There is a close dynamic correlation between the feed rate and threshing loss rate in rice and wheat threshers, and its pattern is influenced by the structure of the threshing device, crop characteristics, and operating parameters. In the combined rice and wheat harvesting process, the feed rate, as a core operating parameter, directly determines the crop quality entering the threshing device per unit time, while the threshing loss rate reflects the proportion of unthreshed grains, entrained losses, and broken grains in the total processed volume. The relationship between the two needs to be comprehensively analyzed from three aspects: the threshing principle, crop condition, and device adaptability.
When the feed rate is at a low level, the processing capacity of the threshing device is relatively sufficient. The crop can fully withstand the impact and rubbing of the spikes or slats during the threshing interval, and the separation process of grains from the cob is relatively thorough. At this time, the threshing loss rate is mainly affected by the device structural parameters, such as the size of the threshing interval, the drum speed, and the design of the concave sieve openings. Because the crop layer is thin, the resistance of grains passing through the stalk layer into the concave sieve is small, and the unthreshed loss and entrained loss are both at a low level. However, too low a feed rate will lead to insufficient device load, increased unit energy consumption, and decreased economic efficiency.
As the feed rate gradually increases, the processing load on the threshing device intensifies, and the crop layer thickness increases. At this point, the threshing process exhibits a dual effect: on the one hand, the thicker crop layer provides more buffer space for the grains, reducing breakage caused by direct impact from the spikes; on the other hand, an excessively thick crop layer may cause localized blockages, resulting in some grains not being fully threshed and thus incomplete loss. Simultaneously, increased stalk density hinders grains from passing through the concave sieve openings, leading to a higher entrainment loss rate. Therefore, the relationship between feed rate and threshing loss rate is non-linear at this stage, requiring optimization of the device's structural parameters to balance the threshing rate and breakage rate.
When the feed rate exceeds the design capacity of the threshing device, the system enters an overload state. At this time, the crop layer thickness increases dramatically, severely compressing the threshing gaps, preventing the spikes or stalks from effectively gripping the crop, resulting in a large number of grains failing to detach from the ear cob. Simultaneously, the excessively thick stalk layer creates a "cushion effect," making it difficult for threshed grains to pass through the concave sieve, instead causing them to be entrained by the stalks and discharged from the machine, significantly increasing the entrainment loss rate. Furthermore, under overload conditions, the device vibrates more intensely, and component wear accelerates, further deteriorating threshing quality. During this stage, the threshing loss rate increases rapidly with increasing feed rate, and the device reliability decreases.
Crop characteristics have a significant moderating effect on the relationship between feed rate and threshing loss rate. Rice stalks are thinner and more resilient, making them more prone to forming a dense layer under the same feed rate, leading to a faster increase in entrainment loss. Wheat stalks are thicker and more brittle, making them more prone to breakage under overload, increasing cleaning difficulty. In addition, crop moisture content is also a key factor; high-moisture crops are more likely to adhere to the device surface during threshing, forming a "sticky" phenomenon, exacerbating incomplete threshing losses. Therefore, the feed rate threshold needs to be adjusted for different crops to control the threshing loss rate within a reasonable range.
The structural parameters of the threshing device have a decisive influence on the adaptability of the feed rate. The diameter, rotational speed, and shape of the threshing teeth directly affect processing capacity: larger diameter drums can accommodate thicker crop layers but require higher rotational speeds to maintain threshing intensity; ribbed drums achieve threshing through a rubbing action and are more adaptable to fluctuations in feed rate; spiked-tooth drums rely on impact force and are prone to increased breakage rates under overload. The size and shape of the concave sieve apertures affect grain separation efficiency; elongated aperture sieves facilitate stalk passage more effectively than round aperture sieves, reducing entrainment losses.
Modern rice and wheat threshers optimize feed rate management through intelligent control technology. Sensors monitor the threshing drum load, concave inlet pressure, and grain flow rate in the cleaning chamber in real time, and dynamically adjust the feed speed, drum rotational speed, and cleaning fan airflow using an algorithm model. For example, when the threshing loss rate exceeds a threshold, the system automatically reduces the feed speed or increases the drum rotational speed to ensure stable threshing quality. This adaptive control technology significantly expands the device's adaptability to different feed rates, keeping the threshing loss rate at a low level.
The relationship between feed rate and threshing loss rate in rice and wheat threshers exhibits a pattern of "high efficiency under low load, optimization under medium load, and deterioration under high load." In actual operation, the optimal feed rate range needs to be determined through experiments based on crop characteristics, equipment parameters, and environmental conditions, and combined with intelligent control technology to achieve a balance between threshing efficiency and quality. This pattern provides a theoretical basis for the design optimization and operational parameter adjustment of threshing devices, and is of great significance for improving the overall performance of combine harvesters.
