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HEFAT20118 th International Conference on Heat Transfer, Fluid
Mechanics and Thermodynamics
11 13 July 2011Pointe Aux Piments, Mauritius
EXPERIMENTAL EVALUATION OF GAS TURBINE EMISSIONS FUELED
WITHBIODIESEL AND BIODIESEL-DIESEL BLEND
Ferreira R.W.M.*, Guerra D.R.S., Nogueira M.F.M. and Lacava
P.T.***Author for correspondence
Department of Mechanical Engineering,Federal University of
Par,
Belm, Par, CEP 66075-110, Brazil.**Department of Propulsion,
Aeronautical Institute of Technology,So Jos dos Campos, So
Paulo, CEP 12228-900, Brazil.
E-mail:[email protected]
ABSTRACT
Over the past years many researchers have been carryingout
studies regarding the use of renewable fuels for internalcombustion
engines due the environmental and economicaspects. These studies
have been conducted mainly applyingbiodiesel from vegetable oil or
animal sources in compressionengines. On the other hand, biodiesel
can also be used as fuelfor gas turbine despite scarce amount of
work exists on theliterature about this theme. This work reports
results of a microgas turbine running on biodiesel from vegetable
source, blendsof biodiesel-diesel (B50, B70 and B100) and compare
such
results with natural gas as fuel. The micro gas turbine
wasoriginally designed to operate with natural gas.
INTRODUCTION
Several researchers have been studied renewable fuels
forinternal combustion engines; however it is important toremember
that alternative fuels can and should be tested inother thermal
machines. Currently, several countries includingBrazil follow a new
trend in the energy sector, the developmentof distributed
generation with emphasis on small-scaleproduction. Among the
various technologies that can be used indistributed generation and
in small-scale, micro-gas turbineshave become an excellent
technology option. Micro-turbinesare small thermal machines
operating in the Brayton cycle toproduce electricity in the range
of 20 to 500 kW.
Diesel engines have several applications as on
electricalproduction, industrial and agricultural activities, at
transports of passengers. In all these areas petroleum fuels have
been used incombustion engines. Although the undeniable
dieselimportance as fuel its application in the combustion
processcauses environmental problems.
Pollutants from diesel fuel combustion include carbonmonoxide,
CO, carbon dioxide, CO2, oxides of nitrogen, NOx,
sulphur dioxides, SOx and particulate matter. In this pview a
variable investigation on fundamental combcharacteristics and
emissions of a heat engine using diehave been conducted [1-4].
In this scenario is that the world is concerned toalternative
fuels that can be used in power machines, a gattention has been
paid to biomass fuels as renewable resources. Many types of biomass
used for biodiesel prodinclude rapeseed, cottonseed, sunflower,
jatropha and palPalm oil is one of the most promising alternative
fuels tofossil fuels [7].
Another goal of the alternative fuels application aviation
sector [9, 10]. The effect of the aviation fuepetroleum-based on
the environment is significant dincreased air traffic. At this
sector the considered enginthe gas turbines to operate fuelled with
biofuels. Besidbiodiesel application in automotive sector and
hprocesses, the use of them in aircraft and land-baseturbines would
benefit the economy and environment.
NOMENCLATURE
ANP [-] National Petroleum Agency ASTM [-] American Society for
Testing and Materials BDXX [-] Biodiesel percentage indicator in
the blend
Comb1 [-] New fuelGD [-] Distributed GenerationGNV [-]
Compressed natural gas HHV [kJ/kg] High heating valuem [kg/s] Mass
flow
SMD [m] Sauter mean diameter P [Pa] pressureT [C]
temperature
A lot of biomass type has been used as fuel. A theoexperimental
study of a biodiesel from vegetable oil hav
8th International Conference on Heat Transfer, Fluid Mechanics
and Thermodynamics
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carried out [1-10]. The analysis of heat transfer rate in
variousconditions along the furnace and the performance of
biodieselgenerally are compared with diesel oil. The results showed
thatdiesel oil has a higher heat transfer rate in most parts
exposedto flame. In these researches some authors detected that
thecombustion products have less dark coloration than theproducts
generated by diesel oil, it was also verified that theburner was
not presented problems with its operation afterreplacing diesel
fuel by biodiesel.
Investigations on the use of biodiesel and its blends withdirect
injection diesel engine were realized in the last five years[1-2].
The production of biodiesel from inedible animal fat bythe
transesterification process and its use in diesel engines,were
studied. The chemical properties investigation of fuel,density and
viscosity were obtained according to ASTM D6751and EN 14214. The
biodiesel viscosity and density were foundclose to the value of
diesel, the result of the analysis of thecalorific value showed to
be slightly lower compared to diesel.Addition of biodiesel to
diesel promotes a decrease of theengine efficiency and an increase
of the specific consumptiondue to the low calorific value of the
biodiesel compared todiesel. Emissions of carbon monoxide (CO),
nitrogen oxide(NOx), sulfur dioxide (SO2) and soot were reduced by
about15%, 38.5%, 72.7% and 56.8 % respectively.
Research conducted in micro turbines started very recently.A
study by Nascimento [6] about performance and emissions ina diesel
micro turbine of 30 kW using biodiesel blends as fuelshowed that
the use of biodiesel promotes a slight increase of CO, low NOx
emissions and no emission of SO2. Adevelopment on optimization of a
gas turbine emissionsoperating with biodiesel [5] including
atomization,vaporization, combustion and emissions of biodiesel
wasrealized and compare with the distillated diesel (DF2). In
thisthe turbine used was a commercial gas turbine Capstone
(C30)30KW known as a micro turbine generator.
The analysis of the vaporization and atomizationcharacteristics
suggested that even improving the fuel injectionsystem to reduce
the levels of NOx emissions it does not reduceemissions below the
level of DF2, therefore, another factormust be associated to this
reduction which means that would berequired further studies related
to kinetic chemical mechanismsto provide better understanding of
this case. An investigationabout the atomization characteristics of
diesel and palm methylester (PME), shown that there was no
significant differencebetween the flow rate of the fuels [7].
Relation to the averagesize of drop (SMD), PME has fewer tendencies
to formation of bright flame and soot than diesel and that for the
same SMDand kinematic viscosity the NOx emissions from PME is
lower
than Diesel. The combustion processes are affected by
thecharacteristics of the type of fuel, fuel atomization and
injection[11].
The actual study presents an experimental investigation
fordetermining the emissions generated by biodiesel and
biodiesel-diesel mixtures. Initially the micro turbine that was
designed tooperate with natural gas, so the results was compared
with thisfuel. In the experimental tests the natural gas was change
bybiodiesel fuel blends in addition of natural gas. The
obtained
results of the tests include the exit emissions and
exhtemperature.
FUEL PROPERTIES
As the main focus of this study is to evaluate the emfrom a
micro turbine operating with an alternative fudetermination of some
fuel characteristics is importandevelopment of flexible systems or
the adaptation of th
operate with different fuels requires a careful theoanalysis,
since there are many variables to consider sstoichiometry,
dilution, temperature and pressure characteof combustion in gas
turbines. In the following topicscharacteristics of the fuels that
were used for this stupresented.
Natural gasNatural gas is a fossil fuel formed by a mixtu
hydrocarbons of low molecular weight, its main compomethane CH4,
on the composition there are also propanebutane C4H10, pentane
C5H12, hexane C6H14, isoiC4H10. There are minority fractions of
carbon dioxidehydrogen sulfide H2S, water, nitrogen and mercaptans.
calorific value can vary between 8,000 to 10,000 kdepending on the
levels of heavy (ethane and propaninert gases (nitrogen and carbon
dioxide).
In Brazil the composition of natural gas for the commpurpose is
determined of the act number 104, July 8, 2the National Agency of
Petroleum, Natural Gas and Bi(ANP). For the experiment it was
consider the composinatural gas defined by the same act 104/2002.
The minlimits of methane, ethane, propane and butane that is
usesoutheast Brazilian region was adopted. The composishown in the
Table 1.
Table 1 Natural gas composition
NATURAL GAS COMPOSITIONCH4 86% VOLC2H6 10% VOLC3H8 03% VOL
DieselA fossil fuel from distillated petroleum that has va
concentrations of sulfur, nitrogen and metal compoundmain
constituents of diesel are carbon chains from 6atoms. Diesel fuel
is composed of paraffinic, olefiniaromatics formulated by mixing
various distillations asfuel, heavy naphtha, light and heavy diesel
from variousof processing the crude oil.
The components proportions in diesel fuel are thosallow the
finished product fit within the specifications the ANP agency. The
diesel fuel used in the tests is thefuel sold to consumers and
follows the specifications accto standard ANP 15 OF 03.19.2006.
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BiodieselBiodiesel can be produced from various raw materials
such
as vegetable oils, animal fats, waste oils and residual fats
fromvarious processes. It can also be used pure or mixture
withpetroleum diesel in various proportions. In recent
yearstechnological developments shows trends for adoption
thetransesterification as the final process (ASTM - D6751).
Thebiodiesel definition according to ANP agency is a fuelcomposed
of alquilsteres and long-chain fatty acids derivedfrom vegetable
oils or animal fats.
Mixtures (compositions) of biodiesel and conventionaldiesel fuel
are the most commonly products distributed for usein the retail
diesel fuel. The system known as Factor B isfrequently used to
indicate the amount of biodiesel in any fuelmixture:
Biodiesel 100% referred to as B100, whileBiodiesel 20% labeled
as B20Biodiesel 5% labeled as B5Biodiesel 2% labeled as B2
Following in Table 2 there are some specificationsprovided by
Agropalma about Palmdiesel (PME). Agropalmaindustry provided the
palm oil for development this work.
Table 2 Palm oil specificationPalmdiesel ASTM
Glycerol (%) 0,01 0,02 max.Total glycerides (%) 0,08 0,24
max.Residual carbon (%) 0,04 0,05 max.Density (g/cm3) 0,843 0,82 -
0,87Viscosity 40C(mm2/s) 3,98
1,9 - 6
Flash point (C) 135 100Copper strip corrosion 1 3Water (%) 0,03
0,05 max.Ash (%) 0,015 0,02Acidity (%) 0,03 0,04
ATOMIZING CHARACTERISTICS
The atomizer was designed to use natural gas with liquidfuel
(diesel or biodiesel) as shown in Figure 1. The
atomizationcharacteristics as SMD and cone angle of the spray
wereinvestigated. Figure 1 shows the experimental
apparatusschematic. The fuel is pressurized by the supply of N2 gas
inthe fuel tank. The fuel is measured using a meter-typeflowmeter
from Omel manufacturer model number 4Q factorycalibrated for a flow
rate from 0 to 14 g/s, for a liquid withdensity 850 kg/m3 located
in the fuel line before the injector.
The average size of droplets was measured by a lasersystem
(Malvern MasterizerX) in which traverses the spray bya laser beam,
initially parallel spreads through photodiodedetectors located on a
circular plate, collects the scattered lightangular sectors
individuals. To analyse the droplet size
distribution, the formulation used by the system iFraunhofer
theory, which states that a parallel beammonochromatic light passes
through a cloud dropletspattern obtained is a series of concentric
light and darkwhose spacing between them will depend on the
distributhe droplets. Each detector scans in the order of
2msmeasure consists of 2,000 scans.
Figura 1 Experimental apparatus of the atomizer system
EXPERIMENTAL APPARATUS FOR COMBUSTIONEXPERIMENT
Figure 2 and Figure 3 show the experimental apparawell as the
squematic used in testing the micro turbindata acquisition and
control system of micro turbicomprised of supervisory software
developed at RSV
platform from Rockwell manufacturer in which it is conto a
programmable logic control (PLC) model Micro1100. This system
receives signals from the transdsensors, actuators and
controls.
.
Figure 2 Micro turbine
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Temperatures are measured using a thermocouple type Kand one
thermocouple T at each position. The operating rangeof the
thermocouple type K is 0 to 350C with an error of 1Cand the T-type
thermocouple is 0 to 1250C with an error of 2.2C. The thermocouples
are connected to an analog moduleRockwell where the signals are
sent to the PLC MicroLogix1100.
The pressure measurements at each point shown in figure2, was
performed using a pressure sensor at each position. Thesensor has a
measuring range from 0 to 6 bar with an error of 1%. The rotation
of the micro turbine is measured by aninductive-type Hall sensor.
The counting of pulses is sent fromthe Hall sensor to a pulse
counter Phoenix Contact MCR-f-UI-DC, visualization and control of
rotation is made by thesupervisory system.
The flow rate of natural gas is measured by an orifice
plate,along with software that receives pressure data through
apressure transducer and solves the calculations based onspecific
data set obtained from the orifice plate, accounting theflow rate.
To account the flow rate of liquid fuel (Diesel,Biodiesel and
mixtures) a flowmeter manufactured by Omel,model number 4Q factory
calibrated for a flow rate from 0 to14 g/s for a liquid with
density 850 kg/m3, was used. The flowmeter was recalibrated for
each fuel in advance before the tests.The emissions data of CO2,
NOx, CO, and O2 were collectedusing a gas analyzer 8000 and the
Greenline programDBGas2000.
The gas analyzer consists of a main unit (MCU, MainControl Unit)
and a remote unit (RCU, Remote Control Unit).The gas is collected
in the exhaust of the micro turbine througha tube and sent to the
MCU. All the data analysis is done on theMCU. The control unit can
be configured and controlledremotely through the RCU cable or
Bluetooth communication.
A squematic draw in Figure 3 is the experimental apparatusused
in this study. At this the air that is sucked from theatmosphere
and compressed in the compressor, when it reachesthe combustion
chamber the combustion processes begins withthe fuel which in turn
reaches the atomizer through two fuellines, one that provides
natural gas and another that is sent toliquid fuel. With a spark
the combustion is initiated, hence thereactions on combustion
chamber produces hot gases thatexpand through the turbine providing
shaft work or propulsion.
Figure 3 Experimental apparatus system
RESULTS AND DISCUSSION
Figure 4 shows the experimental results measuredSMD, each
experimental value presented in figure is thevalue of 25 samples,
with a satisfactory repeatability prea maximum standard deviation
of about 0.96% to pressure. The increased pressure difference is
expectebeneficial to the SMD. It causes the liquid discharge
fratomizer nozzle at high speed, providing a thinner however
according to the literature the droplet size preby the atomizer is
in the range of droplets greater thamicrometers. So, it has a
greater vaporization time, incrthe mixing length and the combustion
region.
Figure 4 Average size of droplet.
The cone angle increases with pressure, this is expected since
with increasing pressure and henctangential velocity, there is a
tendency for the jet to be tover the sides increasing the angle. In
Figure 5 the conseof not developing the spray at low pressures is
observeincrease in cone angle of the spray when the pressure
inccannot be noted for the atomizer, this is due to the
geomcharacteristics of the injector.
Figure 5 Atomizer system
Analysis of emissions and gas temperature of exhausrotation of
45,000 rpm. CO2 Emissions: Figure 7 compares
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7injector pressure
differential (atm)
60
80
100
120
140
160
180
200
220
240
S M D ( m )
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emissions of NG, Diesel, Biodiesel and blends, for all blendswas
an increase in emissions compared to NG from 17.76% forBDD50,
66.44% for BDD70, 69.97% for BDD100, and 76.97%for diesel oil.
CO emissions: figure 6 shows the comparison of CO forthe fuels
NG, Diesel, Biodiesel and blends; for all blends wasan increase in
emissions compared to NG from 2.53% forBDD50, 2.57% for BDD70,
2.69% for BDD100, and 1.79% fordiesel oil.
NOx emissions, Figure 8: can be observed that there wasan
increase of 12.5% in emissions compared to NG for DieselBDD100. For
BDD50 and BDD70 remained the same levels of emissions when compared
to NG.
Gas temperature: it was observed, in Figure 9, that for
allblends has an increase in temperature when compared to NG.This
increase was of 39.40% for BDD50, 60.24% for theBDD70, 72.20% for
BDD100, and 69.14% for diesel oil.
(a)Figure 6 CO Emissions
(b)Figure 7 CO2 Emissions
(c)Figure 8 NOx Emissions
Figure 9 Exhaust temperatures.
CONCLUSION
Analyzing the results presented by the atomizer, comwith the
work of Hashimoto [7], for the SMD-type atomlow pressure swirl SMD
is presented in the range of 80micrometers. So the atomizer used in
this work pres
medium size drop much larger than that found in the liteand cone
angles were slightly lower for the same variapressure.
The emission results are primarily influenced bequivalence ratio
in the primary zone, the average sdroplet and the geometry of the
combustion chamber. Sincombustion chamber is designed to operate
with naturahas reduced geometries and thus impacting on the
reemissions for the combustion of liquid fuels like
DiesBiodiesel.
0 3 6 9 12 1 5 18 21 24 27 30 33 36 3 9 42
Time (minutes)
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
C O ( p p m )
45.000 RPMBDD50BDD70BDD100Diesel
GNV
0 3 6 9 12 15 18 21 24 27 30 33 36 39 42
Time (minutes)
0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
2.7
3
3.3
3.6
3.9
4.2
4.5
4.8
C O 2 ( % )
45.000 RPMBDD50BDD70BDD100GNVDIESEL
0 3 6 9 12 15 18 21 24 27 30 33 3 6 39 4 2
Time (minutes)
0
2
4
6
8
10
12
14
16
18
20
N O
x ( p p m )
45.000 RPMBDD50BDD70BDD100GNVDIESEL
0 3 6 9 12 1 5 18 2 1 24 27 30 3 3 36 39 42
Time (minutes)
400
500
600
700
800
900
1000
1100
1200
T g s ( C )
45.000 RPMBDD50BDD70BDD100GNVDIESEL
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Based on this statement we can conclude that for therotation of
45,000 rpm the diesel oil had lower rates of CO andCO2, while the
BDD100 showed lower levels of NOx andtemperature of gases. For
rotation of 60,000 rpm, diesel hadlower rates of CO and CO2, while
the BDD50 showed lowerlevels of NOx and temperature of gases.
However to obtain more conclusive results we shouldsubsequently
improve the atomizer, and modify the geometryof the combustion
chamber in order to obtain similarcombustion conditions for all
fuels and operating conditionspre-established.
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