Taking the 50 MW tower solar thermal power station as an object of simulation, a heliostat mirror field model and a cylindrical exposed receiver model were established according to the main simulation parameters of the station, based on which, the distribution of flux density on the surface of the receiver was calculated for the following three concentrating strategies of the heliostat, such as the simple, alternating offset and normal distribution concentrating strategy, using the data of typical meteorological years, by the method of ray tracing, under design point conditions, over the whole day of summer solstice, and in different layouts of heliostat field. Meanwhile, the influence of above three concentrating strategies on the safety of the receiver was analyzed. Results show that among the three concentrating strategies, the alternating offset concentrating way could effectively improve the distribution of flux density on the surface of the receiver, resulting in higher safety of the station.

From the perspective of large capacity steam turbine technology development,remarkable progresses from 2010 to 2019 and research prospect in China were reviewed.The background of large capacity steam turbine development was introduced,and new achievements on large capacity steam turbine technology research for thermal power and nuclear power in recent decade were summarized,including three technologies,such as the optimization of flow path and the performance at the wide range of load to improve efficiency; comprehensive design technology concerned with structural strength and lifetime,rotor dynamic and support,high temperature material and welding rotor to ensure safety; automatic turbine one-key start-up or shutdown control and thermal stress monitor to enhance the operation flexibility. Based on the development status,research prospect of domestic large capacity steam turbine was proposed in aspect 700℃ high temperature nickel alloy component,non-nickel alloy high temperature rotor,2 000~2 300 mm half-speed long blade for 2 000 MW nuclear power steam turbine,and intelligent technology of design,manufacture,operation and maintenance.Further target of large capacity steam turbine development is to promote the efficiency,guarantee reliability, safety and operation flexibility.

To study the effects of temperature and reactant concentrations on the formation mechanism of ammonium bisulfate (ABS), characteristic experiments were conducted on a self-developed test setup, during which the vaporating point of ABS was obtained through thermogravimetric analysis, and subsequently its decomposition temperture was acquired by calculating the Gibbs free energy for decomposition of ABS. Results show that the formation of ABS is a function of temperature and reactant concentrations, and its formation temperature lies in 220-261℃; the larger the concentration product of NH₃ and H₂SO₄, the higher the formation temperature of ABS; for a constant excessive concentration of H₂SO₄, the higher the concentration of NH₃, the larger the ABS precipitation amount; whereas for a constant concentration of NH₃, the effect of H₂SO₄ concentration on ABS precipitation is not obvious. Thermogravimetric analysis indicates that the volatization and decomposition temperature of ABS are respectively 173.7℃ and 447.18℃.

An analysis was conducted on the technical problems occurring in low load (below 40% rated load) and ultra-low load (20%-30% rated load) operation of current domestic pulverized coal-fired boilers, such as poor combustion stability, low hydrodynamic safety, high pollutant emission and low unit economy, etc., following which, corresponding countermeasures were discussed. Results show that the boiler could achieve steady combustion under ultra-low load condition after taking corresponding countermeasures such as refined combustion adjustment, etc. The hydrodynamic safety of a once-through boiler is relatively high in the process above 30% rated load; with the reduction of unit load, the hydrodynamic safety of a drum boiler increases, while its economic performance drops significantly. As to the pollutant emission, more attention should be paid on the NO_x concentration.

Collaborate on climate change mitigation has become a widely-accepted consensus for the international community. As an important participant and active player of the global response to climate change, China has put ‘carbon-peak and carbon-neutrality’ into the overall layout of ecological conservation. The initiative of ‘carbon-peak and carbon neutrality’ is an extensive and profound reform for the entire economy and society, in which the low-carbon oriented transition of energy will be the key to achieve the target. Under the current level of economic and social development, the overall development plan of ‘two-step acceleration’ should be adopted. In the near term, non-fossil energy should be accelerated to achieve the carbon-peak target by 2030. 2℃ temperature-rise target and 1.5℃ temperature-rise target should be implemented in the medium and long term to achieve carbon neutrality by 2060. In order to ensure the realization of the ‘carbon-peak and carbon-neutrality’ target, it is necessary to strengthen the research on key technologies or planning issues, including the power system with deep renewables penetration, low-carbon transition pathway of coal-fired power, and CCUS, etc.

Combining the thermodynamic calculation in sections for large capacity boilers with simplified dynamic model of full-furnace pressure and temperature, and based on the law of energy conversation and the theory of radiation heat transfer, mechanism models of furnace temperature were set up for three zones of a 600 MW boiler before and after dual-scale low nitrogen retrofit, with which combustion characteristics in vertical space of the furnace was simulated using Simulink software. In addition, the temperature field and velocity field in horizontal space of the furnace were also simulated using Fluent software, while the mechanism of dual-scale low nitrogen combustion retrofit was analyzed comprehensively. Results show that the flow of primary air is in opposite direction to the secondary air due to the bias of primary air flow after retrofit, thus making the swirl region expanded in horizontal direction and shortened in vertical direction, resulting in increased combustion efficiency and lowered NO_x emission in partial areas, but simultaneously increased inertia of combustion process and reduced adaptability to uploading conditions.

Numerical simulations were conducted on a domestic 1 000 MW ultra-supercritical double reheat boiler system based on a unit model newly built to study the performance of the boiler, and to calculate the exergy loss and exergy efficiency of the boiler system and its components at different loads according to exergy balance equations. Results show that with the variation of unit load, all the components maintain high exergy efficiency with small fluctuation, which could satisfy the requirements of deep peak regulation under low load conditions and ensure stable operation for the unit. The exergy loss caused by combustion and heat exchange accounts for 97% of the total, which could be lowered by reducing the heat exchange temperature difference between the working medium and the high temperature flue gas.

In order to analyze the mechanical properties of bend-twist coupling blades, the NREL 5 MW wind turbine blade shell model was established based on the secondary development of the three-dimensional modeling software NX. The composite material layup design was further carried out on the blades and aeroelastic tailoring of blades was achieved by offsetting the spar cap fiber in the mirror image. The CFD method was used to calculate the pressure distribution on the blade surface. To study the effect of the spar cap fiber offset angle on the mechanical properties of the bend-twist coupling blades, the modal, static and buckling analyses were performed in conjunction with the finite element method. Results show that when the offset angle of the spar cap is small, the maximum stress value on the surface of the bend-twist coupling blade is smaller than that of the traditional blade. The effect is best when the offset angle is -15ånd the maximum stress value decreases by 14.78%. Compared with the conventional blades, the natural frequencies and buckling factors of each order of the bend-twist coupling blades all decrease,and their decrease are close when the angle of forward and reverse offset are the same.The off-axis mirror laying of the spar cap has a great influence on the flapwise vibration of the blade. The offset angle of the spar cap has a certain influence on the anti-buckling ability of the blade and the maximum buckling load of the blade is reduced by about 78%. The natural frequency and buckling factor of the bend-twist coupling blades should be paid more attention to avoid the resonance between the natural frequency of the blade and the excitation frequency. If necessary, the laminate structure should be optimized to improve the anti-buckling ability of the bend-twist coupling blades.

The effect of hot isostatic pressing (HIP) on the microstructure and the mechanical properties of precision casting Mar M247 was investigated. Results show that the hot isostatic pressing helps to eliminate the microporosities, increase the density, improve the microstructure, and reduce the segregation of the alloy, leading to greatly improved impact property, tensile property and stress rupture property of the material. Meanwhile, the data dispersion of density and mechanical properties could be reduced for the alloy by hot isostatic pressing.

A conjugate heat transfer simulation was conducted on the film cooling flow field at the trailing edge of gas turbine blades, and the simulation results were compared with that of adiabatic method, thus finding the film cooling behavior at different blow ratios and suction surface thickness. Results show that compared with the adiabatic method, the curve of film cooling efficiency obtained by conjugate method is more gentle, with more uniform temperature distribution on the suction surface but a higher temperature gradient above the pressure surface. Increasing the blow ratio could reduce the effect of heat conduction on film cooling and inhibit the separation of the fluid from wall surface effectively. As the thickness of the suction surface increases, the fluid temperature in the area from 0.6 to 0.76 isotherm changes, the temperature rises in the downstream of cutback outlet and decreases in the place far from the cutback.

The design of an impeller with axial admission of air flows, i.e., the impeller with blade leading edge located at the impeller eye, was presented and discussed. First, the cubic Bezier curve was applied to design the meridional flow channel. Then, the distribution of the angular momentum on surfaces of the shroud and hub was prescribed by using a piecewise polynomial function. Finally, modified formulas for the optimum ratio of D₁/D₂ (D₀=D₁) were proposed via numerical simulations for the impeller with blade leading edge at the impeller eye, and simultaneously the blade angle was analyzed. Results show that the blade angel on the shroud surface shows a monotonic increasing tendency for the impeller with axial admission of air flows, different from that with radial admission of air flows. By calculation with above modified formulas to optimize the ratio of D₁/D₂, the whole-pressure polytropic efficiency can be improved by 5% within the scope of working conditions.

Photovoltaic-coupled hydrogen production technology can use the waste and abandoned electricity generated by photovoltaics to produce hydrogen on a large scale, which reduces the hydrogen production cost, improves the overall system efficiency, and plays an important role in the transformation and upgrading of photovoltaic systems. By analyzing the development status of domestic photovoltaic coupled hydrogen production technology, its operation performance and system economy were evaluated. Finally, according to the characteristics of Northwest China, a technical route suitable for photovoltaic coupled hydrogen production technology demonstration was proposed.

An experimental system was set up to study the gas-liquid two-phase flow in a vertical rectangular narrow channel, based on which, the gas-liquid two-phase flow was visualized by a high-speed camera, and subsequently the automatic images were recognized, while close bubbles were discriminated using Matlab software. Results show that the relationship between average void fraction α and volume void fraction β is found to be α=0.88β. The calculated results have a high matching degree with the experimental measurements after the coefficient C of Chen model is revised.

To study the stall mechanism of a transonic axial compressor, numerical simulations were conducted on the NASA Rotor 35 combined with throttle valve model. To further research the variation behavior of the flow field during stall process, an analysis was carried out on the flow field in the tip region using the method of proper orthogonal decomposition (POD). Results show that the stall originates in the tip region of blade and develops into a stall cell rotating coaxially with the rotor in the same direction but with lower speed. By comparing the flow field characteristics at different time, the leakage flow is found to exist throughout the process of stall development, which could be taken as a basis for judgment of flow field worsening. Meanwhile, the structure of large-scale unsteady flow could be identified in the flow field during stall process.

Life cycle assessment systems of wind, PV and coal-fired power generation were established based on life cycle assessment theory, so as to compare and analyze their environmental load produced at different stages. Results show that in the construction state of a power plant, the carbon footprint of coal-fired power generation is 1.94 g/(kW·h), which is the lowest in the three power generation ways, and the carbon footprint of wind power generation is 9.42 g/(kW·h), which is the highest. Whereas in the operation stage of a power plant, the carbon footprint of PV power generation is almost zero, and that of wind and coal-fired power generation is respectively 0.2 g/(kW·h) and 83.3 g/(kW·h), indicating that coal-fired power generation produces the highest carbon footprint. The ratios of carbon footprint in construction stage for wind and PV power generation are relatively high, which are 99.4% and 99.78%, respectively; while the ratio of carbon footprint in operation stage for coal-fired power generation has the highest value of 96.13%. Results also indicate that coal-fired power generation has the greatest influence on global warming in a whole life cycle with a standard equivalent of 3.63×10^-5, while wind power generation has the least influence with a standard equivalent of 7.9×10^-7; whereas PV power generation has the biggest impact on environmental acidification with a standard equivalent of 6.7×10^-6, and wind power generation has the smallest impact with a standard equivalent of 1.6×10^-7. The emission of solid waste is almost zero in both wind and PV power generation.

Taking the 600 MW supercritical steam turbine as an object of study, a theoretical analysis was conducted on the energy saving potential of the composite regulation mode, while experimental tests were performed to determine the flow characteristics, analyze the energy consumption characteristics and to set the overlap degree of various high-pressure control valves under different sequences of operation, following which, the sequence of valve opening was optimized. Results show that after optimization, the high-pressure cylinder efficiency could be increased by 1.53%, 1.34% and 1.42%, and the corresponding heat consumption rate could be reduced by 26.0 kJ/(kW·h), 23.2 kJ/(kW·h), and 25.3 kJ/(kW·h), respectively at the medium/low loads of 500 MW, 400 MW and 330 MW.

Based on the gas combustion test platform, a large number of diffusion and premixed flame images were taken by industrial CCD camera under different conditions, following which, six characteristic variables that representing the shape, position and brightness of the gas flames were obtained by choosing and adopting appropriate image processing algorithm. Taking the six characteristic data of different kinds of flames as the training samples, the classification program was trained by support vector machine, and subsequently the real-time monitoring and stability evaluation were conducted on the combustion test platform. Results show that via the method proposed, the detection accuracy may achieve 99% for different types of flames.

To solve the problem of unstable vibration occurring in the HP-IP rotor of a 660 MW supercritical steam turbine, a dynamic response model was set up for the system under coupled action of shaft bend and rotor unbalance using finite element method, of which the accuracy was verified with field experiments. Results show that the shaft bend caused by inconsistency between balancing and unbalance plane can not be neglected at high rotating speeds, since it may lead to the instability and increase of vibration. The balancing plane should be chosen on the unbalance plane as far as possible. High-pressure rotor is easy to have creep deformation under the effect of external force due to its high-temperature operation environment; the phenomenon is even more obvious for high-pressure rotors of large steam turbine.

Wind tunnel experiments were conducted to study the effects of sand accumulation on the output characteristics of solar photovoltaic (PV) modules at different sand concentrations and wind speeds, so as to plot the output characteristic curves at different dip angles, and to compare the power generation efficiency with and without sand accumulation. Results show that at low wind speeds, the power output of all the components at different angles changes slightly between the case with and without sand accumulation, showing a reduction degree below 5%; whereas at high wind speeds, the power output changes significantly between the case with and without sand accumulation, showing a reduction degree in 5%-10%. At installation angles of 30° and 60°, the power output of solar PV modules in pure sand environment presents obvious turning features.

To reduce the effects of local resistance in pipe tees on hydraulic balancing and energy consumption of the heating supply network, the velocity and pressure field in pipe tees with diameter equal to or above 400 mm were simulated using Fluent software, so as to analyze the influence of following factors on the local resistance characteristics, such as the split ratio (q), Reynolds number (Re), diameter ratio (d) and the angle between main pipe and side branch (θ), etc. Results show that both the local resistance coefficient of main pipe to side branch ζ₀₁ and that of main pipe to straight branch ζ₀₂ reduce with rising Re, which basically get stabilized at Re=4.8×10⁵. ζ₀₁ and ζ₀₂ increase with the rise of q in the case of d less than 0.8, which have a parabolic relationship with q in the case of d larger than or equal to 0.8. For a certain value of q, ζ₀₁ reduces with rising d, and the reducing tendency slows down obviously in the case of d larger than 0.7. Analysis results indicate that with the rise of θ, the size of vortex, the gradient of velocity and the curving degree of streamline increase significantly in the side branch, resulting in obvious increase of ζ₀₁, whereas the gradient of velocity slightly rises in the straight branch, resulting in slight increase of ζ₀₂ accordingly.

A proposal was suggested for maintenance interval optimization of steam turbines based on the design life, while an introduction was presented to the statistical results of utilization hours for domestic thermal power units, the calculation methods for common equivalent operating hours, the maintenance interval of steam turbines obtained based on the first equivalent operating hours, the calculation methods for start weight coefficients and load change weight coefficients of steam turbines based on the design of fatigue and creep life, the calculation methods for the second equivalent operating hours, the optimization methods for the maintenance interval, the calculation methods for annual average life expenditure of steam turbines and the calculation methods for annual average grade maintenance cost of a unit, together with application examples of a 1 000 MW ultra-supercritical steam turbine and a 600 MW supercritical steam turbine. Results show that compared with the two standards in China Power Industry, the number of years for class A maintenance interval of steam turbines optimized based on the design life is larger, with less average annual life expenditure of the steam turbine and lower average annual grade maintenance cost of the unit. This may serve as a reference for safety and economic operation of power plant steam turbines.

Based on power generation simulation of a yaw system and fatigue life quantitative analysis of the yaw bearing, a yaw control reboot tracing wind strategy model was established, which takes comprehensive economic benefits of the wind turbine in a life cycle as the target, the start and stop control of the yaw system as the strategy, thus to reasonably balance the relationship between the power generation and the yaw frequency. To find the optimal control strategy, the hybrid particle swarm optimization-genetic algorithm (PSO-GA) was adopted to optimize the control model. Results show that the model proposed can achieve the expected optimization goals, which may serve as a reference for improving the comprehensive economic benefits of wind turbines.

To study the co-firing characteristics of coal and biomass gas for coal-fired boilers, a co-combustion model was built for a 300 MW subcritical boiler to simulate the combustion process of pure pulverized coal and mixed fuel using Fluent software, and to find out the variation law of in-furnace velocity field, temperature field, gas component and NO_x distribution at different arrangements of biomass gas nozzles, during which, the quantity of biomass gas was calculated according to 20% of total heat input of the boiler under co-firing conditions. Results show that, compared with the condition of pure pulverized coal combustion, all the parameters, such as the maximum in-furnace temperature, the outlet gas temperature and the outlet NO concentration, are lower than that under co-firing conditions. The position of biomass gas nozzles has a great influence on the temperature distribution and NO emission when the overall structure of the furnace is not changed.

Taking the profile of the first-stage stator blade in a heavy duty gas turbine as an object of study, the effect of surface roughness on heat transfer characteristics of the blade airfoil was researched using the equivalent sand-grain roughness model of commercial software CFX. Results show that the variation of roughness affects little on the time-mean flow field near the airfoil, but under a typical surface roughness of turbine blade, the heat transfer coefficient would be increased by 36.6% and 33.4% respectively on the pressure side and suction side, compared with a smooth surface, indicating enhanced heat transfer effectiveness. Small-scale surface roughness has little effect on the heat transfer of a leading edge, but when the roughness h_s gets up to 51 μm, the average heat transfer coefficient would drop by 15%, compared with a smooth surface. According to the one-dimensional model of heat conduction, when the heat transfer coefficient is increased by 30%, the average temperature of the blade metal would be increased by 17 K, resulting in significantly reduced life of the blade.

Taking the 1 000 MW double reheat ultra-supercritical unit as an example, based on analysis of the specific fuel consumption, the effects of following arrangement modes of outer steam coolers on the energy consumption of unit were studied, such as the single series connection, double series connection and double parallel connection, etc., and subsequently the optimum arrangement mode of outer steam coolers was obtained, in which case the variation law of specific fuel consumption was analyzed for each part of the thermal system and for the whole unit. Results show that by adopting the outer steam coolers, the feedwater temperature is raised, the irreversible loss of boiler is reduced, thus lowering the specific energy consumption of unit. In the single connection mode, the specific fuel consumption can be reduced by 0.632 g/(kW·h) at most when the outer steam cooler is arranged at No.2 high-pressure heater; whereas in the double connection mode, the specific fuel consumption can be reduced by 1.122 g/(kW·h) at most when the coolers are arranged in series at No.2 and No.4 high-pressure heater. With the reduction of unit load, the energy-saving effect will have slight decrease if double outer steam coolers are arranged in series connection.

To investigate the immobilization behavior of heavy metals As, Pb, Se and V in a waste SCR catalyst during the process of high-temperature melting treatment, a series of melting experiments were conducted with the addition of composite additive CaO-Fe₂O₃-SiO₂-Al₂O₃ and coke in a high-temperature tubular furnace, so as to analyze the effects of melting temperature and time on the leaching toxicity and volatilization property of the heavy metals using X-ray diffraction (XRD), scanning electron microscope (SEM) and heavy metal leaching tests. Results show that the heavy metals in waste SCR catalysts could be effectively stabilized by high-temperature melting treatment technology. The melting temperature significantly affects the leaching toxicity and volatilization property of heavy metals in a waste SCR catalyst; the leaching concentration of As, Pb, Se and V decreases remarkably with increasing melting temperature. The volatilization rate follows the order of Pb>Se>As>V, in which the volatilization rate of Pb and Se increases first and then decreases with rising temperature, and that of As and V is close to zero. With the rise of melting time, the leaching concentration of As, Se and V increases first and then decreases, while that of Pb decreases monotonously. The melting time exerts little influence on the volatilization of heavy metals in a waste SCR catalyst.

Thermodynamic design and aerodynamic design were conducted on a radial-inflow turbine using iteration method and screening method, respectively, while an analysis was carried out on off-design performance of the turbine using three-dimensional numerical simulation. Results show that under different inlet mass flow rates, the total to total efficiency varies in different laws with the relative rotational speed. At larger inlet mass flow rates, the maximum efficiency corresponds to the lowest relative rotational speed. At the design inlet flow rate, the radial-inflow turbine could work stably at higher efficiency in a certain range of relative rotational speed. When the inlet flow rate is constant, the power output rises first and then drops with the increase of relative rotational speed; whereas, when the rotational speed is constant, the power output increases with the enhancement of inlet mass flow rate; the variance amplitude of power output reduces with rising relative rotational speed.

To solve the problems of high CO emission concentration at furnace outlet and coking at flue gas exhaust outlet existing in a 670 MW octagonal corner tangentially-fired tower boiler burning low calorific value lignite, numerical simulations and experimental tests were conducted to study the effects of the following factors on the in-furnace temperature field, and the O₂, NO_x and CO concentration distribution, such as the vertical swing angle of SOFA, the SOFA volume and the SOFA speed, etc. Results show that the increase of SOFA air velocity can effectively reduce the flue gas temperature and CO concentration at furnace outlet. Compared with case 1, the outlet CO concentration of the furnace in case 6 has been reduced from 0.291 2% to 0.025 7%, with a reduction of flue gas temperature at furnace outlet by 43 K, a reduction of exhaust gas temperature by 6 K, an increase of boiler efficiency by 0.63%, and a reduction of standard coal consumption by 2 g/(kW·h), while the NO_x emission concentration basically keeps unchanged at furnace outlet.

Taking a 670 MW supercritical tower boiler under BMCR condition as the benchmark model, numerical simulations were implemented on staged combustion of the eight-corner single-tangential firing boiler, so as to study the generation, distribution and emission characteristics of NO_x at different SOFA ratios, and to compare the simulation data with actual measurements. Results show that when the SOFA ratio is raised from 0.040 to 0.207, the peak temperature in furnace would be reduced by 80 K, and the outlet NO_x concentration would be reduced from 535 mg/m³ to 373 mg/m³, indicating obvious effects of SOFA ratio on the NO_x emission. By comprehensively considering the oxygen and temperature factors, it is recommended to keep the SOFA ratio no more than 0.2 in actual operation.

To solve the problem of poor accuracy and long period of design and optimization for a supercritical carbon dioxide (S-CO₂) turbine using traditional design method, a fast thermodynamic design method was established for the radial inflow turbine based on one-dimensional flow theory. A design-optimization method was also proposed based on Gauss process regression, which combines the high precision three-dimensional aerodynamic analysis with the thermodynamic design to evaluate the real efficiency of the turbine aerodynamic design, verify the accuracy of the design results in simulated annealing process, and to demonstrate the effectiveness of the design and optimization for the S-CO₂ turbine with calculation examples. Results show that via the method proposed, the isentropic efficiency of the turbine could be increased from the original 83.68% to the optimal 91.20%; an optimal design result would require 120 cycles of aerodynamic analysis by traditional method based on simulated annealing optimization, however, by the method proposed, only 24 cycles are requred, which greatly shortens the time of design and optimization, and therefore may serve as a reference in engineering applications.

A theoretical analysis was conducted on the formula to calculate the leakage rate of labyrinth seals considering actual gas parameters and on the equation for the flow control. Based on the rotor multi-frequency elliptic vortex method, the effects of medium category and real gas parameters on the static and dynamic characteristics of labyrinth seals were studied. Results show that the molar mass of gas is positively correlated with the leakage rate of labyrinth seals. At the same frequency of rotor vortex oscillation, the absolute values of direct stiffness coefficient and of main and cross damping coefficient increase with the rise of the molar mass of gas. The flow force increases as the molar mass of gas rises, and the flow force of medium CO₂ is 1.63 times as much as CH₄. As the frequency of vortex oscillation increases, the influence of molar mass on the damping coefficient gradually transfers from the inertial effect to the frictional effect, therefore, as the molar mass of gas increases, the effective damping coefficient increases at low frequency and decreases at high frequency.

A multi-objective analysis and optimization model was established for the plate-fin heat exchanger in a micro gas turbine, based on the coupling relationship between the structural parameters of the heat exchanger and the performance of the gas turbine. On that basis, the effects of key exchanger parameters on the performance of both the heat exchanger itself and the gas turbine were analyzed under two operating conditions (constant heat absorption in the combustion chamber and constant power output of the gas turbine). Results show that the main factor influencing the power output and heat absorption is the pressure loss but not the effectiveness of the heat exchanger. The variation trend of all parameters in above two operating modes keeps consistent (except for the heat absorption and power output). After optimization of the fin structure, the turbine power output is increased by 6.8%, and the heat absorption of combustion chamber is decreased by 5.1%. Compared with the original parameters, the optimized fin thickness, fin spacing and corrugation angle decrease, while the fin height increases, thus ensuring a small pressure loss of the heat exchanger. At the same time, it is found that there is no significant difference in the results when minimum entransy dissipation and minimum entropy production are taken as the optimization objectives.

To reasonably evaluate the operation performance of a coal-fired power plant adopting the ammonia-based carbon capture process, a technical economic model was set up based on the simulation model of carbon capture system and the variable condition model of power plant, so as to analyze the effects of following parameters on operation performance of the unit, such as the ammonia concentration, lean solvent loading, chilled temperature, desorber pressure, ammonia slip rate and carbon capture rate, etc., and subsequently to determine the optimal variables of the carbon capture system. Results show that the optimal values of ammonia concentration, lean solvent loading and chilled temperature are respectively 11%, 0.36 and 15℃, when the power generation efficiency would be increased by 0.7127%, and the coal consumption rate, power generation cost and carbon capture cost would be reduced by 6.9594 g/(kW·h), 0.011 CNY/(kW·h) and 16.7563 CNY/t accordingly, compared to the original power unit.

Parametric programming was adopted on the modeling of deformable trailing edge flap (DTEF) to realize its flexible deformation and control, based on which numerical simulations were conducted to analyze the effects of DTEF on aerodynamic performance of the wind turbine airfoil and to study its flow mechanism respectively under static and dynamic conditions. Results show that under static conditions, the angle of flap affects the lift coefficient and drag coefficient obviously; with the rise of attack angle, the ability of DTEF reduces in changing the aerodynamic performance of the airfoil, and its influence on neighboring flow field weakens accordingly. Swing DTEF makes the change of lift coefficient of airfoil lags the change of flap angle, with reduced ability of DTEF on the control of lift coefficient; whereas swing DTEF makes the change of drag coefficient leads the change of flap angle, with enhanced ability of DTEF on the control of drag coefficient; these unsteady effects of flap oscillation are enhanced with the decrease of the oscillation cycle, reflecting in the variation of surface pressure coefficient of airfoil and in the development of wake vortex.

Based on random theory and statistical properties of transmission light, a light fluctuation method was proposed to measure the size distribution of pulverized coal in power plant, which was verified with a self-developed experimental setup. Results show that via the method, the parameters of size distribution could be effectively obtained. By combining with wavelet reconstruction technology, the method can be used to process actual data of a power plant, during which the influence caused by concentration fluctuation and oversample could be avoided, thus obtaining accurate information of size distribution and concentration of the pulverized coal.

According to the characteristics of large inertia, large time delay and nonlinearity of the controlled object as boiler superheated steam temperature in thermal power plant, the sliding mode variable structure control (sliding mode control) was applied to the cascade superheated steam temperature system. To reduce the steady-state error caused by external disturbances, and to weaken the chattering problem of sliding mode, a new sliding mode control algorithm was designed by introducing the integrating element, and using the modified super-twisting algorithm to replace the switching control. On Simulink platform, simulations were conducted for the high order model of superheated steam temperature system, such as the step response simulation, model parameter mismatch simulation and robustness simulation, etc. Results show that compared with conventional cascade PID control, the algorithm proposed has better dynamic performance, such as shorter regulation time, smaller overshoot and stronger robustness, etc.

Taking deionized water as the working medium, experimental studies were conducted on flow boiling heater transfer in a 3×3 rod bundle at an inlet temperature of 80-100 ℃, a mass flow rate of 0-100 kg/(m²·s), and an inlet pressure of 0.1 MPa, so as to analyze the effects of mass flow rate and heat flux on the flow boiling heat-transfer coefficient, and to investigate the heat-transfer characteristics in various sub-channels. Four correlations were adopted to predict the flow boiling heat-transfer coefficient, including Liu-Winterton, Kandlikar, Gungor-Winterton and Chen, etc., and subsequently their prediction results were compared with experimental data, which were simultaneously evaluated using three statistic indicators. Results show that the predicted values of Liu-Winterton, Kandlikar, and Chen correlation are relatively lower than the experimental data, in which the error of Chen correlation is the highest, while Gungor-Winterton correlation is the most accurate one among all the four correlations.

To improve the aerodynamic and acoustic performance of an axial flow fan, a comparative study was conducted on the aerodynamic performance and internal dynamics of an OB-84 single-stage variable-pitch axial flow fan with rear guide vanes before and after blade skewing, using Fluent software and Ansys finite element analysis, while the static structure features were investigated and the noise was predicted. Simulated results show that the total pressure rise is improved by the skewed blades and the promotion is apparent on the side of large flow rate; the best forward-skewed angle is 3.0° at the design point, in which case, the total pressure rise and the efficiency would be increased by 3% and 0.16%, respectively. The skewed blade improves the axial velocity, delays the emergence of separation flow in the region of blade root, raises the working ability in the middle and lower part of blades, and lessens the pressure difference between the suction surface and pressure surface in the tip region, leading to the effective reduction of tip leakage flow. The skewed blade has little influence on reducing the sound power level, but has a significant impact on the reduction of high-noise area, and thereby the fan noise is weakened.

Using a traditional particle collector and a Dekati DPI small particle collector, flue gas particles were sampled from the inlet and outlet of two differently-structured wet electrostatic precipitators (WESPs) in two 300 MW coal-fired units with near-zero emissions, to which the overal and grade removal efficiency were measured, while the particle size distribution was analyzed. Results show that both the wire-plate and wire-pipe WESP have an outstanding paricle removal efficiency, and the near-zero emission standard of flue gas particles can be achieved using either the wire-plate or wire-pipe WESP, i.e. the particle emission could be controlled under 5 mg/m³. Compared with the wire-pipe WESP, the wire-plate one has a higher particle removal efficiency in the range of particle sizes larger than 10 μm and smaller than 1 μm.

To overcome the difficulty in fault diagnosis of wind turbines due to their complex operation conditions and data information structure, an improved multiblock kernel principal component analysis (MBKPCA) method was proposed based on factor analysis, so as to establish an association mechanism among the unit data, variables and operating conditions by deeply mining the operation data. Through corresponding analysis, the relationship between unit variables and the data was defined, while the number of MBKPCA sub-blocks and their actual meanings were determined. Finally, the factor analysis was adopted to find out the correlation between the data of various sub-blocks and the process of corresponding motions, thus improving the diagnostic accuracy of MBKPCA. Results show that the improved MBKPCA method can help to make fault diagnosis timely and accurately for wind turbines, which may be applied in actual engineering projects.