Perkins Diesel Engine

Introduction

          Rudolf Diesel a German engineer was the person who has introduced the Diesel engine in 1890s.

 at that time   they used coal as fuel and this invention had done great revolution in mechanical scheme.

After 7 years he  invented a compression ignition engine which is run in kerosene.

          These engines are very effective and low cost in inner operation. Consume less fuel. So these

types of engines were very popular in that time. At that time and now also they are being use in big and

 heavy equipment shipping and railways. In these days most heavy duty busses, trucks, trains and autom

obiles also get poweusing these types of engines.

          Most commonly Diesel engines produce energy and heat by air compression ignition in fuel insid

 the cylinder. (Internal combustion engine).When the fuel (Diesel) coming in side of the cylinder there

 exists hot air and that air have enough heat to burn the fuel. Therefore it does not need spark plugs. It is

a very much advantage.Diesel  engines burn petroleum products like kerosene, jet fuels etc.

          Inside a diesel engine also there are cylinders and pistons. When the piston moves up and down

 inside the cylinder   the connecting rod which is connected to the piston is transmitting power to crank

shaft to rotate it.This is the basic operation inside the engine.

          Diesel engines are combust the fuel air mixture by compression. Therefore it should apply higher

load to the pistons and cylinders. So the inner and outer components should be having great strength to

withstand this much of higher forces and pressure. Due to these components are very strong the cost to

 make them also is high. Therefore the cost   of the engine is also very high.

Perkins engine is a 4 cylinder, 4 stroke diesel engine, that means the internal combustion happens in four strokes in side the cylinder.

          Here is the brief introduction about four strokes in Perkins diesel engine.

·                Intake stroke: - In this stroke cylinder sucks air by opening the inlet valve. In this stroke piston is

          in Bottom Dead Center.

·                Compression stroke: – In here intake valve closed and piston moves up to the cylinder. Within this

                                                strok air will compress highly and reached high temperature. At the

                                                finishing of this stroke fuel will be injected.

·                Combustion stroke: – Pressure and temperature will be increased due to the combustion happens.

                                              Therefore piston moves down.

·                Exhaust stroke: – At the beginning of this stroke piston in its bottom position. During this stroke                                           piston coming up and outlet valve will open simultaneously. So the exhaust

                                       gasses can move from the cylinder.

check this youtube video.

 http://www.youtube.com/watch?v=qDG6hwpou80

   

 Perkins Diesel Engine

Inside the Four cylinders four stroke Engine With all four strokes..

                                                         

Theory

Basic Diesel Cycle

·                Process a-b : Isentropic compression

·                Process b-c:  Reversible constant pressure heating

·                Process c-d : Isentropic expansion

·                Process d-a : Reversible constant volume cooling

By this experiment we are trying to get some knowledge about Perkins diesel engine with its design and operations and the performance in several circumstances such as fuel consumption ,efficiency etc.

Useful Notations;

         

          V         Volume

          T         Temperature

          Q         Heat

          γ          Cp / Cv

          Cp       Specific heat capacity under constant pressure

         Cv        Specific heat capacity under constant volume

          α          Cut-off ratio = V3 / V2

          r           Compression ratio = V1 / V2

U         Internal Energy

                 η= Net work / Work in

According to the 1^st law of thermodynamics,

∆U = ∆Q - ∆W

∆U=0, therefore

∆Q = ∆W

Net work  =  net heat =  Q(bc) + Q(da)

Work in  =  heat in  =  Q(bc)

η=Q(bc)  + Q(da) / Q (bc)

η=1 + [Q(da) / Q (bc)]

Q(bc) = Cp (Tc - Tb)

Q(da) = Cv (Ta - Td)

Standard notation

BP                = Brake power

FP                = Friction power

IP                 = Internal power

K (constant) = 4500

W                 = load (lbs)

N                  = Speed (rpm)

SFC              = Specific fuel consumption

BPMF          = Brake power mean efficiency                                                                               

BMEP         = Brake mean effective pressure

h                   = Manometer water head (inch of water)

T                  = temperature at the orifice (K)

H                 = Atmospheric pressure (inch of Hg)

d                  = Orifice diameter

D                 = Cylinder bore

L                 = Stroke

           

BP= W.N/K   (kW)

IP = BP +  FP

BMEP = BP / (Π / 4. D^2. L. (N / 2) (4 / 60) )

Volume inhaled = (4.193 / 35.22) D^2. ( h.T / H) ^ 0.5        (m^3 / min)

Swept volume = 4. (Π / 4 D^2 L). N /2       (m^3 / min)

Performance parameters

SFC = (Fuel consumption / BP). 3600    (kg / kWh)

Mechanical efficiency = BP / IP

Brake thermal efficiency = overall efficiency = BP / Rate of heat input by the fuel

Volumetric efficiency = volume inhaled / Swept volume

Indicated thermal efficiency = IP / Rate of heat input

  Calculation of frictional power

          This can be observed from the graph of fuel consumption vs. brake power. We have to get thefuel consumption in zero power, because when frictional power will be available only when the brake power is zero in the engine. So the frictional power will equal to internal power.

                                  Internal power = Frictional power + Brake power

                                  Brake power = 0

                                  Therefore,

                                  Internal power = Frictional power

                      Frictional power = (Fuel consumption where the brake power is zero) * Calorific value  

Procedure

1.              Open the inlet water supply valve fully and the outlet valve slightly of the dynamometer.

a.                                      i.e. Dynamometer: Instruments measuring energy expended.

2.              Make sure all the valves in the piping between the source of the water supply and the dynamometer inlet are fully open.

3.              The engine may now be started.

4.              Loads may be regulated by opening the sluice gates by means of the hand-wheel and simultaneously operating the engine throttle, until the desired load and speed are obtained.

5.              Adjust the outlet valve to pass sufficient water to keep the temperature at a reasonable figure.

6.              A hand wheel is provided on top of the balance frame to adjust the height of the balance arm. Make sure that this wheel is always set to the horizontal position when taking B.HP readings.

Equipment

·                Perkins diesel engine.

·                4 cylinder 4 stroke engine

·                coolant  :- water cooled

·                Engine is coupled with a Henan-Froude water cooled dynamometer, So the torque,  speed in rpm,

·                 can be measured.

·                Measuring air mass flow rate: - an orifice plate fitted to an air reservoir                                                                                                          this is attached to the inlet manifold of the engine.

·                Measuring pressure across the orifice: - Using an inclined water manometer.

Engine parameters

·                Orifice diameter        = 2.05 inches

·                Length of the stroke  = 3.05 inches

·                Cylinder bore            = 3 inches

·                Speed of rotation       = 1500 rpm

Fuel parameters

·                Specific heat capacity of the fuel   = 1.08kg / kJ.K

·                Density of the fuel                          = 880 kg /m^3

·                Calorific value of fuel                     = 44290 kJ/kg

Discussion

     Perkins engine is a diesel engine which is working according to the diesel cycle. Because of these

advantages of the diesel cycle we can convert this Perkins engine to be very effective engine which

having more efficiency, high fuel consumption, smoothness etc. we can enhance high performances

 using Perkins engine than gasoline or other fuel engines by internal combustion.

          There were many differences between traditional gasoline engine and Perkins engine. We can categorize this are basic two categories.

·                Ignition method

                      Gasoline :- Spark Ignition

                      Diesel :- Compression Ignition

·                Fuel Injection

                      Gasoline :- port fuel injection.

                      Diesel :- Direct fuel injection.

Advantages and Disadvantages of Perkins Diesel Engine.

Advantages:-

·         This engine has high expansion ratio and reached high temperature in combustion. Due to these       reasons Diesel engine has mare efficiency and greater fuel efficiency than other engines. Gasoline engines basically having 20-25% efficiency while Diesel engines have efficiency more than 30%.

·         They are no high powered electrical ignition system to burn fuel. So it is not more harmful to environment because there are no use of carbon coils, wires, unwanted metals and also it eliminates a source of radio frequency emissions which are connect with communication and navigation.

·         For a given load to the engine, Diesel engine remains its efficiency constant while at that load gasoline engine reduces its efficiency to put more output powers.

·         Life time of the Diesel engine is approximately twice a gasoline engine Due to the diesel engine are made by high strength metal parts than traditional gasoline engines.

·         Can deliver the generated power continuously than the gasoline engine.

·         High compression ratio. Volume of the cylinder when the piston at BDC to the volume of the cylinder when the piston at the TDC.

• When higher Compression ratios,

·         The temperature of air is higher at the end of the compression stroke,

·         Having higher thermal efficiency,

·         Greater fuel economics,

·         Generate high temperatures required for auto ignition.

·         Also Diesel engines actually the fuel diesel is more safer than other fuel like petrol. Though diesel get fired in normal air with the support of some fire pulse, it does not explore in severe manner like petrol. It would be great advantage for the industry.

·         And the law vapor pressure of diesel gives more advantage for marine applications. So the fuel air       mixtures which is accumulation of explosive is extremely hazard and for while diesel engines are immune to vapor locking.

·         Compression Ratio of Diesel Engine to Gasoline Engine

• Spark ignition compression ratio         8:1 to 12:1
• Compression ignition ratio      14:1 to 25:1

·         Compression ratio of Diesel engine

• The Compression ratio indicates that in how much of strength the cylinder can compromise it’s contain to outside. As the figure indicates the engine which is used otto cycle is having a smaller compression ratio than the diesel engine. So the engine can work with high efficiency and it also very important for industrial     and other applications.

Disadvantages:-

·         Main disadvantage is that the Diesel engine emits Carbon Monoxide with its exhaust gas. This affects the surrounding and our environment. But this is very small by comparing the gasoline  engine. Because, gasoline engine emits unburned fuel parts and several other chemical components which are more harmful to surrounding as well as human beans.

·         Another disadvantage is that in this diesel engine fuel injected before power stroke. If there is nit sufficient air to get that fuel so fuel will not burned 100% correctly. So that incomplete combustion make exhaust gas black in color and very thick and this unburned fuel will reaches outer environment and it is not very safer.

·         Other thing is those engines are very expensive than other engine types. Because it cost highly in manufacturing and maintenance. Diesel engines are very echo friendly than other engines and they are having high technology to reduce the various components in exhaust system. So this increases its price than other models.

·         When the engine working it emits high noise. This is called as Diesel knock and this noise caused because the diesel combustion process and sudden ignitions.

·         Diesel engines have long stroke lengths to achieve higher compression ratios. So the connecting rods and crankshaft are very heavy and the required power to transmit power is very high.

BALANCING OF ROTATING MASS

Introduction

If the mass center of a component of mass 'm' is rotating at an angular velocity   at a

distance 'r' from the axis of rotation, then the component is subjected to force of mr2

The 'out of balance' forces increase bearing loads, and introduce stresses in the rotor and

framework of a machine. These so called 'inertial forces' may introduce dangerous

vibrations, structural failure or unacceptable noise, and may limit the operating speed

range of a machine. The magnitude of these forces may be reduced or eliminated in the

design stage by 'balancing' the effects of the various mass elements of the device.

Additionally, extra balance masses may deliberately added to a rotating system in order

to cancel out the residual design imbalance.

This experiment involves the balancing of a number of known out of balance masses on a

shaft.

There are two types of balancing.

Static and Dynamic Balance

So far we have considered the case of a wheel, which approximates to a simple disc, having all its mass in or near one plane. If this is statically balanced in the way described, it will run at any speed without vibration. But in a rotating body having a fairly considerable axial length, such as a cylinder, it is important that any local unbalanced mass should be balanced out by a mass as nearly in the same cross plane as possible.

The static method of balancing, in this case, is not reliable because it gives no indication of the position of the bias in relation to axial length. Thus the cylindrical rotor, an armature shaft for instance, shown in Fig. 2, may be heavy at the point A, as indicated by a static balancing test. If this unbalanced mass is counteracted by a weight applied at the point B, the rotor will appear to be in correct balance; but when running at high speed, the effect of the two unbalanced masses will cause local reactions R-R which tend to rock the shaft along its length, or in other words to set up a "couple." In practice, the effect of this may be worse than that of a single unbalanced force which tends to vibrate the structure bodily, and it is often much more difficult to detect and correct.

The method usually employed for dynamic balancing is to mount the shaft in bearings on a frame which is resiliently mounted, usually by some form of spring suspension, so that it is capable of being displaced in any plane by the effect of unbalanced forces. Means are provided for locking the frame while the shaft is run up to a fair speed by any convenient means, after which it is released and allowed to vibrate or oscillate under the effect of the unbalanced forces. In modern dynamic balancing machines, indicating or recording devices are provided to show the position and extent of the unbalanced masses. While it would not be impossible to construct a simple dynamic balancing rig in the home workshop, most of the problems involved in small machines can be dealt with by careful consideration of design, and accuracy in construction of moving parts. It may be mentioned that even the balancing machine, unless of very complex design, may leave certain important considerations out of account.

For instance, suppose that a rotor having an unbalanced mass at J (Fig. 3A) is balanced by adding two smaller masses at the points K, L. The rotor is then in correct dynamic balance, and in the case of a fairly rigid component, such as an armature, it will be perfectly satisfactory in practice. But suppose the same principle is applied to a non-rigid component, such as a crankshaft; in this case, the cancelling masses, being in different planes, exert bending stresses on the shaft, and the latter may be deflected, thereby altering the moment of the masses and putting the system out of balance (Fig. 3B).

This is only one of the many pitfalls in practical balancing, which cause the designer many headaches, and are rarely capable of being dealt with by theoretical calculation. Another example occurs in the case of a rotating body which for practical reasons cannot be made symmetrical in shape, though the moments of mass are calculated and counterweights added where necessary to cancel out and give correct balance as in Fig. 4. When running at high speed, however, the effect of centrifugal forc,e causes the flywheel to distort, and thereby displace the masses to a varying extent, thereby unbalancing them. In case readers think this is an unlikely eventuality, I may say that I once worked on a certain type of flywheel magneto which gave a great deal of trouble through this cause, though dynamic balancing tests gave no indication of the source of error.

Balance weights, whatever their type or purpose, should always be located as close to the plane of the unbalanced mass as possible. Thus, in the case of the crankshaft shown in Fig. 3B, it would be better to attach the counterweights to the crank webs than at the points indicated. The practice of fitting balance weights to external flywheels, therefore, is one that cannot be commended; in the case of an overhung crankshaft, any bias in the flywheel would set up a violent rocking couple. Flywheels should always be at least in static balance, and if of any great width, dynamic balancing is desirable. An exception is made in the case of internal flywheels, as in motor-cycle engines, which are close to the crank pins, and usually form the crank webs.

DISCUSSION

Applications use rotating balancing to maintain there characters properly

1.       Engine crank shaft

2.       Automobile wheel

3.       Grinding wheels

4.       Steam turbines and runners

5.       Compressors

6.       Washing machines

7.       Air craft propellers

Types of Balancing

There are two forms of balancing: static and dynamic.

Static balancing is done by holding the component at its axis, then compensating (by removal or addition of mass) for the "heavy" side of the component. During Static balancing, the component is not rotating, hence "static".  Static balancing is typically done on "flat" parts, or parts that have a large diameter to axial length ratio (pancake like parts, such as fans, pulleys, wheels). 

Dynamic balancing is done on parts that are long compared to their diameters such as rotor assemblies.  These parts require balancing to be done in two planes since the actual imbalance will intersect the center line/axis.  Unless both ends of the part are balanced, mass imbalance will continue to exist.  Rotor assemblies that MCE manufactures are balanced dynamically (in two planes).

Balancing can be achieved by the addition or removal of mass in certain locations.  MCE only provides balancing by use of mass removal which is achieved by abrasive material removal or by drilling/machining.  Note that when designing your part, take into account that material removal will be required and allow for extra material such as a balancing ring or thicker flanges than required by design to achieve mechanical structural integrity. 

Why we need Balancing of rotating Masses

1. It will reduce the unwanted vibrations

2. it reduce the energy waste so it will increase the efficiency of the machine.

3. Vibrating parts wear quickly . so balancing is so important to have a long life time for the shafts.

4. When shaft is unbalanced it bends when it’s rotating so it s subjected to compression and expansion  alternatively so it fails easily.

5.Bearing wear due to large forces on them