Automobile Engines
Engine Automotive production down the ages has required a wide range of  energy-conversion
systems. These include electric, steam, solar, turbine, rotary, and
different types of piston-type internal combustion engines. The
reciprocating-piston internal -combustion system, operating on a
four-stroke cycle, has been the most successful for automobiles, while
diesel engines are widely used for trucks and buses.The gasoline engine was originally selected for the automobile due to its flexibility over a wide range of speeds. Also, the power developed for a given weight engine was reasonable; it could be produced by economical mass-production methods; and it used a readily available, moderately priced fuel--gasoline. Reliability, compact size, and range of operation later became important factors. In today’s world, there has been a growing emphasis on the pollution producing features of automotive power systems. This has created new interest in alternate power sources and internal-combustion engine refinements that were not economically feasible in prior years. Although a few limited-production battery-powered electric vehicles have appeared from time to time, they have not proved to be competitive owing to costs and operating characteristics. However, the gasoline engine, with its new emission-control devices to improve emission performance, has not yet been challenged significantly. The first half of the twentieth century saw a trend to increase engine horsepower, particularly in the American models. Design changes incorporated all known methods of raising engine capacity, including increasing the pressure in the cylinders to improve efficiency, increasing the size of the engine, and increasing the speed at which power is generated. The higher forces and pressures created by these changes created engine vibration and size problems that led to stiffer, more compact engines with V and opposed cylinder layouts replacing longer straight-line arrangements. In passenger cars, V-8 layouts were adopted for all piston displacements greater than 250 cubic inches (4 litres). Smaller cars brought about a return a to smaller engines, the four- and six-cylinder designs rated as low as 80 horsepower, compared with the standard-size V-8 of large cylinder bore and relatively short piston stroke with horsepower ratings in the range from 250 to 350. The automobile engines from Europe had a bigger range, varying from 1to12 cylinders with corresponding differences in overall size, weight, piston displacement, and cylinder bores. Four cylinders and horsepower ratings from 19 to 120 was followed in a majority of the models. Several three-cylinder, two-stroke-cycle models were built while most engines had straight or in-line cylinders. There were several V-type models and horizontally opposed two- and four-cylinder makes too. Overhead camshafts were frequently employed. The smaller engines were commonly air-cooled and located at the rear of the vehicle; compression ratios were relatively low. The 1970s and '80s saw an increased interest in improved fuel economy which brought in a return to smaller V-6 and four-cylinder layouts, with as many as five valves per cylinder to improve efficiency. Internal
-Combustion engine
DIESEL ENGINES are mechanical devices that use controlled explosions (combustions) of diesel and air to rotate wheels. The reciprocating (back and forth) engine explodes the mixture (of diesel fuel + air) in a cylinder that forces the contained piston to move. This movement of the piston is transmitted (via the connecting rod) to a rotating device (crankshaft shown as a simple red disc) which is ultimately connected to the wheels (via gears, usually). The diesel engine is similar to the 4-stroke petrol engine but it uses the heat generated by the compression of air to ignite the explosion. To do this it compresses the air more than a petrol engine. The diesel engine therefore does not require a sparking plug. The diesel fuel (which is heavier and contains longer chain hydrocarbons) is injected directly into the cylinder when the air has been greatly heated by the compression stroke. DIESEL ENGINE: FOUR STROKES ANIMATED: the animation begins with the piston at the top of the cylinder. The piston moves down and the air enters the cylinder. This is illustrated as a pale green cone of air that vanishes into the green inlet tube. Notice how the cylinder fills with this air. The piston then moves upwards and greatly compresses the air. Diesel fuel is injected at this point directly into the heated compressed air. This is illustrated as a rotating purple spiral at the top of the engine. The compressed mixture explodes. This explosion drives the piston downwards in what is called the power stroke. The piston then returns to the top of the cylinder in the exhaust stroke and drives the exhaust gases out of the engine. The exhaust gases can be seen leaving the (orange-yellow) exhaust tube as a cone of pale orange. DIESEL ELECTRIC HYBRID VEHICLES: contain both a diesel engine and an electric motor. Each contributes to powering the vehicle depending on conditions. Energy is stored in the fuel tank (as diesel fuel) and in batteries (cells). Hybrid vehicles are attracting great attention because they use less fuel (petrol / gasoline/ diesel fuel) than conventional vehicles. With the increasing price of oil and worry about carbon dioxide emissions hybrid cars (and other hybrid vehicles) are increasing in popularity. How Engine Works  |
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Fuel
combustion takes place in a confined space, and produces expanding gases
that are used to provide mechanical power. The four-stroke reciprocating
engine that is used in automobiles is the most common
internal-combustion engine. In this mechanism, mechanical power is
supplied by a piston that is fitted inside a cylinder. On a downstroke
of the piston, the first stroke, fuel that has been mixed with air (by
fuel injection or using a carburetor) enters the cylinder through an
intake valve; the piston moves up to compress the mixture at the second
stroke. At ignition, the third stroke, a spark from a spark plug ignites
the mixture, forcing the piston down; in the exhaust stroke, an exhaust
valve opens to vent the burned gas as the piston moves up. The piston is
connected to a crankshaft by means of a rod. The reciprocating (up and
down) movements of the piston rotate the crankshaft, which is connected
by gearing to the drive wheels of the automobile. The ignition spark is
provided by an electrical system whose power comes from a battery. This
also supplies power to the starting system, which is a small electric
motor that turns the crankshaft until the engine takes over. Water
circulating around the cylinders cool the engine, and lubrication occurs
motor oil that is driven around the moving engine parts by an oil pump.
Small vehicles like lawn mowers and motorcycles use the two-stroke
engine, which combines intake and compression in the first stroke and
power and exhaust in the second.
MECHANICS: DIESEL ENGINE: This animation explains how a diesel
engine works. It shows a highly simplified diesel 4-stroke engine
cycling through the intake, compression, power and exhaust strokes.
