Tribological Assessment of Aluminum Cylinder Material for Piston Compressors in Trucks and Buses Brake Systems

Applying new technologies to reduce friction and wear in vehicles and equipment can minimize mechanical losses. This reduces power loss in internal combustion engines and reduces fuel consumption and emissions. Consumption of fuel energy can be reduced by the use of light metals, for example aluminum alloy, to produce vehicles and their aggregates and parts. In this case, the problem is poor tribological properties of those light weight metals, as well as the lower strength compared to the cast iron construction. For tribology research purposes, the contact surface of the aluminum cylinder of an experimental piston air compressor is reinforced with inserts of cast iron. The results of tribology research of the composite material are presented in the paper, explaining how parameters such as the sliding speed, contact time and contact area influence friction and wear of the material in relative tribological contacts, under constant normal force. The test procedures were performed on the ball-on-plate CSM® nanotribometer, in linear reciprocating sliding conditions with no lubricant. Material composition of the samples was determined using the Energy-Dispersive Spectroscopy. All measurements were realized at the Faculty of Engineering, University of Kragujevac

Valve dynamics in reciprocating compressors for motor vehicles

Pouzdanost i termodinamička svojstva stapnih kompresora uvelike ovise o ventilu. Budući da se ventili otvaraju i zatvaraju automatski, postoji intenzivno djelovanje dinamike ventila i elementa za brtvljenje na protok plina kroz ventil. Loše karakteristike ventila neminovno dovode do degradacije rada kompresora i /ili kratkog vijeka trajanja ventila. Kratki vijek trajanja ventila rezultat je prekomjernih udarnih sila između elementa za brtvljenje i drugih dijelova sklopa ventila. Usklađivanje ventila sa specifičnim stapnim kompresorom složen je zadatak koji zahtijeva primjenu odgovarajućih matematičkih modela prije nego se ventil uskladi. U ovom radu predstavljamo matematički model za predviđanje dinamike ventila. Matematički model se provjerava mjerenjima termodinamičkih karakteristika specifičnog stapnog kompresora u motornom vozilu. Zaključeno je da se matematički model dobro slaže s rezultatima laboratorijskih ispitivanja.Reliability and thermodynamic properties of reciprocating compressors are largely dependent on the valve. Since the valves open and close automatically, there is an intensive impact of the valve and the sealing element dynamics to the gas flow through the valve. Poor valve characteristics inevitably lead to degradation of compressor performance and/or short lifetime of the valve. A short lifetime of the valve is the result of excessive impact forces between the sealing element and other parts of the valve assembly. Matching the valves to the specific reciprocating compressor is a complex task that requires the use of appropriate mathematical models before the realization of the valve. The mathematical model for the prediction of the valve dynamics is presented within this paper. The mathematical model is verified by measurements of thermodynamic characteristics of the specific reciprocating compressor used in motor vehicles. It is concluded that the mathematical model agrees well with the results of laboratory tests

Determination of Combustion Process Model Parameters in Diesel Engine with Variable Compression Ratio

Compression ratio has very important influence on fuel economy, emission, and other performances of internal combustion engines. Application of variable compression ratio in diesel engines has a number of benefits, such as limiting maximal in cylinder pressure and extended field of the optimal operating regime to the prime requirements: consumption, power, emission, noise, and multifuel capability. The manuscript presents also the patented mechanism for automatic change engine compression ratio with two-piece connecting rod. Beside experimental research, modeling of combustion process of diesel engine with direct injection has been performed. The basic problem, selection of the parameters in double Vibe function used for modeling the diesel engine combustion process, also performed for different compression ratio values. The optimal compression ratio value was defined regarding minimal fuel consumption and exhaust emission. For this purpose the test bench in the Laboratory for Engines of the Faculty of Engineering, University of Kragujevac, is brought into operation

Binary Logistic Regression Modeling of Idle CO Emissions in Order to Estimate Predictors Influences in Old Vehicle Park

This paper determines, by experiments, the CO emissions at idle running with 1,785 vehicles powered by spark ignition engine, in order to verify the correctness of emissions values with a representative sample of vehicles in Serbia. The permissible emissions limits were considered for three (3) fitted binary logistic regression (BLR) models, and the key reason for such analysis is finding the predictors that can have a crucial influence on the accuracy of the estimation whether such vehicles have correct emissions or not. Having summarized the research results, we found out that vehicles produced in Serbia (hereinafter referred to as “domestic vehicles”) cause more pollution than imported cars (hereinafter referred to as “foreign vehicles”), although domestic vehicles are of lower average age and mileage. Another trend was observed: low-power vehicles and vehicles produced before 1992 are potentially more serious polluters

BENEFITS AND CHALLENGES OF VARIABLE COMPRESSION RATIO AT DIESEL ENGINES

The compression ratio strongly affects the working process and provides an exceptional degree of control over engine performance. In conventional internal combustion engines, the compression ratio is fixed and their performance is therefore a compromise between conflicting requirements. One fundamental problem is that drive units in the vehicles must successfully operate at variable speeds and loads and in different ambient conditions. If a diesel engine has a fixed compression ratio, a minimal value must be chosen that can achieve a reliable self-ignition when starting the engine in cold start conditions. In diesel engines, variable compression ratio provides control of peak cylinder pressure, improves cold start ability and low load operation, enabling the multi-fuel capability, increase of fuel economy and reduction of emissions. This paper contains both theoretical and experimental investigation of the impact that automatic variable compression ratios has on working process parameters in experimental diesel engine. Alternative methods of implementing variable compression ratio are illustrated and critically examined

HEAT TRANSFER IN EXHAUST SYSTEM OF A COLD START ENGINE AT LOW ENVIRONMENTAL TEMPERATURE

During the engine cold start, there is a significantly increased emission of harmful engine exhaust gases, particularly at very low environmental temperatures. Therefore, reducing of emission during that period is of great importance for the reduction of entire engine emission. This study was conducted to test the activating speed of the catalyst at low environmental temperatures. The research was conducted by use of mathematical model and developed computer programme for calculation of non-stationary heat transfer in engine exhaust system. During the research, some of constructional parameters of exhaust system were adopted and optimized at environmental temperature of 22 C. The combination of design parameters giving best results at low environmental temperatures was observed. The results showed that the temperature in the environment did not have any significant influence on pre-catalyst light-off time

New engine method for biodiesel cetane number testing

Substitution of fossil fuels with fuels that come from part renewable sources has been a subject of many studies and researches in the past decade. Considering the higher cost and limits of production resources, a special attention is focused on raising the energy efficiency of biofuel usage, mainly through optimization of the combustion process. Consequently, in biofuel applications, there is a need for determination of auto-ignition quality expressed by cetane number as a dominant characteristic that influences combustion parameters. The fact that the method for cetane number determination is comparative in nature has led us to try to develop substitute engine method for cetane number determination, by the use of the available laboratory equipment and serial, mono-cylinder engine with direct injection, DMB LDA 450. Description of the method, results of optimization of engine’s working parameters for conduction of the test and method’s Accuracy estimation are given in the paper. The paper also presents the results of domestic biodiesel fuels cetane number testing with the application of described engine method, developed at the Laboratory for internal combustion engines and fuels and lubricants of the Faculty of Mechanical Engineering from Kragujevac, Serbia

Some aspects concerning management of road transport of dangerous goods using contemporary information systems

In this paper, some aspects concerning the management of road transport of dangerous goods using contemporary information systems for the sake of energy efficiency increase are presented. The prerequisite condition for optimal utilization of available vehicle fleet and improvement of their operational activities in the domain of road transport of dangerous goods is using sophisticated information systems. Compatibility database presented in this paper, as the central and most significant part of the information system, enables and simplifies the first important task in that manner i.e. obtaining the detailed list of dangerous goods that can be transported in the vehicle intended. Besides that, the analysis of the effects of vehicle constructional features variation onto the mentioned list of dangerous goods allowed for transport can be conducted as well. The information obtained from the compatibility database in conjunction with the geographical information system provides the optimal solution to the transport routes

Some aspects concerning application of alternative fuels as regards fluid flow pattern and flame propagation in particular combustion chamber with strong macro flows

In this paper, some results concerning the evolution of the fluid flow pattern and flame propagation of various fuels in a particular combustion chamber with four tilted valves were elucidated. Flame propagation was represented by the evolution of spatial distribution of temperature in various cutplanes within combustion chamber. Flame front location was determined in the zones with maximum temperature gradient. All results were obtained by dint of multidimensional modeling of reactive flows in arbitrary geometry of IC engine combustion chamber with moving boundaries. The above mentioned results were analysed and presented for two different hydrocarbon fuels such as gasoline and methane and one alchocol based fuel such as ethanol. The results for all three fules considered were obtained by dint of eddy-viscosity model i.e. with standard k-ε model of turbulence. The interplay between fluid flow pattern and flame propagation is entirely invariant as regards fuel variation indicating that flame propagation through unburnet mixture considered fuels is not chemically controlled but controlled by dint of turbulent diffusion

Performance measurements on an experimental Otto/Diesel engine operating with different fuels

Multi-process working principle is one of the modern approaches to development of internal combustion engines. By combining the original features of the Otto and Diesel working processes, an improvement of the engine efficiency and ecological characteristics can be achieved. Examples for that are spark ignition engine with stratified charge as well as compression ignition engines with homogeneous charge. The experimental multi-process engine was developed as well as testing methodology, for the basic researches efficiency and ecological characteristics of the Otto/Diesel engine. This paper presents the results of the combination of Otto/ /Diesel working processes when the engine working with both conventional and bio-fuels. Results of initial tests of Otto/Diesel engine show a high potential to reduce particulate emissions. The investigation has shown certain disadvantages of the engine and the ways for theirs overcoming