The efficiency problem of hydraulic pump units with advanced double structures with constant pressure regulators with different linear characteristics in the case of work in an open supply system is presented in the paper. The main parts of the hydraulic power pack structure and pressure controller functions are described. The equation is given for the calculation of energy losses in particular pumps and the whole multi-pump power pack unit. The difference between the efficiency of particular pumps and the hydraulic pump unit was discussed.

Constant pressure variable flow reciprocating axial pumps (CPAP) are used in various applications, where a constant output pressure is maintained when the flow rate changes. When the hydraulic system is at rated pressure or less, the swash plate has maximum tilt, and the pump delivers maximum flow. The swash plate comes into this position thanks to the action of a reactive piston in which there are two springs. However, when the pressure rises above the nominal pressure value, the piston of the hydraulic pressure transducer (HPT) distributes the fluid under pressure to the hydraulic cylinder (HC), which causes a decrease in the tilt angle of the swash plate and a decrease in flow. The CPAP was selected as a component of the hydraulic system of the aircraft for the experimental tests in this paper. The experimental tests covered the structural and working parameters of the pump and analyzed their performance, efficiency and reliability. Experimental tests of structural and operating parameters of the CPAP were carried out in the Laboratory for Hydraulics and Pneumatics “PPT-Namenska” Trstenik on the hydraulic system, which simulated the real conditions prevailing in the hydraulic system of the aircraft. A system was used for data acquisition and recording of pump characteristics, which were obtained during experimental testing. The results of the measurement and testing of the structural parameters of the CPAP are shown in tabular form, and the experimental tests of static characteristics and dynamic behavior are shown diagrammatically.

The modern economy rests on industrial development and production with the application of new technologies, knowledge and achievements in technique, technology, economy, ecology, organization, management, informatics and other branches of science and profession. Processes are being innovated in order to achieve products and services of higher quality and performance, in accordance with increasingly strict market requirements. Today, KETs (Key Enabling Technologies) are increasingly being used, which represent a narrower set ofsix KETs that enable innovations: micro and nanoelectronics, nanotechnology, industrial biotechnology, advanced materials, photonics and advanced production technologies. Ideas for sustainable hotels are in line with the application of environmentally friendly and automated processes, products and services, which with the application of artificial intelligence (AI) can become green (or even greener). The world's best brands (hotels) have become green thanks to the solutions created by the application of VI, with the launch of many green initiatives (ie. smart showers, solar energy installations, waste reduction and diversion, energy and water consumption savings, etc.). A full understanding of sustainability is important for the hotel industry. The best sustainable hotels are businesses that significantly reduce their impact on the environment through best green practices in maintenance, services, logistics, products and supplies. A hotel that is serious about sustainability must expect large capital expenditures, such as modernization (ie replacement) of HVAC systems (ventilation and air conditioning systems, with the extension to mechanical cleaning and dry cleaning). When hotels go green, they do much less harm to the environment, reduce costs and win the goodwill of guests. Sustainability in the business world is key to achieving supplier growth and customer satisfaction. Consumers are increasingly looking for green businesses and paying more for environmentally friendly products and services. One in three consumers prefers sustainable brands, and the travel industry is taking note. The research results in this paper are mainly presented according to the dominant program criteria and variables, at the level of ecology or the application of artificial intelligence at the level of products and systems.

As part of the research carried out in the field of processing systems and the production process of oil-hydraulic cylinders of large dimensions and power, the specifics of fluid power transmission, in the functioning of hydropower facilities, were analyzed. The research also includes the optimization of the physical–mathematical model of non-stationary processes, which take place inside the chamber of a large hydrocylinder. In parallel with the definition of the optimization model, the work parameters that affect the process of fluid flow and piston movement were determined. The operating and technological construction parameters of the hydraulic cylinder, which most significantly affect the operation of the hydraulic cylinder, were defined, and the observed parameters were optimized, based on which a prototype with improved characteristics compared to existing solutions was realized.

The overall efficiency and energy consumption problem in hydraulic power pack units with and without an additional pre-charging system was analyzed in this paper. A theoretical mathematical model was developed for calculating energy losses in both pump unit structures. To verify the theoretical relationships, a laboratory test stand was built, upon which the results of calculating the overall efficiency were compared with the results of the laboratory tests. Universal diagrams of the overall efficiency dependence as a function of pressure load and geometric adjustment of the main pump’s working volume were created for the case of a particular hydraulic pump unit without and with a pre-charging system. Based on this, discussions were carried out on whether and the way in which the additionally pre-charging system affects the parameters of the overall efficiency characteristics of the researched pump unit. Additionally, the dependence of the optimal pressure load and the maximum overall efficiency of the pump unit on the geometric adjustment of the main pump’s working volume was analyzed. It was shown that the pre-charging system affects the increase in the optimal pressure load at which the most favorable operating conditions, in terms of energy consumption, are obtained for the researched hydraulic pump unit.