Search

The atomization process of fuel spray injection in internal combustion engines affects the spray mixture formation process, the combustion characteristics, and the formation of toxic substances. Therefore, several optical measurement procedures have been developed and applied to capture spray features, including imaging methods and laser diagnostics. It has been concluded that the spatial resolution of fine spray droplets detection in imaging with silver halide film is much better than with a CCD imaging device. Therefore, the authors previously developed a novel imaging technique called Super High Spatial Resolution Photography (SHSRP), which allows for whole spray imaging while maintaining the spatial resolution of tiny droplets. This is a wide-field, high-resolution imaging method that can measure the entire spray area at the droplet scale. However, the image analysis method analyzes the intensity gradient of the outer edge of the droplet, and the accuracy of droplet analysis deteriorates as the droplet diameter is small. In this study, a new image analysis method with wide-field and high-resolution images acquired by SHSRP was developed to improve the analysis accuracy of spray droplets. The analysis method of depth of object field, which depends on droplet size, was changed from one-dimensional analysis of the intensity gradient of the outer edge of the droplet to two-dimensional analysis using the intensity deviation of the entire droplet area. For the developed analysis method, analysis of error based on scattering theory was conducted and the droplet capture ratio in diesel spray was analyzed to verify the accuracy. As a result, it was found that the particle size distribution obtained has no peaks due to noise effects, and that the presented analysis method is accurate enough to characterize the particle size distribution of diesel spray.

ABSTRACT: A breakup model used in spray combustion simulations was developed to predict the breakup process of spray droplets, which has large influences on the mixture formation and the combustion process in internal combustion engines. Taylor Analogy Breakup (TAB) Model is widely used as a droplet breakup model. Improved TAB (ITAB) Model has been developed by improving model constants and the breakup/non-breakup boundary condition of TAB Model. ITAB Model reproduces the dimensionless breakup time based on the observation results of the single droplet breakup behavior and CFD simulation results. In this study, calculation methods of droplet diameter and droplet velocity after breakup in ITAB Model are modified to avoid fitting model constants during spray analysis. Droplet diameter after breakup is determined by calculating Sauter Mean Diameter and using the droplet diameter distribution after breakup based on the observation results of the single droplet breakup behavior. The calculation constant for Sauter Mean Diameter is a function of Weber number to reproduce the breakup phenomenon of single droplets. Droplet velocity after breakup is calculated based on the energy conservation law of droplets used in Enhanced TAB Model. This model shows that Sauter Mean Diameter after breakup is almost same and perpendicular motion of droplets after breakup is more active than TAB Model. This model also considers the effects of the fuel physical properties on breakup characteristics. Model analysis shows that droplet diameter after breakup of the high boiling point component fuel is larger under same conditions and the effect of temperature change is larger than that of the low boiling point component fuel.

Direct fuel injection spray is used to improve thermal efficiency and environmental performance in SI engines. A mixture is formed through momentum exchange between fuel droplets and ambient gas, along with mixing accompanied by droplets evaporation and diffusion. Both the droplets development derived from the liquid fuel atomization and the entrainment ambient air predominate the mixture formation process. The purpose of this study is to elucidate the momentum exchange characteristics of the spray formed by a single-hole injector for direct injection gasoline engines. To clarify the momentum exchange characteristics of spray droplets, the spray was visualized by optical experiments and the spray development process was analyzed. The parameters are injection pressure and ambient density. A comparison of experimental results and a model analysis of a single droplet movement was conducted, and different of deceleration characteristics were evaluated. In the case of the fuel spray, the induced ambient air by the spray tip droplets decreases the relative velocity between the spray droplets and the spray internal flow. A model for predicting the temporal variation of the spray tip penetration from the different of momentum exchange characteristics between the spray and the droplet was proposed.

In a direct-injection gasoline engine, strict control of pollutant emissions at cold start is a critical point to comply with new regulations, and the fuel film formed by spray impingement on the piston wall is closely related. In this context, the purpose of this study is to clarify the fuel film formation process of spray impinging on a low temperature wall. Total internal reflection laser induced fluorescence (TIR-LIF) method was applied to the fuel film formed by wall impingement gasoline spray. TIR-LIF method can measure the fluorescence from fuel film without the influence of the spray droplet. The fluorescence intensity from the fuel film depends on the film thickness and temperature. In this paper, the temperature dependence of the fluorescence from the fuel film was investigated under the condition that the laser light is totally reflected from the top surface of the film. The order of magnitude of the heat transfers due to the mixing of spray droplets and fuel film, the heat transfer from the ambient gas, and the heat transfer from the wall were compared and modeled. A method to simultaneously calculate the unsteady change in fuel film thickness and fuel film temperature was developed. Then, the model analysis method was applied to the measured experimental data and verified.

The fuel injection in diesel engines have a significant effect on the engine performance. But there is little knowledge on the characteristics of dispersion of liquid phase concentration. The purpose of this study is to clarify the dispersion process of the liquid phase of diesel spray through quantitative analysis of the liquid phase concentration distribution in non-evaporating diesel spray. In this paper, a quantitative analysis method of the liquid phase concentration of diesel spray under non-evaporative conditions is developed. The cross-sectional mass flow of the fuel was obtained using the momentum theory from the measured concentration distribution of the liquid phase with the laser induced fluorescence method. The relationship between the fluorescence intensity and the liquid phase concentration was estimated. In addition, a scheme was developed to account for the attenuation of the laser light and fluorescence, which results in a quantitative spatial distribution of the liquid phase concentration. Using this method, the dispersion process of the liquid phase in diesel spray was evaluated.

In recent years, with the depletion of fossil resources, there is a need to further improve the thermal efficiency of diesel engines. In order to improve the thermal efficiency of diesel engines, it is necessary to realize rapid combustion. The combustion process in diesel engines is greatly affected by spray characteristics and depends on air fuel mixture characteristics. Therefore, it is necessary to grasp the detailed spray characteristics in mixture formation process. In the past, many studies on the spray characteristics in mixture formation process have been reported. For example, Nishiura et al experimentally evaluated the effect of fuel injection pressure, nozzle hole diameter, and ambient density on the spray characteristics (Nishiura and Inoue ,2019). However, most of the previous reports have evaluated the spray characteristics using the total time averaged over a quasi-steady period for the physical quantity. Thus, the temporal and spatial variability of the spray and the large-scale vortical structure have not been sufficiently investigated. In this study, the turbulent intermittency phenomena in diesel sprays were investigated by using sheet scattered light imaging, focusing on the large-scale vortex structure that affects the formation mechanism of the diesel spray mixture. The intermittency of the diesel spray was investigated by applying the analysis method used for clarifying the phenomenon of turbulent intermittency in free jet flow to the analysis of the diesel spray. In this experiment, the effects of injection pressure on the intermittent behavior of the diesel spray were investigated.

This paper reports the quantitative analysis of vapor concentration in the mixture-liquid two-phase region with Laser Induced Exciplex Fluorescence（LIEF）for the unsteady evaporating gasoline type spray. These methods were used to analyze the mixture-liquid two-phase characteristics in the process of mixture formation. The exciplex fluorescence method, developed by Melton, is a method to optically separate the fluorescence of the liquid and vapor phases, but quantitative analysis of vapor concentration in the mixture-liquid two-phase e region is difficult due to fluorescence cross talk. In this study, the quantitative analysis of vapor concentrations using the average temperature of mixing was used to quantify the vapor concentrations in the mixture-liquid two-phase region by image processing that considers the fluorescence cross talk between the liquid and vapor phases. As a result, the vapor concentration, the temperature of the mixture, and the concentration distribution of the liquid phase in the mixture-liquid two-phase region of the spray cross section were obtained. Based on these results, the correlation diagram between vapor concentration and fluorescence intensity of the liquid phase and the relative frequency distribution of vapor concentration were calculated. A comparison was made between the characteristic values of the fuel and the temperature under the experimental conditions. It was found that the spray consisted mainly of a region where the liquid phase was almost absent and dilute vapors were formed, and a region where the liquid phase was present and formed dense vapors. The same analysis was performed to evaluate the process of vaporization of the spray mixture at different times from the start of injection.

In this study, spray characteristics of waste cooking oil, bio-hydro fined diesel oil and n-tridecane are reported. Bio-hydro fined diesel oil (BHD) is known as a second generation fuel made from bio hydro finning process. The results of chemical properties from the hydro finning process in vegetable oils are nearly the same as diesel oil. BHD has low viscosity and high oxidation stability which is better than the trans-esterification process of biodiesel (FAME). The experiments were conducted in a constant volume chamber in the room temperature for non-evaporating and 400, 500 and 600 K for evaporating. The pressure injections in the room temperature were varied from 50, 100 and 150 MPa. Then, the pressure injection for evaporating was 100 MPa respectively. The results show that the spray tip penetration in non-evaporating and evaporating conditions of waste cooking oil is higher than BHD oil and n-tridecane. Nevertheless, the spray angle of waste cooking oil is smaller than BHD oil and n-tridecane. These results imply due to the high viscosity and density in waste cooking oil.

Fossil fuel dependency in developed countries is worrisome due to the lack of energy security that traditional energy generation provides. In order to prevent future energy problems and to maintain a sustainable society, some countries are starting to develop renewable energy sources. In this research, biomass energy is introduced as a solution not only to reduce fossil fuel dependency, but also to improve municipal solid waste management. The purpose of this report is to construct a distributed power generation system combining the superheated steam gasification of solid waste and photovoltaic panels, and to verify the feasibility of generating power at the consumption site. It also focuses on optimizing the current waste superheated steam gasification system and compares the superheated steam gasification technology with other waste to energy technologies, such as downdraft air gasification and solid waste direct combustion. Finally, the report analyzes the economic, environmental and energetic viability of the above mentioned distributed generation system, which is located in a medium size mall surrounded by a community of 20,000 inhabitants. As a result, it was found that a distributed generation system composed by waste superheated steam gasification and photovoltaic panels is perfectly feasible, since its long term economic performance shows high profitability.

In this study, the novel flame synthesis method using flash boiling spray is proposed in order to form the homogeneous characteristics nanoparticle. In this method, the precursors are injected and the injected precursors are evaporated by flash boiling. The evaporated precursors form vapor and the nanoparticles are formed at high temperature with flame. The factors for homogeneous characteristics of nanoparticles are precursor, flash boiling spray, flame characteristics and nozzle. These factors affect each other and affect to the nanoparticle characteristics as diameter distribution and crystal characteristics. It is necessary to optimize these factors to form homogeneous characteristics particles. In the previous study, TiO2 nanoparticles were formed and the relationship between the flame and injection characteristics, and the particle characteristics were investigated. From the result, the equivalence ratio affects to the nanoparticle crystal characteristics and injection condition affect to the particle diameter and mass fraction of anatase phase. In this paper, TiO2 nanoparticles were produced and the particle property influenced by ambient pressure and particle trapping position is investigated. As the result, the mass fraction of TiO2 anatase phase decreases by increasing ambient pressure. The rutile phase is formed at the short nanoparticle trapping position. The factors such as precursors, injection condition and fuel/oxygen flow ratio for producing the anatase phase particle in this method was discussed.

The nanoparticles whose diameter is less than 100 nm are used as the ceramics, electrical material and cosmetics. It is important to produce homogeneous characteristics of the particles for high performance property. The particle generation method to form homogeneous characteristics is difficult. The nanoparticle generation method with the flame has several advantages such as easy to accomplish high temperature by using simple apparatus construction and continuous produce. The authors proposed that the novel nanoparticle synthesis method by using flashing spray with flame in order to improve the problems. In this method the precursor and low boiling point organic solvent mixed solution is used as the start solution to improve the characteristics of the precursor evaporation characteristics. The injected solution from the nozzle is evaporated by flash boiling and form the homogeneous vapor. The nanoparticles are produced by the combustion energy of the flame. In this paper, the relationship between the flame and injection characteristics, and TiO2 particle characteristics were investigated to demonstrate the method. As the result, the particle distribution has two peaks as 0.1 and from 1 to 3 μm when the low injection frequency and the anatase phase of mass fraction increases by increasing injection frequency. The particle diameter distribution has wide distribution in the case of high equivalence ratio because the aggregation is promoted. The anatase phase of mass fraction changes at the equivalence ratio equal to 0.4, drastically.

A large amount of energy is consumed by people around the world. Most of the consumed energy is originated from fossil resources of which deposits are limited. Therefore, it is necessary for a sustainable society to use energy without waste. Fuel Cell (FC), which supplies energy effectively by Co-generation, attracts attention as a high-efficient distributed energy device for residential use. However, FCs are generally operated with City gas derived from fossil resources. Then, a FC system using hydrogen (H2) fuel produced by Photovoltaic power generation (PV) is proposed. The FC is driven with H2 generated from “surplus power”, which comes from the gap between PV output and electricity demand in residence. This PV-FC combined system approaches energy independence in the residence because consumed electric and thermal power generated by PV and FC originates from solar energy. In this study, PV and Solid Oxide Fuel Cell (SOFC) combined system (PV-SOFC system) is discussed. A SOFC, which has the highest electrical efficiency among FCs, can accept mixed fuel of H2 and City-gas. Additionally, heat-to-power ratio of SOFC output may be able to be controlled by changing H2 concentration of the mixed gas fuel. Thus, it is possible to realize the energy supply synchronizing the each variation of electricity and heat demand in residence. In this paper, the energy reduction by introducing a heat-to-power ratio controllable PV-SOFC system to a residence is simulated. The results show that primary energy consumption in the PV-SOFC system is reduced by 53.8 % for a year.

In this study, we propose a Photovoltaic power generation (PV) and Fuel Cell (FC) hybrid system for residential use to reduce consumption of energy originated from fossil resources. In the hybrid system, FC supplies electricity and heat into residence with hydrogen fuel, which is produced by power of PV installed at house. So, consumed energy is generated by PV and FC which are operated with renewable energy. Therefore, energy independence in residence is approached with applying the proposed system. In the first report of this study, primary energy consumption in PV and Solid Oxide Fuel Cell (SOFC) combined system were calculated by simulation with optimizing method. The results of the first paper showed that the energy reduction of PV-SOFC combined system was larger than the sum of those in PV only and SOFC only system. In this second paper, energy saving performance and cost of PV -SOFC are compared with other energy systems —PV -Battery system in which PV power is stored as electrical energy, and PV-EHP system in which power of PV is converted into hot-water as thermal energy, to evaluate the effectiveness to store PV power as hydrogen energy in PV-SOFC system.

Co-generation system and district heating and cooling system have been applied to urban areas to realize a low-carbon society. However, CO2 emissions from operation division including commercial buildings are still on the increase. Hence researches of micro grid have been conducted as one of the countermeasures to realize a low-carbon society. Here, it seems that the district heating and cooling system is operated effectively under the urban site micro grid network. Thus in this report, a combined system composed of micro grid network and district heating and cooling was investigated to minimize CO2 emissions with a variation of a combination of energy saving systems. The combined system in this study interconnected 3 commercial-scale utility customers with different electric demands and thermal demands. In addition, a conventional energy supply system and district heating and cooling were selected as subjects of comparison with the combined system. Furthermore, 4 kinds of heat-to-power ratio were set by changing the total floor space of each building. In these conditions, annual CO2 emission from each energy supply system was simulated by using a numerical software GAMS/BARON. The calculated CO2 emission was compared with one another in each heat-to-power ratio.

The power generation system by waste biomass has lately attracted attention. The system can convert waste biomass such as garbage, paper and wood into energy. As a result, regional energy independence ratio of area increases. However, conditions of waste biomass are different from their properties, so it is difficult to use as a fuel. Superheated steam gasification system is one of the effective energy conversion systems in order to available wide range of waste biomass. Waste biomass consumes a lot of energy so as to make superheated steam. Then, it is necessary to take account from the collection and transport to power generation process in order to evaluate CO2 emission totally by means of Life Cycle Assessment (LCA). Therefore, this study proposes modeling analysis for LCA by the waste energy by means of superheated steam gasification system. In this paper, it was evaluated that the effect of processing speed of gasification, population, waste biomass ratio, and boiler fuel on energy balance, CO2 emission and cost in residential area. It was obtained that the optimal processing speed of gasification effects on utilization method of carbonization gas and waste biomass ratio. As a result of LCA, energy independence ratio is improved and CO2 emission is reduced by use of carbonization gas. However, total energy conversion efficiency and surplus power are reduced.

In port fuel injection (PFI) gasoline engines, combustion fluctuations are caused by the interaction of various factors during ignition. Variations in the fuel deposition on the intake port walls cause fluctuations in the fuel supply to the combustion chamber and in the fuel concentration distribution, which causes knocking. In addition, when a large amount of fuel deposition occurs, it flows into the cylinder in liquid form without vaporizing, generating unburned hydrocarbons. In the previous report, we confirmed that the fuel adhesion amount on the port wall can be reduced by increasing the fuel injection pressure. In this paper, we investigated fuel atomization under even higher injection pressure conditions than the injection pressure range commonly used in intake port injection, with the aim of further reducing the amount of adhesion. In this paper, shadowgraph photography and Super High Spatial Resolution Photography were used to visualize and measure the free-spray jet morphology and atomization characteristics. The effect of high injection pressure to like direct injection, which on the Jet configuration and atomization characteristics of the spray. The results showed that the droplet diameter changed significantly from 1 to 3 MPa (Wavy region) to 4 MPa (Spray region), but no significant change was observed after 8 MPa (Spray region, Spray region with secondary breakup), and that the droplet diameter did not decrease after 8 MPa. [ABSTRACT FROM AUTHOR]

A breakup model used in spray combustion simulations was developed to predict the breakup process of spray droplets, which has large influences on the mixture formation and the combustion process in internal combustion engines. Taylor Analogy Breakup (TAB) Model is widely used as a droplet breakup model. Improved TAB (ITAB) Model has been developed by improving model constants and the breakup/non-breakup boundary condition of TAB Model. ITAB Model reproduces the dimensionless breakup time based on the observation results of the single droplet breakup behavior and CFD simulation results. In this study, calculation methods of droplet diameter and droplet velocity after breakup in ITAB Model are modified to avoid fitting model constants during spray analysis. Droplet diameter after breakup is determined by calculating Sauter Mean Diameter and using the droplet diameter distribution after breakup based on the observation results of the single droplet breakup behavior. The calculation constant for Sauter Mean Diameter is a function of Weber number to reproduce the breakup phenomenon of single droplets. Droplet velocity after breakup is calculated based on the energy conservation law of droplets used in Enhanced TAB Model. This model shows that Sauter Mean Diameter after breakup is almost same and perpendicular motion of droplets after breakup is more active than TAB Model. This model also considers the effects of the fuel physical properties on breakup characteristics. Model analysis shows that droplet diameter after breakup of the high boiling point component fuel is larger under same conditions and the effect of temperature change is larger than that of the low boiling point component fuel. [ABSTRACT FROM AUTHOR]