Sensitivity analysis of centrifugal compressors aerodynamic losses using 1D-mean streamline prediction technique

One-dimensional modeling and prediction of the centrifugal compressor performance are challenging as they require conservation equations and empirical and semi-empirical correlations. Therefore, there is a need to perform a consolidated study of the compressor aerodynamic loss models to conclude the importance of each loss to the compressor performance modeling. Accordingly, the purpose of this paper is to examine the effect of each aerodynamic loss on the compressor performance and explore more about which loss could have a negligible effect on the compressor performance. A MATLAB code was developed to predict the performance of five different small turbocharger centrifugal compressors at different geometric and operating conditions. The developed code was validated using the available experimental data of the investigated compressors. A sensitivity analysis methodology was performed using the validated code to check the effect of ten aerodynamic losses for the impeller and volute sections on the compressor performance. This paper concludes that impeller disk friction, blade loading, and clearance losses have a negligible effect on the small turbocharger vanless diffuser compressor performance.

Application of computational gas dynamics methods for calculating losses during rotation of solids in low vacuum conditions

On the basis of a mathematical model with distributed parameters, a method for determining aerodynamic losses during high-frequency rotation of a flywheel accumulator is developed. The power of losses due to friction of the rotor against the air is determined as a function of the pressure in the chamber. A comparative analysis of the aerodynamic losses under low vacuum conditions at various pressures of the working medium and the data obtained on the basis of empirical dependences and presented in the scientific literature on this topic is carried out. The maximum difference between the loss power values is no more than 25%. The data deviation decreases as the pressure in the chamber decreases.

Design of Heat Shield for Compressor Case of Industrial Gas Turbine to Meet Clearance Requirement

In Gas Turbine design key important role was to establish proper clearance between rotating and statoric parts during operating conditions which controls the performance, cooling flow requirements, part performance etc., These clearances must be optimized to meet product requirements. Too tight clearance at assembly condition causes excessive rubbing during starting or shutdown of gas turbine which could cause excessive heat generation and damage rotating and statoric parts. In some case, rubbing can cause tip liberations and damages to flow path causing aero dynamic losses. Similarly, if clearance is large at assembly condition causes aerodynamic losses. In this paper describes the experience of Baker Hughes, in design of compressor case wherein different design options in casing design with and without considering external features / components are considered to have adequate clearance between rotating and statoric parts. It also describes the Heat shield design iterations which was provided on a compressor case to establish proper thermal response during transient operating conditions. This helps in providing adequate clearance without causing excessive rubs or too large clearance avoiding aerodynamic losses. During development of heat shield design, challenges encountered considering clearance, manufacturing aspects, assembly feasibility and part life capabilities like low cycle fatigue, high cycle fatigue requirements are discussed in the paper. Also heat shield was subjected to high thermal gradient due to temperature difference, this makes heat shield to have constrained growth. This restriction in growth provides huge stresses beyond the material limit causing it to fail before product requirement time period. To avoid constrained growth, this paper describes how the heat shield was connected to casing by different means are mentioned. It also describes the impact on frequency margin if there is not adequate fixity in heat shield design. Some of the design parameters like circumferential & axial ribs and intermittent stiffeners and its influence on stress by comparing against yield and on frequency margin with reference to potential driver are also discussed in this paper. It also incorporates the methods to control intersegment leakages and design features to avoid interface interference. Feasibility study of heat shield design was done using finite element modeling techniques using ANSYS tool and its best practices would also be dealt in this paper.

Optimization of a3D Aircraft Morphing Wing with highly controllable Aerodynamic Performance

the sole purpose of this project is to compare the aerodynamic performance of the modernistic wing with morphing techniques to the conventional one (i.e. wing with ailerons and flaps). The morphing wing is capable of enhancing the mission profiles through its significant geometrical changes in the surface areas (upper and lower area of wing). The primary aspiration is to calculate the CL and CD (coefficient of lift and drag) of real aircraft with conventional control surfaces and to compare its result with morphing wing. The morphing techniques also enables various prevention of aerodynamic losses (drag, vortices, noise, etc) caused due to geometrical discontinuities of conventional wing with aileron and flap in operating conditions (take-off, cruise, loiter, landing).Catia modelling of proposed wing is analysed by CFD method and to compare and contrast the aerodynamic performance with the conventional (hinged) wing.

Second Law Analysis of Condensing Steam Flows

A numerical second law analysis is performed to determine the entropy production due to irreversibilities in condensing steam flows. In the present work, the classical approach to calculate entropy production rates in turbulent flows based on velocity and temperature gradients is extended to two-phase condensing flows modeled within an Eulerian–Eulerian framework. This requires some modifications of the general approach and the inclusion of additional models to account for thermodynamic and kinematic relaxation processes. With this approach, the entropy production within each mesh element is obtained. In addition to the quantification of thermodynamic and kinematic wetness losses, a breakdown of aerodynamic losses is possible to allow for a detailed loss analysis. The aerodynamic losses are classified into wake mixing, boundary layer, and shock losses. The application of the method is demonstrated by means of the flow through a well-known steam turbine cascade test case. Predicted variations of loss coefficients for different operating conditions can be confirmed by experimental observations. For the investigated test cases, the thermodynamic relaxation contributes the most to the total losses and the losses due to droplet inertia are only of minor importance. The variation of the predicted aerodynamic losses for different operating conditions is as expected and demonstrates the suitability of the approach.