István Barabás

Evaluation of the Behavior in Cornering for Different Classes of Passenger Cars by Numerical Modeling

This paper presents a study, using modeling methods, on the behavior of different classes of passenger cars in cornering. Taking into account the factors that influence the movement and tendency of the cars in cornering, the parameter values in the mathematical model were chosen so as to characterize the real situations encountered frequently in cars’ exploitation in the cornering process. In order to have relevant results for the chosen cars, different experimental loads (for each axle) were determined for different loading cases. The analytical model, developed in Mathcad, takes into account the geometrical parameters of the passenger cars and helps to determine the understeering or oversteering tendencies. The results were represented graphically in order to facilitate their comparison.

Evaluation by Experimental Methods of the Parameters that Influence the Behavior of Various Passenger Cars Classes in the Braking Process

This paper presents a study - by experimental methods - on the behavior of different classes of passenger cars in the braking process. In the experimental determinations, the parameter values were chosen to characterize the real studies case, commonly encountered, of the passenger cars use in the braking process. Thus, it is considered the experimental determination of the braking ability parameters of the studied passenger cars depending on tire pressure, loading on axles, nature and condition of the rolling surface, tire type (summer or winter) and type of braking system. The way in which behave the passenger cars equipped with winter tires in a situation where the weather requires summer tires at different inflation pressures, also show interest. For the frequency assessment of the brake using in urban areas at different traffic densities it has been used Android applications. The results were represented graphically in order to facilitate theirs comparison.

Exhaust Emissions of a Medium Power Diesel Engine Operated with Biodiesel

The purpose of this study was to identify from experimental researches the results regarding the nitrogen oxides (NOx) emissions and hydrocarbon emissions (HC), emissions of a four-stroke, four cylinder, direct injection of a Romanian medium power diesel tractor engine at partial loads operating on diesel fuel (DF), rapeseed methyl ester (RME), degummed and filtered (5 μm) pure rapeseed oil (RO100) and its blends with diesel fuel: 20% pure rapeseed oil-80% diesel fuel (RO20), 50% pure rapeseed oil-50% diesel fuel (RO50), 75% pure rapeseed oil-25% diesel fuel (RO75) compared to diesel fuel. The main properties of the tested fuels (density, kinematic viscosity, oxidation stability, acid value, peroxide number, coke content, water content and cetane number) have been determined. The value of NOx emissions for the experimented biofuels is smaller up to 53% (for RO100) and increases up to 37% (for RO75) for different engine loads as compared to the diesel fuel. The HC emission shows a decrease for all biofuels used in the experiment ranging between 4% (for RO100) and 63% (RO75) at different loads relative to the diesel fuel.

Influence of TiO2 Nano-particles Content on Physicochemical and Tribological Properties of Lubricant Oil

This study deals with research activities that aim to emphasize the effect of titanium dioxide (TiO2) nano-particles, used as additive, on physicochemical and tribological properties of lubricant engine oil. Commercial TiO2 Degussa P25 nano-particles with 21 nm average particle size were blended with commercial Castrol (10W-40, A3/B4, SL/CF) engine oil, varying concentrations of nano-particles (between 0.01% wt. to 0.1% wt.) in lubricating oil, under both magnetic stirring and ultrasound conditions. The physicochemical properties of the oil and dispersions which contain TiO2 nano-particles were determined e.g. density, viscosity, viscosity index and flash point. In order to evaluate if there are chemical interactions between TiO2 nano-particles and oil, FT-IR spectroscopy was utilized. The tribological properties were tested on block-on-ring tribotester. Density, viscosity and viscosity index tend to increase with TiO2 content. The studies provide information regarding the utilization of TiO2 nanoparticles as additive in lubricant engine oil which can improve the physicochemical (density, viscosity and viscosity index) and tribological (coefficient of friction) properties, which can leads to fuel economy in automotive engines.

Fuel Properties of Diesel-Ethanol-Tetrahydrofuran Blends: Experimental and Theoretical Approaches

Oil based fuel is the most important energy source in the road transport sector which has an increasing demand of fuel meanwhile its raw material resources are decreasing. Therefore, new fuels and blends are urgently needed. Blends of diesel fuel-ethanol could be one of the solutions. For this its properties must be described properly. To describe density, viscosity and surface tension of these types of fuel, five blends containing 2, 5, 8, 10 and 15% ethanol were prepared and stabilized at 20 °C and 0 °C by using tetrahydrofuran as surfactant. The density and viscosity of blends were measured at 0, 15, 40 and 50 °C and their surface tension was evaluated at 20 °C. In order to characterize the hazardousness of these blends their flash points were measured. The density and viscosity of the blends were mathematically described as a function of their composition and temperature. Surface tension was modelled as a function of ethanol content.

Key fuel properties and engine performances of diesel-ethanol blends, using tetrahydrofuran as surfactant additive

In this paper there were presented researches related to preparation and characterization of physicochemical properties of diesel-ethanol blends stabilized with tetrahydrofuran as surfactant, in order to be used as fuels in compression ignition engines. The main spray characteristics and engine performances of these blends were evaluated by using AVL Fire software. In the first stage of the studies, commercial diesel was mixed with ethanol, in different concentrations (between 2% and 15% v/v), followed by the addition of tetrahydrofuran (THF) until the blends were miscible, i.e. the blends were stabilized. The experiments were done at room temperature (22 0C). The obtained blends were characterized in order to determine the chemical composition and physicochemical properties, i.e. density, kinematic viscosity, surface tension. UV-Vis spectroscopy was utilized in order to determine a semi-quantitative evaluation regarding the chemical composition of the prepared blends and chemical interaction between diesel, ethanol and THF. Based on the determined properties, the fuel spray characteristics, engine performances and emission characteristics were evaluated by simulation using the AVL Fire software. The obtained results regarding physicochemical properties of blends were compared with diesel. Some improvements were observed when operating with the prepared blends compared to diesel with respect to engine performances and emission characteristics. Based on physicochemical evaluation and computer simulation, it was demonstrated that diesel-ethanol-tetrahydrofuran blends can be used as alternative fuel in compression ignition engines.

Estimation of Boiling Points of Brake Fluids

One of the most important properties of brake fluids is their boiling point. A too low boiling point may permit the forming of vapor during frequent and/or severe braking. Hereby the brake fluid becomes compressible and the braking performance decreases.

Automated test bench for study of the fuel injection process

The paper presents the design, implementation and use of an automatic test bench for the injection process, using an economical solution for recording successive images of a fuel jet injected into a chamber pressurized with nitrogen at ambient temperature, with a camera. Injection pressure can be adjusted with high precision using a closed loop PID control (closed loop). The test bench operation is synchronized by a computer-assisted system. Experimental results are also summarized for research of the diesel injection process.