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In this work, layer-by-layer organic photovoltaics (LbL OPVs) were prepared by sequentially spin-coating PM1 and L8-BO solutions. The solvent additive 1,8-diiodooctane (DIO), which has a high boiling point, and solid additive l,3,5-trichlorobenzene (TCB), which has a high volatile, were deliberately selected to incorporate with the L8-BO solutions. The power conversion efficiency (PCE) of LbL OPVs was considerably enhanced from 17.43% to 18.50% by employing TCB as the additive, profiting by the concurrently increased short-circuit current density (JSC) of 26.74 mA cm−2 and a fill factor (FF) of 76.88%. The increased JSCs of LbL OPVs with TCB as additive were ascribed to the tilted-up absorption edge in the long wavelength range and the external quantum-efficiency spectral difference between LbL OPVs with and without TCB as an additive. The molecular arrangement of L8-BO and the PM1 domain was enhanced with TCB as an additive, which was most likely responsible for the increased charge mobilities in the layered films processed with additives. It was indicated that the dynamic film-forming process of the acceptor layers plays a vital role in achieving efficient LbL OPVs by employing additive strategy. Over 6% PCE improvement of the LbL OPVs with PM1/L8-BO as the active layers can be achieved by employing TCB as additive.

In this work, pseudo-bilayer planar heterojunction (PPHJ) all-polymer solar cells (APSCs) were constructed on the basis of the commonly used PY-IT and PM6 as the acceptor and donor, respectively. A nonfullerene small molecular acceptor (NF-SMA) BTP-eC9 was incorporated into the PY-IT layer as the solid additive in consideration of its similar building block to PY-IT. BTP-eC9 can serve as a photon capture reinforcer and morphology-regulating agent to realize more adequate photon capture, as well as a more orderly molecular arrangement for effective carrier transport. By incorporating 2 wt% BTP-eC9, the efficiency of PM6/PY-IT-based PPHJ-APSCs was boosted from 15.11% to 16.47%, accompanied by a synergistically enhanced short circuit current density (JSC, 23.36 vs. 24.08 mA cm−2) and fill factor (FF, 68.83% vs. 72.76%). In another all-polymer system, based on PBQx-TCl/PY-DT as the active layers, the efficiency could be boosted from 17.51% to 18.07%, enabled by the addition of 2 wt% L8-BO, which further verified the effectiveness of using an NF-SMA as a solid additive. This work demonstrates that incorporating an NF-SMA as a solid additive holds great potential for driving the development of PPHJ-APSCs.

The power conversion efficiencies (PCEs) of organic photovoltaics (OPVs) have reached more than 19%, along with the prosperous development of materials and device engineering. It is meaningful to make a comprehensive review of the research of OPVs for further performance improvement. In this review, some typical materials of high-performance OPVs are summarized, including representative polymer donor materials, non-fullerene acceptor materials, and interfacial modification materials, as well as their design rules for molecular engineering. From the point of view of device engineering, active layer treatment and deposition technology are introduced, which can play a critical role in adjusting the degree of molecular aggregation and vertical distribution. Meanwhile, a ternary strategy has been confirmed as an efficient method for improving the performance of OPVs, and the multiple roles of the appropriate third component in the photo-electronic conversion process are emphasized and analyzed. The challenges and perspectives concerning this region are also put forward for further developing high-performance OPVs.

The application of additive manufacturing in the field of aviation hydraulics greatly improves the design freedom of hydraulic valve internal flow channels. Pressure loss in hydraulic valve internal flow channels is a primary factor that designers need to consider, and the rapid prediction of pressure loss is very helpful for flow channel design. At present, most studies only focus on how much the pressure loss in an additive manufacturing (AM) hydraulic channel is reduced compared with an original hydraulic channel, and a mathematical model of pressure loss in an AM curved channel is still lacking. In this paper, the pressure loss in a curved flow channel was firstly studied, and the main parameters affecting the pressure loss were determined using the dimensionless analysis method. Using computational fluid dynamics simulation, the relationships between the flow channel diameter, the flow channel length, the flow channel curvature radius, the fluid velocity and pressure loss were studied. According to the multiple regression analysis method, the mathematical model of pressure loss in aviation hydraulic channels was developed, and the model was solved based on the orthogonal experimental results. The pressure loss in the flow channel samples fabricated using selective laser melting was tested, and the results showed that the average error between the test results and the mathematical model calculation results was 7.72%. This model can be used to quickly predict the pressure loss in curved flow channels in the aviation hydraulic field.

Modern civilization and economic development of humankind have been largely based on the exploitation and utilization of fossil energy [...]

The nitrogen content of electric arc furnace (EAF) steel is much higher than that of basic oxygen furnace (BOF) steel, which cannot meet the requirements of high-grade steel. Most denitrification processes only considered a single smelting condition, which leads to poor denitrification effect. In this study, a hot state experiment was conducted to simulate the melting process of EAF steelmaking and to explore the thermodynamic and kinetic constraints of the molten steel nitrogen reaction in the scrap melting, oxygen blowing decarburization, and rapid temperature rise stages. The experimental results showed that the nitrogen reaction in the molten pool during the scrap melting stage was a first-order nitrogen absorption reaction, and the reaction-limiting link was the diffusion of nitrogen atoms in the molten steel. When the carbon content increases to 4.5%, the bath temperature decreases to 1550 °C, and the nitrogen partial pressure decreases to 0.2 PΘ, the nitrogen saturation solubility decreased to 0.0198%, 0.0318%, and 0.0178%, respectively. At the same time, the rate constants decreased to 0.132 m/min, 0.127 m/min, and 0.141 m/min, respectively. The nitrogen reaction in the oxygen blowing decarburization stage was a secondary denitrification reaction, and the reaction-limiting link was the gas–liquid interface chemical reaction. Argon had better degassing effect. When the argon flow rate increased from 100 mL/min to 300 mL/min, the reaction constant increased by about four times. When the oxygen content of molten steel was 0.0260%, the denitrification rate constant decreased by about 2.5 times. The nitrogen content of liquid steel was higher than 0.045%, and the reaction was a secondary reaction. As the nitrogen content decreased, the reaction rate decreased, and the reaction-limiting link changed from the gas–liquid interface chemical reaction to the joint control of mass transfer and chemical reaction. The oxygen content in the molten steel can not only hinder the chemical reaction of nitrogen at the gas–liquid interface, but also reduce the mass transfer rate of nitrogen atoms in the molten steel. The results provided a theoretical basis for the optimization of nitrogen removal process and further reduction of nitrogen content in liquid steel.

Interface modification is an important way to get better performance from organic solar cells (OSCs). A natural biomolecular material methionine was successfully applied as the electron transport layer (ETL) to the inverted OSCs in this work. A series of optical, morphological, and electrical characterizations of thin films and devices were used to analyze the surface modification effects of methionine on zinc oxide (ZnO). The analysis results show that the surface modification of ZnO with methionine can cause significantly reduced surface defects for ZnO, optimized surface morphology of ZnO, improved compatibility between ETL and the active layer, better-matched energy levels between ETL and the acceptor, reduced interface resistance, reduced charge recombination, and enhanced charge transport and collection. The power conversion efficiency (PCE) of OSCs based on PM6:BTP-ec9 was improved to 15.34% from 14.25% by modifying ZnO with methionine. This work shows the great application potential of natural biomolecule methionine in OSCs.

The high temperature brittleness range of medium carbon microalloyed steel under an actual continuous casting process was determined by the high temperature tensile test. The test results revealed that only a third of the brittle temperature range from 650–825 °C was due to intergranular ferrite in the experimental steel. In addition, it was found that the plastic recovery was fast and stable when the temperature was lower than 725 °C (the lowest plastic temperature). Bending/straightening operation in this temperature range was conducive to controlling the generation of corner cracks. In order to keep the corner temperature at the low temperature end of the plastic curve when the slab was bent/straightened, the cooling water scheme of the secondary cooling zone of the continuous caster was formulated by numerical calculation. By appropriately increasing the cooling water flow in the foot roll and the secondary cooling zones 1–5, the corner temperature of slab during bending operation was 600–700 °C, avoiding the brittle temperature range. The industrial test was then carried out. The results showed that after using the optimized water volume, the corner grains of the slab were uniform and the microstructure was mainly pearlite + ferrite. In addition, the abnormally large grain size was reduced, and a large amount of ferrite was generated inside the grain, which avoided stress concentration at the corner of the slab during bending/straightening operation, and basically eliminated the corner crack of the slab.

The power conversion efficiency (PCE) of organic photovoltaics (OPVs) has exceeded 18% with narrow bandgap, non-fullerene materials Y6 or its derivatives when used as an electron acceptor. The PCE improvement of OPVs is due to strong photon harvesting in near-infrared light range and low energy loss. Meanwhile, ternary strategy is commonly recognized as a convenient and efficient means to improve the PCE of OPVs. In this review article, typical donor and acceptor materials in prepared efficient OPVs are summarized. From the device engineering perspective, the typical research work on ternary strategy and tandem structure is introduced for understanding the device design and materials selection for preparing efficient OPVs.

Air intake and fuel supply conditions are the major factors that affect diesel engine performance at plateau. In a regulated two-stage turbocharged diesel engine, these parameters are reflected as the adjustment of fuel injection mass (mfuel), fuel injection advance angle, and bypass valve opening of a high-pressure stage (HP) turbine. Due to the strongly nonlinear nature and complexity of the diesel engine, it is difficult to find the proper parameter combinations. That is why a model-based optimization method is adopted in this paper. The simulation model of a six-cylinder two-stage turbocharged diesel engine is built on the GT-SUITE platform. According to the analysis of diesel engine operation characteristics at high altitude, a fuzzy optimization algorithm is proposed based on a fuzzy logic controller and is realized in a MATLAB/simulink (MATLAB 2014, Mathworks, Natick, MA, USA) environment. Joint optimization of air intake and fuel supply parameters is then performed on the GT-MATLAB co-simulation platform. Results show that engine torque at full load is significantly increased. At the full load point of 2100 r/min, engine power is increased from 256.5 to 319.6 kW, and brake specific fuel consumption (BSFC) is reduced from 243.1 to 222.3 g/(kW·h). Peak torque is increased from 1944.8 to 2173.2 N·m.

The internal combustion engine (ICE) as a main power source for transportation needs to improve its efficiency and reduce emissions. The Organic Rankine Cycle (ORC) is a promising technique for exhaust heat recovery. However, vehicle engines normally operate under transient conditions with both the engine speed and torque varying in a large range, which creates obstacles to the application of ORC in vehicles. It is important to investigate the dynamic performance of an ORC when matching with an ICE. In this study, the dynamic performance of an ICE-ORC combined system is investigated based on a heavy-duty diesel engine and a 5 kW ORC with a single-screw expander. First, dynamic simulation models of the ICE and the ORC are built in the software GT-Power. Then, the working parameters of the ORC system are optimized over the entire operation scope of the ICE. A closed-loop proportional-integral (PI) control together with a feedforward control is designed to regulate the operation of the ORC during the transient driving conditions. The response time and overshoot of the PI control are estimated and compared with that of the feedforward control alone. The results based on the World Harmonized Transient Cycle (WHTC) indicate that the designed closed-loop PI control has a shorter response time and a better trace capacity during the dynamic processes. The average output power and thermal efficiency during the WHTC cycle are improved by 3.23% and 2.77%, respectively. Compared with the feedforward control alone, the designed PI control is more suitable for practical applications.

In-cylinder air flow is very important from the point of view of mixture formation and combustion. In this direction, intake chamber structure and piston crown shape play a very crucial role for in-cylinder air pattern of opposed-piston two-stroke (OP2S) engines. This study is concerned with the three-dimensional (3D) computational fluid dynamics (CFD) analysis of in-cylinder air motion coupled with the comparison of predicted results with the zero-dimensional (0D) parametric model. Three configurations viz., a flat piston uniform scavenging chamber, a flat piston non-uniform scavenging chamber and a pit piston non-uniform scavenging chamber have been studied. 0D model analysis of in-cylinder air flow is consistent with 3D CFD simulation. It is concluded that a pit piston non-uniform scavenging chamber is the best design from the point of view of tumble ratio, turbulent kinetic energy and turbulent intensity, which play very important roles in imparting proper air motion. Meanwhile a flat piston uniform scavenging chamber can organize a higher swirl ratio and lower tumble ratio which is important to improve the scavenging process.

In opposed-piston folded-cranktrain diesel engines, the relative movement rules of opposed-pistons, combustion chamber components and injector position are different from those of conventional diesel engines. The combustion and heat release characteristics of an opposed-piston folded-cranktrain diesel engine under different operating conditions were investigated. Four phases: ignition delay, premixed combustion, diffusion combustion and after combustion are used to describe the heat release process of the engine. Load changing has a small effect on premixed combustion duration while it influences diffusion combustion duration significantly. The heat release process has more significant isochoric and isobaric combustion which differs from the conventional diesel engine situation, except at high exhaust pressure and temperature, due to its two-stroke and uniflow scavenging characteristics. Meanwhile, a relatively high-quality exhaust heat energy is produced in opposed-piston folded-cranktrain diesel engines.

This paper describes a method for the control of transient exhaust gas recirculation (EGR) systems. Firstly, a state space model of the air system is developed by simplifying a mean value model. The state space model is linearized by using linearization theory and validated by the GT-Power data with an operating point of the diesel engine. Secondly, a state feedback controller based on the intake oxygen mass fraction is designed for EGR control. Since direct measurement of the intake oxygen mass fraction is unavailable on the engine, the estimation method for intake oxygen mass fraction has been proposed in this paper. The control strategy is analyzed by using co-simulation with the Matlab/Simulink and GT-Powers software. Finally, the whole control system is experimentally validated against experimental data of a turbocharged diesel engine. The control effect of the state feedback controller compared with PID controller proved to be further verify the feasibility and advantages of the proposed state feedback controller.

Currently, internal combustion engines (ICEs) are still the main power for transportation. Energy conservation and emission reduction for ICEs have become the driving force of the industrial R&D in recent years. Organic Rankine cycle (ORC) is a feasible technology to recover the waste heat of an ICE so that the energy efficiency can be enhanced apparently. However, there are still many obstacles needed to be overcome for the application of an ORC together with an ICE. When a vehicle is driving, the operation conditions of the ICE vary in a large range. The operation of the ORC needs to be regulated accordingly to achieve maximum efficiency. In this study, the operation characteristics of an ICE-ORC combined system is investigated and the transient performance is analyzed. First, an integrated simulation model of the ICE and the ORC was built in GT-POWER software. A 5 kW single-screw expander was employed for the ORC system. The working characteristics of the ORC system were evaluated under various working conditions of the ICE. The matching principles of the ORC with the ICE were discussed and the optimal operation conditions of the ORC over the entire engine’s working range were obtained. Subsequently, a feedforward control strategy for the ORC system was designed in MATLAB/SIMULINK. Finally, the entire model was simulated under a transient driving cycle of a vehicle. The results indicate that the pump speed and the expander speed are two important parameters and must be adjusted according to the engine’s working condition. The speed of the single-screw expander maintains in the low-speed region and the pump speed is tuned to achieve a high evaporation pressure and a proper superheat degree of the working fluid at the inlet of the expander. Thus, the net power output can be maximized. The designed feedforward control strategy can adjust the working condition of the ORC automatically to match with the working condition of the ICE. The ORC operates intermittently and an impulse power is output under the urban driving conditions. However, the working time of the ORC is increased significantly and the power output is relatively higher under the highway conditions.

The fuel injection cycle-to-cycle variation characteristic in an opposed-piston compression ignition engine was investigated experimentally. Based on the optimal Proportion Integration Differentiation (PID) method, a new control method was proposed by utilizing a rail pressure error state observer (OBS) before feedback. Compared with the conventional filtering treatment method, the OBS method was developed to simultaneously account for the flow mass changing and the dynamics of a common rail system, rather than representing the rail pressure state as an average value over a period time. The OBS method was subsequently implemented in the control system to investigate the injection pressure oscillation characteristic and cycle-to-cycle variation of injected fuel quantity. The results show that the present OBS method substantially reduces the injection pressure oscillation, improves response characteristics of the control system, and produces qualitatively satisfactory fuel injection cycle-to-cycle variation in the opposed-piston compression ignition (OPCI) engine.

In order to improve the diesel engine performance under plateau (high altitude) conditions, a new Speed Adjustable Compound (SAC) supercharging method is proposed. A simulation model based on a six-cylinder V-type turbocharged intercooler diesel engine is built on the GT-POWER platform, and then simulation-based research is carried out. A genetic algorithm (GA) is used to identify the best operation parameters, including the supercharger speed and fuel injection quantity under steady state conditions. Transient performance is obtained through starting process simulation of a vehicle with SAC engine on the MATLAB/Simulink GT-POWER co-simulation platform. Both the steady and transient performance of the SAC engine are compared with those of the original engine. Results show that the torque of the SAC engine at full load is significantly increased when the engine speed n < 1600 r/min. The increment of the maximum torque can reach up to 31% at 1000 r/min compared to that of the original engine, while the peak torque is increased by 9%. The fuel consumption deterioration is restricted within 5%. What’s more, the SAC engine can help reducing the acceleration time by 20% during tip-in pedal events during the vehicle starting process.

The common rail pressure has a direct influence on the working stability of Opposed-Piston Two-Stroke (OP2S) diesel engines, especially on performance indexes such as power, economy and emissions. Meanwhile, the rail pressure overshoot phenomenon occurs frequently due to the operating characteristics of OP2S diesel engines, which could lead to serious consequences. In order to solve the rail pressure overshoot problem of OP2S diesel engines, a nonlinear concerted algorithm adding a speed state feedback was investigated. First, the nonlinear Linear Parameter Varying (LPV) model was utilized to describe the coupling relationship between the engine speed and the rail pressure. The Linear Quadratic Regulator (LQR) optimal control algorithm was applied to design the controller by the feedback of speed and rail pressure. Second, cooperating with the switching characteristics of injectors, the co-simulation of MATLAB/Simulink and GT-Power was utilized to verify the validity of the control algorithm and analyze workspaces for both normal and special sections. Finally, bench test results showed that the accuracy of the rail pressure control was in the range of ±1 MPa, in the condition of sudden 600 r/min speed increases. In addition, the fuel mass was reduced 76.3% compared with the maximum fuel supply quantity and the rail pressure fluctuation was less than 20 MPa. The algorithm could also be appropriate for other types of common rail system thanks to its universality.