Search Results

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.

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.

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.

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.

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.

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 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.

The automobile industry has developed and marketed hybrid electric vehicles (HEV) internationally for over 10 years. The presence of batteries in these vehicles poses difficulties for their approval in laboratory trials. The difference between the initial and final battery state of charge changes the energy balance measured in the tests, affecting the emissions and fuel economy levels. Two proposals have emerged to address this problem. One is described in ISO 23274, which consists in determining and applying a correction factor to the emissions and fuel economy results. This factor is based on the difference between the initial and final battery state of charge after the test. The other is described by SAE J1711 which consists in conditioning the battery, in order to equal the state of charge level at the end and start of the test, avoiding the factor recalculation.

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.

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.

Uncertainty in measurements is a complex issue to obtain accurate results in vehicle fuel consumption tests. Petrobras Research Center carried out a study to calculate the final uncertainty of measurement during a vehicle fuel economy test following a feasible method that can be used in many laboratories. This study was based on the ISO-GUM (Guide to the expression of uncertainty in measurement) and on the Brazilian legislations ABNT NBR-6601 (pollutant emission) [1] and NBR-7024 (fuel economy tests) [2].

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.

On-board measurement is a powerful method to assess vehicular exhaust gas emission, since it enables the acquisition of instantaneous raw emission values in real-world conditions. While the vehicle emissions are subject to traffic and environment fluctuations, on-board measurement is a fast and economical way to generate data for fleet emission inventories, for instance. It is part of the mandatory testing for heavy-duty vehicles in the USA, as regulated by the USEPA. In 2004, Petrobras (Brazilian Oil Company) first experienced on-board emission measurements while participating in an international joint project, whose objective was to obtain information regarding the light-duty vehicular gas emission contribution to pollutant levels in some of the major Latin-American cities.

Natural gas (NG) produced in the Urucu area (Amazon Forest) has low methane and high nitrogen and therefore does not meet current NG specifications for vehicular use, as established by standard number 104 of ANP (National Petroleum Agency). This paper reports the steps for these NG conversion kit adjustments and also the results and comparisons of vehicle performance, emissions and fuel economy tests on a chassis dynamometer. The vehicles were tested with different fuels like regular NG, Amazon Forest NG, gasoline and ethanol. The results were presented to ANP that authorized in the beginning of 2005 the experimental use of the Urucu natural gas for 30 months. Also reported on this paper is an overview of the Brazilian NG fleet, present and future emission legislation, fuel specification, new trends on NGV (Natural Gas Vehicle) market and conversion kit technologies. Updated information is included regarding the experimental project of Urucu natural gas that is running on Manaus city.

This paper presents a methodology proposed by the PETROBRAS Research Centre (CENPES) to simulate in a laboratory a route performed during field emission tests run with an on-board emission measurement system. It also includes the procedure followed to build the drive cycle and to implement it at the CENPES' Vehicle Test Laboratory. Laboratory simulation of local urban routes, for instance, allows analyzing the impact of a new fuel formulation on the emission levels of a local fleet with higher accuracy and repeatability, as the test conditions can be better controlled. The usage of on-board emission measurement systems is more expensive and is subject to fluctuations in the traffic conditions, making comparative tests more difficult. In order to generate the new cycle, data acquired during the field tests was used to determine speed profiles and an average speed distribution was calculated.

This paper presents a proposed methodology developed during a research project at CENPES - PETROBRAS Research Center, to simulate a typical urban traffic cycle in the city of São Paulo on a chassis dynamometer. This cycle can be used in pollutant gas emission tests for light duty vehicles in laboratories. The implementation of a representative city cycle in a laboratory allows its simulation under controlled conditions. It can be applied, for example, in emission inventories and the impact of air quality in public health studies, without the need for on-board emissions measurement equipment for field use. This kind of equipment is generally expensive and the repeatability for the same cycle can be difficult to achieve, mainly due to traffic variants such as the day of the week, time, and weather conditions.