Performance, emission and economic assessment of clove stem oil–diesel blended fuels as alternative fuels for diesel engines
Introduction
Most of the energy used in the world is supplied by fossil fuels. Burning of fossil fuels generates waste materials, mainly emissions to the atmosphere in the form of exhaust gases and dust, as well as some ash. These emissions have hazardous effects on the environment, some of them locally, others with more widespread or even global impact. Not only does the continued use of fossil fuels pose a serious threat to the environment, but also liquid hydrocarbon fuel deposits are exhausted. These problems of fuel diminishing and negative environmental impact of fuel can be addressed by using of renewable biofuels.
A large amount of energy consumed in Tanzania is imported. Tanzania is seeking to utilize its renewable energy resources, in order to alleviate the increasing import burden of energy and adapt a sustainable approach towards energy application.
Clove tree, which is a kind of biomass, is one of the most commonly cultivated plants in Tanzania. Clove products are very important sources not only for food and pharmaceutical products but also for biomass fuel production. All parts of the clove plant (stalk, stem, leaf, etc.) can be evaluated in energy applications.
The cloves generate substantial quantity of solid by-products known as clove stems, which are less commercial. With some additional processing clove stems can produce clove stem oil (CSO). It is used as a less expensive replacement for clove oil. The identification of the local market for the applications of CSO could add value to the clove crop which has been struggling in the world market to retain a good price. This will motivate the clove farmers and enhance the clove production, thus generating more revenue for the farmers. The utilization of the by-product of cloves towards bio-oil production for an alternative fuel for diesel engines could provide an inexpensive fuel and minimize Tanzania's dependence on imported petroleum base fuels. CSO is non-edible oil; hence it could be reasonable to investigate the potentiality of the usage of CSO as an alternative fuel for diesel engines.
In order to understand all tangible and intangible benefits and promote the application of CSO in Tanzania, a comprehensive analysis of the economic assessment of the CSO–diesel blended fuels as the alternative fuels for diesel engine from a social standpoint is required. A comparison of just the fuel cost per mile or kilometre without consideration of environmental externalities and other costs can be misleading and can result in erroneous conclusions. Therefore, the aim of this study is to fill the current gap in literature and increase the knowledge regarding the performance, emission formation and economic assessment of the CSO–diesel blended fuels as the alternative fuels for diesel engine. Our recent study [1] of the comparative performance and emissions study of a direct injection diesel engine using blends of diesel fuel with CSO is extended to incorporate the economic assessment of the CSO–diesel blended fuels as the alternative fuels for diesel engine.
Section snippets
Oil extraction process
CSO is obtained by distillation. Firstly, the clove stems are placed in a large stainless-steel vessel, separated into layers to reduce compression. Steam is then passed upwards through the vessel, boiling the clove stems and carrying away with it the raw CSO. The steam with raw CSO is condensed and much of the remaining water runs off. The raw CSO is then further purified by a process of partial distillation and the final oil is obtained after filtration. Tests are carried out on the finished
Fuel properties
There are a number of fuel properties that are essential to the proper operation of diesel engine. The addition of any CSO to diesel fuel affects certain key properties with particular reference to blend stability, viscosity and lubricity, energy content and cetane number (CN). These modifications of fuel may change the fuel spray characteristics, combustion characteristics and emissions formation. Therefore, before the engine testing was embarked, basic physical, chemical and fuel related
Experimental equipment and procedures
Testing was conducted on a four cylinder, four stroke, naturally aspirated, water cooled, direct injection Isuzu Diesel engine with a bore of 93 mm, stroke of 92 mm and compression ratio of 18.4:1. The engine was directly coupled to an eddy current dynamometer using a flexible coupling and a stub shaft assembly. The maximum torque of the engine was 162 Nm at 2000 rpm and the rated power was 43 kW at 2800 rpm. No adjustment was made at the fuel injection timing, i.e. at 20° before top dead centre
Framework for economic analysis of CSO–diesel blend fuels
For a fair comparison of the different operating modes, all costs (direct and indirect costs) that will be incurred over the lifetime of the vehicle should be taken into account. This can be achieved by using a societal life cycle cost (LCC) technique. LCC is the systematic, analytical process of comparing alternatives from original source to final end, with the objective of choosing the best alternative. The LCC key cost components are summarized in the flowchart of Fig. 1.
The LCC of vehicle
Fuel properties
The important properties of CSO are found out and compared with that of the pure diesel fuel (Table 1). It can be seen that the properties of CSO are quite comparable to that of the pure diesel fuel. The viscosity of CSO lies between the minimum and maximum required values of the pure diesel fuel. It has very low CN and high density. The energy content of CSO (33.55 MJ/kg) is slightly lower than that of the pure diesel fuel (43 MJ/kg). The energy content of CSO–diesel blended fuels decreases as
Conclusions
In this study the performance, emission and economic evaluation of using the CSO–diesel blended fuels as the alternative fuels for diesel engine has been carried out. Experiments were performed to evaluate the performance and emissions of the CSO–diesel blended fuels as the alternative fuels for diesel engine. The societal LCC was chosen as an important indicator for comparing different operating modes. The findings of the study are summarized below as follows:
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The CN of CSO prohibits its direct
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