Assessment of the Miller cycle operation in a spark ignition engine via 1D numerical simulation

The article presents the results of a 1D numerical simulation of a spark ignition engine developed to operate in Miller cycle. Miller cycle offers better thermal efficiency compared to Otto cycle due to higher volumetric expansion than compression, which in the current context is of paramount importance. In an engine with fixed geometric compression ratio, Miller cycle operation could be realized by means of either early intake valve closing (EIVC) or late intake valve closing (LIVC). Both cases lead however to a lower volumetric efficiency, thus reducing the indicating mean effective pressure, which in its turn results to a lower power output. The simulation’s aim is not only to assess the impact of implementing the Miller cycle but also to obtain the necessary results for imposing the boundary conditions in a 3D CFD simulation whose purpose is to analyse the influence of the Miller cycle on the internal aerodynamics of the engine.

Influence of a Cu2O hole-transport layer on perovskite solar cellscharacteristics

The article is devoted to the creation of a model of a perovskite solar cell with the FTO/TiO2/CH3NH3PbI3-xClx/Cu2O/Au structure in the SCAPS-1D numerical simulation pro-gram. The effect of the thickness of the CH3NH3PbI3-xClxperovskite layer, as well as the thick-ness, concentration of acceptors, and hole mobility in the Cu2O layer on the photoelectric characteristicsof solar cells has been studied. It was found that the optimal thickness of the perovskite layer is 600–700 nm. An increase in the thickness of the Cu2O layer from 50 nm to 500 nm does not have a significant effect on the efficiency of the solar cell, while the optimal concentration of acceptors in the Cu2O layer is 1018–1019cm-3, and the holemobility should be more than 0.1 cm2/Vs. It is shown that a perovskite solar cell with a hole conductive layer Cu2O has better characteristics compared to the Spiro-OMeTAD layer and has the highest effi-ciency of 21.55%

Evaluation of Water Hammer for Seawater Treatment System in Offshore Floating Production Unit

Water hammer can result in the rupture of pipes, and significant damage to pipe supports is inevitable during the operation of an offshore plant. In this study, the dynamic behaviors of the water hammer caused by closing valves and starting pumps for the seawater treatment system were evaluated by using the 1D numerical simulation model based on the method of characteristics. Before conducting an analysis of a complex piping network, the 1D numerical simulation tools were validated by a comparison between the numerical results and the results from both static and transient experiments that have been conducted in other studies. For the case study, the effects of valve flow characteristics and valve closing time on surge pressure were investigated, and the equal percentage butterfly valve was recommended in order to reduce the surge pressure with a shorter valve closure time and lower weight compared to other valve types.

A Physics-Based Data-Driven Model for History Matching, Prediction, and Characterization of Unconventional Reservoirs

Summary We developed a physics-based data-driven model for history matching, prediction, and characterization of unconventional reservoirs. It uses 1D numerical simulation to approximate 3D problems. The 1D simulation is formulated in a dimensionless space by introducing a new diffusive diagnostic function (DDF). For radial and linear flow, the DDF is shown analytically to be a straight line with a positive or zero slope. Without any assumption of flow regime, the DDF can be obtained in a data-driven manner by means of history matching using the ensemble smoother with multiple data assimilation (ES-MDA). The history-matched ensemble of DDFs offers diagnostic characteristics and probabilistic predictions for unconventional reservoirs.

STUDY OF FREE BURNING ARC CHARACTERISTICS BY DIMENSIONAL ANALYSIS AND COMPUTER SIMULATION

This paper deals with the study of experimental current intensity/voltage characteristics of a free burning arc that appears to be singular: At low intensity current, the arc voltage decreases until a minimum value, corresponding to a critical current intensity Ic. For current intensities higher than Ic, there is an increase of the arc voltage with the current intensity. Dimensional analysis and Pi theorem coupled with a large set of experimental data allow us to evaluate the main physical processes responsible for the characteristics shape. At low current intensity, the plasma is mostly driven by thermal conduction effects while at high current intensity, it is principally governed by radiation losses. Finally, the results obtained from dimensional analysis allow to propose a 1D numerical simulation of the plasma column that gives rather good qualitative results.

Turbocharged CNG Engines for Urban Transportation: Evaluation of Turbolag Reduction Strategies by Means of Computational Analyses

Nowadays, many urban buses for public transportation are fuelled by compressed natural gas (CNG), due to its potential for energy saving and pollutant reduction, with specific reference to particulate matter emissions. However, turbocharging is required to recover the gaseous-fuel related power gap with respect to more traditional engines running on liquid fuels. Therefore, turbolag reduction is fundamental to achieve high performance during engine transients. Significant support for the study of turbocharged CNG engines and guidelines for the turbomatching process can be provided by 1D numerical simulation tools. In this paper, the topic of turbolag reduction is analyzed, and different strategies, namely, Early-Exhaust Valve Opening-Variable Valve Actuation (E-EVO-VVA) and spark timing control for combustion retard (ComR), are analyzed by means of a specifically developed and calibrated GT-POWER® engine model. Tip-in maneuvers in which the engine was coupled to a torque hydraulic converter under stall conditions were investigated, so as to reproduce a typical load transient condition for an urban bus accelerating from engine idle. The best improvement of turbolag was obtained by combining E-EVO-VVA and ComR, with a reduction of turbolag ranging from 60% to 70%. When a limit on the incylinder pressure is introduced, in order to prevent excessive exhaust valve mechanical stresses, the higher achievable reduction in turbolag was found to be between 35% and 45%.