1. Introduction

A very strong debate on the gradual substitution of petroleum by using renewable alternatives such as biofuel dominates the political and economic agenda worldwide [1]. This has been driven by the global concern of the international governing bodies for countries to

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comply with the requirements for emission reduction. The energy independence and security act of 2007 (US) requires the production of 36 billion gallons of renewable fuels including ethanol-based fuels by 2022. This constitutes a 75% increase in their production over the next 14 years [2].

CN, and flash point relative to that of ethanol, the obstacles due to ethanol are partially overcome. Literature concerning the use of n-butanol/diesel fuel blends in diesel engines and their effect on the steady state performance and exhaust emission in engines is limited [15]. Most of the studies, however, have evaluated the potential of methanol and ethanol [16], while there is a need for more studies to be done on the characteristics of higher alcohols such as

n-Butanol-Diesel (D2) Blend Fired in a Turbo-Charged Compression Ignition Engine: Performance and Combustion…

http://dx.doi.org/10.5772/intechopen.72879

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The general objective is to reduce the negative impacts of petroleum oil-based fuels in reciprocating engines on the environment through the use of oxygenated (alcohol) blends, without deteriorating the engine performance. The specific objective of the study is as

• To evaluate the performance and combustion characteristics of n-butanol-diesel blends: B5, B10, and B20. It is given in the abstract in a direct-injection, turbo-charged diesel

The study was conducted on a four-cylinder piston 1Z 1.9 L-66 kW Turbo-Direct injection (TDI) Wolkswagen diesel engine. The engine was fully equipped with a turbocharger with all the necessary sensors and actuators for stable operation of engine. The engine was warmed up to about 94C and the temperature was maintained. The engine was run for 20– 30 min to warm up with the reference DF or test blend fuel. Once the new fuel was pumped in, the engine was made to run for about 20 min to allow for stable operation of the new blend at test fuel conditions. Typical fuel consumption data and brake specific consumption are shown in Table 1. The fuel injection timings for the blends and DF controlled by the electronic diesel control (EDC) for different speeds of 1500, 2500, 3000, and 3500 rpm were 11,11,12, and 15 crank angle BTDC, respectively. The fuel consumption was measured using the AVL 7030 dynamic fuel consumption measuring equipment. Torque was measured by a Borghi and Saveri FE-350S eddy current dynamometer. The study was carried out for 75, 50, and 25% load for engine operating a range of 1500, 2500, 3000, and 3500 rpm. The engine was made to run for each measuring point on steady-state condition for about 2 min before recording values. An average based on three measurements for each test fuel was recorded. The engine operating conditions are shown in Table 2. The in-cylinder indicated pressure (IP) was measured by a piezoelectric pressure transducer Kistler KIAG 600. The top dead center (TDC) crank angle position was measured by an Optical Encoder HENGSTLER RI 32-

• To compare findings with studies that were carried out by others [18–20].

In this section the engine experimental set up, procedure and matrix are included.

propanol, butanol, and pentanol [17].

2. Objectives

engine.

0/1024.ER.14KA [21].

3. Engine experimentation

follows:

Biofuels constitute a renewable source of energy derived from biomass (the primary source). These include all three states of matter: solid, liquid and gas. They fall into the following categories, for liquid biofuels: (a) bioalcohols, (b) vegetable oils and biodiesel, and (c) biocrude and synthetic oils. It is expected that their demand in the future will rise because they replace petroleum [3]. Biofuels can be produced from bio-based materials through the biochemical processes such as pyrolysis, gasification, or liquefaction. Thermal chemical reforming of biomass concerns the process of catalytic or non-catalytic pyrolysis and gasification with a goal of maximizing in the production of energetically exploitable liquids or gases. Biofuels include bioethanol and biomethanol, Fischer-Tropsch liquids and biogas [4].

Oxygenated fuels including alcohols constitute one of the categories of the biofuels that have attracted research for many years due to their cleaner properties when blended with the conventional fuels [5]. Oxygenated fuels drew the attention of many researchers, due to their ability to drastically reduce the particulate matter (PM) emission without altering the emission levels of NOx, UHC, and CO [6, 7]. Oxygenated additives such as ethers, esters, alcohols have been added to diesel fuel [8]. Alcohols are used in internal-combustion engines as alternative fuels. If the source of alcohol is based on biomass then one can reduce greenhouse gas emissions, and exhaust emissions as well as enhance the overall energy efficiency [1, 3, 9–11].

N-butanol possesses certain qualities that make it more suitable to use in internal combustion engines than ethanol or methanol. These include a higher heating value of (28.4 MJ/L) for n-butanol and (21.2 MJ/L) for ethanol; higher cetane number (CN), lower auto-ignition temperature, better flow ability. For ethanol-diesel blend, an emulsifying agent is used to satisfy the homogeneity of the ethanol-diesel fuel mixture to prevent phase separation [12]. However, n-butanol is easily miscible in diesel fuel [13]. Within the functional groups of butanol isomers, n-butanol has the highest flame speed which enhances the combustion process [14]. Some researchers have argued that n-butanol-diesel blends prolong the ignition delay (ID), thereby affecting the combustion duration in internal combustion engines. However, others have stated that burning n-butanol-diesel fuel blends reduces emissions [14]. Therefore, comparisons are necessary on how the combustion characteristics differ between blends of n-butanol and biodiesel in diesel fuel, respectively.

In internal combustion engines such as diesel engines, diesel fuel is atomized into droplets using injectors at high pressure. These droplets entrain air as they evaporate into proportions that are combustible in the combustion chamber. The air temperature and pressure are above the fuel's ignition point. Therefore, after a short while: or ID the mixture auto ignites. ID is a time lag that is influenced by the physical chemical properties of the fuels measured in time (s) or CADs in engine cycles. This affects the combustion process in internal combustion engines including combustion duration and in-cylinder pressure and temperatures.

The simultaneous use of biodiesel, ethanol, and butanol in diesel is an interest that has arisen recently by researchers. However, since biodiesel is characterized by high viscosity, lubricity, CN, and flash point relative to that of ethanol, the obstacles due to ethanol are partially overcome. Literature concerning the use of n-butanol/diesel fuel blends in diesel engines and their effect on the steady state performance and exhaust emission in engines is limited [15]. Most of the studies, however, have evaluated the potential of methanol and ethanol [16], while there is a need for more studies to be done on the characteristics of higher alcohols such as propanol, butanol, and pentanol [17].
