Takayuki Inohara

High Peak Power, Passively

The compact (electric spark plug size), diode-pumped, passively Q-switched Nd:YAG/Cr4+:YAG microlaser was developed for ignition of engines. Output energy of 2.7 mJ per pulse and 11.7 mJ per four-pulse train with a pulsewidth of 600 ps and an M 2 value of 1.2 were obtained at a pump duration of 500 ¿s. The optical-to-optical conversion efficiency was 19%. Brightness of the microlaser was calculated as 0.3 PW/ sr-cm2 and optical power intensity was calculated as 5 TW/cm2 at the focal point of ignition. The enhanced combustion by the microlaser ignition was successfully demonstrated in a constant-volume chamber at room temperature and atmospheric pressure. The cross section area of a flame kernel generated by laser ignition is 3 times larger than that by a conventional spark plug at 6 ms after ignition in a stoichiometric mixture (A/F 15.2) of C 3H 8/air, even though ignition energy of the laser is 1/3 of that of the spark plug. Hundred percent ignition was successfully demonstrated in a lean mixture of A/F 17.2 by laser ignition, where electric spark plug ignition failed.

Q

3mJ per pulse with 1.2ns pulse width, passively Q-switched Cr:YAG/Nd:YAG micro-laser was developed for ignition of engines. The enhanced combustion by using the micro-laser igniter was successfully demonstrated in comparison with a spark plug.

-switched Microlaser for Ignition of Engines

Recently in consideration of the problem of protecting the global environment and preserving fossil resources, the research and development of new clean vehicles driven by clean energy sources, such as electricity, fuel cell, etc., has been progressing worldwide. However it is difficult to replace all conventional gasoline vehicles to clean vehicles immediately, because they still have several hurdles to get over, costs of the clean vehicles and the energy sources, range between refuelling, the availability of refuelling or recharging stations, vehicle performance, fuel cell lifetime, etc. Therefore the improvement of the efficiency of conventional internal combustion gasoline engines, and the reductions of CO2 and harmful pollutant emissions have become more important today. A laser has been discussed widely as one of the promising alternatives for an ignition source of the next generation of efficient internal combustion engines (Hickling & Smith, 1974; Dale et al., 1997; Phuoc, 2006). Laser ignition can change the concept of ignition innovatively and has many advantages over conventional electric spark plug ignition. Figure 1 shows the schematics of combustion engines ignited by (a) an electric spark plug and a laser (b), (c).

High Peak Power, Passively Q-switched Cr:YAG/Nd:YAG Micro-Laser for Ignition of Engines

Spark plug-size, passively Q-switched Cr:YAG/Nd:YAG micro-laser was developed for ignition of engines. Optical power intensity of >5TW/cm2 was obtained at the focal point and the enhanced combustion for leaner gas mixture was realized.

Micro-Solid-State Laser for Ignition of Automobile Engines

A system with “Variable Valve Timing –intelligent by Electric motor (VVT-iE)” has been newly developed to realize requirements for lower fuel consumption and lower exhaust gas emission, as well as higher performance. The system has initially been adopted for the intake valve train of Toyota’s new 4.6 and 5.0 litter V8 SI engine. The VVT-iE is composed of a cam phasing mechanism connected to the intake camshaft and a brushless motor integrated with an intelligent driver unit. The developed motor-actuated system is completely free from operating limitations by conventional hydraulic VVT. This new system leads to advantages in reducing cold HC and also achieves further reductions in fuel consumption.

Compact, high peak power, passively Q-switched micro-laser for ignition of engines

A 0.3PW/sr-cm2, high brightness passively Q-switched Cr:YAG/Nd:YAG micro-laser was tested for ignition of a real automobile engine. Stable engine operation was demonstrated with an ignition optical energy of 2.3mJ, lowest ever reported.