The diesel and petrol engines that are used in most cars are highly similar. In essence, they are internal combustion engines that work using a two or four-stroke cycle. In an internal combustion engine, the power cycle is made up of four phases: intake, compression, power and exhaust.
In the intake phase, air is drawn into cylinder through the opening intake valve. In the compression phase, the intake valve closes and air is compressed with fuel. At this point, the mixture of fuel and air is ignited to cause an explosion. It is this explosion that causes the piston to downwards and drive the crankshaft to produce motion. This is the power phase. The final phase is exhaust where the spent air-fuel mixture is expelled out of the cylinder through the opening exhaust valve so that a new cycle may begin.
The main difference between diesel and petrol engines is that petrol engines use spark plugs to ignite the air-fuel mixture, while diesel engines rely solely on heavily compressed air. As mentioned earlier, Rudolf Diesel found that the temperature of air could be made to increase high enough if it was heavily compressed. The temperature would rise so high to the point where it could cause the ignition of diesel fuel. Therefore in diesel engines, air in cylinder would be very heavily compressed, typically to around 14 to 23 times its original volume.
In petrol engines, the compression ratio is generally much lower, because they rely more on the spark plug to begin the power phase. The compression ratio is petrol engines is typically around only around 7 to 10, with high performance vehicles having higher compression ratios of up to High compression ratios are desirable because it results in higher thermal efficiency. In other words, more energy can be extracted out of the air-fuel mixture.
This also explains why diesel engines are considerably more efficient than petrol engines. In fact, diesel engines have the highest thermal efficiency of any internal combustion engine. Besides being very efficient, what other advantages do diesel engines have over their petrol counterparts? And what disadvantages do diesel engines have? The heat of the air is used to ignite the diesel sprayed in the form of mist by the fuel injector.
The power produced in a diesel engine is very high as compared with the petrol engine. The diesel engine is of four stroke type in which we have four strokes : Suction , compression, power and exhaust stroke. People use more of petrol engines but the power developed is more and the consumption of fuel is also less in diesel engines. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.
Skip to content. Table of Contents. How Jet Engine Works? Leave a Comment Cancel Reply Your email address will not be published. The petrol engine works on Otto cycle i. The diesel engine works on diesel cycle i. The air and petrol are mixed in the carburetor before they enter into the cylinder.
When injected into the combustion chamber, the Diesel oil undergoes spontaneous ignition. These engines work on the Diesel cycle, which consists of a relentless pressure process, a constant volume process, and two isentropic processes.
Apart from the sort of fuel used, the engines also are divided on the premise of plenty of things, like the presence of plug-in Petrol engines and a fuel injector in Diesel engines. We also know that lighter vehicles like motorcycles, scooters, and cars typically use petrol in their engines whereas Diesel is employed in much heavier machinery like tractors, trucks, and buses. Thus, the kinds of fuel used also play a significant role in defining the most important difference between Petrol and Diesel engines.
More differences between these types of engines are listed within the tabular column below. The main difference between diesel and petrol engines is that petrol engines use spark plugs to ignite the air-fuel mixture, while diesel engines rely solely on heavily compressed air.
As mentioned earlier, Rudolf Diesel found that the temperature of air could be made to increase high enough if it was heavily compressed. The temperature would rise so high to the point where it could cause the ignition of diesel fuel.
Therefore in diesel engines, the air in the cylinder would be very heavily compressed, typically to around 14 to 23 times its original volume.
In petrol engines, the compression ratio is generally much lower, because they rely more on the spark plug to begin the power phase. The compression ratio in petrol engines is typically only around 7 to 10, with high-performance vehicles having higher compression ratios of up to Skip to content.
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