Critical Conditions for the Ignition of a Gel Fuel under Different Heating Schemes

A model was developed to research the critical conditions and time characteristics of the ignition of gel fuels in the course of conductive, convective, radiant and mixed heat transfer. MATLAB was used for numerical modeling. Original MATLAB code was established pursuant to the developed mathematical model. For gel fuel ignition at initial temperatures corresponding to cryogenic storage conditions with different heating schemes, a numerical analysis of interconnected processes of heat and mass transfer in the chemical reaction conditions and exothermic and endothermic phase transitions was conducted. The model was tested by comparing the theoretical results with the experimental data. Dependencies were established between the key process characteristic (i.e., the ignition delay time) and the ambient temperature when the following parameters were varied: emissivity, heat emission coefficient, activation energy and pre-exponential factor of the fuel vapor oxidation reaction. The critical values of the main parameters of the energy source were determined. For these values, gel fuel ignition conditions were consistently realized for each heating scheme. The critical heat fluxes necessary and sufficient for the ignition of typical gel fuels were determined.

Measurement of Air-Fuel Mixing in a Diesel Spray at Engine Relevant Conditions Using UV-VIS DBI Diagnostic

Due to the non-premixed nature of diesel combustion, mixing prior to the reaction zone has proven to be one of the primary factors in emissions formation. Therefore, the advancement of diagnostics used to measure mixing fields in diesel applications is imperative for a greater understanding of how in-cylinder emissions mitigation techniques operate. Towards this goal, we have recently demonstrated the use of a high-speed two-wavelength extinction imaging measurement, UV-VIS DBI, for time-resolved measurements of mixing in a diesel spray. This diagnostic operates by back-lighting the spray with ultra-violet and visible illumination. The visible illumination is selected at a non-absorbing wavelength, such that the visible light is only attenuated by liquid droplet scattering, enabling discrete detection of the liquid-vapor mixture and pure vapor phases of the spray. For this work, Ultraviolet and visible light are generated using a ND:YAG pumped frequency-doubled tunable dye laser operating at 9.9 kHz . The simultaneous UV-Visible illumination is used to back-illuminate a vaporizing diesel spray, and the resulting extinction of each signal is recorded by a pair of high-speed cameras. Using an aromatic tracer (naphthalene, BP = 218 °C) in a base fuel of dodecane (BP = 215–217 °C), the UV illumination (280 nm) is absorbed along the illumination path through the spray, yielding a projected image of line-of-sight optical depth that is proportional to the projected fuel vapor concentration in the pure vapor region of the spray. In this paper, a new method of determining the absorption coefficient for the pure-vapor phase of the spray will be discussed, along with showing how an Inverse-Abel transform can be used to compute planar concentration data from the projected concentration data yielded by the diagnostic. This diagnostic and data processing is applied to diesel sprays from two Bosch CRI3-20 ks1.5 single-orifice injectors (140 μm and 90 μm orifice diameters) injecting into a nonreacting high-pressure and temperature nitrogen environment using a constant-flow, optically-accessible spray chamber operating at 60 bar and 900 K. The mixing data produced agrees well with previously existing mixing data, which further instills confidence in the diagnostic, and gives the diesel combustion community access to mixing field data for a 140 μm orifice diameter injector at a 60 bar and 900 K condition.

Efficiency enhancement of the vehicle fuel tank ventilation system by improving its architecture and design

Hydrocarbon emissions from fuel evaporation contribute significantly to the total emissions of harmful substances from vehicles with forced spark ignition. To meet the legally established standards for limiting hydrocarbon emissions from evaporation, all current vehicles use fuel vapor control systems. The design of the system can vary and depends on the sales market of a particular vehicle. This article describes the development of this system for the market of the Russian Federation, as well as optimization for promising sales markets with more stringent environmental requirements.

Investigation of Properties of Diesel Fuel and Carbon Nanotubes Mixture and Characteristics of its Atomization

The fuel economy and exhaust emissions of diesel engines can be improved by adding carbon nanotubes to petroleum diesel fuel. Carbon nanotubes, used as a promising nanoscale additive for diesel fuel, have high thermal conductivity and a large surface area to volume ratio. The thermophysical properties of these fuels, which depend on the composition of the mixtures, are analyzed in this study. Findings of research show that carbon nanotubes added to diesel fuel have little effect on its dynamic viscosity and thermal conductivity. By means of numerical models, we simulated the process of atomization and evaporation of diesel fuel with the different carbon nanotubes content in a constant volume combustion chamber. The accuracy of the calculations is confirmed by the good agreement between the calculated and experimental data. Simulation of mixture atomization showed that the jet length linearly depends on the carbon nanotubes content in diesel fuel. The more carbon nanotubes are in the mixture, the smaller the droplet Sauter mean diameter and the angle of the jet cone opening are. The presence of carbon nanotubes in diesel fuel insignificantly affects the fuel vapor content in it.

Analysis of the vaporization processes in the vehicle fuel tank. New equation for determining the vapor amount

Introduction (problem statement and relevance). Hydrocarbon emissions from vaporizationtank fuel contribute significantly to the total emissions of hazardous substances from vehicles equipped with spark ignition engines. To meet the established standards for limiting hydrocarbon emissions caused by evaporation, all modern vehicles use fuel vapor recovery systems, the optimal parameters of which require the availability and application of mathematical models and methods for their determination.The purpose of the research was to develop a model of vapor generation processes in the car fuel tank and a methodology for determining the main quantitative parameters of the vapor-air mixture.Methodology and research methods. The analysis of the processes of vapor generation in the fuel tank was carried out. It was shown that the mass of hydrocarbons generated in the steam space was directly proportional to its volume and did not depend on the amount of fuel in the tank.Scientific novelty and results. New analytical dependences of the vaporization amount on the saturated vapor pressure, barometric pressure, initial fuel temperature and fuel heating during parking have been obtained.Practical significance. A formula was obtained to estimate the temperature of gasoline boiling starting in the tank, depending on the altitude above sea level and the volatility of gasoline, determined by the pressure of saturated vapors. Using the new equations, the vaporization analysis in real situations (parking, idling, refueling, explosive concentration of vapors) was carried out.

A Binary Liquid Mixture of Bioethanol-Water and Biodiesel-Water as Fuel for NSDC-LNSDCNSDC-L Direct Ethanol-Solid Oxide Fuel Cell

This research studies the possibility on using a binary liquid mixture of bioethanol-water and biodiesel-water as fuel for a NSDC-LNSDCNSDC-L single fuel cell. The ratio of bioethanol-water was 70:30, as well as the ratio of biodiesel-water. The fuel vapor flowed into the fuel cell system under the temperatures of 673, 773 and 873 K with a flow rate of 1–1.5 ml•min-1. The highest power densities were found at 673 K which are 2.984 and 1.838 mW•cm-2 for bioethanol-water and biodiesel-water, respectively. It is a promising result for a single fuel cell test with a very low rate of liquid fuel flow. Meanwhile, open circuit voltage (OCV) of the single fuel cell with bioethanol-water fuel is 1.439 V which is close to the theoretical OCV. However, OCV of the single fuel cell with biodiesel-water as fuel is 0.710 V which is lower than the theoretical OCV. Cell polarization seems still being the problem causing voltage loss during single fuel cell test.