An Experimental Investigation of Combustion Emissions and Diesel Engine Performance of Water in Diesel Nano Emulsion Fuel

Water in Diesel Nano-Emulsions (WiDNE) fuel are an important environmental fuels for decreasing the combustion pollution of diesel engines. WiDNE fuel is a dispersion stable thermodynamic and kinetic system consisting of diesel oil, surfactant and water phase. WiDNE fuel due to their nano scale droplet size (20–200 nm) and large surface area burns more completely and hence a reduction in emissions than straight diesel. The objective of this project is to evaluate the combustion characteristics of WiDNE fuel prepared by rotor-stator homogenizer using mixed surfactants based on nonionic emulsifiers SpanTM 80, TweenTM 80. Direct injection (DI), Fiat engine was used and run at 1500 rpm, constant fuel pressure (400 bar) with varying the operation load. Multi gas analyzer model 4880 was used to measure the concentration of the emission gases such as NOx, unburned total hydrocarbon HC, CO2 and CO. The AVL-415 meter was used for smoke emissions. The experimental results of WiDNE imposes the capability to improve fuel properties, the engine efficiency as well as reduction of gas emissions.


Introduction
Diesel engines offer better fuel to the modem industries and technology, and in another hand they assumed of the large pollution source, especially are particulate matters, smoke, nitrogen & sulfur oxides of, hydrocarbon, carbon oxides [1]. Increasing environmental regulation drives a major research in order to reduce the exhaust pollutants [2, 3].
Various works have been reported for improving fuel performance and reducing pollution.
One such approach is the use of emulsions of water-diesel which have an effect on several emission constituents [4,5,6].
In this study an attempt was made to impart nanotechnology in the field of diesel fuels in order to make use of water droplets in nano size can be injected uniformly along with conventional diesel fuel in compression ignition engine and tested for its performance and emission characteristics.

No.20 Journal of Petroleum Research & Studies (JPR&S)
149 The objective of this study is to prepare WiDNE fuel using based Span™ 80 & Tween™ 80 surfactants. Concentration of the emission gases such NOx, unburned total hydrocarbon HC, CO 2 and CO were also studied.

WiDNE Preparation and Properties:
Diesel fuel was used for WiDNE preparation as the continuous emulsion phase. The

Engine setup and experimental method:
Fiat engine was used in this work to test the diesel fuel and its detailed specification is listed in Table (2).
The engine was coupled to a dynamometer and the load was supplied by the torque.
Multi gas model 4880 analyzer was used to measure the concentration of emission gases.
The smoke emissions were measured by AVL -415 meter. The schematic of the experimental setup is shown in Figure (2). Initially diesel fuel was tested for its performance and emission characteristics and then followed by WiDNE fuel was tested in the same engine and their results were compared against the base diesel fuel.

Brake Specific Fuel Consumption (BSFC)
BSFC of an engine is defined as the amount of fuel used in kgs per Kwhr. Figure 3 shows the brake specific fuel consumption (BSFC) variation with load (brake mean effective pressure).
The results shows that the BSFC increases when used the WiDNE fuel. The water content increases the combustion efficiency by keeping the temperature in the suitable range. It can be seen that the BSFC values for WiDNE fuel was less than that of individual diesel fuel.
The BSFC decreases at all conditions as shown in Figure (3). The effect may be due to the increase of the evaporation rates, which is led to reduction in the ignition delay with increasing surface area to volume ratio which improve combustion efficiency.

Emission Characteristics
When the WiDNE fuel is used, the exhaust gas temperature decreases. The smoke, Hydrocarbon HC, CO, NOx are decreases as shown in Figures (5, 6, 7 and 8).

Smoke Opacity
The relation of smoke opacity vs. load bmep was shown in Figure (5). The smoke opacity WiDNE fuels is lower due to uniform fuel mixture, thus combustion rate would increase and the gas phase oxidation and thermal cracking will decrease. Also, the water absorbs heat which would reduce the cylinder temperature. Thereby reducing the smoke formation could reduce [9, 10]. The HC emission for Diesel is higher compared to WiDNE fuel due to its lower thermal efficiency resulting in incomplete combustion. This could be due to improved combustion characteristics of WiDNE fuel, which leads to improved combustion.

CO Emissions
CO is emitted as a result of incomplete fuel combustion. This emission highly depends on the air to fuel ratio [11]. Figure (7) observed that there is a decrease in CO emissions, which possibly related to the short ignition delay and the enriched ignition characteristics of nano droplets in the WiDNE fuel due to improving fuel air mixing in the combustion chamber [12]. 155 formation of NOx. In general, the WiDNE used will reduce the flame temperature and then resulting in measurable reductions in the NOx emissions. [13][14][15][16][17].