This document summarizes a technical seminar on laser ignition for internal combustion engines. It begins by defining lasers and their properties of spatial and temporal coherence. It then explains how lasers work through population inversion and stimulated emission. The document outlines different types of lasers and describes how laser ignition would replace standard spark plug ignition. It details laser ignition testing on a research engine and discusses advantages like increased efficiency and lifetime compared to spark plugs, as well as current disadvantages like high cost. The conclusion states that laser ignition allows flexibility in ignition location and could improve performance over spark plugs.

1. Technical Seminar
On
Laser Ignition for
Internal Combustion Engines
By
K.SAIKIRAN
(17281A0332)

2. What is a Laser?
• A LASER is a device that emits electromagnetic radiation through a process of optical
amplification based on the stimulated emission of photons.
• The term ‘LASER’ is an acronym for Light Amplification by Stimulated Emission of Radiation
• The emitted laser is unique in its high degree of spatial and temporal coherence.
• Spatial Coherence means a fixed phase relationship between the electric fields at different
locations across the beam. Typically it is expressed through the output being a narrow beam
which is diffraction-limited, also known as a "pencil beam." Laser beams can be focused to very
tiny spots, achieving a very high irradiance.
• Temporal coherence means a strong correlation between the electric fields at one location, but
different times.
Electric field distribution
around the focus of a
Gaussian laser beam with
perfect spatial and temporal
coherence.
A laser beam with
high spatial
coherence, but poor
temporal coherence
A laser beam with
poor spatial
coherence, but high
temporal coherence.

3. Lasers are monochromatic, meaning they are very orderly forms of light that have only one wavelength
and one direction.
It all starts with the electrons.
By sending energy to a system we can achieve what is known as population inversion.
This means that there are more electrons in the excited states than those in the lower energy states.
As one electron releases energy (a photon), the other electrons strangely seem to communicate with
each other and also begin releasing photons.
This chain reaction of releasing photons is called stimulated emission.
So, by having:
- Population Inversion
- Stimulated Emission
- Strategic Planting of Mirrors
We get:
- Monochromatic , Directional, and Coherent light.
How does a Laser work?

4. Types of Lasers
• Gas
– A Helium-Neon (HeNe) used mostly for holograms such as laser printing.
• Chemical
– LASERS that obtain their energy through chemical reactions. Used mostly for weaponry.
• Dye
– Usually it is in the form of a liquid solution. Used in medicine, astronomy, manufacturing, and more.
• Solid-state
– Uses a gain medium that is a solid (rather than a liquid medium as in dye or gas lasers). Used for
weaponry
• Semiconductor
– Also known as laser diodes, a semiconductor laser is one where the active medium is a semiconductor
similar to that found in a light-emitting diode.
– Applications include telecommunication and medicine

5. Standard Spark Plug Ignition in an Internal
Combustion Engine
• Current internal combustion gasoline engines use spark plugs to ignite the
air/fuel mixture in each cylinder (located at the top of the combustion
chamber).

6. Laser Ignition System for an Internal
Combustion Engine
Laser ignition will replace the spark plug seen in current gasoline
engines.

7. Laser Ignition System for an Internal
Combustion Engine (continued)
• Laser Testing:
– A one-cylinder research engine was used as a test engine.
– The research engine was equipped with a four-valve DOHC
cylinder head with a spray-guided combustion system of AVL List GmbH.
– Engine test runs were carried out with two different approaches:
• First, a plane window was inserted into the cylinder head of the
engine. A focusing lens was placed in front of that window in order to
focus the laser beam down into the combustion bomb (“separated
optics”).
• Second, a more integrated window was deployed. A lens-like curvature
was engraved dire
• ctly into the window. By using such a special window, no further lens
was required (“combined optics”).

8. How Laser Ignition Works
• The laser ignition system has a laser transmitter with a fiber-optic cable powered by the car’s
battery. It shoots the laser beam to a focusing lens that would consume a much smaller space
than current spark plugs. The lenses focus the beams into an intense pinpoint of light, and when
the fuel is injected into the engine, the laser is fired and produces enough energy (heat) to ignite
the fuel.
• Below is a diagram of the laser arrangement:

9. Why Laser Ignition?
• Regulations on NOx emissions are pushing us toward leaner
air/fuel ratios (higher ratio of air to fuel).
• Natural gas is more difficult to ignite than gasoline due
to the strong carbon to hydrogen bond energy.
– Lasers are monochromatic, so it will be much easier to ignite
natural
gases and direct the laser beam to an optimal ignition
location.
• Because of the requirement for an increase in ignition energy,
spark plug life will decrease for natural gas engines.
• Ignition sites for spark plugs are at a fixed location at the top of
the combustion chamber that only allows for ignition of the
air/fuel mixture closest to them.

10. Advantages:
• It does not require maintenance to remove carbon
deposits because of its self-cleansing property.
• High load / ignition pressure possible => increases in
efficiency.
• Ignition time is possible.
Disadvantages:
• High system cost.
• Concept proven, but not commercial system
available yet.

11. Conclusion:
Laser ignition system allows almost free choice of
the ignition location within the combustion chamber,
even inside the fuel spray.
At present, a LASER ignition plug is very expansive
compared to a standard electric spark plug ignition
system.

12. THANK YOU