沼液滴灌系统灌水器堵塞模型构建及系统参数优化

在沼液滴灌工程实际生产应用中,为有效预防灌水器发生堵塞,提高沼液滴灌系统运行的可靠性,该文以实际沼气工程发酵剩余的沼液为试验样本,从满足作物生长需求、合理调控系统运行模式的角度出发,以沼液滴灌系统水肥配比、灌水压力、滴头流量为影响因素,以灌水器的平均相对流量和首次发生堵塞的时间为试验指标进行试验研究,建立了沼液滴灌系统灌水器堵塞预测模型。试验采用响应曲面法,利用Design-Expert8.0.6软件回归分析法和响应面分析法,建立了3个因素对沼液滴灌系统灌水器堵塞影响的数学模型,对所建立的数学模型进行了试验性验证。试验分析结果表明:水肥配比、灌水压力和滴头流量对沼液滴灌系统灌水器平均相对流量和首次发生堵塞时间的影响都是显著的,且影响主次顺序均为:滴头流量>水肥配比>灌水压力。在较大的水肥配比和滴头流量条件下,平均相对流量最大,首次发生堵塞时间最长;当灌水压力取适当的中间值时,灌水器抗堵塞性能较好。响应曲面法优化后获得的最佳综合堵塞模型指标为:水肥配比为3:1,灌水压力为0.14 MPa,滴头流量为12 L/h,在该条件下,平均相对流量为0.83,堵塞时间为55 h。经试验验证,实测值与模型理论值的平均相对误差小于4%,表明模型预测效果良好,能够较为准确地预测灌水器堵塞风险和首次发生堵塞的时间。

Development of emitter clogging predication model for drip irrigation system with biogas slurry and optimization of its system parameters

In actual application of drip irrigation project with biogas slurry, emitters clogging occurs frequently. This study established models for predicting clogging of emitters and optimized system factors of drip irrigation system with biogas slurry in order to prevent the emitter clogging effectively and improve the reliability of the operation of the drip irrigation system with biogas slurry. The remaining biogas slurry from the actual biogas project was took as test samples. The total solids in biogas slurry was 0.6%, the chemical oxygen demand was 3 722.40 mg/L, the pH value was 8.42 and the turbidity value was 864.20 NTU. From the perspective of controlling the operation mode of the drip irrigation system rationally and meeting the requirement of crop growth, the ratio of water to biogas slurry, irrigation pressure and dripper flow rate were taken as the influencing factors. The ratio of water to biogas slurry included 3 levels of 1:1, 2:1 and 3:1. The irrigation pressure was 0.04, 0.12 and 0.20 MPa. The dipper flow rate was 4, 8 and 12 L/h. Average relative flow rate and first clogging time of the emitters were used as the response index in the experimental study. The experiment was designed by response surface methodology. The model was established by using regression analysis method. Response surface analysis was completed by the software of Design-Expert 8.0.6. The results showed that the ratio of water to biogas slurry, irrigation pressure and dripper flow rate had significant effects on the average relative flow rate and first clogging time of the emitters in drip irrigation system with biogas slurry, and the effects of these 3 factors on the average relative flow rate and first clogging time of the emitters was ordered by dripper flow rate > ratio of water to biogas slurry > irrigation pressure. Under the condition with large ratio of water to biogas slurry and dripper flow rate, the average relative flow rate was the largest and the firs clogging time was the longest. The optimal condition to obtain larger relative flow rate and longer first clogging time obtained by response surface methodology was as follows: the ratio of water to biogas slurry was 3:1, irrigation pressure was 0.14 MPa, dripper flow rate was 12 L/h. Under such an optimal condition, the measured average relative flow rate was 0.83 and the measured first clogging time was 55 h. The relative error between the measured value and the theoretical value of the model was smaller than 4%. It verified the reliability of model proposed in this study for predicting first clogging time of emitter in drip irrigation system with biogas slurry. The study would provide valuable information for the design of emitter in drip irrigation system with biogas slurry.