Effects of spacing between fuel and oxidizer nozzles on NOx emission from spray combustion furnace operating under various oxidizer temperatures


Four-step global kinetics mechanism for diluted combustion fueled with kerosene


Effect of Pilot Injection on Improvement of Fuel Consumption and Exhaust Emissions of IDI Diesel Engines


Modeling of liftoff heights of non-premixed turbulent flames in co-flows having various temperatures and O2 concentrations


Characteristics of Heat Release History of Multi-Hole Diesel Spray Affected by Initial Mixture Formation, Wall Impingement and Spray Interaction


Effects of inversed-delta injection rate on late combustion and soot emissions from diesel combustion in a constant-volume chamber


Two-dimensional temperature measurement in a high temperature and high pressure combustion using CT-TDLAS with a wide scanning laser at 1335-1375nm

Tunable diode laser absorption spectroscopy (TDLAS) technology is a developing method for temperature and species concentration measurements with the features of non-contact, high precision, high sensitivity, etc. The difficulty of two-dimensional (2D) temperature measurement in actual combustors has not yet been solved because of pressure broadening of absorption spectra, optical accessibility, etc. In this study, the combination of computed tomography (CT) and TDLAS with a wide scanning laser at 1335-1375 nm has been applied to a combustor for 2D temperature measurement in high temperature of 300-2000 K and high pressure of 0.1-2.5 MPa condition. An external cavity type laser diode with wide wavelength range scanning at 1335-1375 nm was used to evaluate the broadened HO absorption spectra due to the high-temperature and high-pressure effect. The spectroscopic database in high temperature of 300-2000 K and high pressure of 0.1-5.0 MPa condition has been revised to improve the accuracy for temperature quantitative analysis. CT reconstruction accuracy was also evaluated in different cases, which presented the consistent temperature distribution between CT reconstruction and assumed distributions. The spatial and temporal distributions of temperature in the high-temperature and high-pressure combustor were measured successfully by CT-TDLAS using the revised spectroscopic database.


Effects of Sub-Chamber Configuration on Heat Release Rate in a Constant Volume Chamber simulating Lean-burn Natural Gas Engines

SAE International Journal of Advances and Current Practices in Mobility


Experimental investigation of nitrogen oxide emissions from emulsified fuel combustion incorporating a rapid internal mixing injector by using temperaturetime scaling


天然ガス希薄燃焼エンジンにおける熱効率向上とNOx 低減の両立(第3 報)

天然ガス希薄燃焼エンジンにおける熱効率向上とNOx 低減の両立(第3 報)

Transactions of the Society of Automotive Engineers of Japan


Rapid emulsification of a fuelwater rapid internal mixing injector for emulsion fuel combustion


Effect of low load combustion and emissions on fuel dilution in lubricating oil and deposit formation of DI diesel engines fueled by straight rapeseed oil


Numerical Simulations of Mixture Formation in Combustion Chambers of Lean-Burn Natural Gas Engines Incorporating a Sub-Chamber


天然ガス希薄燃焼エンジンにおける熱効率向上と NOx 低減の両立(第2報，燃焼諸元の影響)


天然ガス希薄燃焼エンジンにおける熱効率向上と NOx 低減の両立(第1報，燃焼コンセプト)


Flame-wall interactions of lean premixed flames under elevated, rising pressure conditions


天然ガス希薄燃焼エンジンにおけるセンタ直噴の効果に関する研究(天然ガスエンジンの熱効率向上)


A 3D DNS Investigation on the Flame-Wall Interactions and Heat Loss in a Constant Volume Vessel


A DNS Study on Global and Local Flame Structures In Thin Reaction Zones


Droplets Behavior and Evaporation of Diesel Spray Affected by Ambient Density after Pilot Injection


CT半導体レーザ吸収法を用いた高温・高圧域における2次元温度分布計測の特性評価

CT半導体レーザ吸収法を用いた高温・高圧域における2次元温度分布計測の特性評価


Effect of Improving Spray Development and Evaporation on Emissions from DI Diesel Engines Fueled with Straight Rape-seed Oil


Effect of the distance between fuel and oxidizer nozzles on NOx emissions from spray combustion furnaces incorporating high-temperature preheated oxidizers

Journal of Thermal Science and Technology


Evaluation of NOx Production Rate in Diesel Combustion Based on Measurement of Time Histories of NOx Concentrations and Flame Temperature


Liftoff heights of turbulent non-premixed flames in co-flows diluted by CO2/N2


Macro- and Micro-scale Observation on Dynamic Behavior of Diesel Spray Affected by Ambient Density and Temperature


Distribution of Two-stage Direct Injection CNG-air Mixture near Lean Limit using CFD


Analysis of diesel spray evaporation process in high density and high temperature atmosphere

高温高密度雰囲気におけるディーゼル噴霧の蒸発過程の解析

Diesel engines, in recent years, come to apply high pressure charging and high EGR to improve engine performance. In this situation, it is important to study on diesel spray behavior and mixture formation under those kinds of condition. This study investigates diesel spray development and micro-scale characteristics of droplets evaporation including atomization under high density and high temperature atmosphere. Experiment was carried out by shadowgraph photography method. Our system has a nano-spark light source to illuminate spray injected into spray chamber. The image analysis can reveal droplets size-distribution and droplets dynamic behavior at spray boundary. Results indicate that, at early stage of injection, high atmospheric density accompanied with high temperature greatly affects droplets atomization and evaporation at spray boundary. High density atmosphere produces small-size droplets. Evaporation of large-size droplets is improved with high density and high temperature atmosphere.

Transactions of The Japan Society of Mechanical Engineers, Series B

日本機械学会論文集(B編)


Effect of Wall Configuration on Atomization of Rapeseed Oil Diesel Spray Impinging on the Wall


Effect of Gas-jet Ignition Technique on the Extension of CNG Lean Combustion Limit


NOx Reduction of Non-Premixed Flames by Combination of Burner and Furnaces

This study proposes an idea of NOx reduction and high efficiency combustion by combination of burner and furnace. This is basically attributed to the use of entrainment of burnt gases to flame in furnace. The entrainment of burnt gases leads the dilution of flame and the recovery of heat to be exhausted. The phenomena are strongly related to the geometry of burner and furnace. The temperature, concentration, and flow field characteristics were investigated for piloted propane non-premixed flames in the cylindrical furnaces in terms of NOx emission. The effects of the furnace inner diameter, D1, air inlet velocity difference, ΔUa, and global equivalence ratio,φ, on NOx emission were investigated. Moreover, two kinds of materials: Pyrex glass and stainless steel were used as the furnace wall to evaluate the radiation effect through the comparison of the flame characteristics. The emission index of NOx, EINOx, decreases roughly with the increase of above parameters. This decrease is observed to be a consequence of dilution by the burnt gases and flame stretch. The dilution is attributed to the recirculation structure, which is formed at the bottom of the furnace. The flame stretch is related to the velocity difference, which is introduced by multiple air inlets. The EINOx of confined non-premixed flame is scaled by the parameter D1UFΔUa, which is proportional to Re,cDa-1. Here, UF is the fuel velocity, Re,c is the furnace Reynolds number reflecting the turbulence in the furnace, and Da is the Damköhler number reflecting the flame stretch. The parameter D1UFΔUa is related linearly to the volume flow rate entrained in to the flame. Thus, this study verified that the EINOx of confined non-premixed flame is dominated primarily from the entrainment of burnt gases by the recirculation vortex and secondarily by the turbulence at the flame boundary, which is generated by the air velocity difference. In addition, it is found that under present experimental conditions, the radiation effect on the EINOx is small and constant with respect to the parameters. Thus, this idea has a potential for practical applications.


Effects of Burned Gas Dilution on the Liftoff Height of Turbulent Non-Premixed Flames (Effects of Reduced Reactant Concentrations through the Burned Gas Dilution)

乱流浮き上がり火炎の浮き上がり高さに対する既燃ガス希釈の影響(希釈による反応物濃度低下の影響)

Objective of this study is to propose a new method to predict liftoff heights of turbulent non-premixed flames in combustion furnaces. At the first stage of this study, we investigated effects of the burned gas dilution of fuel jet on the liftoff height. The burner used consists of co-axial nozzles from which fuel, oxidizer and co-flow gas are issued, respectively. The co-flow gas surrounding the fuel jet simulates burned gases with low oxygen concentration in combustion furnaces. The fuel jet entrains the co-flow gas in the unburned mixing region of the base of lifted flame. The entrainment of co-flow gas decreases the oxygen concentration of mixtures, and hence the laminar burning velocity of premixed flame formed at the flame base decreases. The lower burning velocity lifts up the flame base. Edge flame model and premixed flame model fail to reproduce this phenomenon of liftoff height due to the dilution through co-flow gas entrainment. A dilution ratio is introduced to quantify the magnitude of the dilution. It has found that the dilution ratio can generalize liftoff heights of the turbulent flames diluted through co-flow gas.

日本機械学会論文集(B編)


Flame and Eddy Structures in Hydrogen-Air Turbulent Jet Premixed Flame


平行噴流バーナーを用いた高温空気燃焼の着火遅れに対する既燃ガス希釈の影響

平行噴流バーナーを用いた高温空気燃焼の着火遅れに対する既燃ガス希釈の影響

Objectives of this study are to suggest a new method to predict the stability limit of high temperature air combustion. For the first stage of this study, we investigated the effects of dilution by the burned gas on the ignition delay time. Dilution ratio is introduced to quantify the magnitude of dilution in high temperature air combustion with a parallel jet burner. The effects of dilution on the ignition delay time are evaluated by a chemical characteristic time with the dilution ratio. Flamelet equations are solved numerically to investigate the effects of dilution on the ignition delay time. Ignition time is defined as the time at which a temporal increase in maximum temperature becomes its maximum. The ignition delay time based on the maximum temperature includes durations of radical pool growth and of most reactive region movement. The ignition delay time based on the maximum value of Damköhler number corresponds to the duration of radical pool growth. With an increase in the dilution ratio, the ignition delay time based on the Damköhler number decreases, and then increases. This trend is attributed to the increase in temperature of mixture and the decrease in reactant concentration with the dilution ratio. The introduction of chemical characteristic time has generalized the ignition delay time.

日本機械学会論文集(B編)


乱流拡散燃焼のスカラー確率密度関数法の解析精度 (レイノルズ応力モデルの評価)

乱流拡散燃焼のスカラー確率密度関数法の解析精度 (レイノルズ応力モデルの評価)

日本機械学会論文集(B編)


A Study on Improvement of Diesel Spray Characteristics Fueled by Rape-seed Oil

SAE International Journal of Fuels and Lubricants


Stability Limits of High Temperature Air Spray Combustion

高温空気噴霧燃焼の安定燃焼限界の解明

The objective of this study is to suggest a new method to predict the stability limit of high temperature air spray combustion. For the first stage of this study, behaviors of the high temperature air spray combustion at the stability limit are investigated experimentally. Kerosene was used as fuel and was supplied into the furnace through a fuel-air spray nozzle. Mixtures of air and nitrogen were used as oxidizer and were preheated up to 1023K. The O2 concentration in the oxidizer was changed from 21 % to 9 %. Heat loss in the furnace was controlled by cooling tubes up to 2.3kW. The stability limit was determined on the basis of CO concentrations measured at the exit of furnace. An increase in heat loss shifts the stability limit to higher preheated temperature and O2 concentration conditions. When an experimental condition approaches to the stability limit, the temperature of the recirculated burned gas decreases to consequently lead to the lifted flame. A further decrease in the temperature in the recirculated burned gas delays the ignition of the unburned mixture and increases the liftoff height. This fact indicates that the liftoff height is determined by the temperature and O2 concentration in the recirculated burned gas. At conditions below the stability limit, the liftoff height becomes larger than the position of the core of recirculation vortex. The vortices recirculate both the burned gas and the unburned mixture of vapor fuel and oxidizer. The recirculation of the unburned mixture decreases the temperature in the recirculated gas, thus the ignition does not occur. It has been therefore founded that the use of the temperature and O2 concentration in recirculated burned gas provides a generalization of the stability limit regardless of the variation of heat loss.

Journal of the Combustion Society of Japan


ナノスケールステップにおける接触線挙動に関する分子動力学解析

ナノスケールステップにおける接触線挙動に関する分子動力学解析

日本機械学会論文集(B編)


移動接触線近傍の流れ場に及ぼす液体・固体物性の影響

移動接触線近傍の流れ場に及ぼす液体・固体物性の影響

The flow field near a moving contact line was measured with the particle imaging velocimetry technique. The test liquids of pure water, ethylene glycol (EG), dimenthyl sulfoxide (DMSO) and polydimethylsiloxane (PDMS) of which surface tensions range from 19mN/m to 72mN/m were used with the solid materials of glass, polymethylmethacrylate (PMMA) and polytetrafluoroethylene (PTFE). The combination of these materials varied the contact angle from zero to 90 degrees. Each solid material was withdrawn from each liquid into Ar gas atmosphere at a constant speed of 0.62mm/s. The observed flow fields were qualitatively different from the theoretical ones obtained with a linear model when the test liquid was either of water, EG or DMSO with the contact angle less than 90°. It is found that, for such flow fields, the viscous tangential stress on the gas-liquid interface estimated for the liquid phase is much larger than that for the gas phase. The stress in the liquid phase forces the liquid on the interface to flow toward the contact line. The Marangoni stress induced by inhomogeneous distribution of slight amount of impurity (surfactant) on the gas-liquid interface is the most presumable mechanism which compensates for the difference between the viscous stresses for the both phases on the interface.

日本機械学会論文集(B編)


Characteristics of Gaseous and Liquid Fuel Combustion in Laboratory-scale Furnaces

The flame appearance, temperature profile, and NOx emission associated with gaseous and liquid fuel furnace combustion are investigated through a series of experiments. Numerical simulations are also conducted, for several cases, in order to complement the experimental data. Three fuels, namely, hydrogen, propane, and Jet-A (C12H23), which is a liquid fuel, are examined. Combustion is carried out in two 840-mm long furnaces with diameters of 95 and 182 mm, respectively. Combustion air is introduced to the furnace through two coaxial air nozzles, which generate air velocity difference ΔUa. The flame appearance, temperature profile, and emission index of NOx (EINOx) of gaseous fuel combustion are found to depend strongly on the furnace diameter, D. The results indicate that gaseous fuel combustion can be characterized according to the furnace volume. In addition, the temperature profiles reveal that larger values of D and ΔUa result in lower temperatures. The EINOx is demonstrated to be well scaled with a parameter DUfΔUa. Finally, the normalized EINOx is shown to be inversely proportional to DUfΔUa because of the effects of dilution and flame stretch. However, the vaporization process in liquid fuel combustion appears to weaken the sensitivity of the normalized EINOx of Jet-A combustion on the parameter DUfΔUa.


多変数β関数を用いた仮定確率密度関数法に基づく乱流拡散火炎のモデリング

多変数β関数を用いた仮定確率密度関数法に基づく乱流拡散火炎のモデリング

A numerical simulation based on a moment method is conducted to investigate the feasibility of two assumed probability density function (PDF) approaches in the configuration of a turbulent jet nonpremixed flame. In this study, two multivariate β probability density functions with respect to P(T, Y) and P(h, Y) are employed to account for the turbulence-chemistry interaction. The former assumes the independency of temperature and concentration, and the latter assumes the dependency of enthalpy and concentration. The reaction mechanism is a single-step irreversible reaction including H_2, O_2 and H_2O species. Results are compared with those from measurements and a combined PDF/moment method, which a detailed reaction mechanism was applied. Velocity distributions obtained by the present approaches have shown good agreement with the results of measurements and the combined PDF/moment method. The present approaches provide good prediction in terms of mean scalar field. Variance of each scalar quantity is evaluated better by P(h, Y), but underestimated by P(T, Y). Thereby the probability density function of enthalpy and concentration is preferable for the evaluation of mean reaction rate.

Transactions of The Japan Society of Mechanical Engineers, Series B

日本機械学会論文集(B編)


The Effect of Distance between the Fuel and Air Nozzles on NOx Emission from High Temperature Air Combustion

高温空気燃焼のNOx排出特性に対するノズル間隔の影響

For the high temperature air combustion (HiTAC), fuel nozzles are commonly located away from an air nozzle. The emission of NO_x from the HiTAC furnace is thought to be related to the distance between these nozzles (ΔL). Objectives of present study are to clarify the effect of ΔL on the NO_x emission. Measurements of the NO_x emission are made in the cylindrical furnace. Propane is issued from the two nozzles located at three different distances from the air nozzle. Preheated temperature of air is up to 1263K. The emission index of NO_x (EINO_x) decreases as an increase in ΔL. The large ΔL enhances the dilution by the burned gas, which leads to a decrease in flame temperature. The decrease of EINO_x is attributed to the decrease in flame temperature. The EINO_x characteristic is evaluated by the residence time and flame temperature. Dilution ratio is introduced to quantify the magnitude of dilution by the burned gas. The flame temperature is predicted by the modified flamelet model with the dilution ratio. The residence time and the dilution ratio are as a function of ΔL. The overall NO_x production rate is found to scale with the flame temperature predicted by the modified flamelet model.

日本機械学会論文集(B編)


An Experimental Study of Flame Characteristics of Jet Diffusion Flames in Cylindrical Furnaces 3rd Report, Effect of Flow Field on NOx Emission Properties

円筒形燃焼炉内の噴流拡散火炎の燃焼特性に関する研究(第3報, NOx排出特性に対する流れ場の影響)

日本機械学会論文集(B編)


A Numerical Study on the Optimum Fuel Split-Injection Scheme Configuration in a Constant-Volume Chamber

The effects of diesel fuel split-injection on the fuel-air ratio and the gas velocity distribution inside the combustion chamber are numerically investigated using a modified KIVA-3V code that incorporates an Enhanced Taylor Analogy Breakup (ETAB) model into the calculation of spray droplet breakup. The second injection in the split-injection scheme can generate a sudden increase in the flammable mixture area inside the chamber. Among the schemes evaluated, the split-injection configuration in which 75% of the fuel mass is injected during the first injection and the remaining fuel mass is injected after a 1.0-ms dwell is preferred as the optimum configuration with respect to particulate emission reduction. The configuration tends to produce the widest flammable area inside the chamber during the mixing-controlled combustion phase. The dwell duration in split-injection schemes does not have a linear correlation with the area of the flammable mixture. The gas velocity distributions do not change significantly when the fuel injection mass ratio and dwell duration are varied.


Effect of Flow Field on NOx Emission Properties of Jet Nonpremixed Flames in Cylindrical Furnaces

The flow field characteristics of confined flames have been investigated for propane nonpremixed flames in cylindrical furnaces. The effects of furnace inner diameter D1, air inlet velocity difference ΔUa, and global equivalence ratio φ on the flow field are related to NOx emission. The emission index of NOx, EINOx, decreases roughly with the increases of the above parameters. This decrease is observed as a consequence of flame stretch and dilution by the burned gas. The flame stretch is related to the velocity difference introduced by multiple inlets, and the dilution is attributable to the recirculation structure formed at the bottom of the furnace. The present investigation shows the mechanism of burner/chamber configuration inciting the flow field and indirectly controlling NOx emission.


Local Flame Structure of H2/Air Turbulent Premixed Flames at Different Reynolds Number


Effect of Turbulence Characteristics on Local Flame Structure of H2-Air Premixed Flames


水素・空気乱流予混合火炎における乱流と火炎の相互作用

水素・空気乱流予混合火炎における乱流と火炎の相互作用


水素・空気乱流予混合火炎の局所構造

水素・空気乱流予混合火炎の局所構造

日本機械学会論文集(B編)