Reconciling optimization of fuel consumption and distribution regularity in a tractor sprayer can be a challenge when applying pesticides, but it is something that can be done.
The cost of food production is made up of the addition of operations and resources used during the production process. With the growing competitiveness of agriculture and the rise in prices for inputs and energy for production, rural administration becomes an important tool for improving efficiency in production and planning agricultural activities, making it necessary to seek alternatives to reduce expenses during operations to reach the final product.
The mechanized activities of soil preparation, sowing, cultural treatments and harvesting require high fuel consumption to be carried out. According to data from the Rio Grandense do Arroz Institute (Irga, 2013), the estimated fuel expenses in rice farming operations represent approximately 6% of the total production cost. In other cultures, this percentage is even higher, elucidating the importance of managing mechanized activities. The applications of pesticides for pest control constitute one of the most important activities for obtaining greater productivity in crops, controlling agents that lead to a reduction in the crop's potential to produce, and are also one of the most expensive. In this context, it is important to seek alternatives to reduce the costs of this operation.
For the application of pesticides using sprayers driven by the power take-off (TDP), it is recommended that they be used at their nominal speed of 540rpm during application, as the pump used in the sprayer to pressurize the system is normally sized to work at this level. rotation. When this recommendation is not followed and the engine speed is lower than recommended, there are two fundamental negative aspects from the sprayer's point of view: poor pressurization of the spray, which can cause oscillations in the boom and a reduction in the useful life of the pump components ( Jacto, 2001). However, when using these recommendations, the pump will produce an excessive flow of syrup, where much of it will return to the tank, hydraulically agitating the mixture present in the sprayer tank. The effectiveness of phytosanitary products depending on their formulation may be influenced when using lower TDP rotations, which may cause problems with the homogeneity of the mixture. Even so, many farmers do not use this indication, as they believe that it is a very high tractor rotation, generating greater fuel consumption and greater system wear, as observed by Dornelles (2008) in a study on the technical inspection of sprayers. in Rio Grande do Sul, which identified that only 20,23% of the sprayers evaluated used the ideal work rotation during the application process.
Another concern regarding working rotation is the noise caused at the tractor's operating station, which is directly proportional to the increase in rotation, which can cause health problems for the operator when he does not use hearing protection. To obtain more information about this operation, a group of researchers from Unipampa carried out work with the aim of evaluating the fuel consumption and distribution regularity of a tractor-sprayer set at different engine speeds and in different working gears.
To conduct the experiments, a TL 75 4x2 TDA tractor was used with a power of 55,2kW (75hp) at 2.400rpm and a torque of 264Nm at 1.400rpm, with 700 hours of use, year of manufacture 2011. The sprayer used was from Jacto brand, Falcon Vortex 600 model, mounted on the tractor's three-point hitch system. Fuel consumption was measured using a graduated auxiliary fuel tank, with a capacity of one liter, allowing visualization of the volumetric consumption of diesel oil, together with a hose connecting the auxiliary tank to the tractor's feed pump, which fed the system with fuel. This reservoir replaced the tractor's fuel tank, being a source of diesel oil for the feed pump and receiving the volume that returned from the system and was not burned by the tractor engine.
For measurements, a 400m path was established in a flat area, where the volume of fuel necessary to complete the path in the different treatments was calculated. On this route, the sprayer had half the reservoir capacity in all observations. The regularity of distribution in the bar was measured by the relationship between the expected flow and the obtained flow and by calculating the coefficient of variation in the bar. The treatments consisted of a combination of three working gears and four engine speeds: 1.600rpm, 1.800rpm, 2.000rpm and 2.200rpm in a completely randomized design with three replications. Jacto ADI 11002 fan and ATR 4,0 empty cone spray tips were used at two working pressures within the range recommended by the manufacturer.
During the experiment it was possible to notice that when changing the speed from 3,82km/h to 9,1km/h, changing the gear, but at the same working speed (1.600rpm), there was an increase of 36,5% in fuel consumption. fuel (Graph 1). For the 1.800rpm rotation, the increase was 31,02% in hourly consumption between 4,34km/h and 10,21km/h. Similar results were found by Trintin et al (2005), evaluating the energy demand for a seeder-fertilizer, finding an increase of 35,9% with the speed variation from 4,2km/h to 6,5km/h, maintaining the rotation at 1.750rpm. At speeds of 2.000rpm and 2.200rpm, hourly consumption was slightly higher at speeds of 7,74km/h and 8,47km/h, respectively, with little variation in consumption at higher speeds. This can be seen in Table 2 of the statistical analysis, which shows that there was no significant difference between the two highest rotations.
From the average data, the straight line regression equation and the sample determination coefficient were arrived at. It was possible to observe a linear increase in hourly mass fuel consumption depending on the different rotations, showing the highest consumption at the highest working rotation. These results are in line with those found by Almeida et al (2010), who obtained higher consumption when the tractor is operated at higher rotations and higher speeds.
It was also possible to verify in the experiment that when using gears that provide higher speeds within the same rotation, operational consumption reduced by around 44%, for rotations of 1.600rpm, 1.800rpm and 2.000rpm (Graph 2). When using 2.200rpm, the reduction in operational consumption was 53% when going from 5,25km/h to 12,66km/h. Therefore, the use of gears that provide higher speeds presents reductions in operational consumption, as they provide greater effective field capacity. However, it is necessary that the area is suitable for higher speeds, also considering the type of sprayer.
Some limitations may be observed when using higher speed at lower speeds, due to the loss of tractor power in areas that require greater torque to maintain the tractor's rotation. Although the tractor is working within its torque reserve, it will be more susceptible to fluctuations in rotation and therefore this condition of low rotation and high speed is restricted to a few conditions of normal use, where the tractor is not constantly overloaded.
For the pressures applied to the ADI 11002 tip (20 and 45psi), the highest relative error occurred at 1.800rpm, 2.200rpm and 2.000rpm, respectively, not representing a trend, revealing no difference in flow rates per nozzle when using rotations lower than those indicated (Table 1). This parameter is calculated based on the expected flow and the flow observed in the collections. The coefficient of variation in the bar showed small variations between the applied rotations, with higher values at the highest operating pressure.
For the ATR 4 tip, the average error values were lower at 1.600rpm for 60psi pressure and 2.200rpm for 105psi, with no trend in the observed data (Table 2). The coefficient of variation in the bar remained low at all pressures applied and had little variation within the rotations used, showing that there was no effect of engine rotation on distribution regularity as long as the system pressure was maintained.
After carrying out this field test, it is clear that it is possible to obtain lower fuel consumption by adjusting the tractor's gear and working speed. Using the same speed at different speeds provides a reduction in operational consumption at lower speeds, due to lower hourly consumption at these speeds. However, the operator must be aware of the need to agitate the syrup and the operating conditions in order to choose the best gear/working speed combination. For the spray tips and pressures studied, it is possible to apply pesticides at lower speeds than recommended without influencing the uniformity of bar application and the average flow rate of the spray tips.
Bruna Batistella, Vilnei de Oliveira Dias, Tiago Lopes, Alcionei Dallaporta, Bruno Bisognin, Camila Dalcin, Lamap/Unipampa
Article published in issue 169 of Cultivar Máquinas
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