di

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diesel oil burners to use liquid butane as an alternative fuel.

worlded, impable col prodrnativewest pf modesses t

tive fuels has motivated detailed studies of biofuels, fuel blends,polluting exhaust emissions and comparative analysis of fuel prices.

Generally speaking, biofuels seem to be attractive substitutes topetroleum-based fuels, mostly because the majority of biofuels areobtained from renewable sources and the greenhouse effect gasesare reduced. Nonetheless, experimental studies, such as the ones

From an economic point of view, an interesting result presentedby Demirbas [8] indicates that, even though biodiesel blends havelower economic performance than diesel oil (in terms of plantcapacity, process technology, rawmaterial cost and chemical costs),they are strong competitors of natural gas and diesel oil for urbantransportation and industries. Demirbas also remarks that biofuelsprovide the prospect of new economic opportunities by creatingjobs for people in rural areas of developing countries, which usuallyare highly dependent in oil consumption. However, Chang and Su

* Corresponding author. Tel.: 56 32 2654162; fax: 56 32 2797472.

Contents lists available at

a

sev

Applied Thermal Engineering 45-46 (2012) 1e8E-mail address: mario.toledo@usm.cl (M. Toledo).fuels that substitute diesel oil.Diesel and fuel oil are the most consumed fuels in the industrial

facilities and thermal power plants, which represents a majorproblem due to the permanent price increments and high specu-lation in oil markets. Additionally, as pointed out by Martyr andPlint [1], the hazardous pollution caused by handling andconsumption of diesel oil has contributed to the rapid environ-mental degradation, which turns unfeasible the use of these fuels inthe nearby future. Therefore, an opportunity to introduce alterna-

combustion of some biodiesel blends and the ammable/explosivenature of biogases, bioethanols and hydrogen-based fuels maybecome safety hazards and environmental drawbacks to theircomplete approval for commercial thermal machines. Nonetheless,with the appropriate treatment and manipulation, biofuels still aregood alternatives which mostly improve in the emission reductionof carbon monoxide (CO), unburned hydrocarbons (HC) andparticulate material (PM) as demonstrated in the studies by Sayinand Canakci [6] and Rodrigues de Souza et al. [7].1. Introduction

In the last two decades, with theprice of diesel oil has sharply increasburden to produce power at a reasoncommercial facilities and industriademands a constant search for alteefcient power generation at the lovital to analyze the feasibility ocurrently used for combustion proc1359-4311/$ e see front matter 2012 Elsevier Ltd.doi:10.1016/j.applthermaleng.2012.04.024wide energy crisis, theosing a huge economicst for residential needs,uction. This situations that ensure a highlyossible cost. Thus, it isifying the technologyo introduce alternative

presented by Yoon and Lee [2] and Crookes et al. [3], have proventhat some biofuels, under certain conditions, may retard the igni-tion phase and reduce the combustion performance, compromisingany cost-effective power generation. In the case of biodiesel blendsfrom vegetable oils, Agarwal et al. [4] explain that, without muchchemical processing, usually these blends present high viscositiesand fairly low volatility, causing high droplet size due to poor fuelatomization and jet-mixing. Hence, operational performance anddurability of combustion technology are severely reduced.

Also, as claried by Atsbury [5], the high soot formation from the 2012 Elsevier Ltd. All rights reserved.Liquid butane as an alternative fuel for

Alejandro Sez a, Alex Flores-Maradiaga b, Mario ToaDepartment of Mechanical Engineering, Universidad Tcnica Federico Santa Maria, Avb cole de Technologie Suprieure, 1100 rue Notre-Dame Ouest, Montral, Qubec, Cana

a r t i c l e i n f o

Article history:Received 9 January 2011Accepted 9 April 2012Available online 17 April 2012

Keywords:Liquid butaneDiesel oilDual injectionBurner

a b s t r a c t

The experimental tests peoil burner are presented. Fwith pressures varying froa complete characterizatiotemperatures and the mainfor both liquid butane andshapes, with low radiationand ame front positions.lower than those of diesel

Applied Therm

journal homepage: www.elAll rights reserved.esel oil burners

o a,*

aa 1680, Valparaiso, Chile

ed to study the combustion process of liquid butane employing a dieselhese tests, a dual pumping and injection system was designed to operate.8 to 2.0 MPa. Five distinctive cases were tested for each fuel, obtainingf the combustion processes in comparable conditions. Flame geometries,emical products of the combustion process were recorded experimentallyel oil. It was observed that liquid butane ames present elongated conicaln color at the base position, followed by a higher radiation zone in the coreo, the temperatures and NOx concentrations of liquid butane ames areames. In general, it is feasible to modify the combustion technology of

SciVerse ScienceDirect

l Engineering

ier .com/locate/apthermeng

al En[9] clearly explain that the great paradox of the conventional bio-fuel production and consumption, in favorable periods of high oilprices, is the shortage of basic foods used as rawmaterial (e.g., cornand soybean) that are fundamental part of the food security ofhumans and livestock. For that reason, they stress the need fora careful choice of the raw material to be used for biofuelproduction and suggest the selection of inedible algae-basedfeedstock.

Other researchers have focused on low sulfur gaseous hydro-carbons, such as n-butane, propane and natural gas, which gener-ally are liqueed to be injected in dual-fuel technology. Studies byHuang and Sung [10], Huang et al. [11], Lee et al. [12] and Yamasakiand Iida [13] have identied n-butane as one of the main substitutefuels for diesel oil, mostly due to its similar thermo-physical char-acteristics (important factor for dual-fuel systems) coupled withthe high combustion efciency and low emissions achieved by thetwo-stage autoignition process (i.e., low heat release stage, LTR, andhigh heat release stage, HTR).

In fact, n-butane (C4H10) is the fuel with lowest carbon numberof the parafn family found to interchange well in combustiontechnology with higher hydrocarbons (such as diesel oil), and hasproven to reduce signicantly the CO and PM concentrations inexhaust gases [12]. Additionally, the small carbon number ofn-butane is indicative of the fast chemical kinetics of its combustionprocess which aids the speed-up for autoignition and improvescombustion performance. However, this last characteristic haschallenged designers and combustion engineers, who need tocontrol properly the ignition timing and combustion duration atvery high temperatures and injection velocities [13].

Liquid n-butane (hereafter referred to as liquid butane) hasinspired different inventions over the past 60 years (e.g., Schy-lander [14], Pillard [15] and Kaufman [16]) and is becoming themainstream of substitute fuels in oil combustion technology [17,18].As Fleisch et al. [18] point out, just until recent years gas-derivedfuels could not compete with conventional petroleum-basedliquid fuels because gas-to-liquid conversion has been and still isan expensive process. But now, a signicant cost reduction fromimproved technologies and economies of scale has raised thecompetitiveness of liqueed gas fuels for commercial applications.Either for small-scale indoor purposes (such as the case presentedby Ghosn et al. [19]) or large-scale industrial purposes (such asmetal piece heating discussed by Wang et al. [20]), commercialdevelopers and users can benet from the quick gasication andignition of liquid butane for a more efcient combustion.

Consequently, the main objective of this study is to design andtest of a dual system for liquid butane and diesel oil injection ina Joannes diesel oil burner, aiming for the optimization of thiscombustion technology to facilitate the introduction of liquidbutane as the alternative fuel. For that purpose, rstly, the fuelinjection, jet-mixing and ignition systems are fully studied, anda new system of liquid butane injection complementary to that ofdiesel oil is proposed. Secondly, the experimental setup is imple-mented on a horizontal isothermal vessel, which includes instru-mentation for mass ux, pressure and temperature measurements,ue-gas analysis, PLC automation, solenoid valves, water pumping,fuel injection and security systems. Finally, diesel oil and liquidbutane combustion are investigated, respectively.

This research article presents the nal results obtained with thenew dual injection system. In Section 2 the general set-up of thetesting bench is detailed. Then, the simplied radiation model usedfor thermal performance assessment is presented. The experi-mental results for both fuels are discussed in Section 3, empha-sizing on the main features and benets of liquid butanecombustion. Finally, in Section 4 the concluding remarks are

A. Sez et al. / Applied Therm2presented.2. Experimental setup and methodology

2.1. Isothermal reactor and instrumentation

For this study, a horizontal vessel of 550 mm in diameter and1650 mm long, with a 180 mm diameter exhaust pipe, was adaptedto operate as an isothermal reactor. Its furnace interior, which hashigh alumina refractory coating, is surrounded by a cooling watercircuit which maintains a stable temperature prole, aided bya two-step heat exchanger that removes heat transported by thecooling water. Additionally, the AZ14 Joannes diesel oil burner,designed to generate amaximum power of 180 kW, was installed totest the dual-fuel system.

The schematic design of the dual injection system is presentedin Fig. 1. Diesel oil is stored in a 45 L tank and is injected witha Suntec fuel pump at 0.8, 0.9 and 1.0 MPa. Liquid butane is fedfrom a low-pressure cylinder (0.25 MPa) into a variable ux fuelpump that rises the fuel pressure between 1.0 and 2.0 MPa. Thesehigh-pressure lines are connected to a liquid accumulator andpressure reduction valves that adjust the nal injection pressure.The fuel ow is controlled primarily by automated solenoid valveswhich obey to a sequence program launched by a PLC and moni-tored from a remote computer. Whenever a change in time oroperating sequence is needed, the program is modied, recompiledand reloaded into the PLC.

Diesel oil and liquid butane ow rates are measured by a rota-meter calibrated in situ, and a digital volumetric ow-meter is usedin the cooling water circuit as well. Also, to adapt the power outputto the reactors capacity, the original burner nozzle of 3 GPH wasreplaced for a 1.75 GPHnozzle. This is amajor change in the burnerssystem based on the need of a low power range control. For thisexperiments, a Danfoss pressure-swirl nozzle (of 2.94 kg/h, HRhollow cone, 60 degrees spray) was employed to obtain the desired1.75 GPH fuel injection. A schematic diagram of this nozzle, with itscomponents and dimensions, is presented in Fig. 2.

Five type R thermocouples of 0.75 mm in diameter andplatinumerhodium coating (13% rhodium) were used to scanthe furnace wall temperatures along the combustion chamber.Also, a type K mobile thermocouple (1.5 mm in diameter andchromeealumel coating) was installed to measure the ametemperature at ve positions along the centerline and ue-gastemperatures at 1500 mm from the exhaust pipe entrance. Theame and wall temperatures at the burners exit (rst position,0 m) were obtained with a LumaTech infrared pyrometer(measuring range:30 to 750 C) and two ue-gas meters (TESTO350-S and Bosch BEA 250-EU) were used in order to assess andcontrol combustion parameters in real time. A smoke meter, BoschEFAW 68A, was used to measure soot emissions.

For the ame geometry characterization and monitoring,a Sony HDR-FX1000 professional camcorder was employed formultiple imaging and footage recording. The captured images werepost-processed with the Adobe Premier Pro toolkit (Photoshop

CS5), using the furnaces dimensions as reference for the sizing ofthe ames, obtaining the integral scales of length and radius at theames base, core and front positions discussed in Section 3.

The operation sequence of this experimental hybrid systemwasdened as follows:

Air pre-cleaning of the combustion chamber is set to 10 s todrag any remaining unburned hydrocarbons from previoustests. In case of an emergency, the sweeping procedurecontinues for 3 min;

Turning-on the ignition spark is set for 13 s; Preheating the reactor and nozzle with a diesel oil ame is

gineering 45-46 (2012) 1e8done for 35 min;

done for 5 min; Combustion of liquid butane, waiting 25 min for stabilization

ual

A. Sez et al. / Applied Thermal Enbetween each case, and collecting relevant data is set for30 min; and,

The isothermal reactor is cooled for 60 min before shuttingdown the system.

2.2. Thermal performance calculations Dual injection and combustion of diesel oil and liquid butane is

Fig. 1. Design of the hybrid system for dThermal assessment of the combustion process is doneemploying a simple heat radiation model, by assuming a steady

Fig. 2. Pressure-swirl nozzle components and dimensions. Source: Danfoss HR/SR oilnozzle general datasheet.axisymmetric cylindrical ame concentrically aligned within thecylindrical reactor vessel. Gunn and Horton [21] remarked that forcylindrical furnace industrial boilers the dominant heat productionmechanism is thermal radiation. Thus, equation (1) is used tocalculate the mean heat transfer due to thermal radiation of theame _qf , which corresponds to the net energy absorbed by thereactors inner surface at each position, as presented by engel andGhajar [22] for a simplied ame radiation model.

4 4

injection of liquid butane and diesel oil.

gineering 45-46 (2012) 1e8 3_qf Afs Tf Tw

1= 3f 1=aw 1rf=rw

(1)

Here, the constant of StefaneBoltzmann (s) is set to 5.67 108 W/m2K4, and the mean ame and wall temperatures (Tf andTw, respectively) are averaged over 30 min of data collected every10 s at each of the ve control positions. Also, a constant ameemissivity ( 3f) of 0.8 for diesel oil ames and 0.5 for liquid butaneames, and a constant wall spectral absorption coefcient (aw) of0.8, are adopted for all the cases. This model considers a unity formfactor Ff/w 1, and the ratio of the ames longitudinal surfacearea (Af 2prfl) to the furnaces internal surface area (Aw2prwl) isreduced to the ratio of ame to wall radius (rf/rw), taking the sameame length scale (l) in each case.

Secondly, the net rate of heat transported by water _qH2O thatcirculates in the cooling circuit of the reactors shell is calculated bythe general relationship expressed in equation (2).

_qH2O _mH2OcpH2ODTH2O (2)

Here, the mean ow rate of cooling water _mH2O and thetemperaturedifferencebetween the inletandoutlet DTH2O DTo DTi are averaged over 30 min for each case. The water specic heatcoefcient at constant pressure is set to 4184 kJ/kg C.

Lastly, equation (3) represents the thermal absorption efciency(h), calculated from the ratio of net heat transfer of cooling water tothe mean ame radiation at each position.

h _qH2O_qf

(3)

3. Experimental results and discussion

The thermo-physical properties of both fuels are presented inTable 1. In general, the following assessment compares thecombustion performance based on the ames heat release, ue-gasemissions and the adaptability of the dual injection system to

From Fig. 3b, it is evident that geometries of liquid butaneames are different from diesel oil ames in size and shape. Underthe setting conditions listed in Table 2, liquid butane ames presentlarger sizes and more elongated conical shapes with respect to

Table 2Tested cases for diesel oil and liquid butane.

Fuel Case Pressure(MPa)

Flow rate(L/min)

Remarks

Diesel oil 1A 0.8 0.124 Constant air onblower scale to observeinjection pressureinuence for dieseloil (D.O.)

Diesel oil 2A 0.9 0.126Diesel oil 3A 1.0 0.138

Diesel oil 4A 0.9 0.141 More air at constantpressure for D.O.

Diesel oil 5A 0.9 0.160 Few air at constantpressure for D.O.

Liquid butane 1B 1.0 0.137 Constant air on blowerscale to observeinjection pressureinuence for liquidbutane (L.B.)

Liquid butane 2B 1.5 0.154Liquid butane 3B 2.0 0.179

Liquid butane 4B 2.0 0.134 More air at constantpressure for L.B.

Liquid butane 5B 2.0 0.188 Few air at constantpressure for L.B.

A. Sez et al. / Applied Thermal Engineering 45-46 (2012) 1e84Lower heat value, kJ/kg 44,602 45,742Vaporization latent heat, kJ/kg 277 386a diesel oil burner. The experimental tests are aimed to obtain resultsfrom pre-dened input parameters (i.e., fuel injection pressure andair excess) that yield useful output information for the analysis.Under these operating conditions, ve distinctive cases for each fuelwere performed (see Table 2) in order to trace a characteristicbehavior for their particular combustion processes. For this purpose,measurements of ame and wall temperatures, ame imaging andue-gas analysis were achieved. Note that, except for the cases 3Aand 1B with 1.0 MPa, the injection pressure ranges are different forboth fuels due to technological limitations of the testing bench. Themain difculty encountered was the high instability of liquid butanefor high-pressure variable ow-rate pumping which directlyaffected the fuel injection pressure. No doubt this system can beimproved to operate with a lower pressure range for liquid butane,but an adequate testing pumpmust be designed to handle such lowow rates in order to obtain a continuous fuel jet.

In the rst three cases for both fuels the inuence of changingthe injection pressure was observed, which permitted modica-tions in the fuel atomization; then, the last two cases were aimed toobserve the oxidizer inuence (air excess) in extreme operatingconditions. Each of these cases was observed during 30 min,allowing the temperature and fuel ow rates to reach a quasi-s-teady level before collecting data. The experiments were per-formed within a temperature range of 16e20 C and a humidityrange of 70e80%. At the starting point, all measuring equipmenthave been adjusted and double checked to minimize errors in theexperimental results.

3.1. Flame geometries and general characteristics

The diameter and length scales of diesel oil and liquid butaneames are shown in Fig. 3a and b, respectively. It is clearly observedthat for diesel oil combustion, with constant air input and variableinjection pressure, case 3A produces a large ame due to higher fuelconsumption. In contrast, keeping a constant injection pressurewith variable air input, case 4A produces a shorter ame due to anincrease of air excess, and case 5A produces the largest ame withsignicantly higher fuel consumption. In general, diesel oil amesdisplay a turbulent yellow-orange color indicative of high thermaland infrared radiation levels. Hence, it was noticed that as thefuel injection pressure raised the ame size increased and theyellow-orange colour became more intense, related to larger fueldroplets and more soot formation.

Table 1Thermo-physical characteristics of diesel oil and liquid butane.

Property Diesel oil Liquid butane

Density (at 20 C), kg/m3 840 585Viscosity (at 20 C), mm2/s 5.5 106 2.42 104Molecular weight, kg/kmol 142.28 58.12Higher heat value, kJ/kg 48,020 49,546

Specic heat (at 772 K), kJ/kg K 3.26 2.4

Thermal conductivity, W/mK 0.15 0.014Fig. 3. Lengths and radius of diesel oil (a) and liquid butane (b) ames.

Also, one can observe that, under the same operating conditions(cases 3A and 1B), the energy release is slightly better distributed forliquid butane ames.

Fig. 7 depicts the heat absorption efciency at ve positions forcases with an injection pressure of 1.0 MPa at constant air excess fordiesel oil and liquid butane (cases 3A and 1B, respectively). This arethe only two cases that can be compared directly for the reasonsexplained in Section 2, but are sufcient to get a good idea of theenergy transfer phenomenon. For the rst half of the chamber,Fig. 7 shows higher heat absorption for diesel oil combustion, then,decaying rapidly in the second half. This behavior was the same forall diesel oil ames, showing high heat concentration in the regionnear the nozzle. In contrast, the absorption efciency of liquidbutane combustion is poor very near the nozzle and improves asthe jet ame develops downstream in the chamber.With this resultone can infer that, in general, heat transfer is better distributed forliquid butane ames.

3.3. Combustion performance based on ue-gas analysis

A resourceful way to assess the combustion process of this dual

Fig. 4. Flame (a) and wall (b) temperature proles of diesel oil combustion.

al Enanalogous diesel oil ames. In all ve cases tested for liquid butane,the ames kept the same geometry, characterized by a cyan-bluecolour cone about 20 cm long at the base followed by a turbulentyellow-orange jet ame. At constant air excess, case 3B has a largerame due to the increase of fuel consumption and, with constantinjection pressure, case 4B yields a shorter ame with more airexcess and case 5B gives the largest ame as little air and more fuelenter the combustion zone.

Also, referring to Table 2, one can verify that any change of theame dimensions is tied to its corresponding fuel consumptionrate. At constant air, whichever increase in injection pressure yieldsa larger ame and, as a direct consequence, increases the heatrelease. Also, keeping a constant injection pressure, an increment ofair excess generates a shorter ame, and vice versa, affecting theheat release in the same proportion, which will be discussed inSection 3.2.

The cyan-blue colour cone at the base of the liquid butaneames indicates that part of the droplet stream evaporates veryquickly, changing to gas phase combustion almost instantaneouslyas it enters the combustion zone. This quick evaporation is highlydesirable in order to obtain autoignition and a good combustionperformance. Yet, a small yellow semi-sphere was observed at thebase of the ame, possibly caused by incomplete combustion ofresidual olens in the fuel stream. The second portion of the liquidbutane ames behave in a similar way to diesel oil ames bygenerating high radiation levels, except that the length is doubledin most cases. This phenomenon reveals that the combustion ofliquid butane may be incomplete at high injection pressures inaddition to the reactors limited volume, which is an importantfactor that should be considered for commercial purposes.

3.2. Thermal assessment of the combustion process

The ame and wall temperature proles for cases with diesel oilare illustrated in Fig. 4a and b, respectively. The maximumtemperature for diesel oil ames is 1096 K (obtained in case 3A)and themaximum temperature decay is approximately 350 K at theame frontal position. The maximumwall temperature is 748 K forcase 4A, with a maximum temperature decay of 150 K. Most of thetemperature proles show a peak temperature at a relative distance(x/L) between 0.4 and 0.5 from the injection nozzle. Based onthese experimental results for diesel oil, it is clear that walltemperatures follow similar trends to ame temperatures, thus,anticipating that the maximum heat transfer should be expected atthe same relative position (x/L w0.4).

Fig. 5a and b presents the ame and wall temperature proles,respectively, for liquid butane combustion. The maximum ameand wall temperatures are 974 K and 668 K, respectively, bothobtained in case 5B. Most of the ame temperature proles showa peak temperature at the second half of the ame (x/L w0.6),which is an expected based on the ame geometries. Hence, duringthe quasi-steady operation with liquid butane, the temperatureswere better distributed along the reactor compared to those ofdiesel oil combustion, mainly due to the elongated liquid butaneames which cover more heat transfer area of the furnace. Never-theless, liquid butane ames generate temperatures 120 K coolerthan the diesel oil ames, hence, it is expected to obtain slightly lessheat radiation with liquid butane.

To obtain a more insightful assessment of the thermal perfor-mance for both fuels, we can apply equations (1)e(3) presented inSection 2.2 to compare the heat absorption efciency of the coolingwater with respect to the ames energy release. Fig. 6 presents theame radiation generated with both fuels. It is readily veried thatthe peak thermal radiation for diesel oil and liquid butane occur at x/

A. Sez et al. / Applied ThermL w0.4 and 0.6, respectively, and their magnitudes are very close.gineering 45-46 (2012) 1e8 5system is to measure the exhaust gases of each fuel. The mean

Fig. 5. Flame (a) and wall (b) temperature proles of liquid butane combustion.

Fig. 6. Flame radiation for diesel oil (case 3A) and liquid butane (case 1B).

A. Sez et al. / Applied Thermal Engineering 45-46 (2012) 1e86ue-gas results in each case are presented in Table 3 andcompared graphically with respect to the air-fuel ratio, lambda,in Fig. 8.

Clearly, as the air excess increases, oxygen concentrations rise(Fig. 8a) and carbon dioxide is reduced in a proportional rate(Fig. 8b). Furthermore, one can observe these concentrations forboth fuels are very close with low air excess but start to separateover lambda w1.6, showing less CO2 production with liquidbutane at high ue-gas temperatures. Nonetheless, there is rela-tively more carbon monoxide concentration (Fig. 8c) with liquidbutane ames, which underlines the need to improve the purity ofthe n-butane fuel supply that may contain traces of heavierhydrocarbons.

In addition, concentrations of NOx (Fig. 8d) display the expectedtrends; i.e., both fuels yield high NOx levels for rich air-fuelmixtures and low NOx concentration for poor oxidizing

Fig. 7. Heat absorption efciency for diesel oil (case 3A) and liquid butane (case 1B).mixtures. From Table 3, comparing NOx concentrations for bothfuels with 1.0 MPa (cases 3A and 1B), diesel oil combustion yieldsa NOx level 6 times higher than liquid butane combustion. Thus, forhigher temperatures and fuel consumption, diesel oil amescontribute more to the emission of green-house effect gases thanliquid butane ames.

Finally, the soot emissions (Fig. 8e) also rise with increasingamounts of air excess, which indicates incomplete combustion forboth fuels. However, soot formation for liquid butane combustion itis consistently lower than diesel oil combustion, which hasa signicant environmental impact for air quality control.

Table 3Combustion products for diesel oil and liquid butane.

Case Lambda CO2 (%vol) CO (ppm) NOx (ppm) Temperature (K)

1A 1.37 10.1 17 288 7712A 1.53 11.06 23 310 7133A 1.4 10.9 20 295 7454A 1.78 8.39 10.9 254 8235A 1.59 9.67 13 273 7881B 1.88 7.5 13 54 6952B 1.4 10.39 29 68 7003B 1.42 11.22 27 68 7514B 2.29 6.3 7 22 7455B 1.56 9.92 17 56 773

al EnA. Sez et al. / Applied Therm4. Conclusions

Innovation and deployment of the butaneediesel dual injectionsystem demonstrates it is possible to achieve an effective trans-formation of commercial diesel oil burners, maintaining goodcombustion performance and low pollution levels. Based on theexperimental results, for equivalent operating conditions, thecombustion process of liquid butane yields a similar energy outputwith less polluting emissions than the diesel oil combustion. Also,with liquid butane ames, temperatures are better distributedthroughout the combustion chamber.

Fig. 8. Concentrations of O2 (a), CO2 (b), CO (c), NOx (d) and sgineering 45-46 (2012) 1e8 7Hence, the key factor to obtain a proper interchange fromdiesel oil-to-liquid butane in commercial burners is the adequatecontrol of liquid butanes ow rate to obtain an equivalent energyoutput.

Acknowledgements

The authors wish to acknowledge the support of LIPIGASS.A. Enterprises and CONICYT-Chile under Fondecyt project1121188.

oot (e) for both diesel oil and liquid butane combustion.

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A. Sez et al. / Applied Thermal Engineering 45-46 (2012) 1e88

Liquid butane as an alternative fuel for diesel oil burners1. Introduction2. Experimental setup and methodology2.1. Isothermal reactor and instrumentation2.2. Thermal performance calculations

3. Experimental results and discussion3.1. Flame geometries and general characteristics3.2. Thermal assessment of the combustion process3.3. Combustion performance based on flue-gas analysis

4. ConclusionsAcknowledgementsReferences