[en] Highlights: • Ultra-expansion cycle SI engine is investigated. • An improvement of 9–26% in BSFC at most frequently operated conditions is obtained. • At high and medium loads, BSFC improvement is attributed to the increased combustion efficiency and reduced exhaust energy. • At low loads, reduction in pumping loss and exhaust energy is the primary contributors to BSFC improvement. • Technical challenge in practical application of this type of engine is discussed. - Abstract: A four-cylinder, intake boosted, port fuel injection (PFI), spark-ignition (SI) engine is modified to a three-cylinder engine with the outer two cylinders working in the conventional four stroke cycle and with the inner cylinder working only with the expansion and exhausting strokes. After calibration and validation of the engine cycle simulation models using the experimental data in the original engine, the performance of the three-cylinder engine with the ultra-expansion cycle is numerically studied. Compared to the original engine, the fuel consumptions under the most-frequently operated conditions are improved by 9–26% and the low fuel consumption area on the operating map are drastically enlarged for the ultra-expansion cycle engine with the proper design. Nonetheless, a higher intake boosting is needed for the ultra-expansion cycle engine to circumvent the significant drop in the wide-open-throttle (WOT) performance, and compression ratio of the combustion cylinder must be reduced to avoid knocking combustion. Despite of the reduced compression ratio, however, the total expansion ratio is increased to 13.8 with the extra expansion of the working gas in the inner cylinder. Compared to the conventional engine, the theoretical thermal efficiency is therefore increased by up to above 4.0% with the ultra-expansion cycle over the most load range. The energy balance analysis shows that the increased combustion efficiency, reduced exhaust energy and the extra expansion work in the inner cylinder are the primary contributions to improving the fuel conversion efficiency at the middle and high loads. At the low load, reductions in the pumping loss and exhaust energy are the main causes of the reduced fuel consumption, while the contribution of the extra expansion work in the inner cylinder becomes small

[en] Using the methods of dynamic simulation and closed circuit of primary and secondary systems, the transient of house load from 100% FP, which is important transient in the normal operation of nuclear power plant, is analyzed with reference to Daya Bay nuclear power plant. Some factors to influence the progress of transient are pointed out

[en] The author analysis the transient of house load operation for Ling'ao Nuclear Power Plant by using the methods of dynamic simulation and closed loops of primary and secondary system. The transient of house load operation from 100% FP is the most severe that can occur on the unit in normal operation because it causes immediately shedding of 95% of turbine load and requires the unit to operate steadily at reduced power. The results show that the transient can be successful both at beginning of core life and manual house load operation. However, more attentions must be paid to automatic house load operation caused by grid fault at toward end of core life because the success of the transient could be threatened by the actuation of the protection of high flux and high flux rate

[en] Highlights: • We designed a PV/T system running in the mode of natural circulation. • We established a simulation model of the system with MATLAB simulation software. • The experimental data was compared with simulation results. • The performance of the system was researched. - Abstract: Because of the high resistance caused by photovoltaic-thermal (PV/T) systems, the improved electrical energy due to fluid’s cooling is much less than energy consumption of pump. To avoid this problem, in this paper, a natural circulation tube plate PV/T system is designed and built in photovoltaic solar simulation laboratory of Tianjin Chengjian University. The circulation velocities, electrical efficiencies, thermal efficiencies, overall efficiencies, and primary energy economic ratios are tested and analyzed under different radiation intensities. The result shows that the operation of the natural circulation PV/T system has hysteresis, and it requires longer time to keep the system operating with higher and stable performance when radiation intensity is at low levels. A mathematical model of heat transfer for this PV/T system has been established and solved using the MATLAB, and the numerical results have been validated by experimental data. The overall efficiency of the system under the pattern of natural circulation is also calculated when used in hot summer and warm winter areas. The generated electricity is about 1281.5 MJ/year; the heat collection is about 4639.6 MJ; and the annual integrative efficiency is 60%.

[en] A microcomputer code MACONP/MOD1.0 for PWR nuclear power plant high-speed safety analysis is developed successfully. The mathematical model of this code mainly includes reactor core heat transfer model, point-reactor kinetic model, pressurizer model, U-tube steam generator model as well as flow field models and fluid property equations related to the above system models. The code has friendly interface and is very convenient for users. Several transients of Qinshan Nuclear Power Plant are analyzed by the code, and results agree well with ones of the RELAP5/MOD2 code

[en] TARTS, a pressurizer water reactor (PWR) nuclear power plant (NPP) transient process adjustment real-time simulation code, is successfully developed. This code combines the reactor control system analysis and design with the NPP transient analysis organically. It has applications in the reactor control system dynamic behavior analysis, the reactor control system design and real-time simulation of the NPP transient process adjustment. this code running on microcomputers and under WINDOWS operation system has friendly interface and is very convenient for users. Several transients of Qinshan Nuclear Power Plant are simulated by the code, and satisfactory results are obtained

[en] In the welding structure of nuclear power equipment, J-type welding is a typical welding connection form, such as the control rod drive mechanism (CRDM) seat, instrument tube and exhaust pipe connected with the top cover of reactor pressure vessel, which are connected by J-type welding on the inner surface of the upper head. Corrosion cracks and fatigue cracks are easy to occur, so it is particularly important to study the integrity of such structures. In fact, there are many influencing factors in the process of J-type welding. At present, it is difficult to obtain complete distribution of welding residual stress by means of damage or non-destructive testing. In this paper, the finite element method is used to simulate the welding process of J-type welding of typical dissimilar metals. The three-dimensional structure model and sequential coupling method are used to simulate the temperature field in the welding process, and then the temperature field is used as input condition to respond to the whole welding process. The force and deformation are simulated. Finally, the residual stress and deformation after J-type welding are analyzed, the dangerous position is found and the improvement suggestions are put forward. In this paper, J-type welding involves five kinds of materials and their thermophysical and thermoelastic-plastic parameters. The analysis software is ANSYS. The results of this paper have practical guiding significance for the design of J-type welding structure, the optimization of welding parameters and the control of residual stress and deformation after welding, and lay a foundation for the safety and reliability analysis of welding structure. (authors)

[en] In this paper, the (G'/G)-expansion method is extended to solve fractional partial differential equations in the sense of modified Riemann—Liouville derivative. Based on a nonlinear fractional complex transformation, a certain fractional partial differential equation can be turned into another ordinary differential equation of integer order. For illustrating the validity of this method, we apply it to the space-time fractional generalized Hirota—Satsuma coupled KdV equations and the time-fractional fifth-order Sawada—Kotera equation. As a result, some new exact solutions for them are successfully established.

[en] Background: A flaw is discovered by ultrasonic test at reactor pressure vessel during the service. Purpose: In order to insure the structural integrity of RPV, it is necessary to perform the fracture analysis for RPV flaw. Methods: According to ASME rule, fracture analysis is performed, which the flaw is assumed as a circumferential surface crack and crack depth is 10.1 mm. The analysis work contains the calculation of fatigue crack growth and the assessment of stress intensity factor under several category conditions. The loads are the temperature fluctuation, pressure and weld residual stress. The concerned category conditions include normal and upset conditions, emergency conditions, and faulted conditions. Results: The analysis results show that normal and upset conditions transient loading has little effect on the fatigue crack growth of low inner surface crack. The fatigue crack growth is about 0.228 mm at the end of 40 years service life. Conclusions: The stress intensity factor results of all conditions satisfy the requirement of ASME Rule. The RPV with flaw can continue service without repair. (author)

[en] Atmospheric pressure glow discharges generated between parallel-plate electrodes in helium have been characterized using temporally resolved emission spectra. The variation of typical spectral lines over time has been analyzed. In helium with a low concentration of N₂, the emission of He at 706.5 nm is dominant and appears 500 ns earlier than N₂⁺ first negative bands, indicating low reaction rates of Penning ionization and charge transfer in the initial stage. During the decay, it is the Penning ionization caused by He metastables with a long lifetime rather than the charge transfer reaction that leads to the long decay of N₂⁺ emissions. When helium contains a higher concentration of N₂ molecules, the N₂⁺ first negative bands become the most intense, and emissions from He, N₂⁺, and O exhibit similar behavior as they increase. The emissions last for a shorter time under such conditions because of rapid consumption of He metastables and He₂⁺.