Automotive Engineering-Gasoline direct injection Overview

☑ Gasoline Direct injection(GDI) Fundamentals

Introduction

In the recent years, heavy emphasis on reducing the BSFC while meeting the stringent emission norms

Over the past two decades, attempts have been made to develop an internal combustion engine for automotive applications that combines the best features of the SI and the diesel engines.

The objective has been to combine the specific power of the gasoline engine with the efficiency of the diesel engine at part load.

Research has indicated that a promising candidate for achieving this goal is a direct-injection, four-stroke, sparkignition engine that does not throttle the inlet mixture to control the load.

In this engine, a fuel spray plume is injected directly into the cylinder, generating a fuel-air mixture with an ignitable composition at the spark gap at the time of ignition.

This class of engine is designated as a direct-injection, stratified-charge (DISC) engine

Potential benefits of GDI over PFI

Fuel System requirements

Fuel injector characteristics

Fuel spray characteristics

The fuel injection system in a GDI engine is a key component that must be carefully matched with the specific in cylinder flow field to provide the desired mixture cloud over the entire operating range of the engine

A well-atomized fuel spray must be produced for all operating conditions

A GDI fuel system needs to provide for at least two, and possibly three or more distinct operating modes.

Flow structure

Fuel air mixing

Combustion chamber geometry

Engine operating modes and fuel injection strategies

Types of combustion chambers