Three low NOx combustors, i.e. a lean premixing combustor, a rich-lean two stage combustor and a lean diffusion flame combustor, were tested in order to find out a suitable combustion concept for an automotive ceramic gas turbine combustor. The prevaporization-premixing lean combustion was proposed as the most promising candidate to meet Japanese 10 mode regulation for gasoline passenger car. The required conditions for the uniform premixture formation in the prevaporization-premixing tube were achieved by a fine droplet size atomizer and by means of swirl and turbulent generator. Air ratio range, air loading and other dimension criteria in the lean primary combustion zone were also proposed in the present paper.

Two aspects of reliability assurance are discussed. First, This paper deals with the reliability design of the emissions under transient conditions. The optimization was made from the simulation results of the relationship between the response of the variable combustor geometry to follow load changes and the resulting exhaust emission levels. The load variation pattern used in this investigation was that of the Japanese 10-mode regulation. Second, this paper describes the validity of the reliability design prepared for the ceramic liner of the combustor. A service life prediction was made for the liner on the basis of stress analysis results and fatigue parameters.

A low emission combustor for a 100kW ceramic gas turbine, which is intended to meet Japanese emission standards for gasoline passenger cars, has been designed and subjected to initial performance tests. A prevaporization-premixing combustion system was chosen as the most suitable system for the combustor. The detailed combustor design, including the use of ceramic components and fuel injectors, was pursued taking into account the allowable engine dimensions for vehicle installation. In the initial performance tests conducted at a combustor inlet temperature of 773K, a low NOx level was obtained that satisfied the steady state target at this temperature level.

A low emission combustor, which uses a prevaporization-premixing lean combustion system for the 100 kW automotive ceramic gas turbine (CGT), has been subjected to performance tests. Now a second combustor prototype (PPL-2), which incorporates improvements intended to overcome a flashback problem observed in an initial combustor prototype (PPL-1), is tested. The PPL-2 has been designed and built, so that it will substantially expand the stable combustion range. The improvement is accomplished by increasing the air distribution ratio in the lean combustion region to avoid flashback, providing a uniform flow velocity through the throat area and also by diluting the boundary layer so as to suppress flashback. Test results of the PPL-2 combustor show that it expands the flashback limit without affecting the blow out limit and is able to cover the stable combustion range need for the 100kW CGT.

In recent years, magnesium alloys are attracting attention from aircraft and automotive industries because of their low density, high speci c strength and high damping capacity. However, magnesium alloys suffer from low ductility at room temperature. The improvement of ductility in AZ91D alloy through a new thermo-mechanical treatment (TMT) process was reported. This TMT process is based on simple uniaxial hot pressing in atmosphere. Uniaxial hot pressing was carried out at 673 K up to 67% compressive strain. After the hot pressing, the specimen was held isothermally at 673 K for various times. Hot pressed specimens were aged at 473 K. The specimen isothermally held for 3.6 ks showed tensile strength of 358 MPa and elongation to failure of 9.6%. Microstructural observation revealed that both high strength and ductility in AZ91D alloy were caused by the homogeneous distribution of ne intermetallic precipitates inside grains.