油菜脱粒过程中茎秆碰撞破碎的试验研究

Experimental study on impact crushing of rapeseed stalks during threshing of oilseed rape

油菜脱粒过程中茎秆过度破碎是导致夹带损失和脱粒功耗升高的主要原因。为明确油菜茎秆被脱粒钉齿碰撞导致破碎的机理,该研究以收获期油菜茎秆为研究对象,在自制的碰撞试验台上进行脱粒钉齿与油菜茎秆的碰撞破碎试验。在进行油菜茎秆与脱粒钉齿撞后轨迹分析的基础上,利用感压胶片对脱粒钉齿与油菜茎秆的碰撞力进行了测量,并以油菜茎秆破碎率为指标,以油菜茎秆长度、喂入次数、滚筒转速、齿型等为因素分别进行了单因素试验和正交试验。结果表明:单个钉齿与油菜茎秆的碰撞过程为高速瞬时多点碰撞,碰撞过程89%为多次碰撞,发生1次碰撞的仅占11%,碰撞次数与碰撞点在钉齿上的位置有关;瞬时多次碰撞过程中碰撞力随碰撞次数呈减小趋势,试验条件下单次碰撞力平均值为13.25 N,单次碰撞的油菜茎秆不易破碎;单因素试验表明油菜茎秆破碎率与茎秆长度、喂入次数、滚筒转速正相关;刀面、柱面和平面3种钉齿中刀面钉齿对茎秆破碎率影响最大,平面钉齿对茎秆破碎率影响最小,试验条件下将油菜茎秆重复8次喂入碰撞试验台后油菜主茎秆上、中、下各部分破碎率分别为84.4%、91.1%、97.8%,油菜侧枝破碎率为42.2%,主茎秆破碎率远远大于侧枝;正交试验表明,在所选参数范围内,影响茎秆破碎率大小的因素依次为茎秆长度、滚筒转速、齿型、喂入次数,且茎秆长度100 mm、滚筒转速500 r/min、喂入次数为2次、齿型为平面钉齿时油菜茎秆破碎率最低。研究结果可为油菜脱粒装置的优化设计提供依据。

Excessive breakage of stalk in the process of rape threshing has become the main reason for the entrainment loss and the increase of the whole power consumption.Taking the harvest rape stalks as the research object,this study aims to investigate the collision and crushing behavior between threshing nail tooth and rape stem,further to clarify the breakage mechanism of rape stems caused by the collision of threshing spike tooth on a self-made collision test-bed.A prescale film was used to measure the impact force between the rape stalks and spike tooth,according to the force and trajectory.A single factor and an orthogonal experiments were carried out,where the breakage rate of rape stalk as the index,and the length of rape stalk,feeding times,rotational speed of cylinder,and type of spike tooth as factors.An attempt was made to explore the collision form and collision force between the threshing nail tooth and the stem of rapeseed,thereby to figure out the main factors affecting the breakage rate of stalk.The results were as follows:The collision process between single spike tooth and rape stalk was a multiple high-speed instantaneous collision,where 89%of the collisions were multiple collisions,and only 11%had one collision,particularly that the collision times were strongly related to the position of impact point on the spike tooth.In the process of instantaneous multiple collisions,the collision force decreased with the number of collisions.In the case of test conditions,the single impact force was 13.25 N,which was less than the yield limit of radial compression in a rape stalk.The stalk collided only once cannot be broken.The breakage rate of stalk was positively related to the stalk length,feeding times,and rotational speed of cylinder.In three kinds of nail tooth,cutter surface,cylinder,and plane,there was the greatest influence of nail teeth formed on the cutter face on the stem breakage rate,whereas,there was the least influence of plane nail teeth on the stem breakage rate.In the experimental conditions,the crushing rates of the upper,middle and lower parts for the main stem were 84.4%,91.1%,and 97.8%,respectively,after feeding the rape stem into the collision test-bed for 8 times,and the fragmentation rate for the lateral branches of the rape was 42.2%,indicating that the broken rate of main stem was much higher than that of lateral branch.The orthogonal test showed that,there was the greatest effect of the length of rape stalk on the breakage rate,followed by the rotational speed of cylinder,and the type of spike tooth,whereas,the effect of feeding times was the smallest within the scope of the selected parameters,where the stalk length was 100 mm,the roller speed was 500 r/min,the feeding times were 2 times,and the tooth shape was flat nail teeth,as well as the breakage rate of rape stalk was the lowest.The finding can provide a sound basis for the optimal design of rape threshing device.