Ebook A field guide to automotive technology: Part 2
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Ebook A field guide to automotive technology: Part 2
UNDER THE HOODWHAT NOISY BEAST IS IT that resides beneath the hood of your car? It breathes air, consumes petroleum, and belches particulate-laden exh Ebook A field guide to automotive technology: Part 2 haust responsible for all manner of undesirable environmental and health effects.For all its negative attributes, few machines have gained such widespread acceptance. Anywhere you go in the world people are using gasoline engines to move themselves and their goods, to move water, and to make electri Ebook A field guide to automotive technology: Part 2 city.INTERNAL COMBUSTION ENGINESGasoline engines can convert about 25 to 30 percent of the energy in burning fuel to moving the vehicle. Diesel engineEbook A field guide to automotive technology: Part 2
s operate a bit more efficiently at up to 40 percent. The remaining or wasted energy is lost as heat. Yet even at these low ratings, internal combustiUNDER THE HOODWHAT NOISY BEAST IS IT that resides beneath the hood of your car? It breathes air, consumes petroleum, and belches particulate-laden exh Ebook A field guide to automotive technology: Part 2 cylinders. In steam engines, the combustion occurs outside the engine in a separate fire box.Air and gasoline are squirted into the cylinder in a ratio of about 15:1. That is, 15 parts of air mix with one part of gasoline. This mixture is compressed by a piston moving upward in the cylinder. At just Ebook A field guide to automotive technology: Part 2 the right moment in the cycle, a spark plug fires and ignites the mixture.117The explosion drives the piston downward, and as it moves it rotates theEbook A field guide to automotive technology: Part 2
crankshaft. One cylinder operating a crankshaft makes for a roughoperating engine so usually cars have at least four cylinders. The additional cylindUNDER THE HOODWHAT NOISY BEAST IS IT that resides beneath the hood of your car? It breathes air, consumes petroleum, and belches particulate-laden exh Ebook A field guide to automotive technology: Part 2 cylinder (overhead valves) let air and fuel into the cylinder as the piston moves downward. They close before the piston begins its upward stroke, other valves open to let out the exhaust gases resulting from the combustion. These valves may open and close 50 times each second. Strong springs retur Ebook A field guide to automotive technology: Part 2 n the valves after being lifted by the cams.This describes how most gasoline engines work. Most use this Otto cycle, named for its inventor, NikolausEbook A field guide to automotive technology: Part 2
Otto. A more recent variation of the Otto cycle was invented by Ralph Miller and is called the Miller cycle.Miller cycle engines have superchargers thUNDER THE HOODWHAT NOISY BEAST IS IT that resides beneath the hood of your car? It breathes air, consumes petroleum, and belches particulate-laden exh Ebook A field guide to automotive technology: Part 2 out 20 percent of the compression cycle. During this period, the piston doesn’t have to use as much energy to compress the fuel/air mixture in the cylinder, so each cylinder generates nearly the same energy but expends less energy getting it. Further, the supercharged air is cooled (by a device call Ebook A field guide to automotive technology: Part 2 ed an intercooler). The cooler air allows the timing of the spark to be delayed and the resulting compression to be higher. These changes provide anotEbook A field guide to automotive technology: Part 2
her boost in engine efficiency. Mazda uses Miller cycle engines in some of its cars.A diesel engine works pretty much the same way as an Otto cycle gaUNDER THE HOODWHAT NOISY BEAST IS IT that resides beneath the hood of your car? It breathes air, consumes petroleum, and belches particulate-laden exh Ebook A field guide to automotive technology: Part 2 on compressing the fuel-air mixture causes ignition. Air enters the diesel engine from a valve and is compressed. In a diesel engine the air is compressed up to twice as much as in a gasoline engine. When the piston is at the top of its stroke and the air inside the cylinder is about 1,500° F, the f Ebook A field guide to automotive technology: Part 2 uel is sprayed into the cylinder.118 A FIELD GUIDE TO AUTOMOTIVE TECHNOLOGYBang! The piston is driven downward powering the crankshaft. Although dieseEbook A field guide to automotive technology: Part 2
l engines don’t have spark plugs, some have glow plugs to warm the cylinders on a cold start.Of course, engineers could not let gasoline and diesel enUNDER THE HOODWHAT NOISY BEAST IS IT that resides beneath the hood of your car? It breathes air, consumes petroleum, and belches particulate-laden exh Ebook A field guide to automotive technology: Part 2 otors has a hemispherical or domed combustion chamber rather than a flat head over the chamber. The shape improves the mixing of fuel with air to get more kick from each explosion. Million dollar ad budgets aside, most gasoline engines today have hemi-like combustion chambers that differ little from Ebook A field guide to automotive technology: Part 2 the vaulted Hemi.The rotary or Wankel engine has rotary pistons that spin around in a circle. Rather than the violent vibrations of the reciprocatingEbook A field guide to automotive technology: Part 2
piston motion in other engines (up, stop, down, stop), the rotary pistons spin smoothly with no stops throughout the combustion cycle. The rotor spinUNDER THE HOODWHAT NOISY BEAST IS IT that resides beneath the hood of your car? It breathes air, consumes petroleum, and belches particulate-laden exh Ebook A field guide to automotive technology: Part 2 e for every two strokes of a traditional (four-cycle) combustion engine. To ensure complete combustion rotary engines typically have two spark plugs for each rotor. Mazda has offered several models.ELECTRIC MOTORSBefore internal combustion engines were popular in vehicles, people were driving electr Ebook A field guide to automotive technology: Part 2 ic cars. Now, a century later, we are looking again at the advantages of electric cars.Unlike most cars that burn gasoline or diesel fuel to generateEbook A field guide to automotive technology: Part 2
heat and motion, electric cars use energy stored in batteries to power motors. The chemical reaction of batteries is reversible so batteries can be chUNDER THE HOODWHAT NOISY BEAST IS IT that resides beneath the hood of your car? It breathes air, consumes petroleum, and belches particulate-laden exh Ebook A field guide to automotive technology: Part 2 at the site of the electric generator, where hopefully they can be controlled more effectively. Electric cars are less expensive to operate, but their initial cost, largely the cost of the batteries, discourages many buyers.UNDER THE HOOD 119Manufacturers are using a variety of battery types in elec Ebook A field guide to automotive technology: Part 2 trics. Some use the lead-acid batteries that gasoline engine cars use, but electrics require many more of them. These are very heavy but inexpensive —Ebook A field guide to automotive technology: Part 2
at least in relation to the alternatives. More practical are nickel metal hydride, but they cost much more. They can increase the car’s range, and theUNDER THE HOODWHAT NOISY BEAST IS IT that resides beneath the hood of your car? It breathes air, consumes petroleum, and belches particulate-laden exh Ebook A field guide to automotive technology: Part 2 control system that interprets the position of the pedal and increases or decreases the voltage carried to the motor. The motor can be either AC or DC. An AC system requires the conversion of the DC power from the batteries into AC current to run the motor. DC motors are often the same ones used in Ebook A field guide to automotive technology: Part 2 forklifts.Electric cars can recapture some of the car’s kinetic energy to generate electricity. When the car is slowing down, the car’s momentum keepsEbook A field guide to automotive technology: Part 2
it moving and the motor turning. The motor then acts as a generator, able to recharge the battery.HYBRID MOTORSHybrid cars use electric motors but alUNDER THE HOODWHAT NOISY BEAST IS IT that resides beneath the hood of your car? It breathes air, consumes petroleum, and belches particulate-laden exh Ebook A field guide to automotive technology: Part 2 ators and a gasoline engine. A motor-generator can operate either as a motor, when electric power is supplied to it, or as a generator of electricity, when mechanical power is applied.One of the two motor-generators is mounted on the front transaxle. At slow speeds, nickel-metal hydride batteries pr Ebook A field guide to automotive technology: Part 2 ovide power to the motor generator on the drive shaft. At higher speeds, about 40 mph, the gasoline engine kicks in to add power to the wheels. The enEbook A field guide to automotive technology: Part 2
gine also turns the other motor-generator to generate electricity that can either recharge the batteries or provide power to the motor-generator on thUNDER THE HOODWHAT NOISY BEAST IS IT that resides beneath the hood of your car? It breathes air, consumes petroleum, and belches particulate-laden exh Ebook A field guide to automotive technology: Part 2 as the starter. Initial power is provided by the batteries.120 A FIELD GUIDE TO AUTOMOTIVE TECHNOLOGYAs the car accelerates, the gasoline engine and the axle-mounted motor generator provide the power. When the engine is producing more power than needed to drive the car, it generates electrical powe Ebook A field guide to automotive technology: Part 2 r through the second motor-generator. When the engine needs help getting the car up a steep hill, the motor-generator on the axle can assist. It drawsEbook A field guide to automotive technology: Part 2
power either from the battery or from its partner motorgenerator. Going down a steep hill the car can capture some of the potential energy through thUNDER THE HOODWHAT NOISY BEAST IS IT that resides beneath the hood of your car? It breathes air, consumes petroleum, and belches particulate-laden exh Ebook A field guide to automotive technology: Part 2 ite polarity, so the motor runs in reverse. The gasoline engine isn’t used in backing up.Selecting the right combination of battery, motor-generators, and engine is the job of a computer. Drivers don’t control the engine directly, they make inputs into the computer that controls the motorgenerators Ebook A field guide to automotive technology: Part 2 and engine. If the computer quits, so does the car. But the advantage is greatly increased fuel efficiency and quieter operation.From a car engine staEbook A field guide to automotive technology: Part 2
ndpoint, these are exciting times. A wide variety of engine technologies are vying for marketplace approval and it’s impossible to say with certaintyGọi ngay
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