Search Results

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.

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.

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.

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.

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.

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.

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.