1. UNIT-V
RECENT TRENDS

2. TOPICS
Homogeneous charge compression ignition engine – lean
burn engine – stratified charge engine – surface ignition
engine – electronic engine management – common rail
direct injection diesel engine – gasoline direct injection
engine – hybrid electric vehicles – on board diagnostics –
variable geometry turbochargers – NOx absorbers.

3. HOMOGENEOUS CHARGE COMPRESSION IGNITION
(HCCI)
• Homogeneous Charge Compressive Ignition is an internal
combustion in which well-mixed fuel and atmospheric air are
compressed to the auto ignition point. This exothermic reaction
releases chemical energy which is transferred into work and heat.
Start of combustion in three types of engines

4. Homogeneous charge spark ignition

5.  HCCI has two forms of combustion used in engines.
 Homogeneous charge spark ignition and
 Stratified charge compression ignition.
Here HCCI works with both gasoline engine and diesel engines.
Gasoline work under homogeneous charge spark ignition method and it
is also known as (HCSI). Likewise diesel engines work under stratified
charge compression ignition methodwhich is also known as SCCI.

6. Conventional spark ignition

7. LEAN-BURN ENGINE
 Lean-burn means pretty much what it says. It is a lean amount of fuel
supplied to and burned in an engine combustion chamber. Normal air-
to-fuel ratio is on the order of IS:1. True lean-burn can go as high as
23:1.

8. Working Principle
• A lean burn mode is a way to reduce throttling losses. An engine in
a typical vehicle is sized for providing the desired for acceleration, but
must operate well below the particular point in normal steady-speed
operation. Ordinarily the power is cut by partially closing a throttle.
However, the extra work done in pumping air through the throttle
reduces efficiency. power

9. Lean-burn engine

10. Lean-burn engine

11. Advantages
 Emit fewer unburned hydrocarbons and green house gases
 Higher fuel economy.
 A lean-burn mode is a way to reduce throttling losses.

12. Disadvantages
 Relatively high cost.
 Catalytic converter is used to reduce the NOX emission.

13. STRATIFIED CHARGE ENGINE
• The stratified charge engine is a type of internal combustion engine
which runs on gasoline. When compared with conventional internal
combustion engine, the compression ratio is high in stratified charge
engine. Here we use exhaust gas recirculation system (EGR) or
catalytic converters to reduce the emissions from the engine cylinder.
• Stratified charge combustion engine utilizes a method of
distributing fuel that successively builds layers of fuel in the
combustion chamber. The initial change of fuel is directly injected into
a small concentrated area of the combustion chamber where it ignites
quickly.

14. Working Principle
• In traditional engine, we use air and fuel mixture at correct
proportion for the working of engine. In stratified charge engine, we
use lean mixture which is so low in fuel which could not be used in
conventional engine. A pre combustion chamber is designed before the
combustion chamber where the spark plug is located.

15. Stratified charge engine
 It contains a spheroid cavity that imparts a swirling movement to
the air contained by the cylinder during compression. During
injection, fuel is sprayed nearer to the spark plug, for turbulent flow we
use artifices life "swirl" or "tumble".
 The working of stratified charge engine comprises of two modes.
 Lean mode.
 Normal mode.

16. Lean Mode
• Lean mode operates at very low engine load. Here the injection
takes place at the end of the compression stroke and swirl effect is
created at the piston cavity. Fuel sprayed by the injector is confined
near the spark plug and a very high pressure is developed in the
cylinder at this moment.

17. Normal Mode
• Normal mode works under very high engine load. When engine
power is required injection takes place in normal mode, during the
admission phase.
• This makes it possible to achieve a homogeneous mix, as it is the
case with traditional injection.

18. SURFACE IGNITION ENGINE
The other important abnormal combustion phenomenon is surface
ignition. Surface ignition is ignition of fuel air charge by overheated
valves or spark plugs, by glowing combustion chamber deposits, or by
any other hot spot in the engine combustion chamber. It is the initiation
of flame front by a hot surface other than the spark plug. Mostly
surface ignition is due to carbon deposits.

19. Normal combustion (a,b), Abnormal
combustion and problems (c,d)

20. ELECTRONIC ENGINE MANAGEMENT
• It provides the information about how fast the engine is running or
where the crankshaft is in its rotation. ECU senses this information and
adjusts the fuel injection and the spark timing so that the engine speed
does not exceed the safe operating limits.
Purpose of EEM
• Controlling of Engine operation electronically by electronic
components.
• Benefits to the motorist, more power, better mileage, a smoother idle
andreduced operation expenses.

21. Basic Components of EEM
 Electronic Control Module
 Fuel Delivery System
 Ignition System
 Sensors
Electronic Control Module
 It is a extremely reliable piece of hardware.
 It process information hundreds of times per second.
 It is actually a microprocessor.
 It is programmed by the Manufacturer.

22. Fuel Delivery system
 The fuel line passes through which feeds each injector
and it passes through a pressure regulator.
 The surplus fuel heading back to the tank in the return
line. The air is taken from the atmosphere. It is mixed
with fuel just before the inlet valve by the fuel injector.
Ignition System
 To maximize the Engine output, spark should be at the
precise moment.
 Maximum combustion chamber pressure can be attained.
 A mechanical advance distributor is used for this.
 A spark advance map is developed and stored in the
ECU.

23. COMMON RAIL DIRECT INJECTION
DIESEL ENGINE(CRDDI)
 CRDDI is technically efficient engine which is used to overcome
the problems such as improper automization which leads to more
unburnt particles, causing more pollution, lower fuel efficiency and
less power.
 A diesel fuel injection system employs a common pressure
accumulator, called the rail, which is mounted along the engine block
as shown in Fig.The rail is fed by a high pressure fuel pump. The
injectors, which are fed from the common rail, are activated by
solenoid valves.

24. Diesel fuel engine with rail

25. Principle of CRDDI in Gasoline Engines
 Gasoline engines are using carburetors for the supply of air-fuel
mixture before the introduction of MPFI system. CRDDI principle can
also be adopted for gasoline engines. This engine is known as Gasoline
Direct Injection (GDI) gasoline engines.
 Advantages of CRDDI System
 Better pulverization of fuel.
 Doubling the torque at lower speeds.
 Improved power, increased fuel efficiency and reduced
noise.
 Less emissions and reduced particulates in the exhaust

26. GASOLINE DIRECT INJECTION ENGINE
(GDIE)
• In internal combustion engines, Gasoline Direct Injection Engine
(GDIE), also known as Petrol Direct Injection Engine or Direct
Petrol Injection Engine or Spark Ignited Direct Injection Engine
(SIDIE) or Fuel Stratified Injection Engine (FSIE), is a variant of fuel
injection employed in modern two-stroke and four-stroke gasoline
engines.

27. Working Principle
• The major advantages of a GDI engine are increased fuel efficiency
and high power output. Emission levels can also be more accurately
controlled with the GDI system. The cited gains are achieved by the
precise control over the amount of fuel and injection timings that are
varied according to engine load.
• In addition, there are no throttling losses in some GDI engines,
when compared to a conventional fuel-injected (or) carburetor
engine, which greatly improves efficiency, and reduces pumping
losses in engines without a throttle plate.

28. • Engine speed is controlled by the engine control unit/engine
management system (EMS), which regulates fuel injection
function and ignition timing, instead of having a throttle
plate that restricts the incoming air supply.

29. Gasoline Direct Injection Engine

30. HYBRID ELECTRIC VEHICLES
• Internal combustion engines produce an accountable emission and
are also less efficient at part loads. But electrical drives have no
emission, but varying in efficiency for limited range. In advance
technology, both aspects are combined and the hybrid vehicle is
formed. A hybrid electric vehicle has two types of energy storage units
by electricity and fuel. Electricity means that a battery is used to store
the energy. Fuel means that a tank is required in the form of I.C engine
to produce mechanical power. Also fuel cell will be used to convert
fuel to electric energy.

31. Types of Hybrid System
 The hybrid systems are classified into three types.
 Series system
 Parallel system
 Series-Parallel system (or) Combined system
Series System
In series system, the combustion engine drives an electric generator
instead of driving the wheels. The electric motor provides the power
to the wheels. The generator is employed to recharge thebatteries and
also provide power to electric motor to move the vehicle.

32. Series system

33. Advantages of Series System
 No mechanical link between the combustion engine and
its wheel.
 No conventional transmission elements (gear box,
transmission shaft) are placed..
 The engine drives a generator to run at optimum
performance.
 The combustion engine can operate in a narrow rpm
range, even vehicle changesthe speed.
 The engine is never required to idle thus reducing
exhaust emission.

34. Disadvantages of Series System
 The series system has less efficient. It requires larger
and heavier battery back up.
 The power from the combustion engine has to run
through both the generator and electric motor. During
longer drive the total efficiency is less, due to several
energy conversions
 The engine works very hard to maintain battery charge
as the system is not running in parallel.

35. Parallel system

36. Operation method of parallel system- electric
only

37. Operation method of parallel system-
Hybrid/Electric assist

38. Operation method of parallel system- Battery
charging

39. Operation method of parallel system-
Regenerative braking

40. Advantages
 Total efficiency is higher at long distance and highway
 Larger flexibility to switch over between electric motor
 It does not require separate generator for recharging
since the motor regeneratesthe batteries.

41. Disadvantages
 Complicated system.
 If heat engine does not operate in correct rpm, the
efficiency will drop at low speed.
 If the heat engine is not linked to the wheels, the battery
will not be charged.
• Examples
 Honda's insight
 Volvo 26 ton truck
 Accord hybrids
 BMW 7 series Active Hybrid

42. Simplified structure of a combined
hybrid electric vehicle

43. Variable geometry turbocharger

44. Power comparison between normal engine
and variable geometry turbo charger

45. NOX ABSORBER
 NOx absorber is developed to reduce the oxides of nitrogen emitted by
the exhaust gas from the lean burn internal combustion engine. This
NOx absorber is purely designed for diesel engines. Nowadays,
designers have the challenges to emit the oxygen from exhaust. The
3-way catalytic converter technology is the successful way for the
internal combustion engines.

46. Oxidation: 2 NO+O₂= 2 NO₂ Absorption:
2 NO+1.5O₂+ MO=M (NO3)2

47. Free energy level

48. Free energy level