Robert Jakubowski

Modeling and analysis of jet engine with cooling turbine

Abstract The problems of the turbojet engines with a cooling turbine modelling are discussed in the paper. The cooling systems of the contemporary jet engines are briefly described in the first part of the paper. Than the models of various turbine, cooling systems are presented and discussed. The main scope of the paper is the turbine cooling system consisted of internal convection cooling and external film cooling of turbine blades. This cooling system is commonly used in contemporary military and civil turbojet engines. The model of the internal-external cooling turbine incorporated in the overall jet engine model is presented and discussed. Some simplifying assumptions are discussed. Then the results of the jet engine calculation taking into account the proposed model are presented in the tables. The results are compared with results obtained by simple model of the jet engine with cooling turbine. The simple model is commonly applied for 1D turbojet engine analysis. Based on this analysis, some aspects of the turbojet engine calculation with reference to different models applied for description of the turbine cooling process are presented and discussed. The analysis allowed formulating some conclusions, which are presented in the final part of the paper. One of them is that proposed model of cooling turbine allows to calculate of coolant mass flow, while the simple models of cooling turbine require the assumption of coolant mass. By this way the calculation results accuracy by the use of simple model, strictly depend on the proper assumption of coolant mass flow.

TWO-COMBUSTOR TURBOFAN ENGINE PERFORMANCE ANALYSIS

A conception of a two-combustor turbofan engine is the main scope of this paper. At the beginning, the problems of turbofan engines development are briefly discussed as a background of this work. In this part the turbofan engines innovation activities are presented. It is mentioned the engine’s innovations consists of many aspects but some important ones are: lowering of production operation cost, maintenance, reduction of noise and exhaust gases emission while engine reliability should stay on the same level or event increase. Next, the conception of turbofan engine with two combustors is presented in this context. Some positive aspects for environment, production and maintenance of such engine are discussed. Then the thermodynamic cycle of two-combustor engine is presented and analysed. On this basis, the engine numerical model is prepared. Next, some information about the model simplifications and calculations done to determine performance of the engine is presented. Then the results of the simulation calculations of the engine performance are presented and discussed. The relationship of engine thrust and specific fuel consumption vs. engine flight conditions are shown. Based on the results there were discussed the advantages and disadvantages of two combustors engine as an airplane propulsion are specified. The conclusions are formulated and presented in the last part of the paper.

ANALYSIS OF CHOSEN FUELS INFLUENCE ON TURBOPROP ENGINE WORK PERFORMANCE

The analysis of work parameters of a turboprop engine fuelled by various fuels was done in the paper. The turboprop engine model was presented in the beginning. The main feature of this model is description of the flow in the engine as semi-perfect gas model. By the way, the change of fumes chemical composition influence the gas properties as heat constant and isentropic index are determined. Next energy balance of a compressor and turbine was analysed and turbine pressure drop was evaluated. Finally, engine output power was determined. It was done for selected fuels, which could be applied in the aero engines. The results of analyse were presented in the tables and charts and discussed. Summary of the test results with the results for contemporary applied fuel allows drawing the conclusions about the turboprop engine performance change by various fuel application. Main of them refers to the point that higher combustion heat value of fuel and higher heat constant of fumes cause better engine work conditions By this way the hydrogen seems to be perspective fuel of future, because its combustion heat value is three times JET A-1 and by this way it is possible the engine fuel consumption will be lower.

Analysis of turbofan engine design modification to add inter-turbine combustor

An inter turbine combustion is one of modern direction of turbofan engine cycle modification. It is possible to reduce gas temperature in high-pressure turbine inlet section and reduce NOX emission by an additional combustor placed between high and low pressure turbines. The analysis of engine cycle modification and its performance are a scope of many scientific investigations, but it is not any work about engine dimension change due to cycle modification. By these way problems of two combustor engine components and dimensions, change with comparison to conventional turbofan engine is a goal of this work. The structure of a turbofan engine with inter turbine combustor is shown and results of evaluation temperature and pressure in specified engine cut sections are presented and discussed. Then the gas density is calculated and by mass continuity equation application, the specified cross section areas are determined. The results of two-combustor turbofan engine are compared with conventional high bypass turbofan engine. The comparison of engines parameters allow to predict how engine components should be modified in two-combustor turbofan when the base of modification is classic turbofan engine. The analyse contain determination of compressor and turbine stage numbers, prediction of areas of cross section and diameters in specified engine sections and overall engine axial dimensions. The results are used to formulate conclusion about the turbofan engine structure modification by additional combustor implementation between turbines.