This study aimed to clarify the variation law of head loss along aerated pipelines, explore the impact of aeration rate on the hydraulic performance of water-air two-phase flow in pipelines, and establish a reliable calculation method for head loss along aerated pipelines. The goal was to provide theoretical guidance and technical support for the hydraulic design of aeration irrigation systems. An automated water-air aeration irrigation system was constructed based on a programmable logic controller (PLC), consisting of a water source, pipeline system, variable frequency water pump, aeration device, valves, and measurement instruments. The pipeline used was a horizontal PVC pipe with an outer diameter of 32 mm and a wall thickness of 3 mm. A full factorial experiment was conducted with 3 water head levels (11, 17, 22 m) and 8 aeration rates (ranging from 0-1.33×10⁻³ m³/s), resulting in 24 working conditions. For each condition, measurements were taken for 5 minutes after stabilization, repeated 3 times, and the average value was used. Flow rate was measured by an intelligent electronic water meter, aeration rate by a gas mass flowmeter, and water head by pressure transmitters installed at 5 positions along the pipeline. Regression analysis was applied to establish relationships between variables, and the proposed calculation formula was verified through specific working conditions. The results showed that aeration had an inhibitory effect on the average pipeline flow rate. The maximum inhibition rate was 3.81% when the aeration rate was 1.08×10⁻³ m³/s. Both water head and aeration rate, as well as their interaction, had significant effects on the flow rate (P<0.05 or P<0.01). For aerated pipelines, a higher pressure was required compared to pure water pipelines. The pipeline pressure increased with the aeration rate, with an approximate 3 m increase for every 1×10⁻³ m³/s increment in aeration rate, and it was jointly affected by water head and aeration rate. Along the pipeline, pressure decreased with increasing length, and the decrease rate tended to slow down, which was consistent with the variation in pure water flow; higher aeration rates led to higher pressures. A calculation formula for head loss along aerated pipelines was established, considering the effects of aeration rate on resistance coefficient and flow velocity. Verification results indicated that the error between calculated and measured values ranged from 0.2% to 1.6%, confirming the formula's reliability. This formula was applicable to horizontal circular pipes with bubbly flow, gas content between 0-50%, initial pressure between 11 and 22, and Reynolds number above 70 000. Aeration rate exerts dual effects on pipeline hydraulic performance: increasing pipeline pressure and slightly inhibiting flow rate, with the overall impact within an engineering acceptable range. The established calculation formula for head loss along aerated pipelines, with high reliability, provides an important theoretical basis for hydraulic calculation and optimal design of aeration irrigation systems, especially facilitating pressure compensation and flow control balance in hilly areas by adjusting aeration rate.

This study aims to explore the influence of water extraction and system configuration on the performance of photovoltaic pumps. The water extraction system was required for the high efficiency, high utilization rate of solar energy, and cost saving in the photovoltaic pump. The circulating water extraction was also selected to improve the conversion efficiency of the photovoltaic module, the pump operation efficiency, and pipeline efficiency under different irradiation intensities, valve opening, and water extraction height. The flow model was then constructed. The irradiation intensity data that was monitored in 2022 was partitioned to calculate the proportion of radiation intensity in each partition using the flow model. The amount of water extraction was calculated to evaluate the parameters of the system in each range of radiation intensity under different heights. The optimal height of water extraction was then determined, according to the overall efficiency of the water extraction system and the utilization rate of solar energy. There was an increase in the area of photovoltaic modules and the number of reservoirs. The utilization rate of solar energy was improved in the water-lifting system, where the cost was reduced significantly. The optimal area of photovoltaic modules and the number of reservoirs were obtained at the lowest cost of the water-lifting system. The results show that there was a significant relationship between the utilization efficiency of photovoltaic modules and the irradiation intensity. Some variations were also found in the pump operation efficiency with the irradiation intensity and valve opening, in order to determine the high-efficient operation interval of the photovoltaic pump and the valve opening. At the same time, the optimal height of water lifting was determined as 20 m in the photovoltaic pump, according to the utilization rate of solar energy and the overall efficiency. Meanwhile, the utilization rate of solar energy was 65.05 %, the overall utilization efficiency was 4.521%, and the water lifting cost was 0.151 yuan/m³. The optimal height of water lifting was utilized to clarify the influence of the increasing area of photovoltaic panels and the number of reservoirs on the utilization rate of solar energy and water lifting cost. Once the water lifting cost was the lowest, the area of photovoltaic panels, water lifting cost, and solar energy utilization rate were 3.71 m², 0.151 yuan/m³ and 90.83%, respectively. When the number of reservoirs was 4, the water lifting cost and solar energy utilization rate were 0.145 yuan/m³ and 94.62%, respectively. Therefore, the increasing area of photovoltaic panels and the number of reservoirs greatly contributed to the cost saving of water lifting and the solar energy utilization rate. There was the application range and complementary relationship between valve opening and opening/closing under different irradiation intensities. Two application scenarios were introduced to improve the solar energy utilization rate. The finding can provide new ideas to optimize and apply the photovoltaic water pumping.

A mesh filter is one of the key components of micro-irrigation systems, which plays an important role in filtering impurities and slowing down dripper blocking. The filter head loss tends to increase with the increase of intercepted impurities, resulting in screen breakage or forcing system shutdown. This study adopted the method of inductive analysis of literature data to carry out K-means cluster analysis on the head loss data of vertical, composite, horizontal, torpedo, flap, Y-type and hand-cranked cleaning of 7 types of mesh filters at different stages, and summarized the trend of dynamic change of head loss. Then, in order to clarify the reasons for the surge in head loss for the Y-mesh filter, the study designed three types of flow rates of 2.5, 3.5, and 4.5 m³/h, three sediment concentrations of 60, 80, and 100 mg/L and four grades of sand-containing water mainly of >54-75 ( Grade Ⅰ ), >75-100 ( Grade Ⅱ ), >100-125 ( Grade Ⅲ ), and >125-150 μm ( Grade Ⅳ) respectively, and carried out a full-scale experiment to test the effects of different flow rates, sediment concentrations, and sand grades on the head loss of the filter. With the main objectives of reducing the head loss surge and improving the sand stopping effect, a CRITIC-TOPSIS comprehensive evaluation was carried out with the evaluation indexes of increase rate of head loss during steady increase stage, increase rate of head loss during sudden increase stage, clogging uniformity, total operation time, total head loss and desanding rate to optimize the suitable operating conditions of the Y-filter. The results showed: 1) The change in different types of mesh filters head loss over time was divided into a steady increase stage and a sudden increase stage, the sudden increase in the stage of the head loss had larger growth rate and shorter operation time; The ratio of the duration of both stages was greater than 0.5, and the filter clogging uniformity was greater than 1. 2) Under the same flow rate and concentration, grade Ⅲ and grade Ⅳ were more likely to produce head loss surge than grade Ⅰ and grade Ⅱ. Under the same flow rate, the head loss surge was more likely to occur under high concentration conditions. Under the same concentration, the head loss surge was most likely to occur when the flow rate was 3.5 m³/h. 3) The results of CRITIC-TOPSIS comprehensive evaluation showed that the top three indexes affecting the hydraulic performance were 100-125, 125-150 and 75-100 μm water with the flow rate of 2.5 m³/h and the sediment concentration of 60 mg/L, and their comprehensive score indexes were 0.726, 0.712 and 0.711, respectively. The combinations of low sediment concentrations and larger particle gradations, as well as those with high sediment concentrations and smaller particle gradations, performed well at a flow rate of 2.5 m³/h. However, when the flow rate increased to 4.5 m³/h, the combinations of the higher sediment concentrations and the larger particle sizes exhibited superior comprehensive performance. In contrast, those with low sediment concentrations and small particle gradations demonstrated relatively consistent performance across all the three flow rates tested. The study can provide valuable information for reducing head loss and increasing operation time of filter.

A fuzzy adaptive control system was presented for greenhouse temperature, according to heat balance and fuzzy control. The accuracy of temperature control was improved to reduce the energy consumption of the control system in the winter greenhouse. An adaptive adjustment module was introduced for the output membership functions using the heat balance equation in the system. The membership functions of output variables were real-time adjusted with the outdoor temperature in the upper computer. The target temperature was ultimately reached to be stable in the greenhouse. At the same time, the experiment was conducted to verify the fuzzy adaptive control. The final experimental results were as follows: (1) The temperature was set to be 30, 35, 40, and 45 ℃ for the water tank of the heating fan. The temperature inside the greenhouse was then monitored for a period of time. The monitoring data was substituted into the energy balance equation to calculate the comprehensive heat transfer coefficient of the heating fan. 19 datasets showed that the comprehensive heat transfer coefficient of the heating fan was 50.50 W/(m²·℃). (2) A fuzzy adaptive control system was developed for greenhouse temperature using Python. A comparison was made on the control effects of fuzzy control, adaptive fuzzy, and threshold control. The more sensitive output response of the fuzzy adaptive control was observed at the target temperature of 20 ℃, according to the heat balance equation. The higher temperature was found in the water tank of heating fan at the beginning of the control. The overall control time was shorter at 35 min. Finally, the temperature of the temperature chamber was stabilized at (19.8 ± 0.11) ℃. There was a longer control of 39 min for the general fuzzy controller. Finally, the greenhouse temperature was stabilized at (13.5 ± 0.5) ℃, which was unable to reach the target ambient temperature. The threshold control had the shortest control time of 26 min. But there were more fluctuations to reach the target temperature until the greenhouse temperature was stabilized at (20.0 ± 0.85) ℃. (3) The ratio of heat input was calculated from the heating fan to the total energy consumption of the greenhouse using different control systems. The energy utilization rate of fuzzy adaptive control was 45.97% when the total energy consumption was 1.584 × 10⁷ J. While the energy utilization rate of threshold control was only 20.21% when the total energy consumption was 3.301 × 10⁷ J. Therefore, low energy consumption, high stability, and accuracy were achieved in the fuzzy adaptive control system with the heat balance equation, fully meeting the needs of temperature control in a winter greenhouse.

Greenhouse is one kind of protected cultivation facility with plastic film as the covering material and bamboo or steel frame as the supporting structure. Solar radiation is one of the most important influencing factors on the thermal energy environment inside the greenhouses. Only the greenhouse effect without heating can make the internal temperature higher than the outside in the cold regions. The solar radiation received by a greenhouse is strongly related to some parameters, such as geographical location, climatic conditions, orientation, and shape. Therefore, it is very necessary to optimize the shape, orientation, and size of greenhouses, in order to maximize the use of winter solar radiation and then effectively reduce winter heating requirements and operating costs. The optimal shape and orientation of greenhouses can vary slightly in the height of the crop canopy, such as fruit, leafy vegetables, and flowers. However, it is still lacking to consider the canopy height of the crops in the greenhouse structure, according to the capture of solar radiation on the lighting surfaces. In this study, a novel model was developed to optimize the ridge-shape greenhouse using canopy height and constant volume constraints. The amount of solar radiation was also maximized to capture the lighting surface and the effective planting area. A systematic analysis was implemented to explore the influence of the greenhouse height ratio and azimuth angle on solar radiation capture under the constant internal energy demand. The optimal combination of parameters was achieved in the different ridge ratios and regions. More light was harvested and converted at the expense of the greenhouse into heat stored in the greenhouse, thus reducing night-time heating costs. A comparative analysis was also made to verify the calculated and measured values of the solar radiation model. The results show that the solar radiation captured by the greenhouses was positively correlated with the height and ridge ratio. The difference in solar radiation with different ridge ratios decreased with the decrease in height ratio. The amount of solar radiation captured inside the greenhouse increased with the decrease of regional latitude at the same height ratio. Most solar radiation showed a decreasing and then increasing trend with the increase of azimuth angle. The preferred height ratios in different regions were related only to the height of the crop canopy. The higher the latitude under the same conditions was, the greater the ridge ratio and canopy height were. The greater angle of azimuth was preferably obtained by the greenhouse deflected with respect to the north-south direction. This finding can improve the thermal insulation and heat storage with heating cost savings in the greenhouse. A theoretical basis can also offer to advance the overall planning and development of greenhouses.

A disc filter is one of the key components in micro-irrigation systems, and plays an important role in filtering impurities and reducing clogging of emitters. However, the disc filter cannot fully meet the filtration requirements of different impurity particle sizes, due to a single type of discs and a narrow range of sand grain sizes for filtration. In this research, a disc filter with an adjustable filter mesh size was proposed to reasonably change the tightness between discs. The disc filter also met the filtration requirements in the different ranges of impurity particle size, in order to reduce the manufacture and operation costs. A series of tests was carried out on the hydraulic performance of disc filters with different mesh. Five flow rates of 10, 15, 20, 25, and 30 m³/h were then set to test the head loss in the conditions of clear water with different mesh sizes of disc filters. In addition, the head loss and sand interception of disc filters were evaluated with different mesh numbers under different grades and contents. Three grades were selected as the small, medium, and large sandy water with less than 75, 75−150, and 150−300 μm sand particles and three sand contents of 0.8, 1.0, and 1.2 g/L. The results show that: (1) Different objectives of mesh filtration were achieved to adjust the disc tightness. Three types of discs were used to obtain 7 levels of tightness under three motor pressures, corresponding to filter mesh sizes of 50, 60, 75, 100, 120, 150, and 200. (2) There were some differences in the head loss dynamics and sand interception of the 7 mesh disc filters. In small graded sandy water, the 200-mesh disc piece shared the largest peak head loss, where all maximums were stabilized at about 16 m. The sand interceptions of the 200-mesh disc were 54, 73, and 84 g, which were significantly larger than that of others (P<0.05). In intermediate-graded sandy water, the head loss was greater than for 120, 150, and 200 mesh discs, with the maximum exceeding 6 m. The sand interceptions for 120 and 150 mesh discs were 72, 92, and 103 g, and 81, 92, and 95 g, respectively, which were significantly greater than that of the others (P<0.05). In large grades of sandy water, the 50, 60, 75, and 100 mesh discs all shared greater sand interceptions and increased head loss. (3) The optimization configuration of the filter mesh size was achieved using the TOPSIS. Therefore, a 200-mesh disc should be chosen in small graded sandy water. A 120-mesh disc should be chosen in intermediate-graded sandy water when the content was high, and a 150-mesh disc should be chosen when the content was low. A 50- or 60-mesh disc should be selected in large grades of sandy water when the content was high, and a 75- or 100-mesh disc should be chosen when the concentration was low. The best filtration was achieved to effectively avoid the hidden danger of head loss surge. The finding can provide a strong reference for the rational selection and use of disc filters under different sand contents in micro-irrigation systems, in order to reduce the head loss of the filter

Droplet velocity and particle size determine droplet kinetic energy and have a major impact on soil erosion, crop leaf strike and farm microclimate. The equivalent droplet velocity and diameter describe the average characteristics of the droplet and they are important parameters for measuring the spray quality of the nozzle and the degree of droplet fragmentation. Traditional droplet testing methods can only measure number and particle size, so the equivalent method previously used cannot calculate the average droplet characteristics in terms of droplet energy. With the widespread use of optical instruments in sprinkler tests, droplet velocities can also be measured and the corresponding methods for calculating droplet equivalent indicators should be improved and developed. This study proposed an energy weighted method for calculating droplet equivalent indicators. Based on droplet data sprayed by five types of sprinkler nozzles, the characteristics, and differences between the calculation results of the energy weighted method and other types of methods were compared. The regression relationship between energy weighted equivalent indicators and other types of indicators was established. The results showed that: 1) The energy weighted equivalent droplet diameter was the largest, followed by the equivalent method related to droplet volume, and the smallest is the equivalent method related to droplet number. The overall trend in droplet equivalent diameter related to energy and volume along the radial direction was relatively similar, but there were significant differences at the proximal end of the spray. This is because although a larger proportion of smaller droplets occupy the near end of the spray water, there are also a certain number of large droplets which, after being ejected from the nozzle outlet, fall steeply to the ground without being sufficiently broken up. Large droplets carry a greater kinetic energy and contribute more to the energy at the measurement point, so the energy weighted droplet equivalent diameter is more biased in favour of these large droplets. 2) The droplet equivalent velocity and equivalent diameter calculated by the energy weighted equivalent method can characterise droplets with a high energy contribution. The histogram of the distribution of the number of droplet velocities showed that droplets with velocities less than 6 m/s occupied a large proportion of the droplets. The IWOB nozzle, for example, had a number weighted equivalent velocity of 3.93 m/s, corresponding to a droplet number accumulation frequency of 29.7%, but an energy accumulation frequency of only 4.5%. The energy weighted equivalent droplet velocity was 4.55 m/s. The number of droplets less than this velocity carries about 43.8% of the energy and the number of droplets greater than this velocity is about 21.4%. This velocity was between the maximum velocity and the number-weighted equivalent droplet velocity and may represent the velocity characteristics of a large droplet carrying more energy. 3) There was a good exponential regression between the droplet terminal velocity calculated by the empirical formula and the energy weighted equivalent droplet velocity, and there was a good exponential regression between the equivalent droplet diameter related to volume and the energy weighted equivalent droplet diameter, with correlation coefficients greater than 0.80. 4) The energy weighted equivalent droplet kinetic energy provided a better estimate of the kinetic energy of precipitation per unit time and area, with a coefficient of determination of 0.84 for the logarithmic regression relationship. The results of the study may provide ideas for reflecting the average characteristics of droplets from an energy perspective.

In order to solve the immaturity of decision-making methods in the regulation of winter heating in greenhouses, this study proposed a solution to the problem of greenhouse winter heating regulation using a dynamic programming algorithm. A mathematical model that included indoor environmental state variables, optimization decision variables, and outdoor random variables was established. The temperature is kept close to the expected value and the energy consumption is low. The model predicts the control solution by considering the cost function within the next 10 steps. The two-stage planning method was used to optimize the state of each moment step by step. The temperature control strategy model was obtained by training the relationship between indoor temperature, outdoor temperature, and heating time after optimization using a regression algorithm. Based on a typical Internet of Things (IoT) structure, the greenhouse control system was designed to regulate the optimal control according to the feedback of the current environment. Through testing and verification, the optimized control method could stabilize the temperature near the target value. Compared to the threshold control (threshold interval of 2.0°C) under similar weather conditions, the optimized control method reduced the temperature fluctuation range by 0.9°C and saved 7.83 kW·h of electricity, which is about 14.56% of the total experimental electricity consumption. This shows that the dynamic programming method is feasible for environmental regulation in actual greenhouse production, and further research can be expanded in terms of decision variables and policy models to achieve a more comprehensive, scientific, and precise regulation.