Search Results

Lean air-gas mixture combustion systems seem to be very promising solutions for IC engines in terms of lower emission indexes and higher thermal efficiency, especially in part-load operation. The main problem however is the necessity to provide the bigger activation energy for ignition of lean and very lean mixtures. In several publications and in research performed by the authors of this paper it has been confirmed, that the implementation of turbulent jet ignition (TJI) results in significantly faster inflammation of lean CNG/air mixture due to the improvement in on-ignition mechanism. The TJI-system consists of two chambers connected with nozzles. The orifices generate complex charge movement and decrease significantly the charge homogeneity in the pre-chamber, interrupting therefore first ignition process.

Direct injection into open chambers of Diesel- and S.I.- Engines is considered by the experts of automotive engineering worldwide as the best way for future economy and ecology engines [1]. Beside of the best fuel saving passenger cars driven by Diesel engines, advanced Diesel like Stratified Charge Engines as the CCSC (Controlled Combustion Stratified Charge) and the MESC (Mixture Exhaust Stratified Charge) -Engines open the way for future developments. Both engines work with the following new elements: Air assisted injection for the formation of the combustible mixture in the small cavities of prechambers, where the load control is achieved by the quantity of the injected fuel without the need of throttling the charge of the main chamber as common in today's SI engines. Pulsed Jet Combustion, where at first in small cavities of prechambers a rich mixture gets ignited.

The paper discusses the analysis of gasoline atomization generated by piezoelectric fuel injectors operating in a high pressure direct injection system. The methodology and tests results of the influence of the fuel injection pressure and combustion chamber back pressure on the changes of the fuel spray geometrical parameters during the injection and on the values characterizing the injection quality have been presented in the paper. It was stated that the growth in the back pressure by 50% results in a decrease in the linear spray penetration by 15% and a change in the injection pressure by 25% reduces the spray penetration by 1.6-4%. Similar relations are found for the fuel spray area and are even stronger for the spray penetration velocity.

The paper discusses the analysis of ethanol (E85) fuel atomization generated by piezoelectric fuel injectors operating in a high-pressure gasoline direct injection system. The methodology and tests results of the influence of the fuel (E85) injection pressure and combustion chamber back pressure on the changes of the fuel spray geometrical parameters during the injection and on the values characterizing the injection quality have been presented in the paper. The tests were performed for one value of the air backpressure (1.5 MPa; as in modern supercharged DI engines) at the injection pressures of 5 and 20 MPa. The following comparative indexes were analyzed: linear and radial spray penetration during the injection and the velocity of the spray propagation. The investigation consisted in a visual recording of the process of fuel (ethanol E85) injection realized into a high pressure chamber.

In the paper the results of a comparative analysis of the changes in the fuel spray shape, penetration and its angle in the piezoelectric injection have been discussed. The results of the observation of the fuel (bio-diesel) spray with the use of high-speed camera (100 μs frame frequency) have been presented. The tests were performed for a multi hole piezoinjector and each time the whole fuel spray was observed and analyzed. The injector was placed in a closed chamber with an adjustable backpressure in the range of 0-4.5 MPa. At this stage of the research the authors investigated the influence of the chamber backpressure on the fuel spray shape, atomization and spray front displacement. Moreover, the parameterization and digital processing (including automation) of the obtained images have been presented, too. The influence of the pressure and the timing of the injection on the variable-in-time spray parameters have been shown.

The task of “Around the world in 80 days on 1000 liters of fuel” was successfully accomplished on the 3rd of August 2000. Volkswagen has set up a formidable record with its Lupo 3L TDI, the world's first ever 3 liters car. In 80 days this car traveled 33333 kilometers across 5 continents using only 792.57 liters of fuel. 2.38 liters per 100 kilometers, equal to 98.9 miles/gallon, at an average speed of 85.6 km/h, what has never been done before. Beside other features of the car and the drive train, credit must be given to the 1.2 liter Diesel engine equipped with Unit Injectors. Further improvement of the fuel consumption and emissions might be reached with Diesel-like and S.I.-like Stratified Charge engines as discussed in this paper.

The paper presents the thermodynamic analysis of the engine supplied with small and large diesel fuel doses while increasing natural gas quantity. The paper presents changes in the combustion process thermodynamic indexes and changes in the exhaust gas emissions for dynamically increased share of the gaseous fuel. The cylinder pressure history was subject to thermodynamic analysis, . based on which the mean indicated pressure, the heat release rate, the quantity of heat released as well as the pressure rate increase after self-ignition were determined. These parameters were also referred to the subsequent engine operation cycles by specifying the scope of the change per cycle. The relationship between the engine load and the start, the center and the end of combustion while increasing the gas amount supplied to the cylinder was indicated.

The paper presents experimental and model research related to the fuel spray - wall interaction in terms of pressure and air back-pressure variability. Using a constant volume chamber the authors performed a qualitative and quantitative analysis of the fuel spray reaching the piston. The experimental research was supported with a model research using the FIRE 2010 software by AVL. On this basis the fuel concentration and its distribution in individual areas of the combustion chamber were determined (in the piston combustion chamber). A greater impact of the injection pressure (rather than the back-pressure) on the fuel spray distribution in the combustion chamber was observed and on the fuel spray interaction with the chamber walls in the piston. In such a case the problems of the contact of a liquid fuel with the cylinder walls and/or the combustion chamber walls is becoming increasingly important in terms of the fuel film formation and HC emission intensification.

Controlled combustion in direct injection stratified charge engines can be achieved by the use of impinging jets for injection as well as for ignition, in association with a close-loop, electronic control system. Upon the description of the method of approach required for the design of a control strategy, illustrated by application to a conventional diesel engine, salient features of novel concepts for direct injection stratified charge engines are presented.