A conventional asymmetric twin-scroll turbine with wastegate is capable of effectively tackling down the contradiction between fuel economy degradation and low nitrogen oxide emissions. However, as the engine speed has been rising at middle- and high-speed ranges, the pressure of small scroll inlet will be increasingly higher as compared with the intake pressure, thereby worsening fuel economy. In this study, a novel turbocharging technology of asymmetric twin-scroll turbine with a balance valve was first analyzed to more effectively balance the engine fuel economy and emission. The experiments on turbine test rig and engine performance were performed to explore the effects of balance valve on turbine performance, asymmetric ratio, exhaust gas recirculation rate, as well as engine performance. As the balance valve open degree was elevated, the turbine flow parameter was being extended, while the turbine efficiency was enhanced. Moreover, a lower asymmetric ratio could lead to a broader flow parameter range between that of partial admission and equal admission, thereby resulting in a broader regulating range of exhaust gas recirculation rate. In contrast with the asymmetric twin-scroll turbine with wastegate, the turbine running efficiency of asymmetric twin-scroll turbine with balance valve was enhanced by nearly 2%–11% at middle and high engine speed ranges, while the fuel economy was improved by nearly 1.5%–8%.
Ionic liquids (ILs), as one of the most concerned functional materials in recent decades, have opened up active perspectives for electrocatalysis. In catalyst preparation, ILs act as characteristic active components besides media and templates. Compared with catalysts obtained using ordinary reagents, IL-derived catalysts have a special structure and catalytic performance due to the influence of IL’s special physicochemical properties and structures. This review mainly describes the use of ILs as modifiers and reaction reagents to prepare electrocatalysts for water splitting. The designability of ILs provides opportunities for the ingenious composition of cations or anions. ILs containing heteroatoms (N, O, S, P, etc.) and transition metal anion (FeCl4−, NiCl3−, etc.) can be used to directly prepare metal phosphides, sulfides, carbides and nitrides, and so forth. The special physicochemical properties and supramolecular structures of ILs can provide growth conditions for catalysts that are different from the normal media environment, inducing special structure and high performance. ILs as heteroatom sources are safe, green and easy to operate compared with traditional heteroatom sources. The strategy for using ILs as reagents is expected to realize 100% atomic transformation of reactants, in line with the concept of green chemistry. This review reflects the discovered work with the best findings from the literature. It will offer readers a deeper understanding on the development of IL-derived electrocatalysts and inspire them to ingeniously design high-performance electrocatalysts for water splitting.
In this paper, a novel one-dimensional matching method of an asymmetric twin-scroll turbine (ATST) with a small scroll bypass wastegate is initially presented for energy improvement. The developed method presents further insights into efficiency prediction of the ATST and the small scroll exhaust bypass in the matching process of model characterization. The efficiency of the small and large scroll turbines was approximately assessed with two times flow parameters of the small and large scroll turbines, respectively, as well as according to turbine efficiency prediction curves. Subsequently, given the matching results of a 9-L engine, a targeted ATST was developed; its effectiveness was verified by computational fluid dynamics (CFD) and the performance tests of a turbine and an engine. As revealed from the results, the prediction efficiency of the ATST well complies with that of the numerical calculation and performance tests of turbines and engines. Compared with the common large scroll exhaust bypass wastegate, the small one exhibits better engine performance and can save nearly 0.5–1.5% fuel consumption at middle and high engine speeds. Moreover, the reasons of which were explored for better understanding of the mechanism accordingly.
As green, safe, and cheap solvents, deep eutectic solvents (DESs) provide tremendous opportunities to open up attractive perspectives for electrocatalysis. In this review, the achievement of DESs in the preparation of catalysts for electrolytic water splitting is described in detail according to their roles combined with our own work. DESs are generally employed as green media, templates, and electrolytes. A large number of hydrogen bonds in DESs result in supramolecular structures which have the ability to shape the morphologies of nanomaterials and then tune their performance. DESs can also serve as reactive reagents of metal electrocatalysts through directly participating in synthesis. Compared with conventional heteroatom sources, they have the advantages of high safety and designability. The “all-in-one” transformation strategy is expected to realize 100% atomic transformation of reactants. The aim of this review is to offer readers a deeper understanding on preparing DES-mediated electrocatalysts with higher performance for water splitting.
Maintaining required performance and rated power output of proton exchange membrane fuel cells while reducing fuel consumption demands and improving efficiencies at the largest parasitic work loss contributor, namely the air compressor. In this paper, we built a high-efficiency one-dimensional match model of centrifugal compressor for proton exchange membrane fuel cells first, which was based on the fuel cell air supply system and the optimal trim factor. And then a variable map width enhancement slot design adjusted by a closed ring was first introduced to extend the surge margin and keep high efficiency. Finally, the compressor with a variable map width enhancement slot was validated at a compressor performance rig and a fuel cell simulation system. The results from compressor performance test rig indicate that the compressor peak efficiency is as high as 77% and the surge margin is enhanced by about 28.1∼ 42.7 %. The simulation results of the fuel cell system indicate the maximum power consumption of the compressor and the H2 consumption of comprehensive adapted world transient vehicle cycle are reduced by nearly 1.6 kW and 4.86%, respectively, in comparison with the baseline screw compressor.
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