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Alexandria University Faculty of Engineering Marine and Naval Architecture Department Modern Diesel Engines Presented to: Prof . Dr : Mosaad Mosleh By: Eng: Walaa Morgan Ebied Eng: Noha Hassan

Modern Diesel Engines

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it's about cam less engines

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Page 1: Modern Diesel Engines

Alexandria University

Faculty of Engineering

Marine and Naval Architecture Department

Modern Diesel Engines

Presented to:

Prof . Dr : Mosaad Mosleh

By:

Eng: Walaa Morgan Ebied

Eng: Noha Hassan

Page 2: Modern Diesel Engines

Modern Diesel Engines

The internal combustion engine (ICE) finds its place in the market with latest

design modifications in various components to improve efficiency, economy and

overall performance .However, one component has remained unchanged in the

internal combustion engine development i.e., the camshaft ,has been the primary

means of controlling the valve actuation and timing, and therefore, influencing the

overall performance of the vehicle. Camless technology is capturing the future of

internal combustion engines.

It has been known to man that if valves could be controlled independently in an

Internal Combustion Engine then there would be benefits like increased power,

reduced emissions and increased fuel economy. In the camless technology valve

motion is operated by valve actuators of electro-mechanical and electro-hydraulic

type.

The other type of modern diesel engines is dual fuel engines

Dual Fuel engine

What is Dual Fuel engine?

A dual fuel engine burns both diesel and natural gas at the same time.

It differs from a Bi-fuel engine in so much that a Bi-fuel engine will run on one type

of fuel or another, not two fuels simultaneously as is the case with dual fuel.

The four stroke cycle is maintained as with a standard diesel engine. The only

difference is that the gas is injected directly into the cylinder while the inlet valves

are open and the engine is drawing in air. As a result a homogonous mix of gas

and air is present when the inlet valves close.

Page 3: Modern Diesel Engines

Dual Fuel engine operation

The gas is mixed with air before compression starts, a gas pressure of about 5 bar

is sufficient. This gas pressure is in the same range as the gas pressures in steam

turbine installations. Close to top dead- centre a very small amount of MDO is

injected in order to trigger ignition. On pilot injection, a flame is created which

then ignites the main air/fuel mixture in the main combustion chamber. Ignition

timing is thus directly controlled via injection timing of the pilot fuel.

1.The Air and gas enter the cylinder

The Air and gas mixture is compressed

The piston begins to move back up the cylinder on

the compression stroke, prior to the piston

reaching TDC the reduced amount of diesel is injected.

Page 4: Modern Diesel Engines

2. Diesel Fuel is injected into the cylinder

As the piston reaches TDC a reduced amount of

diesel fuel is injected to be utilized as the source of ignition.

3. The air and gas mixture combusts as a Result of the diesel

injection

This reduced diesel injection is sufficient to act as the ignition

catalyst and thus, combustion of the air and gas mixture

together with the diesel takes place.

4. The burnt mixture exits the cylinder as normal on the

exhaust stroke

The exhaust stroke remains unchanged and the exhaust gases

exit the cylinder as normal.

Page 5: Modern Diesel Engines

Following main modifications are made in the diesel engines

considering the use of gas as fuel:

Gas admission to each cylinder by individual valves.

Charge air and exhaust manifolds equipped with pressure relief valves to

avoid any gas operation risks.

Common rail system for pilot fuel oil injection integrated in the cylinder

head. The pilot fuel quantity is controllable by the injection system.

Separate conventional fuel system for liquid fuel mode.

A specially designed DF engine management system for the whole

operating range.

The basic design difference between a conventional diesel engine and a

dual fuel engine lies in the fuel injection systems.

Features of Dual Fuel Engine:

Less operation cost

→ Main fuel : Natural Gas

Environmental friendly

→ Drastic reduction of NOx, SOx & CO2 emission

Stable operation

→ Pilot injection system

→ Operatable on either fuel of natural gas or diesel oil

Excellent dependability

→ Main component : Diesel engine

Clean combustion and Less maintenance cost

Page 6: Modern Diesel Engines

Effective utilization of existing assets

Diesel fuel oil injection:

The diesel fuel oil supply system on the engine is divided into two systems.

Pilot Fuel Injection System:

The pilot fuel is raised to the required by a pump unit incorporating duplex filters,

pressure regulator and engine driven radial piston type pump. The high pressure

pilot fuel is then distributed through a common rail pipe to the injection valve at

each cylinder. The pilot fuel injected at around 900 bars pressure and the timing

and duration are electronically controlled. The individually controlled solenoid

valve allows optimum timing and duration of pilot fuel injection into every

cylinder when the engine is running in gas mode.

Main Diesel Fuel Oil Injection System:

The main diesel oil fuel is fed to a normal camshaft driven injection pump by

which it is pumped at high pressure to a spring loaded injection valve of standard

design for a diesel engine. The larger needle of the twin-needle injection valve is

used in diesel engine mode and the smaller needle for pilot fuel oil when the

engine is running in gas mode. Main diesel engine is hydro mechanically

controlled.

Page 7: Modern Diesel Engines

Schematic Diagram for DF

Page 8: Modern Diesel Engines

CAMLESS ENGINES

-Cam is a rotating machine element which

gives reciprocating motion to the follower.

-The motion of the follower is pre-determined

and accordingly the Cam is designed.

-The cams are normally placed on a fixed

camshaft which is then geared to the crankshaft.

-Movement of inlet and exhaust valves of Conventional Four Stroke IC Engine with

the help of Cam.

Conventional Valve train

Page 9: Modern Diesel Engines

It is fixed to deliver only one specific cam timing. The cam lobes

have to be shaped such that when the valve travels up and down at the engines

maximum speed it should still be able to slow down and gently contact the valve

seat. The valves crashing down on their valve seats results in an engine that is real

noisy and has a short life expectancy. Having different cam profiles will result in

different engine characteristics. While high-rpm power and low rpm-torque can be

each optimised, acompromise is required to obtain the best of both in the same

engine. With Variable Valve Timing (VVT) technologies the compromise is getting

better and better -reasonable low down torque and high-speed power .

Disadvantages Of Conventional Valve train

Increased frictional losses

Cam profile is fixed

Noise

Overview Of Camless Engine

Mainly Five Sensors are present,which senses;

Speed of the engine.

Load on the engine.

Exhaust gas Sensor.

Valve position Sensor.

Current Sensor.

Page 10: Modern Diesel Engines

Sensors sense parameter & Send signals to (Electronic Control Unit ) ECU

ECU contains microprocessors with associated software

This ECU controls the actuators to work according to requirements

Microprocessors are present in ECU to issue signals and control the Actuators.

Actuators

It is electro_hydraulic camless valve train (ECV)

Uses elastic property of compressed hydraulic fluid which acts like a liquid spring ,

accelerates & decelerates the valves

Types of Camless Mechanisms

I. Electromechanical Poppet Valves.

II. Electromechanical Ball Valves.

III. Electrohydraulic Poppet Valves.

I. Electromechanical Poppet Valves

Early systems magnetic attraction/repulsion was used on an iron or ferromagnetic

armature

Varying Air Gaps which lead to high energy losses and High Seating Velocities

which made varying of the lift difficult.

Page 11: Modern Diesel Engines

It is replaced with a current-carrying armature coil. A magnetic field is generated by a magnetic field generator and is

directed across the fixed air gap.

The force generated on the armature coil drives the armature coil

linearly in the air gap in a direction parallel with the valve stem.

Depending on the direction of the current supplied to the armature coil,

the valve will be driven toward an open or closed position.

II. Electromechanical Ball Valves

An alternative to the conventional poppet valve for use in camless valve trains is

a ball valve. This type of electromechanical valve system consists of a ball through

which a passage passes. If the ball is rotated such that the passage lines up with

Page 12: Modern Diesel Engines

other openings in the valve assembly, gas can pass through it. Opening and closing

the valve is accomplished by electromagnets positioned around its exterior

Referring to the following figure

The valve housing (7) is shown in two pieces. Ball valve (8) has two rigidly attached

pivots (12). the ball valve needs only to rotate on its axis to achieve the desired

flow conditions, rather than be accelerated up and down in a linear fashion. A

partially open ball valve state may also be able to be used to create more

turbulence disc (10) is permanently attached and indexed to the ball

valve and contains permanent magnets around its perimeter. The electromagnets

(11) are situated on both sides of the ball valve (8) and they are fixed to the valve

housing. The electromagnets are controlled through the ECU. A crank trigger

sensor on the crankshaft provides information about the position of the pistons

both electromagnets so that they are of opposite polarity to the magnets in

the ball valve, rotating the ball valve to the closed position.The substitution of a

Page 13: Modern Diesel Engines

simple,efficient ball valve and valve housing arrangement in a four stroke

reciprocation piston engine eliminates all the independent moving parts in the

valve train. This may even be an improvement over the poppet valve camless

system.

III. Electro-hydraulic Poppet Valves

The engine poppet valves (22) and the valve springs (24) that are used to reset

them are shown. The poppet valves are driven by hydraulic actuators (26),

which are controlled by electrically operated electro-hydraulic valves (28)

supplying hydraulic fluid to the actuators via conduit (29). The preferred hydraulic

fluid is engine oil, supplied to the electro-hydraulic valves by the pressure rail (30).

An engine-driven hydraulic pump (32) supplies the oil pressure, receiving the oil

from the engine

oil sump (34). The pump output pressure is also limited by an unloader valve (36),

as controlled by an accumulator (38) connected to the oil pressure rail.

Page 14: Modern Diesel Engines

With this design the hydraulic pump could be periodically disconnected, such as

under braking, so that the valve train would run off the stored accumulator

hydraulic pressure. As is the trend with all modern engine systems, the camless

engine has an even greater reliance on sensors. The valve actuation and control

system typically needs a manifold pressure sensor, a manifold temperature

sensor, amass flow sensor, a coolant temperature sensor, a throttle position

sensor, an exhaust gas sensor, a high resolution engine position encoder, a

valve/ignition timing decoder controller, injection driver electronics, valve coil

driver electronics, ignition coil driver electronics, air idle speed control driver

electronics and power down control electronics. A valve developed by Sturman

Industries is said to be about six times faster than conventional hydraulic valves.

To achieve such speeds, it uses a tiny spool sandwiched between two electrical

coils. By passing current back and forth between the coils, a microprocessor-

based controller can quickly move the spool back and forth, thereby actuating the

engine valves in accordance.

Advantages of Camless Engines

Infinitely variable valve timing.

More torque is made available throughout the rev-range.

Increases durability and engine life.

Valve train weight which limits the rotational speed at which the engine can

operate is reduced.

Increases engine performance.

Decreases fuel consumption

Decreases harmful emissions

The efficiency of a camless engine would be 20% greater than a comparable

camshaft-operated engine.

Page 15: Modern Diesel Engines

Disadvantages of Camless Engines

1. Relatively high cost (cost of microprocessor & software control)

2. Power consumption (opening & clothing of valves require some power)

3. Noise and vibration

Questions

Q1) With the aid of a neat sketch Explain the Operation of the Dual

Fuel engine . page 3,4

Q2) Diesel engines can be modified and uses as Dual Fuel engines

what are these modifications? page 5

Q3) The diesel fuel oil supply system on the engine is divided into

two systems , Explain the two systems. Page 6

Q4) Draw Schematic Diagram for Dual fuel engine . page 7

Q5) There are three types of Camless Mechanisms , Define them,

and Explain briefly one type. page 10,11,12.13