Colin Rodgers

Recuperated gas turbine aeroengines, part II: engine design studies following early development testing

Purpose – To advance the design of heat exchanged gas turbine propulsion aeroengines utilising experience gained from early development testing, and based on technologies prevailing in the 1970‐2000 time frame.Design/methodology/approach – With emphasis on recuperated helicopter turboshaft engines, particularly in the 1,000 hp (746 kW) class, detailed performance analyses, parametric trade‐off studies, and overall power plant layouts, based on state‐of‐the‐art turbomachinery component efficiencies and high‐temperature heat exchanger technologies, were undertaken for several engine configuration concepts.Findings – Using optimised cycle parameters, and the selection of a light weight tubular heat exchanger concept, an attractive engine architecture was established in which the recuperator was fully integrated with the engine structure. This resulted in a reduced overall engine weight and lower specific fuel consumption, and represented a significant advancement in technology from the modified simple‐cycle ...

A Hybrid System Based on a Personal Turbine (5 kW) and a Solid Oxide Fuel Cell Stack: A Flexible and High Efficiency Energy Concept for the Distributed Power Market

In this paper a high efficiency and flexible hybrid system representing a new total energy concept for the distributed power market is presented. The hybrid system is composed of a very small size (5 kW) micro gas turbine (named personal turbine-PT) presented in a companion paper by the authors coupled to a small size solid oxide fuel cell (SOFC) stack. The power of the whole system is 36 kW depending on the design parameters assumed for the stack. The design and off-design performance of the hybrid system have been obtained through the use of an appropriate modular code named HS-SOFC developed at the University of Genoa and described in detail in this paper. The results of the simulation are presented and discussed with particular regards to: choice of the hybrid system (HS) design point data, HS design point performance, off-design performance of PT and SOFC stack, and off-design performance of the whole HS. Some preliminary economic results are also included based on different fuel and capital cost scenarios and using the cost of electricity as the parameter for comparison between PT and HS.

Recuperated gas turbine aeroengines. Part III: engine concepts for reduced emissions, lower fuel consumption, and noise abatement

Purpose – This paper seeks to evaluate the potential of heat exchanged aeroengines for future Unmanned Aerial Vehicle (UAV), helicopter, and aircraft propulsion, with emphasis placed on reduced emissions, lower fuel burn, and less noise.Design/methodology/approach – Aeroengine performance analyses were carried out covering a wide range of parameters for more complex thermodynamic cycles. This led to the identification of major component features and the establishing of preconceptual aeroengine layout concepts for various types of recuperated and ICR variants.Findings – Novel aeroengine architectures were identified for heat exchanged turboshaft, turboprop, and turbofan variants covering a wide range of applications. While conceptual in nature, the results of the analyses and design studies generally concluded that heat exchanged engines represent a viable solution to meet demanding defence and commercial aeropropulsion needs in the 2015‐2020 timeframe, but they would require extensive development.Research...

The Ubiquitous Personal Turbine—A Power Vision for the 21st Century

Having a personal computer (PC) and related electronic equipment in the majority of U.S. homes today is accepted without question. In the same vein, having a personal turbine (PT) in the home could also be taken for granted in coming decades to assure a constant and reliable source of electrical power, which is paramount in the e-business era. As addressed in this paper, gas turbine technology has advanced to the point where a natural gas-fired PT, rated at about 5 kW could reliably provide the total energy needs of an average home. The Industrial Revolution of the 18th century, in which a centralized factory replaced cottage industries, was made possible by introduction of the steam engine. In the 21st century IT Revolution, the situation will have essentially gone the full circle, with a high percentage of service industry work being done in the home. For individuals using the internet for conducting business a reliable source of electrical power is mandatory. Alas, this can no longer be assured by the U.S. power grid which is quickly reaching its capacity, and increasing outages will become more commonplace. One solution to this could be the use of PTs in homes in both cities and remote areas. Also it would be ideally suited to applications in the developing countries, where it could provide the total energy needs of villages and small communities. In this introductory paper it is projected that when mass produced in very large quantities like automobile turbochargers, the PT unit cost would be competitive.

Recuperated gas turbine aeroengines, part I: early development activities

Purpose – Interest is currently being expressed in heat exchanged propulsion gas turbines for a variety of aeroengine applications, and in support of this, the aim of this paper is to evaluate the relevance of experience gained from development testing of several recuperated aeroengines in the USA in the late 1960s.Design/methodology/approach – Technology status, including engine design features, performance, and specific weight of recuperated propulsion gas turbines based on radial and axial turbomachinery, that were development tested in the power range of about 300 to 4,000 hp (224 to 2,984 kW) is discussed in Part I.Findings – A successful flight worthiness test was undertaken in the USA of a helicopter powered solely by a recuperated turboshaft engine and this demonstrated a specific fuel consumption reduction of over 25 percent compared with the simple‐cycle engine. However; in an era of low‐fuel cost, and uncertainty about the long‐term structural integrity of the high‐temperature heat exchanger, f...

Ceramic Recuperator and Turbine — The Key to Achieving a 40 Percent Efficient Microturbine

Based on the use of state-of-the-art component technologies and the use of existing metallic materials, achieving an electrical efficiency anywhere near 40 percent in low pressure ratio recuperated microturbines is proving elusive. Current microturbines, rated at say 100 kW, operate with efficiencies approaching 30 percent. Advancing this to an upper level of about 35 percent is projected based on the ability to operate at turbine inlet temperatures greater than 1100C, and the utilization of a higher cost superalloy recuperator. This paper puts into perspective the challenge of trying to achieve 40 percent efficiency for small recuperated turbogenerator designs with radial flow components; the major constraints being associated with stress limitations in both the turbine and recuperator. Various publications (issued by both industry and the Government) often mention an efficiency goal of 40 percent for small gas turbines of this configuration, however, it needs to be recognized that the means to achieve this are beyond current high temperature metallic component capabilities. To achieve this “goal” necessitates increasing the operating temperature of the turbine and recuperator above 1100C and 800C respectively. Such advancements are projected to be technically and cost-effectively achievable by utilizing ceramic components, which with a dedicated development program, could perhaps become a reality in less than a decade to meet both future distributed power generation needs and defense applications, and be in concert with ever-demanding conservation goals and reduced emissions.Copyright

A Hybrid System Based on a Personal Turbine (5 kW) and a SOFC Stack: A Flexible and High Efficiency Energy Concept for the Distributed Power Market

In this paper a high efficiency and flexible hybrid system representing a new total energy concept for the distributed power market is presented.The hybrid system is composed of a very small size (5 kW) micro gas turbine (named personal turbine – PT) presented in a companion paper by the authors (McDonald and Rodgers, 2001) coupled to a small size Solid Oxide Fuel Cell (SOFC) stack. The power of the whole system is 36 kW depending on the design parameters assumed for the stack.The design and off design performance of the hybrid system have been obtained through the use of an appropriate modular code named “HS-SOFC” developed at the University of Genoa (Magistri, 1999) and described in detail in this paper.The results of the simulation are presented and discussed with particular regards to: choice of the Hybrid System (HS) design point data, HS design point performance, off design performance of PT and SOFC stack, off design performance of the whole HS.Some preliminary economic results are also included based on different fuel and capital cost scenarios and using the cost of electricity as the parameter for comparison between PT and HS.Copyright

Heat Exchanged Propulsion Gas Turbines: A Candidate for Future Lower SFC and Reduced Emission Military and Civil Aeroengines

After seven decades of service the evolution of simple cycle propulsion gas turbines continues with emphasis now being placed on reduced fuel burn, lower emissions, and less noise. With compressor and turbine efficiencies near plateauing, and turbine inlet temperatures paced by materials and blade cooling technologies, improvements in SFC, specific power and weight for conventional engines (including small turboprop, and turboshaft engines and larger turbofans) will likely be incremental compared with the past. With retention of the simple cycle both evolutionary and revolutionary approaches are being taken by the aeroengine industry to improve performance, particularly reduced fuel burn in an era of high fuel cost. In this paper a further step is suggested, that is in concert with meeting performance, economic, and environmental goals of future aeroengines, namely the use of a more complex thermodynamic cycle involving recuperation for turboprop and turboshaft engines, and intercooling together with recuperation for higher pressure ratio turbofan engines. The idea of heat exchanged propulsion gas turbines is not new, but the many concepts identified from studies done periodically over the last 65 years, including the few engines that were static tested and one test flown, didn’t find acceptance in an era of low fuel cost and concerns about recuperator integrity and reliability. With today’s very high fuel cost there is current interest in this type of engine because of its potential for low SFC and reduced emissions. In this paper potential applications are summarized and the features of various heat exchanged aeroengine design concepts together with projected performance are presented. Included is a discussion on the various issues that must be resolved before they enter service. A postulated deployment scenario is suggested with engines initially developed to meet military aviation needs, such as recuperated turboprop and turbofan engines for extended range UAV’s, followed by a recuperated turboshaft engine for a helicopter. Operational experience and demonstrated reliability from these would pave the way for high efficiency ICR turbofan engines for military and civil aircraft service sometime after the year 2020.Copyright

Small Recuperated Gas Turbine APU Concept to Abate Concern About Emissions, High Fuel Cost, and Noise

During the last decade microturbines in the 30 to 250 kW power range have been in service, but they have not been produced in significant enough quantities to impact the DG market due to a combination of factors including their high cost, modest efficiency, utility institutional concerns, and low interest in CHP use in the USA, although the latter could change as a result of fuel cost escalation. Very small gas turbines (ie. less than 10 kW) have been investigated periodically over the years, mainly for potential military use, but to date have not found a niche. This could well change with over 20 states now having instigated idling regulations that limit or prohibit heavy duty truck diesel engine idling. With emphasis on reducing emissions and noise levels this essentially implies that in the future a small APU will be required to provide the truck’s stationary electrical needs and cabin climate control. While there will be several power source types vying for this potentially large market, a small gas turbine APU is viewed as having attractive features which include low emissions, low acoustic signature, vibration-free operation, compact and light weight package, obviates the need for oil lubrication and liquid coolant systems, ease of cold weather starting, immediate response, and the use of fuel from the truck tank. In this paper a small recuperated gas turbine APU concept rated at 5kW is discussed including component design considerations, layout features, engine performance, and target cost. The conservative design of the APU is based on the use of existing materials and state-of-the-art gas turbine technology, and is amenable to high volume automated manufacturing processes. A competitive cost is projected if the proposed APU of modular construction was fabricated in large quantities like the production of vehicular turbochargers in Europe.Copyright

The Ubiquitous Personal Turbine (PT)…A Power Vision for the 21st Century

Having a personal computer (PC) and related electronic equipment in the majority of US homes today is accepted without question. In the same vein, having a personal turbine (PT) in the home could also be taken for granted in coming decades to assure a constant and reliable source of electrical power, which is paramount in the e-business era. As addressed in this paper, gas turbine technology has advanced to the point where a natural gas-fired PT, rated at about 5 kW could reliably provide the total energy needs of an average home. The Industrial Revolution of the 18th Century, in which a centralized factory replaced cottage industries, was made possible by introduction of the steam engine. In the 21st Century IT Revolution, the situation will have essentially gone the full circle, with a high percentage of service industry work being done in the home. For individuals using the Internet for conducting business a reliable source of electrical power is mandatory. Alas, this can no longer be assured by the US power grid which is quickly reaching its capacity, and increasing outages will become more commonplace. One solution to this could be the use of PT’s in homes in both cities and remote areas. Also it would be ideally suited to applications in the developing countries, where it could provide the total energy needs of villages and small communities. In this introductory paper it is projected that when mass produced in very large quantities like automobile turbochargers, the PT unit cost would be competitive.Copyright