with the increase of Re. When Re is high, the effect of inflow Re on the flow coefficient is less.With the increase of Re, the atomization angle of the nozzle increases. When Re is less than 1 000, the increase of atomization angle is more obvious with the increase of Re. For a certain Re, the atomization angle is almost equal. When Re is higher, the Sauter mean diameters (d_SMD) of atomized droplets are more uniform, and the distribution of the atomization particle size is closer to the characteristics of Rosin-Rammler (R-R) function.

To study the fluctuation suppression strategy of concentrated solar power (CSP) in Brayton cycle with storage battery on photovoltaic (PV) output power, a PV-CSP with air Brayton cycle and battery combined power generation system was established. The PV worked as the main power generator, and the CSP and battery served as the supplementary power to stabilize the PV output power fluctuation. Four operation strategies were proposed for the efficient operation and load variation of the CSP micro gas turbine system. Results show that all the four strategies can reduce the PV output power fluctuation to some extents. Moreover, with the same battery capacity, strategy 2 causes the smallest PV output power fluctuation, while strategy 3 results in the lowest maximum battery charging power. As the battery capacity increases, the PV output power fluctuations of all strategies decrease, and the power fluctuation suppression abilities of strategy 2 and strategy 1 become closer to each other. When the ratio of heat and electricity storage is 3∶4, the output power fluctuations of the four strategies are reduced by 80.7%, 88.3%, 50.5% and 55.1%, respectively, compared to the PV-only case.

Wind turbine gearbox is an important component that is prone to failure, and its maintenance cost is high, so it is necessary to monitor its real-time status. Aiming at the problem that the integrated K-nearest neighbor (KNN) algorithm was not sensitive to random sampling, an improved integrated KNN model based on regular sampling was proposed. Firstly, the distance correlation coefficient was used to select variables. Then the variables were sorted based on normalized mutual information and used for regular sampling to construct sub training sets. Finally, the threshold was set to analyze the real-time residual based on the statistical process control method, and the health of gearbox was monitored according to the health rate curve. This method was valified by the actual data of a wind turbine. Results show that the proposed method significantly improves the estimation accuracy of the model, which is better than the conventional ensemble KNN model, and can warn the early failure of the gearbox.

Aiming at improving the economy of cogeneration unit coupled absorption heat pump, the thermal model of the unit was built based on Ebsilon; the influence of internal and external parameters on the heat pump efficiency and thermal economy was analyzed using the control variates method; the research was conducted combined with the actual operation data of a 2×350 MW cogeneration unit. Results show that under the rated heating condition, the extraction steam of the coupled absorption heat pump can be saved by about 18% and the thermal efficiency of the unit can be increased by 1.2% compared with that of the heating network heater only; The return water temperature of the heat supply network increases by 10 K, resulting in that the performance coefficient (C_OP) of the heat pump decreases by about 0.1% and the thermal economy of the unit decreases by about 4%. The reduction of the thermal economy of the unit can be reduced by increasing the heat supply load of the heat pump; Increasing the temperature of the low-temperature circulating water increases both the C_OP of the heat pump and the thermal economy of the unit. When the difference between the return water temperature of the heat supply network and the temperature of the low-temperature circulating water is less than 10 K, the effect of improving the heating performance is not obvious; When the outlet steam temperature of the heat pump generator increases by 10 K, the C_OP of the heat pump increases by 18.9%, but the steam consumption of the unit increases by about 1%. Therefore, by adjusting the operating parameters of the heat pump, more waste heat of circulating cooling water can be extracted, the output of the heating network heater can be reduced, and the cold end loss of the unit is reduced.

In terms of instability and difficulty in timely intervention during the combustion adjustment process, based on the characteristics of a certain type of gas turbine combustion adjustment process, an improved particle swarm optimization (PSO) algorithm was used to optimize Elman neural network. The parameters that affect the operating state of the unit were used as input variables, and the parameters that characterize combustion stability were used as output variables, thereby establishing an improved PSO-Elman neural network model. Result shows that the mass flow rate of the duty air, the opening of the compressor inlet guide vanes (IGV) and the first stage adjustable stationary blade of the compressor (CV1) have a significant impact on combustion stability. Compared with Elman neural network, the improved PSO-Elman neural network model has better reliability. The proposed model can well track the change characteristics of parameters during combustion adjustment, which can be used to predict possible combustion instability in advance, and solve the technical problems related with limitations and poor flexibility in the test process.

Aiming at the problem that the conventional drag force model is difficult to accurately predict the gas-solid interphase drag force, considering the calculation accuracy and model generality, the EMMS-1M drag force model with mesoscale correction coupled with the two-fluid model was chosen to simulate the effects of particle size and inlet gas velocity on the cold-state fluidization and thermal chemical reactions in the air reactor. Results show that:the decrease of particle size and increase of inlet gas velocity result in uniform bed gas pressure distribution; the bed axial particle concentration decreases, the bed particle mixing return phenomenon can be weakened, and the axial velocity of particles increases. Increasing temperature promotes the reaction to proceed positively and increases the oxygen conversion rate. The increase of inlet gas velocity leads to uniform particle distribution in the bed and complete gas-solid mixing, which promotes the chemical reaction. However, too high inlet gas velocity carries out many particles, and the residence time in the bed is reduced, which is not conducive to the occurrence of the gas-solid chemical reaction.

Based on the actual operating data of a coal-fired boiler in a 1 050 MW ultra-supercritical unit, a random forest (RF) algorithm was used to establish a prediction model for NO_x concentration in the flue gas at the furnace outlet of the coal-fired boiler, and Bayesian optimization (BO) was used to optimize the hyperparameters. Then the BO-RF model was compared with the grid search optimized RF model (GSO-RF). In order to better evaluate the prediction model, the established BO-RF model was compared with the current common error Bayesian optimized back propagation neural network (BO-BPNN) model and Bayesian optimized least square support vector machine (BO-LSSVM) model, using the average absolute percentage error δ_MAPE and the coefficient of determination R² as evaluation indicators. Results show that the prediction accuracy of the BO-RF model is higher than that of the GSO-RF model, and the δ_MAPE of the BO-RF model is 1.478%, the R² is 0.916 2, which are better than the prediction results of the BO-BPNN model and the BO-LSSVM model, indicating that the BO-RF model has higher prediction accuracy and better generalization performance.

In order to realize the economical and low-carbon operation of the integrated energy system, an integrated energy system optimization model considering the stepped carbon trading mechanism was proposed. Firstly, the goal was to minimize the annual operation and maintenance costs of the system and investment costs. An energy system capacity optimization model was established considering multiple load demands. Secondly, the typical daily cooling and heating loads were selected based on the k-means clustering method and the average method. Finally, the minimum system operation and maintenance costs and carbon trading costs were targeted to analyze the impact of different benchmark carbon prices on system operation, carbon emissions and economic efficiency, and conducted a detailed analysis on a typical day. Results show that the introduction of the stepped carbon trading mechanism into the integrated energy system can effectively reduce carbon emissions and improve the economy of the system, especially in the heating season, which can have a significant impact on the system with a lower benchmark carbon price.

The mathematical model and control logic of energy release process in compressed air energy storage (CAES) were studied. The dynamic simulation model of CAES energy release process was established using MATLAB/Simulink platform for the simulation of start-up process, quasi-synchronized grid connection process and off-design condition process. The variation of operating parameters and efficiency under multi conditions were analyzed. Results show that within the power range of 200-300 kW, the expander efficiency is in the range of 75%-88%, and the exergy efficiency is in the range of 73%-84%.

Taking the packed bed phase-change thermal storage tank as the research object, a local non-thermal equilibrium model of porous medium was established without mesh discretization of each encapsulated particle., by using the binary nitrate composing of 60%NaNO₃ and 40%KNO₃ as the heat transfer fluid, and the mixed molten salt of 59.98%MgCl₂, 20.42%KCl and 19.6%NaCl as the phase-change material. The heat storage performance of packed bed phase-change thermal storage tank was numerically studied,and the influence of turbulence and particle structure on heat storage performance of the thermal storage tank was analyzed. To improve the heat storage performance of thermal storage tank, non-uniform particle distribution was adopted and compared with the uniform particle distribution. Results show that compared with the uniform particle diameter of 0.025 m and 0.015 m, the complete melting duration of phase-change material with the particle diameter of 0.025 m at the upper end and 0.015 m at the lower end decreases by 3.81% and 1.90%, respectively.

In order to study the impact of participating in carbon trading on the operation strategy of multi-source cogeneration system combined cooling heating and power, taking an industrial park as the research object, a multi-source cogeneration system including energy storage was constructed. Taking the electrothermal characteristics, climbing power limit of combined heating and power (CHP) and supply-demand balance as constraints and the annual comprehensive cost including operation cost and carbon transaction cost as optimization objectives, the effects of parameters including the proportion of photovoltaic utilization area (x) and the heat distribution coefficient of waste heat boiler input absorption chiller (μ) on the comprehensive cost and carbon emission of the system were studied. Results show that photovoltaic equipment has a greater impact on the system economy than solar boiler. The best economy is obtained when x is 90%. The ranges of μ in four seasons are[0,1],[0.74,1],[0,1],[0,0.21], which should be valued reasonably according to season and demand.

The effects of operating parameters, such as steam load, circulation ratio and water level, on the performance of curved-arm steam water separator for steam generator of CANDU6 reactor were calculated and analyzed by computational fluid dynamics (CFD) technology. Euler two fluid model and three sizes of the water droplets, which were 100 μm, 200 μm and 300 μm respectively, were used to simulate the two-phase flow of steam and water in the separator. Results show that the influential trend of operating parameters on separation performance is basically identical for all the three droplet sizes, the droplet size independence law applies. When the droplet size is 300 μm, more accurate separation efficiency and pressure loss value can be obtained. As the steam load is increased, the separation efficiency increases and the outlet humidity decreases, while the circulation ratio and the water level result an opposite influential trend. The pressure loss increases as steam load or circulation ratio increases, but the pressure loss coefficient decreases, the influence of water level on pressure loss and pressure loss coefficient can be ignored.

Combined cooling, heating and power (CCHP) system can realize efficient cascade utilization of energy, which was conducive to achieve the goal of "carbon peak and carbon neutrality". Based on the exhaustive search method, a building-level CCHP system was constructed including gas-fired cogeneration system, gas-fired boiler, electric chiller, absorption chiller and water-water heat exchanger. Taking three typical buildings as research objects, the capacity configuration, system operation parameters, economic performance and emission reduction of the CCHP system were studied and the corresponding sensitivity analysis was carried out. Results show that compared with their production systems, the cost saving rates of commercial buildings, office buildings and residential buildings are 21.76%, 16.72% and 9.17%, the carbon dioxide emission reduction rates are 15.80%, 10.42% and 4.41%, and the system energy prices are reduced by 39.85%, 49.04% and 41.29%, respectively. The research results can provide a reference for the optimization of the CCHP system.

Considering the insufficient primary frequency regulation capability of nuclear power unit, the flywheel energy storage array was used to assist its primary frequency regulation. The 1 MW/250 kW·h flywheel energy storage unit model and 4 MW/1 MW·h flywheel energy storage array were established, so as to analyze their charge and discharge characteristics. In order to improve the integral power contribution index of the primary frequency regulation of nuclear power unit by twice, the capacity configuration method of flywheel energy storage array was propose based on particle filtering method. According to the historical operation data of a nuclear power unit with installed capacity of 1 250 MW, the simulation was performed to verify the proposed method. Results show that compared with the capacity configuration method of flywheel energy storage array using the ensemble empirical mode decomposition (EEMD) method, the proposed method shows better performance of frequency regulation.

A solar-aided municipal solid waste incineration power generation system has been proposed for advancing the waste-to-energy and solar thermal energy technologies. This system could use the heat obtained by the parabolic trough collectors to reheat the working steam in the incineration plant and improve the steam parameters. A waste-to-energy power plant with the waste treatment capacity of 550 t/d and net generating power of 8.97 MW was used as a reference unit, coupled with solar assisted reheat system with input of 5.91 MW solar energy. Thermodynamic and sensitive analyses were conducted to examine the performance of the proposed system under various solar conditions and reveal the performance enhancement mechanism. Results show that compared with the reference system, the proposed system improves the ideal steam cycle efficiency by 0.96% and net generating power by 1.36 MW with solar-to-electricity efficiency of 22.91% under the design condition. The proposed system performs well for most of the year. And the annual solar-to-electricity efficiency of 17.45% is achieved. The levelized cost of electricity of the proposed system is 0.757 Yuan/(kW·h), which is economically feasible.

Based on the life cycle assessment method, inventory data of hardwood used in direct combustion power generation was established. The ILCD Midpoint+ method was used to evaluate six environmental impact types, and the main pollutants causing various environmental impacts were analyzed. At the same time, multiple power generation methods were compared in terms of six environmental impact types. Results show that the environmental impact of the direct combustion of hardwood for power generation mainly comes from the planting process and power generation process, with global warming mainly coming from the power generation process, and the other five types of environmental impact mainly coming from the planting process. Nitrogen oxide, sulfur oxide, ammonia and greenhouse gas are the main factors causing environmental impact of each unit process. In terms of environmental impact, compared with hydropower, wind power, and photovoltaic power generation methods, hardwood direct combustion power generation has certain disadvantages, but its environmental impact is much lower than traditional fossil energy power generation methods.

Using the method of numerical simulation, the influence of the deviation of the primary air volume of the circulating fluidized bed (CFB) boiler on the fluidization uniformity was studied, the criterion for the material layer thickness deviation of the air distribution uniformity was proposed, and then the improved test method of the air distribution uniformity of the circulating fluidized bed boiler was proposed. Results show that when the deviation of the inlet flow on both sides of the primary air chamber exceeds 10%, the fluidization uniformity of the bed material is worse. At this moment, it corresponds to the maximum allowable deviation of the air distribution uniformity, namely the difference between the maximum and minimum bed material heights should not exceed 20 cm, and the maximum deviation between the height of the bed material and the average height should not exceed 12 cm.

According to the overall shutdown condition and operating load data of power plant units over the past three years,the relationship between flue resistance and unit load was analyzed. Based on the duration of shutdown, flue resistance before shutdown, average relative humidity and average temperature, multiple linear regression analysis was used to analyze main factors affecting the increase of flue resistance during unit shutdown. Results show that the number of shutdown days has a significant positive impact on the flue resistance, and there is a significant negative relationship between flue resistance before shutdown and the increase of flue resistance. Average relative humidity and average temperature show little positive impact on the increase of flue resistance. When the shutdown time reaches 30 days and the relative humidity reaches 49%, the flue resistance of the unit is likely to increase during the shutdown period.

A type of supercritical carbon dioxide truncated cone cavity heat receiver was designed and developed for the solar energy disk concentrator. The optic-thermal model of the cavity heat receiver was established, and the optic-thermal characteristics of the cavity heat receiver were analyzed by Monte Carlo ray tracing method. Based on the related theory, the thermal boundary conditions were introduced as the input parameters to import into Ansys Fluent software. CFD simulation was carried out to study the optical characteristics and flow heat transfer characteristics of the cavity heat receiver. The outlet temperature, pressure drop, optical efficiency, thermal efficiency and losses of heat convection, radiation and conduction were obtained under different inlet temperatures (100-200℃) and different solar radiation intensities (400-1 200 W/m²). Results show that the optical efficiency of the cavity heat receiver remains basically unchanged under different solar radiation intensities. The influence of solar radiation intensity on the thermal efficiency of cavity heat receiver is not significant. The higher the inlet temperature of the working fluid is, the lower the thermal efficiency of the cavity heat receiver is. In the heat losses of cavity heat receiver, natural convection heat loss is the largest, followed by radiation heat loss and heat conduction heat loss.

To explore the influence of rotary kiln air inlet modes on hazardous waste combustion, Fluent software was adopted to study the combustion process in a rotary kiln. The effects of three air inlet modes including double-channel swirl air inlet mode, single-channel swirl air inlet mode and annular air inlet mode on temperature field, component field, velocity field and burnout rate were simulated. Results show that under the double-channel swirl air inlet mode, the average temperature of the cross section of the rotary kiln is the highest, O₂ concentration at the tail of the kiln is the lowest, and CO₂ concentration is the highest while the concentration of CO is reduced to 0. In this condition, the gas turbulence in the kiln and the speed of hazardous waste are both the highest, the materials are completely burned out, and the coke conversion rate is the highest. Under the annular air inlet mode, average temperature of rotary kiln is the lowest while O₂ concentration is the highest at the tail of the kiln, CO₂ concentration is the lowest and CO is not fully converted. In this condition, the gas turbulent intensity and hazardous waste velocity are both the minimal. Therefore, the material burnout rate and coke conversion rate are both the lowest.The parameters under the single channel swirl inlet mode are between the above two.

A test rig for identification of the direct stiffness coefficient of the labyrinth seal was designed and built. The influence of the excitation frequency and inlet pressure on the direct stiffness coefficient at different rotational speeds was studied. The experimental results were compared with the theoretical calculation of the Bulk Flow model in DyRoBeS. Results show that the direct stiffness coefficient of the labyrinth seal is negative under any operating conditions, which makes it prone to rotor instability. The direct stiffness coefficient decreases with increasing rotational speed, inlet pressure and excitation frequency. The rotational speed has little influence on the direct stiffness coefficient. And the direct stiffness coefficient is highly dependent on the high excitation frequency. The theoretical prediction calculation of DyRoBeS shows good agreement with the experimental measurements.

To achieve the cascade utilization of low-temperature waste heat from cement kilns and the carbon capture of flue gas, a novel flash-type waste heat power generation system integrated with carbon capture unit was proposed. The primary saturated flash steam of the waste heat power generation system was used as the heat source for the carbon capture unit. Then, the saturated water generated steam through the secondary flash, and the generated steam was sent to the steam turbine as supplementary steam to generate power. The Aspen Plus and Ebsilon software were used to simulate the carbon capture unit and the waste heat power generation system, respectively. The thermal integration of the system was optimized, and the technology of the carbon capture unit was further improved to reduce carbon capture energy consumption. Meanwhile, from perspectives of energy and exergy, the thermal performance variation of the system after integrated with the carbon capture unit was deeply analyzed. On this basis, the influence of carbon capture energy consumption on the performance of the novel system was further analyzed. Results show that the proposed system has a generating capacity of 7.452 MW, and captures about 110 000 tons of CO₂ annually. The carbon capture energy consumption rate decreases from 3.58 GJ/t to 3.08 GJ/t, and the cycle efficiency and net power generation efficiency can be increased by 0.51 and 0.9 percentage points, respectively.

An efficient and flexible heating system coupled with low-grade waste heat and extraction steam was constructed to balance efficiency and flexibility. The performance indexes of heating and peak shaving were determined and the thermal model was established by Ebsilon. The thermal performance of the system under design and off-design conditions in the case area was studied. The adjustable range of electric load under different heating loads was obtained. The flexible operation and control strategy and the energy consumption characteristics of the system were analyzed in case of simultaneously meeting heat and electric demand.Results show that the system achieves low energy consumption heating by matching energy and quality, reducing specific equivalent electricity consumption. The specific coal consumption for heat supply is 13.3 kg/GJ under the design condition. The maximum peaking capacity ratio is 48.1%, which is 24.3% higher than the back-extracting mode. When the electric and heat load change, the operation mode switches among back-extracting-cutting modes, and the specific coal consumption for heat supply ranges from 8 to 14.7 kg/GJ. The specific coal consumption for heat supply increases with the decrease of electric load. The system develops the energy-saving advantage of supplying heat by waste heat and realizes heat and power decoupling in a certain range. Both "efficient" and "flexible" operation are taken into account.