Combustor turbine interface optimisation studies in ECAT (RIDN/RODN/RTDF optimisation) and understanding the impact on vane

Higher turbine inlet temperatures result in improved efficiency and power output of gas turbines. The high-pressure nozzle guide vanes (HP NGVs) are the stators that sit immediately downstream of the combustor in a gas turbine, experiencing high temperatures and a non-uniform inlet total temperature profile. The hot-gas-path temperature in the HP NGV passages is well in excess of the metal melting temperature, as such cooling systems have been developed to maintain an acceptable component lifespan. As gas turbine performance continues to improve, better cooling system designs are required to manage the increasing thermal loads that will be imparted by higher turbine inlet temperatures. Film cooling is a cooling technique widely used on HP NGVs where air is bled from the compressor and a thin film is injected onto the HP NGV surface to directly shield the surfaces from the hot gas path. The main disadvantage of this method of cooling is that bleeding air from the compressor reduces the mass-flow that work can be extracted from in the turbine, thus reducing system efficiency. Therefore, the aim of an optimal film cooling system is to appropriately manage the thermal loads with the minimum amount of coolant.

While existing research has reported on successful numerical optimization of film cooling systems, research has primarily been concerned with the optimization of a single cooling hole in a simplified channel. This was originally due to the large computational cost of simple film cooling optimization routines however, in recent years, new optimization schemes have been proposed that have significantly reduced that expense. Few studies have been published that detail optimization methods for film cooling arrays on turbine vane surfaces and optimization of endwall film cooling designs has received almost no attention.

The performance of endwall cooling systems is affected by many interdependent parameters and as such is difficult to predict precisely. As such, conventional design relies heavily on designers' prior experience and costly experimental fine-tuning. An accurate endwall film cooling optimization methodology has the potential to have a significant impact on system efficiency, minimising the large coolant mass flow, and therefore efficiency penalty associated with bleeding coolant from the compressor, required to cool the large, exposed area. A reliable method could also shorten development cycles and give designers the opportunity to cost-effectively explore a wider design space.

The objective of this project is to apply recently developed film cooling optimization techniques to HP NGV endwall cooling systems. An endwall optimization tool will be developed that can efficiently and cheaply search the design space being considered for the optimal film cooling configuration. The success of any developed tool would be evaluated experimentally with the engine component aerothermal (ECAT) facility, a real-engine-parts rig with a high degree of engine similarity for testing HP NGVs. The developed tool will be used to optimize the endwall cooling system of a currently in-service vane. The aerothermal performance of the baseline and optimized design will then be evaluated in the ECAT rig to validate the optimization process.

1. Impact on the UK Aero-Propulsion and Power Generation Industry
The UK Propulsion and Power sector is undergoing disruptive change. Electrification is allowing a new generation of Urban Air Vehicles to be developed, with over 70 active programmes planning a first flight by 2024. In the middle of the aircraft market, companies like Airbus and Rolls-Royce, are developing boundary layer ingestion propulsion systems. At high speed, Reaction Engines Ltd are developing complex new air breathing engines. In the aero gas turbine sector Rolls-Royce is developing UltraFan, its first new architecture since the 1970s. In the turbocharger markets UK companies such as Cummins and Napier are developing advanced turbochargers for use in compounded engines with electrical drive trains. In the power generation sector, Mitsubishi Heavy Industries and Siemens are developing new gas turbines which have the capability for rapid start up to enable increased supply from renewables. In the domestic turbomachinery market, Dyson are developing a whole new range of miniature high speed compressors. All of these challenges require a new generation of engineers to be trained. These engineers will need a combination of the traditional Aero-thermal skills, and new Data Science and Systems Integration skills. The Centre has been specifically designed to meet this challenge.

Over the next 20 years, Rolls-Royce estimates that the global market opportunities in the gas turbine-related aftercare services will be worth over US$700 billion. Gas turbines will have 'Digital Twins' which are continually updated using engine health data. To ensure that the UK leads this field it is important that a new generation of engineer is trained in both the underpinning Aero-thermal knowledge and in new Data Science techniques. The Centre will provide this training by linking the University and Industry Partners with the Alan Turing Institute, and with industrial data labs such as R2 Data Labs at Rolls-Royce and the 'MindSphere' centres at Siemens.

2. Impact on UK Propulsion and Power Research Landscape
The three partner institutions (Cambridge, Oxford and Loughborough) are closely linked to the broader UK Propulsion and Power community. This is through collaborations with universities such as Imperial, Cranfield, Southampton, Bath, Surrey and Sussex. This will allow the research knowledge developed in the Centre to benefit the whole of the UK Propulsion and Power research community.

The Centre will also have impact on the Data Science research community through links with the CDT in Data Centric Engineering (DCE) at Imperial College and with the Alan Turning Institute. This will allow cross-fertilization of ideas related to data science and the use of advanced data analytics in the Propulsion and Power sectors.

3. Impact of training a new generation of engineering students
The cohort-based training programme of the current CDT in Gas Turbine Aerodynamics has proved highly successful. The Centre's independent Advisory Group has noted that the multi-institution, multi-disciplinary nature of the Centre is unique within the global gas turbine training community, and the feedback from cohorts of current students has been extremely positive (92% satisfaction rating in the 2015 PRES survey). The new CDT in Future Propulsion and Power will combine the core underlying Aero-thermal knowledge of the previous CDT with the Data Science and Systems Integration skills required to meet the challenges of the next generation. This will provide the UK with a unique cohort of at least 90 students trained both to understand the real aero-thermal problems and to have the Data Science and Systems Integration skills necessary to solve the challenges of the future.