Cold air performance of a 12.766-centimeter-tip-diameter axial-flow cooled turbine. 2: Effect of air ejection on turbine performance

An air cooled version of a single-stage, axial-flow turbine was investigated to determine aerodynamic performance with and without air ejection from the stator and rotor blades surfaces to simulate the effect of cooling air discharge. Air ejection rate was varied from 0 to 10 percent of turbine mass flow for both the stator and the rotor. A primary-to-air ejection temperature ratio of about 1 was maintained

A Computer Program for the Coupled Implementation of Meanline and Throughflow Methods to Simplify the Aerodynamic Design of Multistage Axial Compressors

A computer program capable of simplifying the preliminary aerodynamic design process of multistage axial compressors has been developed. This interactive design tool, named C-STAAC, combines the Meanline and Throughflow analysis capabilities of two independent compressor design codes to form one standalone system. The program greatly improves the efficiency of the Preliminary-to-Throughflow stages of compressor design by providing fully coupled interaction between the two platforms. The result enables the user to produce stacked airfoil geometry from only a handful of initial input parameters. The program additionally offers a wide selection of pre- and post-processing capabilities that were not previously available with the independent design codes. This tool is accessed through an easy-to-use graphical user interface that allows for immediate visual feedback during design iterations, thus increasing user productivity and design turnaround time. An equivalent industry-standard process may take a substantial amount of time and effort. The unique “from scratch” design capabilities of C-STAAC are explained in complete detail, and the program’s abilities are demonstrated with illustrated examples

Computer aided design of twin screw compressors

The twin screw refrigeration compressor is required to run over a large range of working conditions. In order to design an advanced and high-efficiency compressor economically, computer aided design techniques are required. This thesis presents such techniques, which include profile generation, geometrical characteristic calculation, working process simulation, rotor cutter blade calculation and optimisation techniques. All the basic theory and equations and the derived equations are presented. Four important computer programs, ie the profile generation program, the geometrical characteristics calculation program, the working process simulation program and the cutter blade calculation program, are developed and presented in the thesis. A few other support programs are also developed by the author to display the calculated results. All the programs developed form a program library for the CAD of twin screw compressors. All the programs except the profile generation program are universal, which means that they can be used for any shape of rotor profile. For the working process simulation program, only refrigeration twin screw compressors are considered, but it is easy to extend the use of the programs to other kinds of compressor. The thermodynamic effects of the following are discussed and taken into account: internal leakage of gas through all paths; oil, injected and drained from bearings; refrigerant injection, both gaseous and liquid; the flashing of injected refrigerant and that dissolved in oil; friction effects, in both end and main casings; the use of measured performance data in the determination of essential empirical coefficients in the mathematical model. The application of the programs and the design optimisation technique are presented, which include leakage analysis, compressor geometrical parameter optimisation, rotor-to-rotor clearance distribution optimisation and cutter blade shape optimisation etc. The author believes that the research work presented in this thesis is of practical value. Further, it presents new knowledge: of the compression start blow hole and its influence; of leakage quantitative analysis; of compressor design optimisation; of the quantitative analysis of the influence of different determination procedures of inter-rotor clearances.The twin screw refrigeration compressor is required to run over a large range of working conditions. In order to design an advanced and high-efficiency compressor economically, computer aided design techniques are required. This thesis presents such techniques, which include profile generation, geometrical characteristic calculation, working process simulation, rotor cutter blade calculation and optimisation techniques. All the basic theory and equations and the derived equations are presented. Four important computer programs, ie the profile generation program, the geometrical characteristics calculation program, the working process simulation program and the cutter blade calculation program, are developed and presented in the thesis. A few other support programs are also developed by the author to display the calculated results. All the programs developed form a program library for the CAD of twin screw compressors. All the programs except the profile generation program are universal, which means that they can be used for any shape of rotor profile. For the working process simulation program, only refrigeration twin screw compressors are considered, but it is easy to extend the use of the programs to other kinds of compressor. The thermodynamic effects of the following are discussed and taken into account: internal leakage of gas through all paths; oil, injected and drained from bearings; refrigerant injection, both gaseous and liquid; the flashing of injected refrigerant and that dissolved in oil; friction effects, in both end and main casings; the use of measured performance data in the determination of essential empirical coefficients in the mathematical model. The application of the programs and the design optimisation technique are presented, which include leakage analysis, compressor geometrical parameter optimisation, rotor-to-rotor clearance distribution optimisation and cutter blade shape optimisation etc. The author believes that the research work presented in this thesis is of practical value. Further, it presents new knowledge: of the compression start blow hole and its influence; of leakage quantitative analysis; of compressor design optimisation; of the quantitative analysis of the influence of different determination procedures of inter-rotor clearances

Design and optimization of fuel injection of a 50 kW micro turbogas

The present article deals with the design of a micro turbogas turbine suitable for on board applications, e.g., as a power generator on hybrid transit bus, characterized by a simple constructive approach. Deriving the machine layout from an existing KJ-66 aircraft model engine, the authors propose a theoretical design of a compact, lightweight turbogas turbine, by investigating the technical possibility and limits of the proposed design. In particular, a different combustion chamber layout has been proposed, and fuel adduction channels for different swirler designs have been simulated via ANSYS Fluent in order to identify a satisfactory fuel spreading. As a result, the complete characterization of the design parameters and geometries has been performed, and a series of RANS simulations has been used in order to identify an optimal swirler configuration

Computational thermo-fluid dynamics contributions to advanced gas turbine engine design

The design practices for the gas turbine are traced throughout history with particular emphasis on the calculational or analytical methods. Three principal components of the gas turbine engine will be considered: namely, the compressor, the combustor and the turbine

Multidisciplinary Design of Transonic Fans for Civil Aeroengines

For current state-of-the-art turbofan engines the bypass section of the fan stage alone provides the majority of the total thrust in cruise and the size of the fan has a considerable effect on overall engine weight and nacelle drag. Thrust requirements in different parts of the flight envelope must also be satisfied together with sufficient margins towards stall. A complex set of system requirements and objectives, combined with component technology of high maturity level, demands performance predictions with higher accuracy that are sensitive to more detailed design features at an early conceptual design phase. Failing to meet these demands may result in a sub-optimal choice of aircraft-engine system architecture.The emphasise of this thesis work is on fan-stage design and performance prediction in terms of aerodynamic efficiency and stability. The aspect of accuracy when it comes to establishing engine cycle performance for existing state-of-the-art technology based on open literature data is undertaken in the first paper. In the second paper a strategy to expand the parameter interdependencies of a fan-stage performance model with a multidisciplinary perspective is explored. The resulting model is integrated into an engine systems model and coupled with a simplified weight model to investigate the trade-off between weight and specifc fuel consumption. Results implied that being able to predict the rotor solidity required to maintain a given average blade loading - in addition to stage efficiency - is of high importance

Conceptual Thermodynamic Cycle and Aerodynamic Gas Turbine Design - on an Oxy-fuel Combined Cycle

The world is today facing a serious problem with global warming, which is heading towards an appallingly high temperature level. The greater part of the overall climate science community agree that global warming is caused by the greenhouse effect, which depends largely on emitted CO2 emissions from the combustion of fossil fuel. The agreement at the COP 21 climate meeting in Paris (December 2015) was that global warming must be limited to no more than + 2.0 C, with the aim of keeping it below + 1.5 C. Accomplishing this requiresa concerted effort in several different areas, for example through increased energy efficiency, more renewable energy sources and the utilization of carbon capture and sequestration (CCS) technology. The oxy-fuel combined cycle (OCC), which is the topic of this thesis, is a subcategory of oxy-fuel combustion which, in turn is one of the three main technologies for CCS today. The key idea with oxy-fuel combustion is to avoid mixing the CO2 formed in the combustion withthe non-condensable nitrogen, as occurs at the combustion in a conventional combined cycle power plant (CCPP). This is achieved by combusting the gas fuel with pure oxygen (O2) and thereby forming a combustion product consisting of only steam (H2O) and carbon dioxide (CO2). The CO2 can then be separated downstream of the HRSG by condensing out the H2O and thereby leaving a pure stream of CO2 for sequestration. The OCC consists of a topping Brayton cycle and a bottoming Rankine cycle and has many similarities with a conventional CCPP. In the OCC, however, the flue gas leaving the HRSG is recirculated back to the gas turbine units compressor inlet, instead of being emitted to the atmosphere as in a CCPP. Thereby, the combustion products also act as the working medium in the topping (gas turbine) cycle. The working medium has a composition of about 85 wt.-% CO2, 10 wt.-% H2O and a few percentage points of enriched nitrogen and argon, which follows with the oxygen stream as impurities. The CO2-rich working medium has significantly different gas properties, compared to air and conventional flue gas. This affect the design of the topping cycle, the exhaust heat utilization in the HRSG, the design requirements for the gas turbine unit and the aerodynamic design of its compressor and turbines. One of the major effects on the design, is the requirement for a higher gas turbine pressure ratio than for a conventional CCPP, as a result of the lower isentropic exponent for the CO2-rich working medium. This thesis takes the OCC concept to the next technical readiness level not just by identifying, optimizing and proposing a cycle design for a 115 MWel OCC. It also addresses the conceptual design of a gas turbine unit suitable for an OCC and a quite detailed conceptual aerodynamic design for the gas turbines unit’s turbomachineries, i.e. one compressor and two turbines. The work investigated the performance levels to be expected from both the entire OCC, the embedded gas turbine unit and its turbomachineries. The proposed gas turbine unit was a single-shaft gas generator with a free direct-driven power turbine. The conceptual turbomachinery design of the compressor, the compressor turbine and the power turbine covered the conceptual design loop of the 1D mid-span, the 2D through-flow, and the 3D steady-state calculations. The compressor design was a 16-stage design, with a mass flow of 220 kg/s and a pressure ratio of 31.0. The turbine design was a two-stage compressor turbine and a four-stage power turbine. The oxy-fuel combined cycle was calculated to have an overall net efficiency of 48.2%, which includes the energy cost for the CO2 compression to 140 bar and the external O2 production in an air separation unit (ASU)

Identification of corner separation modelling in axial compressor stage

The paper presents a study of corner separations in hub to blade region at various operation conditions towards compressor stall. It is known that for compressor flows with low or none separations computation fluid dynamics with RANS methods work quite well, however, for highly separated flows they are no longer entirely valid. Therefore, several criteria were applied for prediction and quantification of possible corner separation, and the main interest of this work is in predicting the separation just before it will actually happen by certain flow metrics, so these metrics can be further used as a 'pre-stall' criteria whilst the RANS CFD operating point still behave within its appropriate limits. Also the effect of shear lean is discussed in the presented context. © The Authors, published by EDP Sciences, 2020

Computer program for aerodynamic and blading design of multistage axial-flow compressors

A code for computing the aerodynamic design of a multistage axial-flow compressor and, if desired, the associated blading geometry input for internal flow analysis codes is presented. Compressible flow, which is assumed to be steady and axisymmetric, is the basis for a two-dimensional solution in the meridional plane with viscous effects modeled by pressure loss coefficients and boundary layer blockage. The radial equation of motion and the continuity equation are solved with the streamline curvature method on calculation stations outside the blade rows. The annulus profile, mass flow, pressure ratio, and rotative speed are input. A number of other input parameters specify and control the blade row aerodynamics and geometry. In particular, blade element centerlines and thicknesses can be specified with fourth degree polynomials for two segments. The output includes a detailed aerodynamic solution and, if desired, blading coordinates that can be used for internal flow analysis codes

Optimal design of gas turbines flow paths considering operational modes

A new technique for multi-parameter optimization of gas turbines flow paths considering a variable mode for their operation is presented. It allow s the estimation of the influence of flow path optimization on performance parameters of gas-turbine units, such as power, efficiency, and fuel consumption. An algorithm for turbine flow path multi-criteria optimization that takes into account the gas-turbine unit operation mode is shown. Approaches to speed up the optimization process are described. Using this technique GT-750-6M low pressure turbine flow path optimization based on real working loads during one year is carried out and the results are analyzed. Due to optimization the unit efficiency was improved at all operating modes. The total fuel economy for considered period makes 50.831 t