Laser Ignition for Internal Combustion Engines

PRESENTED BY , GUIDED BY , HINGMIRE ABHISHEK A. PRADNYA KOSBE(3228)

Why Laser Ignition?

• Regulations on NOx emissions are pushing us toward leaner air/fuel ratios (higher ratio of air to fuel). – These leaner air/fuel ratios are harder to ignite and require higher ignition

energies. Spark plugs can ignite leaner fuel mixtures, but only by increasing spark energy. Unfortunately, these high voltages erode spark plug electrodes so fast, the solution is not economical. By contrast, lasers, which ignite the air-fuel mixture with concentrated optical energy, have no electrodes and are not affected.

• 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. – Laser spark plug ignition system will require less power than traditional spark

plugs, therefore outlasting spark plugs. • 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.– Lasers can be focused and split into multiple beams to give multiple ignition

points, which means it can give a far better chance of ignition.

Why Laser Ignition? (continued)

• Lasers promise less pollution and greater fuel efficiency, but making small, powerful lasers has, until now, proven hard. To ignite combustion, a laser must focus light to approximately 100 gigawatts per square centimeter with short pulses of more than 10 millijoules each.

• Japanese researchers working for Toyota have created a prototype laser that brings laser ignition much closer to reality. The laser is a small (9mm diameter, 11mm length) high powered laser made out of ceramics that produces bursts of pulses less than a nanosecond in duration.

• The laser also produces more stable combustion so you need to put less fuel into the cylinder, therefore increasing efficiency.

• Optical wire and laser setup is much smaller than the current spark plug model, allowing for different design opportunities.

• Lasers can reflect back from inside the cylinders relaying information such as fuel type and level of ignition creating optimum performance.

• Laser use will reduce erosion.

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).

Laser Ignition System for an Internal Combustion Engine

Laser ignition will replace the spark plug seen in current gasoline engines.

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.

– From the point of view of components development, the main goal is the creation of a laser system which meets the engine-specific requirements. Basically, it is possible to ignite mixtures with different types of lasers.

Experimental Setup

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:

Result and Discussion

• Laser ignition of hydrogen/air mixtures.

• Laser ignition of biagos/air mixtures.

• Shockwave and flame kernel development by Schlieren photography.

• Engine tests:

a. Optics deposits and self-cleaning effect.b. Laser self-cleaning with deposits caused by the combustion process.c. Laser self-cleaning effect with worst case deposits. d. Properties of the optical window.

Advantages

• A choice of arbitrary positioning of the ignition plasma in the combustion cyinder.

• Absence of quenching effect by the spark plug electrodes.

• Effective ignition of leaner mixture at lower combustion temperature.

• Less NOx emissions.

• No erosion effects in case of spark plug.

• Lifetime of laser ignition system expected to be significantly longer than that of conventional spark plug.

• High load ignition pressure possible.

Advantages (continued)

• High power output, hence higher efficiency.

• Precise ignition timing possible.

• Exact regulation of the ignition energy deposited in the iginition plasma.

• Multipoint ignition is possible.

• Shorter ignition delay time and shorter combustion time .

• Fuel lean ignition possible.

Disadvantages

• High system costs.

• Concept proven , but no commercial system available yet.

Conclusion

• An enhanced ignition sourse can make a strong contribution to sustainability in internal combustion engines.

• It was found in the test with hydrogen that with higher initial pressure the minimum pulse energy for ignition decreases, same behaviour was found for methane.

• Fuel-lean biogas/air mixture exhibit a slower combustion process which results in lower peak pressure and flame emission compared to methane-air of same air to fuel ratio.

• Applicability of the laser induced ignition as a future ignition system for combustion engines with spray-guided combustion process could be proved with basic research.

• It is possible to ignite mixtures with different laser systems.

THANK YOU