Search Results

Currently, fuels development is strongly dependent on experiments. New engines and vehicles simulation methodologies contribute to speed up R & D projects deadlines, as well as reducing costs. This paper presents a modeling methodology for a vehicle deceleration load curve (coast down) prediction and simulations of coast down variations impact on urban and highway autonomies. Two coast down curve mathematical models were successfully developed and validated. The first one, based on vehicles technical specifications and empirical equations, resulted in percent differences up to 9% compared to the experimental results. This is lower than the variation established on coast down standard, which is 15%. The second, generated by regression analysis between other vehicles characteristics versus experimental results of F0 and F2 (coast down curve parameters), resulted in percent differences up to 15%, for six of the eight vehicles.

This paper assesses the use of E85 fuel in Brazilian flex fuel light duty vehicles. E85 is composed of 85% of anhydrous ethanol and 15% of gasoline in volume base. Advantages and disadvantages of the E85 use are presented in comparison to hydrated ethanol (H100) that is currently available in the Brazilian market. Additionally, the blend H81 made by 81% of hydrated ethanol and 19% of E22 gasohol (gasoline with 22% of anhydrous ethanol), resulting on a fuel with 15% of gasoline was also investigated. The main difference between E85 and H81 is the water content due to the use of hydrated ethanol. As the E85 is not available in Brazil, this is the correspondent feasible mixture with commercial fuels in the country. Both fuels were assessed and compared to hydrated ethanol regarding cold start, cold driveability, speed recovery, pollutant emissions, fuel economy and deposit formation with engine and vehicle tests performed in the Petrobras Research Center (CENPES) laboratories.

Vehicles manufacturers, in search of cost reduction, fill the tanks of recently manufactured vehicles with the least volume of fuel necessary for future commercialization. The adoption of such practice, depending on the diesel fuel storage conditions, may lead to oxidation products formation in the fuel system and to problems during the first start of these vehicles. Some vehicles manufacturers, trying to minimize the occurrence of these problems, replace the diesel fuel in the vehicle tank with new fuel when vehicle storage time reaches 90 days. As a result of such occurrences, the opportunity for a first fill diesel fuel development, that presented better oxidation stability during storage, was identified. In the first stage of the special diesel fuel development, various analyses where conducted in laboratory, in the sense of defining criteria for the fuel formulation, taking into consideration the chemical variability of commercial Brazilian diesel fuel type A and biodiesel.

The growing humanity concern about harmful effects of global warming in consequence of greenhouse gases (GHG) emission has been translated on CO₂ emission reduction targets for the next years in many countries. These targets and regulations for exhaust gas pollutants with local effects have led to the introduction of new vehicular technologies as gasoline direct injection or hybrid vehicles, for instance. New fuel developments, including alternative ones, have already been an important contribution. In the United States, up to 2016, all manufacturers shall accomplish with the average production target of 34.1 mpg, becoming 49.6 mpg in 2025. In Europe, the 2015 target is 130 g/km of CO₂ average emission by each manufacturer production and reduced for 95 g/km in 2020. Japan, China, India and other countries have their own limits defined for the next years too.

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.

In Brazil, gasoline boats are mostly equipped with imported engines. These engines are not prepared to gasoline with high ethanol content. CENPES (PETROBRAS Research and Development Center) has large experience in automotive engines and vehicles testing for fuels development. However, gasoline marine engines need infrastructure, methodologies, and equipments different from those typically used in automotive testing. This work describes infrastructure and methodologies developed by CENPES to assess fuels performance in an outboard engine, running at water tank. It also studies the influence of gasoline formulations with different ethanol contents in this kind of engine performance. Additionally, it was performed an endurance test using a gasoline formulation with 10%vol. ethanol.

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.

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.

Through a market analysis, PETROBRAS identified an opportunity to launch a new product dedicated to diesel boats market. This paper describes the activities performed by PETROBRAS research center (CENPES) during the new diesel development: new or improved methodologies to ensure reliable comparative performance, fuel consumption and smoke emissions analysis, with appropriate precision to elucidate differences between the new fuel and the conventional marine diesel. Performance tests were conducted by using radar monitoring. For fuel consumption, constant engine speed tests were made, with fuel flow measurement and acquisition. Smoke tests were performed using a total flow smokemeter, installed directly on the exhaust gas pipe. Results showed that, because of its special characteristics, the new diesel allows performance gains up to 6% and smoke emissions reduction up to 83%. Fuel consumption remains in the same level of regular marine diesel.

The development of new fuels involves several areas of an oil company and several tests, including vehicle emissions tests on chassis dynamometers and engine performance tests on engine bench laboratory. Particularly for diesel and blends of gasoline fuels, an important test is to evaluate the engine speed profile during the vehicle cold start. In this work, for engine speed profile analysis, it was developed a system to acquire data using the engine's flywheel ring gear information and the audio input of a standard notebook computer. It was also developed a specific software to analyze the acquired signals. The system is able to point out several important features of the engine start such as the starter motor beginning of operation, the maximum engine speed during the start time, the settling time and the engine idling speed. All of this information can be collected using a low cost set of instrumentation devices.

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.

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.

In last few years, Petrobras has been working to make feasible the vehicular usage of the natural gas (NG) produced in Brazilian north region. This gas is produced in the Urucu field located at the Amazon forest. Due to its low methane and high nitrogen contents that could promote, respectively, performance losses and higher NOx emissions, Urucu's gas does not meet ANP specification for vehicular natural gas. Previous studies performed at Petrobras Research Center (CENPES) indicated the possibility of vehicular application for Urucu's NG, attending the Brazilian emission legislation (PROCONVE). However, with new PROCONVE's phases, recent vehicles have more advanced technological levels of fuel injection and catalyst systems, which require that kits for natural gas follow this evolution, including interfacing with flexible fuel engines.

In the last years, world's general concern about climate changes and their effects on human life has strongly increased. Some countries, such as European Union members and the USA, are improving their legislations in order to limit vehicular CO2 emissions. To comply with these limits, new vehicle and fuel technologies are being developed in many places. Thus, the main goal of this paper is to present a comprehensive overview of some of these technologies for light-duty vehicles based on international published references and some experiences of Petrobras Research Center (CENPES). Also, this work addresses to some regulatory initiatives, such as new CO2 emission legislations and fuel economy labeling programs.

In order to simulate the real behavior of vehicles during laboratory tests, such as fuel consumption [1] and pollutant emissions [2], coast down coefficients must be set on the chassis dynamometer control system. These coefficients are used to determine load curves, which represent the resistance imposed on the vehicle movement by the wheels rolling and the air, being obtained from track tests performed according to Brazilian standard ABNT NBR 10312 [3]. However, coast down tests depend on the availability of long and flat tracks. This may entail costs for deployment or leasing of facilities with these characteristics, which may include even long commutes of human and material resources, depending on its location. This paper proposes an alternative methodology for coast down coefficients determination, from experiments on chassis dynamometer and vehicles aerodynamic specifications. It was applied to some Petrobras Research Center (Cenpes) test vehicles.

Nowadays, due to the global warming questions related to CO2 emissions, many countries legislation lead automotive and fuel industries to search for higher efficiencies in their products. Therefore, new engine technologies and cleaner fuels are being developed and launched in the market. This paper presents a study of efficiencies on chassis dynamometer tests, in order to evaluate vehicle and fuel contributions. Tests were performed using one Brazilian flex fuel vehicle in full load condition at constant speeds to evaluate the losses of each part of the system, such as, wheel, air resistance and powertrain. The vehicle energy parcels were determined. So, it was possible to assess vehicles mechanical losses, aerodynamic losses and also the engine efficiencies.

Fun to drive is one of the main driver’s wishes. Therefore, it is a relevant attribute in vehicles and fuels development. Vehicles performance depends, mainly, on ignition and fuel injection strategies adopted by their manufacturers. However, fuel characteristics may significantly influence acceleration and speed recovery results. Regarding fuel development, it is important to establish test methodologies, which minimize experimental uncertainties. So, it is possible to detect any small acceleration or speed recovery variation and relate it to fuel characteristics changes. An alternative to traditional track tests is to perform speed recovery tests on chassis dynamometer, where it is possible to mitigate the effect of some parameters which may significantly vary on track, such as, ambient temperature, ground irregularities and wind direction and speed.