Authors

Abstract

During the grain drying process, in order to adjust the temperature, it is necessary to match the proportion of hot and cold air. This is the problem that the two components in the mixed gas cannot fully mix with each other in a short period of time, resulting in the problem that it takes a long time for the gas flow temperature to reach a stable value. Based on the process and technical requirements of the dryer, a self-priming hot air temperature changing device suitable for the dryer was designed. The two gas components used to improve the variable temperature ratio of the dryer are fully mixed with each other in a short time and a short distance, thereby reducing the loss caused by the food not reaching safe moisture. Based on Bernoulli's principle and the basic theory of airflow mixing in fluid dynamics, a mathematical model of airflow mixing in the constriction section of the main pipeline was established. Fluent was used to numerically simulate the distribution of uniform mixing distance and temperature field in the necking section. The results show that the mixing uniformity in the necking section reaches 75%-80%, which effectively improves the mixing efficiency. A self-priming hot air temperature change device test bench developed independently was used, and the quadratic orthogonal rotation combined test method was used for parameter optimization. Design-Expert.V8.0.6.1 was used for analysis and testing, and the regression equation and response surface were obtained to analyze the effects. Interaction between factors to determine the best combination of optimization parameters: when the number of air inlet pipes is 3.16, the incision axial angle is 27.6°, the temperature difference is 43.5°C, and the pipe diameter is 23.8mm, the post-mixing temperature is 50.93°C, and the mixing distance is uniform is 39.33mm. The test results are consistent with the optimization results. The self-priming hot air temperature changing device of the dryer has certain practical application value.

Abstract in Chinese

在谷物干燥过程中，为调节温度，需要根据冷热空气的比例配比。为混合气体中的两种组分在短时间内无法充分相互混合，导致气流温度达到稳定值需要较长时间的问题。基于干燥机的工艺与技术要求，设计了一种适用于干燥机自吸式热风变温装置。用于提高干燥机变温配比的两种气体组分短时间、短距离的充分相互混合，进而减少粮食未达到安全水分造成损失。基于流体动力学中伯努利原理和气流混和的基本理论，建立了在主管道缩颈段的气流混配的数学模型。运用Fluent对缩颈段内混合均匀距离和温度场的分布情况进行了数值模拟。结果表明：在缩颈段混合均匀度达到75%-80%，有效的提高了混合效率。采用自主研制的自吸式热风变温装置试验台，应用二次正交旋转组合试验方法进行参数优化，运用Design-Expert.V8.0.6.1进行分析检验，得到回归方程和响应曲面，分析各影响因素之间的交互作用，以确定优化参数最佳组合：当进气管数量为3.16、切口轴向角27.6°、温差43.5°C、导管直径23.8mm时混后温度为50.93°C，混合均匀距离为39.33mm，试验结果与优化结果相符合，干燥机自吸式热风变温装置具有一定的实际应用价值。