Combine Harvester PDF

Harvesting of Paddy Combine harvesting systems The combine harvester combines all operations: cutting the crop, feeding it into the threshing mechanism, threshing, cleaning, and discharging grain into a bulk wagon or directly into bags. Straw is usually discharged behind the combine in a windrow....

Harvesting of Paddy Combine harvesting systems The combine harvester combines all operations: cutting the crop, feeding it into the threshing mechanism, threshing, cleaning, and discharging grain into a bulk wagon or directly into bags. Straw is usually discharged behind the combine in a windrow. Tractor-drawn combine harvester Self propelled combine harvester Cutter Bar Width: 4 feet Rated Feed Capacity (kg/s): 1.5 kg/s Cutter Bar Width: 6-8 feet Engine Output And Rotating Speed Power Output: 35 to 70 HP (HP/rpm): 22HP / 27HP/ 2200 r/min Cutting capacity: 1.5 acres/hour Track combine harvester  Harvesting of Paddy Combine harvesting systems Advantages: 1. Reduces labor requirement and drudgery 2. Scheduled operation avoiding adverse conditions (untimely rain, storm, fire hazard, etc) 3. Time saving 4. Provides opportunity for early harvest, and time for seedbed preparation for next crop Disadvantages: 1. High initial investment cost 2. Difficult to maneuver in small and irregular shaped field 3. Loss of straw 4. High operational and repair cost  Harvesting of Paddy Separating Unit Threshing Unit Header Unit Cleaning Unit The yellow stream is the crop, orange is chaff, blue is forced air, and red is the grain. 1) Reel 6) Threshing drum 12) Bottom sieve 18) Driver's cab 2) Cutter bar 7) Concave 13) Tailings conveyor 19) Engine 3) Header auger 8) Straw walker 14) Rethreshing of tailings 20) Unloading auger 4) Grain conveyor 9) Grain pan 15) Grain auger 21) Impeller 5) Stone trap 10) Fan 16) Grain tank 11) Top Adjustable sieve 17) Straw chopper  Harvesting of Paddy Reel Hold and guide the crop towards the cutter bar until it has been cut and lay it on cutter bar platform. Diameter ranges between 1-1.5 m Hydraulic attachments are used to adjust the height and clearance from cutter bar Types: bat type (good for standing crop with small size grain, shattering loss due to slap) pick-up type/tyne type (also benefits the lodged crop) Vertical adjustment (height of cut 7.5-90 cm) Horizontal adjustment (distance between cutter bar & reel, should be high for lodged crop, 230-300 mm )  Harvesting of Paddy Reel Reel speed should be It should run fast without shattering the grain or throwing the cut crop out of the cutter bar Should move the harvested crop smoothly over the header platform In general same or little more than forward speed of combine Reel Index 𝑃𝑒𝑟𝑖𝑝ℎ𝑒𝑟𝑎𝑙 𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑟𝑒𝑒𝑙 𝑅𝑒𝑒𝑙 𝑖𝑛𝑑𝑒𝑥 = 𝐹𝑜𝑟𝑤𝑎𝑟𝑑 𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑐𝑜𝑚𝑏𝑖𝑛𝑒 Optimum range: 1.25-1.5 for upright crops Reel index for lodged crops is less compared to upright crops  Harvesting of Paddy Platform auger Due to spiral movement of auger conveyer, crop is collected from the entire length brought to center. Prongs take the crop and pushes them to conveyer chain of feeder assembly. Vertical height adjustment is done to maintain the clearance between auger conveyer flight and header platform, generally 20 mm. Diameter of the auger ranges from 40-60 cm Flight Prongs Platform auger  Harvesting of Paddy Feeder conveyer To convey the harvested crop to threshing unit Set of sprocket fixed on two shaft. Serrated mild steel slats are fitted across chain length, which restricts the crop to roll back and convey efficiently  Harvesting of Paddy Threshing Unit Removal of grain from ear head or pods Works on impact force on crop by the rotating threshing cylinder, resulting in separation of grains from ear head Rubbing action between crop layers over each other while passing through constricted space between concave and cylinder Types: raspbar, 6-8 in no. (wheat), spike tooth (rice) Threshing Factors affect threshing effectiveness Cylinder Peripheral speed of cylinder Clearance between concave & cylinder Number of rasp-bar or spike tooth Type of crop Moisture content of crop Feed rate Concave  Harvesting of Paddy Straw walker Separate the grains from long chaff. The grains drop on oscillating grain pan and throws out long straw out of machine. Speed of straw walker is 200 cycles/min Number of straw walker varies from 4-7 in number and kept in cascade steps to improve the separation Length of straw walker is 4 m. Speed of straw walker is 190-200 rpm.  Harvesting of Paddy Grain cleaning unit Separate and clean the grain from straw. Returns the unthreshed ear heads to threshing unit for re-threshing Throws out the chaff dust and short straw out of the machine Consists of 2-3 oscillating sieves and blower having 4-6 blades. Tailing is the unthreshed ear heads that are heavy to be blown out of machine and large enough to pass through sieve opening  Harvesting of Paddy Factors affecting combine performance Machine parameters: Crop parameters: ▪ Speed of reel and its position ▪ Crop moisture content & its ▪ Cutter bar speed & its adjustment condition ▪ Speed of threshing cylinder ▪ Time of harvest ▪ Speed of straw rack, sieve & ▪ Crop density blower ▪ Crop variety ▪ Machine vibration Operating parameters: Field parameters: ▪ Forward speed of combine ▪ Size & shape of field ▪ Height of cut ▪ Soil moisture content during ▪ Direct of cut w.r.t. plant orientation harvesting  Harvesting of Paddy Sources of grain loss Header loss/Cutter bar loss: It is determined on those portions of ground, which are protected from combine afflux by the use of rolls of cloth. The loose grains and complete and incomplete ear heads fallen on the marked area, where pre-harvest losses were determined, shall be collected manually. Grain shattered by reel (speed, over matured crop, improper adjustment) Grain shattered by cutter bar (excessive vibration) Dropped before reaching the platform Missed by cutter bar due to improper registration or height adjustment Cylinder loss: Amount of unthreshed grain found from straw walker and cleaning sieve  Harvesting of Paddy Sources of grain loss Rack and shoe loss: For determining the rack and shoe loss, the straw and chaff afflux is collected separately. To collect these, two rolls of cloth 30 m in length and one and half times the width of straw/chaff outlet is suspended on especially attached fittings beneath the rear of machine. As the sheets of cloth unroll, one sheet retains the afflux from straw walker and other from sieve for 20 m run length. Unrolling operation starts 5 m in advance and terminates 5 m ahead of end point. Pre-harvest loss: It is determined at minimum of three places randomly selected in the field where combine harvester is to be operated. The sample should be collected from the area having one-meter length in the direction of travel and full or half width of cutter bar of machine depending upon its size. All the loose grains, complete and incomplete ear heads fallen in the marked area have to be picked up manually without vibrating the plants before the machine is to be operated. This will give pre-harvest loss.  Harvesting of Paddy Factors affecting grain loss Machine parameters: Crop parameters: ▪ Threshing cylinder speed ▪ Moisture content of crop ▪ Cylinder-concave clearance ▪ Lodging of crop ▪ Forward speed ▪ Variety of crop ▪ Reel index ▪ Crop density ▪ Reel position ▪ Height of cutter bar ▪ Blower speed ▪ Opening if cleaning sieve  Tutorial A combine harvester having 4.20 m cutter bar is tested for harvesting crop and the following data was obtained i. Total area harvested = 100 m² ii. Time taken = 20 sec iii. Free seed over rack = 150 g iv. Unthreshed over rack = 100 g v. Free seed over shoe = 500 g vi. Unthreshed over shoe = 150 g vii. Net grain collected in combine tank = 50 kg viii. Average cutter bar loss = 10.20 g/m² Determine: (i) Total seed yield and total seed loss in kg/ha, respectively (ii) Various combine losses and total combine loss as percent of total seed yield (iii) Reel index, if peripheral speed of reel is 5.52 km/h  Tutorial Solution: Total harvested area = 100 m² (i) Total seed harvested = 0.15 + 0.1 + 0.5 + 0.15 + 50 + 1.02 = 51.92 kg Average cutter bar loss = 10.20 × 100 = 1020 g x 1.02 kg Total seed yield per ha = 51.92/0.001 = 5192 kg Total grain loss = 51.92 - 50 = 1.92 kg Total grain loss per ha = 1.92/0.9 = 192 kg (ii) Various combine losses Cutter bar loss = (1.02/51.92) × 100 = 1.96 % Rack loss: Threshed seed = (0.15/51.92) x 100 = 0.288 % Unthreshed seed = (0.1/51.92) x 100 = 0.192 % Shoe loss: Threshed seed = (0.5/51.92) × 100 Unthreshed seed = (0.15/51.92) x 100 Total grain loss = 0.15 +0.1+0.5 +0.15 + 1.02 = 1.92 kg Hence, grain loss in respect of total seed yield per ha = (1.92/51.92) x 100= 3.6 %  Tutorial Solution: Width of cutter bar = 4.20 m Total distance travelled = (100/4.2) = 23.8 m Total time taken to travel this length = 20 sec Hence, speed of operation would be = 23.8/20 = 1.19 m/s= 4.284 km/h Peripheral speed of the reel = 5.52 km/h Reel index = Peripheral speed of operation/Forward speed of operation=5.52/4.284 = 1.29  Design of Combine Harvester Design of header −2 1 𝑄 = 10 ∗ 𝑣ℎ ∗ ε ∗ 𝑙ℎ ∗ 𝑞𝑔 ∗ 1 + 𝛿` Q = capacity of combine, kg/sec 𝑣ℎ = harvesters working speed, m/sec ε = factor of use of cutting width, 0.9 - 0.951 𝑙ℎ = header length, m 𝑞𝑔 = yield of grain q/ha 𝑞𝑔 𝛿 ` = straw factor = 𝑞𝑠 (straw to grain ratio varies 0.6-1.2 for wheat 1-2.5 for paddy) The proportion between header length (𝑙ℎ ), length of drum (𝑙𝑑 ) and the surface of concave (𝑐𝑠 ) for different sizes of combine are as follows: 1. For small combines (𝑙ℎ ≤ 2.1 m), 𝑙ℎ : 𝑙𝑑 : 𝑐𝑠 ≤ 1: 0.37: 0.8 2. For medium combines (2.1 m < 𝑙ℎ < 3 m), 𝑙ℎ : 𝑙𝑑 : 𝑐𝑠 ≤ 1: 0.36: 1 3. For large combines (𝑙ℎ ≥3 m), 𝑙ℎ : 𝑙𝑑 : 𝑐𝑠 =1: 0.36 : (1.25-1.5)  Design of Combine Harvester Design of crop conveyer 𝑞𝑐 = 𝐿𝐶 ∗ 𝑊𝐶 ∗ ε ∗ 𝑣𝐶 ∗ ϒ𝑚 ∗ 𝑠 𝑞𝑐 = Conveyer output, kg/sec 𝐿𝐶 = Length of the inclined conveyer, m 𝑊𝐶 = Width of undershot conveyer, m ε = factor of filling 𝑣𝐶 = linear speed of conveyer, m/s ϒ𝑚 = bulk density of crop material in the conveyer belt, kg/m3 𝑠 = % slip of material in the conveyer slit Refer book Agricultural machines, theory and construction Vol 2 By Kanafojski & Karwowski  Design of Combine Harvester Capacity of horizontal feed auger 𝜋 2 𝐶𝑎 = 𝐷0 − 𝑑𝑖2 ∗ 𝑃 ∗ 𝑛 4 𝐶𝑎 = Capacity of auger, m³/min 𝐷0 = Outside diameter of flight strip, m 𝑑𝑖 = Inside diameter of flight, m P = pitch of auger, m 𝑛= rotational speed of feed auger, m/s Assuming the auger fill factor = 2, capacity of feed conveyer (tons per hour) : fill factor x C (m³/min) x tons/m³ x 60 Power to move material horizontally (𝑊ℎ ): 𝑊ℎ = (𝐶𝑎 ∗ 𝐿 ∗ F )/367 Power to lift material vertically (𝑊𝐿 ): 𝑊𝐿 = (𝐶𝑎 ∗ 𝐿 sinθ )/367 L = Length,m F= Multiplying power factor, if power is less than 1 kW it is equal to 1.5. If power lies between 1 & 2, take it as 1.25, If power lies between 2 and 4, take it as 1.1. If power lies between 4 and 5. take it as 1.0  Design of Combine Harvester Threshing Mechanism n= 𝑝𝑒𝑟𝑖𝑝ℎ𝑒𝑟𝑎𝑙 𝑠𝑝𝑒𝑒𝑑 (𝑣) n= no. of revolution, rps 𝜋𝐷 D = Dia of cylinder, m q= 0.25 ∗ 𝑅𝑏 ∗𝑛∗𝑙𝑑 ∗𝑘 q = feed rate of thresher 𝒓𝒂𝒔𝒑 𝒃𝒂𝒓 1+𝛿ሖ 𝑅𝑏 = number of rasp-bars. ሖ 𝑞 (1 + 𝛿) 𝑙𝑑 = 𝑛 = revolutions of threshing drum /sec 0.25 ∗ 𝑅𝑏 ∗ 𝑛 ∗ 𝑘 𝑙𝑑 = length of drum, m q = 𝑞𝑎 ∗ 𝑅𝑏 ∗ 𝑙𝑟 𝑘 = 0.17 - 0.32 kg per metre 𝑞𝑎 = allowable feed rate of thresher, 0.35- 𝑆𝑝𝑖𝑘𝑒 𝑡𝑜𝑜𝑡ℎ 𝑞 𝑣2 − 𝑣1 𝑣 0.4 kg/sec/m 𝑃= + 𝑚𝑣 + 𝑛𝑣 3 1 − 𝐶𝑓 P= power required for operation of thresher, watt q=feed rate to combine, kg/sec 𝑣1 = initial velocity of plants, m/sec 𝑣2 = velocity of plant mass after impact, m/sec 𝑣 = peripheral velocity of threshing drum, m/sec 𝑊𝑖𝑟𝑒 𝑙𝑜𝑜𝑝 𝐶𝑓 = coefficient of friction between straw and thresher, 0.6 (assumed) m = constant = 0.85 -0.90 N per 100 kg weight of threshing drum, n = a constant = 0.065 N-sec²/m² Velocity of plant mass after impact (v2) is given by, 𝑣2 = 𝛼 ∗ 𝑣 , 𝛼 = 0.7-0.8  Design of Combine Harvester Cleaning Mechanism L% = permissible grain loss from straw walker, 0.4- Length of straw walker 0.5% of total grain. 𝑓𝑠 ∗ 100 ∗ 𝑒 −𝜇𝐿𝑆 𝑓𝑠 = feed rate to straw walker (kg/sec), 20% of feed 𝐿(%) = rate 𝛿ሖ ∗ 𝑞 𝛿ሖ = straw factor q=amount of plant mass being fed to the combine Straw layer thickness (feed rate), kg/sec. ሖ 𝑞 (1−𝛿) μ = coefficient of separation, depends on straw layer h= thickness (h) on walker. 𝑊𝑆 ∗𝑣𝑎𝑣 ∗𝜌𝑠 𝐿𝑆 = length of straw walker, cm 𝑊𝑆 = width of straw walker, m Length of straw walker h = straw layer thickness, in m 𝜇 ℎ𝑙 𝑚 𝑣𝑎𝑣 = average speed of straw grain mass over straw = walker, m/s 𝜇𝑙 ℎ 𝜌𝑠 = bulk density of straw layer on the walker, usually it is 12-17 kg/m³ For h= 20 cm, 𝜇 =0.018/sec. So, m = 0.8 for heavy load, 1.2 for light load 𝜇𝑙 at any other layer thickness ℎ𝑙 can be determined  Design of Combine Harvester Cleaning Mechanism Width of sieve (𝑾𝒔 ) 𝑊𝑆 = 0.9 − 0.95 ∗ 𝑊𝑆𝑊 𝑊𝑆𝑊 = width of straw walker ƴ ): 0.15-0.17 kg/sec/decimeter of sieve width Specific load of sieve (𝑞𝑠𝑖𝑒𝑣𝑒 Sieve area (𝑨𝒔𝒊𝒆𝒗𝒆 ) 𝑞ƴ 𝐴𝑆𝑖𝑒𝑣𝑒 = 𝑞𝑠𝑖𝑒𝑣𝑒 ƴ 𝐴𝑆𝑖𝑒𝑣𝑒 = area of sieve, in m² ƴ = specific load of sieve (kg/sec/m²) 𝑞𝑠𝑖𝑒𝑣𝑒 𝑞ƴ = Q (1- 𝛿ሖ C), in kg/sec/m² Q = output of threshing unit 𝛿ሖ = straw factor C = coefficient which depends on moisture content of grain. The value of coefficient, C for different range of moisture content  Tutorial Q1. Determine the header length (Lh) of a 5.5 kg/s capacity self propelled combine harvester used in harvesting wheat crop (average yield 45.0 q/ha) at a speed of 5.4 km/hr. Assume that 90% of cutting width is utilized effectively during harvesting operation and straw factor for wheat crop as 1:1.5. Also design the threshing mechanism for the combine and power required to operate. Q2. Calculate the straw walker length for the combine harvester having a feed rate 5.5 kg/s in wheat crop. Assume permissible grain loss from straw walker as 0.3% of total grain output of combine and straw layer thickness on straw walker 15 cm. Also calculate the power requirement for threshing.