What is homogeneous and stratified charge?

What is homogeneous and stratified charge?

The term “stratified charge” refers to the working fluids and fuel vapors entering the cylinder. In a homogeneous charge system, the air/fuel ratio is kept very close to stoichiometric, meaning it contains the exact amount of air necessary for complete combustion of the fuel.

What is homogeneous operation?

Homogeneous Charge Compression Ignition (HCCI) is a form of internal combustion in which well-mixed fuel and oxidizer (typically air) are compressed to the point of auto-ignition. As in other forms of combustion, this exothermic reaction releases energy that can be transformed in an engine into work and heat.

What is the basic difference between stratified engine and HCCI?

3.2 Stratified-Charge Engines The primary physical difference between standard homogeneous-charge compression-ignition (HCCI) engines and stratified-charge engines is that the fuel injector is moved from the intake port to inside of the engine cylinder.

What are the important features of a stratified charge engine?

In the stratified charge engines, the mixture composition is varied within the combustion chamber such that stoichiometric or slightly richer mixture exits near spark plug to provide good ignition characteristics and the mixture gets progressively leaner away from the spark plug.

Why do engines downsize?

In the automotive industry, engine downsizing is the practice of utilizing smaller combustion engines over larger ones of the same power capacity when manufacturing vehicles. Reducing the number of cylinders also reduces the amount of friction in the engine, increasing the efficiency. …

What is a stratified scavenging engine?

One such technique is stratified scavenging. STRATIFIED SCAVENGING – The conventional two- stroke engine operates by inducing the air and fuel into. the crankcase and supplies a homogeneous mixture of. air and fuel to the cylinder.

What is homogeneous fuel mixture?

HCCI is a concept where in a lean homogeneous mixture of air and fuel is compressed and ignited. Compression of this mixture leads to auto-ignition in multiple locations, followed by combustion that is significantly faster than the conventional Otto or Diesel modes.

What is homogeneous mixture in engine?

Homogenous charged compression ignition (HCCI) engine is a mix of both conventional spark-ignition and diesel compression ignition technology. The combination of these two designs offers diesel-like high efficiency and at the same time, reduces and particulate matter emissions.

What is meant by SI engine?

A spark-ignition engine (SI engine) is an internal combustion engine, generally a petrol engine, where the combustion process of the air-fuel mixture is ignited by a spark from a spark plug.

Does TFSI mean petrol?

Turbocharged Fuel Stratified Injection
TFSI stands for ‘Turbocharged Fuel Stratified Injection’ and is used to signify that the engine is a turbocharged petrol unit.

Can you reduce engine capacity?

The University of Bath published research carried out by its Powertrain and Vehicle Research Centre which demonstrated that it is possible to reduce engine capacity by 60% and still achieve the torque curve of a modern, large-capacity naturally-aspirated engine, while encompassing the attributes necessary to employ …

How does a stratified charge engine differ from a HCCI engine?

R. Evans, in Lean Combustion (Second Edition), 2016 The primary physical difference between standard homogeneous-charge compression-ignition (HCCI) engines and stratified-charge engines is that the fuel injector is moved from the intake port to inside of the engine cylinder. This change has a number of consequences.

When to use stratified vs.homogeneous combustion?

The GDI design allows for two different modes of combustion, stratified and homogeneous. Stratified combustion is typically used during idle and light to moderate loads at low engine speeds while homogeneous combustion is used at moderate to high loads and medium to high engine speeds.

What are the benefits of stratifying the charge?

By stratifying the charge, the ignition timing can also be delayed. There are a couple of benefits: Less risk of engine knock. The excess air surrounding the air-fuel charge (“stratified” charge) helps to cool down the combustion chamber, reducing the likelihood of knocking, enabling higher compression ratio.

How does a homogeneous charge system affect combustion?

In a homogeneous charge system, the air/fuel ratio is kept very close to stoichiometric, meaning it contains the exact amount of air necessary for complete combustion of the fuel. This gives stable combustion, but it places an upper limit on the engine’s efficiency: any attempt to improve fuel economy by running…