An experimental investigation of Impact of ZrO2 nanoparticles in DI engine performance

Many investigators have examined the effluent of different types of nanoparticles on emission characteristics and performance of diesel engine but most of the present studies have been concentrated only diesel or biodiesel that contain dispersed nanoparticle. In the present work, water in diesel Nano-emulsified fuel was prepared by high speed rotor-stator homogenizer, and then addition of (50ppm, 100ppm, 150ppm) Zirconium oxide ZrO2nanoparticle blended water-diesel nanoemulsion (WiDNE). The objective of this project is to evaluate the effect of ZrO2 nanoparticles on combustion characteristics and engine performance. Direct injection (DI), water cooled four cylinders, in-line, natural aspirated Fiat diesel engine was used and run at a constant speed (1500 rpm) and constant fuel injection pressure (400 bars) with varying the operation load. The concentration of the emission gases such as NOx, unburned total hydrocarbon HC, CO and CO2 was measured by Multigas analyzer model 4880. The engine exhaust smoke emissions were measured using the AVL-415 smoke meter. The experimental results notified that WiDNE+ZrO2 fuel imposes the capability to enhance fuel properties, improve the engine efficiency as well as reduction in the emissions concentrations of exhaust gas.


Introduction:
The necessity in air quality enhancements and the existing cost of fuel requires alternative fuels for vehicles and CI engines. The traditional sources of energy are being brought down very quickly and the world is in the direction of a global crisis. The basic task nowadays is exploitation of non-conventional resources of energy for generation of power. Non-conventional fuels are also known as Alternative fuels. Methanol, Biodiesel and Ethanol are alternatives for petroleum and can be used in diesel engines (internal combustion) with very slight or no modification. The day by day, increasing in the use of diesel engine in numerous fields, especially in power generation and agriculture application, increasing the request of diesel fuel, due to lack of green spaces in Iraq and the large number of factories, toxic emissions of transport and high temperatures in a long summer lead to global warming, made challenge to reduce these emissions. Severe rules on emission of diesel engine are promoting to the use of alternate fuels and emissions reduction technique. Environmental Air quality and human health concerns have driven the legislation to other emissions of internal combustion engine, with significant consideration paid to particulate matter and nitrogen oxides (NOx, PM) [1]. Short-term exposing to high concentrations of NO 2 can cause inflammation of the air ways and more longer term exposure to low levels, increasing capability to respiratory toxicities and to allergens, and nitrogen oxides are known precursors to photochemical smog .Further rigid regulations on exhaust gas emissions drives a foremost research endeavor in engine improvement in order to diminish these pollutants [2].
The most control strategy of the NOx depends on lowering the heat of combustion or decreasing the duration time of the diffusion flame period, due to the thermal dependent of the NO formation and therefore NOx compounds [3]. Water in diesel Emulsions for use in engines (internal combustion) are simply applicable alternate fuels for the present vehicles. The emulsified fuel is defined as dispersion of water in conventional diesel with a certain surfactants, additives, for stabilizing water droplets in the system. There is a great interesting in the use of water in diesel emulsions and the main reason is due to the importance of the environment.
Existence of water droplets has an important impact on several emission components: exhaust gases such as nitrogen oxides (both NO and NO 2 , which are collectively referred to as NOx) and carbon monoxide (CO), as well as particulate matter and black smoke [4]. The water and Diesel fuel with water content normally range from 10% to 20%.
Their generally consistent conclusion is that the right water ratio of emulsified diesel can improve the fuel economy and emissions of diesel engine [5,6].Addition of Nano fluids along with the emulsified fuel and using it as fuel finds attraction for improving the performance of the diesel engine further. In the present work, influence of a Nano fluid on the emission and performance parameters of a compression ignition engine fuelled with water diesel Nano fluid emulsion was studied experimentally. An exciting concept for improving combustion of the traditional liquid fuels is the use of energetic materials in Nano scale as additives for fuel.  Table 1. The formula used to calculate the HLB value is given as:  Table 2.

Experiment Details:
The pure diesel, WiDNE fuel with and WiDNE+ZrO 2 at different nanoparticle level were charged into a variable CI diesel engine at compression ratio 17 for analyzing its behavior. The engine was coupled to a hydraulic dynamometer through which the load was applied by increasing the torque. Multigas model 4880 emissions analyzer was used to measure the concentration of NOx, unburned HC, CO 2 and CO. The engine exhaust smoke emissions were measured using the AVL -415 smoke meters. Table 3 shows the specifications of the exhaust gas analyzer. to assure complete distribution into the nanoemulsion in Fig.3 shows combustion mechanism of additives with the WiDNE.

Fig. 3:
Schematic illustration of combustion mechanism of Nano-additive in emulsion inside the fuel chamber of the diesel engine. [14].
ZrO 2 nanoparticle used to study the effect of nanoparticle dispersed into WiDNE on CI engine. Table 4 shows the specifications of ZrO 2 nanoparticle. (Supplied by sky spring company, USA).  Table 5. The photograph of diesel engine is shown in Fig.4. It was perceived that the BSFC decreased when the load was increased for all processes of diesel and Nanoemulsions blends, as shown in Fig. 3 due to the consumption of more fuel [7]. It is observed that WiDNE shows higher BSFC as compared to conventional diesel and nanoparticle blended water in diesel Nanoemulsions. This is maybe due to the higher viscosity and lower heating value of water diesel emulsions as compared with diesel [8,9].
It was also observed that BSFC decreases when nanoparticle volume fraction in the Nanoemulsions blend was increased for any given load. This reduction in fuel consumption can be due to increase in calorific value with the addition of the nanoparticle [10,11]. Potential advantage of the water in diesel Nanoemulsions fuels is the integrated influence of secondary atomization and micro-explosion phenomenon, resulting in strong vaporization and mixing better of air, turns in improving the combustion reactions inside the engine cylinders. Influence of ZrO 2 on BSFC was investigated and it is illustrated through Fig.5. There was an apparent effect on reduction of BSFC with increasing of ZrO 2 concentration in WiDNE Due to high catalytic activity of ZrO 2 nanoparticles blended fuels, which facilitate improved combustion and improved combustion characteristics [15]. With increasing of ZrO 2 from 50 ppm to 150 ppm, BSFC reduced. The effect of 50 ppm of ZrO 2 blended in WiDNE is barely recognized when compared with the net diesel but it is more effective for BSFC reduction with increasing concentration.

Brake Thermal Efficiency (BTE):
It was perceived that (BTE) increased when the load was increased for all operations of diesel and nanoemulsion blends as obvious in below Fig.6. It was observed that the conventional diesel shows lower Brake thermal efficiency as compared to WiDNE and nanoparticle blended water in diesel Nanoemulsions [8,9].   Fig. 6 it is obvious that the increase of thermal efficiency of WiDNE on net diesel fuel.
The enhancement of thermal efficiency was observed with ZrO 2 nanoparticles. There was an apparent effect on increasing of thermal efficiency with increasing of ZrO 2 concentration in WiDNE. With increasing of ZrO 2 from 50 ppm to 150 ppm, the thermal efficiency increased.

Nitrogen Oxide (NOx):
The experiments on the NOx emission by diesel engine were carried with net diesel fuel and increasing with the all operations of diesel and Nanoemulsion blends as shown in below Fig.7. It is observed that WiDNE reduces NOx emission as compared to conventional diesel. Water molecules presents in emulsified fuel possess very high latent heat of vaporization, which tends to reduce the peak cycle temperature, hence oxides of nitrogen emission of water diesel nanoemulsion were found on the lower side as compared to diesel fuel for all the power output.
It is discovered that the water in diesel emulsion with 15% water content produces the less amount of NOx emission as compared to the net diesel fuels [12].It was also observed that the NOx emission gives effects when the nanoparticle volume fraction in the nanoemulsion blend was increased. It is observed that the nanoparticles addition to diesel fuel decreases the NOx emission [13]. Influence of ZrO 2 on NOx emission was studied and it is shown through Fig. 5.
There was a little reduction in NOx emission with increasing of ZrO 2 concentration in WiDNE.
With increasing of ZrO 2 from 50 ppm to 150 ppm, the NOx emission decreased.

Smoke Opacity:
Diesel fuel showed the higher magnitude of Smoke opacity over the entire load range. It was noticed that the Smoke opacity increased when the load was increased for all operations of diesel and Nanoemulsion mixers, as shown in below Fig.8.

Carbon Monoxide (CO):
Carbon dioxides are coming as exhaust resulting from combustion of CO inside cylinder and complete combustion of carbon particles of the fuel. Carbon monoxide is extremely depending upon the air-to-fuel ratio comparing with stoichiometric ratio. In most cases, CI engine functions with lean mixture and thus results in lower CO emission. It was noticed that the CO emission decreased when the load was increased for all operations of diesel and Nanoemulsion blends, as shown in below Fig.9.
WiDNE fuel showed the higher magnitude of CO emission over the entire load range. It was also observed that the CO emission decreased when nanoparticle volume fraction in the Nanoemulsions blend was decreased for any given load. This reduction in CO emission because of nanoparticles will easily separate the oxygen atom from the water molecule which ensures complete oxidation of fuel droplets. In addition to it better air and fuel mixing rate was achieved inside the combustion chamber due to finer atomization of emulsified fuel droplets, which ends up with complete combustion. Decreasing in CO emission was observed from Fig.9.when blending ZrO 2 nanoparticles with WiDNE. Surface area of ZrO 2 is 20-30 nm which makes it easier for atomization process.

Unburned Hydrocarbon (HC):
HC emissions are producing due to the incompletion combustion and they tend to decline with load increasing. The total HC emissions are commonly made as a consequence of flame quenching. The formation of higher HC and CO emissions is extremely relied on the viscosity of fuel. More viscosity is also leading to longer spray penetration rate. The formation of higher HC emissions is due to the wetting cylinder of engine by incomplete combustion .It was observed that the HC emission decreased when the load was increased for diesel and Nanoemulsions blends as shown in Fig.10 due to the increase of combustion temperature. It is observed that WiDNE showed higher HC emission as compared to conventional diesel and nanoparticle blended water in diesel Nanoemulsions.
It was also noticed that the HC emission decreased as nanoparticle volume fraction in the Nanoemulsions blend was increased for all loads. At peak load condition, the HC emission of water diesel Nanoemulsions was quite higher than diesel fuel.  These Fig.10 show that at low load situation, the HC emission of diesel was less than WiDNE. With increasing the load, the HC emission will reduce with increasing the load. At high load the emissions by WiDNE will be less.
When using diesel fuel, there is a small increase of HC emission with increasing the load, but the curve will back down to become less than the net diesel in HC emission. The improvement of HC emission was observed with ZrO 2 nanoparticle blended with nanoemulsion in their respective concentration, as in Fig. 8.

5 Viscosity:
The higher temperature, the greater kinetic energy is for the emulsion particles. This continued increase increases the collisions of the molecules with each other and thus leads to a decrease in fluid viscosity, as clarified in Fig.11. It was observed that viscosity of emulsion fuel decreases when the temperature increasing.
The effect of lower viscosity decreases as the temperature rises and upon arrival to the stage, there is no heat effect for the viscosity.
All experiments were done in 60 seconds and 100 rpm for spindle rotating inside the fluid.
Above 100 o C, water begins to boil and separate from the nanoemulsion.

Conclusions:
Major purpose of this study is the comparative analysis of WiDNE and WiDNE+ZrO 2 nanoparticle on emission characteristics and engine performance of 4 strokes, CI diesel engine.