Gas turbine research at Whittle's test site21 May 1998
GEC Alsthom's Power Generation Division, makers of the world's widest range of gas turbines, have now opened a major new gas turbine research centre for both industrial and aircraft propulsion gas turbines, on the site where gas turbine development was first started by the late Sir Frank Whittle at Whetstone in Leicester in the UK.
The grand opening of GEC Alsthom's Whittle Test Centre by UK Energy Minister John Battle took place on 28 January 1998, but it had already been working intensively for some years making major contributions to the gas turbine market's ever increasing demands on new, application specific, advanced gas turbine development testing and research. The first of the main rigs commenced operation in November 1995, while the buildings were still under construction, after a project starting date in November 1994.
There was nothing sentimental about the decision to site the gas turbine test centre on the original location where Sir John Whittle developed the first gas turbine aircraft engines during the late 1930s, it was a natural development of GEC Alsthom's existing mechanical engineering research work on this site at Whetstone in Leicestershire. The $30 million project, designed and built by the Mechanical Engineering Centre of GEC Alsthom's Power Generation Division under the leadership of Managing Director Peter Robinson, aims to help meet the power generation needs of the 21st century.
Whittle's original Power Jets Factory on the site, which was eventually sanctioned by the UK government in 1940, is reckoned to have been the first factory in the world built specifically for jet engine development and initial production. Most of the original buildings are still standing, now surrounded by much of the most modern turbine development technology currently available.
The centre is based around a 40 by 20 m extendible open plan building which accommodates most of the large and small test rigs which have been installed to date. The facilities, which are supported by the most advanced and flexible SCADA and analysis systems, are also being applied to non-power generation work.
Some 30 per cent of the work undertaken at Whetstone involves engineering problems associated with military and civil aircraft engines, but the main aim is to further enhance the European Gas Turbine's own range of industrial gas turbines which extends from the smallest Ruston machines to the largest GE turbines covering an output range from under 10 MW to over 230 MW.
Clearly the centre is well set up to handle IGCC and PFBC development. As well as having acquired and refurbished the key kit from the former Grimethorpe test rigs at incredibly low cost, they have put together a syngas synthesis facility which is capable of mixing virtually any cocktail of constituents required in sufficient quantities to drive large combustion rigs at full engine operating conditions.
With these provisions they are well able to execute the same kind of demonstration projects as Sydkraft's biomass gasification project in Sweden and the Varnamo Bioflow gasifier in Finland. These are not the main work horses, but a key feature of the Whetstone test centre is the wide range of fuels that can used in the rigs. High temperature demonstrator unit: Currently undergoing testing, using a modified Ruston 4.5 MW gas turbine, new components can be tested in this facility at greatly increased firing temperatures at full scale. At present the existing compressor is being utilised with a new combustion system and a new high pressure turbine with instrumentation installed to acquire data from both static and rotating components.
Systems can be tested at "rotor inlet temperatures" of up to 1425°C, even after mixing in all of the stator cooling air.
Water analogy combustion rig: With a working section of up to 1 m3, this rig is used for calibration of computational fluid dynamics tools, and for refining combustor concepts, particularly with respect to mixing properties.
It has mainly been used for development of dry low NOx combustors. Using water analogy equipment is much cheaper than using a gas flow rig and generates more useful results in some respects. Fuel flow can be simulated and traced by the use of laser induced fluorescence, and laser systems are also used for digital quantitization of the flow measurement systems.
Atmospheric combustion rig: Used to verify the behaviour of prototype combustors at low pressure before proceeding to more costly high pressure tests. Ignition characteristics are best tested at atmospheric pressure. Small programmes on catalytic combustion have been carried out here as well as advanced combustion control systems making use acoustic dynamics phenomena.
High pressure combustion rig: Invest-
igation of large combustion systems at full scale at high pressures and temperatures burning a variety of fuels can be carried out on this high flow combustion rig. It is large enough to accommodate a range of systems and to enable air inlet flow patterns that are representative of the actual engines. It has a back pressurising valve, traversing equipment and emissions measurement facilities.
Medium flow combustion rig: This is a smaller version of the high pressure combustion rig equipped to carry out tests on synthesised gases with application specific instrumentation.
Warm air turbine rig: Still undergoing construction at the time of our last visit, the main purpose of the warm air turbine rig is to improve the understanding of detail flows involved in advanced turbines with high temperature blade cooling with a view to gaining further efficiency improvements. The rig is also used for calibrating computational fluid dynamics tools for specific applications such as unsteady flows and coolant mixing.
For the latter function, the density ratio of coolant flow to main stream combustion products is established to support accurate modelling of coolant mixing. The rig is rated for up to 7500 kW and 18 000 r/min load absorption. It has a secondary cooled air supply of 5 kg/s, 30°C.
Syngas compound: The syngas compound is uniquely equipped to generate low and medium calorific value fuel mixtures of CH4, CO, H2O, H2, N2, NH3, etc. for a variety of programmes supported by EU Thermie and British DTI funding. Syntheses applied so far include biomass, waste gases, mine gas, landfill gas, process gases such as blast furnace gas, and testing is under way on gasified visbreaker residue fuel gas.
Data acquisition: A wide range of gas analysis, mechanical and aerodynamic instrumentation and customisable SCADA equipment is available, all feeding a single high speed single wire LAN covering the entire complex. Digital analysis of dynamic measurements supports FFTs in real time and on line calibration is also accommodated.
Dedicated power supply: Electricity supply capacity of 25 MVA is available and provisions are made for exporting up to 12 MVA to the grid.
Air flow: Air supply of up to 31 kg/s at 16 barg and 350 to 525°C generally. Engine test bed air flow of 25 kg/s can be supplied with variable exhaust nozzle control, with the capability to operate at up to 1100°C.
Fuel supply: Natural gas supply for up to 175 MW at 22 barg is available, as well as synthesised gases up to 3 kg/s mass flow at 15 barg and temperature up to 600°C as well as distillate oil supply.
Cooling systems: Of the three available cooling systems, the largest can absorb 10 MW. Total capacity is 16 MW. A reservoir of 1 million litres of cooling water for hot gas quenching is available from Whittle's original brick built cooling pond which is still in good order
GEC Alsthom's Mechanical Engineering Centre (MEC) has established a widely recognised expertise in modelling flow patterns using advanced CFD (computational fluid dynamics) techniques.
These are applied in earnest at Whetstone in combustor development and also in emissions reduction.
Reducing emissions in gas turbine combustion depends on close control of the complex chemistry of the flame by optimising stoichiometry and flow patterns of fuel and combustion air.
MEC has developed unique methods of combining fluid dynamics and reaction kinetics codes in complex geometries to predict dynamic response and generation of undesirable emissions.
Equally essential, ensuring the robustness of the combustor requires exhaustive stress and service life predictions including detailed heat transfer analysis. Recent combustion system failures in field test versions of the latest advanced power generation turbines stress the need for continuing research on this front. At Whetstone, separate hot side and cooling heat transfer analyses are integrated using the ESATAN thermal analysis software originally written by MEC for the European Space Agency. Materials are also assessed for the required duty and the results integrated into in-house materials behaviour models.
Test programmes at Whetstone contribute to and benefit greatly from EGT's materials design databases, which are now being developed as specialised expert systems, although because of the extremely large knowledge base involved in advanced gas turbine materials this is proving difficult.
Materials for land based industrial turbines face a more hostile environment than the once more highly rated aircraft engine turbines. Creep lives of more than 40 000 hours are needed for materials which must perform in ever increasing stress, temperatures, thermal shock, corrosion and thermal transfer conditions.
While conventional low alloy steels are still being used effectively in high pressure ratio compressor designs, single crystal and directionally solidified alloys now in regular use for turbine blades and new alloys to follow CMSX-4 and CM186 LC are being investigated.
Titanium based alloys are being considered for advanced compressors for the new marques of gas turbine and nickel based alloys are anticipated for highly supercritical steam turbine applications.
Design solutions which use this wide range of materials, many of which are anisoptropic, call for a comprehensive and validated materials database in which test results, methods of analysis, design data and archived records may be stored. Physical and mechanical properties of structural materials, fracture mechanics data, and properties related to surface engineering all need to be made available in this context.
EGT has built up a materials database of extraordinary value using the commercial package MSC/Mvision from the MacNeal-Schwendler Corporation as the software platform. This system broadly adheres to the internationally standardised generic model for data exchange under Part 45 of the ISO Standard for exchange of product data and also ASTM E49 (8).
The MSC/Mvision software provides the means to record pre-defined metadata in spreadsheets which are also used to store tools for the data processing and analysis of test data.
Since Microsoft Office has been adopted across the company, and is used for the majority of reports, data analyses and calculations in general, the output from the Mvision software is also available as Excel datasheets formatted to provide tabular and graphical data.
The EGT database is distributed via servers on all EGT sites, and it is generally considered that browsing the database and making material comparisons is still best carried out using the Mvision software on workstations, but the Excel data can be more readily embedded into other programmes which make use of application specific data such as component analysis.
The test centre is run as a commercial profit centre, gaining its return on investment from both internal GEC Alsthom and external customer contract business. It works in close liaison with existing facilities at EGT's Lincoln (UK) and Belfort (France) works as well as with GE of the USA's industrial and aircraft engine operations.
In addition, the group has worked with Mitsui Babcock in Renfrew, Scotland with a compressor plus combustor rig on the dynamic control of surge conditions taking compressor bleed into account.
Control and monitoring of all the test rigs, plant and ancillary devices is carried out via a single wire LAN connection to a separate Operations Centre.
It uses a 32 channel switched 100Base-T Ethernet network running ten times faster than the conventional Ethernet. This allows data to be monitored and analysed on Pentium based PC workstations running Windows NT. The high and low speed data acquisition sub-systems are capable of handling up to 64 channels at rates of 500 kHz, or 1024 channels at sample rates to 200 Hz.
Full multi-media facilities are also incorporated for storing, analysing, and outputting results, with DDE links for transferring information between programmes.
A high speed SCADA system stores dynamic data over a broad frequency spectrum, and voice communications as well as video channels are included that can bring detailled test results to the designers desk within minutes of test completion.