Robert Lundberg

Alumina/alumina composite with a porous zirconia interphase —Processing, properties and component testing

Abstract Novel oxide ceramic composites (NOCC) was a four year European programme aimed to develop an all-oxide ceramic matrix composite (CMC) and processing route, carry out a characterisation programme on the material and demonstrate it in a combustor rig at conditions representative of a gas turbine engine. The fibre used was a single crystal monofilament (Saphikon Inc.), which was chosen for its temperature and creep resistance. Alumina (aluminium oxide) was chosen for the fibre and matrix, and zirconia as a weak interphase coating on the fibre. Tape casting followed by hot pressing was chosen as the manufacturing route for the composite, with hot isostatic pressing (HIPping) as an alternative densification process. Cross-ply material with fibre volume fractions of around 30% was found to have moderate strength (100–130 MPa), but retained composite properties at elevated temperatures and after extended periods at elevated temperatures (1000 h at 1400°C). In addition, the material was found to withstand thermal cycling (>1300 cycles to 1200°C), retaining its as-fabricated properties. Computational fluid dynamics (CFD) calculations were carried out for a combustor rig, and a CMC tile was designed. The temperatures, stresses and strains in the tile were predicted using finite element (FE) analysis and combustor tiles were manufactured. A tile was successfully tested in a rig at temperatures >1260°C and up to 46 cycles. Some of the issues that remain to be addressed with the material and manufacturing method are cost, delamination during manufacture, and consistency. It is likely that, due to the high cost of the fibre and relatively modest usable strength, the material will remain as a model material. The promising results on long term static and cyclic ageing proves that the concept of an all-oxide CMC is valid and points the way to future development of this class of material.

Near net shape production of monolithic and composite high temperature ceramics by hot isostatic pressing (HIP)

Abstract Improved properties of high temperature ceramics in general are achieved by compositional and processing research and development—compatible with sintering and forming needs. Pressure can be used to increase the driving force for densification and with hot isostatic pressing (HIP) the form can be closely controlled, even of complex shaped parts, like turbine wheels. Recent development within the EUREKA-AGATA hybrid electric car gas turbine project shows that improved high temperature material properties can be achieved, while at the same time fabricating components like combustion parts and turbine wheels, to near-net-shape. For such components a highly uniform green powder body is desired. Combined with a type of encapsulation during HIP, which does not create shear stresses at the surface of the green body during the shrinkage/sintering to full density, but at the same time prevents penetration into the body, optimal near-net-shape results can be achieved. Recent studies, e.g. by TEM, have confirmed that some encapsulation glass constituents can form new compounds with silicon nitride, at the very surface, which appear to help develop these desired characteristics. Non-homogeneous and non-isotropic ceramics, like fiber reinforced composites, may be fabricated using rigid, shape controlling tools on one or several sides. Particularly for large (and curved) panels such use of a hot isostatic press can be an advantage.

Fibre reinforced silicon nitride composites

Abstract Three possible processing routes to obtain silicon nitride reinforced with continuous fibres are identified and demonstrated. Slip-infiltrated, HIed carbon fibre reinforced material, slip-infiltrated, SiC fibre reinforced nitrided Si3N4, and polysilazane solution infiltrated pyrolysed composites with SiC fibres have been successfully fabricated. Possible fibre/matrix reactions are discussed on the basis of scanning electron microscopy observations and the bend fracture behaviour of the composites. All materials exhibited non-brittle fracture and are thus potentially interesting composites for further development.

Development of Ultra High Temperature Ceramic Composites for Gas Turbine Combustors

All-oxide ceramic composites as a material with potential for long life-time applications at temperatures in the 1400–1600°C range in combustion environments were studied. The properties of available polycrystalline and single crystal oxide fibres were summarised. The literature on stable weak interfaces in all-oxide composites was reviewed. Composites with single crystal fibres, a polycrystalline matrix of the same material as the fibres, and a compatible high temperature stable weak oxide interphase was suggested to be the most promising approach. Recent progress in an ongoing European project aiming at development, scale-up and property evaluation of all-oxide composites is reported. The composite will be applied to a simple prototype combustor tile and tested in a combustor rig.© 1997 ASME

Ceramic Component Development for Agata

The European EUREKA project, EU 209, also known as AGATA (Advanced Gas Turbine for Automobiles), is a programme dedicated to the development of three critical ceramic components — a catalytic combustor, a radial turbine wheel and a static heat exchanger — for a 60 kW turbogenerator in a hybrid electric vehicle. These three components, which are of critical importance to the achievement of low emissions and high efficiency, have been designed, developed, manufactured and tested as part of a full scale feasibility study. AGATA is a joint project conducted by eight commercial companies and four research institutes in France and Sweden. This paper outlines the main results of the AGATA project with special emphasis to the development of ceramic components.Copyright

Progress on the AGATA Project: A European Ceramic Gas Turbine for Hybrid Vehicles

The European EUREKA project EU 209 or AGATA - Advanced Gas Turbine for Automobiles is a program dedicated to the development of three critical ceramic components; i. catalytic combustor, ii. radial turbine wheel, iii. static heat exchanger, designed for a 60 kW turbogenerator hybrid electric vehicle. The objective is to develop and test the three components as a full scale feasibility study with an industrial perspective. The AGATA partners represent car manufacturers as well as companies and research institutes in the turbine, catalyst and ceramic material fields in France and Sweden. The program has been running since early 1993 with good progress in all three sub-projects.The turbine wheel design is now completed. FEM calculations indicate that the maximum stress occur during cold start and is below 300 MPa. Extensive mechanical testing of the Si3N4 materials from AC Cerama and C&C has been performed.The catalytic combustor operates uncooled at 1350°C. This means a severe environment for both the active catalyst and the ceramic honeycomb substrates. Catalysts with high activity even after aging at 1350°C have been developed. Ceramic honeycomb substrates that survive this temperature have also been defined. The catalytic combustor final design is ready and the configurations which will be full scale tested have been selected.The heat exchanger will be a ceramic recuperator with 90 % efficiency. Both a tube concept and a plate concept have been studied. The plate concept has been chosen for further work. Sub-scale plate recuperators made of either cordierite or SiC have been manufactured by C&C and tested.Copyright

HIPed Silicon Nitride Components for AGATA — A European Gas Turbine for Hybrid Vehicles

The European EUREKA project, EU 209, otherwise known as AGATA (Advanced Gas Turbine for Automobiles), is a programme dedicated to the development of three critical ceramic components — a catalytic combustor, a radial turbine wheel and a static heat exchanger — for a 60 kW turbogenerator in an hybrid electric vehicle. These three components, which are of critical importance to the achievement of low emissions and high efficiency, have been designed and developed and will be manufactured and tested as part of a full scale feasibility study. AGATA is a joint project conducted by eight commercial companies and four research institutes in France and Sweden. Silicon nitride ceramics play an important role both in the development of the catalytic combustor and for the radial turbine wheel. This paper outlines the main results of the AGATA project with special emphasis to the development of HIPed Si3N4 combustor and turbine wheel. AC Cerama has developed a HIPed Si3N4 material designated CSN 101. This material has been selected for the catalytic combustor afterburner as well as for the radial turbine wheel. Mechanical properties of the CSN 101 Si3N4 have been found to be at the level of the best available high temperature Si3N4 materials. A new glass encapsulation technique using an interlayer between the glass and the silicon nitride has been shown to give material with excellent strength and creep resistance with as-HIPed surface finish.Copyright

HIPed Silicon Nitride Components for AGATA — Properties and Evaluation

The European EUREKA project, EU 209, otherwise known as AGATA (Advanced Gas Turbine for Automobiles), is a programme dedicated to the development of three critical ceramic components — a catalytic combustor, a radial turbine wheel and a static heat exchanger — for a 60 kW turbogenerator in an hybrid electric vehicle. These three components, which are of critical importance to the achievement of low emissions and high efficiency, have been designed, developed, manufactured and tested as part of a full scale feasibility study. AGATA is a joint project conducted by eight commercial companies and four research institutes in France and Sweden. Silicon nitride ceramics play an important role both in the development of the catalytic combustor and for the radial turbine wheel. This paper outlines the main results of the AGATA project with special emphasis to the development of HIPed Si3N4 combustor and turbine wheel. AC Cerama has developed a HIPed Si3N4 material designated CSN 101. This material has been selected for the catalytic combustor afterburner as well as for the radial turbine wheel. Mechanical properties of the CSN 101 Si3N4 have been found to be at the level of the best available high temperature Si3N4 materials. A new glass encapsulation technique using an interlayer between the glass and the silicon nitride has been shown to give material with excellent strength, oxidation resistance and creep resistance with as-HIPed surface finish.Copyright

AGATA: A European Ceramic Gas Turbine for Hybrid Vehicles

The European EUREKA project EU 209 or AGATA - Advanced Gas Turbine for Automobiles is a program dedicated to the development of three critical ceramic components; i. catalytic combustor, ii. radial turbine wheel, iii. static heat exchanger, designed for a 60 kW turbogenerator for a hybrid electric vehicle. The objective is to develop and test the three components as a full scale feasibility study with an industrial perspective. The AGATA partners represent car manufacturers as well as companies and research institutes in the turbine, catalyst and ceramic material fields in France and Sweden.Copyright

Development of Silicon Nitride Based Matrices

A feasible way to produce SiC long fibre reinforced Si3N4 is by vacuum infiltration of Si3N4 slurry followed by reaction bonding of the matrix. To minimize degradation of the fibres the nitridation reaction has to take place at moderate temperatures. In the present work a number of Si3N4-matrices processed by a modified RBSN technique and mixed with ZrO2-additives to optimize the nitridation cycle will be discussed. The results show that ZrO2 has a remarkably accelerating effect on the nitridation. It is thus possible to decrease the exposure of SiC fibres to high temperatures.