Paul C. Ivey

An R&D options selection model for investment decisions

Technology centered organisations must be able to identify promising new products or process improvements at an early stage so that the necessary resources can be allocated to those activities. It is essential to invest in targeted RD the selection of the most appropriate projects is the aim of R&D selection models. Although capital budgeting and financial portfolio management offer a similar style approach, the techniques used for the solution of those is different to that used for R&D project selection. The reasons for this are that project selection is complicated by many factors, such as uncertainty, interrelationships between projects, changes over time and success factors that are difficult to measure. Thus, a mathematical optimisation approach in isolation is not practical. Project selection models not only have to consider these problems but also that there are different types of R&D. The spectrum of R&D ranges from low budget exploratory research to large budget product development. This paper reviews the development of a project selection and evaluation tool that can be applied to a wide range of research, technology and investment decisions. Firstly, the background on project selection models is given. This is followed by the introduction of the model and its application to a sample group of projects. Finally, some conclusions are discussed as to the applicability of such models.

An overview of the measurement errors associated with gas turbine aeroengine pyrometer systems

It is advantageous to operate the thermodynamic cycle of an aeroengine at as high a turbine entry temperature as practical for the current metallurgical limits of the turbine blades, in order to achieve peak cycle efficiency and thus lower specific fuel consumption. However, achieving the highest possible turbine entry temperature requires accurate knowledge of the turbine blade temperatures for control purposes to prolong component life, as frequent excursions beyond the design limits of the blades can severely reduce their service life. The optical pyrometry technique represents the best method for providing these crucial temperature data needed for blade condition based monitoring. However, this method of non-contact temperature measurement is subject to a number of errors inherent to the gas turbine operating environment. In this paper we present the general operating principles and an overview of the measurement errors associated with optical pyrometry, together with a discussion of the techniques to prevent, limit and compensate for such errors resulting from the turbine environment.

Parametric Study of Tip Clearance – Casing Treatment on Performance and Stability of a Transonic Axial Compressor

The control of tip leakage flow (TLF) through the clearance gap between the moving and stationary components of rotating machines is still a high-leverage area for improvement of stability and performance of aircraft engines. Losses in the form of flow separation, stall, and reduced rotor work efficiency are results of the tip leakage vortex (TLV) generated by interaction of the main flow and the tip leakage jet induced by the blade pressure difference. The effects are more detrimental in transonic compressors due to the interaction of shock-TLV. It has been previously shown that the use of slots and grooves in the casing over tip of the compressor blades, known as casing treatment, can substantially increase the stable flow range and therefore the safety of the system but generally with some efficiency penalties. This paper presents a numerical parametric study of tip clearance coupled with casing treatment for a transonic axial-flow compressor NASA Rotor 37. Compressor characteristics have been compared to the experimental results for smooth casing with a 0.356 mm tip clearance and show fairly good agreement. Casing treatments were found to be an effective means of reducing the negative effects of tip gap flow and vortex, resulting in improved performance and stability. The present work provides guidelines for improvement of steady-state performance of the transonic axial-flow compressors and improvement of the stable operating range of the system.Copyright

Parametric study of tip clearance: Casing treatment on performance and stability of a transonic axial compressor

The control of tip leakage flow through the clearance gap between the moving and stationary components of rotating machines is still a high-leverage area for improvement of stability and performance of aircraft engines. Losses in the form of flow separation, stall, and reduced rotor work efficiency are results of the tip leakage vortex (TLV) generated by interaction of the main flow and the tip leakage jet induced by the blade pressure difference. The effects are more detrimental in transonic compressors due to the interaction of shock TLV. It has been previously shown that the use of slots and grooves in the casing over tip of the compressor blades, known as casing treatment, can substantially increase the stable flow range and therefore the safety of the system but generally with some efficiency penalties. This paper presents a numerical parametric study of tip clearance coupled with casing treatment for a transonic axial-flow compressor NASA Rotor 37. Compressor characteristics have been compared to the experimental results for smooth casing with a 0.356 mm tip clearance and show fairly good agreement. Casing treatments were found to be an effective means of reducing the negative effects of tip gap flow and vortex, resulting in improved performance and stability. The present work provides guidelines for improvement of steady-state performance of the transonic axial-flow compressors and improvement of the stable operating range of the system.

Measurement of tip-clearance flow in a multistage, axial flow compressor

Detailed measurements using pneumatic probe traverses, blade static pressure tappings, and laser anemometry are made in the third stage ofa large-scale, low-speed, four-stage, axial flow, research compressor. Inlet conditions show well-ordered two-dimensional flow from approximately 40 to 85 percent annulus span. Outside of this region, reduced total pressure due to upstream leakage losses and endwall effects results in high incidence to the following blade row. As a result, peak suction surface static pressure moves forward along the blade chord for both the hub and tip of stators and rotors. At the blade tip, however, the peak suction pressure is maintained with chord due to radial flow on the suction surface being entrained into the tip leakage jet. The extent of rotor chord for which this entrainment occurs increases with increasing rotor tip clearance gap. The leakage jet from both stators and rotors is seen to roll up into a vortex downstream of their respective blade rows.

Performance enhancement in transonic axial compressors using blade tip injection coupled with casing treatment

Abstract The casing treatment and flow injection upstream of the rotor tip are two effective approaches in suppressing instabilities or recovering from a fully developed stall. This paper presents numerical simulations for a high-speed transonic compressor rotor, NASA Rotor 37, applying a state-of-the-art design for the blade tip injection. This is characterized by introducing a jet flow directly into the casing treatment machined into the shroud. The casing treatment is positioned over the blade tip region and exceeds the impeller axially by ∼30 per cent of the tip chord both in the upstream and in the downstream directions. To numerically solve the governing equations, the three-dimensional finite element based finite volume method CFD solver CFX-TASCflow (version 2.12.1) is employed. For a compressible flow with varying density, Reynolds-averaging leads to appearance of complicated correlations. To avoid this, the mass-weighted or Favre-averaging is applied. Using an injected mass flow of 2.4 per cent of the annulus flow, the present design can improve stall margin by up to 7 per cent when compared with a smooth casing compressor without tip injection. This research can lead to an optimum design of recirculating casing treatments or other mechanisms for performance enhancement applying tip flow injection.

Optical pyrometry for gas turbine aeroengines

Fundamentally, it is advantageous to operate an aeroengines thermodynamic cycle at as high a turbine entry temperature as practical for the current metallurgical limits of the turbine blades in order to achieve peak cycle efficiency and thus lower specific fuel consumption. However, achieving the highest possible turbine entry temperature requires accurate knowledge of the turbine blade temperatures for control purposes to prolong component life as frequent excursions beyond the design limits of the blades can severely reduce their service life. The optical pyrometry technique represents the best method for providing this crucial temperature data needed for blade condition‐based monitoring. This paper presents the general operating principles, system aspects and design considerations for the application of the optical pyrometer instrument for inflight service use on gas turbine aeroengines.

A New Design for Tip Injection in Transonic Axial Compressors

This paper presents a state of the art design for the blade tip injection. The design includes the means to inject high-pressure gas jet directly into a circumferential casing groove formed in the shroud adjacent to the blade tip. The casing groove is positioned over the blade tip and exceeds 30% of the blade axial chord beyond the impeller to both upstream and downstream directions. In order to validate the multi block model used in the tip gap region, main flow characteristics are verified with the experimental data for smooth casing with a design clearance of 0.5% span. Three arbitrary mass flow rates (1.75%, 2.45%, and 4.35% of choked mass flow) have been studied. The results indicate remarkable advantageous effects on the compressor stability margin. Further, compared to classical design for tip injection, the current design can significantly improve the compressor stall margin due to direct injection of flow. An increase of the injected air may enhance the stall margin improvement. Furthermore, results for injection at different angles, shows that the compressor stability margin reaches a maximum when the bleed air in the relative coordinates is aligned with the mean camber line of the blade leading edge. The main objective of this research is to present an improved design for tip injection as well as to determine its effect on the stability enhancement of the compressor. The current research also provides guidelines to an optimum design of tip injection.Copyright

The Engineering Doctorate model of consultant/researcher/innovator/entrepreneur for new product development—a gas turbine instrumentation case study

Abstract This paper presents the utilisation of the British Engineering Doctorate programme for new product development through an Industry–University partnership between a sponsoring company and an academic establishment, the aim being to stimulate greater levels of technological innovation and equip research engineers with the necessary design tools and business skills for entrepreneurial ventures. Described within the paper is the consultant/researcher/innovator/entrepreneur (CRIE) model, developed by the Gas Turbine Instrumentation Group at Cranfield University, that the research engineer undertakes in order to not only satisfy the requirements of the doctoral study but to exploit their research output in terms of a new product and fully appreciate the market implications of their designs. This CRIE model is illustrated through the use of a case study based on the work between Cranfield and Rolls-Royce plc within the research field of optical pyrometry for in-flight service use on a gas turbine aeroengine.

A Review of Purge Air Designs for Aeroengine-Based Optical Pyrometers

With the advent of power by the hour type agreements within the civil aeroengine market, the application of engine monitoring system data has reached the level of strategic use for informed decision making in not only the aftermarket but increasingly in the contract negotiation stage. One of the key cost drivers in these dollar-per-hour contracts for the OEMs to analyze is the life and maintenance requirements of the turbine blades leading ultimately to blade life management. Such life management of key components is of critical importance to ensure that the economic and technical risks to both service provider and customer are minimized. The optical pyrometer, through providing a direct temperature measurement of the turbine blades, is a primary input for providing a more realistic assessment of the components operating history associated with the use of life usage/remaining algorithms. However, the greatest concern with the in-service use of pyrometry is the issue of fouling since the pyrometers lens is exposed to the turbine environment. The level of optical contamination is usually minimized by introducing purge air, bled from the compressor, down the sight tube to prevent both the build-up of contaminants on the exposed system optics and particles in the gas stream from coming in contact with the lens. This paper provides a review of purge air designs and the key methodologies for engine designers to be acquainted with when seeking to integrate the use of optical pyrometry systems in new engine concepts.