Controllable Preparation and Rapid Photoelectric Response of Homogeneous ZnTe Microspheres

With the use of ethylene glycol as a solvent, polyvinylpyrrolidone as a surfactant and hydrazine hydrate as a reducing agent, uniform spherical ZnTe microstructure was synthesized in a homogeneous reactor...

The Interaction Between the Pilot Diesel and Main NG Injection in an HPDI Engine

High Pressure Direct Injection (HPDI) is a promising combustion concept for the medium- to heavy-duty industry to combat climate change. It uses a pilot diesel injection to ignite the main fuel consisting of Natural Gas (NG). Both fuels are injected directly in the combustion chamber using a dedicated HPDI injector. A significant reduction in carbon dioxide and Particulate Matter is achieved due to the use of the low carbon fuel NG. It is seen in literature that a small change in pilot injection can have profound consequences for the HPDI combustion. This research investigates the interaction between the pilot diesel and main NG injection. A relevant Computational Fluid Dynamics (CFD) simulation environment is setup for this purpose. It is observed that the main NG injection needs a certain pilot trigger to ignite. Furthermore, local conditions are derived to investigate driving factors of the ignition of NG on a fundamental level. A homogeneous reactor model is used to study Ignition Delay (ID) behavior by varying the initial temperature as well as concentrations of radicals H and OH. It is observed that both factors influence the ID. The initial temperature has to be higher than 1110 K in order to ignite the NG under enginelike conditions. It is also observed that species mole fractions H or OH encountered in the CFD simulation can reduce the ID up to 5.5 crank angle degrees at a speed of 1400 RPM.

Effects of EGR and Alternative Fuels on Homogeneous Charge Compression Ignition (HCCI) Combustion Mode

We present in this article an analysis of the impacts of the exhaust gas recirculation (EGR) and alternative fuels on HCCI combustion mode. The objective is to reduce the pollutant emissions below the levels of established pollution standards. The ANSYS CHEMKIN-Pro software and the combined chemical kinetics mechanism were used to perform simulations for a closed homogeneous reactor under conditions relevant to HCCI engines. The calculation process is based on one single-zone in the combustion chamber. Numerical simulation has proven the ability of the models adopted, which use the essential mechanisms of the fuel combustion process, to reproduce, among other things, the evolution of the formation of chemical species. This study showed that adding hydrogen (H2) to methane (CH4) is an interesting alternative fuel because it reduces ignition time. It was concluded that an increase of EGR rate conducts to a slower combustion process, lower temperatures, and the reduction of nitrogen oxide (NOX) emissions.

Homogenization Effects of VVER-1000 Fuel Assembly on Criticality Calculations

Due to cost effective and simplicity homogeneous reactors have been widely used for experimental and research purposes. Parameters which are difficult to get from a heterogeneous reactor system can be easily obtained from a homogeneous reactor system and can be applied in the heterogeneous reactor system if the major parametric differences are known. In this study, homogenization effects of VVER (Water Water Energetic Reactor)-1000 fuel assembly on neutronic parameters have been analyzed with the universal probabilistic code MCNP (Monte Carlo N-Particle). The infinite multiplication factor (k∞) has been calculated for the reconfigured heterogeneous and homogenous fuel assembly models with 2 w/o U-235 enriched fuel at room temperature. Effect of mixing soluble boron into the moderator/coolant (H2O) has been investigated for both models. Direct and fission detected thermal to higher energy neutron ratio also has been investigated. Relative power distributions of both models have been calculated at critical and supercritical states. Burnup calculations for both the reconfigured cores have been carried out up to 5 years of operation. Effective delayed neutron fraction (βeff) and prompt removal lifetime (ℓ) also have been evaluated. All the results show significant differences between the two systems except the average relative power.