Development of mathematical models and optimization of operation modes of the oil heating station of main oil pipelines under conditions of fuzzy initial information

The relevance of the study is substantiated by the fact that when managing the processes of oil transportation through main pipelines, it becomes necessary to determine and select the optimal operating modes of the oil pipeline units, taking into account the fuzziness of some part of the initial information. In this regard, solving the problem of multi-criteria selection of effective operating modes for an oil heating station for a hot oil pipeline system, which is often described in a fuzzy environment, based on the apparatus of fuzzy set theories, is an urgent scientific and practical problem. A method for the synthesis of models in the conditions of fuzzy output parameters of the object has been developed, with the help of which fuzzy models of the investigated oil heating station of the main oil pipeline have been built. Based on the modification and combination of various optimality principles, mathematical formulations of the problem of multi-criteria selection of effective operating modes for an oil heating station in a fuzzy environment are obtained. By modifying and adapting the principles of guaranteed results and equality in a fuzzy environment, a heuristic method has been developed for solving the formulated problem of selecting object's operation modes using the initial fuzzy information. The proposed heuristic method for multi-criteria selection in a fuzzy environment is based on the use of the experience and knowledge of the decision-maker. The proposed approach is implemented in the formulation and solution of the problem of multi-criteria selection of operating modes of the oil heating station in Atyrau of the Uzen-Atyrau-Samara main oil pipeline. As a result of the application of the proposed method, an improvement in the degree of fulfillment of a fuzzy restriction on environmental impact was achieved by 2 %, as well as the optimal values of the operating parameters of the object were improved: the temperature was reduced by 1.85 % (5.67 K), pressure – by 0.04 % (kPa) and fuel consumption – by 2.9 % (0.0002 kg/s). The obtained results have confirmed the effectiveness of the proposed approach to solving the assigned tasks.

Balancing of Coupled Piezoelectric NEMS Resonators

Micro and Nano Electro Mechanical systems (M/NEMS) have a lot of potential to be used for sensing in different schemes and operation modes. We focus here on the use of coupled resonators for sensing and address the major limitation that these systems face, which stems from a compromise between dynamic range and responsivity. When the system becomes unbalanced, the responsivity drops. To solve this issue, we propose the use of piezoelectric-based stress tuning of the stiffness of the resonators in order to rebalance the system of resonators. With this approach we expect to be able to extend the dynamic range of such systems by some orders of magnitude.

Effects of Reversed Shock Waves on Operation Mode in H2/O2 Rotating Detonation Chambers

Operation modes are an important topic in the research of Rotating Detonation Chamber (RDC) as it can affect the stability of RDC. However, they have not been discussed in detail due to the limitation of measurement means in experiments. The aim of this research is to investigate the mechanism of different operation modes by numerical simulation. In this paper, a numerical simulation for RDCs with separate injectors is carried out. Different operation modes and mode switching are analyzed. There is a series of reversed shock waves in the flow field. It was found that they have great effects on operation mode and mode switching in RDCs. A reversed shock wave can transit into a detonation wave after passing through isolated fresh gas region where fresh gas and burnt gas distribute alternatively. This shock-to-detonation transition (SDT) phenomenon will influence the ignition process, contra-rotating waves mode and mode switching in RDCs. SDT makes the number of detonation wave increases, resulting in multi-wave mode with one ignition. Moreover, quenching of detonation waves after collision and SDT after passing through isolated fresh gas region are the mechanism of contra-rotating waves mode in RDCs with separate injectors. In addition, when the inlet total temperature increases, a shock wave is easier to transit into a detonation wave. The distance that a shock wave travels before SDT decreases when temperature increases. This will result in mode switching. Therefore, SDT determines that there is a lower bound of detonation wave number.

Free Switching Control Strategy for Multi-Operation Modes of Multi-Port Energy Router in Distribution Area

For the distribution area with a high penetration rate of new energy, the traditional power supply system has some problems, such as a single form of power supply and low utilization of new energy. Because the multi-port energy router can realize the interconnection and complementation of multiple energy forms, it has become the key piece of equipment in the hybrid AC/DC distribution area. Nevertheless, restricted by the existing control strategy, the performance of the energy router in complex operation mode switching and coordinated control still needs to be further improved. To address this issue, the free switching control strategy is proposed in this paper. Firstly, the topology and model of the multi-port energy router are designed and established. Secondly, the operation mode of the system is analyzed, and the control strategy of each port is designed. Then, a reference power calculation method suitable for multi-mode operation is derived. Based on this, the control strategy does not need to be changed when operation modes are switched. Furthermore, the extended state observer is introduced to track and compensate for the new energy disturbance, which can improve the power quality of the system. Finally, the simulation and experimental results show that the proposed control strategy of the multi-port energy router can realize flexible and controllable power transmission among various modules in the distribution area and the free switching of multi-operation modes without changing the control strategy.

Sequential generation of self-starting diverse operations in all-fiber laser based on thulium-doped fiber saturable absorber

Self-starting Q-switching, Q-switched mode-locking and mode-locking operation modes are achieved sequentially in an all-fiber erbium-doped fiber laser with thulium-doped fiber saturable absorber for the first time. The central wavelengths of Q-switching, Q-switched mode-locking and mode-locking operation modes are 1569.7 nm, 1570.9 nm, and 1572 nm, respectively. The mode-locking operation of the proposed fiber laser generates stable dark soliton with a repetition rate of 0.99 MHz and signal-to-noise ratio of 65 dB. The results validate the capability of generating soliton pulse by doped fiber saturable absorber. Furthermore, the proposed fiber laser is beneficial to the applications of optical communication and signal processing system.