Reduction In Unburned Hydrocarbons Research Articles

Performance and emissions of a diesel engine burning blends of Jatropha and waste cooking oil biodiesel

Blending of biodiesels is a straightforward but efficient solution to the issue of improving biodiesel characteristics in cold climates. A comparison of emissions and performance of a diesel engine powered by methyl ester blends made from jatropha and waste cooking oil (WCO) was investigated. Jatropha oil was converted into biodiesel through esterification and transesterification, but WCO biodiesel was produced by transesterification. Volume percentages of WCO and jatropha biodiesels as 5, 10, 15, 20, and 100% were prepared. Peak improvements in brake thermal efficiency (BTE) were 7% and 6% for JB20 and WB10 + JB10, respectively, at 75% of engine output power over diesel fuel. Maximum reductions in brake specific fuel consumption (BSFC) related to diesel oil were for JB20 and WB10 + JB10 6 and 5%, respectively. For JB100, the maximum increase in exhaust gas temperature over diesel oil was 45%. For WB10 + JB10, the maximum reduction in carbon dioxide (CO2) emission about pure diesel was 10%. WB10 + JB10 blend had carbon monoxide (CO) emission reduction up to 6% than fossil diesel. For WB10 + JB10, the maximum reduction in nitrogen oxides (NOx) emission relative to crude diesel was 10%. WB10 + JB10 had the greatest reduction in smoke emission when compared to diesel oil as 22%. WB10 + JB10 had the largest reduction in unburned hydrocarbons (HC) of 14% over diesel oil at 75% of output power. In comparison to other fuels, the WB10 + JB10 and JB20 biodiesel blends produce better engine performance and lower emissions as compared to other biodiesel blends. As an alternative fuel in conventional diesel engines, it is recommended to use a mixture of jatropha and WCO biodiesels of 10% by volume.

High temperature fuel impacts on combustion characteristics of a swirl-stabilized combustor

Future aircraft will require advanced thermal management systems to manage the increased heat loads resulting from the avionics, turbomachinery and other subsystems of higher performance, and high speed flight systems. Fuel is the primary coolant to alleviate these thermal management challenges. Heated fuel entering the combustor is likely to affect combustion performance due to dramatic changes in properties that impact fuel atomization, distribution, vaporization and fuel/air mixing. In this study, the combustion performance, emissions, and flame characteristics of a single-nozzle, swirl-stabilized combustor operating with high temperature fuels were investigated. Four fuels representing a wide range of jet fuel physical and chemical properties were studied at injection temperatures of 32, 121 and 260 °C. The test fuels included a conventional Jet A (A-2), a low cetane number alcohol-to-jet (ATJ) alternative fuel (C-1), n-dodecane (n-C12) and a high viscosity jet fuel blend (C-3A). Tests were conducted at a combustor pressure of 2 atm and inlet air temperature of 121 °C at global equivalence ratios (ϕ) of 0.10–0.24 for most fuel temperatures. Particulate matter (PM) emissions (concentrations and size distributions), and primary gaseous emissions were measured. High frequency pressure measurements and high-speed video were collected to assess fuel temperature impacts on combustion stability and flame characteristics, respectively. Results show that the heated fuel impacts on combustion were highly dependent on fuel type, temperature and ϕ. Qualitative results show that as fuel temperature increased, the flame in the primary zone appeared more compact, and less thermally radiant (lower soot). PM emissions were significantly impacted with reductions exceeding 95 % in particle number density for all fuels, and between 20 and 55 % reductions in mean particle diameters for aromatic-containing fuels. Gaseous emissions show up to ∼ 90 % reduction in unburned hydrocarbons (UHC) and up to 60 % reduction in carbon monoxide (CO), and corresponding moderate increases in NOx and CO2 with the heated fuel. The combustor acoustic response was slightly suppressed in frequencies of interest as fuel temperature increased. In general, the impacts of heated fuel on combustion were mostly beneficial and are primarily attributed to improved fuel atomization and reduced fuel evaporation timescales of the heated fuel. Specific impacts of fuel physical and chemical properties, and potential implications of heated fuel combustion are discussed.

Alternative fuels: An overview of current trends and scope for future

Abstract The concern over rapid depletion of fossil fuels has prompted the search for alternative fuels having efficiencies similar to those found for the conventional fuels being used today. The present article reviews the prospects and opportunities for using alternative fuels in different applications. The properties of these fuels and their performance as a fuel are discussed in detail. Vegetable oils present a very promising scenario of functioning as alternatives to fossil fuels. Use of biodiesel in a conventional diesel engine results in a substantial reduction in unburned hydrocarbons, carbon monoxide, particulate matter, and nitrogen oxides. Different alternative fuels have been compared with the conventional fuels, and clearly the consumption of the latter can be significantly decreased by the use the blended fuels. Most of the alternative fuels have properties similar to those of the existing fuels, and therefore the technology required to handle them is already well known. Hydrogen is an exception to this, and its ignition properties are quite different from those of the conventional fuels. Difficulties are thus expected during the storage, transport, and use of hydrogen as a fuel. Other technologies are also discussed such as alternative routes to equivalents of conventional fuels, like CTL. Finally, the emulsified fuels including the use of oxygenates have been discussed.

Environment-friendly biodiesel production by transesterification of rapeseed oil: effect of reaction parameters

Abstract The huge energy demand in the industrialized world and the pollution problems caused due to the worldwide consumption of fossil fuels has made it necessary to develop alternative sources of energy. It is estimated that pure biodiesel provides over 90% reduction in unburned hydrocarbons and 75–90% reduction in aromatic hydrocarbons. This results in almost total reduction in sulphur dioxide (which causes acid rains), 40–60% reduction in soot particles, 80% and 10– 15% reduction in carbon dioxide and carbon monoxide emissions respectively. Reduction of poly-aromatic hydrocarbons is extremely important as many of these hydrocarbons are cancer causing and ozone-forming compounds. Biodiesel does not interfere with the carbon cycle or cause climate change (vegetables from which oils are extracted for biodiesel production remove carbon dioxide from the atmosphere to grow). Due to the global drive towards renewable, non-toxic and environmentally acceptable products the ability of the commercial lipolytic ...

Improvement of Stratified Combustion by a Large Amount of Hot EGR (Reduction of Unburned Hydrocarbons)

Unburned hydrocarbons from a direct injection stratified charge engine were greatly reduced by a large amount of hot EGR. A hydraulically controlled variable valve system was used to realize the hot EGR. Almost all the amount of required EGR gas for the NOx reduction was supplied directly from the previous cycle through the exhaust or inlet valves. Two kinds of recirculation were examined in this test. The first was the recirculation through the exhaust valves, which opened additionally during the suction stroke. Another was the recirculation through the inlet valves. The exhaust gas was pushed back to the port during the exhaust stroke through the additionally opened inlet valves and re-induced in the next cycle. Although both methods have the same ability to reduce HC emissions, required EGR was less in the latter method.

Exhaust Oxidation of Unburned Hydrocarbons from Lean-Burn Natural Gas Engines

Post cylinder oxidation of unburned hydrocarbons (UHC) was studied using a 35 kW lest engine. The engine was equipped with an insulated exhaust reactor to extend the residence time. The exhaust reactor performance has been characterised under the basic engine operating conditions, and under conditions where temperature and composition (NOx level) of the exhaust were modified independent of engine settings. The experiments studied spanned a wide range of moderately lean-bum conditions. The composition at the exhaust port was as follows: O2 5-9% (engine excess air ratios of 1.28-1.75), UHC 1000-7000 ppm, CO 550 ppm, NOx0-1400 ppm. The temperature varied from 600 to 700°C, In addition, experiments with injection of hydrogen peroxide to promote UHC oxidation in the exhaust system were conducted. The amount of UHC oxidised in the exhaust system depended closely on the exhaust temperature, residence time and concentration of nitrogen oxides in the exhaust gas. The increased reaction time in the exhaust reactor caused an oxidation of the exhaust hydrocarbons of up to 90% with CO as the major oxidation product, but the reactor efficiency decreased as the engine was operated at leaner conditions, due to lower temperatures and lower NO, levels. Levels of nitrogen oxides above 300 ppm were shown to strongly promote the extent of UHC oxidation. Injection of hydrogen peroxide increased the degree of exhaust reactor oxidation and extended the oxidation further into the lean operation range. A field engine was tested at increased NOx levels, obtained by addition of ammonia to the air intake. No physical modifications of the engine or the settings were performed. The ammonia addition resulted in a reduction of unburned hydrocarbons by approximately 30% with CO2 as the major product. Due to the comparatively low temperature and short residence time of the field engine exhaust system, as well as the absence of CO production, the UHC reduction was attributed to processes occurring in the cylinder or exhaust port, rather than in the exhaust system. Similar levels of UHC reduction prior to the exhaust reactor were observed in the test engine. A detailed chemical kinetic model was used for simulation of the exhaust oxidation experiments. The modelling predictions were in fairly good agreement with the observations, confirming the catalytic role of NOx in the oxidation of hydrocarbons. The model was used to extrapolate the test engine results to conditions representative of co-generation engines and the practical implications are discussed.