NATURAL GAS COMBUSTION INSIDE A CONFINED VOLUME CHAMBER USING GAS-JET IGNITION METHOD

The demand for natural gas is increasing since recent climate change. Natural gas is considered an abundant energy source with low greenhouse-gas emissions. A natural gas engine usually operates in lean-burn mode to gain the advantage of high thermal efficiency and low nitrogen oxides emission. Aproblem typically associated with natural gas combustion in lean mode is poor ignitability. The objective of this study is to improve ignitability of lean natural gas combustion using gas-jet ignition method. Several experiments were done using a confined volume chamber apparatus. Images of the combustion flame were captured using a high speed camera, and hydrocarbon emissions were measured. The result showed that the gas-jet ignition method is effective in improving ignitability of lean natural gas mixture. A addition of 30% hydrogen gas to the natural gas fuel improves both the ignitability and further flame propagation, thus lowering the hydrocarbon emission

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

The objective of this study is to apply neat biomass fuel to a DI diesel engine and investigate the effect of in-cylinder gas flow and combustion on the deposit formation and the fuel dilution in lubricating oil. The study focuses on the low load combustion and emissions considering that low load exhaust contain much unburned fuels and the unburned fuels are the source of the deposit formation and the fuel dilution. Piston configuration and swirl velocity were altered in the engine test. The engine was fueled by neat rapeseed oil. The test was carried out through the four hours continuous engine operation with keeping low load. After the operation, state of deposit formation and fuel dilution in lubricating oil were investigated. Results indicate that Re-entrant piston which creates strong reverse squish and high swirl forms the deposit annular on the piston top. Toroidal piston easily produces deposit on the undersurface of cylinder head. The deposit in the cavity accumulates where initial rapeseed oil spray impinges regardless of piston types. The carbonization of the deposit is promoted on the wall surface where the burned gas with high temperature and high velocity comes into contact. It is important to avoid extremely strong reverse squish to the cylinder liner in order to control the fuel dilution. The deep-bowl chamber changes the direction of reverse squish from the cylinder liner direction to the cylinder head direction. The low velocity outflow from the piston cavity reduces the adhesion of unburned fuel on the cylinder liner, resulting in the smaller amount of unburned fuel scraped off by a piston ring

サンカ テツケイ ネンショウ ショクバイ ノ ディーゼル ハイキ ガス ショリ ギジュツ エノ オウヨウ

Iron oxides which were supported on three kinds of alumina (γ-Al2O3, χ-Al2O3 and activated-Al2O3) were prepared for oxidation catalysts on an after-treatment system of diesel engine. In methane oxidation experiment, we found that the hematite (α-Fe2O3), which was synthesized from goethite (α-FeOOH), supported on χ-Al2O3 has the highest catalytic activity (over 70% in CH4 conversion) at 227K than the other catalysts. Also in the redox reaction between NOx and activated-carbon as substitute for soot, the catalyst supported on χ-Al2O3 showed the highest performance and CO gas was not observed in the products. It is concluded that in α-Fe2O3/χ-Al2O3 catalyst, α-Fe2O3 exists mainly on the surface of the support, because of flatness of the surface of χ-Al2O3. On the other hand, in the case of α-Fe2O3/γ-Al2O3 catalyst, as the surface of support, γ-Al2O3, is uneven, α-Fe2O3 do not partially exist on the surface but in the pores

Two-dimensional temperature measurement in a high temperature and high pressure combustor 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 1335-1375nm has been applied to a combustor for 2D temperature measurement in high temperature of 300-2000K and high pressure of 0.1-2.5MPa condition. An external cavity type laser diode with wide wavelength range scanning at 1335-1375nm was used to evaluate the broadened H2O absorption spectra due to the high temperature and high pressure effect. The spectroscopic database in high temperature of 300-2000K and high pressure of 0.1-5.0MPa 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

Analysis of Straight Vegetable Oil (SVO) Spray Characteristic and Droplets Distribution By Using Nano-Spark Shadowgraph Photography Technique

Abstract - Biofuel is an alternative fuel to reduce the dependent on fossil fuel due to the limited oil stock and increment of oil prices. Straight vegetable oil (SVO) has several superior combustion characteristics such as less hydrocarbons, carbon monoxide and particulate matter compared to diesel fuel. More advantages are high biodegradability, excellent lubricity and no sulfur content. During combustion, approximately 10wt% of its oxygen content promote more complete combustion process and effectively reduce unburned hydrocarbons (UHC), carbon monoxide (CO) as well as suspended aerosol carbon granules. However, high kinematic viscosity of SVO affects the spray characteristics thus effect the engine efficiency. In this study, the effect of kinematic viscosity of SVO on fuel injection spray characteristic are investigated using constant volume high pressure spray chamber and nano-spark shadowgraph photography technique

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

Lifted flames in combustion furnaces are diluted with burned gas entrained into the fuel jet. The reduced concentrations of reactants resulting from this dilution increase the liftoff height, while the associated temperature increase decreases the height. The aim of the present study was to develop a premixed model capable of predicting the variation in the liftoff height resulting from entrainment. A triple concentric burner incorporating fuel gas, oxidizer and co-flow gas nozzles was employed to simulate a combustion furnace. Prior to combustion tests, the fraction of the fuel gas in the non-reactive jets forming on the burner was determined, to allow an evaluation of parameters affecting the entrainment rate of the co-flow gas. The flame liftoff height above the burner was found to increase with decreases in the O2 concentration in the co-flow gas and was decreased with increases in temperature. Three premixed models were examined: a conventional premixed model, a DP1 model including only the effect of decreasing reactant concentrations and a DP2 model including the effects of both decreasing concentrations and temperature increases. Validations of these models demonstrated that the conventional model failed to predict variations in the liftoff height at a variety of co-flow gas O2 concentrations and temperatures. The DP1 model also provided insufficient correlations between the bulk velocity and liftoff height, such that the correlation line at a high co-flow gas temperature separated from that at room temperature. In contrast, the DP2 model provided excellent correlations in conjunction with different virtual origin positions

Project toward development of industrial application on laser diagnostics

The demands for lowering the burdens on the environment will continue to grow steadily. It is important to monitor controlling factors in order to improve the efficiency of industrial systems and machinery such as engines, boilers and gas turbines. In particular, detailed measurement techniques for their parameters such as temperature and species concentrations are necessary to elucidate the overall nature of industrial systems. In Tokushima University the project named “Development of Industrial Applications on Laser Diagnostics (DIALD)” has been promoted for the purpose of elucidating the mechanisms and improving the efficiency of engines, boilers, gas turbines and so on. In this project, laser diagnostics such as computed tomography-tunable diode laser absorption spectroscopy (CT-TDLAS), laser-induced breakdown spectroscopy (LIBS), Raman spectroscopy and time-of-flight mass spectrometry (TOFMS) have been developed and applied to practical industrial fields. A consortium on CT-TDLAS including 11 institutes (2015 fiscal year) has also been organized and several joint researches have been performed toward practical applications. This report shows the research results of CT-TDLAS in the field of combustion analyses and applications to engines, boilers and gas turbines are discussed as a part of applications in the DIALD project

Analysis of Straight Vegetable Oil (SVO) Spray Characteristics at End of Injection (EOI)

The depletion source and the increasing demand of fossil fuel have prompted scientists and researchers to search new alternative fuels for diesel engine. Biodiesel is seen a promising alternative fuel to reduce dependent on conventional diesel fuel. Advantages of biodiesel compared to petroleum-based diesel include high biodegradability, excellent lubricity, higher flash point, no sulfur content and produces less air pollutants. Although biodiesel has many advantages on the fuel properties, the fuel consumption rate or lower horsepower output are still need to be improved. This is due to the differences in fuel properties especially the kinematic viscosity between diesel fuel (GO), biodiesel fuel (BDF) and straight vegetable oil (SVO). In this study, the effect of kinematic viscosity of SVO on the spray behavior at End of Injection (EOI) were investigated. High kinematic viscosity of fuel highly affects the spray characteristics at EOI. In additional, high injection pressure and high kinematic viscosity of SVO apply resistance at nozzle inner hole caused needle lift cannot completely close the nozzle at EOI signal. At the EOI in which the combustion temperature inside chamber reduces promptly, many fuel droplets could not undergo a complete atomization process especially for large size of diameter fuel droplets. This phenomenon result the development of carbon deposition around the nozzle tip area and it will cover the nozzle hole. The development of carbon deposition will affect the fuel flow from nozzle. This study indicates that fuel injection pressure show no effect on SVO spray characteristics at the end of injection. Furthermore, high ambient temperature spray will reduce the kinematic viscosity value of SVO and could improve SVO spray atomization at end of injection

An investigation into the relationship between the formation of thermal cracked components and PM reduction during diesel combustion using water emulsified fuel

Water-in-diesel emulsion fuel (W/O) operated in diesel engines, shows a significant reduction of particulate matter (PM). In this paper, PM reduction characteristics by thermal decomposition of W/O10 and W/O20 (10vol.% and 20vol.% of water in W/O respectively) are identified in diesel combustion atmosphere using a plug flow reactor with a co-flow diffusion burner. To analyze initial thermal decomposition at diesel diffusion combustion, the W/O fuels are thermally decomposed in the plug flow reactor first, then the thermally decomposed W/O fuels are introduced into a co-flow diffusion burner as fuel and PM are generated. In high temperature atmosphere without oxygen in the reactor, W/O10 and W/O20 are thermally decomposed and both of them almost produce light hydrocarbons (LHCs) higher than a diesel fuel, which means thermal decomposition before combustion are encouraged by the W/O. Excitation-emission matrix (EEM) method shows that polycyclic aromatic hydrocarbons (PAHs) are produced by both W/O fuels and diesel fuel during the thermal decomposition period but some W/O fuels oxidize a huge amount of PAHs in the later diffusion combustion. CO, CO2 measurements after the combustion of the thermal decomposed substances in the diffusion burner via high temperature reactor reveal that diffusion combustion of W/O fuels contribute to Soluble Organic Fraction (SOF) and Solid reduction which leads to reduction of CO and increase of CO2 respectively