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Sapoviruses (SAVs), including several genogroups (GI to GV), are one of the causes of acute gastroenteritis (AGE). In this study, viral metagenomics revealed the presence of sapoviruses of different genogroups in stool from children with AGE. Eight different complete SAV genomes were determined, of which five belonged to GI and the other three belonged to GII, GIV and GV, respectively. Although they were highly similar to published sequences, the GIV and GV were the first complete genome sequences of these SAVs found in China. In a prevalence investigation, 19% of subjects with AGE were positive for SAVs, while none of the control group was positive. [ABSTRACT FROM AUTHOR]

The decrease of inlet charge and mismatch of air and fuel are main reasons for the decrease of engine performance at variable altitudes. Understanding coupling mechanism between two-stage turbocharging and fuel injection system is key to maximize its potential for engine power recovery at variable altitudes. This paper focused on the coupling characteristic of twin variable geometry turbocharging (Twin-VGT) and fuel injection parameters on key parameters of gas path, in-cylinder combustion, and energy flow of the diesel engine at variable altitudes. Firstly, a thermodynamic cycle model of a Twin-VGT diesel engine aiming at variable altitudes was established and validated by experimental data. Furthermore, the coupling mechanism of high-pressure variable geometry turbocharging (HVGT) and low-pressure variable geometry turbocharging (LVGT) vanes on exhaust available energy (EAE), global expansion ratio (GER) and its distribution, global boost ratio (GBR) and its distribution, isentropic efficiency of the Twin-VGT, combustion process, and energy flow of the engine were studied at different altitudes. Enthalpy drop ratio is regulated by HVGT and LVGT and the isentropic efficiency of two-stage turbine reaches to maximum when openings of HVGT and LVGT at 0.35 and 0.75, respectively, at the altitude of 5500 m. Finally, this paper investigated the coupling characteristic of turbocharging and fuel injection parameters on combustion process and engine performance, which provides the theoretical basis for collaborative controlling of the Twin-VGT and fuel injection parameters at variable altitudes. Brake thermal efficiency (BTE) is affected by exhaust temperature which is mainly controlled by HVGT openings and injection advance angle (IAA) at variable altitudes, and BTE reaches to maximum when openings of HVGT at 0.4 and IAA at −5.5°CA under fixed engine load at the altitude of 5500 m. [ABSTRACT FROM AUTHOR]

The twin variable geometry turbocharger (VGT) System, through efficient use of exhaust energy, maximizes internal combustion engine (ICE) power, reduces exhaust emissions and improves reliability. However, the internal flow characteristics of the twin-VGT system are greatly affected by the environment. To ensure that the two-stage adjustable supercharged internal combustion engine is efficient in all geographical environments and under all operating conditions, it is necessary to conduct in-depth research on the internal flow characteristics of high- and low-pressure turbines. In this paper, an experimental system of the flow characteristics of a double variable-geometry turbocharging (twin-VGT) system is designed and developed. A two-stage variable turbine flow characteristic test was carried out, focusing on the relationship between the initial rotational velocity of high variable-geometry turbocharging (HVGT) and blade opening in low variable-geometry turbocharging (LVGT). The effects of high- and low-pressure variable-geometry turbocharger (VGT) blade opening on available exhaust energy, expansion ratio distribution, blade velocity ratio, compressor power consumption and isentropic efficiency were studied. The results show that when the available energy of exhaust gas is constant, with the increase in HVGT turbine speed, when the LVGT blade opening decreases by 10%, the low-pressure turbine expansion ratio increases by about 0.23. [ABSTRACT FROM AUTHOR]

Increasingly complex air path concepts are investigated to achieve improving the power while reducing fuel consumption of diesel engines at high altitudes. One promising technology is the Twin-VGT (variable geometry turbocharger) for diesel engines. A control concept has to be developed to exploit boost potential by coordinated management of the two turbocharger stages at different altitudes. In this paper, a nonlinear model prediction control (NMPC) algorithm based on back propagation neural network (BPNN) was proposed to purpose multi-parameter control of turbocharging system at high altitudes. Optimal control sequences of NMPC were solved by improved particle swarm optimization (PSO), and boost pressure and intake flow achieved good dynamic tracking performance by collaborative control high-pressure VGT (HVGT) and low-pressure VGT (LVGT) under whole operative conditions at high altitudes. NMPC achieved better step response performance compared with PID controller at different altitudes. NMPC control error of intake flow and boost pressure are within 0.26% under steady and transient conditions, exhibiting higher control accuracy and responsiveness even under transient operating conditions at high altitudes. [ABSTRACT FROM AUTHOR]

In this study, we established a matching method for a twin variable geometry turbocharging (Twin-VGT) system under varying expansion ratios at high altitudes. In addition, we developed an equivalent thermodynamic model of a two-stage variable turbine with the effective flow areas of turbines obtained under velocity constraints for altitudes ranging from 0 to 5500 m. The effects of altitudes on the matching efficacy of a two-stage compressor under different operating conditions were evaluated. Additionally, an optimal distribution of the total boost pressure was determined to minimize the output power of the two-stage compressor during non-isothermal compression at various altitudes. Furthermore, the interplay between exhaust available energy (EAE), total expansion ratio (TER), exhaust temperature, and turbine power was investigated. Lastly, the peak efficiency of the turbocharging system was evaluated by analyzing the distribution of the TER and total enthalpy drop, aimed at optimizing EAE at different altitudes. • An optimized distribution method of total boost ratio at different altitudes. • Theoretical constraint equations for optimal distribution of available exhaust energy at different altitudes. • Matching principle for a two-stage compressor with engine under whole operating conditions at different altitudes. • Establishment of an equivalent thermodynamic model of Twin-VGT at various altitudes. [ABSTRACT FROM AUTHOR]

Abstract In this research, a comparative study of combustion characteristics, performance and emissions of a turbocharged diesel engine fueled with diesel and methanol-Fischer-Tropsch (F-T) diesel-biodiesel-diesel blends at various simulated altitudes (0 m, 3500 m and 5500 m) were conducted. The blends were composed of diesel, methanol, F-T diesel and biodiesel at volume fractions of 65%, 15.2%, 15.6% and 4.2%, respectively. Diesel was used as the baseline fuel, methanol, F-T diesel and biodiesel were used to improve the atomization characteristics, cetane number and stability of the blends, respectively. The results indicated that the cylinder pressure, pressure rise rate and heat release rate of the engine fueled with the blends were lower than those of the diesel at an altitude of 0 m, but higher at an altitude of 5500 m. Peak torque values for the test fuels both appeared at 1400 rpm near the sea level and the speeds corresponding to the peak torque values increased with altitudes. The use of the blends improved the engine power and economic performance at low-speed ranges at an altitude of 3500 m but a dramatically reduce was observed at 5500 m. Compared with the diesel, the particulate matter (2.5 (PM 2.5)) for the blends was markedly lower, while a slightly higher in NOx at various altitudes. [ABSTRACT FROM AUTHOR]

The PIV technique was applied to study the turbulent characteristics of the spays through the swirl injector and the double-jet holes injector which belong to the typical spray models called liquid-film spray and cylindrical spray respectively. The Spatial Turbulent Intensity (short for "I") and the Turbulent Integral Length Scale (short for "ILS" ) were used as parameters to analyze the turbulent characteristics of the two typical sprays. The result indicated that in the whole spray process, the distributions of I-values for the two kinds of sprays were diffuser than the distributions of speed-values, and the I-values were mainly distributed on the regions of the upside, downside and the root side of the spray flow fields. With the spray is continuing the I-value of the spray flow field, the L-value of the spray flow fields became higher and its distributions mainly concentrated in the regions of the non-front for the swirl spray and the non-front, non-central line for the double-jet spray. In order to simulate the ILS distribution more convenient, the ILS-value of every point of the spray flow field was decomposed into 4 components, Lxx, Lyx, Lxy, Lyy. Begining with the injectors spraying, at the time of 1. 5ms and 4ms, the Lxx-value of the swirl spray was higher than the double- jet spray and was also higher than the 3 other components at the same time; the local values of the Lxx reached the scales of 6mm (1.5ms) and 7mm(4ms) . At the time of 8ms, the distributions of all components for the swirl spray were diffuser than the double-jet spray; at the same time, the distributions including values and integralities of Lyx and Lxy were completely contrary. In the whole spay process, the distributions of Lyx for the two sprays were obviously lower and less integrated than the 3 other components respectively. [ABSTRACT FROM AUTHOR]

Abstract: The nanostructure, fractal dimension and size of in-cylinder soot during diesel combustion process have been investigated for a heavy-duty direct injection diesel engine, using a total cylinder sampling system followed by high-resolution transmission electron microscopy and Raman scattering spectrometry. Different structural organizations of in-cylinder soot are found depending upon the combustion phase. It is revealed that both the fringe tortuosity and separation distance decrease as combustion proceeds, while the mean fringe length increases distinctly from 1.00 to 2.13nm, indicating the soot evolution toward a more graphitic structure during the combustion process. The fractal dimensions of aggregates are in a range of 1.20–1.74 at various crank angles under the applied engine operating conditions. As temperature and pressure increase, the fractal dimension decreases significantly to a minimum at the early diffusion combustion stage. The soot particles become more compact again as the fractal dimension increases during the subsequent combustion period. Primary particle sizes start small, go through a maximum in the early diffusion combustion phase and decline again as combustion proceeds. [Copyright &y& Elsevier]

Abstract: The diesel soot was extracted from the chamber of a running diesel engine using a total cylinder sampling system. A structural description and size distribution of the soot spherules were performed by means of high-resolution transmission electron microscopy (HRTEM). HRTEM image analysis was carried out to achieve semi-quantitative information about the soot organization. Different nanostructures were found in dependence upon the engine test conditions. A better organization of the graphitic layers occurred for the in-cylinder soot as the expansion stroke developed. The oxygen concentrations at sampling angles and the cylinder pressure were measured. The oxidation rates of the in-cylinder soot during the late combustion phase were calculated according to the differences of spherules size distributions between two consecutive sampling angles. The soot reactivity in dependence on the nanostructure was shown after deducting the effect of oxygen concentration and temperature. The increase of resistance toward oxidation was associated to the increase of the structural order for the in-cylinder soot. The results are a useful database for testing the structure–property relationship between the nanostructure and the reactivity of the in-cylinder diesel soot. [ABSTRACT FROM AUTHOR]