# Studies on the Energy Consumption of Material Cutting in the Onion Peeling Process
## 2 Materials and Methods  
In order to obtain an answer to the research problem indicated above, a test stand experiment was planned according to a scheme showing correlations between independent variables, dependent variables, constant factors, and disturbing factors. In the experiment, the independent variables included material speed \(vp\), depth of cuts in the outer shell \(d_{n}\), number of air nozzles \(nd\), distance of air nozzles from the cut material \(hd\), air pressure supplying the nozzle system \(p\), while the unit energy consumption \(Ej\) was selected as the dependent variable. The studies were conducted within fixed ranges of temperature and humidity for both environment and material tested and for a specific onion variety. The parameters were described as constant factors: onion variety \(o_{c}\), onion diameter \(d_{c}\), ambient humidity \(w_{o}\), ambient temperature \(T_{o}\). The material in the main studies was onions of the Bonus variety, due to the processing susceptibility and high popularity of this variety. The independent and dependent variables were defined on the basis of an analysis of the literature on the theory and design of agricultural and processing machinery and preliminary own research. The values of the independent variables that were adopted in the experimental studies are summarised in Table 1, while the dependent variable was defined as the unit energy consumption for carrying out the process and \(E_{j}\) was determined to be the ratio of the sum of the energy consumed to carry out the process of cutting off the ends and removing the outer scales to the weight of the onion peeled per unit time. Scientific research was conducted for materials with diameters of 50-70 mm in a warehouse where the humidity and ambient temperature were controlled. The number of repetitions in the experiment was based on previous trials and statistical calculations. The number of repetitions was set to 10 with a significance level of \(\alpha=0.05\) and the permissible estimation error was d = 2%. The station where research on the energy consumption of onion cutting was carried out was built by the authors [13]. Figure 1 shows a view of the test stand. The cutting system was designed as two discs with a diameter of 200 mm (Figure 2). The copying system installed in the station makes it possible to change the spacing of the knives depending on the size of the material being cut. The technological process involving peeling the onion is carried out by first cutting off the ends of the material by disc knives (Figure 3), followed by the cutting and blowing off of the skins (Figure 4). In order to perform a measurement of the load torque of the motor driving the disc knives performing the heel trimming and the residual chive, constructional alterations were made to the test stand by changing the method of driving one of the cutting knives. While during the operation of the machine under processing conditions the cutting knives are driven via a belt transmission system by a single motor built into a chamber located directly above the end-cutting and skin-incision space, a separate drive of one of the knives was used for the torque measurement by means of an additional induction motor. This operation consisted of fixing the motor in such a way as to allow it to rotate freely around an axis that was the axis of symmetry of the drive shaft. \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Independent Variables**} & \multicolumn{4}{c}{**Values of Variables**} \\ \cline{2-5}  & \(x_{1}\) & \(x_{2}\) & \(x_{3}\) & \(x_{4}\) \\ \hline Material speed \(v_{p}\) [pcs\(\cdot\)min\({}^{-1}\)] & 30 & 45 & 60 & \\ Depth of cuts in the outer shell \(d_{n}\) [mm] & 1.5 & 1.25 & 3 & \\ Number of air nozzles \(n_{d}\) [pcs.] & 2 & 3 & 4 & \\ Distance of air nozzles from the cut & 20 & 30 & 40 & \\ material \(h_{d}\) [mm] & 20 & 30 & 40 & \\ Air pressure supplying the nozzle & 4 & 5 & 6 & 7 \\ system \(p\) [bar] & 4 & 5 & 6 & 7 \\ \hline \hline \end{tabular}
\end{table}