Study Of Light Duty Vehicle Emission Characteristics At High Altitudes

Since the invention of the internal combustion engine,one of the most significant problems has been pollutant emissions resulting from the combustion.This aspect becomes even more aggravated by the rapid growth of the cars fleet at the global level mainly in countries of large territorial extensions.Engine performance and emissions can be affected by a large number of variables.In this project a light duty,spark ignition,gasoline engine(JL465Q5,1000 cc)was evaluated computationally considering pressure changes at different altitudes,in a range from sea level to 5000 m every 500 m,and engine speeds between 800 to 5000 rpm as most important variables for analysis.The model was built in the software called WAVE designed by Ricardo software.In order to build a more attached to reality model,all systems required for engine operation were configured based on information gathered in previous works with this type of engine such as: intake air system,port fuel injectors,cylinders,exhaust system and after treatment pollutant gases system,for this simulation three way catalyst converter.In addition,some parameters required for the sub models using WAVE were configured according to data collected from previous researches,referenced during the development of the study.Fifty-five cases(55)were simulated accurately enough in order to analyze combustion,performance and emissions results.The pressure variation with altitude proves to be a very strong effect on the combustion because the air flow decreases significantly,so in these conditions it is very difficult to record engine performance at wide opening throttle points.As a chain effect,deterioration of combustion produced several significant reductions in engine power and efficiency,each 500 m a decrease of 6-7% and 0.1 to 0.28%,respectively was estimated.For this model regarding emissions,high production of the main pollutants(CO,HCs and NOx)was reported.Carbon monoxide concentration increases with altitude and engine speed;Hydrocarbons rise with increasing altitude and engine speeds;Nitrogen oxides growth with altitude changes but diminish with engine speed.Three way catalyst produced a high conversion efficiency operating at medium and high speed: for CO(about 80% in average)and HC(90% approximately)which were affected significantly at low engine speed,however low conversion rates were reported for NOx due to the fact that the model does not provide reactions to eliminate NO2 and the reduction of NO is only a function of the availability of CO.For NO,the calculated maximum efficiency was only 60% evaluated at a high engine speeds.In addition,fuel consumption test of two gasoline,naturally aspirated,2.5 liters capacity vehicles(Subaru Legacy-Subaru Forester)was performed in laboratory at 6 different vehicle speeds and several atmospheric conditions(pressure and temperature).As accurately possible recreating real road conditions a decrease was recorded in the fuel consumption of the two tested vehicles.Mainly this tendency is created due to the reduction of air drag as a result of decreased air density at higher altitude.Besides,fuel consumption of the two test vehicles became higher as ambient temperature falls down.Furthermore,grater resistance force was recorded with increasing speed for both vehicles.