Oxides of nitrogen mainly found in the form of NO and NO 2. Deceleration from high speed produces highest CO because of reduced supply of oxygen. It is lowest during acceleration and at high steady speeds. CO emission is high during idling and reach maximum during deceleration. The only way to control the HC emission is by controlling speed. So mixture always remains rich or lean with fuel and it’s not possible to avoid HC emission. However, it’s never possible to supply the fresh charge with this proportion.
#TYPES OF COOLING SYSTEMS IN IC ENGINES FREE#
Theoretically, it can be said that the petrol engine exhaust can be made free from CO by operating it at correct air-fuel ratio which is 15:1. These factors are indirectly affecting the HC emission and we can reduce their effects by practicing regular and proper maintenance of our vehicle.Ĭarbon monoxide, being an intermediate product of combustion, comes out in the exhaust gas if the oxidation of CO to CO 2 is not complete. Other maintenance variables which affect the HC emissions comprise engine wear, lubricating oil level, cooling efficiency and carbon deposits on cylinder wall. The operating variables like air-fuel ratio, speed and load are the factors which we can control to reduce HC emission. The emission amount of HC is closely related to design variables like breathing system design and combustion chamber design, which we can’t change. Engines are subjected to high working temperature.The unburnt hydrocarbon emission is the direct result of incomplete combustion. Cooling fins under certain conditions may vibrate and amplify the noise level. Relatively large amount of power is used to drive the cooling fan. No risk of damage from frost, such as cracking of cylinder jackets or radiator water tubes. This system of cooling is particularly advantageous where there are extreme climatic conditions in the arctic or where there is scarcity of water as in deserts.Ħ. It is lighter in weight than water-cooled engines due to the absence of water jackets, radiator, circulating pump and the weight of the cooling water.ĥ. Its design of air-cooled engine is simple.Ģ. Usually fin height varies from 15 to 25 mm vehicle-air-conditioningĪir cooled engines have the following advantages:ġ. Smaller inter spacing between the fins results in smaller flow area of cooling air and hence input cooling air is less Larger inter spacing between the fins offers larger area for cooling air but the heating of the air is less, so more cooling air is required For efficient cooling the length of the fins and the spacing between them is quite important Low temperature increases the viscosity of lubricant causing more loss due to friction The vaporization of the fuel is less resulting in lower combustion efficiency Thermal efficiency is decreased due to more loss of heat carried by the coolant Higher temperatures also lower the volumetric efficiency of the engine.
This makes it necessary for, the temperature variation to be kept to a minimum. Due to overheating, large temperature differences may lead to a distortion of the engine components due to the thermal stresses set up. Due to very high temperatures, the film of the lubricating oil will get oxidized, thus producing carbon deposits on the surface. (Platinum, a metal which has one of the highest melting points, melts at 1750 ☌, iron at 1530☌ and aluminium at 657☌.) Therefore, if the heat is not dissipated, it would result in the failure of the cylinder material. The temperature of the burning gases in the engine cylinder reaches up to 1500 to 2000☌, which is above the melting point of the material of the cylinder body and head of the engine.
The cooling system is provided in the IC engine for the following reasons: Requirements of cooling system in the IC engine