Exhaust EmissionsTask 3 P4Petrol and diesel engines work in slightly :: Design and Technology

Exhaust EmissionsTask 3 P4Petrol and diesel engines work in slightly different ways and burn different fuels, so they produce different exhausts Petrol and diesel engines work in slightly different ways and burn different fuels, so they produce different exhausts. Compared with petrol engines, diesel engines produce smaller amounts of unburnt and partially burnt fuel but can produce more nitrogen oxides and large amounts of smoke. These particles consist of soot, hydrocarbons, sulphur-based chemicals and volatile organic compounds. Heavy duty diesel vehicles, such as trucks, can be very polluting because they produce large amounts of particulates and nitrogen oxides. Diesel exhaust has also been shown to be a probable cause of cancer. WHAT ARE DIESEL ENGINE EXHAUST EMISSIONS? Cold Start Emissions - Starting and driving a vehicle the first few minute’s results in higher emissions because the emissions control equipment has not yet reached its optimal operating temperature. Running Emissions - Pollutants are emitted from the vehicle's exhaust during driving and idling after the vehicle is warmed up. Diesel engine exhaust emissions are a mixture of gases, vapors, liquid aerosols and substances made up of particles. They contain the products of combustion including: * carbon * nitrogen * water * carbon monoxide * aldehydes * nitrogen dioxide * sulphur dioxide * Polycyclic aromatic hydrocarbons The carbon particle or soot content varies from 60% to 80% depending on the fuel used and the type of engine. Most of the contaminants are adsorbed onto the soot. Petrol engines produce more carbon monoxide but much less soot than diesel engines. WHAT FACTORS AFFECT THE COMPOSITION OF DIESEL FUMES? * the quality of diesel fuel used; * the type of engine, e.g. standard, turbo or injector; * the state of engine tuning; * the fuel pump setting; * the workload demand on the engine; * the engine temperature; * Whether the engine has been regularly maintained. WHAT DOES THE COLOUR OF THE SMOKE PRODUCED INDICATE? Smoke is the product of combustion. Vehicles at a workplace may produce three kinds of smoke, two of which indicate engine problems. The three types are: * Blue smoke (mainly oil and unburnt fuel). This indicates that the vehicle has been poorly serviced and/or a tuned engine * Black smoke (soot, oil and unburnt fuel). This indicates there is a mechanical fault with the engine * White smoke (water droplets and unburnt fuel) which is produced when the engine is started from cold and disappears when the engine warms up Exhaust fumes are just one of the ways CO2 adds to climate change Not only do vehicles cause localised air pollution, they are also responsible for a large proportion of greenhouse gas emissions.