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Raman spectrometers are studied and developed for the military purposes because of their nondestructive inspection capability to capture unique spectral features induced by molecular structures of colorless and odorless chemical warfare agents(CWAs) in any phase. Raman spectrometers often suffer from random noise caused by their detector inherent noise, background signal, etc. Thus, reducing the random noise in a measured Raman spectrum can help detection algorithms to find spectral features of CWAs and effectively detect them. In this paper, we propose a denoising autoencoder for Raman spectra with a loss function for sample efficient learning using noisy dataset. We conduct experiments to compare its effect on the measured spectra and detection performance with several existing noise reduction algorithms. The experimental results show that the denoising autoencoder is the most effective noise reduction algorithm among existing noise reduction algorithms for Raman spectrum based standoff detection of CWAs.

A matched filter (MF) is one of the most widely used detectors for the detection of chemical agent (CA) clouds in the passive hyperspectral imaging system. To improve the detection performance of the MF, a linear cooperation scheme that allocates cooperation coefficients to the spectra of the neighbouring pixels is proposed. The optimal cooperation coefficients, which removes noise signatures whilst minimising the distortion of CA signatures, are acquired by finding the maximum likelihood estimator of the cooperation coefficients. It is proved that a moving average scheme that assigns the same coefficients is the optimal cooperation scheme. Finally, a cooperative MF with the optimal cooperation scheme is designed. It is demonstrated that the proposed cooperative MF is capable of robust detection performance via outdoor experiments with actual CA data measured by a Bruker HI‐90 instrument.

To analyze the combustion and exhaust characteristics of internal combustion engines, it is important to analyze combustion phases, such as ignition delay, premixed combustion period, and d...

The purpose of this paper is to investigate the effects of using gas to liquid (GTL)-biodiesel blends as an alternative fuel on the physical properties as well as the combustion and emission reduction characteristics in a diesel engine. In order to assess the influence of the GTL-biodiesel blending ratio, the biodiesel is blended with GTL fuel, which is a test fuel with various blending ratios. The effects of GTL-biodiesel blends on the fuel properties, heat release, and emission characteristics were studied at various fuel injection timing and blending ratios. The test fuels investigated here were GTL, biodiesel, and biodiesel blended GTL fuels. The biodiesel blending ratio was changed from 0%, 20% and 40% by a volume fraction. The GTL-biodiesel fuel properties such as the fuel density, viscosity, lower heating value, and cetane number were analyzed in order to compare the effects of different mixing ratios of the biodiesel fuel. Based on the experimental results, certain meaningful results were derived. The increasing rate of the density and kinematic viscosity of the GTL-biodiesel blended fuels at various temperature conditions was increased with the increase in the biodiesel volumetric fraction. The rate of density changes between biodiesel-GTL and GTL are 2.768% to 10.982%. The combustion pressure of the GTL fuel showed a higher pressure than the biodiesel blended GTL fuels. The biodiesel-GTL fuel resulted in reduced NOx and soot emissions compared to those of the unblended GTL fuel. Based on the experimental results, the ignition delay of the GTL-biodiesel blends increased with the increase of the biodiesel blending ratio because of the low cetane number of biodiesel compared to GTL. As the injection timing is advanced, the NOx emissions were significantly increased, while the effect of the injection timing on the soot emission was small compared to the NOx emissions. In the cases of the HC and CO emissions, the GTL-biodiesel blended fuels resulted in similar low emission trends and, in particular, the HC emissions showed a slight increase at the range of advanced injection timings.

The purpose of this paper is to investigate the effects of blending ratio of Karanja oil methyl ester (KOME) on spray characteristics and to analyze the engine performance and exhaust emissions of Karanja biodiesel blend vis-a-vis baseline diesel. Spray characteristics were analyzed using injection rate and spray visualization experiments for the following injection pressures: 50, 100 and 150 MPa. Engine performance, emission and combustion characteristics were also investigated at various engine operation conditions. From a comparison of the spray evolution of Karanja biodiesel 40% (v/v) blend (KB40) vis-a-vis baseline diesel, the spray shape revealed a narrower and deeper penetrating spray development process for KB40. However, at an ambient pressure of 4 MPa, which is considered to be similar to the cylinder pressure of a test engine, KB40 exhibited a spray evolution behavior (spray penetration and shape) closely resembling that of diesel. In the engine experiment, lower max torque, brake thermal efficiency (BTE) and exhaust gas temperature, in addition to higher brake-specific fuel consumption (BSFC) were observed for biodiesel blend compared to diesel due to lower heating value of Karanja biodiesel.

Main objective of this study was to demonstrate endoscopic visualization of combustion events in the combustion chamber of a production grade compression ignition (CI) engine. High speed endoscopic imaging was used to provide qualitative information about the in–cylinder combustion for mineral diesel and biodiesel fueled engine operating at different engine loads. These images were analyzed using image processing program developed in MATLAB, in order to determine the ‘start of combustion’ (SoC), ‘spatial soot distribution’ and ‘spatial flame temperature distribution’. In–cylinder pressure and rate of heat release (RoHR) were validated using simulation results obtained by using a KIVA-3V code. The luminosity of flames in the combustion images was relatively lower for biodiesel compared to baseline diesel. Area of soot distribution decreased in later stages of combustion for both test fuels, which indicated superior oxidation of soot particles formed, during the post combustion events. Biodiesel showed relatively lower dissipation of heat, which caused lower soot radiations in the flames. Simulated soot distribution and flame temperature distribution obtained from KIVA-3V code also showed similar behavior and verified the trends observed by combustion chamber endoscopy.

There is an urgent need for detailed comparative engine performance assessment of alternative fuels such as biofuels vis-a-vis conventional gasoline and diesel. Single cylinder genset engines are widely used in developing countries in very large numbers in agriculture and decentralized power generation sectors, therefore such a detailed understanding becomes even more important. In this study, the effects of change in fuel on noise, vibrations, and engine combustion characteristics of a single cylinder genset engine are investigated. Three different test fuels; mineral diesel, Jatropha biodiesel (JB100), and Jatropha biodiesel-diesel blend (JB20) were used. Spray characterization studies were also conducted and it was found that the spray penetration length, and spray cone angle are strongly influenced by ambient pressure for all the three test fuels. These parameters are not significantly different, especially at higher ambient pressures (1 MPa, and 2 MPa) for different test fuels. The study shows that the variation of HRR max and combustion duration for test fuels correlates well with our measurements of combustion noise and vibrations. A higher value of HRR max corresponds to higher levels of combustion noise.

An experimental study was carried out for assessing noise, vibrations, combustion, and spray characteristics and associated correlations using a single cylinder compression ignition engine. Such engines are typically used in genset and agricultural farm machinery. Tests were conducted from no load to full load using three different test fuels; Karanja biodiesel, 20% (v/v) Karanja biodiesel blend and baseline mineral diesel. Spray visualization experiments were conducted in a constant volume spray chamber using a mechanical fuel injector, similar to the one used in the test engine. Engine combustion noise as well as overall engine noise measurements were carried out using a microphone. Three different accelerometers were used to measure engine vibrations in pistonic, longitudinal and lateral directions. Combustion noise was found to be highest for 20% biodiesel blend was correlated to shorter combustion duration, increased ignition delay, and higher heat release rate. Vibration levels in the pistonic direction were found to be highest for KB20 fuelled engine. External engine noise measured by microphone was higher for KB100 at almost all loads compared to other test fuels. However, such a divergence was attributable to other sources of noise, which were not related to the combustion process. Finally, spray investigations for different test fuels showed maximum spray penetration for KB20, and the least for baseline mineral diesel. These observations were also consistent with other observations related to combustion noise, ignition delay, and heat release rate.

Internal combustion engine research on alternative fuels has gained momentum because of growing awareness about energy security and environmental issues worldwide. Biodiesel offers an ideal solution to these problems and is an excellent partial replacement to mineral diesel. In this study, Karanja biodiesel blended with mineral diesel has been investigated for macroscopic spray characterization vis-à-vis baseline mineral diesel by varying fuel injection pressures (50, 100 and 150 MPa). Spray developed with relatively narrower spray angle for KB20. Injector needle movement for energizing and real injection durations were also compared for diesel and KB20 at fuel injection pressures of 50, 100 and 150 MPa. Needle movement was slightly higher for KB20 because of its relatively higher viscosity. However, with increasing fuel injection pressure, the difference reduced and showed quite similar results. A 2.2 L common rail direct injection sport utility vehicle EURO-IV diesel engine was used for the experiments. Engine performance, emissions and combustion characteristics of KB20 were compared with baseline mineral diesel at (1) the rated engine speed (2500 r/min) with varying engine loads as well as (2) at the rated load at varying engine speeds (1500–3500 r/min). Brake thermal efficiency of KB20 was lower than mineral diesel. Brake-specific carbon monoxide and carbon dioxide emissions decreased with increasing brake mean effective pressure and showed increasing trend with increasing engine speeds. KB20 showed emission of higher number of particles compared to mineral diesel at all engine operating conditions. Higher oxygen content of biodiesel resulted in shorter ignition delay and slightly higher peak cylinder pressure. KB20 showed relatively longer combustion duration compared to mineral diesel at 2500 r/min engine speed.

In this article, the spray atomization characteristics, combustion performance, and emissions reduction characteristics of a biodiesel-fueled compression ignition (CI) engine are reviewed, including physical fuel properties such as the oxygen content, density, viscosity, and cloud point. Different fuel properties of biodiesel such as higher oxygen content and cetane number induce shorter ignition delay, improved combustion efficiency, and reduction of emissions. However, higher viscosity causes coarse atomization, and a higher cloud point indicates that the fuel injection system needs to be modified. A slightly shorter injection delay was observed due to the low compressibility of biodiesel, and the production of biodiesel spray is similar to that of diesel spray despite having different fuel properties. The higher surface tension of biodiesel results in a higher SMD distribution, and thus the droplet momentum of biodiesel, which is related to the spray velocity, is greater than that of diesel fuel. A lower maximum combustion pressure and indicated mean effective pressure (IMEP) were observed for biodiesel fuel due to its low heating value. Biodiesel combustion with exhaust gas recirculation (EGR) shows a higher combustion pressure and rate of heat release than those of diesel fuel due to its oxygen content. This oxygen content induces reduced HC, CO, and PM emissions, but there is an increase of NO X emission. However, a high EGR strategy can reduce the NO X emission in biodiesel-fueled CI engines.

In this study, we investigated the effect of biobutanol and biobutanol–diesel blends on the combustion and emission characteristics in a four-cylinder compression ignition engine using pilot injection strategies. The test fuels were a mixture of 10% biobutanol and 90% conventional diesel (Bu10), 20% biobutanol and 80% diesel (Bu20), and 100% diesel fuel (Bu0) based on mass. To study the combustion and emission characteristics of the biobutanol blended fuels, we carried out experimental investigations under various pilot injection timings from BTDC 20° to BTDC 60° with constant main injection timing. As the butanol content in the blended fuel increased, the experimental results indicated that the ignition delay was longer than that of diesel fuel for all pilot injection timings. Also, the indicated specific fuel consumption (ISFC) of the blended fuels was higher than that of diesel at all test conditions. However, the exhaust temperature was lower than that of diesel at all injection timings. Nitrogen oxide (NOx), carbon monoxide (CO) and soot from Bu20 were lower than those from diesel fuel at all test conditions and hydrocarbons (HC) were higher than that from diesel.

The purpose of this work was to investigate the effect of the combustion and emission characteristics of dimethyl ether (DME), diesel fuel, and a DME-biodiesel blend on a passenger vehicle ...

Biodiesel has emerged as a suitable alternative to mineral diesel in compression ignition (CI) engines in order to ensure global energy security and to reduce engine out emissions in near future. Biodiesel derived from various feedstocks available worldwide fits well in the current fuel supply arrangement for transport sector. However, biodiesel as an alternative transportation fuel has been extensively investigated because of differences in its important fuel properties compared with baseline mineral diesel. Since fuel properties greatly influence spray development, combustion, and emission formation in internal combustion (IC) engines, a number of experimental and computational studies on biodiesel usage in CI engines have been performed to determine its brake thermal efficiency (BTE), gaseous emissions, durability, etc., by various researchers using variety of engines and feedstocks. In the present paper, a critical review of the effect of biodiesel's fuel properties on engine performance, emissions, and combustion characteristics in existing diesel engines vis-a-vis conventional diesel has been undertaken. In addition, the progress and advances of numerical modeling involving biodiesel are also reviewed to determine the effect of fuel properties on spray evolution and development of reaction mechanisms for biodiesel combustion simulations. Fuel properties are discussed in two categories: physical and chemical properties, which are key parameters affecting spray and combustion processes. Subsequent sections review spray, combustion, emissions, and performance characteristics of biodiesels under various engine operation conditions. In the last section of this review paper, numerical modeling of biodiesel covering recent numerical models and schemes to understand the behavior of biodiesel combustion and pollutants formation is included. This review paper comprehensively summarizes biodiesel fuel's (BDFs) spray, combustion, and emission characteristics using experimental and numerical approaches. Limitations and scope for future studies are discussed in each section.

The purpose of this paper is to investigate the impact of DME-biodiesel, diesel-biodiesel and diesel fuels on the combustion and emission reduction characteristics of a compression ignition engine according to pilot injection and single injection strategies. In this investigation, the effect of pilot injection and single injection modes were studied as they pertain to the combustion and emission characteristics of three alternative fuels. These tests were conducted to display the effect of a DME-biodiesel blend (DME80B20), biodiesel-diesel blend (B80D20), and diesel fuel on a passenger car diesel engine. According to the combustion characteristics, the DME80B20 fuel has a higher pressure than the B80D20 and conventional diesel fuel, while the DME-biodiesel blend exhibits a lower peak in pilot injection. The maximum pressure of the pilot injection mode showed significantly lower pressure than for single injection mode without pilot injection. In a pilot injection cycle, NO x emissions of DME-blend (DME80B20) are higher than those of diesel and biodiesel-diesel blend (B20D80), regardless of injection timings. The soot emission was nearly zero for both single and pilot injection, though diesel and B20D80 fuel showed a higher distribution of soot emission than that of DME80B20 in the case of pilot injection.

This paper investigates the effect of a dimethyl ether–soybean oil methyl ester blend as an alternative fuel on the combustion and the spatial distributions of nitrogen oxide emissions and soot emissions in a diesel engine using experimental and numerical approaches. The results obtained from the combustion and the emission characteristics (such as the heat release, the nitrogen oxide emissions, the soot emissions, the carbon monoxide emissions and the hydrocarbon emissions) of a dimethyl ether–soybean oil methyl ester blend are compared with the results from a conventional diesel fuel. The test fuels used in this investigation were dimethyl ether–soybean oil methyl ester blend, dimethyl ether and a conventional diesel fuel. The dimethyl ether–soybean oil methyl ester blend is a mixture of 80 wt % dimethyl ether and 20 wt % biodiesel fuel. A numerical calculation was conducted to analyse the combustion characteristics, the spray behaviours, the mixture formation, the emissions characteristics and the spatial distributios of nitrogen oxides and soot for the dimethyl ether–soybean oil methyl ester blend in a cylinder by using the AVL FIRE program. The numerical results showed that the combustion characteristics of the dimethyl ether–soybean oil methyl ester blend and diesel fuel were in good agreement with the experimental results, such as the combustion pressure and the rate of heat release. It was found that the effect of the dimethyl ether–soybean oil methyl ester blend on the combustion characteristics in an engine resulted in a shorter ignition delay and advanced ignition compared with those using conventional diesel fuel. In addition, the combustion duration of the dimethyl ether–soybean oil methyl ester blend was shorter than that of diesel fuel. The combustion effect of the dimethyl ether–soybean oil methyl ester blend on the concentration of the exhaust emissions indicated that the carbon monoxide emissions and the hydrocarbon emissions were lower than those from diesel fuel. On the other hand, the nitrogen oxide emissions of the dimethyl ether–soybean oil methyl ester blend slightly increased in comparison with those from diesel fuel. The soot emission concentration was nearly zero for the entire test range.

The background oriented Schlieren (BOS) method for the visualization of impinged evaporating spray is presented to analyze macroscopic spray characteristics and evolution processes. The spray characteristics of dimethyl ether (DME), DME blends, biodiesel and diesel on the impinged wall in a pressurized chamber are effectively visualized for the spray evolution processes, spray depth, and spray area at various elapsed times. The visualization results of impinged spray on the wall by BOS method compared those with the scattering method. It is confirmed that the BOS method is an effective method for measurement and visualization of impinged evaporating sprays. The spray depth for the impinged wall increased with the increase of DME mixing fraction and the evolution patterns showed the stepped increasing due to impinged effect of plane wall.

In this investigation, effect of 10%, 20% and 50% Karanja biodiesel blends on injection rate, atomization, engine performance, emissions and combustion characteristics of common rail direct injection (CRDI) type fuel injection system were evaluated in a single cylinder research engine at 300, 500, 750 and 1000 bar fuel injection pressures at different start of injection timings and constant engine speed of 1500 rpm. The duration of fuel injection slightly decreased with increasing blend ratio of biodiesel (Karanja Oil Methyl Ester: KOME) and significantly decreased with increasing fuel injection pressure. The injection rate profile and Sauter mean diameter (D32) of the fuel droplets are influenced by the injection pressure. Increasing fuel injection pressure generally improves the thermal efficiency of the test fuels. Sauter mean diameter (D32) and arithmetic mean diameter (D10) decreased with decreasing Karanja biodiesel content in the blend and significantly increased for higher blends due to relatively higher fuel density and viscosity. Maximum thermal efficiency was observed at the same injection timing for biodiesel blends and mineral diesel. Lower Karanja biodiesel blends (up to 20%) showed lower brake specific hydrocarbon (BSHC) and carbon monoxide (BSCO) emissions in comparison to mineral diesel. For lower Karanja biodiesel blends, combustion duration was shorter than mineral diesel however at higher fuel injection pressures, combustion duration of 50% blend was longer than mineral diesel. Up to 10% Karanja biodiesel blends in a CRDI engines improves brake thermal efficiency and reduces emissions, without any requirement of hardware changes or ECU recalibration.

This paper investigates the macroscopic and microscopic characteristics of DME(dimethyl ether)/isobutene blended fuel using a spray visualization and droplet particle analyzing system. In this study, the spray characteristics of DME/isobutene blends were investigated with regard to spray injection rate, spray tip penetration, spray cone angle, and the development of spray images at various blending ratios of isobutene fuel. In addition, the size distribution of DME/isobutene blended fuels and the velocity distribution of blended fuels were conducted and compared to those of conventional diesel fuel. The results showed that DME fuel has a higher injection rate peak than those of the DME/isobutene blends. The spray tip penetration increased with an increase in the injection pressure; however, the increasing rate of the spray penetration decreased with an increase in injection pressure. The spray cone angle at a 60 MPa injection pressure was larger than that at 30 MPa of injection pressure. The effect of ambient pressure on the spray cone angle according to the variation in ambient pressure showed that the spray cone angle is wider at the beginning of the fuel injection, and it converges to a similar and constant distribution. The droplet size of DME fuel showed the smallest Sauter mean diameter among the DME/isobutene blending fuels due to the excellent evaporation characteristics compared to those of blended fuels. The droplet size distributions of the test fuels were divided into two patterns: DME and the other three DME/isobutene blended fuels.

This paper investigates the effect of isobutane blended dimethyl ether (DME) fuels on the spray behaviors, combustion, and emission reduction characteristics in a diesel engine. To investig...

The purpose of this study is to examine the effects of bioethanol and gasoline as a premixed injection source on the combustion performance and exhaust emissions characteristics of a dual-fuel combustion engine. The ignition source of dual-fuel combustion was biodiesel derived from soybean oil. The premixing ratio was calculated based on the total input energy and was varied from 0.2 through 0.8. Experiments were conducted using a single cylinder diesel engine with a re-entrant geometry type combustion chamber. Experimental results show that dual-fuel combustion has a higher maximum combustion pressure ( P max ), shorter ignition delay, significantly lower NO x and soot emission, but it has higher HC and CO emission when compared to single-fuel combustion. In a comparison of bioethanol and gasoline during dual-fuel combustion, biodiesel–bioethanol dual-fuel combustion showed lower P max , longer ignition delay, and higher IMEP than biodiesel–gasoline dual-fuel combustion. The increase in the premixing ratio for both dual-fuel combustion modes increased the ignition delay and IMEP, and decreased P max . With the increase in the premixing ratio, fuel consumption increased during biodiesel–gasoline dual-fuel combustion, but decreased during biodiesel–bioethanol dual-fuel combustion. NO x significantly decreased during biodiesel–bioethanol dual-fuel combustion; however, biodiesel–gasoline dual-fuel combustion had a limited effect on NO x reduction. HC and CO emissions were increased by bioethanol or gasoline premixing. The biodiesel–bioethanol dual-fuel combustion mode showed higher HC emission than the biodiesel–gasoline dual-fuel combustion mode, and the CO emission level was similar in both combustion modes.

In this paper, effect of varying fuel injection pressures and injection timings on particulate size number distribution and spray characteristics was investigated in a single cylinder, common rail direct injection (CRDI) compression ignition (CI) engine fueled with Karanja biodiesel blends vis-a-vis baseline mineral diesel. The investigation results of spray tip penetration and spray area of biodiesel blends and diesel showed that higher fuel injection pressure result in a longer spray tip penetration and larger spray area than that at lower injection pressures at same elapsed time after the start of injection (SOI). In order to compare the effect of fuel injection parameters, 10, 20 and 50% Karanja biodiesel blends at 1500 rpm engine speed were compared with baseline data from mineral diesel. It was observed that average particulate size increased with retarding the SOI timings. Particulate number concentration was lowest for 10% biodiesel blend, which increased with further increase in biodiesel content in the blended test fuel. Addition of even very small quantity of biodiesel in the test fuel helped in reducing particulate emissions.

From the perspectives of environmental conservation and energy security, dimethyl-ether (DME) is an attractive alternative to conventional diesel fuel for compression ignition (CI) engines. This review article deals with the application characteristics of DME in CI engines, including its fuel properties, spray and atomization characteristics, combustion performance, and exhaust emission characteristics. We also discuss the various technological problems associated with its application in actual engine systems and describe the field test results of developed DME-fueled vehicles. Combustion of DME fuel is associated with low NO x , HC, and CO emissions. In addition, PM emission of DME combustion is very low due to its molecular structure. Moreover, DME has superior atomization and vaporization characteristics than conventional diesel. A high exhaust gas recirculation (EGR) rate can be used in a DME engine to reduce NO x emission without any increase in soot emission, because DME combustion is essentially soot-free. To decrease NO x emission, engine after-treatment devices, such as lean NO x traps (LNTs), urea-selective catalytic reduction, and the combination of EGR and catalyst have been applied. To use DME fuel in automotive vehicles, injector design, fuel feed pump, and the high-pressure injection pump have to be modified, combustion system components, including sealing materials, have to be rigorously designed. To use DME fuel in the diesel vehicles, more research is required to enhance its calorific value and engine durability due to the low lubricity of DME, and methods to reduce NO x emission are also required.

This study describes the effects of the fuel injection angle and the multiple-injection strategies on the combustion, the emissions and the performance characteristics in a common-rail diesel engine. To conduct this investigation, a single-cylinder diesel engine with four valves was used, and various injection strategies with different parameters such as the spray angle, the timing and a single injection or multiple injections were applied. The combustion pressure, the heat release rate and the emissions were measured by a combustion and exhaust emissions analyser system. An injection spray angle of 156° resulted in higher nitrogen oxide emissions than an injection spray angle of 60° did, as the time between the first injection and the second injection increased. Also multiple injections resulted in lower levels of soot and hydrocarbon emissions than a single injection did. A multiple-injection strategy with a dwell time of 20–40° crank angle before top dead centre and the first injection at 60° crank angle before top dead centre or 50° crank angle before top dead centre improved the engine power and lowered the fuel consumption compared with the results for a single injection.

The hydrodynamic effects on spectroscopic water detection were microscopically investigated in a gasoline pipe flow. The effects of the gasoline flow rate and the water content on the water droplet characteristics were investigated experimentally using a phase Doppler particle measurement system. The characteristics of spectral absorbance of water and gasoline were measured using a spectrophotometer to determine the optimal wavelength of the incident light for spectroscopic water detection. The effects of the droplet size on the light transmittance characteristics were calculated using the light extinction theory of Mie scattering on polydisperse particles and experimental results on the water droplet size in the gasoline flow. The measurement results of spectral absorbance showed that gasoline was almost transparent at 980 nm wavelength of light while water showed peak absorption at this wavelength, therefore, it was appropriate incident light for spectroscopic water detection. It was found that the flow conditions of the gasoline flow rate and the water content influenced the Sauter mean diameter and the volume concentration of water droplets, which influenced the light transmittance.

The light intensity measurement and image visualization of multi-hole injection spray due to different hole arrangements and hole numbers were investigated. The light intensities and behavior characteristics of the GDI spray were analyzed through the axial and diagonal spray penetration, cone angle, and spray area from the spray images by using the image visualization system and image analysis system. The atomization performance of GDI injectors was analyzed by the local and overall Sauter mean diameter (SMD) measurement. It is revealed that the higher injection pressure shows higher light intensity levels due to the strong vortices and collision by a high injection pressure. The light intensity level at the outer and end region of the spray shows lower value compared to that at the center spray region. In all of test injectors, the increased injection pressure leads to the decrease of the droplet size distribution in the initial spray. But, there is little difference of the droplet size at low and high injection pressure in middle and latter period after the injection. The overall SMD of GDI injectors showed from 14 to 23.14 μm.

The purpose of this investigation is to study the effect of biogas mixing on the combustion and emission characteristics of DME fueled diesel engine. Combustion performance was assessed in terms of combustion pressure, rate of heat release (ROHR), ignition delay, and an indicated mean effective pressure (IMEP). NO x , soot, HC and CO emissions were also analyzed using an emission analyzer. Increase in biogas mixing ratio caused a decrease in peak combustion pressure, ignition retardation and reduction in rate of combustion pressure increase. Increase in biogas also induced a decrease in the peak value and gradient of ROHR. Injection and ignition timings showed a linear correlation regardless of biogas mixing ratio when DME was injected toward the piston bowl. At the same injection timing, the increase of biogas caused a decrease in IMEP when DME was injected into the piston bowl. When DME was injected toward the crevice and squish region, IMEP increased as the biogas mixing ratio increased, and IMEP showed a linear correlation with SOI. ISNO x emissions decreased with the increase in biogas. The soot emissions level was close to zero in all test conditions. However, ISHC and ISCO emissions showed an increasing trend with increasing biogas mixing ratio.

This study was performed to investigate the effect of biodiesel derived from waste cooking oil on the spray behavior and macroscopic spray characteristics. To analyze quantitative characteristics of test fuels, injection quantity was measured at various injection pressures and the spray images of injected fuels in the pressurized chamber were obtained by using a high speed camera and image analysis system. Based on the measured spray images, the spray tip penetration and spray cone angle were investigated at various energizing timings and injection pressures. In this work, the experimental results showed that the injection quantity of waste cooking biodiesel indicated the higher quantities than diesel at high injection pressure. As the injection pressure was increased, the spray tip penetrations of biodiesel were higher value than diesel. The difference of penetration between biodiesel and conventional diesel fuel was reduced in accordance with the increase of injection pressure. Also, the spray angles of diesel were larger than that of biodiesel because diesel fuel has lower viscosity than biodiesel. In addition, the spray evolution processes of biodiesel fuel at various injection pressures and the elapsed time after the injection were compared to the conventional diesel fuel.

This study investigates the impact of dimethyl ether (DME) on the combustion and exhaust emission characteristics at low engine load operating and pilot injection conditions in a four-cylinder diesel engine that was modified for DME application. The combustion characteristics were analyzed based on the combustion pressure, the rate of heat release, the accumulated heat release, and the premixed combustion characteristics. The emission characteristics were analyzed through the analysis of the nitrogen oxides (NOx), soot, hydrocarbon (HC), and carbon monoxide (CO). The heat release amount per unit crank angle in DME combustion is higher than that in diesel combustion in a pilot injected combustion mode. The accumulated heat release of DME during the main combustion is higher than that of diesel fuel. The pilot injection combustion of DME fuel started earlier than single-injection combustion does. The advanced pilot injection timing caused a decrease of premixed combustion duration and a retardation ...

The purpose of this work was to investigate the combustion performance and the pollutant emission characteristics of gas-to-liquid fuel in a passenger car’s diesel engine. In order to perform this study, the test facilities were set up on a 1.6 l four-cylinder compression ignition diesel engine with a common-rail injection system. Gas-to-liquid fuel combustion under a high-engine-load condition was compared with conventional diesel and biodiesel derived from soybean oil. The performance test results revealed that the gas-to-liquid fuel shows more rapid ignition than diesel and biodiesel do because of its high cetane number. The rates of increase in the combustion pressure in gas-to-liquid fuel and biodiesel were smaller than that in diesel, and the maximum rate of heat release from gas-to-liquid fuel was the lowest among the three test fuels. In terms of emission analysis, gas-to-liquid fuel shows a slight decrease in the nitrogen oxide emissions and significant reductions in the hydrocarbon and the carbon monoxide emissions compared with other test fuels. Meanwhile, the combustion of gas-to-liquid fuel indicates a lower concentration of soot emissions than those from conventional diesel but slightly higher than those from biodiesel owing to the variation in the low heating value parameter.

The purpose of this paper is to compare image measurement of the evaporating spray of oxygenated fuels such as DME and biodiesel spray by using the background oriented Schlieren (BOS) technique and scattering method. In this work, the macroscopic characteristics of oxygenated fuel sprays by using BOS technique were compared with the results of scattering method. In order to analyze the vapor phase images of fuel spray in the constant-volume chamber, the BOS technique is employed to visualize the evaporating fuel spray in a constant-volume chamber with high-pressure injection system. The fuel spray characteristics with evaporating phenomena were visualized to compare the spray macroscopic behaviors such as penetration length and the area of spray axial plane. The results showed that BOS technique is an effective method for the visualization and measurement of macroscopic characteristics of evaporating fuel spray compared to the results of scattering method.

The main purpose of this study was to investigate how a narrow angle injector affects the combustion and exhaust emissions characteristics in a single-cylinder diesel engine fueled by diesel–bioethanol blends. This study focused on reducing HC and CO emissions in the exhaust emissions by the bioethanol blending of diesel. A narrow angle injector with an injection angle of 70° was used and compared with a conventional angle injector having a 156° injection angle. The bioethanol was blended with the conventional diesel up to 30% with 5% biodiesel. Experiments revealed that, in a narrow angle injector, the premixed combustion duration increased with bioethanol contents unlike the similar value of conventional injector. The premixed combustion phasing decreased with the increase of bioethanol in both injectors. The variation in the peak combustion pressure of the narrow angle injector was smaller than that of a conventional injector. In addition, the narrow angle injector induced a higher indicated mean effective pressure (IMEP) and a shorter ignition delay compared to the conventional injector. In terms of exhaust emissions characteristics, the low and stable ISHC and ISCO emissions can be achieved through the application of narrow angle injector to the diesel–bioethanol blends combustion. By the early injection combustion strategy, ISHC and ISCO emissions are significantly reduced.

The objective of this study was to determine the effects of dimethyl ether (DME) on the performance characteristics of a direct methanol fuel cell. Impedance and crossover experiments were performed in order to investigate the performance losses such as ohmic loss, activation loss and crossover loss accurately. The DME was pressurized to 5 bar to supply with liquid phase was and blended with an aqueous methanol solution. In this experiment, the membrane electrode assembly (MEA) was composed of Nafion 115, anode catalyst loaded Pt–Ru and cathode catalyst loaded Pt-Black. Experimental results showed that fuel cells with DME-methanol enhanced performance when compared to fuel cells with methanol only. Such performance enhancement was due to a decrease in activation losses by DME oxidation reactions. As the DME crossover through the membrane was reduced, the open circuit voltage (OCV) of the fuel cell increased. Other output characteristics are also discussed.

The objective of this research was to experimentally investigate the effects of the prestressing reinforcement ratio, the magnitude of the prestressing force, the loading type, and the sectional shape on the flexural behavior of beams internally prestressed with unbonded carbon-fiber-reinforced polymer (CFRP) tendons. Four rectangular and three T-beams were tested. Test results have shown that, even for the unbonded prestressing ratio less than the balanced ratio of the bonded equivalent, unbonding the CFRP tendons could relieve tendon strains along the beam span and delay the rupture of CFRP tendons. Improved ductility was observed for the rectangular beams prestressed with unbonded CFRP tendons and non-prestressed auxiliary bonded steel bars when compared with prestressed beams that have bonded CFRP tendons.

NASA Glenn Research Center (GRC) has been involved in a wide range of combustion research topics in combustor concept research, component technology development, and enabling technology development to provide enabling technologies for flight regimes from subsonic to hypersonic. These research efforts were carried out by NASA and industrial and academic partners through a range of NASA fundamental research and focused programs. These synergistic efforts in fuel injection, flame stabilization, combustion physics, and ignition studies have resulted in combustor concept changes that resulted in much cleaner-burning modern jet engines. New computational tools, optical diagnostics, fuels, and fuel conditioning technology are being currently used to develop a better understanding of the complex processes occurring in combustion systems for a range of future propulsion systems.

This article is a condensed overview of a dimethyl ether (DME) fuel application for a compression ignition diesel engine. In this review article, the spray, atomization, combustion and exhaust emissions characteristics from a DME-fueled engine are described, as well as the fundamental fuel properties including the vapor pressure, kinematic viscosity, cetane number, and the bulk modulus. DME fuel exists as gas phase at atmospheric state and it must be pressurized to supply the liquid DME to fuel injection system. In addition, DME-fueled engine needs the modification of fuel supply and injection system because the low viscosity of DME caused the leakage. Different fuel properties such as low density, viscosity and higher vapor pressure compared to diesel fuel induced the shorter spray tip penetration, wider cone angle, and smaller droplet size than diesel fuel. The ignition of DME fuel in combustion chamber starts in advance compared to diesel or biodiesel fueled compression ignition engine due to higher cetane number than diesel and biodiesel fuels. In addition, DME combustion is soot-free since it has no carbon–carbon bonds, and has lower HC and CO emissions than that of diesel combustion. The NOx emission from DME-fueled combustion can be reduced by the application of EGR (exhaust gas recirculation). This article also describes various technologies to reduce NOx emission from DME-fueled engines, such as the multiple injection strategy and premixed combustion. Finally, the development trends of DME-fueled vehicle are described with various experimental results and discussion for fuel properties, spray atomization characteristics, combustion performance, and exhaust emissions characteristics of DME fuel.

The purpose of this study was to investigate the fuel properties, droplet atomization, combustion performance, and exhaust emission characteristics of gasoline–diesel direct blended fuels in a four-cylinder diesel engine. The gasoline fuel was blended as a volumetric fraction of conventional diesel fuel. The droplet size of test fuels was measured using a phase Doppler particle analyzer (PDPA), and the combustion and emission characteristics were investigated for a four-cylinder diesel engine with a common-rail injection system and emission analyzer. In this study we found that increasing the gasoline volume fraction decreased the fuel density, kinematic viscosity, and surface tension. The temperature for 10% distillation (T10) decreased as the gasoline fraction increased. The blending of gasoline caused a decrease in droplet size by increasing the small droplets and decreasing the large droplets because the surface tension decreased with the addition gasoline fuel, thereby inducing an increase in droplet instability. On the other hand, gasoline blending resulted in an extension of the ignition delay and the formation of a more homogeneous mixture. These combustion characteristics caused the simultaneous reduction of ISNOx and ISsoot. However, the ISHC and ISCO emissions were slightly increased. The difference in ISHC and ISCO emissions between pure diesel and gasoline blended diesel fuels decreased as the engine load increased. An increase in engine load diminished the effects of gasoline blending on combustion performance and exhaust emissions.

The purpose of this article is to provide the physicochemical properties and characteristics of exhaust emissions from a DME-fueled diesel engine. Fundamental properties of DME are described and compared with the properties of the conventional diesel fuel. In addition, the applicability of DME fuel is presented in terms of its potentials as an alternative fuel for compression ignition engines. The exhaust emission characteristics of a DME-fueled engine are described using experimental results of different DME and diesel blends. The most important properties of DME are the presence of oxygen in the fuel molecule, lower ignition temperature, and high cetane number. The kinematic viscosity of DME is significantly lower than that of diesel. However, low lower hating value (LHV), low viscosity, and low lubricity are some of the major disadvantages of DME. The bulk modulus of DME is about 1/3 compared to diesel fuel. Spray tip penetration of DME is found to be shorter than that of diesel. Also, the Sauter mean diameter (SMD) distribution of the DME spray is found to be much smaller than that of diesel. Emission characteristics of different DME and diesel blends are investigated, which shows low soot, CO, and other hydrocarbon emissions.

The purpose of this study is to investigate the effect of the bioethanol port injection ratio and the in-cylinder diesel injection timing on combustion and exhaust emissions characteristics using a dual-fuel combustion strategy. Dual-fuel combustion was applied to a single-cylinder diesel engine with a displacement volume of 373.3 cm3. In a diesel–bioethanol dual-fuel combustion system, there is no need for additives to solve any phase separation between diesel and bioethanol. The combustion and emissions characteristics were investigated through the study of the indicated mean effective pressure (IMEP), ignition delay, heat release rate, indicated specific nitrogen oxides (ISNOx), indicated specific soot (ISsoot), indicated hydrocarbon (ISHC), and indicated carbon monoxide (ISCO). It revealed that IMEP increased with increases to the bioethanol port injection ratio, and the effect of bioethanol on IMEP can be clearly observed in early injection timing. The rate of combustion pressure rise decrea...

A high-resolution seismic survey, piston coring, and water column measurements were conducted on the continental shelf off southeastern Korea to examine the gas-charged sediments and gas seepage in the water column. We examined the factors controlling the spatial distribution of the acoustic blanking zone in recent Korea Strait shelf mud (KSSM) deposits along the southeastern shelf. The molecular composition, methane, hydrogen, and carbon dioxide isotope values of headspace gases, and the geochemical composition of core sediments, were measured in 11 piston cores. Dissolved methane concentrations in the water column were observed at 6 of the 11 coring sites. Acoustic blanking of the recent KSSM deposits was limited to areas with water depths between 30 and 105 m along the continental shelf, except line L-13 (133 m depth). The flanks of the acoustic blanking zone can be classified as distinct, disturbed, and step types based on their configurations. The highest methane concentration in the headspace gases was about 2.7%, 2–4 m below the seafloor, which matched the top of the acoustic blanking zone. No obvious methane was found in piston cores obtained from the gas-free zone. The δ 13 C CH4 ranged from − 56.5 to − 106.3‰ relative to Vienna Pee Dee Belemnite (V-PDB), and the δD CH4 ranged from − 194 to − 207‰ relative to Vienna Standard Mean Ocean Water (V-SMOW). These isotope values show that methane is produced by the microbial reduction of CO 2 . CH 4 oxidation results in a significantly heavier carbon isotope fraction (from – 91.2 to – 56.5‰ in the 2 m below the seafloor) with constant δ 13 C CO2 isotope fractionation. No obvious differences were seen in the total carbon (TC; 2.438–3.378%), total nitrogen (TN; 0.159–0.548%), total organic carbon (TOC; 1.139–2.078%), or CaCO 3 (2.825–15.258%) in the continental shelf, whereas the TOC was high and the CaCO 3 low distant from the Nakdong River. Distinct dissolved methane anomalies (21.87 ppm) were seen in the water column in the acoustic blanking and gas seepage zones. This level was about 15 times higher than the dissolved methane level (1.5 ppm) in the water column in the gas-free zone. These results indicate that the acoustic blanking zone accumulates biogenic methane. Methane seepage was observed in the water column throughout the acoustic blanking zone of the continental shelf off southeastern Korea.

In engine combustion studies of bioethanol blended diesel fuels, biodiesel is a very important blending fuel for preventing phase separation between diesel and bioethanol. The purpose of this study is to investigate the impact of biodiesel in bioethanol blended diesel fuel on ignition delay, premixed combustion phasing, engine performance and exhaust emissions characteristics. In this work, the fuel properties of diesel–bioethanol blends were measured and engine tests were conducted using a single cylinder diesel engine. Based on the experimental results, we found that increasing the biodiesel blending ratio recovered the reduced fuel density and cetane number of bioethanol blended diesel fuel, while the kinematic viscosity and surface tension both increased. In addition, the lower heating value (LHV) slightly decreased when biodiesel fuel was added. By increasing the blending ratio of biodiesel fuel, the ignition delay and the premixed combustion phasing advanced, and the IMEP decreased. However, the premixed combustion duration in all tested blended fuels showed almost similar values, regardless of the biodiesel contents. Biodiesel blending decreased the EI-HC emission in wide engine operating regions. In addition, for the premixed combustion phasing and ignition delay, the increase of biodiesel fuel influenced the decrease of EI-HC emission. In the case of EI-CO and EI-soot emissions at advanced injection timings (around 30° BTDC), when the combustion occurred in the squish area of the combustion chamber, the biodiesel blending impact was clear. The increase of biodiesel fuel reduced EI-CO and EI-soot emissions. In addition, the increase of biodiesel fuel slightly reduced the EI-NOx emission.

The study is to investigate the mixing stability, fuel properties, and macroscopic spray characteristics of diesel-gasoline blended fuels in a common-rail injection system of a diesel engine. The test fuels were mixed diesel with gasoline fuel, which were based volume fraction of gasoline from 0 to 100% in 20% intervals. In order to analyze the blended effect of gasoline to diesel fuel, the properties of test fuels such as density, viscosity, and surface tension were measured. In addition, the spray behavior characteristics were studied by investigating the spray tip penetration and spray angle using a spray images through a spray visualization system. It was revealed that the density, kinematic viscosity and surface tension of diesel-gasoline blending fuels were decreased with the increase of gasoline fuel. The injection quantity of test fuels were almost similar level at short energizing duration condition. On the other hand, the increase of energizing duration shows the decrease of injection quantity compared to short energizing duration. The test blending fuels have similar growth in Spray tip penetration and Spray cone angle.