18-07-2014, 11:56 AM
SUPERCHARGED DIESEL ENGINES
SUPERCHARGED DIESEL ENGINES.docx (Size: 1.92 MB / Downloads: 97)
ABSTRACT
A super-charger is an extra equipment mounted on main engine shaft (directly or using belt, chain drives) to increase the power and torque of engine.
Basically it’s an air compressor which sucks and compresses air at inlet by forced induction increasing the air density, temperature and pressure. Which finally improves power output. As we know more power means more fuel and to burn that fuel efficiently we need more oxygen. So, the supercharger does it.
These days the so called Super cars,Pickup trucksthey all use this technology to perform better with their same engine.
This seminar paper deals with its types, working, working parameters, its performance and its comparison with naturally aspirated engines in terms of performance, then to find out other ways increasing power and its comparison with supercharger. Let’s start!
Introduction
In 1860, brothers Philander and Francis Marion Roots, founders of Roots Blower Company of Connersville, Indiana, patented the design for an air mover, for use in blast furnaces and other industrial applications.
The world's first functional, actually tested [2] engine supercharger was made by Dugald Clerk, who used it for the first [3] two-stroke engine in 1878. Gottlieb Daimler received a German patent for supercharging an internal combustion engine in 1885. Louis Renault patented a centrifugal supercharger in France in 1902. An early supercharged race car was built by Lee Chadwick of Pottstown, Pennsylvania in 1908 which reportedly reached a speed of 100 mph (160 km/h).
The world's first series-produced cars [4] with superchargers were Mercedes 6/25/40 hp and Mercedes 10/40/65 hp. Both models were introduced in 1921 and had Roots superchargers. They were distinguished as "Kompressor" models, the origin of the Mercedes-Benz badging which continues today.
On March 24, 1878 Heinrich Krigar of Germany obtained patent #4121, patenting the first ever screw-type compressor. Later that same year on August 16 he obtained patent #7116 after modifying and improving his original designs. His designs show a two-lobe rotor assembly with each rotor having the same shape as the other. Although the design resembled the roots style compressor, the "screws" were clearly shown with 180 degrees of twist along their length. Unfortunately, the technology of the time was not sufficient to produce such a unit, and Heinrich made no further progress with the screw compressor. Nearly half a century later, in 1935, Alf Lysholm, who was working for Ljungstroms Angturbin AB (later known as Svenska Rotor Maskiner AB or SRM in 1951), patented a design with five female and four male rotors. He also patented the method for machining the compressor rotors.
MORE FUEL+MORE AIR=BIGGER EXPLOSION =GREATER HORSEPOWER
The power output of an engine depends upon the amount of air indicated per unit time, the degree of utilizationof this air and thermal efficiency of the engine. The amount of air inducted per unit time can be increased byincreasing the engine speed or by increasing the density of air intake. The method of increasing the inlet air density is called Supercharging. The increase in the amount of air inducted per unit time (increasing the density) by supercharging is obtained mainly to burn a greater amount of fuel in a given engine and thus increase its power. Supercharging can be done both for SI engines as well as CI engines
Dynamic compressor
It rely on engine speed. The acceleration of air it uses and converts kinetic energy to pressure energy (diffusing) slowing it down. So, it can give increasing boost with increasing engine speed.
So, a positive displacement type supercharger pushes air into an engine at a constant speed while dynamic one uses velocity to manipulate the pressure in the air.And in either case oxygen is compressed and delivered to the engine allowing more power to be gained from each explosion of the combustion chamber.
Commonly used types of superchargers
Roots Superchargers: The Roots supercharger is the oldest design. Philander and Francis Roots patented the design in 1860. In 1900,Gottleib Daimler included a Roots supercharger in a car engine.
As the meshing lobes spin, air trapped in the pockets between the lobes is carried between the fill side and the discharge side. Large quantities of air move into the intake manifold and "stack up" to create positive pressure.
For this reason, Roots superchargers are really nothing more than air blowers. Roots superchargers are usually large and sit on top of the engine. They are the least efficient supercharger for two reasons, they add moreweight to the vehicle and they move air in discrete bursts instead of in a smooth and continuous flow.
Drives used in supercharger
These are basic equipment used to transfer power from one shaft to another shaft. Here in supercharger it is used to transfer part of engine power to supercharger.
According to requirement there are several types of drives used to empower a supercharger. As:
>Mechanical
• Belt (V-belt, flat belt, toothed belt)
• Gear drive
• Chain drive
>Exhaust gas turbines
• Axial turbine
• Radial turbine
TURBO-SUPERCHARGERS OR TURBOCHARGERS
Turbochargers are a type of forced induction system whose function is same as that of Supercharger. They compress the air flowing into the engine.
A turbocharged engine produces more power overall than the same engine without the charging. This can significantly improve the power-to-weight ratio for the engine.
In order to achieve this boost, the turbocharger uses the exhaust flow from the engine to spin a turbine, which inturn spins an air pump. The turbine in the turbocharger spins at speeds of up to 150,000 RPM.
The turbocharger is bolted to the exhaust manifold of the engine. The exhaust from the cylinders spins the turbine, which works like a gas turbine engine.
Conclusion
• It derives 10-15% power from main engine and boosts engine power to almost 145% and torque 135%, which seems more sensible. So that means even if you have little less powered car it enables us to burn fuel more efficiently and gives cleaner exhaust.
• Itmakes them great for racing, towing heavy loads or just adding excitement to the typical driving experience.
• Despite their disadvantages, superchargers are still the most cost-effective way to increase horsepower.
• With the use of high octane premium-gradegas,it can be a miracle invention for speed junkies.
• To prevent knocking we can restrict them using only in diesel engines to perform better