The fluidity length of aluminum alloy is key parameter in mold-filling process. Generally it impacts the final quality of the cast products. In the paper we introduce our mathematical model for estimating the fluidity length of the particular alloy under high pressure die casting conditions. We tested our model against the spiral test to compare results and verified the feasibility of this particular mathematical model.

Heating flame furnaces are the main type of furnaces used for heating and heat treatment of metal products in metallurgy and mechanical engineering. In the working chamber of a modern heating furnace, there should be neither high-temperature nor stagnation zones. One of the methods used to provide such combustion conditions is the application of distributed (volumetric) combustion. Owing to this method, heating quality is ensured by creating a uniform temperature field and equivalent heat exchange conditions, regardless of the placement of the charge in the working chamber of the furnace. In this work, we numerically study the volumetric combustion and influences of small- and large-scale recirculation ratios of furnace gases, the influence of temperature fluctuation on the regenerator nozzle, and the working parameters at the starting phase and reverse.

Nitrogen oxides (NO_x) from combustion contribute significantly to atmospheric pollution. An experimental setup was employed to investigate the application of three primary denitrification methods, i.e., reburning (staged combustion), overfiring air (OFA), and flue-gas recirculation (FGR), individually and in combination, combusting natural gas (NG) and propane–butane gas (PBG). Fuel heat inputs of 16 and 18 kW and air excess coefficients of 1.1 and 1.2, respectively, were tested. The highest individual denitrification efficiency of up to 74% was obtained for FGR, followed by reburning and OFA. A denitrification efficiency between 8.9% (reburning + OFA) and 72% (reburning + OFA + FGR) with NG combustion was observed. Using a 20% FGR rate yielded denitrification efficiency of 74% for NG and 65% for PBG and also led to a significant decrease in carbon monoxide (CO) emissions, so this can be recommended as the most efficient denitrification and de-CO method in small-scale furnaces. Reburning alone led to a sharp, more than 12-fold increase in CO emissions compared to the amount without any other method application. The presented results and the difference between our experimental data and the literature data acquired in some other studies indicate the need for further research.

The paper deals with the stabilization of low damped astatic systems. They show a low value of a relative damping and consequently a high resonance rise of amplitude frequency response. If astatism occurs in an automatic control system, the situation becomes complicated due to the exhaustion of a phase safety of astatic element. In order to achieve the stabilization, a filter with rejections has been designed. The filter is characterized by rapid rejections of logarithmic frequency characteristics that eliminate resonance rise of a low damped astatic system. A functional model of a discrete filter was created to attest the properties of the filter with a continuous low damped astatic system. Experiments have proved the suitability of the filter application. The method of the filter utilization, the stability of the low damped astatic system as well as the stability assessment by the operator W will be described in the paper.

In recent years, extensive research has been dedicated to enhancing energy efficiency and promoting environmental sustainability in heating and cooling systems. Among the promising solutions, phase change materials (PCM) technology stands out as a key area of exploration. This study focuses on improving the thermal performance of PCM–water hybrid tanks by investigating methods to enhance thermal conductivity and heat transfer. Through experimental testing using techniques such as copper matrices, steel twisted matrices, and copper spirals, this study demonstrates significant improvements in thermal conductivity, particularly with the use of copper matrices. The integration of a copper matrix placed in the PCM reservoir increased the heat transfer coefficient and thermal conductivity of the PCM, and thus, the total phase transformation time for solidification was reduced by 79.19% and for melting by 54.7%. Our experimental results demonstrate that the integration of a copper matrix can increase latent heat transfer from 55,677.6 J up to 125,274.6 J, marking a 125% enhancement over the experiment with pure PCM. Additionally, comparisons of the energy storage potentials for different PCMs underscore the benefits of integrating PCMs into hybrid storage tanks. These findings highlight the immense potential of PCM technology to increase energy storage efficiency in heating and cooling applications.

The presented paper deals with the design of a mathematical model of a rejection filter for the drives stabilization applied to pressure die casting processes. The rejection filter allows the stabilization of electrohydraulic servo drives making use of periodically repeated zero transfer functions while taking advantage of the essence of a parallel joint of the proportional unit and a time delay unit. Consequently, the model of the adaptive rejection filter algorithm with a higher form of electrohydraulic servo drives has been mathematically elaborated. The paper comprises the algorithm description for the models implementation in the process of a servo drive control, which to a sufficiently greater extent can respond to the changes in technological parameters of pressure die casting than a conventional drive system. The introduction of a position feedback or a high-speed feedback allows the elimination of excessive porosity formation. By Introducing additional feedbacks, it is possible to affect the speed of a piston movement in the range of a low pressing speed depending on other technological parameters, for example, a melt temperature in the chamber.