Mariusz Rząsa

This study investigates short-term natural gas consumption forecasting in the city of Ternopil and the contribution of different feature groups to forecasting accuracy. Synchronized natural gas consumption and meteorological observations from 2007 to 2019 were used. A total of 203 calendar, meteorological, and derived features were constructed. Six machine learning models, three naive baseline forecasts, and a seasonal ETS model were compared. Hyperparameters were optimized using Optuna, model performance was evaluated using six temporal folds with an expanding training window, and final testing was conducted on data from 2019. XGBoost achieved the lowest mean root mean squared error of 4307.13 ± 280.29 m³ across the cross-validation folds and a root mean squared error of 6517.29 m³ on the test set. No statistically significant difference was found between XGBoost and Random Forest, although both models outperformed the baseline forecasts. Feature ablation analysis showed that adding historical gas consumption features to calendar features reduced the mean root mean squared error by 81.42%. Adding meteorological features to a feature set that already included consumption history further reduced this error by 0.51%. Among the features evaluated for XGBoost, gas consumption 24 h before the target interval had the highest mean absolute SHAP value. The adaptive online conformal method produced prediction intervals that contained the observed consumption in 89.32% of cases, compared with a nominal coverage level of 90%. However, these intervals had the largest mean width among the prediction interval methods considered. The findings are limited to forecasting for a single city and one test year.

W artykule wyznaczono błędy pomiaru strumienia masy powietrza za pomocą kryzy ISA z przytarczowym pomiarem różnicy ciśnień w przypadku jej odwrotnego zainstalowania w rurociągu przepływowym. Obliczono wartości współczynnika poprawkowego zmniejszającego te błędy oraz przedstawiono wartości błędów resztkowych po wprowadzeniu tego współczynnika. W zależności od liczby Reynoldsa przedstawiono również zmiany wartości współczynnika przepływu dla kryzy zainstalowanej prawidłowo i odwrotnie.

The paper presents an adaptive air stream control algorithm for use in a bioreactor for waste composting. The system controls the streams of air supplied to the six ducts of the bireactor. Bioreactors of this type are characterized by the fact that the porosity of the charge is very heterogeneous throughout the volume. In addition, during the process, the charge is compacted and blockages for the gas flow often occur. The control algorithm should take into account the formation of blockages and attempt to clear them. In situations where unblocking is impossible, it should ensure proper distribution of air flow in other ducts despite the presence of blockages. The overriding goal of this algorithm is to ensure equal air flow streams in all channels, regardless of differences in flow resistance. Since the air circulation in bioreactors is forced by fans with constant capacity, the algorithm should adaptively determine the maximum average value of air streams that is possible to obtain under given conditions and adjust the control system to achieve it. The paper proposes a solution to meet these requirements.

Coagulation is a process during which a flocculent suspension may sediment. It is characterized by its polydisperse structure. There are three main fractions of sedimentation particles after coagulation: spherical, non-spherical and porous agglomerates. Each of the fractions sediments in a different manner, for different forces act on them, due to interactions between the particles, inhibition or entrainment of neighboring particles. The existing sedimentation models of polydisperse suspension do not consider the flocculation process, i.e. the change of one particle into another during sedimentation, resulting from their agglomeration. The presented model considers the shape of particles and flocculation, which is a new approach to the description of the mathematical process of sedimentation. The velocity of sedimentation depends on the concentration of particles of a given fraction in a specific time step. Following the time step, the heights of individual fractions are calculated. Subsequently, new concentration values of individual fractions are determined for the correspondingly reduced volume of occurrence of a given fraction in the volume analyzed, taking particle flocculation into consideration. The new concentration values obtained in this way allow to recalculate the total sedimentation rates for the next time step. Subsequent iterations allow for numerical simulation of the sedimentation process.

Progress in agriculture comes down to lowering the costs of plant production. One solution is precision farming, which saves on fertilisation, spraying and irrigation. Precision farming is mainly based on methods for measurement of coefficient of vegetation and geological conditions. For this purpose, aerial technology is used and nowadays drones are very often utilized to fields mapping. For this purpose, aerial technology is used and nowadays drones are very often used to mapping fields. On this basis, areas that require agricultural treatment are identified. The use of computer techniques improves the mapping process and the determination of vegetation coefficients. This paper presents a computer-based method for mapping of agricultural surface combined with image analysis and calculation of vegetation coefficients.

Vortex flow meters are used to measure the flow of gases and liquids. The flow meters of this type measure the frequency of vortices that arise behind an obstacle set in the path of the flowing fluid. The frequency is a function of the speed of the flowing fluid. This obstacle is called the vortex shedder bar. The advantage of this solution is that the frequency of vortices does not viscose on the rheological properties of the fluid, such as viscosity or density. As a result, the indications of the vortex flowmeter do not depend on the temperature and type of fluid. The work includes numerical and experimental studies of the effect of changing the shape of a vortex generator on the stability of vortex generation in a vortex flowmeter. The article presents a numerical analysis of the influence of selected surfaces of the vortex shedder on the parameters of the vortex flowmeter. In order to determine the influence of the shape of the vortex shedder on the type of generated vortices, simulations were carried out for various flow velocities. Numerical calculations were experimentally verified for a cylinder-shaped vortex shedder. The experimental tests consist in determining the velocity field behind the vortex shedder. For this purpose, a proprietary method of determining local liquid velocities and the visualization of local vortices were used. On the basis of the conducted research, the influence of the shape of the vortex shedder on the width of the von Karman vortex street was determined and the optimal longitudinal distance from the shedder was determined in which it is most useful to measure the frequency of the vortices. This place ensures the stability of the frequency of the generated vortices.

Flow measurements that utilize differential pressure meters are commonly applied in industry. In such conditions, gas flow is often accompanied by liquid condensation. For this reason, errors occur in the metering process that can be attributed to the fluctuations in continuous phase parameters in the flow. Furthermore, the occurrence of a dispersed phase results in flow disturbance and dynamic pressure pulsations. For the above reasons, new methods and tools are sought with the purpose of performing measurements of gas-liquid flows providing measurement results that can be considered as fairly accurate in the cases when flow involves a liquid phase form. The paper reports the results of a study involving measurement of wet gas flow using differential pressure flowmeters. The experiments were conducted for three constant mass air flow rates equal to 0.06, 0.078 and 0.086 kg/s. After stabilization of the air flow rates, water was fed into the pipe with flow rates in the range from 0.01 to 0.16 kg/s. The research involved a standard orifice and three types of slotted orifices with various slot arrangements and geometries. The analysis focused on the effect of orifice geometry on the flow metering results. On the basis of the results, it was found that the slotted orifice generates smaller differential pressure values compared to the standard orifice. The water mass fraction in the gas leads to overestimated results of measurements across the flowmeter. Regardless of the type of the orifice, is necessary to undertake a correction of the results. The paper proposes a method of gas mass flow correction. The results were compared with the common over-reading correction models available in the literature.

The paper presents a new design solution for the multi-cylinder compressed air engine, described in the PL 216801 patent. A characteristic feature of the engine is its double-piston operation with pistons working in pairs in opposition and a reciprocating movement in toroidal cylinders. The energy of compressed air was used more effectively in the described engine than in the solutions known so far. Comparing the engine built in accordance with the PL 216801 patent with the parameters of the MP165 and MP3000 engines, lower air consumption in relation to the power generated on the shaft is demonstrated. The described engine uses only one crankshaft and one straight complex shaft, which constitutes an innovative combination of pistons, while maintaining the same engine operation as in the case of two crankshafts operating with phase shift and working chamber shift. Such a solution results in a reduction in the harmful space occurring at the beginning of the power stroke to the value close to “zero”—the necessity to maintain the minimum distance between the pistons working in one cylinder when they are at their closest exists only to for the sake of collision-free operation—which is very desirable for the compressed engine operating with a shift of the working chamber. The mechanical efficiency of the engine has also been improved by guiding the pistons on the complex shaft, and the number of kinematic nodes was decreased by applying only three connecting rods supporting six pistons, which also makes it possible to improve the power and mass relation by approximately 25% in comparison with the currently known engines of similar power.