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℃.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 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 mathematical model was established for the supercritical fossil-fired power system with CO₂ recompression and reheat Brayton cycles, based on which the effects of following key parameters on the cycle efficiency were analyzed through detailed calculation with programs developed on the Fortran platform, such as the split ratio of flow, the inlet and outlet pressure of compressor, inlet temperature of turbine etc. Results show that the cycle efficiency increases linearly with the temperature rise of primary and secondary working medium. Different from traditional Rankine cycles, above parameters in Brayton cycles show non-monotonic relationship with the cycle efficiency due to the features of spercritical CO₂ physical properties and the constraints of minimum temperature difference for heat exchange. There exists an optimum combination of compressor inlet pressure, compressor outlet pressure and split ratio for supercritical CO₂ Brayton cycles, in which case, the cycle efficiency reaches the maximum.

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.

In the collection process of farmer straw for power generation, there are in total following four supply modes:manpower collection + active delivery, machinery collection + active delivery, manpower collection + waiting for delivery, and machinery collection + waiting for delivery. Corresponding models were established for cost calculation of farmer straw in above supply modes, while single factor analysis was conducted for different key sensitive factors. Results show that the mode of manpower collection has lower cost than machinery collection, which however is greatly affected by the labor price, and when the labor price is more than 18 CNY/h, the mode of manpower collection + active delivery costs the maximum. When the arable area is larger than 0.667 hm², the cost of all supply modes would basically keep constant. The mode of manpower collection is more affected by conveying distance than machinery collection, the shorter the stubble is, the higher the influence will be. Machinery collection is found to be the most suitable mode for the condition of high crop yields.

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.

Numerical simulation was conducted on the attenuation mechanism of audio waves in the furnace of power plant boiler, based on which a formula of sound attenuation coefficient in the gas medium containing solid particles was built, so as to analyze the effects of following factors on the attenuation coefficient, such as the acoustic frequency, particle concentration, particle size and flue gas temperature, etc. Moreover, attenuation characteristics of acoustic waves in the furnace of fluidized bed boiler containing solid particles of higher volumetric fractions were also studied based on multi-body multiple scattering theory, and subsequently corresponding attenuation coefficients were corrected. Results show that for general coal-fired boilers, the sound attenuation coefficient increases with rising flue gas temperature, particle concentration and sound frequency, and with reducing particle size; whereas for fluidized bed boilers, the acoustic attenuation mainly originates from the thermal diffusion on the surface of medium particles.

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.

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.

A numerical simulation was conducted on the gas-solid two-phase flow in a single shutter coal separator of a 600 MW supercritical W-flame boiler, including a hot-state simulation on the in-furnace combustion, so as to obtain the simulation results on corresponding separating effect and ignition distance of the boiler at different secondary air ratios under the arch, and to compare them with experimental data. Based on above simulation results, different retrofit schemes were proposed and compared by replacing all the shutter separators with high-efficient cyclone ones, considering the combustion conditions in reasonable arrangements of over-arch secondary air nozzles and at reasonable under-arch secondary air ratios. Results show that lowest combustible matter in fly ash and balanced temperature distribution between V-type bottom of the furnace and the bottom of platen superheater would be obtained when the under-arch secondary air ratio is set to be 36%. In retrofit scheme 1, the water wall at lower part of the furnace is protected from heat-transfer deterioration by a low-temperature layer formed on the surface. The simulated boiler performance after retrofit is proved to agree well with actual test data.

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.

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.

A novel water gas shift (WGS) process was proposed, where the heat released in WGS reaction can be utilized to heat the syngas before entering into the gas turbine, while a process model was set up for the whole integrated gasification combined cycle (IGCC) unit using Aspen Plus software, based on which the effects of pre-combustion CO₂ capture on the power output, auxiliary power consumption rate and plant net efficiency of the unit were evaluated, and simultaneously the variation of two key parameters of the novel WGS process and their influences on the unit performance were analyzed. Results show that it is beneficial to decrease the auxiliary power consumption rate and increase the plant net efficiency by reducing the mole ratio of H₂O/CO in syngas that entering into WGS reactor and by increasing the final heating temperature of syngas. These findings agree well with those of previous studies. By adopting the optimized operating parameters for the WGS process, the auxiliary power consumption rate and the plant net efficiency are respectively decreased by 1.3% and increased by 2.7%.

Taking the EUROTROUGH-150(ET-150) parabolic trough solar collector as an example, mathematical models on heat collection and heat loss of the system were built to optimize its thermal efficiency. On above basis, a coal-fired power system aided by parabolic trough solar collectors (complementary power generation system) was researched to analyze the selection of direct normal irradiance (DNI) design values using a certain evaluation criteria in the integration mode. Results show that for collector fields with different number of loops and different latitude distributions, there exists optimal column spacing and optimal range of DNI design values to make the system annual performance optimum.

Aiming at the phenomenon of large gas temperature deviation between the left and right side at furnace outlet of a 660 MW supercritical tangentially-fired boiler, numerical simulation was conducted, and subsequently the results were compared with that of experiment. Results show that the simulation data agree well with experimental values, and the gas temperature deviation is found to be caused by residual rotating air flow, which can be reduced by counterclockwise adjusting the SOFA horizontal swing angle, reducing the opening of secondary air damper and increasing the opening of SOFA damper, etc. After taking above measures, the economy and safety of the boiler are improved.

A concept of cell models was proposed for thermodynamic calculation of double reheaters, while the cell dividing principles and schemes were described, including the calculation procedure and equations, etc. With the models, thermodynamic calculation and analysis were conducted on the double reheaters. Based on the dividing principles, high-temperature superheaters were divided into four cells (Ⅰ, Ⅱ, Ⅲ and Ⅳ) according the direction of flue gas and steam flow, while the primary and secondary high-temperature reheater were uniformly divided into three cells (Ⅰ, Ⅱ and Ⅲ) according to the arrangement relationship between superheaters and reheaters. Calculations were then conducted on each of the cells under different working conditions in the sequence of flue gas and steam flow. Results show that the calculated main steam temperature is around 610℃ and the outlet steam temperatures of reheaters are both above 600℃, with an error within 0.6% under BMCR condition, compared with the design value, which could be controlled by adjusting the flow rate of desuperheating water under all the conditions. This model is proved to be applicable for thermodynamic calculation of double reheaters, simply and easily.

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.

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 platform for steam gasification of biomass was built based on downdraft gasifier, which makes use of pine sawdust briquette to produce hydrogen-rich gas, so as to analyze the gas composition, hydrogen yield, gas yield, gas calorific value and coal gas efficiency at different temperatures. Results show that the high-temperature steam can effectively promote the forward reaction of steam reforming. When the gasification temperature rises from 700℃ to 900℃, the H₂ volume fraction, the hydrogen yield, the gas yield and the cold gas efficiency would be increased by 50%, 2.5 times, 70% and 37%, respectively. The steam reforming reaction can be accelerated towards the generation of H₂ by high specific enthalpy contained in the high temperature steam involved in the reaction. The rise of gasification temperature helps to boost the forward reaction for more output of gas product. The gas produced in high-temperature steam gasification of forestry wastes, like pine sawdust, etc., is of high grade, which is able to burn stably in the experiment and therefore is theoretically considered to be available in commercial process.

Flue duct evaporation products of desulfurization waste water were analyzed by XRD, EDS and ion chromatography, while their composition and morphology were compared with that of fly ash. Results show that the evaporation products of desulfurization waste water are mainly in solid and gaseous state. The solid products include CaSO₄, NaCl and Na₂SO₄, while the gaseous products are HCl, HF, HBr, HNO₂ and HNO₃. The evaporation does not have negative effect on comprehensive utilization of the fly ash, but would increase its specific resistance. In addition, gaseous products such as HCl can aggravate the corrosion of flue duct and increase the amount of desulfurization waste water discharged.

To research the dynamic response and mooring performance of a semi-submersible platform for floating wind turbine, a NREL 5 MW wind turbine model was established based on the semi-submersible platform, with which, numerical simulation was conducted on dynamic response and mooring performance of the platform under extreme sea conditions using Aqwa software by finite element method considering the combined action of random wave, wind and current load with the radiation/diffraction theory, thus obtaining the response amplitude operator (R_AO), the additional mass and the rate of radiation damping changing with the wave frequency, as well as the dynamic response of the platform and the tension response of the mooring line under extreme sea conditions. Results show that the platform would have good motion performance with little dynamic response, as the wave frequency is high (above 1.6 rad/s); changes of wave directions have little effect on the heave response; severest responses of surge and pitch would happen in the wave direction of 0 degree; under typhoon sea states, both the peak of dynamic response of platform and the peak of tension response amplitude are above those without typhoon; the dynamic response of platform and the tension response of mooring line increase with worsening sea states.

Numerical simulation was conducted on the fuel-air premixing and combustion process in a premixed swirl-stabilized combustor using Fluent software, so as to analyze the effects of vane parameters in the axial swirler on the premixing uniformity, flashback characteristics, total pressure loss and pollutants emission, etc., and to determine the improvement plans for the fuel injection structure. Results show that good combustion performance could be obtained when the cover degree of axial swirler is within 1.0-1.5, the angle of vane is within 40°-55° and the number of vanes is of 8-12. The premixing uniformity could be improved and the maximum combustion temperature could be lowered by following 3 measures, such as reducing the diameter of fuel injection holes, integrating the swirler with fuel injection holes and arranging the injection holes in a reasonable distribution, etc., in which case, the NO_x emission would be decreased by 91%, 35% and 91% accordingly.

To overcome the abnormal vibration faults frequently occurring in boiler water walls that may affect the safety operation of the boiler, vibration characteristics of a 60 MW boiler furnace were experimentally studied and numerically simulated with Ansys software, after which vibration suppression measures were proposed and implemented, such as adding pulling bars to enhance the stiffness of rigid beams, and hanging the soot blowers to reduce the concentrated mass, etc. In addition, inherent frequencies of boiler water walls before and after retrofit, and also the vibration displacement of each measuring point under circumstance of forced vibrations, were obtained via numerical simulation. Results show that the vibration displacement can be reduced by a maximum of 84.3% and 79.2% respectively in simulated scheme and actual measurement.

An optimization was conducted to the design of a plate stiffener located in the lower area of steam turbine exhaust hood using Latin hypercube experiment design, cubic response surface model and Hooke-Jeeves direct search technique. Based on numerical investigation of a large number of samples, the influence of different geometric parameters of the stiffener was studied on the aerodynamic performance of the exhaust hood, which was examined under variable conditions after optimization. Results show that both the distance between the stiffener and the meridian plane X as well as the dip angle of the stiffener θ have large influence on the aerodynamic performance of the exhaust hood, while the distance between the stiffener bottom and the hood outlet Y as well as the length of the stiffener L have little influence. The static pressure recovery coefficient can be improved effectively by arranging the stiffener appropriately, when the outlet non-uniformity would be reduced; however, this may lead to a certain loss of the total pressure.

To solve the problem of a power unit that can't response the requirement of AGC control after low NO_x combustion retrofit on the boiler, a study was conducted on the combustion characteristics of the boiler, the regulating quality of the coordinated control system and the response ability of the AGC control, including an analysis on the effects of following factors on the NO_x formation, such as the oxygen concentration in the furnace, the openings of SOFA damper, surrounding air damper and secondary air damper etc., while the influence of primary air combustion control on the unit response was investigated. On above basis, an optimized design and commissioning were carried out for the boiler-turbine coordinated control system. Results show that not only stable operation, but also high accuracy and quick response of the AGC control are achieved via the optimized coordinated control strategy, which has been successfully applied in low NO_x combustion retrofit of several units, proving the control strategy to be extendable and replicable.

Based on Euler-Euler method, the kinetic model for single-step multi-component reaction was used to study the fast pyrolysis of biomass in a two-dimensional bubbling fluidized bed reactor, with focus on analysis of the particle flow, heat transfer, and the distribution of pyrolysis products in the reactor. Results show that the bubble flow benefits the mixing and heat exchange of gas, quartz sand and biomass particles. Through convective heat transfer with gas and contact heat conduction with quartz sand, the temperature of biomass rises rapidly, following which, fast pyrolysis of biomass occurs, with a pyrolysis temperature lying in 750-850 K, and the calculated yields of bio-oil, char, and non-condensable gas being 59.2%, 14.4% and 22.1%, respectively.

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.