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[en] The hydraulic free-piston engine integrates the internal combustion engine with a hydraulic pump. The piston of an HFPE is not connected to the crankshaft and the piston movement is determined by the forces that act upon it. These features optimize combustion and make higher power density and efficiency increase. In this paper, a detailed thermodynamic and energy saving analysis is performed to demonstrate the fundamental efficiency advantage of an HFPE. The thermodynamic results show that the combustion process can be optimized to an ideal engine cycle. The experimental results show that the HFPE combustion process is a nearly constant-volume process; the efficiency is approximately 50%; the piston displacement and velocity curves for a cycle are the same at any frequency, even at a 1.25 Hz. The maximum velocities are of the same value at high or low frequencies. Similarly, pump output flow is not influenced by frequency. The independent cyclic characteristics of HFPE determine that it should work in higher frequencies when the vehicle runs in Japanese 10–15 road conditions. It indicates that a higher working frequency will lead to the starting frequency of HFPE, and a lower frequency will decrease the pressurized pressure of the hydraulic accumulator. - Highlights: • The thermodynamic and energy saving benefits of the HFPEs was investigated. • The approach of combustion optimization was obtained by adjusting the injection timing and compression ratio. • The high efficiency area of HFPE was given as a function of injection timing and compression pressure. • The maximum efficiency of HFPE of 50% was obtained from the prototype. • The method of energy saving with adjusting the piston frequency was examined.
[en] Highlights: • A hydraulic electronic unit injector in HFPE is developed and the test bench is established. • Effect of drive pressure on injection delay of hydraulic electronic unit injector are investigated. • Cycle fuel injection quantity is tested online and off-line engine operation. • The BDC control results in HFPE based on feed-forward compensation are acceptable. • The energy flow in HFPE is analyzed and the hydraulic output energy is optimized. - Abstract: The fuel injection system in two stroke engine is very important, therefore the hydraulic electronic unit injector system is developed and the injection characteristics of hydraulic electronic unit injector are investigated. Firstly the HFPE and the hydraulic electronic unit injector working principle are analyzed, and then PID control strategy is built by engine demand. In order to validate the feasibility of hydraulic electronic unit injector, the prototype test bench is established. The specific measurement principle is presented. Further the injection characteristics, such as the effect of injection pressure on injection delay and the effect of engine frequency on injection delay, are analyzed. In order to optimize the engine stability performance, the BDC control based on fuel injection control is investigated. The load control based on fuel injection is also discussed and the BDC feedforward control with the load variation is investigated. Experiment results of stead engine operation shows that the hydraulic electronic unit injector system based on PID control can be satisfied with the engine operation demand. In addition, cycle fuel injection quantity is tested online and off-line engine operation. It is obvious that the fuel injection quantity is affected by the hydraulic pressure. The fuel injection quantity variation can be improved with decreasing the fluctuation of drive pressure or adopting more suitable oil common rail instead of connected with exhaust valve hydraulic drive oil-way. The energy flow in HFPE is analyzed and the hydraulic output energy can be optimized by selecting suitable hydraulic valves parameters. The fuel injection quantity should be designed by the energy balance and the stable operation requirement in spite of the higher thermal efficiency.
[en] The cold start characteristic of hydraulic free piston diesel engine may affect its stable operation. Therefore the specific cold start characteristics, such as BDC or TDC positions, pressure in-cylinder, heat release rate, should be investigated in detail. These parameters fluctuate in some regularity in the cod start process. With the development of the free piston engine prototype and the establishment of test bench, the results are obtained. For the dynamic results, the fluctuation range of TDC and BDC positions is 8 mm and decreases with time. The thermodynamic results show that the combustion process is not stable and the pressure in-cylinder fluctuates largely in the cold start process. In addition, the combustion is rapid and knock happens inevitably. In order to investigate the reasons, a CFD model is established for temperature analysis in-cylinder and heat transfer conditions. It is found that higher start wall temperature will lead to more uniform temperature distribution. The delay period may decreases and heat release will move forward. This reason is analyzed by thermodynamic derivation based on the first law of thermodynamics. Finally, the improvement suggestions of cold start strategy are proposed. - Highlights: • The cold start behaviors of HFPE are investigated in detail. • CFD method is used for simulating temperature distribution in start process. • Thermodynamic derivation uncovers the compression temperature distribution. • The improvement suggestions of cold start strategy are proposed.
[en] 2-Hydroxy-1-naphthaldehyde oxime (receptor 1) serves as a selective chemosensor for cyanide anion (CN"−). In the presence of CN"−, an enhanced fluorescent intensity and red-shift were observed. The observed complexation between receptor 1 and CN"− may cause by a hydrogen bonding interaction between the OH group of receptor 1 and CN"−. - Highlights: • 2-Hydroxy-1-naphthaldehyde oxime serves as a selective chemosensor for CN"−. • In the presence of CN"−, an enhanced fluorescent and red-shift were observed
[en] In relativistic mass-asymmetric nucleus-nucleus collisions, the azimuthal distribution of pions is anisotropic because of the shadowing effect of the heavy target spectator, consequently, correlation independent of Bose-Einstein statistics is observed among the pions. The spatial parameter of the source extracted from pions interferometry is less than the true value due to this correlation. The influence of the preferential emission of pions on the analyzed results of pion interferometry can be corrected by rotating the events so that their estimated reaction planes are parallel to each other before construction the background
[en] In the present work Ce3+-doped germanate glasses containing Gd2O3 and BaO or La2O3 were developed. The UV and VIS transmission spectra of these glasses were measured before and after irradiation at doses ranging between 3 and 277 Gy. The radiation induced absorption coefficient μ was calculated on the basis of the measured transmission spectra. From these results the cerium ions doping turns out to be effective in improving the radiation hardness of glasses with respect to their undoped matrices
[en] CO adsorption on small Aun (n = 1 — 7) clusters which are supported by a partially reduced rutile TiO2(110) surface has been investigated by the first-principles method. The low coordinated sites of Au clusters are favorable for CO adsorption. CO—Aun—TiO2 system displays surface magnetism. There is a strong interaction between the adsorbed CO molecule and the supported Au clusters. (condensed matter: structural, mechanical, and thermal properties)
[en] Graphical abstract: A series of novel β-Bi2O3-NiO/Ni composites were synthesized via one-step solution combustion method. The coupling of β-Bi2O3 with NiO/Ni promoted the catalytic activity under visible light irradiation, which can be ascribed to the increase of separation efficiency of electrons and holes over β-Bi2O3-NiO and the existence of metallic Ni. - Highlights: • β-Bi2O3-NiO/Ni composites were prepared via one-step solution combustion method. • The materials had excellent visible light absorption ability and narrow band gaps. • Ni may show a plasmonic property and increase the visible light absorption. • The photocatalytic mechanism of the β-Bi2O3-NiO/Ni composites was proposed. • The as-obtained samples could be recycled easily by magnetic separation. - Abstract: A series of novel β-Bi2O3-NiO/Ni heterojunctions were synthesized via one-step solution combustion method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis spectroscopy and terephthalic acid (TA) fluorescence. The obtained NiO/Ni samples showed visible light absorbance ability and had narrow band gap of ca. 2.20 eV. The coupling of β-Bi2O3 with NiO/Ni promoted the visible light catalytic performance. The enhanced activity could be ascribed to the increase of separation efficiency of electrons and holes and the existence of metallic Ni, which might show a plasmonic effect and could increase the light absorption ability. The scavengers’ tests demonstrated that hydroxyl radical and holes species played a major role for the methyl orange degradation. Furthermore, the as-obtained samples had magnetic properties and could be recycled easily by magnetic separation from the reaction system. Finally, the mechanism of the photocatalytic reaction over β-Bi2O3-NiO/Ni composites was proposed
[en] According to the semi-classical theory, we study the photodetachment microscopy of H− in the electric field near a metal surface. During the photodetachment, the electron is photo-detached by a laser and the electron is drawn toward a position-sensitive detector. The electron flux distribution is measured as a function of position. Two classical paths lead the ion to any point in the classically allowed region on the detector, and waves traveling along these paths produce an interference pattern. If the metal surface perpendicular to the electric field is added, we find that the interference pattern is related not only to the electron energy and the electric-field strength, but also to the ion-surface distance. In addition, the laser polarization also has a great influence on the electron flux distribution. We present calculations predicting the interference pattern that may be seen in experiment. We hope that our study can provide a new understanding of the electron flux distribution of negative ions in an external field and surface, and can guide future experimental research on negative ion photo-detachment microscopy. (atomic and molecular physics)
[en] In the framework of a modified Fisher model, the ratio of the symmetry-energy coefficient to temperature (asym/T) is extracted from the fragment produced in the 124,136Xe induced reactions using the isobaric yield ratio methods based on different approximations. It is found that for nuclei with the same neutron excess (I≡N-Z) increases when the mass of the fragment increases, while for isobar asym/T decreases when I increases. It is also found that the extracted asym/T of the nucleus has very little dependence on the n/p ratio of the projectile, target, and the incident energies in the reaction. (orig.)