Original Article J. of Biosystems Eng. 40(2):102109. (2015. 6) http://dx.doi.org/10.5307/jbe.2015.40.2.102 Journal of Biosystems Engineering eissn : 22341862 pissn : 17381266 Redesign and Evaluation of a Chickpea Harvester H. Golpira* Department of Biosystems Engineering, University of Kurdistan, Sanandaj, Iran Received: November 2 nd, 2014; Revised: November 19 th, 2014; Accepted: January 28 th, 2015 Purpose: Slow manual harvesting of rainfed chickpeas cultivated in fallow fields in developing countries have encouraged the design of a mechanical harvester. Methods: A tractorpulled 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 tractormounted 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 Introduction Harvesting 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 rainfed chickpeas. Both manual and mechanized harvesting methodologies were reported for chickpeas (Diekmann, 2011; Gaur, 2011); however, rainfed 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 *Corresponding author: H. Golpira Tel: +988716620552; Fax: +988716620553 Email: h.golpira@uok.ac.ir reaper for chickpea harvesting, where machine blockage with weeds was the main problem. BehrooziLar 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 tractorpulled stripper harvester was designed in which passive fingers with Vshaped 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 tractorpulled frames, and high Copyright c 2015 by The Korean Society for Agricultural Machinery This is an Open Access article distributed under the terms of the Creative Commons Attribution NonCommercial License (http://creativecommons.org/licenses/bync/3.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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 introduced by Golpira et al. (2013). The flexibility of pneumatic conveyors, maneuverability of tractormounted 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; BehroziLar & 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 (R e ) less than 2,300 (Stein, 2004; Fox et al., 2012). 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 ) 1318 Gorial & 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 (%) 86 Length (mm) 9.34 Gorial & O'callaghan, 1990; Kaur et al., 2005; Kilikan & Güner, 2010; Shahbazi, 2011 Width (mm) 7.72 BehroziLar & Mohtasebi, 2003; Konak et al., 2002 Thickness (mm) 7.75 Geometric mean diameter (mm) 8.5 Gorial & O'callaghan, 1990 Mass (mg) 370 True density (kg m 3 ) 1404 Gorial & O'callaghan, 1990; Gürsoy & Güzel, 2010 Bulk density (g ml 1 ) 0.64 Volume (ml) 19.5 Kaur et al., 2005 Hardness (kg) 3.3 Impact velocity 10 Khazaei et al., 2003; Shahbazi, 2010 Coefficient of friction on galvanized surface 0.28 Coefficient 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. Tabatabaeefar et al., 2003 103
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 R e higher than 50, the drag coefficient curves level off, and therefore, the assumption of sphericity results in considerable error (Mohsenin, 1986; Gorial & O'callaghan, 1990; Marcus et al., 1990). As the R e for chickpea grains is 6,800 (Gorial & O'callaghan, 1990), the sphericitybased 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 machine In 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 tractormounted frames, 2) the flexibility of pneumatic conveyors, and 3) the adaptability of floating headers (Figure 1). A platform 1.4 m wide with 27 Vshape 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 threelinkage 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 conveyor A mobile vacuum conveyor, which was an innovator open system, was designed for the dilute phase transferring (a) (b) Figure 1. 3D 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). mode of grain and MOG. A centrifugal fan, cyclone separator, power transmission unit, and ducts are the functional 104
H. Golpira. Redesign and Evaluation of a Chickpea Harvester 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 doublesuction centrifugal fan was modified to singlesuction 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 takeoff powered gearbox, accompanied by two pulleys with a 2.2:1 reductionpulley, 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 s1 were provided by fan speeds of 330 1,200 rpm, corresponding to power takeoff 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): 3.14d 2 Q V 4 ha kg kg 300 126 h ha h 0.42 (2) The gas solid disengaging system was fabricated based on the variables for conventional vacuum cleaners, and it Table 2. The geometrical variables of the cyclones designed for separating harvested material from air flow Variables D d/d *Model 7.5 0.73 **Conventional I/D W/D L/D S/D H/D Vout/Vin 0.37 0.250.40 0.5 0.8 0.8 3.5 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 conventional vacuum cleaners. **The design variables for cyclone separators prepared by Hoffmann and Stein (2008). Table 3. Functional operators of the prototype harvester Part Value Platform (1) where Q is the volumetric flow rate of air in m3 s1 and V is the air velocity in m s1. The air capacity is 0.26 m3 s1 (1,053 kg h1) at an air velocity of 20 m s1. According to Eq. 2, at a spot work rate of 0.42 ha h1 (which will be discussed later) and a crop yield of 300 kg ha1, the mass flow rate is 126 kg h1. Length (mm) 400 Width (mm) 1,400 Thickness (mm) 6 Reel Length (mm) Reel diameter (rpm) Number of bats on reel (dimensionless) Kinematic index 1,400 700 6 1.8 Centrifugal fan Impeller diameter (mm) 500 Impeller length (mm) 1,000 3 1 Air capacity (m s ) 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) Figure 3. Air velocities in four suction inlets. These velocities are average for 20 values measured in fan speed of 1320 rpm. 350 Working height (mm) 50 Working width (mm) 1,400 Machine width in road (mm) 1,600 Machine length (mm) 1,300 105
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 maneuverability, allowing short turns and superior conformance to crop rows. Evaluation Harvesting 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 Discussion The 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. km 3 1.4 h km 2 ha m m ha m 1000 60 % 10000 0.25 h (3) Chickpea harvesting takes 8 mandays 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. 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 0.120.52 Moisture content (% w.b.) 14 1.6 11.516 Plant height (cm) 22.4 0.5 1033 Grain to pod weight ratio (g/g) 0.75 0.2 0.340.88 Pod detaching force (N) 7.5 2 3.458.86 The measured values are average of 50 samples. ha 0.015 10 h ha 0.25 10 h h day h day 30 30 day month day month month 2 9 year month 2 150 year ha year ha year (4) (5) This justifies the price of the equipment, which is $4,000, as it will be compensated during the economic life 106
Table 5. Performance factors of the chickpea stripper harvester compared to those in manually and mechanized harvesting Performance/harvesting system work rate (ha h 1 ) Total losses (%) Purchase price ($) Cost ($ ha 1 ) The prototype harvester 0.25 25±10 4,000 17.66 Combine harvester **2050 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. $ 400 150 year ha year $ 2.66 ha (6) According to Eq. 7, the cost of manual harvesting is 80 $ ha 1 at a labor wage of 10 $ day 1. man day $ $ 8 10 80 ha man day ha (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 airtomaterial 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. Conclusion Available 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 tractormounted 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 m 3 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 commercialization 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 Interest The authors have no conflicting financial or other interests. Acknowledgements The 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 107
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