Building an efficient and pollution-free power generation system is an effective means to solve the current energy shortage and environmental pollution problems. By taking the C65 micro gas turbine produced by Capstone Company as the core power generation component, and coupling with the thermochemical process of solar powered ammonia decomposition to produce hydrogen, this article achieves multi-energy complementarity between renewable energy and ammonia chemical energy. The organic Rankine cycle is used as the bottom cycle to recover the waste heat from the flue gas generated by the micro gas turbine and generate electricity, achieving cascade energy utilization. A detailed simulation process is constructed in the chemical simulation software Aspen Plus. The results show that the complementary use of solar energy and ammonia has improved the calorific value of the generated hydrogen rich synthesis gas. The output power of the micro combustion engine is 89.95 kW, which is 24.95 kW more than the C65 micro combustion engine in the reference system. The electrical efficiency of the system under design conditions reaches 44.81%, and the thermal efficiency is 47.97%, which are 8.51 percentage points and 9.67 percentage points higher than that of the reference system, respectively. The component having the largest exergy loss in the system is the combustion chamber, accounting for 41.67% of the total damage, followed by the evaporator and regenerator, accounting for 14.31% and 11.15%, respectively. Sensitivity analysis shows that the electrical efficiency and thermal efficiency of the system decrease and increase with the increase of solar energy collection, respectively. The research results provide a reference for a distributed micro turbine power generation system using ammonia gas as fuel and coupled with solar energy.

Labyrinth seals are widely used in various types of turbomachinery due to their simple structure, convenient maintenance, and long service life. The shunt injection devices can reduce the flow-induced vibration caused by the spiral effect and improve the stability of the sealing system by affecting the circumferential flow inside the seal cavity. The three-dimensional numerical models of shunt injection labyrinth seal were established to calculate and analyze the impact of the shunt injection nozzle on the dynamic characteristics of the seal under different structural parameters. The results show that the smaller the tilt angle of the anti-swirl nozzle, the greater the system damping and stability. When the tilt angle is 30°, the effective damping is 4 times that of the vertical angle incident; the shape of the anti-swirl nozzle has a small impact on the sealing dynamic and flow characteristics. The cross stiffness of both nozzle hole types is negative, and the difference in cross stiffness between the two is about 5 kN/m at low frequencies and 1~2 kN/m at high frequencies; the more nozzles there are, the more they can suppress the circumferential flow of the rotor, which is beneficial for system stability.

In order to achieve the desired flexibility, high efficiency, and cost-effectiveness in the startup and operation of thermal power units, the utilization of the BEST small steam turbine with a small generator for the implementation of a double-turbine reheat system unit is crucial for enhancing the operational economy of the unit. According to the starting mode of the BEST system and unit, combined with the historical process and data of the starting and operation of the debugging and adjustment test, a characteristic analysis test of the BEST system in multi-mode startup and operation was conducted. The existing control logic was optimized, and an operation control strategy for the BEST small steam turbine with a small generator was proposed. The system addresses the issue of lacking control strategies in various aspects, such as the starting and control of the BEST system, converter start-stop control, BEST small steam turbine and converter non-disturbance switching, run back, load dumping conditions, and ensures uninterrupted operation control of the entire process of the BEST system. After optimization, the crucial parameters of the BEST system remain secure and stable during operation. The control method holds significant reference value for similar units equipped with the BEST system.

To study the coupling and oscillation characteristics of power equipment in microgrid, the energy functions of the wind turbine subsystem, generator and excitation subsystem in the doubly-fed wind turbine are deduced based on the transient energy flow method taking into account the wind speed and the control strategy of the unit. Then, the mechanism of the change of the energy consumption of each subsystem is investigated when the wind speed, the control parameters of the unit and other operational parameters change, and the oscillation characteristics of the unit are analyzed. Finally, the energy change and power oscillation characteristics of the doubly-fed wind turbine when the operation parameters change are analyzed by modeling and simulation on PSCAD/EMTDC platform, and the results are compared with the eigenvalue calculation results to verify the reasonableness of the analysis. At last, the influence mechanism of wind speed change on the oscillation of doubly-fed wind turbine is obtained.

To address the challenges posed by the reverse peak shaving characteristics of new energy generation units to the smooth operation of the power grid, coal-fired units urgently need to improve their flexible operation and deep peak shaving capabilities. This article proposes three schemes of molten salt heat storage and heat release for a 670 MW reheating unit, including using a steam ejector to allocate the steam inlet flow rate of the reheater. By using Ebsilon to establish the thermal model, this article analyzes the performance of the coupled system. The results show that all schemes can effectively expand the peak shaving range of the unit. Under energy-storage conditions, the thermal economy of steam-extraction is better than using electrical heating at the same peak shaving depth. The heat-storage scheme of integrating steam ejector to allocate extraction steam to compensate for reheat inlet flow can effectively solve the problem of reheater over temperature caused by a large amount of extracted main steam. Under heat-release conditions, using molten salt to heat high pressure feed water can acquire better thermal and economic benefits. In the combination scheme of heat storage and release, C1-S2 exhibits the best economic performance, with an upward peak shaving depth of 76.89 MW, and a cyclic thermal efficiency and thermal efficiency of 42.48% and 41.31%, respectively.

The urea hydrolysis technology for ammonia production has been widely used in the preparation of denitration reducing agents for thermal power units. However, if the quality of urea is not up to standard, the urea hydrolyzer will leak, and the drainage from the urea hydrolyzer will be reused in the condenser, which will cause great harm to the thermal system. The article analyzes the serious salt accumulation and superheater tube explosion in the water and steam system caused by the leakage of a urea hydrolyzer in a coal-fired unit, and proposes a solution to the salt accumulation problem. The problem has been successfully solved, after the unit is started, all quality criterion of water and steam meet the requirements of Quality Criterion of Water and Steam for Power Plant and Steam-generating Equipment (GB/T 12145—2016). This article provides a solution for analyzing and treating the cause of salt accumulation in the water and steam system for reference.

In order to study the effect of backpacking containing barite powder on the heat transfer efficiency of buried pipe boreholes in plain and mountainous areas of Beijing, a comparative analysis of laboratory experiments and field thermal response experiments was carried out. The quaternary boreholes in plain areas were backfilled with medium sand and the bedrock boreholes in mountainous areas were backfilled with cement mortar. When the specific gravity of medium sand barite powder was 5%, the thermal conductivity of medium sand backfill samples increased by 14%. When 5% barite powder was added to cement mortar, the thermal conductivity increased 7.3%. According to the field thermal response test results, under summer conditions in the same site, the heat transfer rate of a backfilling borehole containing barite powder increased by 2.4 W/m and 3.5% per meter compared with that of the medium-sand backfilling borehole in plain area. The heat transfer rate of cement mortar backfill containing barite powder increased by 2.7 W/m and 3.9% per meter. The numerical simulation model of the quaternary system and bedrock area was established. It was found that the content of barite powder increased to 10% and the heat transfer rate of boreholes increased by about 6.0%. In general, the heat transfer capacity of buried pipe is improved and its sustainability gets better after adding barite powder.

In industrial production processes, time delays can have adverse effects on the performance of control systems, and may even lead to system instability. This article investigates the stability issues of time-delay in the load/speed control loop of a heavy-duty gas turbine from the perspective of switching systems. The model of GE MS109FA 275 MW heavy-duty gas turbine under 100% load is taken as the research object. The load/speed control loop with time-varying delay is transformed into a class of switching system by augmenting the state variable and selecting the change of time delay as the switching signal. By using the norm correlation lemma, a necessary and sufficient condition to ensure the stability of the load/speed control loop with time-varying delay is derived and the stability verification algorithm is given. The hardware-in-the-loop simulation is carried out based on the domestic heavy-duty gas turbine NuCON control system. The results of this study can provide theoretical references for the design and parameter adjustment of heavy-duty gas turbine control system.

By the end of 2021, over 95% of coal-fired thermal power units in China have achieved ultra-low emission of nitrogen oxides, with the remaining being W-flame boilers that burn anthracite. Due to the high mass concentration of nitrogen oxides generated, which often reaches 750~1 200 mg/m³, achieving ultra-low emissions is difficult, making it the “last mile” for China to achieve ultra-low emission policies. At present, selective catalyst reduction (SCR) denitration flow field technology mainly includes “SCR partition hybrid dynamic leveling technology”, “full flue section mixing flow field technology”, and “conventional accurate ammonia injection technology”, etc. Taking a W-flame boiler of which the design denitration efficiency needs to be up to 95% as an example, this paper compares the performance indicators of various technologies through CFD simulation, and the indicators of the “SCR partition hybrid dynamic leveling technology” are significantly superior to other technologies. After the project transformation, when the mass concentration of nitrogen oxides at the denitration system inlet is 1 000 mg/m³ and that at the system outlet is lower than 50 mg/m³, the ammonia escape can be kept less than 3 μL/L, far exceeding the maximum design efficiency of the conventional SCR denitration system. The research provides a new technical route for ultra-low NO_x emission of W-flame boilers.

H₂S is an important product produced by power plant boilers in the process of low NO_x combustion. To solve the problems that H₂S may cause various hazards to thermal power plants due to its inflammability, strong corrosion and extreme toxicity, tunable diode laser absorption spectroscopy (TDLAS) method combined with multi-pass cell and computer is employed to build an online measurement system for detecting the molar fraction of low-concentration gas. By using this measurement system, accurate online measurement of H₂S in the mixed gas with the molar fraction of 10^–6 magnitude is realized, and the H₂S high-temperature reaction experiment is carried out to explore the influence of experimental temperature and the molar fraction of O₂ in the mixed gas on the reaction. The experimental results show that, under the conditions of pressure of 80 kPa and molar fraction of O₂ ranging from 0 to 5%, the temperature at which H₂S begins to react changes with the molar fraction of O₂. On the whole, the higher the molar fraction of O₂ in the mixed gas, the lower the temperature at which H₂S begins to react. The experimental results can provide some data basis for the generation, transformation and harm control of H₂S in boiler flue gas.