تحسين كفاءة احتراق وقود الديزل باستخدام اضافات نانوية

Abstract

Abstract This study investigates the effect of nanoparticles fuel additives (ZnO) on the combustion performance of emission characteristics of diesel engine. Diesel fuel was mixed with the ZnO nanoparticle size in the mass fractions of (50 and 100 ppm) by using ultrasonicator.Direct injection (DI), water cooled four cylinders, in-line, natural aspirated Fiat diesel engine was used and run at a constant speed at (1500 rpm) and constant fuel injection pressure (400 bar) with varying the operation load. The obtained results were compared with those obtained when the engine run at the same conditions for the same diesel fuel but without ZnO nanoparticles. Measurements indicated that there was improvement in the thermal efficiency and the brake specific fuel consumption with increasing the dosing level of ZnO nanoparticles in the blended fuel. The emission results at all loads showed that NOx and smoke generated by ZnO blended fuels were less than those generated by diesel fuel. Diesel fuel produced CO and HC more than ZnO blended fuel at high load and less at low load.

Keywords :- combustion , diesel engine , nanoparticles additives , gases emission , zinc oxide .

Introduction Diesel fuels are most important produced fuels from petroleum refineries which also blend with selected conversion petroleum cuts to reach the desired specification for fuel combustion. Diesel fuel is essential for transport and heavy-duty engines. It contributes to the prosperity of the worldwide economy since it was widely used due to its high combustion efficiency, reliability, adaptability and cost-effectiveness. However, pollutant emissions were a major drawback. Emissions from diesel engines seriously threaten the environment and were considered one of the major sources of air pollution. It was proved that these pollutants cause impacts in the ecological systems, lead to environmental problems, and carry carcinogenic components that significantly endanger the health of human beings, they can cause serious health problems, especially respiratory and cardiovascular problems.Increasing worldwide concern about combustion-related pollutants, such as particulate matter (PM), oxides of nitrogen (NOx), carbon monoxide (CO), total hydrocarbons (THC), acid rain, and photochemical smog and depletion of the ozone layer had led several countries to regulate emissions and give directives for implementation and compliance. It was commonly accepted that clean combustion of diesel engines can be fulfilled only if engine development was

coupled with diesel fuel reformulation or additive introduction. In this way, methods to reduce PM and NOx emissions include high pressure injection, turbo charging, and exhaust after treatments or the use of fuel additives, which was thought to be one of the most attractive solutions. Improvement in the performance of diesel engines was an important challenge to be addressed, in the current era due to the fast depletion of fossil fuel resources as well as due to the harmful hydrocarbon and nitrogen oxide emissions. Efforts were also made for the reformulation of diesel fuel to reduce these harmful emissions without affecting the physicochemical properties of fuel such as viscosity, flash & fire point, and so forth [1–3]. Diesel oil was a fuel derived from petroleum and consists mainly of aliphatic hydrocarbons containing (8-28) carbon atoms with boiling points in the range of (130-370) °C. It was a blend of fractions of hydrocarbons heavier than those of the hydrocarbons in gasoline and with a lower H/C mass ratio, which determines the high emission of carbon compounds per unit of energy delivered to the engine. A reduction in consumption and improvements in the quality of diesel oil have been the object of study by various specialists, motivated by growing demands in the transport and electric sectors. Several additives were added to perform specific functions. Additives reduce emissions; improve fluid stability over a wider range of conditions; improve the viscosity index, reducing the rate of viscosity change with temperature; and improve ignition by reducing its delay time, flash point, and so forth[4]. Diesel additives can be classified according to the purpose for which they are designed. Pre flame additives were designed to correct problems that occur prior to burning and include dispersants, pour point depressants, and emulsifiers, which act as cleaning agents. Flame additives were used to improve combustion efficiency in the combustion chamber, to increase cetane number, to reduce the formation of carbon deposits, oxidation reactions and contamination of fuel and filters clogging by rust, and to inhibit potential explosions caused by changes in static electricity. Post flame additives were designed to reduce carbon deposits in the engine, smoke, and emissions[5]. The advent of the nanotechnology revolution brings with it a host of new potential health issues that may ensue following exposure to intentionally engineered materials, those materials that were designed to serve a particular technological function. New metal oxide nanomaterials were being developed for a wide range of novel applications. Addition of some metal and metal oxide in the form of nano-powder to the base fuel may enhance the properties of the fuels. This was due to the interesting properties of nano-particles like higher specific surface area, thermal conductivity, catalytic activity and chemical properties as compared to their bulk form. Many researchers have used nano-particles as additives in diesel as well as biodiesel as new hybrid fuel blends (Williams & Van den Wildenberg 2005) [6]. They reported properties of nano-particles such as size, thermal conductivity and chemical properties affect the performance and emission characteristics of engine. Reduced size of the nano-particles increased specific surface, surface to volume ratio, and surface area improving catalytic reactivity and magnetic properties as compared to their bulk form. Hence metal and metal oxide nano-particles addition to biofuel will improve the performance as well as reduce the harmful gases from engine exhaust [7].

Experimental Work Material and Method :Diesel oil fuel was brought from the Daura Refinery and ZnO nanoparticles were synthesized through sol-gel method with average size as (58.3 nm) and their detailed specifications were listed in Table (1). The nanoparticles were weighed by using (electronic-Analytical balance of (0.0001 gm) accuracy, sartorius type, the two samples of zinc oxide in the concentration of (50 ppm) and (100 ppm) were blended with diesel fuel. The mixing of zinc oxide nanoparticle in diesel fuel placed in an ultrasonicator set (sonic vibra cell, model (vc X 750) power (220-240 VAC, 40 KHZ ultrasonic frequency) The ultrasonication technique applied of ultrasound energy to agitate particles of the sample for about (4 hour) to obtain a uniform stable suspentionnano particle fluid. The modified fuel was used in the experiment immediately after preparation in order to allow for sedimentation to occur. Fuel Properties: Various physicochemical properties of both the base fluid (diesel) and nanoparticle added modified diesel was tested by means of standard ASTM methods under identical laboratory conditions. The results obtained were compared in order to investigate the effect of nanoparticle and their dosing level on the fuel properties which were given in Table (2). There were no significant differences observed in the flash point, density, kinemitic viscosity, cetane number due to the addition of zinc oxide nanoparticles in the blend.The(ZnO) nanoparticles were mixed with diesel fuel in (50 and 100 ppm) by ultrasonicator using frequency (20KHz) . Fiat an amount to produce this study. The engine was .run at constant speed (1500 rpm) and constant fuel injection pressure of (400 bar) with varying the operation of loads (0.6, 1.2, 2.4, 3, 3.5 bar) brake mean effective pressure (bmep).The experimental apparatus the engine in this study was direct injection (DI), water cooled four cylinders, in-line, natural aspirated Fiat diesel engine. The engine major specifications were shown in Table (3). The engine was coupled to a hydraulic dynamometer through which load was applied by increasing the torque. The Multigas model (4880) emissions analyzer was used to measure the concentration of nitrogen oxide (NOx), unburned total hydrocarbon HC, CO2 and CO. The analyzer detects the CO, CO2, HC, NOx, and O2 content. The gases are picked up from the engine exhaust pipe by means of a probe. A ray of infrared light (which was generated by the transmitter) was sent through optical filters on to the measurement elements. The engine exhaust smoke emissions were measured using the (AVL – 415) smoke meter.

Results and Discussion Performance Characteristics: In general, there was a decrease of the Brake Specific Fuel Consumption (BSFC) with an increase in engine load , the increase in (BSFC) at low load was a result of the incomplete combustion of fuel. It can be seen that the (BSFC) values for (DZnO50) and(DZnO100) blends are less than that of diesel fuel, and the (BSFC) decrease with increasing in (ZnO) dosing level. Emission Characteristics: The NOx concentration values increase with the increase of engine load for all types of fuels. The reactions forming NOx are highly temperature dependent, so the NOx emissions have a close relation with the engine load.Also, NOx

emissions decrease with (ZnO) level increase at all operation loads. As mentioned in performance results, the ignition delay reduced with using (ZnO) blended fuels compared to diesel fuel. The shorter ignition delay of (ZnO) blends leads to reduce the premixed burn fraction (PMBF) of combustion and this will reduce the combustion temperature which leads to decrease the NOx emissions. Premixed combustion, during which in-cylinder pressure and temperature were very high, plays an important role in NO formation. Techniques to control NOx formation are mainly linked to a reduction in combustion temperature during this phase of combustion.The reduction of smoke number with (ZnO) blends fuels can be attributed to the increase of oxygen content in the fuel. The difference between the CO emissions at high and low loads is quite clear. The CO emissions decrease generally with the increase of engine load.

Conclusions 1- The reduction in the ignition delay with increasing of nanoparticles level by virtue of enhanced surface area to volume ratio leads to more complete combustion. 2-The effect of calorific value increase with increasing of nanoparticles generate leads to increase the thermal efficiency and decrease (BSFC) with increasing the dosing level of (ZnO) nanoparticle in the blended fuel. 3-This reduction in the ignition delay with using (ZnO) blended fuels compared to diesel fuel leads to reduce the premixed burn fraction of combustion and this will reduce the NOx emissions due to decreasing the combustion temperature (t), it was found that the smoke emissions decrease with increasing (ZnO) proportion. 4-CO and HC were lower for (ZnO) nanoparticles blended fuels, due to high catalytic activity because of their higher surface to volume ratio and improving fuel air mixing which leads to improve the combustion. References 1-K. J. Baumgard and D.B. Kittelson, “The Influence of A Ceraic Particle Trap on The Size Distribution of Diesel Particles,” Sae Technical Paper 850009, 1985. View At Publisher . View at Google Scholarm. 2-G. Lepperhoff and G.Kroon, “Impact of Particulate Traps on The Hydrocarbon Fraction of Diesel Particles,” Sae Technical Paper 850013, 1985. View at Google Scholar. 3-M. Gürü, U. Karakaya, D. Altiparmak, snd A. Alicilar, “Improvement of Diesel Fuel Properties By Using Additives,” Energy Conversion and Management, Vol. 43, No. 8, Pp. 1021–1025, 2002. View at Publisher •View at Google Scholar•View at Scopus. 4-Williams and Van Den Wildenberg, Roadmap Report on Nano-Particles, November 2005. 5-J.Matthew, H.Calvin Li, AbdollahAfjeh, G.P. Peterson, Experimental Study of Combustion Characteristics of Nanoscale Metal and Metal Oxide Additives In Bio Fuel (Ethanol), Nanoscale Research Letters, 2011; 6:246. 6-M.W. Vincent, P. Richards and S.L Cook, “Particulates Reduction In Diesel Engines Through the Combination of A Particulate Filter and Fuel Additive” Sae F and L Congress, October 1998, 13 Pages.

7-Nubia M. Ribeiro, Angelo C. Pinto, Cristina M. Quintella, Gisele O. Da Rocha, Leonardo S. G. Teixeira, Lilian L. N. Guarieiro, Maria Do Carmo Rangel, Marcia C. C. Veloso, Michelle J. C. Rezende, RoseniraSerpa Da Cruz, and Maria De Oliveira, Ednildo A. Torres and Jailson B. De Andrade, “The Role of Additives For Diesel and Diesel Blended (Ethanol or Biodiesel) Fuels: A Review” Energy and Fuels 2007, 21, 2433-2445. Table (1) : Specifications of Zinc oxide nanoparticulars Item Specification Formula ZnO Appearance White powder Molecular weight 81.39 AMU SG/Density 6.61 g/cm3 Average particle size 24-71 nm Bulk Density 0.15 g/cm3 Specific surface area 15-25 m2/g Crystal phase Hexagonal

Table (2): physicochemical properties of both base diesel fuel and nano particle added modified diesel Tests base Diesel fuel Modified diesel fuel ASTM Added 50 ppm NanoZnO Added 100 ppm Nano Zno Specific gravity at 15.6 C0 0.8299 0.7981 0.780 D2298 Flash point 74 76 78 D93 Viscosity C.St at 40C0 2.1 2.8 2.95 D445 Sulfer content wt.% 1.22 1.21 1.2 Carbon Residue (RAMS) 0.11 0.09 0.07 D524 Cetane No. TNA 55 56 57 D2699 Ash wt.% Nil Nil Nil D4451-O2

Table (3) :Tested Engine Specifications Engine type 4cyl., 4-stroke Engine model TD 313 Diesel engine reg Combustion type DI, water cooled, natural aspirated Displacement 3.666 L Valve per cylinder Two Bore 100 mm Stroke 110 mm Compression ratio 17 Fuel injection pump Unit pump 26 mm diameter plunger Fuel injection nozzle Nozzle hole dia. (0.48mm) , Spray angle= 160o, Nozzle opening pressure=40Mpa