Diagnostiche non convenzionali per l’analisi del processo di iniezione in un motore monocilindrico ad accensione per compressione - Non conventional diagnostics of injection process in single cylinder compression ignition engine

This thesis has been carried out in the Istituto Motori – CNR of Napoli. The mission of the institute is the research on engines and other kinds of propellers for the development of the future transport systems. The main targets of the research activities concern the reduction of pollutant emissions and fuel consumption of modern engines. A variety of experimental and numerical activities are carried out in the institute with the aim to understand the entire functioning chain of internal combustion engines. The research activities of the present doctoral thesis have been run in the optical diagnostics laboratory. In particular, the present work focuses on the analysis of the injection process in a single-cylinder compression ignition engine via direct imaging with high speed cameras. The research engine is derived from a light duty production engine and is fed with commercial Italian diesel fuel. The engine performances have been analyzed in seven operating conditions that are representative of the engine behavior during the homologation cycle New European Driving Cycle (NEDC) when installed on a D-class vehicle. The approach used in this work for the investigation of in-cylinder processes is based on the combination of experimental activities and numerical simulations. A mono-dimensional (1d) model developed by the Sandia National Laboratories to simulate the fuel injection in a control volume combustion vessel has been implemented and adjusted to fit in-cylinder thermodynamic conditions and geometrical limitations. The model has been set up using experimental data collected on the single-cylinder optical engine. The thermodynamic parameters have been collected in conjunction to images of the injection process in the visible range. A sensitivity analysis to the model input values has been made and by comparing the model result to injection images it has been possible to understand the model limitations and potentialities. It has revealed to work well for the simulation of the injection process inside the engine and could provide additional information to the investigated phenomena. For example, the jet/wall interaction has been investigated and the fuel mass impinging on the combustion chamber wall has been correlated to the exhaust emissions of particulate matter (PM). Moreover, the model has been able to provide both the penetrations of the liquid and vapor fuel. Whereas visible imaging of the injection process could provide only images of the fuel liquid phase, it could be very useful to get information about the vapor phase too. The 1d model has revealed to be a valid support for the development of a novel optical technique for the visualization of the vapor fuel using infrared imaging. As aforementioned, visible imaging is able to detect only the fuel liquid phase; for the visualization of the fuel vapor phase there exist several optical techniques characterized by complex set up and high sensitivity to fuel impurities and geometrical limitations. On the contrary, infrared imaging is able to overcome the limitations of the previous diagnostics. For this reason, this technique has been setup and applied for the optical diagnostics in the single-cylinder research engine. The spectral analysis in the range 1.5-5 μm allowed to identify two wavelengths to investigate: at 3.4 μm and at 3.9 μm. The penetration curves obtained from the infrared images have been compared to the ones from visible images and from the model (liquid and vapor penetrations). The two selected wavelength, 3.4 μm and 3.9 μm, demonstrated to be good for the visualization in the infrared of the vapor and liquid phase, respectively. According to these observations, a more accurate analysis of the infrared radiation of the fuel jets and the modeled fuel evaporation rate allowed to understand better the fuel vaporization process. The results reported in this doctoral thesis, the description of the 1d model of fuel injection inside the engine, and the presentation of an innovative optical technique in the infrared for the detection of the fuel vapor phase could contribute to the present scientific context for the development of sustainable transport systems with low environmental impact

Quantum Backaction on kg-Scale Mirrors: Observation of Radiation Pressure Noise in the Advanced Virgo Detector

The quantum radiation pressure and the quantum shot noise in laser-interferometric gravitational wave detectors constitute a macroscopic manifestation of the Heisenberg inequality. If quantum shot noise can be easily observed, the observation of quantum radiation pressure noise has been elusive, so far, due to the technical noise competing with quantum effects. Here, we discuss the evidence of quantum radiation pressure noise in the Advanced Virgo gravitational wave detector. In our experiment, we inject squeezed vacuum states of light into the interferometer in order to manipulate the quantum backaction on the 42 kg mirrors and observe the corresponding quantum noise driven displacement at frequencies between 30 and 70 Hz. The experimental data, obtained in various interferometer configurations, is tested against the Advanced Virgo detector quantum noise model which confirmed the measured magnitude of quantum radiation pressure noise

Supplement: "Localization and broadband follow-up of the gravitational-wave transient GW150914" (2016, ApJL, 826, L13)

This Supplement provides supporting material for Abbott et al. (2016a). We briefly summarize past electromagnetic (EM) follow-up efforts as well as the organization and policy of the current EM follow-up program. We compare the four probability sky maps produced for the gravitational-wave transient GW150914, and provide additional details of the EM follow-up observations that were performed in the different bands

The population of merging compact binaries inferred using gravitational waves through GWTC-3

We report on the population properties of 76 compact binary mergers detected with gravitational waves below a false alarm rate of 1 per year through GWTC-3. The catalog contains three classes of binary mergers: BBH, BNS, and NSBH mergers. We infer the BNS merger rate to be between 10 $\rm{Gpc^{-3} yr^{-1}}$ and 1700 $\rm{Gpc^{-3} yr^{-1}}$ and the NSBH merger rate to be between 7.8 $\rm{Gpc^{-3}\, yr^{-1}}$ and 140 $\rm{Gpc^{-3} yr^{-1}}$ , assuming a constant rate density versus comoving volume and taking the union of 90% credible intervals for methods used in this work. Accounting for the BBH merger rate to evolve with redshift, we find the BBH merger rate to be between 17.9 $\rm{Gpc^{-3}\, yr^{-1}}$ and 44 $\rm{Gpc^{-3}\, yr^{-1}}$ at a fiducial redshift (z=0.2). We obtain a broad neutron star mass distribution extending from $1.2^{+0.1}_{-0.2} M_\odot$ to $2.0^{+0.3}_{-0.3} M_\odot$. We can confidently identify a rapid decrease in merger rate versus component mass between neutron star-like masses and black-hole-like masses, but there is no evidence that the merger rate increases again before 10 $M_\odot$. We also find the BBH mass distribution has localized over- and under-densities relative to a power law distribution. While we continue to find the mass distribution of a binary's more massive component strongly decreases as a function of primary mass, we observe no evidence of a strongly suppressed merger rate above $\sim 60 M_\odot$. The rate of BBH mergers is observed to increase with redshift at a rate proportional to $(1+z)^{\kappa}$ with $\kappa = 2.9^{+1.7}_{-1.8}$ for $z\lesssim 1$. Observed black hole spins are small, with half of spin magnitudes below $\chi_i \simeq 0.25$. We observe evidence of negative aligned spins in the population, and an increase in spin magnitude for systems with more unequal mass ratio

Simulating the Electrochemical-Thermal Behavior of a Prismatic Lithium-Ion Battery on the Market under Various Discharge Cycles

In this paper, a computational fluid dynamics (CFD) model to predict the transient temperature distributions of a prismatic lithium-ion polymer battery (LiPo) cooled by natural convection at various discharge cycles is developed. The thermal behavior of a lithium-ion (Li-ion) battery cell is important for its safety, performance and degradation, and it requires both measurement and modeling. However, most existing thermal models for Li-ion battery cells only account for steady-state temperature fields, while the exercise of a Li-ion battery cell is usually transitory. The Newman’s pseudo-2D approach was used to perform an electrochemical CFD analysis. This approach treats the porous electrode as a collection of equal-sized, isotropic, homogeneous spherical particles. This simplifies the electrode microstructure and assumes a smooth and uniform lithium insertion/extraction in the electrode. The model has been validated through variable discharge rate experimental tests in a controlled chamber. Additionally, infrared images of the battery cell during discharging are taken and the experimental numerical gradient temperature was compared. We have validated the CFD simulations by comparing the temperature, state of charge and voltage curves with experimental data. The model predictions match the experimental data very well. The difficulty in CFD battery simulations with an electrochemical approach lies in the setting of many physical parameters that are difficult to find. In this work, the parameters’ characteristics of the simulated battery are assumed and validated; these can be useful for modeling batteries of the same type. Consequently, the model developed in this work can be applied to predict the temperature distribution of the LiPo prismatic battery and can be used by the battery designers and by the designers of all systems that include batteries

First and second generation biodiesels spray characterization in a diesel engine

Potential improvement on exhaust emissions, biodegradability and the possibility to reduce dependence on fossil fuel resources has led to an increasing interest on the use of biofuels for transport application. In this work, the analysis of the spray behaviour of first and second generation biodiesel in a Euro 5, common rail transparent diesel engine has been performed. GTL, SME and RME fuels have been used in blends at 100% and 50% in volume; while reference fuel consisted of commercial diesel. Two engine operating conditions of the NEDC have been selected: 1500 rpm at 2 bar of brake mean effective pressure (BMEP) and 2000 rpm at 5 bar BMEP. The injection process has been accurately studied, and the influence of the combustion process on the spray behaviour has been taken into account. Typical jets parameters such as penetration and cone angles have been detected and a comparison with theoretical models of Hiroyasu and Siebers has been performed. A new correlation for the forecasting of the jet penetration has been obtained starting from Hiroyasu equations. An image-based method has been applied for the identification of the phenomena that control the spray behaviour during its evolution in the combustion chamber. First generation biodiesels, pure and blends, show longer penetration with respect to the reference fuel at both the engine speed analysed. Moreover, they penetrate for a longer time in the combustion chamber, because of the longer energizing time set, so impingement phenomena can be observed. On the other hand, the second generation biodiesels penetrate less than reference one, due to its lower density, but also because the combustion of the pilot injection causes an increase of pressure that obstructs the penetration in the combustion chamber. Finally, a good agreement between the breakup times computed by means of the Hiroyasu and Siebers correlations and the ones from the experimental data has been found

Analogies in the Analysis of the Thermal Status of Batteries and Internal Combustion Engines for Mobility

Thermal management is an important research area for the automotive sector in order to make high-efficiency and low-impact future vehicles. The transition from internal combustion engines to battery systems in the automotive field requires new skills to be achieved in the shortest possible time. The well-consolidated knowledge of thermal management of engine systems can be rearranged to face new challenges regarding the thermal control of batteries. The present work aims to show the analogies between the thermal behavior of an engine component, such as the piston, and of a battery. The thermodynamic processes involved during the operation are described, experimentally investigated, and modeled. The external temperature of the piston window is measured once per cycle with a K-type sheathed thermocouple, while the surface temperature of the battery is detected via infrared imaging. An almost-fixed stabilization time of 500 s is observed for the engine while it varies with the current load for the battery ranging from 1800 s to 3000 s, for the tested cases. Different temperature increments are also observed. Two mono-dimensional (1D) models of heat transfer are built using the finite-difference method. Good agreement with the experimental data is quantitatively demonstrated by a Normalize Root Mean Square Error lower than 0.07 for all the test cases and systems, except for the battery charging phase. The analysis of the temperature provides an estimation of the heat losses for the two systems, spanning from 15% to 27% for the engine and from 6% to 10% for the battery. The analysis carried out in this work can provide a methodology to understand and improve the thermal management of the new mobility system

Carbon and Graphene Coatings for the Thermal Management of Sustainable LMP Batteries for Automotive Applications

The increment of battery temperature during the operation caused by internal heat generation is one of the main issues to face in the management of storage systems for automotive and power generation applications. The temperature strongly affects the battery efficiency, granting the best performance in a limited range. The investigation and testing of materials for the improvement of heat dissipation are crucial for modern battery systems that must provide high power and energy density. This study presents an analysis of the thermal behavior of a lithium-polymer cell, which can be stacked in a battery pack for electric vehicles. The cell is sheltered with layers of two different materials: carbon and graphene, used in turn, to dissipate the heat generated during the operation in natural convection. Optical diagnostics in the infrared band is used to evaluate the battery surface temperature and the effect of the coatings. Experiments are performed in two operating conditions varying the current demand. Moreover, two theoretical correlations are used to estimate the thermal parameters of the battery with a reverse-logic approach. The convective heat transfer coefficient h and the specific heat capacity cp of the battery are evaluated and provided for the Li-ion battery under investigation for different coatings’ conductivity. The results highlight the advantage of using a coating and the effect of the coating properties to reduce the battery temperature under operation. In particular, graphene is preferable because it provides the lowest battery temperature in the most intense operating condition