Exhaust emissions of diesel engine with CuNO3 nano additive and butanol-diesel blends

This experimental study was focused on use of CuNO3 as a fuel additive with butanol-diesel blends in diesel engine and its effects on fuel specifications and emission characteristics. With this purpose, CuNO3 nano additive was mixed with diesel-butanol and each test fuel was analyzed to determine fuel specifications (density, viscosity, Cetane number, heating values and copper strip corrosion). A four stroke, four cylinder direct injection diesel engine was conducted to perform the test fuels. In conclusions, CuNO3 nano additive with diesel-butanol blends improved the fuel specifications and exhaust emission characteristics of diesel engine.


INTRODUCTION
The low fuel consumption, high durability, reliability and performance make diesel engines most preferable compared other internal combustion engines [1]. However, the pollutant emissions especially NO x and PM from diesel engines have been a serious drawback for diesel engines [2]. Many researchers have studied to prevent the damage of diesel engines reducing the pollutant emissions of diesel engines without any depletion in performance.
The use of fuel additives in diesel engine is an alternative method to prevent the pollutant emissions and improve engine performance [3][4]. Many different fuel additive types (oxygenates, antioxidants (stabilizers), antiknock agents, fuel dyes, metal based additives, corrosion inhibitors) have been used in studies [5]. Especially oxygenates and metal based additives have been much attention by researchers nowadays [6]. Oxygenates and metal based additives improve the engine performance and reduce pollutant emissions in diesel engines. These additives make catalytic effect in combustion reaction and an effective combustion is occurred in combustion chamber [7].
Babu and Anand tested n-pentanol and n-hexanol with die-sel-biodiesel blends. They found that the use of n-pentanol and n-hexanol improved performance and emission characteristics of diesel engine [9]. Jiand and et al. added carbon coated aluminium nanoparticles into diesel in terms of different mass ratios. The results showed that carbon coated aluminium was quite conducive to thermal conductivity but had little influence on viscosity. The BSFC of engines decreased up to 13.3% and emissions characteristic of engine increased with nanoparticles [10]. N-butanol and diesel blends were used in a small size, modified, variable compression ratio diesel engine by Nayyar and et al. [11]. N butanol was added in diesel with 10-25% by volume. Engine tests were carried out to see its effects on engine performance and emissions. Results showed that Brake thermal efficiency increased by 5.54% while smoke and nitrogen oxides decreased by 59.56% and 15.96% respectively for B20. Jiaqiang and et al. used Cerium oxide nanoparticle in diesel engine. They found that metal-based additive improved combustion characteristics of engine and decreased the pollutant emissions [12]. Palladium and acetylferrocene was tested as metal based additives in diesel engine by Keskin et al. [13]. CO and PM emissions decreased significantly up to 60.07% and 51.33%, respectively with the use of palladium and acetylferrocene.
This study intends to investigate fuel specifications and emission characteristics of a diesel engine runned by diesel blended with butanol and CuNO 3 nano additive.

Preparation of blends
Butanol (B) was blended with diesel as a ratio of 5% and 10% volumetrically and CuNO 3 nano additive doped in these blends as 50 and 100 ppm. In experimental studies the alcohols rates in fuels have been preferred approximately with the rate of 5-10% by researchers [1]. Four different blends were prepared for engine test to see the effects of butanol and CuNO 3 nano additive on fuel specifications and exhaust emission characteristics of diesel engine. Each blend was named according to its rate in blends as B5Cu50, B5Cu100, B10Cu50 and B10Cu100.

Experimental setup
The schematic diagram of experimental setup is given in Figure 1. A direct injection, four cylinder, four stroke, water cooled Mitsubishi Canter/4D34-2A diesel engine with a displacement of 3907 cc, 115 mm stroke, 89 kW maximum power at 3200 rpm and 295 Nm maximum torque at 1800 rpm was used in tests. The engine was mounted to a hydraulic dynamometer. MRU OPTRANS 1600 was used to measure Smoke with ± 2% relative accuracy while MRU DELTA 1600 V was used to obtain CO, HC, NO and NO 2 with respectively 0-10%, 0-20000 ppm, 0-4000 ppm and 0-1000 ppm measuring range.
Exhaust emission tests were conducted at full load conditions and engine speeds from 1800-3200 rpm with a constant increment of 200 rpm. Each fuel was tested with three replicates and the averages of results were calculated. The same operating conditions were carried out for all tests.

The specifications of blends
The specifications of test fuels are represented in Table 1. Use of butanol and CuNO 3 nano additive improved the specifications of fuel. Viscosity and density decreased while slight increases were obtained for Cetane index and lower heating value. Copper strip corrosion was determined as 1A for all test fuels. Compared with diesel, maximum decrease in viscosity and density were obtained as 12.24% and 0.52% with B10Cu100. Cetane index and lower heating value were increased as 2.39% and 2.09% with B10Cu100. Figure 2 shows the comparison of CO between diesel and blends with butanol and CuNO 3 nano additive. The use of butanol and CuNO 3 nano additive led to significant decrease in CO. Maximum decrease was observed as 31.74% with B10Cu100 at 2000 rpm compared to diesel. Decreases in CO were obtained averagely 12.74% for B5Cu50, 15.71% for B5Cu100, 19.98% for B10Cu50 and 23.84% for B10Cu100. The use of butanol and CuNO 3 nano additive in diesel engine improved the combustion efficiency and temperature. Increase in combustion temperature led to burn fuel effectively.

Emission results
HC emission variations of test fuels are given with     load condition. NO and NO 2 emissions increased slightly with blends. Increase rates of NO and NO 2 for B5Cu50 and B5Cu100 was determined higher than those of B10Cu50 and B10Cu100. B10Cu50 and B10Cu100 led to increase averagely 5.04% for NO and 7.55% for NO 2 emission.
Influence of butanol and CuNO 3 nano additive on Smoke emissions is given in Figure 6. Significant decreases were obtained in smoke emissions. The use of butanol and CuNO 3 nano additive led to decrease averagely as 12.13% for B5Cu50, 27.90% for B5Cu100, 18.33% for B10Cu50 and 32.76% for B10Cu100. Maximum decrease rates were obtained at 2800 rpm for all test fuels.

CONCLUSION
This study focused on butanol and CuNO 3 nano additive as fuel additives in diesel engine. Butanol and CuNO 3 nano additive were added into diesel and each test fuel was analyzed. Actual engine tests were conducted to see the effects of butanol and CuNO 3 nano additive on engine emission characteristics. Results showed that viscosity and density decreased while slight increases were obtained for Cetane index and lower heating value. CO, HC and smoke emissions showed downward trend while NO and NO 2 emissions slightly increased. Consequently, the fuel specifications and engine emission characteristics were improved with the use of butanol and CuNO 3 nano additive as fuel additives in diesel engine.