redesign and evaluation of a chickpea harvesteragri.uok.ac.ir/golpira/papers/redesign 2015.pdf ·...

Redesign and Evaluation of a Chickpea Harvester

H. Golpira*

Department of Biosystems Engineering, University of Kurdistan, Sanandaj, Iran

Received: November 2nd, 2014; Revised: November 19th, 2014; Accepted: January 28th, 2015Purpose: Slow manual harvesting of rain-fed chickpeas cultivated in fallow fields in developing countries have encouraged the design of a mechanical harvester. Methods: A tractor-pulled harvester was built, in which a modified stripper header detached pods from an anchored plant and a chain conveyor transferred material. The stripper harvester was redesigned to use: 1) the maneuverability of tractor-mounted frames, 2) the adaptability of floating headers, and 3) the flexibility of pneumatic conveyors. Results: A mobile vacuum conveyor, which was an innovator open system, was designed for the dilute phase transferring mode for both grain and material other than grain. A centrifugal fan transferred harvested material to a cyclone separator that settled harvested material in a grain tank 1 m high. The machine at the spot work rate of 0.42 ha·h-1 harvested chickpea pods equal to the output of 16.6 farm laborers. Conclusion: The low cost and reasonable projected purchase price are the advantages of the concept. Additionally, the shattering loss reduction confirms the feasibility of the prototype chickpea harvester for commercialization.Keywords: Centrifugal fan, Chickpea harvester, Cyclone separator, Dilute phase, Pneumatic conveyor

Original Article Journal of Biosystems EngineeringJ. of Biosystems Eng. 40(2):102-109. (2015. 6)http://dx.doi.org/10.5307/JBE.2015.40.2.102

eISSN : 2234-1862 pISSN : 1738-1266

*Corresponding author: H. Golpira Tel: +98-871-6620552; Fax: +98-871-6620553 E-mail: [email protected]

Copyright ⓒ 2015 by The Korean Society for Agricultural MachineryThis is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0)

which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

IntroductionHarvesting of chickpeas (Cicer arietinum L.) is currently carried out manually by laborers in a tedious manner and with a low level of efficiency in fallow fields in developing countries. Low yield, irregular and small fields, uneven ripening, low plant stature, and high probability of shattering losses are the challenges of harvesting rain-fed chickpeas. Both manual and mechanized harvesting methodologies were reported for chickpeas (Diekmann, 2011; Gaur, 2011); however, rain-fed chickpea harvests sustained much greater losses than those of irrigated chickpeas. Some modifications have been applied to conventional Combine harvester headers to reduce gathering losses (Haffar et al., 1991; Siemens, 2006; Yavari, 2007); however, they have the disadvantage of causing excessive grain losses, often over 50%. Bansal and Sakr (1992) developed a vertical conveyor

reaper for chickpea harvesting, where machine blockage with weeds was the main problem.Behroozi-Lar and Huang (2002) developed a Shelbourne Reynolds stripper header for chickpea harvesting; however, the inefficiency of this header for low harvest yields produced extra losses. Stripper headers have a rotating rotor and teeth to detach the pods from the anchored plant and deliver the material (Tado et al., 2003).Golpira et al. (2013) modified the stripping methodology to develop a new concept for chickpea harvesting. Special features include a stripper platform combined with a conventional reel configuration. A tractor-pulled stripper harvester was designed in which passive fingers with V-shaped slots remove chickpea pods from an anchored plant, a batted reel sweeps the pods across the platform, and a chain conveyor handles the harvested material. Performance factors, including field capacity, harvesting losses, purchase price, and operating costs were evaluated in a field trial. The large weight of the chain conveyors, low maneuverability of tractor-pulled frames, and high

H. Golpira. Redesign and Evaluation of a Chickpea HarvesterJournal of Biosystems Engineering • Vol. 40, No. 2, 2015 • www.jbeng.org

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Table 1. Physical, mechanical and aerodynamic properties of chickpeas seed surveyed for designing pneumatic conveyors

Properties values Related references

Dilute phase velocity (m s-1) >20 Mills, 2004

Drag coefficient 0.44 Marcus et al., 1990; Raheman & Jindal, 2002

*Reynolds Number >6800 Gorial & O'callaghan, 1990; Gürsoy & Güzel, 2010

*Terminal velocity (m s-1) 13-18Gorial & O'callaghan, 1990; Rabani et al., 2002; Tabatabaeefar et al., 2003;

Kilikan & Güner, 2010; Gürsoy & Güzel, 2010; Razavi et al., 2010

Drag force (N) 7.93×10-3 Mohtasebi et al., 2002

Sphericity (%) 86Gorial & O'callaghan, 1990; Kaur et al., 2005;

Kilikan & Güner, 2010; Shahbazi, 2011

Length (mm) 9.34

Behrozi-Lar & Mohtasebi, 2003; Konak et al., 2002 Width (mm) 7.72

Thickness (mm) 7.75

Geometric mean diameter (mm) 8.5 Gorial & O'callaghan, 1990

Mass (mg) 370Gorial & O'callaghan, 1990; Gürsoy & Güzel, 2010

True density (kg m-3) 1404

Bulk density (g ml-1) 0.64

Kaur et al., 2005Volume (ml) 19.5

Hardness (kg) 3.3

Impact velocity 10 Khazaei et al., 2003; Shahbazi, 2010

Coefficient of friction on galvanized surface 0.28

Tabatabaeefar et al., 2003Coefficient of friction on fiberglass surface 0.33

Arithmetic mean diameter (mm) 7.8

* The data was measured or calculated in this research.This data are preliminary and the accurate data needs additional research on the subject.

losses of the stripper headers caused low work quality. The main aim of this article is to explain the redesign and modification of the chickpea stripper harvester intro-duced by Golpira et al. (2013). The flexibility of pneumatic conveyors, maneuverability of tractor-mounted frames, and adaptability of floating headers were applied to the earlier harvester, and the performance of the prototype harvester was evaluated in the field. Further, both the design of the pneumatic conveyor for chickpeas and the technical information that is useful for the design are discussed. Materials and Methods

Design fundamentals For dilute phase transference of chickpea grains and/or materials other than grain (MOG), the minimum gas velocity must exceed the saltation velocity in the horizontal parts of the system, and the choking velocity in the vertical

part. A product velocity of 10–25 m·s-1 and a system pressure of -0.5/+2 are needed for a dilute phase conveying system (Wohlbier, 2000; Mills, 2004). As listed in Table 1, terminal velocity, Reynolds number, sphericity, grain dimensions, densities, mass, volume, hardness, impact velocity, coefficients of friction, and drag force are some of the important parameters for designing a pneumatic conveyor for chickpea seeds (Raheman & Jindal, 2002; Mohtasebi et al., 2002; Behrozi-Lar & Mohtasebi, 2003; Konak et al., 2002; Khazaei et al., 2003; Khazaei et al., 2004; Kaur et al., 2005; Shahbazi, 2010; Shahbazi, 2011).Drag coefficient values of 0.81 (Gorial & O'callaghan, 1990) and 0.764 (Kilikan & Gner, 2010) were reported for chickpea seeds. However, for the air velocities and turbulent flow commonly encountered in pneumatic conveying, drag coefficient attains an average value of approximately 0.44 (Marcus et al., 1990; Raheman & Jindal, 2002). It is noteworthy that laminar flow may be expected only for Reynolds numbers (Re) less than 2,300 (Stein, 2004; Fox et al., 2012).


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(a)

(b)

Figure 1. 3-D model of the prototype chickpea harvester (a). A, chassis; B, pulley; C, duct; D, cyclone separator; E, holding arm; F, gauge wheel; G, reel; H, adjustable screw; I, platform; K, centrifugal fan; L, gear box; M, suction entrance. The prototype constructed for chickpea harvesting (b).

Figure 2. Schematic view of the cyclone separator. (D: Body diameter; E: diameter of air exit; H: length of body; I: diameter of air inlet; S: length of vortex finder; X: diameter of material outlet; L: length of exhaust; W: diameter of vortex finder).

Terminal velocity A stationary particle falling in a fluid will initially experience high acceleration. As the particle accelerates, the drag force increases, which causes a decrease in the acceleration. Eventually, a force balance is achieved when the acceleration is zero and the single particle terminal velocity is reached (Rhodes, 2008). Vertical wind tunnels and theoretical calculations were used to determine the terminal velocity of chickpea seeds (Mohsenin, 1986; Gorial & O'callaghan, 1990; Rabani et al., 2002; Tabatabaeefar et al., 2003; Kilikan & Güner, 2010; Gürsoy & Güzel, 2010; Razavi et al., 2010). However, for Re higher than 50, the drag coefficient curves level off, and therefore, the as-sumption of sphericity results in considerable error (Mohsenin, 1986; Gorial & O'callaghan, 1990; Marcus et al., 1990). As the Re for chickpea grains is 6,800 (Gorial & O'callaghan, 1990), the sphericity-based theoretical calculation of terminal velocity is not valid. A vertical wind tunnel was used to measure the terminal velocity of chickpea grains. The experimental results confirmed that the terminal velocity of chickpea grains varied within the range of 13–18 m·s-1 for different moisture contents. A hot wire anemometer was employed to obtain the values of the velocities.Development of the machineIn 2008, a modified stripper harvester was designed and developed for chickpea harvesting. In 2011, the machine was redesigned to use: 1) the maneuverability and low weight of tractor-mounted frames, 2) the flexibility of pneumatic conveyors, and 3) the adaptability of floating headers (Figure 1). A platform 1.4 m wide with 27 V-shape teeth, accompanied by a reel with 6 bats, a 700 mm peripheral diameter, and a kinematic index of 1.8, produced a stripper header for chickpea harvesting. The header assembly, which is on top for transport, rotates to the offset position for harvesting. A gauge wheel guides the header and transmits power to the reel, a ground wheel reduces machine vibration and losses, a three-linkage bar provides operational safety, and an adjustable screw sets the working height. The design of the original header (Golpira et al., 2013) and its improvements are not discussed here; only the final design is presented. Pneumatic conveyorA mobile vacuum conveyor, which was an innovator open system, was designed for the dilute phase transferring mode of grain and MOG. A centrifugal fan, cyclone separator, power transmission unit, and ducts are the functional


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Figure 3. Air velocities in four suction inlets. These velocities are average for 20 values measured in fan speed of 1320 rpm.

Table 2. The geometrical variables of the cyclones designed for separating harvested material from air flow

Variables D d/D I/D W/D L/D S/D H/D Vout/Vin

*Model 7.5 0.73 0.37 0.8 0.8 3.5 -

**Conventional - 0.25-0.40 0.5 0.5 - - - -

Designed cyclone

32 0.60 0.40 0.43 0.53 0.93 2.15 0.65

Redesigned cyclone

32 0.68 0.40 0.40 0.53 0.43 1.68 0.90

The values of Vout/Vin are average of 20 samples.*Model is designed based on cyclone separators used in conventionalvacuum cleaners. **The design variables for cyclone separators prepared by Hoffmannand Stein (2008).

Table 3. Functional operators of the prototype harvester

Part Value

Platform

Length (mm) 400

Width (mm) 1,400

Thickness (mm) 6

Reel

Length (mm) 1,400

Reel diameter (rpm) 700

Number of bats on reel (dimensionless) 6

Kinematic index 1.8

Centrifugal fan

Impeller diameter (mm) 500

Impeller length (mm) 1,000

Air capacity (m3 s-1) 0.26

Cyclone separator

Length (mm) 537

Body diameter (mm) 320

Outlet diameter (mm) 217

Air inlet and exhaust diameter (mm) 130

Prototype harvester

Weight (kg) 350

Working height (mm) 50

Working width (mm) 1,400

Machine width in road (mm) 1,600

Machine length (mm) 1,300

operators of the transferring system. A feeding system was designed using a fan in the grain cleaning system of a conventional Combine harvester (Iran Combine Manufacture Company, models 955 & 1055) from the area. The original double-suction centrifugal fan was modified to single-suction for delivering air through the pipes and the discharge point. The fan transfers the harvested material, which falls onto the header, then into a cyclone separator (Figure 2). The cyclone separates the harvested material using air flow and settles it in a grain discharge tank 1 m high. A power take-off powered gearbox, accompanied by two pulleys with a 2.2:1 reduction-pulley, transverses and directs power to the centrifugal fan. The pipe peripheral diameter and length from the upstream of the suction inlet to the downstream of the discharge port are 13 and 350 cm, respectively. This continuously operating system was modified based on test data of air volumetric flow rate produced by the fan at the suction inlet. Air velocities ranging from 5 to 30 m·s-1 were provided by fan speeds of 330–1,200 rpm, corresponding to power take-off speeds of 150–540 rpm (Figure 3). The volumetric flow rate (i.e., capacity) of the air produced by the fan is calculated by (Wohlbier, 2000): VdQ

4

214.3 (1)

where Q is the volumetric flow rate of air in m3·s-1 and V is the air velocity in m·s-1. The air capacity is 0.26 m3·s-1 (1,053 kg·h-1) at an air velocity of 20 m·s-1. According to Eq. 2, at a spot work rate of 0.42 ha·h-1 (which will be discussed later) and a crop yield of 300 kg·ha-1, the mass flow rate is 126 kg·h-1.

hkg

hakg

hha 12630042.0 (2)

The gas–solid disengaging system was fabricated based on the variables for conventional vacuum cleaners, and it


106

Figure 4. Evaluation of the prototype chickpea harvester in field.

Table 4. Physical properties of chickpea (Kabuli) during harvest

Crop properties Measured value SD Range

Grain weight (g) 0.25 0.1 0.12-0.52

Moisture content (% w.b.) 14 1.6 11.5-16

Plant height (cm) 22.4 0.5 10-33

Grain to pod weight ratio (g/g) 0.75 0.2 0.34-0.88

Pod detaching force (N) 7.5 2 3.45-8.86

The measured values are average of 50 samples.

was redesigned based on the geometrical variables of cyclones prepared by Hoffmann and Stein (2008). The design relied on the process of “suck it and see” to obtain the best solution for chickpea transportation and separation. Two cyclones were developed and evaluated with respect to the ratio of velocities in the inlet and outlet ports (Table 2). In addition, a pod harvester with a stripper header and a pneumatic conveyor was designed and constructed for chickpea harvesting. The design characteristics of the prototype harvester are presented in Table 3. The machine height, total width, and effective width are 1,400, 2,700, and 1,400 mm, respectively. The important features include low construction weight (350 kg) and low transportation width (1,600 mm). These features provide excellent mane-uverability, allowing short turns and superior conformance to crop rows. EvaluationHarvesting loss, maneuverability, cost, and field capacity were the harvesting performance factors that were evaluated during the field experiments (Figure 4). The experiments

were conducted during the summer of 2013 using a very common chickpea variety, Kabuli, on typical fallow fields. Grains were sown at 35 cm row spacing using a seed drill. Evaluation was conducted at two sites: Dooshan farm of the Kurdistan Agricultural Research Center and Saral farm of the Agricultural Research Station, at heights of 1,200 and 2,200 m above sea level, respectively. These two sites provided different maturity times, and as a result, approximately two months for evaluation and improvement of the prototype. The crop properties during the trials are presented in Table 4. A 50 mm stripping height was experimentally determined as optimum. The experimental area and layout were detailed by Golpira (2013).Results and DiscussionThe evaluation results confirm the effectiveness of the prototype and of the modified stripping methodology for chickpea harvesting. For a forward speed of 3 km·h-1, a working width of 1.4 m, and a field efficiency of 60%, the spot work rate (according to Eq. 3) and effective field capacity were 0.40 and 0.25 ha·h-1, respectively.

hha

ham

kmmm

hkm 25.0

210000%6010004.13

(3)Chickpea harvesting takes 8 man-days per 1 ha (at 8 working hours in a day), or 0.015 hectares per hour (Table 5). According to Eqs. 4 and 5, a farm laborer harvests 9 ha·yr-1, whereas the machine completes 150 ha·yr-1. The stripper harvester work equals 16.6 farm laborers for chickpea harvesting.

yearha

yearmonth

monthday

dayh

hha 923010015.0 (4)

yearha

yearmonth

monthday

dayh

hha 1502301025.0 (5)

This justifies the price of the equipment, which is $4,000, as it will be compensated during the economic life


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Table 5. Performance factors of the chickpea stripper harvester compared to those in manually and mechanized harvesting

Performance/harvesting system work rate (ha h-1) Total losses (%) Purchase price ($) Cost ($ ha-1)

The prototype harvester 0.25 25±10 4,000 17.66

Combine harvester - **20-50 40,000 -

*laborer 0.015 <5 - 80

* The row shows data for manual harvesting.**this value is for the irrigated chickpea.

(10 years) of the harvester. Further, the projected purchase price of the chickpea stripper harvester is only 10% of the price of a conventional combine harvester in the area. Eq. 6 shows that the cost of the machine is 2.66 $·ha-1. If the cost of a hired tractor, which is about 15 $·day-1, is added, the total cost of the chickpea stripper harvester is 17.66 $·ha-1. The labor requirement for crop collection from the field is not included.

hayearha

year$66.2150$400 (6)

According to Eq. 7, the cost of manual harvesting is 80 $·ha-1 at a labor wage of 10 $·day-1.

hadaymanha

dayman $80$108 (7)In addition, the floating stripper header was properly adapted with a pneumatic conveyor system and chassis to recover grains from the field with minimum losses. Field losses during harvesting have been reduced to approximately 25%. The sparse research available confirmed that the maximum losses for manual harvesting of chickpeas are close to 5%. Losses are due to bent or flattened material being passed over by the platform, grain falling from the platform’s front edge, and grain shattered on the ground by the reel. Occasional blocking of the platform’s slots with tall or immature weeds was another reason for the losses. The header is the main source of losses, whereas the conveyor simply and effectively transfers harvested material. Increasing the volumetric flow rate and air-to- material ratio, via redesign of the centrifugal fan, would improve conveyor performance. Replacing the cyclone separator with a gravity chamber will be considered for the next stage of modification.

ConclusionAvailable information on the physical, mechanical, and aerodynamic properties of chickpea seeds was reviewed for modification of a previously constructed chickpea stripper harvester. The flexibility of pneumatic conveyors, maneuverability of tractor-mounted frames, and adaptability of floating headers were utilized to increase machine performance. A centrifugal fan and cyclone separator were designed based on the grain’s terminal velocity (18 m·s-1), which was measured by the vertical wind tunnel method. The design characteristics of the pneumatic conveyor are: 1) a volumetric flow rate of 0.26 m3·s-1 or 1,053 kg·h-1; 2) an effective air velocity of 20 m·s-1; and 3) a mass flow rate of 126 kg·h-1. Superior maneuverability, low operating costs, and reasonable purchase price, along with a spot work rate of 0.42 ha·h-1, support the com-mercialization of the new methodology and machine for chickpea harvesting. The prototype provides an alternative to manual harvesting with both cost and time savings. Upgrading the conveyor system via soft and hard modeling would allow acceptable performance.Conflicts of InterestThe authors have no conflicting financial or other interests.AcknowledgementsThe author thanks the research fund of the Iran National Science Foundation (INSF) for supporting the 89003079 project. He also appreciates the contributions made by the staffs of Saral and Gerizeh Agriculture Research Station in Kurdistan for supporting the field experiments. And finally, he gives a special thanks to Mr. Hemin Golpira (PhD candidate) for his assistance in machine fabrication


108

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No. 28969 (In Farsi).Nomenclature

d: Pipe peripheral diameter (m)Q: Volumetric flow rate of air (m3·s-1)V: Air velocity (m·s-1)

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