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Hazby H.R.,PCA Engineers Ltd | Xu L.,University of Cambridge | Casey M.V.,PCA Engineers Ltd
Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy | Year: 2017

This paper presents an experimental and numerical study of the flow in a 1:1 scale, automotive turbocharger centrifugal compressor. Particle image velocimetry measurements have been carried out in the vaneless diffuser at 50% of the design speed. The challenges involved in taking optical measurements in the current small-scale compressor rig are discussed. The overall stage performance and the measured diffuser flow are compared with the results of steady-state computational fluid dynamics calculations. A good agreement between the computational fluid dynamics and the experimental results demonstrates that the numerical methods are capable of predicting the main flow features within the compressor. The synthesis of measured and predicted data is used to explain the sources of the flow and performance variations across the compressor map, and the differences in loss production between small and large compressors are highlighted. © IMechE 2016.

Hazby H.R.,PCA Engineers Ltd. | Casey M.V.,PCA Engineers Ltd. | Casey M.V.,University of Stuttgart | Numakura R.,IHI Corporation | Tamaki H.,IHI Corporation
Institution of Mechanical Engineers - 11th International Conference on Turbochargers and Turbocharging | Year: 2014

The design of a mixed flow compressor stage with an extremely high flow coefficient (φ) of 0.25 and a high pressure rise coefficient (φ) of 0.56 is described. The objective of the work was to explore the performance potential in this highly unconventional area of the design space and to assess the capability of design methods. The paper describes the aero-mechanical design approach for the preliminary design and discusses the challenges involved in developing such highly loaded compact stages. The test data obtained on a prototype stage is also presented. The results show that acceptable performance levels can be achieved at these extreme design conditions and further exploration of the design space is worthwhile. © The author(s) and/or their employer(s), 2014.

Agency: European Commission | Branch: FP7 | Program: CP-FP | Phase: AAT-2007-1.1-03;AAT-2007-4.2-03 | Award Amount: 10.79M | Year: 2008

FUTURE brings together European and international well reputed centres-of-excellence in order to reach major scientific & technical objectives in striving towards flutter-free turbomachine blades. By advancing the state-of-the-art in flutter prediction capabilities and design rules, the FUTURE project will lead to benefits in terms of decreased development cost, reduced weight and fuel consumption, and increased ability to efficiently manage flutter problems occurring on engines at service. Eight interconnected turbine and compressor experiments will be performed in the project, in combination with numerical modelling of vibrating blades and the related unsteady aerodynamics. Cascade experiments will be employed to study unsteady aerodynamic properties in detail. These tests are supporting more complex rotating turbomachinery tests (turbine and compressor) to study the addressed phenomenon in engine-typical environment. The knowledge from both component tests will be then condensed into best practice for both experimental and computational (CFD) set-ups, and will be used towards a combined effort of physical understanding of travelling waves and interferences between the vibrating structures and the surrounding fluid. The acquired knowledge is aimed to be employed by the aeroelastic specialists in the companies, research institutes and universities to identify updated and better aeromechanical design rules. In the process of reaching this unique knowledge status a sophisticated, not yet available, measuring technique will be developed, and a new excitation mechanism will be implemented as back-up to the free-flutter experiments. Furthermore, a unique database with combined structural and unsteady aerodynamic results will be established and made available for further dissemination among the partners. This database will contain significantly more detailed data than any other existing database in the world.

Agency: European Commission | Branch: FP7 | Program: CP-IP | Phase: AAT.2011.1.4-2. | Award Amount: 67.80M | Year: 2011

The main objective of the LEMCOTEC project will be the improvement of core-engine thermal efficiency by increasing the overall pressure ratio (OPR) to up to 70 leading to a further reduction of CO2. Since NOx increases with OPR, combustion technologies have to be further developed, at the same time, to at least compensate for this effect. The project will attain and exceed the ACARE targets for 2020 and will be going beyond the CO2 reductions to be achieved by on-going FP6 and FP7 programmes including Clean Sky: 1.) CO2: minus 50% per passenger kilometre by 2020, with an engine contribution of 15 to 20%, 2.) NOx: minus 80% by 2020 and 3.) Reduce other emissions: soot, CO, UHC, SOx, particulates. The major technical subjects to be addressed by the project are: 1.) Innovative compressor for the ultra-high pressure ratio cycle (OPR 70) and associated thermal management technologies, 2.) Combustor-turbine interaction for higher turbine efficiency & ultra-high OPR cycles, 3.) Low NOx combustion systems for ultra-high OPR cycles, 4.) Advanced structures to enable high OPR engines & integration with heat exchangers, 5.) Reduced cooling requirements and stiffer structures for turbo-machinery efficiency, 6.) HP/IP compressor stability control. The first four subjects will enable the engine industry to extend their design space beyond the overall pressure ratio of 50, which is the practical limit in the latest engines. Rig testing is required to validate the respective designs as well as the simulation tools to be developed. The last two subjects have already been researched on the last two subjects by NEWAC. The technology developed in NEWAC (mainly component and / or breadboard validation in a laboratory environment) will be driven further in LEMCOTEC for UHPR core engines. These technologies will be validated at a higher readiness level of up to TRL 5 (component and / or breadboard validation in a relevant environment) for ultra-high OPR core-engines.

Agency: European Commission | Branch: FP7 | Program: BSG-SME | Phase: SME-2013-1 | Award Amount: 1.65M | Year: 2014

The EcoJet consortium comprising a value chain of three European SME manufacturers of gas turbines and sub-systems, and suppliers of high-performance materials and coatings, together with an SME developer of CHP systems - aims to address a major market opportunity through the optimization and deployment of a proprietary 10 KWe radial micro gas turbine into an innovative system solution tailored for environmentally friendly micro CHP applications for the residential sector. EcoJet targets the development of an engine based on an innovative radial jet turbine with an integrated electric generator. The technology has a uniquely robust design and uses very few advanced components, which makes it inexpensive and simple to manufacture. As existing micro turbine technology, it is multi-fuel enabled; has a high power to weight ratio, low emissions; no vibration and noise. As a core novelty and differentiator, the EcoJet design simultaneously enables environmentally superior performance and cost-effective uptake of micro CHP compared to conventional reciprocating engine generators. The concept addresses S&T barriers related to materials selection and assessment and to the production of the monorotor and heat exchanger. The EcoJet solution has a range of unique selling propositions to a very large group of potential end-users manufacturers of micro CHP systems and, ultimately, households which, in addition to economic benefits, can contribute to the mitigation of environmental problems due to a reduction in energy consumption and emissions. The SME consortium has the capacity to produce and market the new solution, but lacks the financial resources as well as the research expertise that enable the required technological development. Therefore, the consortium has identified the Research for the Benefit of SMEs Programme as the suitable vehicle for overcoming the technological and financial barriers associated with the achievement of the projects objectives.

Cox G.D.,PCA Engineers Ltd
Proceedings of the ASME Turbo Expo | Year: 2012

The modern trends in automotive turbocharger applications are towards the boosting of smaller internal combustion engines and more advanced systems including twostage, turbo-compounding and hybrid electric-motor assist. Off-the-shelf turbochargers will become a smaller share of the market and the choice of major parameters for the compressor and turbine, e.g. speed and diameter, will fall outside of the manufacturer's knowledge base. The selection of the compressor and turbine may even be independent. The only certainty is that the turbomachinery will have to be small, cheap and efficient. To provide some guidance to the turbine designer, this paper presents the results of a study in which practical designs have been generated to cover the range of conceivable parameters, presented in non-dimensional terms to provide general applicability. All the designs are generated using a throughflow-based optimisation system in which the candidate geometries are assessed against mechanical as well as aerodynamic and inertia targets. Analysis of the results gives clues to the form of the basic empiricism that would be of use in the preliminary design of automotive turbocharger turbines. Copyright © 2012 by ASME.

Casey M.,PCA Engineers Ltd | Casey M.,University of Stuttgart | Rusch D.,ABB
Journal of Turbomachinery | Year: 2014

The matching of a vaned diffuser with a centrifugal impeller is examined with a onedimensional (1D) analysis combined with extensive experimental data. A matching equation is derived to define the required throat area of the diffuser relative to the throat area of the impeller at different design speeds and validated by comparison with a wide range of compressor designs. The matching equation is then used to give design guidelines for the throat area of vaned diffusers operating with impellers at different tip-speed Mach numbers. An analysis of test data for a range of high pressure ratio turbocharger compressor stages is presented in which different matching between the diffuser and the impeller has been experimentally examined. The test data includes different impellers with different diffuser throat areas over a wide range of speeds. It is shown that the changes in performance with speed and diffuser throat area can be explained on the basis of the tip-speed Mach number which causes both the diffuser and impeller to choke at the same mass flow. Based on this understanding, a radial compressor map prediction method is extended to include this parameter, so that more accurate maps for matched and mismatched vaned diffusers can be predicted. © VC 2014 by ASME.

Casey M.V.,PCA Engineers Ltd | Casey M.V.,University of Stuttgart | Robinson C.J.,PCA Engineers Ltd
Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy | Year: 2011

An equation is derived that relates the changes in turbomachinery efficiency with Reynolds number to the changes in the friction factor of an equivalent flat plate. This equation takes into account the different Reynolds number and roughness dependencies of the individual components, and can be used for whole stages and multistage machines. The new method is sufficiently general to correct for changes in Reynolds number due to changes in fluid properties or speed, changes in machine size, or changes in the surface roughness of components for all types of turbomachinery, but is calibrated here for use on axial and radial compressors. The method uses friction factor equations for a flat plate which include fully rough behaviour above an upper critical Reynolds number, a transition region depending on roughness and a region with laminar flow below the lower critical Reynolds number. The correction equation for efficiency includes a single empirical factor. Based on a simple loss analysis and a calibration with over 30 sets of experimental test data covering a wide range of machine types, a suggestion for the variation of this factor with specific speed has been made. Additional correction equations are derived for the shift in flow and the change in pressure rise with Reynolds number and these are also calibrated against the same data. © 2011 Authors.

Casey M.,PCA Engineers Ltd | Robinson C.,PCA Engineers Ltd
Journal of Turbomachinery | Year: 2013

A novel approach to calculate the performance map of a centrifugal compressor stage is presented. At the design point four nondimensional parameters (the flow coefficient φ, the work coefficient λ, the tip-speed Mach number M, and the efficiency η) characterize the performance. In the new method the performance of the whole map is also based on these four parameters through physically based algebraic equations which require little prior knowledge of the detailed geometry. The variable empirical coefficients in the parameterized equations can be calibrated to match the performance maps of a wide range of stage types, including turbocharger and process compressor impellers with vaned and vaneless diffusers. The examples provided show that the efficiency and the pressure ratio performance maps of turbochargers with vaneless diffusers can be predicted to within ±2% in this way. More uncertainty is present in the prediction of the surge line, as this is very variable from stage to stage. During the preliminary design the method provides a useful reference performance map based on earlier experience for comparison with objectives at different speeds and flows. © 2013 American Society of Mechanical Engineers.

Casey M.,University of Stuttgart | Robinson C.,PCA Engineers Ltd
Journal of Turbomachinery | Year: 2010

This paper describes a newly developed streamline curvature throughflow method for the analysis of radial or mixed flow machines. The code includes curved walls, curved leading and trailing edges, and internal blade row calculating stations. A general method of specifying the empirical data provides separate treatment of blockage, losses, and deviation. Incompressible and compressible fluids are allowed, including real gases and supersonic relative flow in blade rows. The paper describes some new aspects of the code. In particular, a relatively simple numerical model for spanwise mixing is derived; the calculation method for prescribed pressure ratio in compressor blade rows is described; and the method used to redistribute the flow across the span due to choking is given. Examples are given of the use and validation of the code for many types of radial turbomachinery, and these show that it is an excellent tool for preliminary design. © 2010 by ASME.

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