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Nowadays computer simulation is an important tool to support new internal combustion engine projects, but still further studies are necessary for its use in fuel development. In order to study the influence of fuel properties on engine combustion and emission performance, a computer model was designed based on a Flex-Fuel engine geometric data. Model was validated with experimental tests done on an engine dynamometer. A simulation software was used to simulate the experimental conditions, by using Wiebe two zone combustion and Woschni heat transfer models. In-cylinder maximum pressure, IMEP and emission data were calculated for different gasoline-hydrous ethanol blends at 3875 rpm, 60 Nm and 105 Nm. Total hydrocarbons concentration was simulated comparing the experimental data of hydrocarbons added with unburned ethanol emission measured with a FTIR analyzer.

In the 80's, due to the oil crisis, natural gas (NG) began to be regarded as a fuel with great potential for replacing diesel in heavy duty vehicles. At that time, Petrobras, together with other companies, developed conversion kit technology for heavy duty diesel engines to run burning simultaneously diesel and NG, known as diesel gas. For several reasons, the trials were interrupted. In the late 90's and beginning of the 2000's, factors such as NG availability, expansion of NG distribution network; increase of NG converted light duty vehicle fleet, government interest in increasing NG's energy matrix share, all together made a scenario which stimulated new developments in diesel gas technology. The scenario changed in the last couple of years, with Brazilian NG demand reaching its offering, mainly due to thermoelectricity generation guarantee of supply. This makes the diesel gas technology more attractable than the NG dedicated technologies.

In Brazilian market, Flex-Fuel vehicles represented over 85% of new light-duty vehicles sold in 2010. These vehicles can use gasoline blended with anhydrous ethanol (18 to 25% v/v), 100% of hydrous ethanol (contains from 6,2 to 7,4% w/w of water) or any blend of these fuels. Some studies regarding Flex-Fuel technology are being made in Brazil, but there are not many published information about fuel properties of different ethanol-gasoline blends. Also, it is important to better understand emissions of aldehydes, unburned ethanol and total hydrocarbons of different ethanol blends on gasoline. A Flex-Fuel engine, 1.4 l, 4 cylinders was tested on a dynamometer. A FTIR (Fourier Transform Infrared analyzer) bench measured aldehydes, unburned ethanol and total hydrocarbons. It was used Gasoline with 25% of anhydrous ethanol was used as a reference fuel (E25). E25 was blended with different hydrous ethanol contents such as 30% (H30), 50% (H50), 80% (H80) and 100% (H100).

To attend the new tendencies of the automotive market, new technologies must be used throughout the engine conception. One way of improving the project is to use computational numerical simulation, predicting engine behavior in a wide range of situations. This paper presents a methodology to estimate the engine characteristic parameters necessary to numerical simulation. Morse test was used to determine friction power, mean effective pressure friction and friction torque, considering the engine behavior during cylinder ignition cut-off. In this test all the results were compatible with manufacturer data, which validates the methodology. To define the moment of inertia, it's also proposed a fuel cut methodology, associated with the Morse test, because the torque values measured by dynamometer after the fuel cut did not correspond to the real value. Thus, plausible values of engine moment of inertia, very close to values obtained by software, were obtained.

In Brazilian market, Flex-Fuel vehicles represented over 90% of new light-duty vehicles sold in 2009. These vehicles can use gasoline blended with anhydrous ethanol (20 to 25% v/v), 100% of hydrous ethanol (contains from 6,2 to 7,4% w/w of water) or any blend of these fuels. An experimental investigation was done to study fuel consumption, emissions and in-cylinder pressure data of a Flex-Fuel Otto engine, 1.4 L, 4 cylinders. It used gasoline with 22% of anhydrous ethanol as a reference fuel (E22). E22 was blended with different hydrous ethanol contents such as 50% (H50) and 80% (H80), also a 100% hydrous ethanol H100) was used. The main fuel properties were analyzed as part of this work. To control the engine operation, a programmable ECU (Engine Control Unit) was used, allowing spark timing calibration either for maximum break torque (MBT) or to keep the engine below the knocking limit.

The automotive industry usually adopts the crankshaft angle between 8° and 10° after piston top dead center for the CA50 (crank angle of 50% of mass fraction burned) in order to set the maximum break torque spark timing calibration in Otto cycle engines. There are few studies of the influence of fuel composition, such as the ethanol content, on the CA50 at the maximum torque operating condition. The subject is relevant to the extent that the fuels used in the Brazilian domestic market are different from those usually adopted abroad. The Brazilian gasoline must contain, by law, a volumetric percentage between 18% and 27% of anhydrous ethanol in its composition and, currently, this level is set at 27%. The introduction of flex fuel vehicles in the domestic market in 2003, which now represent most of the new vehicles production in the Country, allowed the use of any blend of national gasoline and hydrous ethanol. This significantly expanded the range of fuel properties variation.

Combustion images are not simple to be obtained in conventional engines. Therefore, some experimental apparatus, such as a rapid compression machine (RCM), are useful to conduct this kind of study. Imaging techniques allow flame front propagation analysis, which is a very important parameter to understand engine performance, using different fuels and also to generate data to improve fuel modeling in engine simulation softwares. A RCM was adapted to operate in a spark ignition engine mode. It was used to obtain cylinder pressure measurements of gasoline-ethanol combustion synchronized with high-speed photos of flame propagation. Contour plots of the flame front profiles, assumed to be spherical, were used in successive frames to calculate the propagation speeds toward the cylinder walls. So, it was possible to correlate images, pressure curves and flame speeds of gasoline-ethanol blends.

Regarding fuels research and development, some preliminary studies - low cost and short time - can be conducted before the traditional engine tests - more expensive and time consuming. Therefore, experimental apparatus, such as a rapid compression machine (RCM) and specific methodologies, such as imaging techniques, are very useful in order to simulate engine combustion with simplicity, agility and flexibility, reducing development time and costs. Imaging techniques allow flame front propagation and ignition delay analysis, which are important parameters to understand fuel performance in engines and also to improve fuel modeling in engine simulation softwares. A RCM was adapted to operate in a spark ignition engine mode. It was used to obtain high-speed photos of flame propagation and ignition delay. Contour plots of the flame front profiles were obtained in successive frames to analyze the flame development with gasoline-ethanol blends.

Over the last few years, a growth of the Brazilian light duty vehicle fleet converted to Natural Gas (NG) has been observed. This is mainly due to license tax reductions on NG vehicles; the increase of the NG distribution around the country and attractive price difference between NG and other fuels. The Brazilian CNG (Compressed Natural Gas) light-duty vehicle fleet has currently reached more than 1,4 million units, being the 2nd largest in the World. ANP (Brazilian National Petroleum Agency) published in 2002 Resolution no104, which defines the NG specification for automotive application. The IBAMA (Brazilian Institute for Environment and Natural Renewable Resources) published in 2002 Resolution no 291, which defines ways for the environmental certification of the NG conversion kits.

Brazil is known for its long experience on using alternative fuels, mainly ethanol for light duty vehicles. In 2002, it was released the Flexible fuel car that can run with gasohol (gasoline with 22% of ethanol), hydrated ethanol or any blend of these fuels. By the end of 2006, national production of these vehicles represented around 80% of the total. Brazil is also the second world fleet of Natural Gas Vehicles (NGV), with more than 1,4 million light duty converted vehicles. This paper describes the development of a computational thermodynamic model of compression, combustion and expansion processes of gasohol, ethanol and Natural Gas (NG) for the cylinder pressure curve prediction of a Flexible Fuel engine, working with a NG kit installed. The combustion process is modeled using a Wiebe function, which establishes the mass fraction of burned fuel. Convective heat transfer to cylinder walls is estimated with an empirical correlation for heat transfer coefficient determination.

An experimental investigation was performed on an engine dynamometer to study in cylinder pressure curve and combustion parameters variability with ethanol addition. It was used a Flex-Fuel engine, 1.4 L, 4 cylinders, with a programmable engine control unit to optimize the calibration for different blends of Brazilian gasoline and hydrous ethanol. Engine was calibrated for maximum break torque limited by knocking. In-cylinder pressure was measured by using a pressure sensor installed on the spark plug and analyzed by a combustion data system. Combustion duration, mass fraction burned, indicated mean effective pressure (IMEP) and others were calculated based on in-cylinder pressure curve data. The combustion variability was analyzed from 300 recorded engine cycle for each operating condition. Results for some operating conditions indicated that ethanol addition can reduce combustion variability on a non linear pattern.

Commercial gasoline is composed of hundreds of hydrocarbon components. Surrogate fuels that decrease the chemical and physical complexity of gasoline are being used to allow a better understanding of the processes involved in the interaction between fuels and internal combustion engines (ICEs). Based on previous published works about methodologies for fuel development using surrogate fuels, the aim of this paper is to present further results on the effect of individual components and fuel fractions on the combustion and performance parameters of spark ignition engines. SI engine dynamometer tests were conducted using ten mixtures of iso-octane, toluene, n-heptane and ethanol. Response surface models were statistically developed to analyze the interactions between fuel components, fuel properties and engine performance.

The worldwide concerns and some countries stricter legislations regarding the CO2 emission of light duty vehicles are motivating new technologies adoption, such as hybrids and electric battery vehicles, and discussions about what fuel economy data comparison between different countries. International discussions were done about the need to reevaluate the existing standardized driving cycles due to large emission and fuel economy differences when compared to the real road values, leading to the creation of a new cycle called WLTC (Worldwide Harmonized Light Duty Vehicle Test Cycle). Light duty vehicle fuel economy tests are usually performed on a chassis dynamometer using standard driving cycles under controlled laboratory conditions. Each country regulation defines the standard cycles used for the fuel economy tests.

Fossil fuels and biofuels usage in internal combustion engines are the main source for vehicular propulsion. This justifies the intense worldwide research and development to comply with the challenges of increasing efficiency and emissions reduction. The modeling of commercial fuels and engine combustion processes presents great challenges. There is also the need to better understand how different fuel components interact and influence engine combustion and performance parameters. In previous works, components selection and engine dynamometer tests were done to identify representative surrogate fuels for commercial Brazilian gasoline. It was concluded that formulations with n-heptane, iso-octane, toluene and ethanol can be used to model oxygenated gasolines. Methodologies were implemented to evaluate the influence of the fuel components on fuel properties and several engine combustion and performance parameters.

Gasoline is a complex mixture that possesses a quasi-continuous spectrum of hydrocarbon constituents. Surrogate fuels that decrease the chemical and/or physical complexity of gasoline can be used to enhance the understanding of fundamental processes involved in the interaction between fuels and internal combustion engines (ICEs). The aim of this paper is to present methodologies for fuel development and show how surrogate fuels can be used to investigate the effect of individual components and fuel fractions on fuel properties and the performance of commercial engines. For this purpose, experiments were designed and SI engine dynamometer tests were conducted using ten mixtures of iso-octane, toluene, n-heptane and ethanol. Response surface models were statistically developed to analyze the interactions between fuel components, fuel properties and engine performance.

The increasing ethanol participation in Brazilian fuel market and its supply and price oscillations, motivate studies on multifuel engines behavior with the two specified types of ethanol in Brazil, the anhydrous and the hydrous fuels. The present work includes a comparative engine test bed performance study of a multi-fuel engine equipped with a programmable electronic central unit (ECU), fueled with anhydrous and hydrous ethanol. Fuel properties, engine performance, emissions and combustion parameters are reported using these two fuels for maximum power operating point. The programmable ECU was installed in order to make possible the setting of some parameters that are not accessible in engines operating with commercial ECU. This way, torque was optimized regarding spark timing and air fuel ratio, for all selected fuels and engine conditions tested. Test results presented the effects of anhydrous and hydrous ethanol on a multi-fuel engine performance, emissions and combustion.

In the 80s, due to the oil crisis, natural gas (NG) appeared as a fuel with great potential for replacing diesel in heavy duty vehicles. At that time, Petrobras, together with other companies, had developed partial conversion kit technology for diesel to diesel plus NG, known as “dual fuel” technology. Engine dynamometer and vehicle bus tests have been developed to verify the technical and economic viability of the “dual fuel” kit. For several reasons, the dual fuel program did not advance and the trials were interrupted. At the same time, other trials, using NG Otto cycle bus engines, manufactured in Brazil, were being conducted, mainly in São Paulo, although unsuccessfully.

Accurate simulation of fuel properties influence in internal combustion engines performance is a very complex approach and combines many physical and chemical concepts such as combustion phenomena, chemical kinetics, fluid dynamics, turbulence and thermodynamics. The right modelling of that is still a challenge and currently available software packages for engines simulation usually consider standard or surrogate fuels. The objective of this paper is the prediction of gasolines performance in internal combustion engines as an auxiliary tool in researches and developments of new fuels, reducing experimental timing and costs. It is proposed the use of kriging metamodels based on bench test results of a flexible fuel engine running with distinct blends of iso-octane, n-heptane, toluene and ethanol, to predict performance, energetic efficiency and pollutant emissions in function of fuel properties and operating conditions.

Experiments in engine test cells are under the influence of several parameters and types of equipment, which may impact the test results. Many variables of interest are derived from the combination of more than one quantity, increasing the results uncertainty of the final reported value. This paper describes a detailed procedure to calculate uncertainty of measurement of emission tests using a FTIR (Fourrier Transformed Infrared) emission analyzer. A Flex-Fuel engine using gasoline and ethanol was tested under different operating conditions on an engine dynamometer equipped with automation system. For each operating condition at least four different measurements were taken. The expanded uncertainty was calculated by the combination of Type A (due to repeatability) and Type B (due to calibration, sensor resolution and others).

Rapid Compression Machine (RCM) is an experimental tool developed to study engine combustion parameters. The RCM used is a pneumatically and hydraulically driven device which reproduces a single combustion shot, considering a compression and a partial expansion stroke. This paper describes RCM adaptations made in order to run Otto cycle tests using Brazilian regular gasoline (E25) [1]. These adaptations enable pre-vaporized air-fuel mixture combustion tests, representative of port fuel injection engines, by using a gasoline direct injection (GDI) injector. It is also presented RCM piston displacement and cylinder pressure comparisons to a real engine and RCM comparative results for different spark timings and compression ratios. These results show that RCM reproduced satisfactorily piston displacement and pressure curves during the combustion shots, when compared to real engine curves.