UNIT-5 --Recent trends in IC Engines.pptx

RECENT TRENDS

1. UNIT-V RECENT TRENDS

2. 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

3. Homogeneous charge spark ignition

4. 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 method which is also known as SCCI.

5. Conventional spark ignition

6. 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.

7. 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

8. Lean-burn engine

9. Lean-burn engine

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

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

12.   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.

13. 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.

14. 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.

15. 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.

16. 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.

17. 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.

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

19. 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 and reduced operation expenses.

20. 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.

21. 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.

22. 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.5.6. The rail is fed by a high pressure fuel pump. The injectors, which are fed from the common rail, are activated by solenoid valves.

23. Diesel fuel engine with rail

24. 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

25. 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.

26. 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. 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.

27. Gasoline Direct Injection Engine

28. 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.

29.   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.

30. Series system

31. 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 changes the speed. The engine is never required to idle thus reducing exhaust emission.

32. 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.

33. Series system

34. Operation method of parallel system- electric only

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

36. Operation method of parallel system- Battery charging

37. Operation method of parallel system- Regenerative braking

38. 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 regenerates the batteries.

39. 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

40. Simplified structure of a combined hybrid electric vehicle

41. Variable geometry turbocharger

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

43. NOX ABSORBER NO x absorber is developed to reduce the oxides of nitrogen emitted by the exhaust gas from the lean burn internal combustion engine. This NO x 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.

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

45. Free energy level

46. Free energy level