Spraying of Composite Liquid Fuels Based on Types of Coal Preparation Waste: Current Problems and Achievements: Review

This article discusses the atomization of composite liquid fuels. A large group of injectors is considered. A comparative analysis of the atomization characteristics (droplet sizes and velocities, jet opening angles) and the influence of the fuel characteristics (density, viscosity, component composition) and the process parameters (the ratio of the fuel–air mass flow rates, the features of the jet formation) has been carried out. Finally, the most effective types of injectors, which provide for the necessary characteristics of fuel atomization for its combustion, have been determined. The most favorable conditions for the applicability of each type of atomization have been formulated. Possible mechanisms of secondary fragmentation of droplets of composite fuels have been analyzed: those resulting from mutual collisions of droplets in the flux and from the interaction with a solid surface as well as those resulting from thermal overheating in the presence of a phase boundary or a large gradient of component volatility. A conclusion is made about the need of using a synergistic effect of primary and secondary atomization of fuel suspension droplets.

Towards Understanding the Structure of Subcritical and Transcritical Liquid–Gas Interfaces Using a Tabulated Real Fluid Modeling Approach

A fundamental understanding and simulation of fuel atomization, phase transition, and mixing are among the topics researchers have struggled with for decades. One of the reasons for this is that the accurate, robust, and efficient simulation of fuel jets remains a challenge. In this paper, a tabulated multi-component real-fluid model (RFM) is proposed to overcome most of the limitations and to make real-fluid simulations affordable. Essentially, a fully compressible two-phase flow and a diffuse interface approach are used for the RFM model, which were implemented in the CONVERGE solver. PISO and SIMPLE numerical schemes were modified to account for a highly coupled real-fluid tabulation approach. These new RFM model and numerical schemes were applied to the simulation of different fundamental 1-D, 2-D, and 3-D test cases to better understand the structure of subcritical and transcritical liquid–gas interfaces and to reveal the hydro-thermodynamic characteristics of multicomponent jet mixing. The simulation of a classical cryogenic injection of liquid nitrogen coaxially with a hot hydrogen jet is performed using thermodynamic tables generated by two different equations of state: Peng–Robinson (PR) and Soave–Redlich–Kwong (SRK). The numerical results are finally compared with available experimental data and published numerical studies with satisfactory agreement.

Volumetric losses of the compression process in a hypocycloidal pump in the light of the gas desorption effect

The effect of gas desorption from the solution with nucleation of gas bubbles is a process that allows to improve fuel atomization in diesel engines. The advantage of such a process, which has been experimentally proven, is a significant reduction in harmful emissions. The conducted research highlighted one of the fundamental problems. This problem concerned the injection pump - it was necessary to design a new construction that would be adapted to the desorption effect. The authors of the work proposed a construction based on a hypocycloidal drive. Due to the nature of the process, i.e. the use of exhaust gases dissolved in diesel fuel, it was very important to analyze the volumetric losses of the compression process - this is the main goal of this article. The authors proved that for the adopted design assumptions, the power of volumetric losses resulting from compressibility is 0.25% of the power consumed by the pump.

Experimental Analysis of Swirl Fuel Injector in Liquid Propellant Rocket Engine

Fuel injector for a liquid rocket is a very important component since a small difference in its design can drastically affect the combustion efficiency. The primary function of the injector is to break the fuel up into very small droplets. The concept of this project is to perform the fuel atomization with the desired cone angle. This atomization is achieved by passing the fuel through a swirl fuel injector which is connected to the fuel tank and air compressor. Three different orifices of various diameters are designed with different cone angles. The experimental setup consists of a fuel injector with the swirler inside, which is made up of brass with two different vane angles. The air compressor is used for pressurizing the fuel through the injectors. The cold flow experiment is conducted by passing the mixture of air and fuel to get the atomization. The injector is tested with various pressures ranging from 3 to 7 bar for the two cone angles with varying orifice diameters and the different spray patterns are captured. The results are compared, tabulated and correlated with existing values.

Low-order modeling of high-altitude relight of jet engine combustors

A physics-based, low-order ignition model is used to assess the ignition performance of a kerosene-fueled gas-turbine combustor under high-altitude relight conditions. The ignition model used in this study is based on the motion of virtual flame particles and their extinction according to a Karlovitz number criterion, and a stochastic procedure is used to account for the effects of spray polydispersity on the flame’s extinction behavior. The effects of large droplets arising from poor fuel atomization at sub-idle conditions are then investigated in the context of the model parameters and the combustor’s ignition behavior. For that, a Reynolds-averaged Navier-Stokes simulation of the cold flow in the combustor was performed and used as an input for the ignition model. Ignition was possible with a Sauter mean diameter (SMD) of 50 μm, and was enhanced by increasing the spark volume. Although doubling the spark volume at larger SMDs (75 and 100 μm) resulted in the suppression of short-mode failure events, ignition was not achieved due to a reduction of the effective flammable volume in the combustor. Overall, a lower ignition probability is obtained when using the stochastic procedure for the spray, which is to be expected due to the additional detrimental effects associated with poor spray atomisation and high polydispersity.

Possibilities of using water-fuel emulsion in order to extend the diesel operating range and improvement of fuel supply processes

В статье представлены результаты математического моделирования процессов топливоподачи судового дизеля при работе по винтовой характеристике при использовании дизельного топлива и водотопливной эмульсии с водосодержанием 30% в качестве аль­тернативного топлива. В результате исследования выявлены особенности процессов топливоподачи и влия­ние альтернативного топлива на рабочие характеристики впрыскивания серийной топлив­ной аппаратуры при работе на номинальном и частичных режимах. При оценке качества работы топливной аппаратуры учитывались: изменение характеристики подачи топлива; особенности распыливания топлива в начальной и конечной фа­зах впрыскивания; повышение стабильности последовательных циклов впрыскивания за счет увеличения активного хода плунжера; колебания остаточного давления в трубопро­воде высокого давления при последовательных циклах впрыскивания. При применении водотопливной эмульсии возможно существенное повышение каче­ства работы судового дизеля, расширение диапазона стабильных подач серийной топлив­ной аппаратуры как за счет возможности снижения скоростных режимов при малых подачах топлива, так и обеспечения форсированных подач топлива вследствие отсутствия повторных впрыскива­ний. The article presents the results of the mathematical modeling of marine diesel’s fuel supply processes during the screw characteristic while using diesel fuel and water-fuel emulsion with 30% water content as alternative fuel. As a result of the research, the features of the fuel supply processes and the effect of alternative fuel on the serial fuel equipment injection characteristics during operation in nominal and partial modes were identified. Considering the quality of fuel equipment operation the following features were taken into account, they are: changing fuel supply characteristics; features of fuel atomization in the initial and final phases of injection; increasing stability of the injection in sequential cycles by increasing plunger active stroke; residual pressure oscillations in the high pressure line during injection consecutive cycles. Using the water-fuel emulsion it is possible to significantly increase a quality of marine diesel engine operation, to extend the stable fuel supply range of the serial fuel equipment both from the possibility of speed modes reducing during fine fuel feed and providing forced fuel feed due to absence of repeating injections.

Experimental comparison of the spray atomization of heavy and light fuel oil at different temperatures and pressures for pressure-swirl injector

In this study, the atomization of heavy fuel oil (Mazut) and diesel fuel at different pressures is compared experimentally. Also, the effects of temperature on the Mazut fuel atomization are investigated experimentally. Mass flow rate, discharge coefficient, wavelength, liquid film thickness, ligament diameter, spray angle, breakup length, and sature mean diameter are obtained for the Mazut and diesel fuel. Fuels spray images at different pressures and temperatures are recorded using the shadowgraphy method and analyzed by the image processing technique. Error analysis is performed for the experiments, and the percentage of uncertainty for each parameter is reported. The experimental results are compared with the theoretical results. Also, Curves are proposed and plotted to predict changes in the behavior of atomization parameters. Diesel fuel has less viscosity than Mazut fuel. Diesel fuel has shorter breakup length, wavelength, liquid film thickness, and sature mean diameter than Mazut fuel at the same pressure. Diesel fuel has a larger spray angle and a larger discharge coefficient than Mazut fuel at the same pressure. As the pressure and temperature increase, fuel atomization improves. The viscosity of Mazut fuel is decreased by temperature increase. As the fuel injection pressure and temperature increase, breakup length, wavelength, liquid film thickness, and sature mean diameter decrease; also, spray angle increases.