CAUSALITY DIAGRAM BASED SAFETY ANALYSIS OF MICRO TURBOJET ENGINE

An improved safety analysis based on the causality diagram for the complex system of micro aero-engines is presented.The study is examined by using the causality diagram in analytical failure cases due to rupture or pentration in the receiver of micro turbojet engine casing,and the comparisons are also made with the results from the traditional fault tree analysis.Experimental results show two main advantages：（1）Quantitative analysis which is more reliable for the failure analysis in jet engines can be produced by the causality diagram analysis;（2）Graphical representation of causality diagram is easier to apply in real test cases and more effective for the safety assessment.

Effects analysis on catalytic combustion characteristic of hydrogen/air in micro turbine engine by fuzzy grey relation method

In order to enhance catalytic combustion efficiency, a premixed hydrogen /air combustion model of the micro turbine engine is established under different excess air ratio, inlet velocity and heat transfer coefficient. And effects of inlet velocity, excess air coefficient and heat transfer coefficient on the catalytic combustion efficiency of the hydrogen have been analyzed by the FLUENT with CHEMKIN reaction mechanisms and the fuzzy grey relation theory. It is showed that inlet velocity has a more intuitive influence on the catalytic combustion efficiency of the hydrogen. A higher efficiency can be obtained with a lower inlet velocity. The optimum excess air coefficient is in the range of 0.94 to 1.0, the catalytic combustion efficiency of the hydrogen will be declined if the excess air coefficient exceeded 1.0. The effect of heat transfer coefficient on the catalytic combustion efficiency of the hydrogen mainly embodies in the case of the excess air coefficient exceeded 1.0, however, the effect will be declined if the heat transfer coefficient exceeded 4.0. The fuzzy grey relation degrees of the inlet velocity, heat transfer coefficient and excess air coefficient on the catalytic combustion efficiency of the hydrogen are 0.640945, 0.633214 and 0.547892 respectively.

EFFECT OF THE CONTROLLED ROLLING CONTROLLED COOLING ON STRENGTH AND DUCTILITY OF THE BAINITE MICRO ALLOYED ENGINEERING STEEL

The continuous cooling transformation of hot deformation austenite austenite of test steel and the effect of different processing schedules of controlled rolling and controlled cooling on the strength and ductility have been studied. The theory and the experiment base are presented for controlled rolling and controlled cooling of the SBL micro alloyed engineering steel.

Performance analysis of a 2-stroke micro free-piston swing engine

The micro free-piston swing engine （MFPSE） is a new structure, free-piston internal combustion engine. The dynamic model integrated MFPSE with a power generator and thermodynamic models in compression, power and scavenge processes based on the open thermodynamic systems were presented. A simulation was executed at given geometric parameters and initial conditions. The results manifest that the working principle of MFPSE is feasible.

Design and fabrication of alumina micro reciprocating engine

Microengines are regarded as the potential replacements for batteries.Aimed at the unsatisfactory thermal property of silicon used in the combustion chambers,ceramics are chosen as the construction material in this paper.The fabrication process where alumina has been chosen as the microengine material is discussed.Vigorous FEA has been carried out,and it is found that the material satisfies the stress and deformation requirements of the design.Then the alumina fabrication process is described.Soft reusable polydimethylsiloxane(PDMS)moulds are produced from SU-8 resist masters,and alumina microengine parts are produced using the PDMS moulds.Images of the ceramic components show that the fabrication satisfies the design requirements.

Research on windmill starting characteristics of MTE-D micro turbine engine

Micro turbine engine （MTE） is an important kind of propulsion system for miniature unmanned aircraft or missiles, because of its better high-speed performance （than propeller propulsion） and higher propulsion efficiency （obviously than rockets）. Windmill start is a common air-starting mode used in micro turbine engine. The windmill starting characteristics are important to the practical use of micro turbine engine. In this paper, the windmill starting characteristics research for a 12 cm diameter （MTE-D） micro turbine engine is carried out by experiment and numerical simulation. The characteristic of rotor mechanical losses at low-speed condition is stud- ied, and the engine common working line of windmill starting process is obtained. Based on the engine windmill characteristics, the propane ignition characteristics under different inflow conditions are researched, and the envelope of propane ignition and propane flameout is determined. The experimental research of fuel supply and ignition characteristics is completed, and the envelope of fuel supply and ignition is obtained. The windmill stage, propane ignition stage, fuel ignition stage and acceleration process from idling-speed to 80% full speed of MTE-D micro turbine engine is optimized, and the optimization windmill starting parameters are collected. The successful wind-mill starting experiment under this condition with engine speed up to 80% full speed indicates that these starting parameters are reasonable. All the starting parameters of MTE-D micro turbine engine obtained in this work are dimensionless parameters, and the conclusions obtained in this study have some reference to other micro turbine engines with the similar structural form and starting process.

Redesign of an 11 cm-diameter Micro Diffuser

In order to improve the performances of an 11 cm-diameter turbine engine,this article suggests to substitute a new-style micro diffuser redesigned based on a new concept for the traditional diffuser having poor performances. The new diffuser comprises integral blades and splitters,which are taken for a series of ducts in designing. This article investigates the effects of the cross-section area distribution along the flow path on the redesigned diffuser＇s performances. Having furnished with the new diffuser in place of the original vaned one,the 11 cm-diameter prototype engine is tested on the rig for its performances. CFD and experiments have shown that the improved diffuser with the unchanged original size has gained excellent performance parameters of pressure coefficient over 0.65 and total pressure recovery coefficient over 0.9. Equipped with the redesigned micro diffuser,the engine increases the thrust by 11% and decreases the specific fuel consumption by 9%.

Numerical Study of Effect of Compressor Swirling Flow on Combustor Design in a MTE

An effect of the swirling flow on the combustion performance is studied by the computational fluid dynamics(CFD) in a micro-gas turbine with a centrifugal compressor, dump diffuser and forward-flow combustor. The distributions of air mass and the Temperature Pattern Factor(as: Overall Temperature Distribution Factor-OTDF) in outlet are investigated with two different swirling angles of compressed air as 0° and 15° in three combustors. The results show that the influences of swirling flow on the air distribution and OTDF cannot be neglected. Compared with no-swirling flow, the air through outer liner is more, and the air through the inner liner is less, and the pressure loss is bigger under the swirling condition in the same combustor. The Temperature Pattern Factor changes under the different swirling conditions.