Design and experiment of key components for a pneumatic recovery system in the low-loss harvesting header of rapeseed

doi:10.3969/j.issn.1004-1524.20250126

Acta Agriculturae Zhejiangensis ›› 2026, Vol. 38 ›› Issue (1): 170-183.DOI: 10.3969/j.issn.1004-1524.20250126

• Biosystems Engineering • Previous Articles Next Articles

Design and experiment of key components for a pneumatic recovery system in the low-loss harvesting header of rapeseed

TONG Xuequan¹(), JIN Yuguo¹, SONG Xi¹, WU Mingliang¹^,², JIANG Xiaohu¹^,², LUO Haifeng¹^,²^,^*()

1. College of Engineering, Hunan Agricultural University, Changsha 410128, China
2. Hunan Key Laboratory of Intelligent Agricultural Machinery and Equipment, Changsha 410128, China

Received:2025-02-24 Online:2026-01-25 Published:2026-02-11

Abstract

Abstract:

To address high header loss rate in rapeseed combine harvesting, a pneumatic recovery device was designed using a “bidirectional air intake-centralized middle air supply” method. The device mainly comprises fan, transmission system, air supply unit, header, and splash guards. A stable air curtain generated by the air supply unit directionally recovers the shattered pods and dropped seeds on the header via airflow, enabling low-loss harvesting. The internal flow field of the air ducts was simulated and optimized with Fluent. Using the inner diameters of the main duct left/right inlets, the airflow reducer end, and the airflow branch duct outlet as the test factors, and the outlet wind velocity non-uniformity as the evaluation index, a ternary quadratic regression orthogonal simulation test was conducted. Results showed that the order of primary-to-secondary factors affecting outlet wind velocity non-uniformity was: inner diameter of airflow branch duct outlet, inner diameter of airflow reducer end, and inner diameter of main duct left/right inlet. The optimal duct parameters were: main duct left/right inlets inner diameter 63 mm, reducer end inner diameter 56 mm, and branch duct outlet inner diameter 14 mm. A bench test with fan speed, horizontal distance, and inclination angle as factors indicated optimal seed recovery at 3 000 r·min^-1, 350.5 mm, and 76.8°. A prototype low-loss rapeseed combine harvester was developed by adding a mechanical transmission driven by the existing threshing power to operate this pneumatic recovery device. The device achieved an outlet wind velocity non-uniformity of 1.19%, indicating good airflow stability. Field tests showed a header loss rate of 2.75%, which was 1.3 percentage points lower than that without the pneumatic recovery device, achieving effective low-loss combine harvesting.

Key words: rapeseed, combine harvesting, header loss reduction, air-assisted recovery, computational fluid dynamics (CFD) simulation

CLC Number:

S225

TONG Xuequan, JIN Yuguo, SONG Xi, WU Mingliang, JIANG Xiaohu, LUO Haifeng. Design and experiment of key components for a pneumatic recovery system in the low-loss harvesting header of rapeseed[J]. Acta Agriculturae Zhejiangensis, 2026, 38(1): 170-183.

Figures/Tables 24

Fig.1 Structural schematic diagram of the header pneumatic recovery device a, Prototype of low-loss rapeseed combining harvester with air-blown header; b, Schematic diagram of low loss recovery air supply unit for cutting table. 1, Cutting table; 2, Air supply unit; 3, Splash guard; 4, Blower; 5, Transmission system; 6, Duckbill nozzle; 7, Airflow branch duct; 8, Connection piece; 9, Airflow main duct; 10, Airflow hose; 11, Airflow diverter; 12, Blower rotor shaft; 13, Threshing input shaft.

Fig.2 Schematic diagram of the integration of the blade guard and the airflow branch duct 1, Cutter; 2, Blade guard; 3, Connecting piece; 4, Airflow branch duct. D1, Inner diameter of the airflow branch duct; L1, Spacing between the cutter guards; L2, Vertical distance between the two ends of the cutter guard.

Fig.3 Diagram of grain motion L, Horizontal distance between the outlet of branch airflow duct and the installation point of the horizontal cutter (abbreviated as horizontal distance); θ, Angle of inclination between the outlet and the horizontal direction (abbreviated as horizontal inclination angle); vx, Horizontal velocity of the grain at point O; vy, Vertical velocity of the grain at point O.

Table 1 Parameters of the three airflow duct models

参数 Parameters	结构形态 Configuration	进风口风速/(m·s^-1) Wind speed of inlet/(m·s^-1)	气流主管内径/mm Inner diameter of the main airflow duct/mm	气流支管内径/mm Inner diameter of the branch airflow duct/mm
模型A Model A	单侧进风Single-side air intake	60	60	18
模型B Model B	双侧进风Double-side air intake	30	60	18
模型C Model C	双中通进风Dual-central air intake	30	60	18

Fig.4 Schematic diagram of air intake in the duct model a, Modeling of single-side air intake; b, Modeling of double-side air intake; c, Dual-central air intake.

Fig.5 The internal flow field of the airflow duct

Fig.6 Schematic diagram of wind speed variation at the outlet of each branch duct in model B a, Wind speed at the outlet of branch ducts for model B; B, Each branch duct number of Model B. D2, Inner diameter of main duct.The same as below.

Fig.7 Schematic diagram of the reducer structure D3, Inner diameter at the end of the reducer.

Fig.8 Wind speed non-uniformity curve at outlet of the reducer with different end inner diameters

Fig.9 Wind speed non-uniformity curve at outlet of the branch duct with different inner diameters

Table 2 Factor code of factorial experiments mm

编码 Code	因素Factors
编码 Code	A	B	C
-1	50	50	14
0	60	55	18
1	70	60	22

Table 3 Test protocol and results

试验组 Test group	A/mm	B/mm	C/mm	W/%
1	-1	-1	0	2.24
2	1	-1	0	1.46
3	-1	1	0	2.01
4	1	1	0	2.76
5	-1	0	-1	1.35
6	-1	0	-1	1.02
7	-1	0	1	3.46
8	1	0	1	3.04
9	0	-1	-1	1.03
10	0	1	-1	1.49
11	0	-1	1	3.19
12	0	1	1	3.16
13	0	0	0	1.18
14	0	0	0	1.18

Fig.10 Response surface of interaction effects on wind speed non-uniformity at outlet A, Inner diameter of left and right air inlet; B, Inner diameter at the end of the reducer; C, Inner diameter of the branch duct outlet.

Fig.11 Schematic diagram of the duckbill nozzle

Fig.12 Contour of wind speed at the outlet of the duct

Fig.13 Bench test 1, Airflow hose; 2, Airflow main duct; 3, Splash guard; 4, Collection platform; 5, Long slot; 6, Duckbill nozzle; 7, Airflow branch duct; 8, Fan. H, Vertical distance from long slot to collection platform.

Table 4 Factor code of bench test

编码 Code	因素Factors
编码 Code	f/Hz	L/mm	θ/(°)
-1	30	300	60
0	40	350	70
1	50	400	80

Table 5 Experimental design and results

试验组 Test group	f/Hz	L/mm	θ/(°)	ω/%
1	-1	-1	0	13.2
2	1	-1	0	64.6
3	-1	1	0	12.8
4	1	1	0	64.8
5	-1	0	-1	14.4
6	1	0	-1	58.7
7	-1	0	1	13.8
8	1	0	1	65.4
9	0	-1	-1	38.6
10	0	1	-1	41.3
11	0	-1	1	42.2
12	0	-1	1	42.3
13	0	0	0	44.1
14	0	0	0	45.7
15	0	0	0	44.4
16	0	0	0	44.9
17	0	0	0	45.8

Table 6 Analysis of variance for the regression equation

方差来源 Source of variance	平方和 Square sum	自由度 Degree of freedom	均方 Mean square	F	p
模型Model	5 127.27	9	569.70	371.12	<0.000 1
f	4 965.06	1	4 965.06	3 234.42	<0.000 1
L	0.845 0	1	0.845 0	0.550 5	0.442 3
θ	14.31	1	14.31	9.32	0.018 5
fL	0.090 0	1	0.090 0	0.058 6	0.815 6
fθ	13.32	1	13.32	8.68	0.021 5
Lθ	1.69	1	1.69	1.10	0.326 9
f²	88.23	1	88.23	57.47	0.000 1
L²	10.15	1	10.15	6.61	0.036 9
θ²	22.81	1	22.81	14.86	0.006 3
残差Residual	10.75	7	1.54
失拟项Lack of fit	8.44	3	2.81	4.87	0.080 0
总和Total	5 138.02	16

Fig.14 Response surface of the effect of interaction factors on the recovery rate f, Frequency; L, Horizontal distance; θ, Horizontal inclination.

Fig.15 Fan drive system installation diagram

Fig.16 Schematic diagram of fan drive system 1, Harvester cross-flow fan shaft; 2, Cross-flow fan pulley; 3, Threshing compound pulley (Ⅰ); 4, Threshing compound pulley (Ⅱ); 5, Fan pulley; 6, Fan shaft; 7, Fan; 8, Threshing input shaft; 9, Commutator; 10, Threshing roller.

Fig.17 Field test

Table 7 Results of field experiments

试验序号 Test number	前进速度/(m·s^-1) Forward speed/(m·s^-1)	接样槽回收总质量/g Total mass collected in sample trough/g	割台损失质量/(g·m^-2) Header loss mass/(g·m^-2)	割台损失率/% Header loss rate/%
1	1.12	2.88	4.80	2.41
2	1.04	3.72	6.20	3.11
3	1.08	3.27	5.45	2.73
平均值Average value	1.08	3.29	5.48	2.75

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Design and experiment of key components for a pneumatic recovery system in the low-loss harvesting header of rapeseed

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