Elsevier

Fuel

Volume 104, February 2013, Pages 109-115
Fuel

Effect of diethyl ether on Tyre pyrolysis oil fueled diesel engine

https://doi.org/10.1016/j.fuel.2012.08.041Get rights and content

Abstract

Tyre pyrolysis oil (TPO) can be derived from waste automobile tyres by different methods and it can be used as a fuel blended with diesel in a diesel engine. In the present work, a study was made to use Tyre pyrolysis oil derived from vacuum pyrolysis oil as a fuel in a diesel engine with the help of an ignition improver. Experiments were conducted on a single cylinder four stroke DI diesel engine using TPO as a main fuel. The performance, emission and combustion characteristics of the DI diesel engine were investigated and compared with the conventional diesel fuel (DF). Diethyl ether (DEE) was admitted along with intake air at three flow rates viz 65 g/h, 130 g/h and 170 g/h. Results indicated that the engine performs better with lower emissions when DEE was admitted at the rate of 170 g/h with TPO. It was observed that NOx emission in TPO–DEE operation reduced by 5% compared to diesel fuel operation. HC, CO and smoke emissions were higher for TPO–DEE operation by 2%, 4.5% and 38% than diesel mode.

Highlights

► A method of converting of scrap tyres to Tyre pyrolysis oil (TPO) is explained in this paper. ► A way to utilise TPO as a fuel in diesel engines is described. ► The utilisation of TPO which is a low cetane fuel with an ignition improver on a dual fuel mode.

Introduction

Rapid depletion of petroleum fuels and environmental issues have made the fuel market to awake and find alternative solutions for the petroleum fuels used in mobility, power and agriculture sector. This has intensified the search for alternative fuels for internal combustion engines. One of the methods to derive alternative fuels is pyrolysis in which waste substances are converted into useful energy [1], [2]. Biomass-based fuels like methanol and ethanol etc., are some of the examples in which waste-to-energy is adopted, and these are used as alternative fuels for internal combustion engines. Attempts were also made to use wood pyrolysis oil and rubber pyrolysis oil as fuels in diesel engines [3], [4], [5]. Various methods were adopted to convert waste automobile tyres into Tyre pyrolysis oil and fuel analysis was done [6], [7], [8], [9], [10], [11], [12], [13]. Tyre pyrolysis oil was produced in a laboratory scale by vacuum pyrolysis method [13], [14]. The elemental composition of TPO obtained in the present work is given in Table 1. The oil collected for this study was untreated and it contains both low and high volatile fractions. The properties of TPO compared with reference fuel (diesel) are given in Table 2. The carbon content present in a hydrocarbon fuel is very important as it indirectly indicates the energy content of the fuel. The carbon content of TPO is lesser than DF and hence the calorific value is also lesser than DF. The ash content of TPO is higher than DF. The presence of ash content in a fuel can result in wear in injector, fuel pump, piston and piston ring, if it is used as a neat fuel. Blending TPO with diesel fuel may reduce this problem to a certain extent.

The performance, emission and combustion study was made on a single cylinder, four stroke, air cooled DI diesel engine using different blends of TPO and diesel fuel (10–70% at 20% interval on volume basis). The engine was able to run up to 70% TPO blended with 30% DF [15]. But the engine was not able to run with 100% TPO. The probable reason may be due to lower cetane number of the fuel that resulted in a longer ignition delay thereby delaying the start of combustion.

Fuels with very high cetane numbers can reduce the ignition delay to a greater extent. There are number of fuels such as dimethyl ether, diethyl ether and diglyme whose cetane numbers are greater than diesel. Out of these fuels, diethyl ether is found to be the most potential fuel. Diethyl ether (DEE) has a cetane number greater than 125. Dimethyl ether is more volatile than diethyl ether and is prone to create vapour lock problems in the fuel lines. Diglyme is also a high cetane fuel that can be used as an ignition enhancer but it is costly. The fumigation technique offers the advantages of easy conversion of the diesel engine to work in the dual fuel mode. Research works on dual fuel mode with volatile fuels, vegetable oils and low cetane fuels as injected fuel and gaseous fuels or ignition improvers as inducted fuel were well documented by many researchers [16], [17], [18], [19], [20], [21], [22], [23]. Dual fuel mode also offers increased thermal efficiency and reduced smoke emissions.

Experimental investigations were carriedout with ethanol as injected fuel and DEE as an ignition improver, in a single-cylinder, air-cooled, DI diesel engine producing 4.4 kW of power at 25 r/s in a dual fuel mode [24]. The DEE aspirated into the intake air was varied gradually to achieve a constant speed of 25 r/s at various loads. The quantity of DEE was progressively adjusted in such a way that the lower level of DEE was determined by the onset of unstable operation or misfiring and knocking observed from the pressure–crank angle diagram. It was reported that the engine can run smoothly over the entire range of loads, by the introduction of about 3% DEE. The brake thermal efficiency was found to be higher for ethanol with DEE than with diesel fuel operation. The ignition delay for ethanol–DEE was longer than that of diesel fuel at rated load. The CO and HC emissions were higher for ethanol–DEE than that of diesel fuel. The smoke and NOx emissions were lower for ethanol–DEE than that of diesel fuel.

Experimental investigations were carried out on a Volvo AH10A245 bus engine, using ethanol fuel as a main fuel and DEE was fumigated along with intake air [25]. In this study, DEE was used as an ignition improver. The cylinder pressure increased extensively with increase in DEE. The heat release evolution indicates earlier ignition, i.e. shorter ignition delay, and lower peak heat release for a higher flow of DEE. Such performance resulted in smooth running of the engine and low noise as well. It was also reported that hydrocarbon (HC) and carbon monoxide (CO) increased, and the NOx level decreased with increase in DEE.

The combustion, performance, and emission characteristics of a direct-injection (DI) diesel engine were studied using orange oil and diethyl ether (DEE) [26]. DEE was inducted as an ignition improver through the induction manifold and orange oil was injected into the engine through a conventional fueling device as a primary fuel. It was noticed from the results that the performance of the orange oil–DEE fuel was better than that of diesel fuel. The peak cylinder pressure and heat release rate were found to be higher for the orange oil–DEE fuel than those of diesel fuel. The hydrocarbon and carbon monoxide emission levels in the engine exhaust increased with orange oil–DEE compared with those of diesel fuel. The smoke and NOx emissions were lower with orange oil–DEE compared with diesel fuel. It is concluded that a diesel engine operated using orange oil–DEE gives simultaneous reduction in NOx and smoke emissions with better performance.

An investigation was conducted to study the influence of a cetane number improver on the heat release rate and emissions of a four-cylinder, high-speed diesel engine fueled with ethanol–diesel blend [27]. Different percentages of cetane number enhancer (0%, 0.2%, and 0.4%) were added to the blend. The results showed that: the brake specific fuel consumption (BSFC) increased, the thermal efficiency improved remarkably, and NOx and smoke emissions decreased simultaneously. Combustion characteristics that are comparable with those of the diesel engine are attained at high loads in ethanol–diesel blend operation if a cetane number improver is used. The combustion parameters of ignition time, combustion duration, and maximum heat release rate show a marginal difference, because the large evaporation heat of ethanol results in higher temperature reduction at low loads with a cetane number improver. Also reported is that CO emission increases remarkably at lower and medium loads with a cetane number improver.

In the present investigation, TPO was injected into the cylinder as the main fuel and DEE was inducted at three different flow rates into the cylinder along with intake air. The combustion performance and emission parameters of a single cylinder, four stroke, air cooled, DI diesel engine developing power of 4.4 kW at 1500 rpm was evaluated in comparison with diesel fuel operation.

Section snippets

Experimental setup

The schematic layout of the experimental setup is shown in Fig. 1. The specifications of the engine are given in Table 3. An electrical dynamometer was used to provide the engine load. An air box was fitted to the engine for airflow measurements. The fuel flow rate was measured on volumetric basis using a burette and a stopwatch. Chromel alumel thermocouple in conjunction with a digital temperature indicator was used to measure the exhaust gas temperature. A pressure transducer in conjunction

Ignition delay

The variation of ignition delay with brake power for TPO–DF blends and DF is shown in Fig. 2. The cetane number for DEE is greater than 125. DEE was introduced as an ignition improver, into the manifold along with the intake air. Higher latent heat of evaporation of DEE cools the surrounding air that enters into the manifold. The auto ignition temperature of DEE is 160 °C.

At the end of compression, due to the increase in the temperature of air-DEE, the DEE admitted starts to burn. However, TPO

Conclusion

From the results, it is observed that TPO–DEE at 130 g/h shows a better performance with reduced emissions compared to that of TPO–DEE 65 g/h and TPO–DEE 170 g/h. The engine is able to run smoothly when fueled with TPO with DEE at 170 g/h. The following conclusions are drawn from the experimental investigation:

  • The peak pressure for TPO–DEE with 130 g/h flow rate is higher by about 3 bar than DF at full load.

  • Ignition delay for TPO with DEE is longer by about 2.8 °CA than DF.

  • Thermal efficiency reduced

Acknowledgements

The authors sincerely thank the Ministry of Environment and Forests, New Delhi for their financial grant to carryout this research work. The authors also thank the Management of Rajalakshmi Engineering College, Chennai and Anna University for providing the necessary infrastructure to conduct the study.

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