1. Gasoline Direct Injection SI Engines
P M V Subbarao
Professor
Mechanical Engineering Department
I I T Delhi
Next Generation Eco-friendly SI Engines….

2. Next generation Engines
GDI

3. The Top Most Fuel Efficient Cars of 2018 - 1
Mitsubishi Mirage 1500 GDi Dingo Pearl : Naturally aspirated petrol Engine Inline 4 cyl.1468 cc : DOHC : 16 valves : :140 Nm at 3500 rpm : CR=11:1.
This car gets 37 miles per gallon in town and 43 mpg on the open road.
It’s priced to sell at ~ $15,000.

4. The Top Most Fuel Efficient Cars of 2018 - 2
2018 Honda Fit: GDI Engine:
Naturally aspirated petrol Engine Inline 4 cyl.1498 cc : DOHC : 16 valves : :155 Nm at 4600 rpm : CR=11.5:1.
This car gets 33 miles per gallon in town and 40 mpg on the open road.

5. The Top Most Fuel Efficient Cars of 2018 - 3
2018 Hyundai The Elantra Eco trim: GDI Engine:
This car gets 32 miles per gallon in town and 40 mpg on the open road.

6. Challenges in Developing GDI Engine
The fuel injection to the cylinder should meet two requirements.
First one, it should enable the homogeneous charge burning.
Secondly, It should also enable obtaining a lean mixtures close to cylinder walls.
The equivalence ratio around spark plug must be conducive for ignition.

7. A Missed Chance Cannot be Regained
Ignition Energy Supplied, ES, mJ

8. Operating modes of the GDI engine
Superior output mode
Injection in late intake stroke
Wider spray with high penetration for charge homogenization
A/F – slightly leaner than Stoichiometric
Homogeneous A-F Mixture
Complete Vaporization of Fuel
Ultra Lean combustion mode
Very lean stratified mixture : A/F ~ 30
Injection during compression
Compact spray, deflected from the piston top to the spark plug
Distinct Stratification
At spark , ignitable mixture conditions
It is two engines in one place

9. Special Geometry of Cylinder & In-cylinder Flow
Carburetor Era : Flat piston & Flat Cylinder --- Wedge shaped cylinder with flat piston.
SPI & MPI Era : Wedge shaped cylinder head --- special manifold for generation more turbulence – Optimized location of spark plug.
GDI Era : To design entire cylinder, piston and manifold geometry using computational and experimental fluid mechanics.
More the use of Fluid Mechanics, the better will be the engine.
Three dimensional turbulent flow simulation will be culmination of IC Engine Development.

10. Tough Fluid Mechanics of Fuel Admission
GDI : 50 – 100 bar
Multi Poin Injection : ~ 5 bar
Driving Pressure
Single Point Injection 2 – 3 bar
Carburetor : 20 – 50 Pa
Technology of Fuel Admission

11. Deeper Fluid Mechanics of Spray
GDI : 20 – 50 mm
Multi Poin Injection : ~ 200mm
Droplet size
Single Point Injection 100 – 300mm
Carburetor : 1 ~ 3 mm
Technology of Fuel Admission

12. Enhanced Performance of GDI
Carburetor
GDI engine
Diesel engine
MPI engine
A/F ratio
Fuel economy
MPI engines
power

13. Expected Better Design Variables in GDI Engine
High Compression ratio
Precise control over Air/Fuel distribution inside the combustion chamber
Improved volumetric efficiency

14. New Knowledge to Develop GDI Engines
Understand the behaviour of GDI engines under different operating and design conditions.
Generation of Optimal GDI configurations.
Study of homogeneous & stratified charge formation for each geometry.
Effect of Geometrical and Spray Parameters (a) Injector location, (b) Spray orientation, (c) Injection timing, (d) Droplet diameter, (e) Spray cone angle, (f) Type of spray, (g) Fuel temperature

15. Learning Through Experimentation

16. Experimental Development
A special purpose test rig was developed in IC engine laboratory of Mechanical Engineering Department, IIT Delhi, to investigate the characteristics of GDI engines.
A four stroke engine of Kawasaki Bajaj two wheeler is modified to work as GDI engine.
A mechanical driven petrol injector is placed in the cylinder head.
 Pistons with various geometries of cavities (Cylindrical, Conical & Spherical) are tested using a compression ratio of 9.3 at various speeds.
Following preliminary results are obtained.

17. GDI Engine Test Rig

18. Performance of SI Engine with High Pressure In Cylinder Injection
Carburettor Mode
Normally located Injector
Laterally located Injector

19. Promotion of Turbulence thru Piston Cavity
No Cavity
Cylindrical Cavity
Spherical Cavity
Conical Cavity

20. Eco-friendly Nature of GDI – HC Emissions
No Cavity
Cylindrical Cavity
Conical Cavity
Spherical Cavity

21. Eco-friendly Nature of GDI – CO Emissions
Cylindrical Cavity
No Cavity
Conical Cavity
Spherical Cavity

22. Eco-inimical Nature of GDI – NOx Emissions
Conical Cavity
Spherical Cavity
No Cavity
Cylindrical Cavity

23. Various Cylinder Configurations for GDI concept

24. Swirl based systems

25. Squish based GDI concepts

26. Tumble based GDI systems

27. Generation of Stratified A/F Mixture

28. Peripheral Technologies
Electronically controlled spray type injector - Hollow cone spray
Tumbling Port
Combustion Chamber Geometry
Hollow Cone Spray
Tumbling Flow
Piston Cavity

29. Spray Dynamics in GDI Engines

30. Fuel Injectors for GDI Engines
Currently the most widely used injector for GDI applications, is the single-fluid, swirl-type unit.
This uses an inwardly opening pintle, a single exit orifice and a fuel pressure, in the range of bar.
The liquid emerges from the single discharge orifice as an annular sheet that spreads radially outward to form an initially hollow-cone spray.
Pressure energy is transformed into rotational momentum that enhances atomization.

31. Fuel Spray in GDI Engines
The initial spray angle ranges between 25°-150° and the
Sauter Mean Diameter (SMD) varies from μm.
Surface roughness may, however, produce streams of fuel in the fuel sheet, resulting in formation of pockets of locally rich mixture.
The spray has a leading edge that penetrates away from the nozzle tip for about 50mm in less then 20ms.
A Toroidal vortex is also attached to the periphery.
The leading edge of the spray contains a separate sac spray.

32. Fuel Economy in GDI

33. Compactness of GDI Engine

34. Lowered HC Emissions in GDI Engine

35. Conclusions GDI Engine Technology is an obvious future choice.
Extensive CAD is essential for the development of GDI Engines.
CAD combined with experimental study will develop a better engine with faster development cycle.
More avenues for future research and development.