Low cost, and low weight, turbojet engines for RPV applications are being developed by the Aerospace Technical Centre in Brazil. A simple turbojet developing 320 N thrust is described which has been designed, manufactured and tested, succesfully matching its performance goals. Another turbojet developing 1000 N thrust has been designed and is currently being manufactured. This report describes the design philosophy adopted.

The implementation of new technology in the gas turbine industry is accelerating at a rate which demands increasing specialisation by its engineering design staff. Simultaneously, this industry has been adopting concurrent engineering practices to reduce product lead-time. Accordingly, the industry now requires its engineers to acquire competence in a wide range of technological disciplines together with a thorough understanding of the demands of design optimisation for the whole engine. Against this background, educational providers must respond to these increasing demands with teaching programmes that enable a more rapid and deeper understanding of a very complex product. The ambition of the teacher, however, to prepare the student will continue to be limited by time constraints within lecture courses. Hitherto, this has normally resulted in class worked examples which are necessarily narrow in scope and confined to a limited range of design cases. To overcome these limitations, a portfolio of multimedia computer programs has been developed specifically for rapid and relevant learning purposes. Each is structured to facilitate in-depth understanding of the key interactions between aerodynamics, thermodynamics and mechanical integrity needed in gas turbine design and performance assessment. This paper describes an interactive teaching method for turbine design optimisation using only the multimedia turbine design and performance module. Through the example of a case study, the preliminary design of a high pressure and low pressure turbine combination is undertaken initially by hand. This first pass design leaves substantial scope for design optimisation through a series of workshops using only the software. Final design recommendations are subsequently based on comprehensive tutor led but fully interactive discussion. Particular emphasis is placed on the impact of design decisions on both the various technology issues and on the performance of other engine components.

The implementation of new technology in the gas turbine industry is accelerating at a rate which demands increasing specialisation by its engineering design staff. Simultaneously, this industry has been adopting concurrent engineering practices to reduce product lead-time. Accordingly, the industry now requires its engineers to acquire early competence in a wide range of technological disciplines. In addition, the individual must have a thorough understanding of the impact of component design decisions on both other components and on the engine as a whole. Against this background, gas turbine educational providers must respond to these increasing demands with teaching programmes that facilitate a faster and deeper understanding of this very complex product. The ambition of the teacher, however, to adequately prepare the student will continue to be limited by time constraints within lecture courses. Hitherto, this has normally resulted in class worked examples which are necessarily narrow in scope and confined to a limited range of design cases. This paper describes a teaching methodology which is structured to facilitate in-depth understanding of the key interactions between aerodynamics, thermodynamics and mechanical integrity arising in axial compressor design optimisation. This is achieved interactively through a combination of lectures, a hand worked multistage preliminary compressor design, a series of personal computer based design optimisation workshops and a final collective design assessment.

The current drive for low specific fuel consumption (SFC) has resulted in increasing the bypass ratio (BPR) to improve the propulsive efficiency. Conventional high BPR engines face several practical limits when augmenting BPR i.e. an increase in the number of low-pressure turbine stages and in weight of the engine. This paper is an account of an investigation of the tip-turbine driven propulsion fan (TTDPF) as one potential solution. In particular, the TTDPF is considered as the main propulsion source for the Blended Wing Body Aircraft (BWB) developed by the College of Aeronautics at Cranfield University. The concept combines a gas generator(s) in the fuselage in combination with three or four over-wing mounted propulsion fans driven by tip-turbines. A double pass single stage configuration for the tip-turbine is assessed. This comprises two partial admission segments sharing the same circular annulus. The paper considers some special features of this novel engine concept. For example, the complex ducting (volutes) between the two passes and the aerodynamic arrangement of a two-pass turbine with a single rotor are investigated. Mechanical integrity issues and nacelle sizing are also considered. Finally, estimates are made of the noise generated by the fan and the exhaust configuration and a comparison is made with a traditional high by-pass ratio turbofan. The study concludes that the potential benefits in terms of SFC are somewhat overshadowed by the less favourable outcomes in terms of weight, nacelle size, noise and tip-turbine efficiency.

The objective of the current study was to investigate the effect of casing treatment on a multistage axial flow compressor. The main purpose of the investigation was to extend the range and operability of multistage axial compressors. The study seeks to establish whether a vane-recessed tubular-passage casing-treatment could provide beneficial stall margin improvement, without sacrificing the efficiencies of the compressor with the restricted space available for the treatment. A casing treatment that consisted of three parts: an outer casing ring, with a tubular shaped passage on the inside, a set of 120 evenly spaced curved vanes, and then a shroud or inner ring was developed from two initial designs. The casing treatment, manufactured from high quality acrylic, was positioned upstream and partly covering the tip of the first stage rotor blades. The casing treatment was tested on the first stage of a three-stage low-speed compressor with inlet guide vanes with the rear two stages removed. The rotor blade tip axial chord exposure had a significant impact on the effectiveness of the casing treatment. Seven compressor configuration incorporating casing treatments of 23.2%, 33.3%, 43.4%, 53.5%, 63.6%, 73.7% and 83.8% rotor exposure were tested. The results showed significant improvements in stall margin in all exposures and insignificant efficiency sacrifices in some exposures. Nearly 29% of stall margin improvement in terms of the corrected mass flow rate was achieved with 33.3% rotor blade tip axial chord exposure. The compressor build with 53.5% rotor exposure was the best configuration in terms of maximum efficiency gain. In terms of peak pressure rise coefficients the compressor configuration with a casing treatment of 63.6% exposure was the best design. The results also suggest that the vane-recessed tubular-passage casing treatment designed as part of this research, in most instances enabled the stall conditions in the compressor to become progressive rather than abrupt.

Current fighter engine designs extract power to drive the afterburner fuel pump through the use of a gearbox. The presence of the gearbox only allows the fuel pump to operate at a fixed proportion of engine speed. In addition the fuel pump is continually rotating, although not pumping fuel, even when the afterburner is not engaged. This article investigates the feasibility of using an air turbine to drive the afterburner fuel pump in preparation for supporting an all-electric engine. Utilising performance data for a typical modern military engine, 1-dimensional design techniques were used to design several radial turbines to power the afterburner fuel pump. A choice of an axial or a radial air turbine is possible. Both were reviewed and it was determined that a radial turbine is optimum based on manufacturability and (theoretical) efficiency. Several design iterations were completed to determine the estimated weight and size based on various air off-take locations, mass flows, and rotational speeds. These iterations showed that increasing mass flow allows for lower rotational speeds and/or smaller diameter rotors, but with a corresponding increases in thrust penalties.

This paper presents the design procedure and application of a nested neural network for diagnostics of a small jet engine. Such a diagnostics technique is based on the performance analysis while the performance model was developed with TURBOMATCH, the Cranfield University’s gas turbine simulation code. To validate this model, an outdoor test was conducted to run the small engine. Areas examined in this paper are performance validation of the engine, neural network design, training data generation, and networks training procedures. The assumptions, measured parameters selection and the results obtained are presented and discussed. The results obtained show the good prospects for the use of NNs for detection of existing faults, isolation of faults and quantification of fault levels.