Improvement of the Automotive Spark Ignition Engine Performance by Supercharging and the Bioethanol Use

摘要

The general objective of this paper is application of the supercharging method and bioethanol use at the spark ignition engine for improving performance of power and torque, improving engine efficiency, decrease of the emissions level and increases of the engine specific power. The paper brings an important contribution to pollution problems solving in large urban areas, the solution can being easily implemented on spark ignition engines in running, even on the old designs which can be converted to fit the current rules of pollution. A modern method to increase efficiency and specific power of the spark ignition engines is supercharging. Supercharging is common for diesel engines, but for SI engines becomes restrictive because of the main disadvantages represented by abnormal combustion phenomena with knock, exhaust gases temperature increasing, engine thermal and mechanical stresses increasing. By using modern control methods of the combustion, supercharging becomes an efficient method even for SI engine. The theoretical and experimental investigations were performed on a 1.5L aspirated spark ignition engine with MP injection which was supercharged. The supercharged engine was fuelled with gasoline-bioethanol blends. The use of bioethanol at supercharged SI engine assures an efficient cooling effect of the intake air due to its higher heat of vaporization. The intake air cooling effect leads to a volumetric efficiency increasing and the knock appearance risk is reduced. For to achieve of the research objectives the following methodology was used: modelling of the thermo-gas-dynamics processes inside engine cylinder for the theoretical evaluation of engine energetic performance; experimental investigations carrying out on the test bed of the SI engine in two versions: aspirated engine and supercharged engine fuelled with gasoline- bioethanol blends, respectively. For to achieve of the research objectives the following methodology was used: modelling of the thermo-gas-dynamics processes inside engine cylinder for the theoretical evaluation of energetic and pollution performance for aspirated engine and also for of the supercharged engine fuelled with gasoline-bioethanol blends in order to decrease the experimental investigations volume; experimental investigations carrying out on the test bed of the SI engine in two versions: aspirated engine and supercharged engine fuelled with gasoline-bioethanol blends, respectively; the interfacing of the electronic control units for the supercharged spark ignition engine fuelled with gasoline- bioethanol blends. The obtained results of the research are: development of a physic-mathematical model to simulate thermo-gas-dynamics processes inside engine cylinder; determining the bioethanol influences on the engine cylinder filling; determining the bioethanol influences on the supercharged spark-ignition engine combustion process; engine efficiency increasing by up to 10 %, specific power increasing by up to 33 %, pollutant emission levels reduction (was obtained a reduction of 20 % for NO_x emissions, a 10 % reduction of CO emission and a 13 % reduction of HC emission); establishing the optimal correlation between dosage-electric spark advance-boost pressure-exhaust gases temperature-coefficient of excess air on one hand and functional regime of the engine on the other hand. The abnormal combustion phenomena with knock study in this paper were not developed. As a research novelty is the solution for use of gasoline- bioethanol blends at the supercharging SI engine. Original elements of the research are: application of the supercharging procedure to an aspirated car spark ignition engine; use of gasoline- bioethanol blends as an injected fuel in blower downstream with effect of cooling the compressed air. The SI engine supercharging and use of gasoline- bioethanol blends is a good method to efficiency and power performance increasing. The pollutant emissions level decreases due to the improvement of the combustion processes. Bioethanol can be considered as an efficient anti-knock agent.