Combustion Characteristics Of Diesel Research Articles

Combustion characteristics of RP-3 aviation kerosene/n-butanol blended fuel in a compression ignition engine

In order to meet the requirements of Sustainable Aviation Fuel (SAF) to achieve the imperatives of energy conservation and emission reduction. This paper compares the combustion characteristics of diesel, RP-3/n-butanol blends in terms of heat release rate, in-cylinder pressure, temperature and fuel economy in a compression ignition engine, taking into account the advantages of lightweight structure, low fuel consumption and wide range of applications of aviation piston engines. The results certified the viability of applying RP-3 and RP-3/n-butanol blends in diesel engines. Adding n-butanol prolonged the ignition delay and shorten the combustion duration. Moreover, the peak of the pressure, temperature and apparent heat release rate (AHRR) increased. In addition, the blended fuel showed obvious diffusion combustion characteristics at high load. With the n-butanol increased, the combustion instability of the blended fuels decreased significantly, at low load. At n = 2400r/min, pme = 0.53 MPa, compared with diesel, the maximum heat release rate (MHRR) of R70B30 increased by 76.6 %, improving the combustion characteristics of the blended fuel. Moreover, the equivalent specific fuel consumption (ESFC) of RP-3 is 5.56–14.83 % lower than that of diesel, and the effective thermal efficiency (ETE) of RP-3 is 2.8–13.46 % higher than that of diesel under most working conditions.

Visualization study the cross spray and combustion characteristics of diesel and methanol in a constant volume combustion chamber at cold and flare flash boiling regions

To optimize the performance of diesel/methanol dual fuel engine, fundamental research on the spray and combustion characteristics of diesel/methanol dual direct injection was conducted in a constant volume combustion chamber. The injection pressures were set as at 60 MPa, 80 MPa, 100 MPa, while the ambient pressures were set as 4 MPa and 0.01 MPa, corresponding to cold and flare flash boiling regions, respectively. The results showed that diesel/methanol cross-collision accelerated the droplet interaction, promoting more uniform mixing. Compared to the cold region, the diesel/methanol collision spray had a larger axial and radial diffusion rate and evaporation rate in the flare flash boiling region. In addition, in the flare flash boiling region, the collision length, collision width, and spray projected area of both the liquid and gas phases were significantly greater than those in the cold region. With the increase in injection pressure, the spray obtained more kinetic energy, leading to a more intense collision process and more homogeneous fuel-gas mixing. Besides, a higher injection pressure shortened the mixing time of the fuel-air mixture before collision, resulting in a smaller equivalent ratio, a smaller ignition delay, a larger flame lift-off length, and a lower soot formation.

On ammonia/diesel dual-fuel combustion in optical engine

Ammonia-diesel dual-fuel combustion mode is one of the potential ways to achieve lower carbon emissions in compression ignition engines. In this work, the effects of ammonia addition on diesel combustion characteristics were experimentally investigated in an optical CI engine. The gaseous ammonia is introduced to the engine through a port injection while diesel is directly injection into the cylinder. A color high-speed camera was utilized to detect and differentiate between diffusion burning and lean-premixed ammonia combustion. Additionally, computational models were conducted and the findings were coupled with the experimental data. According to optical investigations, the lift-off distance is created during the diesel spray and progressively grows as the ammonia energy ratio (AER) rises. The findings indicate that, in comparison to pure diesel combustion mode, combustion in an ammonia environment exhibits prolonged ignition delay duration and lesser flame luminosity. Secondly, a multi-injection strategy for diesel fuel was used where the diesel pre-injection timing (SOPI) values adjusted from −30 °CA ATDC to −60 °CA ATDC). Advancing SOPI is an effective approach to suppress diesel diffusion flame and reduce soot production in the cylinder. For advanced SOPI, findings reveal that rich pockets have decreased drastically as the combustion progresses. With the advancement of SOPI, there is a notable a connection between the flame speed and the peak heat release rate, where a high flame speed correlates to a greater heat release rate peak. Finally, the ratio of pre-injection of diesel fuel (ROPI) varied from 0 to 100% as a mean to improve flame propagation. There is a crucial threshold of pre-injection (ROPI) mass ratio of 45%, at which the initial flame features alter considerably. As the ROPI exceeds 45%, the flame kernel appears as a visible flame near to the main injection timing (SOMI), indicating that the ignition delay duration is decreasing.

An experimental study the cross spray and combustion characteristics diesel and ammonia in a constant volume combustion chamber

Recently, the use of ammonia, a carbon-free fuel, in internal combustion engines, particularly in dual fuel dual direct injection engines, has attracted wide attention. However, the spray and combustion characteristics of diesel and ammonia dual direct injection especially on cross injections remain unclear. An optical study of diesel and ammonia spray and combustion was conducted using a constant-volume combustion chamber. The results revealed that spray tip penetration (STP) and spray projected area (SPA) of ammonia are lower than those of diesel, indicating that ammonia has a higher evaporation rate and a smaller diffusion rate than diesel. Besides, diesel and ammonia atomization was promoted through cross injection and collisions. As the cross injection interval increased, the liquid-phase STP of the collision spray increased, and its liquid-phase SPA decreased, while its vapor-phase SPA increased, promoting the diffusion and evaporation rates of the collision spray. In addition, increasing the interval of diesel and ammonia injection can shorten the ignition delay, and increase the flame lift-off length, leading to a more intense combustion process and less soot emissions. Therefore, the combustion and emission characteristics can be effectively improved by adjusting the injection timing of the two fuels reasonably.

Experimental Investigation into the Impact of Natural Gas-Diesel Mixture on Exhaust Emissions and Engine Performance in a Heavy-Duty Diesel Engine with Six Cylinders

In this study, experiments were conducted with a mixture of pure diesel and natural gas. In the experiments, a 6-cylinder heavy-duty diesel engine with an engine displacement of 11,670 cc was used and the engine speed was kept constant at 660 rpm. At 660 rpm engine speed, the maximum torque value reached was 386 Nm. The 386 Nm torque value was accepted as 100% and experiments were carried out at torque ratios of 25, 50, 75 and 100%. In all experiments with natural gas mixture, natural gas was delivered to the combustion chamber at a pressure of 1.5 bar and a flow rate of 1.29 g/sec, pre-mixed with air from the intake manifold. The aim of this study is to investigate the combustion characteristics of pure diesel and natural gas mixtures in a heavy-duty diesel engine. According to the test results, the BTE value of natural gas - diesel blended fuel decreased by 157, 89, 53, 53 and 28% at 25, 50, 75, 100 torque values, respectively, compared to pure diesel. It was observed that at low torque values, natural gas - diesel blended fuel was very inefficient, but as the torque value increased, there were improvements in the BTE value of natural gas - diesel blended fuel, although it could not reach the BTE value of pure diesel. In the experiments with pure diesel, it was determined that the fuel consumption was 127, 68, 38, 17% less than the natural gas - diesel blended fuel at torque values of 25, 50, 75, 100%, respectively. The most significant change in exhaust emissions was observed in CO and UHC emissions. At maximum load, CO and UHC emissions were found to be 4.42 and 4.5 g/kWh for pure diesel and 19.9 and 11.9 g/kWh for natural gas blend, respectively.

Investigation of evaporation and combustion characteristics of diesel and fatty acid methyl esters emulsified fuel droplets

To address the problems of energy shortages and environmental pollution, biodiesel and its emulsified fuel have gained wide attention. In this work, the fatty acid methyl esters (FAME) emulsified water-in-oil fuel (BW) is thoroughly investigated using the droplet suspension experiment with a focus on the main characteristics of puffing/micro-explosion, droplet ignition delay and flame regime, etc. The role of water content at different ambient temperatures is examined in comparison to a counterpart blend of diesel/water (DW) fuel. Results show that the increase in water content and temperature has a significant promotion effect on the strength and number of puffing/micro-explosion process, however, the higher viscosity of BW leads to the lower values. And owing to the heat absorption by water evaporation, only the micro-explosion with high intensity induced by water nucleation has a favorable effect on the evaporation rate. There exists a critical concentration of water addition, after which the enhancement of evaporation is expected. Moreover, it is indicated that the diesel with water additives has a better atomization effect, and the size of child droplets generated by DW droplets breakup is smaller, which is in the range of 0.08–0.1 mm compared to the 0.09–0.13 mm for BW droplets. It has been shown that the increase in water content hinders the rise of droplet flame temperature, extends the ignition delay time, and shortens the maximum premixed-flame length. Compared to diesel droplets, the larger combustion rate of BW droplets is correlated with their shorter flame length and the higher boiling point of FAME.

Experimental investigation of the effects of diesel-bioethanol blends on combustion and emission characteristics in industrial burner

The increased rate of industrialization in various countries has increased the demand for fossil fuels, which are found in limited reserves and in specific countries. As a result, countries that lack these energy resources are experiencing an energy crisis. As a result, alternative fuels that are made locally within countries are needed, like alcohol.. Experiments were carried out in this research to examine the combustion and emission characteristics of diesel and bioethanol blends using an industrial 350 KW burner. Three different diesel/bioethanol ratios (DE-10, DE-15, and DE-25) were tested. Flame geometries, temperatures, and emissions for diesel/bioethanol blends were measured experimentally for each type of fuel to obtain a complete characterization of the combustion processes. The findings showed that an increase in the percentage of bioethanol in the fuel blends for DE-10, DE-15, and DE-25 reduced CO, UH, NOx, and soot emissions (by around 20%, 40%, and 45%), (by about 13%, 25%, and 43%), (by about 8%, 14%, and 22%), and (by about 16%, 33%, and 50%), respectively, compared to neat diesel combustion. However, because bioethanol has a lower heating value than diesel, As bioethanol percentages increased in the fuel mixture, exhaust temperature and maximum flame temperature decreased.

Characterization of diesel spray combustion under micro-hole and ultra-high injection pressure conditions-analyses of diffused back-illumination imaging and OH* chemiluminescence imaging

This study investigated the spray combustion characteristics of diesel fuel using the Diffuse Back-illumination Imaging (DBI), Direct Photographic, and OH* chemiluminescence methods under different injection pressures (100–300 MPa) and different hole diameters (0.07–0.133 mm). The results indicated that at a certain point, the downstream of the spray, which holds a strong turbulent mixing, starts to disappear gradually without bright flames due to the cool flame combustion process. Based on this process, the ignition timing was determined using the space integral of intensity and optical thickness through the DBI method, which was validated by the OH* chemiluminescence method. The utilization of a micro-hole diameter injector and ultra-high injection pressure can effectively reduce ignition delay. Significant oxidation processes were observed both downstream and upstream for the micro-hole injector under ultra-high injection pressure. A parameter utilizing spatially integrated natural luminosity to OH* chemiluminescence ratio showed that increasing injection pressure and reducing hole diameter effectively reduced soot under unit fuel oxidation conditions. And predicted model results of droplet diameter and equivalence ratio (Siebers' and Hiroyasu's model) were used to analyze the experimental results. These findings contribute to the understanding of spray combustion characteristics and inform the development of efficient and low-emission combustion systems.

Optical diagnostic study of internal and external EGR combined with oxygenated fuels of n-butanol, PODE3 and DMC to optimize the combustion process of FT synthetic diesel

With the introduction of carbon neutrality target, Fischer-Tropsch (FT) synthetic fuels are coming back into the limelight as a kind of carbon–neutral fuel. However, the mismatch between the overly high cetane number (CN) and the relatively low vaporability of FT synthetic diesel is unfavorable to the soot emission control, which will make it difficult to meet more stringent fuel consumption and emission regulations in future applications. To investigate the potential of oxygenated fuels combined with different exhaust gas recirculation (EGR) introduction schemes to achieve high-efficiency and clean combustion of FT synthetic diesel, an optical diagnostic study was carried out based on high-speed photography and the two-color method. The results show that all three kinds of oxygenated fuels could suppress soot emissions via self-carrying oxygen and adjusting the physicochemical properties of the fuel blend. Compared with the combustion characteristics of FT synthetic diesel, the flame area and luminosity of oxygenated blends are reduced, and the in-cylinder temperature and soot KL factor are lowered. Among them, n-butanol exhibits a greater capability of soot control compared to polyoxymethylene dimethyl ethers (PODE3) and dimethyl carbonate (DMC). In addition, introducing internal and external EGR to the engine fueled by n-butanol/FT synthetic diesel blend shows that with the increase of EGR rate, the external EGR exhibits a gradually stronger inhibiting effect on the heat release process and soot KL factor, while the internal EGR exhibits an inhibiting and then promoting effect. Moreover, the high ratio internal EGR shortens the ignition delay (ID) significantly due to the strong heating effect, which is unfavorable to the control of soot emission. The combination of oxygenated fuels and internal/external EGR could effectively optimize the combustion process of FT synthetic diesel and inhibit soot generation, but the EGR rate needs to be controlled within a proper range.

Determination of combustion and emission characteristics of liquid Fischer-Tropsch diesel fuel synthesized from coal in a diesel engine

Fischer–Tropsch (FT) synthesis is a production method that processes a liquid diesel fuel from heavy carbon-containing organic compounds such as coal and biomass. FT synthesis is an essential process in demonstrating the usability of coal-to-liquid fuel in internal combustion engines. This study investigates the effects of using FT diesel fuel synthesized from coal on the combustion characteristics of a single-cylinder common-rail direct-injection diesel engine. The engine tests were conducted at 50% of the wide-open throttle position and fixed engine control parameters (cycle duration, fuel amount, start of injection timing, etc.). As a result of the study, it was observed that the combustion with the use of FT diesel fuel started (almost 1.5 °CA) and completed earlier according to the petroleum-based diesel (D100). The cyclic variations were more stable with FT diesel fuel. With the use of FT diesel fuel, the indicated mean effective pressure was 3% lower, peak cylinder gas pressure was slightly lower, and the combustion noise was 2–3 dB quieter compared to D100. The heat release was higher during the premixed combustion phase at the cycle durations of 67 ms and 55 ms, while it occurred very small at the cycle duration of 86 ms. Significant reductions in CO2 and NOx emissions, which are complete oxidation products, were obtained with FT diesel fuel compared to D100. The fuel properties, combustion characteristics and emission results showed that no further measures should be taken to use FT diesel in compression ignition engines. FT diesel fuel can be safely used as an alternative fuel.

Experimental study on the interactions of wall temperature and impingement distances and their effects on the impinged diesel spray ignition and combustion characteristics

This study examines the interactions of wall temperature and impingement distances and their effects on the impinged diesel spray ignition and combustion characteristics experimentally in a modified constant-volume combustion chamber. Four wall temperatures of 570 K, 620 K, 700 K, and 800 K, and four impingement distances that correspond to severe wall-wetting, slight wall-wetting, critical wall-wetting, and non-wall-wetting separately are tested. The results indicate increasing wall temperature can promote auto-ignition and the following combustion process, denoted by shorter ignition delays and higher flame area (FA) and spatially integrated natural luminosity (SINL) values, but the promotional effect generally weakens with the increase of the impingement distance. When the wall temperature is high enough, the spray/wall impingement can accelerate fuel evaporating and mixing with the entrained air, in which case decreasing the impingement distance is positive to auto-ignition and combustion. This trend is basically the opposite in low-wall temperature cases where the cooling effect plays a leading role. Besides, the normal distances from the ignition points to the wall decrease with the increment of the wall temperature, and the changes are more remarkable at lower impingement distances, which means that increasing the wall temperature may enhance auto-ignition and combustion in the near-wall region, probably leading to an enlarged temperature gradient in the boundary layer and strengthened heat transfer.

Spray and Combustion Characteristics of CTL-Diesel Fuel Blends in a Constant-Volume Combustion Chamber.

Coal-to-liquid (CTL) fuel is considered a promising alternative fuel for diesel engine applications in China owing to its excellent fuel properties. However, little research on the spray and combustion processes of CTL fuel has been scarce. Therefore, in this study, the spray and combustion characteristics of diesel fuel blends with different CTL fuel blending ratios were investigated in a constant-volume combustion chamber. The results show that under non-evaporation conditions (300 K), a longer spray tip penetration (STP) and enlarged spray cone angle (SCA) were obtained with a higher injection pressure owing to the enhanced turbulent interaction. The SCA of CTL fuel blending was larger than that of diesel fuel owing to its lower viscosity and slightly shorter STP. Under the evaporation condition (700 K), with an increase in the CTL mixing ratio, both the STP and SCA of the fuel exhibited a decreasing trend owing to the higher volatility. Meanwhile, as the CTL mixing ratio increased, the ignition delay period was shortened, and the flame lift-off length decreased, whereas both the integrated natural flame luminosity and combustion duration increased. The cetane number of CTL fuel plays an important role in the occurrence of these results.

Enhancement of combustion and emission characteristics of diesel using lavender oil blending

PurposeThis study aims at improving combustion process to reduce emissions. Emissions such as carbon monoxide, particulate matter and unburnt hydrocarbons are a result of incomplete combustion. These emissions have useful energy but cannot be reclaimed. Hence, to enhance combustion, effect of biofuel blending on diesel combustion was investigated.Design/methodology/approachEssential oils have been found easier for blending with diesel because of simple molecular structure compared to vegetable oils. Lavender oil is an essential oil which has not yet been studied by blending with diesel. The major constituents of lavender oil are linalyl acetate (cetane number improver) and linalool (nitrogen oxides reduction). A single-cylinder, four-stroke diesel engine was run by blending diesel with lavender oil (Lavandula angustifolia oil [LAO]) in varying proportions, 5%, 10% and 15% by volume.FindingsHigher heat release rate (HRR) was observed using lavender oil blends compared to pure diesel. Compared to diesel, an increase in brake-specific fuel consumption using blends was observed. LAO15 has the lowest CO emissions at all loading conditions, 29.3% less at 100% load compared to diesel. LAO5 and LAO15 have 6.9% less HC emissions at 100% load condition compared to diesel. LAO15 has only 1.3% higher NOx emissions compared to diesel at 100% load condition. LAO5 has the lowest smoke content at all loading conditions.Research limitations/implicationsLavender oil was used directly without any processing. Tested on single-cylinder engine.Originality/valueTo the best of the author’s knowledge, currently, there is no published work on lavender oil–diesel combination. Lavender oil can provide a simple renewable solution for diesel additives with potential up to 15% blending.

Effect of ABE and butanol blends with n-dodecane in different volume ratios on diesel combustion and soot characteristics in ECN spray a conditions

This study investigates the feasibility of using Acetone-Butanol-Ethanol mixture (ABE) as a function of the volumetric ratios (20 %v, 30 %v, 40 %v, 50 %v blended with n-dodecane) in order to determine the most suitable ABE ratio for CI engines in comparison to a butanol/n-dodecane blend. The “New One Shot Engine” set-up was used to determine the lift-off length (LOL), ignition delay (ID) and soot concentration by means of OH* chemiluminescence and Diffused Back Illumination imaging at an ambient pressure and temperature of 60 bar and 900 K corresponding to ECN Spray-A conditions. It was found that ID and LOL increased, while soot concentration was reduced with the increase in concentration of ABE and Butanol in dodecane blends. The blends with the smallest content (20%) of ABE or Bu exhibited similar combustion characteristics to n-dodecane with a considerable reduction in soot, indicating that these blends can be considered as a Diesel substitute without any engine modifications.

Experimental study on the effect of load and air+gas/fuel ratio on the performances, emissions and combustion characteristics of diesel–LPG fuelled single stationary ci engine

AbstractDue to the issue of combustion stability when using natural gas and the problem of knocking when using both natural gas and hydrogen, liquefied petroleum gas (LPG) is then a good candidate to use for the dual‐fuel concept since it has been proven to be a good solution to limit the pollutants and the excessive use of fossil resources in the aim to support and advance the African Union's and UN's sustainable development goals. In this paper, the effect of load as well as the air + gas/fuel ratio on the performance, emission, and combustion characteristics of a dual‐fuel diesel–LPG engine, single‐cylinder, four‐stroke, direct injection diesel engine with a rated power of 3.5 kW at a speed of 1500 rpm has been carried out. Experiments have been performed in dual‐fuel mode for a range of loads from 0 to 12 kg and a range of volume flow of LPG from 1 to 5.5 L/min, and the results were compared with those obtained from the single‐fuel mode. Results show that the dual‐fuel mode gives better performance and fewer pollutants than the single‐fuel mode. For example, at low load, Brake thermal efficiency, the indicated thermal efficiency, and mechanical efficiency increased by 83.79%, 24.36%, and 41.77%, respectively, and by 57.48%, 19.84%, and 24.37% at high load when we moved from the single‐fuel mode to the dual‐fuel mode. The smoke, carbon monoxide, and NOx decreased by 24.3%, 94.2%, and 96.2% respectively at low load and by 62.3%, 89.8%, and 91.4% at high load. And, no knocking came up during this research compared to natural gas or hydrogen dual‐fuel engines.

Comparative study of ignition characteristics and engine performance of RP-3 kerosene and diesel under compression ignition condition

This paper aims to explore the spontaneous combustion characteristics and engine performance of kerosene under traditional compression ignition mode, providing a reference for further optimizing the performance of kerosene compression ignition engines and the application of advanced combustion mode. The ignition visualization tests of kerosene under marine and vehicle engine conditions are carried out, and the characteristics under 0.3 mm nozzle diameter are compared with that of diesel. Then, the engine performance of the two fuels under medium load and ultra-high injection pressures is compared. The experimental results show that the ignition and combustion characteristics of kerosene and diesel are very similar, indicating that kerosene has a strong universality in diesel engine application. The long ignition delay time of kerosene leads to its lagging combustion and heat release. Compared with diesel, kerosene has lower CO, particulate emissions and indicated thermal efficiency, while higher HC and NOx emissions. The emission characteristics of kerosene RP-3 are different from previous studies, especially under ultra-high injection pressure. The combustion process and engine emissions of kerosene may be optimized with advanced combustion models and strategies.

Analysis of energy flows and emission characteristics of conventional diesel and isobaric combustion in an optical engine with laser diagnostics

In this study, the thermodynamic analysis of energy distribution, exhaust emissions, and particulate characterization was conducted in an optical engine with an all-metal configuration. Additionally, the line-of-sight integrated imaging of combustion luminosity, and OH* chemiluminescence along with planar laser induced fluorescence of formaldehyde (HCHO-PLIF), and planar laser induced incandescence of soot (soot-PLII) were applied in the optical configuration. The experiments were conducted with conventional diesel combustion at λ = 3 (i.e., CDC), isobaric combustion at λ = 3 (i.e., Iso3), and isobaric combustion at λ = 4.2 (i.e., Iso4.2) using n-heptane fuel. Compared to Iso3 and CDC, Iso4.2 yielded higher thermal efficiency and lower heat losses; whilst the exhaust losses were exacerbeted. Isobaric combustion also resulted in lower NOx but increased soot emissions. For all operating conditions, the combustion luminosity and OH* chemiluminescence imaging showed that the signal grows and develops from the jet-axis downstream of the nozzle to the jet-wall impingement point, followed by movement towards the squish region. HCHO-PLIF showed that isobaric combustion leads to a faster transition of low-to high-temperature reactions compared to CDC. Soot-PLII showed increased in-cylinder soot distribution for isobaric combustion due to lesser charge pre-mixing time and spray-flame interaction induced by close-coupled injections.

Effects of alumina nanoparticles on evaporation and combustion characteristics of diesel fuel droplets

BackgroundEffects of alumina nanoparticles (Al2O3 − NPs) on the evaporation and combustion characteristics of diesel fuel (C10H22) droplets in a model combustion chamber are numerically investigated. The nanofuel (n-fuel) is resulted from adding Al2O3 − NPs in volume fractions of 0.5 and 1 percent (0.5 and 1 vol%) to the base fuel (C10H22). MethodsTo model the two-phase flow, consisting of fuel droplets and inlet air, the Eulerian-Lagrangian approach is applied. The discrete ordinates (DO) radiation heat transfer model and the diffusion flamelet combustion model are employed in order to investigate the characteristics of the reactive flow. Significant findingsWith the addition of 0.5 and 1 vol% of Al2O3 − NPs, average increases of 0.48% and 0.95% in the heat capacity, as well as 20% and 46% in the latent heat of evaporation, of the base fuel occur, respectively. The maximum temperature of the chamber drops by 30 K and 60 K, consecutively. Further, the average mole fractions of oxides of nitrogen (NOx) at the outlet decrease by 17.6% and 34.3%, respectively. However, the oxides of carbon (CO and CO2) decrease too, as drops of 5.6% and 7.7% in CO2 average mole fraction at the outlet are observed. This can indicate the lower evaporation and burning rate of the n-fuels, as compared with the pure fuel.

The study of ignition and emission characteristics of hydrogen-additive hydro-processed renewable diesel

This study was conducted to understand the effects of hydrogen (H2) addition on the combustion and emission characteristics of hydro-processed renewable diesel. Experiments were performed in a constant volume combustion chamber (CVCC) at varying H2 concentrations (0%, 5%, and 10% (by vol.)) relative to air (100%, 95%, and 90% (by vol.)), initial temperatures (Tini) of 600, 650 and 700 K, equivalence ratios (φ) of 0.5, 1.0, and 1.5 and a fixed initial pressure (Pini) of 10 bar. Overall, HRD has lower ignition delay (ID) and total ID. However, H2 addition to HRD delayed the fuel's auto-ignition due to excess H2 oxidation (H2+OHH2O + H) reaction taking place, which turns the chain reactions from branching to propagation, resulting from increasing in ID. Moreover, increasing of H2 concentrations enhanced the maximum pressure rise (Pmax) and heat release rate (HRR), whereas carbon dioxide (CO2) and unburned hydrocarbon (HC) were decreased due to the higher magnitude of the lower heating value of H2 than that of pure HRD. Since H2 itself is a carbon-free molecule, the carbon content of the fuel is reduced. H2 has the characteristics of fast combustion, resulting in a more flammable and complete mixture, which also makes HC emissions to become lower. However, the higher energy density of H2 significantly raises the combustion temperature, and subsequent nitrogen oxides (NOx) were increased. The kinetic modeling predictions revealed that the IDs for HRD-H2 were elongated due to the increased hydroperoxyl (HO2) and hydrogen peroxide (H2O2) mole fractions which led to improved stability.

Experimental investigation on performance, emission and combustion characteristics of neem oil bio diesel using ethanol blend

Experimental investigation on performance, emission and combustion characteristics of neem oil bio diesel using ethanol blend