# Design and Parameters Optimization of a Provoke-Suction Type Harvester for Ground Jujube Fruit

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

^{−1}, respectively; as the forward speed, provoke teeth buried depth, and airflow velocity were 0.21 kg∙h

^{−1}, 74 mm, and 26.4 kg∙h

^{−1}, respectively. Furthermore, the verification results showed that the pickup rate, impurity rate, and working efficiency were 98.05%, 5.97%, and 1591.2 kg∙h

^{−1}, respectively, moreover, the relative errors were 1.32%, 6.04%, and 4.85%, respectively, indicating that the parameter optimization model can accurately predict the test results. The working efficiency of the PSH was significantly improved compared with the traditional aspirated-air type jujube fruit pickup machine. This research can provide a reference for the development of the jujube fruit pickup machine.

## 1. Introduction

^{−1}and the pickup rate is more than 94%. The mechanical type jujube fruit pickup machines have a high working efficiency, but they easily caused the jujube fruit damage during the picking up process, and it is difficult to effectively remove the impurities contained in jujube fruit.

^{−1}. Zhang et al. [13] developed a pneumatic pickup machine for low-density cultivation of jujube orchard by using the negative pressure airflow generated by the centrifugal fan to pick up jujube fruit and remove impurities through a vibrating screen. The results showed that the pickup rate and impurity rate were 96.41% and 1.54%, respectively. Zhang et al. [15] conducted an air suction type picker for ground jujube fruit by the same method as Zhang et al. [13]. The results showed that the working efficiency, impurity rate, and pickup rate were 220 kg∙h

^{−1}, 3.75%, and 92.20%, respectively, in the Jun jujube orchard, and 285 kg∙h

^{−1}, 4.28%, and 90.65% in the Grey jujube orchard. The aspirated-air type jujube fruit pickup machine can better pick up jujube fruit and remove impurities, but the suction inlet needs to be kept at a certain distance to the ground manually, and there are the disadvantages of fast airflow dissipation and low airflow utilization rate. Hence, the working efficiency usually is 100–500 kg∙h

^{−1}[16,17,18,19,20].

## 2. Materials and Methods

#### 2.1. Structure of the PSH

#### 2.2. Working Principle

#### 2.3. Operating Conditions and Main Technical Parameters

#### 2.4. Parameters Analysis and Device Design

#### 2.4.1. Critical Velocity

_{a}is the airflow force for jujube fruit, N; m

_{p}is the weight of jujube fruit, kg; g is the acceleration of gravity, m∙s

^{−2}.

_{a}is:

^{2}; ρ

_{f}is the air density, and the value is 1.205 kg∙m

^{−3}at 20 °C; u

_{g}is the airflow velocity, m∙s

^{−1}.

_{v}is the equivalent diameter of jujube fruit, m; η is air viscosity coefficient, m

^{2}∙s

^{−1}, and the value is 1.5 × 10

^{−5}m

^{2}∙s

^{−1}at 20 °C; ε is the porosity, %; m

_{n}is the mass sum of N jujube fruit, kg; ρ

_{f}is the density of jujube fruit, kg∙m

^{−3}.

^{3}. So, the value of C is 0.44. Then, substituting 0.44 into Equation (2) can be obtained Equation (4):

^{−3}kg) and the minimum projected area were (4.2 × 10

^{−4}m

^{2}) substituted into Equation (4). The critical velocity was obtained to be 24.88 m∙s

^{−1}.

#### 2.4.2. Design of the Pickup Device

- (1)
- Pickup Device Structure

- (2)
- Depth of the Provoking Teeth into Soil

- (3)
- Space between the Provoke Teeth

- (4)
- Angle between the Provoke Teeth and Ground

_{g∙p}is the airflow velocity in the pickup device, m∙s

^{−1}; A

_{c}is the cross-sectional area of the suction pipe, mm

^{2}; A

_{p}is the cross-sectional area in the pickup device, mm

^{2}.

_{a∙p}is the airflow force of jujube fruit in the pickup device, N; f is the friction between jujube fruit and teeth picking, N; θ is the angle between the provoke teeth and the ground, (°); G is the mass of a jujube fruit, kg; G

_{t}is the tangential force of the mass of a jujube fruit, kg; G

_{n}is the normal force of mass of a jujube fruit, kg; F

_{n}is the supporting force of the provoking teeth on the jujube fruit.

_{a∙p}, G

_{t}, and f are:

#### 2.4.3. Design of the Cleaning Device

_{in}is the velocity of jujube fruit entering the cleaning device, m∙s

^{−1}; t is time, s.

_{g.max}is the maximum airflow velocity, m∙s

^{−1}; s

_{p}is the length of the suction pipe that the design value is 1.6 m; m

_{p}is the mass of jujube fruit, kg; a

_{p}is the acceleration of jujube fruit, m∙s

^{−2}.

^{−2}and the corresponding maximum airflow velocity was 35.12 m∙s

^{−1}, by substituting the values into Equations (9) and (10).

#### 2.5. Test Materials

^{−1}. The moisture content of the jujube fruit was 33.09% (W.B) which was measured with a Sartoriusma 100 electronic rapid moisture meter (mass accuracy: 0.001 g, accuracy: 0.01%). The ground was relatively flat, and the soil type was sandy loam.

#### 2.6. Test Methods

_{1}, impurities rate Y

_{2}, and working efficiency Y

_{3}were determined as the evaluation indexes. The calculation methods are shown in Equations (11)–(13):

_{1}is the pickup rate, %; Y

_{2}is the impurities rate, %; Y

_{1}is the working efficiency, kg∙h

^{−1}; m

_{g.j}is the mass of jujube fruit that was not picked up by the PSH, kg; m

_{j.j}is the mass of picked up jujube fruit, kg; m

_{i.j}is the mass of the impurities, kg; t is pure working time, h.

^{−1}, 30–90 mm, and 25–35 m∙s

^{−1}, respectively.

## 3. Results and Discussion

#### 3.1. Pickup Rate

_{1}is extremely significant (p < 0.001) and the lack of fit is 0.4630, which is not significant (Table 4). Hence, the predicted values are highly correlated with the actual values, and the model can be utilized to analyze and predict the pickup rate.

^{−1}, and the trend increases obviously as the forward speed was greater than 0.25 m∙s

^{−1}. The pickup rate first increases rapidly and then tends to be flat with the increase of the provoke teeth buried depth. The pickup rate increases rapidly with the increase of airflow velocity, and the increase trend was further intensified as the airflow velocity was greater than 32 m∙s

^{−1}.

#### 3.2. Impurities Rate

_{2}is extremely significant (p < 0.001) and the lack of fit is 0.1913, which is not significant (Table 4). Hence, the predicted values are highly correlated with the actual values, and the model can be used to analyze and predict the impurities rate.

^{−1}and the provoking teeth buried depth was at its minimum value. The impurities rate increases linearly with the increase of the provoke teeth buried depth. The impurities rate increases gradually with the increase of airflow velocity, when the airflow velocity was less than 30 m∙s

^{−1}, and the trend increases rapidly when the airflow velocity was greater than 30 m∙s

^{−1}.

^{−1}. The provoking teeth will break the massive soil and then be sucked up, increasing the impurities rate, when the forward speed was greater than 0.20 m∙s

^{−1}. The deeper the provoking teeth buried depth, the more soil is disturbed by the provoking teeth, and then it will be sucked up together with the jujube fruit, so the impurities rate increases linearly with the provoking teeth buried depth. The reason the airflow velocity has the most significant effect on the impurities rate is that the greater airflow velocity will inhale more soil blocks. The aerodynamic equivalent diameter of the soil blocks was similar to the jujube fruit, which were difficult to remove.

#### 3.3. Working Efficiency

_{3}is extremely significant (p < 0.001) and the lack of fit is 0.1326, which is not significant (Table 4). Hence, the predicted values are highly correlated with the actual values, and the model can be utilized to analyze and predict the working efficiency.

^{−1}to 1300 kg∙h

^{−1}, as the forward speed increases. With the change of airflow velocity and provoke teeth buried depth, the variation range of the working efficiency only changes from 2000 kg∙h

^{−1}to 2150 kg∙h

^{−1}. The reason may be that the jujube fruit in the area to be collected were almost evenly distributed, so the working efficiency was only related to the forward speed.

#### 3.4. Parameter Optimization

^{−1}, 74 mm, and 26.4 m∙s

^{−1}, respectively. Additionally, the pickup rate, impurities rate, and working efficiency were 99.36%, 5.63%, and 1672.3 kg∙h

^{−1}, respectively.

^{−1}, respectively. Furthermore, the relative errors with the parameter optimization values were 1.32%, 6.04%, and 4.85%, respectively, indicating that the parameter optimization model can accurately predict the test results.

#### 3.5. Discussion

^{−1}[16,17,18,19,20]. In our paper, the working efficiency was 1591.2 kg∙h

^{−1}, which was improved more than three times. One reason was that after the provoke teeth gather the jujube fruit, the negative pressure airflow can act on the jujube fruit more intensively, reducing the dissipation of airflow. The other reason was that the friction drag force between the airflow and the jujube fruit was the main force [28], as the jujube fruit were suctioned by the negative pressure airflow. In this study, the pressure drag was the main force when the jujube fruit were suctioned along the provoke teeth. The pressure drag has more force on the jujube fruit than the friction drag at a higher Reynolds number.

## 4. Conclusions

^{−1}, respectively, as the forward speed, provoke teeth buried depth and airflow velocity were 0.21 m∙s

^{−1}, 74 mm, and 26.4 m∙s

^{−1}, respectively. Furthermore, the field verification tests were carried out according to the optimal parameter combination conditions, of which results showed that the pickup rate, impurity rate, and working efficiency were 98.05%, 5.97%, and 1591.2 kg∙h

^{−1}, respectively. The operation performance of the PSH meets the requirements of jujube fruit harvesting, and the picking efficiency was significantly improved compared with the traditional aspirated-air type jujube fruit pickup machine. This research can provide a new mechanized operation method for picking up jujube fruit and a reference for the development of a jujube fruit harvester.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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**Figure 1.**Structure of the provoke-suction type harvester for ground jujube fruit (PSH). 1. Control system 2. Suction pipe 3. Cleaning device 4. Diesel engine 5. Rotary screen 6. Centrifugal fan 7. Oil hydraulic pump 8. Provoke teeth 9. Pickup device 10. Caterpillar chassis 11. Basket 12. Closed-air aspirator of discharge jujube fruit 13. Closed-air aspirator of discharge impurities materials 14. Rack.

**Figure 2.**Structure diagram of the pickup device. 1. Side baffle 2. Provoking teeth 3. Upper baffle 4. Negative pressure airflow interface 5. Angle adjusting rod 6. Underside baffle 7. Depth limiting sliding plate.

**Figure 6.**Structure diagram of the cleaning device. 1. Inlet 2. Cleaning tank 3. Baffle 4. Drum screen 5. Strip brush 6. Connecting port for centrifugal fan 7. Closed-air aspirator for discharge jujube fruit 8. Closed-air aspirator for discharge impurities.

**Figure 7.**Interaction factors effect on the pickup rate: (

**a**) interaction factors between the forward speed and the provoke teeth buried depth, (

**b**) interaction factors between the forward speed and the airflow velocity, and (

**c**) interaction factors between the provoke teeth buried depth and the airflow velocity.

**Figure 8.**Interaction factors’ effect on the impurities rate: (

**a**) interaction factors between the forward speed and the provoke teeth buried depth, (

**b**) interaction factors between the forward speed and the airflow velocity, and (

**c**) interaction factors between the provoke teeth buried depth and the airflow velocity.

**Figure 9.**Interaction factors’ effect on the working efficiency: (

**a**) interaction factors between the forward speed and the provoke teeth buried depth, (

**b**) interaction factors between the forward speed and the airflow velocity, and (

**c**) interaction factors between the provoke teeth buried depth and the airflow velocity.

**Figure 10.**Field verification test process and work performance of the provoke-suction type harvester for ground jujube fruit (PSH). The Chinese in left image means “developed by the College of Mechanical and Electrical Engineering, Shihezi University”.

**Table 1.**Main technical parameters of the provoke-suction type harvester for ground jujube fruit (PSH).

Items | Values/Type |
---|---|

Rated horsepower/kW | 36.8 |

Unity machine dimensions (Length × width × height)/(mm × mm × mm) | 2840 × 1320 × 2130 |

Working width/m | 1.0 |

Drive type | Hydraulic drive |

Centrifugal fan model | Y5-47 |

Forward speed/(km∙h^{−1}) | 0–1.5 |

Levels | Factors | ||
---|---|---|---|

Forward Speed X_{1}/m∙s^{−1} | Provoke Teeth Buried Depth X_{2}/mm | Airflow Velocity X_{3}/m∙s^{−1} | |

−1 | 0.25 | 30 | 25 |

0 | 0.30 | 60 | 30 |

1 | 0.35 | 90 | 35 |

No. | Factors | Indexes | |||
---|---|---|---|---|---|

Forward Speed X_{1}/m∙s^{−1} | Provoke Teeth Buried Depth X_{2}/mm | Airflow Velocity X_{3}/m∙s^{−1} | Pickup Rate Y_{1}/% | Impurities Rate Y_{2}/% | |

1 | 0.15 | 30 | 30 | 97.15 | 5.7 |

2 | 0.35 | 30 | 30 | 96.34 | 7.4 |

3 | 0.15 | 90 | 30 | 99.020 | 8.2 |

4 | 0.35 | 90 | 30 | 98.59 | 9.5 |

5 | 0.15 | 60 | 25 | 98.76 | 5.6 |

6 | 0.35 | 60 | 25 | 97.77 | 6.5 |

7 | 0.15 | 60 | 35 | 99.97 | 12.4 |

8 | 0.35 | 60 | 35 | 99.92 | 14.8 |

9 | 0.25 | 30 | 25 | 95.76 | 4.5 |

10 | 0.25 | 90 | 25 | 99.37 | 6.6 |

11 | 0.25 | 30 | 35 | 98.52 | 11.1 |

12 | 0.25 | 90 | 35 | 99.86 | 15.2 |

13 | 0.25 | 60 | 30 | 99.34 | 6.4 |

14 | 0.25 | 60 | 30 | 99.41 | 6.5 |

15 | 0.25 | 60 | 30 | 98.97 | 6.9 |

16 | 0.25 | 60 | 30 | 99.33 | 6.7 |

17 | 0.25 | 60 | 30 | 99.26 | 6.8 |

Source of Variance | Pickup Rate | Impurities Rate | Working Efficiency | ||||||
---|---|---|---|---|---|---|---|---|---|

Sum of Squares | Means Square | p Value | Sum of Squares | Means Square | p Value | Sum of Squares | Means Square | p Value | |

Model | 24.00 | 2.67 | <0.0001 ** | 164.50 | 18.28 | <0.0001 | 4.65 × 10^{6} | 5.17 × 10^{5} | <0.0001 ** |

X_{1} | 0.65 | 0.65 | <0.0023 ** | 4.96 | 4.96 | 0.0001 ** | 4.60 × 10^{6} | 4.60 × 10^{6} | <0.0001 ** |

X_{2} | 10.28 | 10.28 | <0.0001 ** | 14.58 | 14.58 | <0.0001 ** | 2876.61 | 2876.61 | 0.3590 |

X_{3} | 5.46 | 5.46 | <0.0001 ** | 114.76 | 114.76 | <0.0001 ** | 24.50 | 24.50 | 0.9304 |

X_{1}X_{2} | 0.036 | 0.036 | 0.3095 | 0.040 | 0.040 | 0.4805 | 228.01 | 228.01 | 0.7903 |

X_{1}X_{3} | 0.22 | 0.22 | 0.0302 * | 0.56 | 0.56 | 0.0268 * | 4013.22 | 4013.22 | 0.2843 |

X_{2}X_{3} | 1.29 | 1.29 | 0.0003 ** | 1.00 | 1.00 | 0.0074 ** | 8807.82 | 8807.82 | 0.1296 |

X_{1}^{2} | 0.61 | 0.61 | 0.0028 ** | 2.42 | 2.42 | 0.0007 ** | 30762.00 | 30762.00 | 0.0149 * |

X_{2}^{2} | 5.16 | 5.16 | 0.0026 ** | 0.34 | 0.34 | 0.0677 | 1163.75 | 1163.75 | 0.5522 |

X_{3}^{2} | 0.21 | 0.21 | 0.0336 * | 24.40 | 24.40 | 0.0001 ** | 8621.32 | 8621.32 | 0.1331 |

Residual | 0.21 | 0.030 | 0.50 | 0.072 | 20902.54 | 2986.08 | |||

Lack of fit | 0.093 | 0.031 | 0.4630 | 0.33 | 0.11 | 0.1913 | 15047.36 | 5015.79 | 0.1326 |

Pure error | 0.12 | 0.029 | 0.17 | 0.043 | 5855.18 | 1463.79 | |||

Total | 24.21 | 165.00 | 4.67 × 10^{6} |

**Table 5.**Comparison of the optimal results and the verification test results for evaluation indexes.

Evaluation Indexes | Optimal Results | Verification Test Results | Relative Errors |
---|---|---|---|

Pickup rate | 99.36% | 98.05% | 1.32% |

Impurities rate | 5.63% | 5.97% | 6.04% |

Working efficiency | 1672.3 kg∙h^{−1} | 1591.2 kg∙h^{−1} | 4.85% |

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## Share and Cite

**MDPI and ACS Style**

Shi, G.; Li, J.; Kan, Z.; Ding, L.; Ding, H.; Zhou, L.; Wang, L.
Design and Parameters Optimization of a Provoke-Suction Type Harvester for Ground Jujube Fruit. *Agriculture* **2022**, *12*, 409.
https://doi.org/10.3390/agriculture12030409

**AMA Style**

Shi G, Li J, Kan Z, Ding L, Ding H, Zhou L, Wang L.
Design and Parameters Optimization of a Provoke-Suction Type Harvester for Ground Jujube Fruit. *Agriculture*. 2022; 12(3):409.
https://doi.org/10.3390/agriculture12030409

**Chicago/Turabian Style**

Shi, Gaokun, Jingbin Li, Za Kan, Longpeng Ding, Huizhe Ding, Lun Zhou, and Lihong Wang.
2022. "Design and Parameters Optimization of a Provoke-Suction Type Harvester for Ground Jujube Fruit" *Agriculture* 12, no. 3: 409.
https://doi.org/10.3390/agriculture12030409