Orlando Volpato, Delphi - AEA – Associação Brasileira de ...

DIESEL-ETHANOL TECHNOLOGY
Orlando Volpato Filho e Vicente Pimenta
Delphi - Powertrain - Brazil
Abstract
World wide research on alternative fuels has been intensified due to environmental
concern and diminishing of conventional fossil fuels reserves. In Brazil, the usage of
fossil fuel for the production of sugar-cane has been improved over the years, but
there still room for improvements. In the agricultural area, for instance, It is estimated
that for 1 Ton of processed sugar-cane about 2 liters of diesel fuel is used. Over the
last year, a fleet of around 110,000 agricultural machines and trucks burned about
1.2 billion liters of diesel. Along with the opportunity of reducing the emission of green
house gases there is also an economic advantage of using ethanol because the final
fuel cost to the producer is about half the price of the diesel fuel. The reasons above
motivated us to develop a Diesel-Ethanol control for Diesel engines using a
mechanical diesel injection pumps. An add-on system was developed using an ECM
used for passenger vehicles to control engines with either 4 or 6 cylinders. In this
system, Ethanol is injected into the intake air stream and a pilot injection of diesel is
used to achieve ignition. This system was derived from a Diesel-CNG system
previously developed for urban busses. Careful design of the control algorithms is
required to prevent excessive diesel fuel usage and high hydrocarbon emissions.
This paper will describe the Diesel-Ethanol system in detail and present some
performance data.
Application
The Diesel-Ethanol technology is better applicable to retrofit of diesel engine controls
with Delphi EMS where the availability of low cost ethanol, mainly in ethanol
production plants, makes the operation economically attractive.
Goal
The goal for the Diesel-Ethanol technology is to reduce the usage of fossil based
fuels (diesel) on transportation and agricultural operations. This will reduce the
amount of emitted green house gases. On top of this there are economical gains from
the reduced cost with fuel and possible gains with Carbon Trade due to Clean
Development Model projects under the Kyoto Protocol, this gain could be further
invested on the development of clean automotive technologies.
1. Development
In the quest for diminishing its dependence on foreign petrol along with the need to
reduce emissions of green house gases to improve air quality, Brazil is pursuing the
greater use of alternative fuels.
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Diesel-Ethanol vehicles emit lower levels of toxics and ozone-forming hydrocarbons,
mainly because ethanol emits 8.5 times less CO2 than diesel for the same amount of
energy [24].
In Brazil, there is a big demand for diesel fuel. Looking at data taken form the 2008
edition of the Mines and Energy Ministry’s National Energy Accounting (BEN 2008)
[1] one can see from figures 1 and 2, that 41% of the petrol processed goes to diesel
fuel production; 75% of diesel used goes to road transportation and 16% to
agricultural use.
Considering the energy used for transportation, the vast majority goes to road
transportation 91.8%, railroad transportation accounts for 4.8% of the used energy.
Considering road transportation alone, 51.6% of the energy comes from diesel fuel
and about 19.4% comes from a renewable source (ethanol).
The strong dependence on diesel fuel leads to some interesting import/export
characteristics. Table 1, below, summarizes the import/export volumes and values for
2008.
It is said that Brazil is self-sufficient in petrol. Most of Brazilian’s petrol is of heavy
type, not suited for diesel production, in order to attend the demand for diesel fuel
light petrol and diesel fuel is imported. We have excess heavy petrol and gasoline,
which are exported.
Considering the energy equivalence, in a quick calculation, the volume of petrol and
fuels that are imported/exported the net result is near zero, indicating a self-sufficient
condition. See table 1.
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Fig. 1: Petrol derived fuels usage in Brazil

Fig. 2: Energy usage by transportation type and fuel type breakdown for road
transportation
Looking to the trade balance, thought, Brazil expends about 5.5 billion dollars
importing petrol and fuel, corresponding to about one fifth of the trade balance of
about 25 billion dollars for year 2008. See table 1.
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Table 1: Brazilian petrol trade balance
Considering the projections for future price of petrol, see figure 3, extracted from
2007 report of the US Department of Energy, there is strong evidence that the
expenditure with fuel will increase for the next two decades.

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Fig. 3: Petrol price projections scenarios
The analysis above shows that, despite the apparent self-sufficiency in petrol, it is
very important to substitute renewable fuels for diesel fuel in order to pursue a more
favorable trade balance.
In the following paragraph, some sugar and alcohol agricultural sector data will be
presented along with benefits of using ethanol to substitute part of the diesel used in
sugar-cane agricultural operations.
1.1 Sugar and alcohol agricultural sector data (2008/2009 harvest)
Compiling sugar-cane agricultural data, available from many groups like: Idea,
Cepea/Esalq, UNICA, CONABE and others, we can make the summary for the
2008/2009 harvest. See additional sources [30], [31], [32] and [33].
About 569 million tons of sugar-cane was processed by about 420 sugar and/or
ethanol mills [29][34]. See figure 4 below. There are about 35 new mills currently in
construction.
On the average, each ton of sugar cane produces about 84 liters of anhydrous
ethanol (AEAC, used to make gasoline C from its mixture with gasoline A).
On the average, each ton of sugar cane produces about 90 liters of hydrous ethanol,
which is sold at fuel as E100. There is an excess electricity of about 12 KWh per ton
of sugar cane.
Diesel fuel is used at an average rate of 2.03 liters for each processed ton of sugar
cane, amounting to approximately 1.16 billion liters of diesel per harvest.
From that amount of fuel, about 60% is used for road transportation and 40% is used
by tractors, harvester and other off-road equipments used in the farms and mills.

Fig. 4: Location of sugar-cane farms and mills
1.2 Economic motivation for diesel substitution
There are big savings when ethanol is substituted for diesel fuel in an ethanol
producing facility.
The sugar cane farm/mill buys diesel as a big consumer, paying a price smaller than
displayed at road fuel stations. But diesel fuel should be conveniently stoked and
there is a monthly bill to be paid.
On the other side, ethanol fuel is ready available at much lower costs than at the fuel
station.
See figure 5 for estimated production costs for ethanol compiled in the 2008 F.O.
Licht ethanol report.
Fig. 5: Production cost of ethanol in different countries
Diesel fuel is more energetic (per volume or weight basis) than hydrous ethanol, in
order to substitute one liter of diesel, in energy terms, one have to use about 1.67
liters of ethanol, see table 2 below [25].
Considering the buy price of diesel and the sell price of hydrous ethanol for the last
year, the fuel economy can be evaluated, see figure 6 [30].
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Page 6 of 18
Table 2: Energy comparison of diesel vs. ethanol
On a year average the price of diesel was R$1.90 and the sell price of ethanol was
R$0.66, in an energy comparison R$1.10 worth of ethanol has the same energy as
R$1.90 worth of diesel fuel.
Considering the use of 2.03 liters of diesel used to process 90 liters of ethanol, the
diesel represents about 6.5% of the sell price of ethanol; this number is bigger if one
considers the production cost.
Fig. 6: Price comparison of diesel vs. ethanol
Considering that 60% of the diesel, used to process the sugar cane, can be replaced
by ethanol a savings of about R$ 530 million can be achieved per harvest. See figure
7 below.

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Fig. 7: Considerações: 50% Diesel substituído por etanol; 100% frota
Potencial de economia/safra: R$ 530 milhões
Considering the substitution ratio of 60% the costs of fuel will be 25% lower, reducing
ethanol price by almost 2%.
1.3 Ambient motivation for diesel substitution
In Brazil, the production of ethanol is one of the most efficient in the aspect of using
fossil fuels, but there still room for improvements.
Considering the carbon cycle, the use of fossil fuels will release Green House Gases
into the atmosphere.
Renewable fuels, made from biomass, uses CO2, water and solar energy to grow
plants, such as sugar cane, these operations, however still uses fossil fuels in the
form of fertilizers, process chemicals, lubricating oils and diesel fuel. See figure 8
below.
Fig. 8: Illustration of carbon dioxide cycle

There are some studies that assess the emissions of green house gases for the
complete fuel cycle [24]; from those studies the use of 1 liter of diesel fuel emits
about 3.14 Kg of equivalent CO2 into the atmosphere. See table 3 below.
The use of 1 liter of ethanol for the propulsion of engines, emits about 0.37 Kg of
equivalent CO2, it is not zero because fossil fuels are still used in the process; like
fertilizers, agro toxics, paints, diesel, etc.
Considering energy equivalence the substitution of ethanol for diesel avoids the
emission of 2.52 Kg of equivalent CO2 per liter.
Table 3: CO2 cycle for diesel vs. ethanol
Using a substitution ratio of 60% to all diesel-burning engines avoids the emission of
about 1.7 million tons of CO2 into atmosphere, per harvest season. See figure 9
below.
Fig. 9: Considerações: 50% Diesel substituído por etanol; 100% frota
Potencial de evitação de CO2: 1.7 milhões de Toneladas
A fringe benefit of this is that CDM (clean development models) can be made and
negotiated in the terms of the Kyoto protocol in order to finance the development of
technologies to further reduce the use of fossil fuels.
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Each ton of equivalent CO2 is being negotiated by about EU$14.60 at the Emissions
Trade Stock [35]; not all this value can be made using CDMs but considering that
each ton of CO2 in a CDM project is worth US$5.00 about US$8.5 million can be
made available.
In the following paragraphs, the basics of diesel engines are presented, along with
the description of a concept of a diesel-ethanol system.
Dynamometer data, for both original diesel engine and the diesel-ethanol operated
engine, is presented. After that, improvements in the presented diesel-ethanol system
are suggested.
2. The Original Diesel System
The diesel engine is a compression ignited internal combustion engine. In this
engine, the air is compressed and the fuel is injected directly into the cylinder. The air
temperature has increased due to the compression and the fuel rapidly ignites
causing increasing pressure within the cylinder and therefore, the generation of work.
The diesel engine has some interesting features: there is no “metering” of the intake
air, which results in minimal pumping losses. As fuel is injected into the air at
temperatures higher than the diesel fuel auto-ignition temperature, it burns almost
completely, even in very lean mixtures.
The diesel fuel is injected at high pressures with the aid of a metering fuel pump that
delivers fuel at very high pressures in the right quantity.
The mechanical diesel pump, which has been used in most of the diesel engines in
the field, has many internal mechanisms to deliver the fuel to make the desired
torque characteristic while avoiding emission soot and pollutant gases per the current
legislation.
A diagram of the diesel pump we used for this development is shown in figure 10
below.
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Page 10 of 18
Fig. 10: Mechanical Diesel fuel pump diagram
The mechanical diesel fuel pump used in most of the agricultural vehicles has a
control that is of the type “variable speed governor”.
In this type of diesel pump, the accelerator lever does not control the fuel delivered
directly (control lever in the diagram above) but at the set point of the variable speed
governor, see figure 11 below.
Fig. 11: Variable speed flywheel governor
Considering this setup, the torque characteristic of an agricultural tractor engine
(Valtra BH185i) can be seen below for various accelerator lever positions. See figure
12.
Fig. 12: Torque characteristic vs. accelerator position
2.1 Diesel-Ethanol Combustion
Diesel-ethanol engines use pilot diesel fuel for ignition with most of the power coming
from burning ethanol. The combustion process changes when the engine transitions
from using diesel fuel to using the combination of diesel fuel and ethanol.

The ethanol is injected into the inlet air and mixed with air. As diesel fuel enters the
combustion chamber due to the pilot injection; it is ignited by the hot air after a very
short delay, creating many ignition fronts to burn the natural gas mixed with air.
In figure 13 a photograph of a diesel fuel injection being ignited by the hot air is
shown to illustrate the pilot injection concept. The injector in the example has 6 holes.
The diesel-ethanol engine is possible because the auto-ignition temperature of
ethanol is higher than the temperatures at the end of compression cycle [37].
A diagram with the temperature in the air inside the cylinder in function of crankshaft
angle is presented in figure 14. The temperature was calculated using the expression
Tc = To * r (n-1), where r is the compression rate (r = 16.8) and n is the polytrophic
exponent for real gases (n = 1.35) [26].
The line with 130 degC intake temperature indicates the limit of operation without
auto-ignition issues.
For a compression ignition engine, using a mechanical diesel fuel injection system,
where the fuel is injected in one event, there are two combustion phases, as
exemplified in figure 15.
The injected fuel does not burn instantaneously, it takes a time to vaporize the fuel
and to chemical reactions to take place and release energy into the combustion
chamber.
Fig. 13: Internal view of cylinder after some milliseconds of diesel fuel injection
This term is called “ignition delay” and after that time most of the fuel already injected
burns in a short period. This is termed “pre-mixed combustion phase”.
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As the ethanol enters the combustion chamber mixed in the air, most of ethanol
burns in a “pre-mixed” fashion too.
In case of high torque levels, where fuel keeps being injected in a “slow” way the rate
of heat release is slow, as the “ignition delay” is very small at high temperatures.
This is called “diffusion combustion phase”. [26]
Fig. 14: Approximate cylinder gas temperature rise with compression with annotated
auto-ignition for diesel and ethanol
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Fig. 15: Pre-mixed vs. diffusion controlled combustion
One issue with high levels of diesel substitution is that most of energy come from
ethanol and is released in a fast way, causing high pressures that might stress the
engine.
2.2 Diesel-Ethanol System
This system was built using a standard ECM suited for spark ignition engines of
passenger vehicles.
Due to the limited number of sensors and actuators and almost inexistent vehicle
interface this system can be implemented using a small motorcycle ECM.
It was conceived to be an add-on system to a diesel engine using a rotary
mechanical pump.

One of the advantages of a diesel-ethanol engine, over an engine converted to
ethanol only operation (i.e. using Otto cycle) is that the engine can run in a diesel fuel
only mode, if desired.
In figure 16 is depicted how the engine control module and the associated sensors
and actuators are connected in the diesel-ethanol system.
Fig. 16: Agricultural tractor diesel-ethanol control system
In the original diesel engine, a pedal connected to the control lever via a cable
controls the amount of fuel delivered. A conventional throttle position sensor is
mounted on the control lever to inform the ECM of the diesel fuel pump position; this
will enable the modeling of the diesel fuel delivered. See figure 17.
Fig. 17: Accelerator pedal sensor mounting
Besides the electronic control module, minimal components were added for the
correct working of the system. Those include a 58X crank wheel (an engine timing
wheel with 60 teeth geometry and 2 missing teeth to enable engine synchronization),
crank sensor, accelerator pedal position sensor, ethanol injectors, engine
temperature sensor, ethanol fuel tank, fuel pump and fuel pressure regulator.
Additional, vehicle related components, are also used, like: Diesel-Only Switch,
indication light and a diagnostic connector.
The indication light is on when the engine is working in diesel-ethanol mode; it might
also indicate failures, e.g. continuous blinking or be part of a field programming of
engine characteristics.
In case of failures, a malfunction code can be send using a blink code as used many
years ago for the passenger vehicles.
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The ethanol substitution may vary from 60% to 85% at full load. The dynamic
transition from diesel fuel to gas is handled with special engine control algorithms and
various settings and adjustments to ensure the dual fuel engine drivability is similar to
diesel fuel.
The natural gas is fed to the injectors at a pressure of 2.5 bar above the pressure in
the intake manifold. Ina compressed natural gas cylinder the pressure is about 200
bar, so a natural gas pressure regulator is used.
2.3 Experimental Data
A diesel-ethanol system was installed on a Valtra BH185i tractor with an AGCO 620
DS engine with a Delphi DPA rotary diesel pump.
Using the original injection timing, the maximum substitution ratio of ethanol was
evaluated at full load conditions. See figure 18 below.
Considering the maximum torque at a given engine speed, the engine was set in way
that the diesel only torque was reduced while increasing the torque from ethanol fuel,
up to the amount without power loss of misfire.
At higher engine speeds the ratio of substitution was smaller; we will talk about that
later.
Fig. 18: Minimum diesel pilot for original diesel pump
Typically an agricultural engine is used at engine speeds around 1800 min-1 at 80-
90% of full load.
So, it’s important to devise a system that has good substitution ratios at that engine
speeds.
The substitution ratio is very sensitive to the injection timing. The engines were
experimented with an advance of +1 degCA, +2.5 degCA and -2.5 degCA regarding
the original injection timing. See figure 19 below.
Increasing the advance angle yields higher substitutions ratios, but the engine is
more prone to misfire.
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With 2.5 degCA more advanced system the substitution ratio is high but the torque
can not be kept high after some time.
Fig. 19: Minimum diesel pilot for injection angle advanced by 1, 2.5 degree and
retarded by 2.5 degree
Experimenting with the injection timing retarded by 2.5 degCA showed lower
substitution ratios.
The operational costs, in terms of fuel consumption, at full load, are estimated
considering the substitution ratios achieved for the injection timing at the original
position. Using the more advanced injection timing the savings will be higher. See
figure 20.
This estimate also takes into account the sell price of the ethanol by the ethanol
producer; it is not considering actual production costs, which will be smaller.
Fig. 20: Comparison of operational costs diesel vs. diesel-ethanol system at
maximum load condition.
Conclusions
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The reduction of foreign petrol dependence and emissions of toxic and greenhouse
gases will gradually be realized by an increase in the use of alternative fuels in
agricultural operations, especially those of ethanol producing mills.
The use of ethanol in agricultural tractors is an economically feasible way to reduce
diesel usage, whence costs and emission of green-house gases.
Automakers and system-solution-providers work together to use alternative fuels
without increasing system costs.
An efficient and cost effective solution has been developed for the use of ethanol with
engines originally fitted with a variable speed diesel mechanical pump.
It was demonstrated that the same level of torque and power is achievable running
with fair levels of substitution of diesel fuel by ethanol.
The fuel economy achieved with the Valtra BH185i tractor was around 30%, with
good correlation with the predicted values. It should be noted, however, that the
effectiveness of the diesel-ethanol system is highly dependant in the way the tractor
is driven.
There are still a number of improvements to be done in this system to increase the
usage of ethanol.
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