Experimental and Theoretical Modelling of Heat Transfer in Aero-engine Compressors.

Due to increasing compression ratio in aero-jet engines, that will enable use of SAF or Hydrogen fuel, tighter blades' tip clearance in the compressor stage are introduced to ensure required efficiency. This clearance can be affected by the blade expansion towards the casing's wall due to centrifugal force, and thermal expansion. The latter phenomenon is the main drive for this research, since the prerequisite to understand how thermal expansion affects the blades' size, is to understand heat transfer beneath the blades floor (shroud), where secondary flow is located. This flow divagates from the main flow path and enters space inside the compressor, between the shaft and the shroud, and usually is cooler than the main flow going above it through the compressor. The secondary flow is used to cool down the shroud, and effectively the blades, decreasing their thermal expansion. How effective this cooling is depends on the resulting flow structures inside the cavities, which in turn dependent on temperatures around these structures and of the secondary flow. This, with added complexity of cavities' rotation, creates a conjugate problem that is impossible to solve purely analytically.
The aim of the project is to aid existing mathematical models of compressor cavity heat transfer with empirical data, that have not yet been implemented or provided. This includes modifying existing experimental rig to facilitate new inlet conditions, operational parameters, and data collection points, making up for the objectives of the project. The first objective from the list includes installing already designed "pre-swirler" component that will swirl the incoming flow, and an "Aero-strut" that will house three thermocouple sensors to obtain temperature measurements inside the core of the rotating mass of air in the cavity.

Upon completion the project should deep understanding of the heat transfer inside compressor cavity throughout the various operational modes of an aircraft. This will aid designers of jet engines to better understand design options influencing tip clearance. It is also falling within the scope of EPSRC funding as the project supports leading jet engine technology research in the UK, and is working towards sustainability in the sector of aviation and energy production.
Methods used will include running experiments to collect data from the modified rig (like temperature measurements of the air flow, velocity measurements of the upstream air entering cavity, or pressure readings inside the cavity and annular flow), computer-aided design of the new components along with finite element analysis if they are subject to investigated flow, and possible computational fluid dynamics simulation of the parts interacting with the flow.

Impact Summary

This proposal has been developed from the ground up to guarantee the highest level of impact. The two principal routes towards impact are via the graduates that we train and by the embedding of the research that is undertaken into commercial activity. The impact will have a significant commercial value through addressing skills requirements and providing technical solutions for the automotive industry - a key sector for the UK economy.

The graduates that emerge from our CDT (at least 84 people) will be transformative in two distinct ways. The first is a technical route and the second is cultural.

In a technical role, their deep subject matter expertise across all of the key topics needed as the industry transitions to a more sustainable future. This expertise is made much more accessible and applicable by their broad understanding of the engineering and commercial context in which they work. They will have all of the right competencies to ensure that they can achieve a very significant contribution to technologies and processes within the sector from the start of their careers, an impact that will grow over time. Importantly, this CDT is producing graduates in a highly skilled sector of the economy, leading to jobs that are £50,000 more productive per employee than average (i.e. more GVA). These graduates are in demand, as there are a lack of highly skilled engineers to undertake specialist automotive propulsion research and fill the estimated 5,000 job vacancies in the UK due to these skills shortages. Ultimately, the CDT will create a highly specialised and productive talent pipeline for the UK economy.

The route to impact through cultural change is perhaps of even more significance in the long term. Our cohort will be highly diverse, an outcome driven by our wide catchment in terms of academic background, giving them a 'diversity edge'. The cultural change that is enabled by this powerful cohort will have a profound impact, facilitating a move away from 'business as usual'.

The research outputs of the CDT will have impact in two important fields - the products produced and processes used within the indsutry. The academic team leading and operating this CDT have a long track record of generating impact through the application of their research outputs to industrially relevant problems. This understanding is embodied in the design of our CDT and has already begun in the definition of the training programmes and research themes that will meet the future needs of our industry and international partners. Exchange of people is the surest way to achieve lasting and deep exchange of expertise and ideas. The students will undertake placements at the collaborating companies and will lead to employment of the graduates in partner companies.

The CDT is an integral part of the IAAPS initiative. The IAAPS Business Case highlights the need to develop and train suitably skilled and qualified engineers in order to achieve, over the first five years of IAAPS' operations, an additional £70 million research and innovation expenditure, creating an additional turnover of £800 million for the automotive sector, £221 million in GVA and 1,900 new highly productive jobs.

The CDT is designed to deliver transformational impact for our industrial partners and the automotive sector in general. The impact is wider than this, since the products and services that our partners produce have a fundamental part to play in the way we organise our lives in a modern society. The impact on the developing world is even more profound. The rush to mobility across the developing world, the increasing spending power of a growing global middle class, the move to more urban living and the increasingly urgent threat of climate change combine to make the impact of the work we do directly relevant to more people than ever before. This CDT can help change the world by effecting the change that needs to happen in our industry.