ENHANCEMENT OF INTERNAL COMBUSTION ENGINES

MOLEBEDI KEOBEETSWE 201000082

KEALEBOGA MOGAPI 201001654

INTERNAL COMBUSTION ENGINE

CLASSIFICATION OF ICEs

Principle of operation

– Four stroke engine

– Two stroke engine

IDEAL CYCLE

• Carnot cycle is ideal

CYCLES OF OPERATION• The ideal air standard Otto cycle

• Process 1- 2 isentropic compression

• Process 2-3 constant volume heat transfer to the air from external source (piston at TDC)

• Process 3-4 isentropic expansion (power stroke

• Process 4-1 heat rejection at constant volume

CYCLES OF OPERATION• The ideal air standard diesel cycle

In the Diesel cycle the heat addition takes place at constant pressure. Accordingly, process 2-3 involves both work and heat.

Spinning Gas

• Employing spinning gasThe efficiency of the internal combustion engine might be

enhanced by employing spinning gas. A gas spinning at near sonic velocities has an effectively higher heat capacity, which allows practical fuel cycles, which are far from the Carnot efficiency, to approach more closely the Carnot efficiency.

Hydrogen• The introduction of hydrogen. It is suitable in

that it has low ignition energy, wide range of flammability, high diffusivity.

BENEFITS

• Reduced carbon emissions to a great extent

• Abundant in nature

DRAWBACKS

• Premature ignition

• High flammability(Hydrogen + air mixture)

Forced induction engine

In a forced induction engine, air is forced into the combustion chamber at a higher pressure than usual, creating a higher compression and more power from each stroke of the engine

BENEFITS• More power without increase in engine size

DRAWBACKS• Fuel consumption and turbo lag

Fuel injection• Fuel injectors spray gasoline into the air intake

manifold, where fuel and air mix together into a fine mist, the mixture is then brought to the combustion chamber. Engines with fuel injection are also more efficient and more responsive to changes in the throttle.

BENEFITS

• Better throttle response, increased fuel efficiency, more power

DRAWBACKS

• More complexity and potentially expensive repair

Variable valve timing and lift electronic control

• More air and fuel into the valves at different speeds. This makes an engine more flexible and allows it to deliver peak performance in a variety of conditions. It also increases fuel economy.

Benefits: Fuel economy, more flexible power delivery

Drawbacks: Greater cost to produce

Duel over head camshaft {DOHC}

• “Dual overhead camshafts" , The term refers to the number of overhead camshafts above each cylinder in the engine.• Camshafts are part of your car's valve train, which is a system that controls the flow of fuel and air into the cylinders. For many decades cars primarily had OHV engines, meaning overhead valves, also called "pushrods."

• Benefits: Better performance

• Drawbacks: Increased complexity

Cylinder deactivation

• Cylinder deactivation is a derived form of active cam switching.

• In this method, while cruising a part of cylinders are switched off by switching to a cam without lobes.

• This method is successful because of following– Lesser fuel consumption– Less heat generation– Less power lost in managing other cylinders

• This is mostly employed in V Type Engines.

Six stokes engine

• The invention of six stroke engines was for the following reasons:• Less weight to power ratio

• Less scavenching

• Less moving parts

• More power and fuel economy

• Obtain freedom in designing

• Better cooling

• Six stroke engines are developed in two different ways

Air/Water injection to cylinder

• In this method air or water is injected to the cylinder at the end of exhaust stroke.

• The fluid absorbs the heat and expands providing another power stroke. An exhaust stroke is provided to removed the fluid from cylinder.

• Three recognized names in this section are:– Bajulaz six stroke engine (Preheating of air)

– Velozeta six stroke engine (Injection of air)

– Crower six stroke engine (Injection of water)

Direct Injection• With direct injection, the advantages of CI

engines can be obtained in SI engines also.

• In direct injection, first the air is filled in the cylinder. Then half way through the compression stroke, a small amount of fuel is injected to the cylinder to create a lean mixture.

• At the end of compression, just before the spark the rest of fuel is injected to the head of spark plug.

• The burning of fuel occurs in a stratified pattern near the spark plug.