This document summarizes a study of a diesel engine power plant. It describes how a diesel engine is used as the prime mover to generate mechanical energy through combustion, which is then converted to electrical energy by an alternator. Diesel power plants are efficient and economical for small-scale power generation, especially where other fuel sources are not available or load factors are high. The document outlines the objectives, components, operating principles, applications and types of diesel engines used in diesel power plants.

1. Experiment No. 02
Experiment Name: Study of Diesel Engine Power Plant
Introduction:
In a diesel engine power Plant, diesel engine is used as the prime mover. The diesel burns
inside the engine and the products of this combustion act as the working fluid to produce
mechanical energy. The diesel engine drives alternator which converts mechanical energy
into electrical energy. As the generation cost is considerable due to high price of diesel,
therefore, such power stations are only used to produce small power.
The diesel plants are more efficient than any other heat engines of comparable size. It is
cheap in first cost. It can be started quickly and brought into the service. It can burn a fairly
wide range of fuels. Its manufacturing periods are short and, therefore, a diesel station may be
rapidly extended to keep pace with load growth by adding generating units of suitable sizes.
The diesel units used for electric generation are more reliable and long-lived piece of
equipment compared with other types of plants.
The diesel engine has provided the most economic means of generating electricity on small
scale particularly where there is no convenient site for micro-hydro plants and cheap fuels are
not available and load factors are considerably large
Objective:
At the end of this workshop, you will gain valuable know-how related to diesel generating
plants on:
Combustion processes and engine operation principles
Understand about diesel engine power plant,
Explain fuel injection system and its functions, and
Describe various injection schemes.

2. Types and applications
Generator principles and construction
Fuel and lube oil requirements
Plant layout requirements for single and multiple units
Testing and commissioning procedures
• Plant performance troubleshooting techniques
• Good maintenance practices
• Mechanical Engineers
• Instrumentation and Control Engineers
• Electrical Engineers
• Project Engineers
• Maintenance Engineers
• Power System Protection and Control Engineers
• Building Service Designers
• Systems Planners and Managers
• Electrical and Instrumentation Technicians
Practical Operation,
Maintenance & Testing of
For Engineers & Technicians

3. Schematic Diagramof DieselEngine PowerPlant:
Field of use(Applications):
The diesel electric power-plants are chiefly used in the fields mentioned below.

4. 1. Peak load plant: The diesel plants are used in combination with thermal or hydro-plants
as peak load plants. This plant is particularly preferable as peak load plant as it can be started
quickly and it has no standby losses as in the case of thermal plants where boilers always
must be kept hot.
2. Mobile plants: Mobile diesel plants mounted on skids or trailers can be used for
temporary or emergency purposes such as for supplying power to large civil engineering
works for supplementing electricity supply systems that are temporarily short of power.
3. Stand-by Units: This can be used as a standby unit to supply part load when required. For
example, this can be used with hydro-plant as stand-by unit. If the water available is not
sufficient due to reduced rainfall, diesel stations supply power in parallel with hydro-station.
The use is made temporarily till the water is available to take the full load.
4. Emergency plant: The plants used for emergency purposes are to standby units, normally
idle but are used where power interruption would mean financial loss or danger in key
industrial processes, tunnel lighting and operating rooms of hospitals. They are also used for
telecommunication and water supply under emergency conditions.
5. Nursery station: When the diesel plant is used to supply the power to a small town in the
absence of main grid and which can be moved to another area which needs power on a small
scale when the main grid is available is known as "Nursery Station”. The main grid cannot
extend to every corner of the country till there are enough loads. Many times the extension of
grid is not possible due to the constructional difficulties as in Assam. Diesel unit of small
capacity can be installed to supply the load to a small town during the process of
development and it can be removed to another required place till the main grid for tapping the
power is available.
6. Starting stations: The diesel units are used to run the auxiliaries for starting the large
steam plants.
7. Central stations: This can be used as central station where the capacity required is small
(5 to10 MW). The limit is generally decided by the cost of the plant and local conditions
regarding the availability of fuel and water, space requirements and non-availability of the
grid.
Types of dieselengines used for diesel powerplants:
The diesels engines are generally used in diesel engine power plant are as following
1. Four-stroke Engines and
2. Two-stroke Engines.
The four-stroke engine develops power after every two revolutions of crank shaft.
Whereas
Two-stroke engine develops power with each revolution of crank shaft. Generally

5. Two-stroke engines are favored for diesel power plants for the advantages described
later.
Duel Fuel Engines: In duel fuel engines, gas and oil both are used as fuels for the engines.
The gas is used as main fuel and oil is used as helper for ignition.
In the duel fuel engine, the air and gas are taken in during suction stroke. The pressure of the
mixture is increased during compression stroke. Near the end of the compression stroke, the
pilot oil is injected into the cylinder. The compression heat first ignites the pilot oil and then
gas mixture. The further actions of the engine are similar to the diesel engine. The air-gas
ratio is comparatively higher in duel fuel engines compared with gas engines.
There is keen interest in the diesel power plants to use the duel fuel engines for better
economy and proper use of available gaseous fuels in the country. The gas may be a waste
product as in the case of sewage treatment installations or oil fields where the economic
advantage is self-evident. With the wider availability of natural gas, the duel fuel engines
may become an attractive means of utilizing gas as fuel at off-peak tariffs for the generation
of electrical energy.
Operating principle of DieselEngine:
A diesel engine has used diesel cycle principle to operate the four sequential steps. The 4
steps are done in 2 stokes or 4 stokes of piston. A stroke is the distance from top dead center
to bottom dead center. The piston travels down for one stroke on intake, up for compression,
down for power, and back up for exhaust. The four stoke of a diesel engine are given below:
Intake Stoke: the inlet valve opens and the piston starts to move down from top dead
center. Air enters the cylinder through the inlet port. When the piston reaches bottom dead
center, the cylinder is full of air. The inlet valve closes.
Compression Stroke: The compression stroke begins with the piston at bottom dead center
and rising up to compress the fuel and air mixture. Since both the intake and
exhaust valves are closed, there is no escape for the fuel and air mixture, and it is
compressed to a fraction of its original volume. At this point, the fuel sprayed in a nice
pattern and ignited automatically.
Power stoke: in this stoke both valves stay closed as the piston rises. Just before it reaches
top dead center, an injector sprays fuel into the chamber. It mixes with the very hot
compressed air and ignites. Combustion occurs, the temperature rises much higher and the
gases expand and force the piston down in a power stroke. The piston reaches bottom dead
center, the exhaust valve opens.
Exhaust Stoke: With the exhaust valve open and inlet valve closed, the piston moves up,
forcing exhaust gases out of the exhaust port. The piston reaches top dead center, the exhaust
valve closes, the inlet valve opens and the cycle starts again.

6. Fig
Essentialelementof diesel powerplant(Short description of diesel
components:
1. Diesel engine:
This is the key element for a diesel power plant. It is also called compression ignition engines
as they are called are generally classified as two stroke engine and four stroke engines. In
diesel engine, air admitted into the cylinder is compressed, the compression ratio being 12 to
20. At the end of compression stroke, fuel is injected. It burns and the burning gases expand
and do work on the position. The engine is directly coupled to the generator. The gases are
then exhausted from the cylinder to atmosphere.
Figure: Diesel Engine
2. Air-filter and supercharger: The function of the air filter is to remove the dust from the
air which is taken by the engine.

7. 3. Supercharger: The function of the supercharger is to increase the pressure of the air
supplied to the engine to increase the power of the engine. The superchargers are generally
driven by the engines.
Engine Auxiliary Systems of Diesel Power Plant:
Engine starting system:
This includes air compressor and starting air tank. The function of this system is to start the
engine from cold supplying compressed air.
Fuel system:
Pump draws diesel from storage tank and supplies it to the small day tank through the filter.
Day tank supplies the daily fuel need of engine. The day tan is usually placed high so that
diesel flows to engine under gravity.
Diesel is again filtered before being injected into the engine by the fuel injection pump. The
fuel is supplied to the engine according to the load on the plant.
Air intake system:
Air filters are used to remove dust from the incoming air. Air filters may be dry type, which
is made up of felt, wool or cloth. In oil bath type filters, the sir is swept over a bath of oil so

8. that dust particles get coated.
Exhaust system:
This system leads the engine exhaust gas outside the building and discharges it into
atmosphere. A silencer is usually incorporated in the system to reduce the noise level.
The exhaust system of a diesel engine performs three functions. First, the exhaust system
routes the spent combustion gasses away from the engine, where they are diluted by the
atmosphere. This keeps the area around the engine habitable. Second, the exhaust system
confines and routes the gases to the turbocharger, if used. Third, the exhaust system allows
mufflers to be used to reduce the engine noise.
Engine cooling system:
The temperature of burning gases in the engine cylinder is the order of 1500 to 2000’C. To
keep the temperature at the reasonable level, water is circulated inside the engine in water
jackets which are passage around the cylinder, piston, combustion chamber etc. hot water
leaving the jacket is sent to heat exchanger. Raw water is made to flow through the heat
exchanger, where it takes up the heat of jacket water. It is then cooled in the cooling tower
and re-circulates again.
Engine lubrication system:
It includes lubricating oil tank, oil pump and cooler. Lubrication is essential to reduce friction
and wear of engine parts such as cylinder walls and piston.
Lubricating oil which gets heated due to friction of moving parts is cooled before
recirculation. The cooling water used in the engine is used for cooling the lubricant also.
Governing system: The governing of diesel engine is done by varying the quantity of fuel
supplied to the engine. Generally constant stroke with variable suction or variable bypass
method is used to control the quantity oil fuel supplied according to load. Centrifugal type
governor is used to control the suction or bypass of the fuel.
Installation of Diesel Power Plant:
Site selectionof diesel power plant:
The following Factors should be considered while selecting the site for a diesel power plant:
• Foundation sub-soil condition: the condition of sub-soil should be such that a foundation
at a reasonable depth should be capable of providing a strong support to the engine.
•Access to the site: the site should be so selected that it is accessible through rail and road.

9. •Distance from that load centre: the location of the plant should be near the load centre.
This reduces the cost of transmission lines and maintenance cost. The power loss is
minimized.
•Availability of water: Sufficient quantity of water should be available at the site selected.
•Fuel transportation: The site selected should be near to the source of fuel supply so that
transportation charges are low.
Engine construction:

12. Operation and Maintenance:
Diesel engines comprise the vast majority of prime movers for standby power generators
because of their reliability, durability and performance under load. Diesel powered generators
are depended on for back-up power systems in the most critical locations: hospitals, airports,
government buildings, telecommunications facilities, and even nuclear power plants. In
standby power applications, diesel generators can start and assume full-rated load in less than
10 seconds, and they typically can go 30,000 hours or more between major overhauls. This
remarkable set of credentials is unique to diesel engines, but like any mechanical device,
maintenance is critical for ensuring that a diesel powered standby generator will start and run
when needed. Facilities with qualified in-house technical personnel can often perform
required preventive maintenance on diesel generators. Other facility managers prefer to
contract with a local service provider or power system distributor for regular maintenance
service—especially if they have generators in multiple locations. (For unplanned
maintenance, engine repairs or overhauls, it is always best to use qualified diesel service
technicians.)
Preventive maintenance:

13. Because of the durability of diesel engines, most maintenance is preventive in nature.
Preventive diesel engine maintenance consists of the following operations:
• General inspection
• Lubrication service
• Cooling system service
• Fuel system service
• Servicing and testing starting batteries
• Regular engine exercise
It is generally a good idea to establish and adhere to a schedule of maintenance and service
based on the specific power application and the severity of the environment. For example, if
the generator set will be used frequently or subjected to extreme operating conditions, the
recommended service intervals should be reduced accordingly. Some of the factors that can
affect the maintenance schedule include:
• Using the diesel generator set for continuous duty
(Prime power)
• Extreme ambient temperatures
• Exposure to weather
• Exposure to salt water
• Exposure to dust, sand or other airborne contaminates
If the generator set will be subjected to some or all of these extreme operating conditions, it is
best to consult with the engine manufacturer to develop an appropriate maintenance schedule.
The best way to keep track of maintenance intervals are to use the running time meter on the
generator set to keep an accurate log of all service performed. This log will also be important
for warranty support.
General inspection:
When the generator set is running, operators need to be alert for mechanical problems that
could create unsafe or hazardous conditions. Following are several areas that should be
inspected frequently to maintain safe and reliable operation.
• Exhaust system: With the generator set operating, inspect the entire exhaust system
including the exhaust manifold, muffler and exhaust pipe. Check for leaks at all connections,
welds, gaskets and joints, and make sure that the exhaust pipes are not heating surrounding
areas excessively. Repair any leaks immediately.
• Fuel system: With the generator set operating, inspect the fuel supply lines, return lines,
filters and fittings for cracks or abrasions. Make sure the lines are not rubbing against
anything that could cause an eventual breakage. Repair any leaks or alter line routing to
eliminate wear immediately.
• DC electrical system: Check the terminals on the starting batteries for clean and tight
connections. Loose or corroded connections create resistance which can hinder starting.
• Engine: Monitor fluid levels, oil pressure and coolant temperatures frequently. Most engine
problems give an early warning. Look and listen for changes in engine performance, sound,
or appearance that will indicate that service or repair is needed. Be alert for misfires,
vibration, excessive exhaust smoke, loss of power or increases in oil or fuel consumption.
Lubrication service:
Check the engine oil level when the engine is shut down at the interval specified in FIGURE
1. For accurate readings on the engine’s dipstick, shut off the engine and wait approximately

14. 10 minutes to allow the oil in the upper portions of the engine to drain back into the
crankcase. Follow the engine manufacturer’s recommendations for API oil classification and
oil viscosity.
Keep the oil level as near as possible to the “full” mark on the dipstick by adding the same
quality and brand of oil.
Fuel systemservice:
Diesel fuel is subject to contamination and deterioration over time, and one reason for regular
generator set exercise is to use up stored fuel over the course of a year before it degrades. In
additional to other fuel system service recommended by the engine manufacturer, the fuel
filters should be drained at the interval indicated in FIGURE 1. Water vapor accumulates and
condenses in the fuel tank and must also be periodically drained from the tank along with any
sediment present.
Generator set exercise:
Generator sets on continuous standby must be able to go from a cold start to being fully
operational in a matter of seconds. This can impose a severe burden on engine parts.
However, regular exercising keeps engine parts lubricated, prevents oxidation of electrical
contacts, uses up fuel before it deteriorates, and, in general, helps provide reliable engine
starting. Exercise the generator set at least once a month for a minimum of 30 minutes loaded
to no less than one-third of the nameplate rating. Periods of no-load operation should be held
to a minimum, because unburned fuel tends to accumulate in the exhaust system. If
connecting to the normal load is not convenient for test purposes, the best engine
performance and longevity will be obtained by connecting it to a load bank of at least one-
third the nameplate rating.
Preventive maintenance for diesel engine generators plays a critical role in maximizing
reliability, minimizing repairs and reducing long term costs. By following generally
recognized diesel maintenance procedures and specific manufacturer recommendations for
your application, you’ll be assured that your standby power system will start and run when
you need it most.
Performance Testing of Diesel Engine Power Plant:
The performance of the diesel engine focuses on the power and efficiency. The engine varies
with parameters of the engine like piston speed, air-fuel ratio, compression ratio inlet air-
pressure and temperature. The two usual conditions under which I.C. engines are operated
are:
(a) Constant speed with variable load, and
(b) Variable speed with variable load.
The first situation is found in a.c. generator drives and the second one in automobiles, railway
engines and tractors etc. A series of tests are carried out on the engine to determine its
performance characteristics, such as: indicated power (I.P.), Brake power (B.P.), Frictional

15. Power (F.P.), Mechanical efficiency (ηm), thermal efficiency, fuel consumption and also
specific fuel consumption etc. The measurement of these quantities is discussed below.
Indicated MeanEffective Pressure (IMRP)
In order to determine the power developed by the engine, the indicator diagram of engine
should be available. From the area of indicator diagram it is possible to find an average gas
pressure which, while acting on piston throughout one stroke, would account for the network
done. This pressure is called indicated mean effective pressure (IMEP).
Economyof dieselpowerplant:
The diesel engine (also known as a compression-ignition or 'CI' engine) is an internal
combustion engine in which ignition of the fuelthat has been injected into the combustion
chamber is initiated by the high temperature which a gas achieves when greatly compressed
(adiabatic compression). This contrasts with spark-ignition engines such as a petrol
engine (gasoline engine) or gas engine (using a gaseous fuel as opposed to gasoline), which
use a spark plug to ignite an air-fuel mixture.
A Diesel engine built by MAN AG in 1906
The diesel engine has the highest thermal efficiency of any standard internal or external
combustion engine due to its very high compression ratio and inherent lean burn which
enables heat dissipation by the excess air. A small efficiency loss is also avoided compared to
two-stroke non-direct-injection gasoline engines since unburnt fuel is not present at valve
overlap and therefore no fuel goes directly from the intake/injection to the exhaust. Low-
speed diesel engines (as used in ships and other applications where overall engine weight is
relatively unimportant) can have a thermal efficiency that exceeds 50%.
Diesel engines are manufactured in two-stroke and four-stroke versions. They were originally
used as a more efficient replacement for stationary steam engines. Since the 1910s they have
been used in submarines and ships. Use in locomotives, trucks, heavy equipment and
electricity generation plants followed later. In the 1930s, they slowly began to be used in a
few automobiles. Since the 1970s, the use of diesel engines in larger on-road and off-road
vehicles in the USA increased. According to the British Society of Motor Manufacturing and
Traders, the EU average for diesel cars account for 50% of the total sold, including 70% in
France and 38% in the UK.
The world's largest diesel engine is currently a Wärtsilä-Sulzer RTA96-C Common Rail
marine diesel, which produces a peak power output of 84.42 MW (113,210 hp) at 102 rpm.

16. Advantages and disadvantages ofdieselpower plant over thermal plants:
Advantages of Diesel Power Station:
1. This is simple in design point of view.
2. Required very small space.
3. It can also be designed for portable use.
4. It has quick starting facility, the small diesel generator set can be started within few
seconds.
5. It can also be stopped as when required stopping small size diesel power station, even
easier than it’s starting
6. As these machines can easily be started and stopped as when required, there may not be
any standby loss in the system.
7. Cooling is easy and required smaller quantity of water in this type power station.
8. Initial cost is less than other types of power station.
9. Thermal efficiency of diesel is quite higher than of coal.
10. Small involvement is less than steam power station.
Disadvantages of Diesel Power Station:
1. As we have already mentioned, the cost of diesel is very high compared to coal. This is
the main reason for which a diesel power plant is not getting popularity over other means
of generating power. In other words the running cost of this plant is higher compared to
steam and hydro power plants.
2. The plant generally used to produce small power requirement.
3. Cost of lubricants is high.
4. Maintenance is quite complex and costs high.
Presenttrends in dieselresearch:
The present research work in the diesel engines development is directed towards higher
operation speeds, lower specific fuel consumption (kg/kW-hr), lower specific weight (kg/kW)
and higher unit size. An air-fuel ratio of 25 : 1 is required for the combustion of diesel fuels.
The power developed in the engine is proportional to the weight of fuel burnt in unit time.
Therefore, the power developed by the engine can be increased by increasing the weight of
air present in the cylinder at each cycle or by increasing the number of cycles per unit time
(r.p.m.) or using both. So long the necessary weight of air can be provided in an engine
cylinder of given size, theoretically there is no limit to the weight of fuel burnt in unit time
and hence to the power which can be developed. The increased weight of fuel burnt creates

17. lot of mechanical and thermal problems. The solution of these problems can be expected to
be major lines of continuing research work.
Discussionand conclusion:
In this unit, we have learnt the functioning of diesel power plant. The diesel engine drives
alternator, which converts mechanical energy in to electrical energy. In this unit, we have
also studied the concept of fuel injection system and its functioning. The unit, also elaborated
on various types of injection schemes. The diesel engine plants are mainly utilised to generate
small power output. Which are mostly utilised as standby modes, when power not takes
place? Its cost is high.