Against the actual problems that the wet cooling tower is easy to hang ice at the bottom of the packing and the upper edge of the inlet in winter, a three-dimensional numerical model of the cooling tower based on the constant heat load is established. The anti-freezing characteristics of the cooling tower in severe cold weather without anti-freezing device are explored, and the variation characteristics and influencing factors of key parameters such as the water temperature distribution of packing bottom and the air mass flow at tower top outlet are analyzed. The results show that, the lower the ambient temperature, the greater the influence of the unit load on the average water temperature and the lowest water temperature at the bottom of the packing. The main factors affecting the change of the difference between the average water temperature and the lowest water temperature at the packing bottom include unit load, wind velocities and water distribution mode. Among them, the influence of water distribution mode is greater, followed by unit load, and the influence of wind velocities is less. The air mass flow at tower top outlet is positively correlated with the unit load and negatively correlated with the ambient temperature. When the ambient temperature is the same, the air mass flow at tower top outlet of the outer ring with underwater is less than that of the full tower. The water temperature inside the lower part of the windward side and the outside of the leeward side is the lowest, and the freezing risk is the greatest. When the wet cooling tower is running in winter, the anti-freezing device should be arranged on the windward side and the leeward side.

Constructing a power system predominantly based on renewable energy sources imposes increasingly stringent demands on deep peak shaving capability and ultra-low-load operation of coal-fired power generating units, thereby presents more severe challenges to the safe operation of steam turbine units under low-load conditions. This paper employs numerical simulation methods, focusing on an in-depth analysis of the operational performance of the last stage of a steam turbine under low-load conditions, and explores various solutions for their working mechanisms and optimization effects under ultra-low-load conditions. It is found that, when the unit transitions from medium-low load to ultra-low load, vortex clusters such as gap vortices, backflow vortices, and separation vortices emerge near the last stage blades, with their extent gradually expanding as the load decreases. Reducing the back pressure of the unit and operating the low-pressure cylinder with cylinder-cutting are effective strategies to attenuate steam turbine vortex flow and enhance the last stage’s performance, with a combined application of these strategies yielding better results. For instance, under 20% turbine heat acceptance (THA) conditions, reducing the back pressure from 4.9 kPa to 2.5 kPa significantly diminishes the influence range of the last stage vortex cluster, increasing the rotor blade torque from −38 N·m to 73 N·m, thereby markedly improves the last stage performance. Under 10% THA conditions, employing a combination of reduced back pressure and low-pressure cylinder-cutting can completely eliminate the tip clearance vortex, with the radial lengths of the backflow vortices and separation vortices reducing by more than 50%. The optimized rotor blade torque increases by approximately 130 N·m, significantly enhancing the last stage performance.

In order to inhibit the flow separation on blade surface and improve the aerodynamic performance of the blade, the design scheme of installing vortex generator on the blade surface is proposed. Taking DU97-W-300 blade section with vortex generator as the research object, the orthogonal experimental design method is used to investigate the influences of height, length, installation angle, chord installation position, spacing and pitch of the vortex generator on the aerodynamic performance of the blade section, so as to determine the basic law of vortex generator parameter design. The results show that, the vortex generator parameters that affect the magnitude of aerodynamic performance of the blade are as follows: spacing, pitch, length, height, chord installation position, and installation angle of the vortex generator. The optimal vortex generator parameter combination law is: height of 0.75ξ (ξ is blade boundary layer thickness), length of 1.6ξ, installation angle of 20°, chord installation position is 10% blade chord length, spacing of 1.6ξ, pitch of 0.8ξ, which can increase the maximum lift coefficient of this blade by 40% and the maximum stall angle of attack by 9.5°.

Due to the characteristics of the medium transported by medium speed coal mill and the limitations of the inlet pipeline and space, the testing method under cold pure air conditions cannot guarantee the timeliness of the calibration test for the inlet air volume. Under hot conditions, the outlet pipeline of the coal mill was selected as test object for its stable flow field. The dynamic pressure and pulverized coal distribution characteristics of each powder pipe were tested by the equal cross-section grid method. The flow velocity of the air-powder mixture was obtained by the cyclic iterative method. Finally, the inlet air volume of the coal mill was compared and calibrated by the difference between the measured air-powder mixture flow rate, the coal quantity and the design sealing air volume. The practical results show that, on the basis of the same measured original data, the inlet flow rate obtained by the method above is closer to the real value, the accuracy can be improved by about 15 percentage points compared with the calculation results with cold conditions method. This method is simple to test and practical, which can effectively improve the timeliness and accuracy of the inlet air volume calibration results of medium-speed coal mill under hot conditions, and at the same time, it also has a certain guiding role in test of the flow rate of powder-containing gas in similar industrial environments.

In order to explore the film cooling potential of crater holes, numerical simulations are performed to investigate the film cooling characteristics of equal-section crater hole, concentric elliptical crater hole, and two types of rounded corner crater holes proposed on the basis of these two types of crater holes. Cooling efficiency curves are analyzed for four types of crater holes at blowing ratios of 0.5, 1.0 and 1.5. The results show that, the crater spreading width of crater holes and crater film holes with rounded corners increases, which is beneficial to spreading coverage of the cooling film. After the crater holes are rounded at three blowing ratios, the Coanda effect strengthenes the ability of the cooling jet to adhere to the wall, and the film cooling efficiency in the near-hole region improves significantly. As the blowing ratio increases, the area-averaged film cooling efficiency after the rounded corner treatment increases by 76%, 139% and 155%, respectively, for the equal-section crater hole. The area-averaged film cooling efficiency improves by 18%, 27%, and 29%, respectively, for the concentric-elliptical crater hole with rounded corner compared with that of the concentric-elliptical crater hole.

It is difficult to control NO_x emissions during full load operation of a 660 MW supercritical circulating fluidized bed (CFB) boiler in a certain power plant, and its instantaneous value is prone to exceed the ultra-low emission limit. In addition, the selective non-catalytic reduction (SNCR) system has a high ammonia consumption and severe ammonia escape issues. To solve these problems, on-site experiments on NO_x original emissions, SNCR denitrification efficiency, CO mass concentration and bottom slag combustibles were conducted, and optimization experiments on secondary air volume layout were also performed. It was found that, the original NO_x emissions of the CFB boiler were relatively low, with a maximum of 120 mg/m³ (standard condition) during full load operation and a NO_x mass concentration below 50 mg/m³ during medium and low loads. However, there was a significant deviation in NO_x mass concentration between the front and rear ends of the furnace, and the NO_x in flue gas was mainly generated in front of the furnace. The reason why NO_x emissions are difficult to control is due to the low denitrification efficiency of SNCR and uneven coal feeding in the furnace. The SNCR denitrification efficiency at inlet of the 6 separators was all below 50%, among which the denitrification efficiency of four separators B, C, E, and F was below 40%. Furthermore, according to the distribution of parameters in the furnace depth direction, such as the bed temperature, the content of combustible materials in bottom slag, and the variation of CO mass concentration, it can be determined that the uniformity of coal feeding in the furnace also had a significant effect on the control of NO_x emissions at full load. Currently, the power plant cannot achieve uniform coal feeding without renovation, but the original NO_x generation can be reduced by adjusting the secondary air volume ratio in the depth direction of the furnace, with a reduction of up to 9.77%.

In order to solve the problem of low accuracy of wind power prediction caused by wind speed uncertainty and volatility, this paper proposes a VMD-ISSA-GRU combination model based on variational mode decomposition (VMD), improved sparrow search algorithm (ISSA) and gated recurrent neural network (GRU). Firstly, the center frequency method is used to determine the number of modal components after VMD decomposition, which can effectively avoid over-decomposition or insufficient decomposition. Then, chaotic mapping, nonlinear decreasing weights and a mutation strategy are introduced to improve the sparrow search algorithm to optimize the gated recurrent neural network, and then an ISSA-GRU prediction model is established for each decomposed subsequence. Finally, the predicted value of each subseries is superimposed and the final predicted value is obtained. The experimental results show that, the mean absolute error, mean absolute percentage error and root mean square error of the VMD-ISSA-GRU model are 1.211 8, 1.890 0 and 1.591 6 MW, respectively. Compared with the conventional GRU, long short-term memory (LSTM) neural network, Bi-directional LSTM (BiLSTM) neural network model and other combination models, the prediction accuracy has been significantly improved, which can solve the problem of low prediction accuracy of wind power.

In the context of current energy structure transformation, conventional thermal power would gradually transform into grid source support and system regulation. Coupling with distributed photovoltaic power is an effective attempt for thermal power enterprises to achieve cost reduction and efficiency improvement. However, due to the lack of relevant guidance for the connection of non centralized power sources for the factory use, there is a lack of evaluation strategies and empirical references for system security and stability. For this purpose, taking the thermal photovoltaic complementary energy supply system of a thermal power plant in northwest China as an example, its operating characteristics are analyzed and a technical framework for stability evaluation is provided. In examples of different power units, grid connection levels, and minimum photovoltaic unit layout, application evaluation issues such as static power flow, transient stability, and power quality are discussed. It is calculated that the power consumption reduction efficiency of thermal power units in this case achieves an improvement of 18%~42%. This conclusion has typical reference significance for the application of the power generation technology model of “distributed photovoltaic access to plant use systems” in thermal power plants.

Solar power plants can be complementary to other new energy power generation stations, and can also undertake the task of peak modulation and frequency modulation of power grid, which have attracted more and more attentions. In this paper, the dynamic simulation model of thermal storage system and power generation system is built and verified by Apros software. The coordinated control system of solar power plant considering the influence of heat storage is designed, and the maximum variable load rate of the solar power plant in different load intervals is studied. The results show that the proposed coordinated control strategy has a good control effect. Compared with the control without heat storage control, the deviation of main steam pressure with heat storage control reduces from 0.17 MPa to 0.07 MPa. Under the set limit conditions, the maximum load rise rate of 100%THA~75%THA load interval is 11.57%/min, and the maximum load reduction rate is 8.94%/min. The results can provide reference for peak shaving and frequency modulation operation of photothermal power plants.

In view of the increasingly serious problem of power grid peak regulation caused by the instability of new energy, combined with the relatively mature photo-coal complementary power generation technology and the multi-heat source combined heating peak shaving system, the light-coal mixed heating power generation system was designed to make the cogeneration unit have a certain peak regulation capacity. Based on the actual operating conditions of the heating unit and the premise of ensuring the heating load, the coupling mode of the solar-assisted dual-engine cogeneration unit was analyzed, and the peak regulation performance of the two-engine was compared before and after coupling. The results show that, a dynamic throttle valve is installed on the pipeline between the condenser outlet and the heat exchanger of the solar collector system, and the operation mode of the auxiliary heating unit of the solar collector system can be changed, which can realize flexible operation of the integrated system of power generation, heating and peak regulation. Among them, the solar thermal collection system is only used for supplementary heating, the peak regulation capacity ratio is 0.76, and the ratio of solar auxiliary double-heating supply before and after peak regulation capacity is 0.55. The No.1 unit which is assisted by solar energy to bear the maximum heating load has the best performance in peak regulation capacity and peak regulation compensation.