Uncertainty Quantification Methodologies Applied to the Rotor Tip Clearance Effect in a Twin Scroll Radial Turbine

In the last three decades computer simulation tools have achieved wide spread use in the design and analysis of engineering devices. This has shortened the overall product design cycle (physical experiments may be impossible during early design stages) and it has also provided better understanding of the operating behavior of the systems under investigation. As a consequence numerical simulation have led to a reduction of physical prototyping and to lower costs for manufacturing production chains. Despite this success, it remains difficult to provide objective confidence levels in quantitative information derived from numerical predictions. The complexity arises from the amount of uncertainties related to the inputs of any computation attempting to represent a physical system. This paper focuses on geometrical sources of uncertainty in the field of CFD applied to twin scroll radial turbines. In particular it has been investigated the effect of uncertainties on tip clearance values at rotor blade leading edge and trailing edge on selected turbine performance parameters. The analysis shows the use of the Surrogate-based uncertainty quantification technique that has been setup by the authors in the Dakota(R)environment. The polynomial chaos expansion method has been applied to the same case. The comparison of the results coming from the different approaches and the discussion of the pros and cons related to each technique lead to interesting conclusions, which are proposed as guidelines for future UQ applications on the theme of CFD applied to radial turbines

The Use of CFD for the Design and Development of Innovative Configurations in Regenerative Glass Production Furnaces

The limitation of nitrogen oxides emissions is nowadays a challenge in several engineering fields. Recent European regulations have reduced the maximum NOx emissions and therefore forced the glass production sector to develop emission reduction strategies. Two different systems have been developed within the framework of the European LIFE project and are currently applied to glass regenerative furnaces: the Waste Gas Recirculation (WGR) and the Hybrid Air Staging (HyAS). The above systems are primary NOx reduction strategies because they both operate to control the combustion evolution. Both WGR and HyAS systems have been conceived with the extensive use of Computational Fluid Dynamics (CFD) models: design strategies for both systems have been developed based on the use of CFD and are currently under use by glass furnace designers. In the present work, the CFD procedures routinely used for the design of the above systems are described. The systems effectiveness, due to the harsh conditions in the industrial installation, can be tested with oxygen concentration measurements inside the regenerators. The oxygen concentration is correlated to the flame evolution and therefore to the nitrogen oxides formation. For the above reason, the models have been validated with experimental data from pilot furnaces using measured values of O2 mole fraction. The CFD procedures are described in the paper together with their application to different configurations

Marine gas turbine monitoring and diagnostics by simulation and pattern recognition

Several techniques have been developed in the last years for energy conversion and aeronautic propulsion plants monitoring and diagnostics, to ensure non-stop availability and safety, mainly based on machine learning and pattern recognition methods, which need large databases of measures. This paper aims to describe a simulation based monitoring and diagnostic method to overcome the lack of data. An application on a gas turbine powered frigate is shown. A MATLAB-SIMULINK\uae model of the frigate propulsion system has been used to generate a database of different faulty conditions of the plant. A monitoring and diagnostic system, based on Mahalanobis distance and artificial neural networks have been developed. Experimental data measured during the sea trials have been used for model calibration and validation. Test runs of the procedure have been carried out in a number of simulated degradation cases: in all the considered cases, malfunctions have been successfully detected by the developed model

ANALYSIS OF A ROCK SLOPE FAILURE IN A LIMESTONE OPEN PIT

The proposed paper is aimed at analysing a rock slope failure that occurred in a sector of an open pit quarry. The failed rock volume was not large, it had a significant impact on the mining operations and the safety of the district road which runs very close to the quarry site. An evaluation of the possible failure mechanisms is given, which was based on a structural description of the rock mass, a mechanical laboratory characterisation of the rock and of rock joints, and on the environmental and exploitation condition. The analysis referred to schemes that could explain the degree of instability of the rock slope. Kinematical analyses, block theory and limit equilibrium were applied and evaluations were also obtained by using DEM models to estimate the static behavior and possible effects induced by quarry blasts of the rock slope

A comparison of strategies to extend the operating range of radial compressors for turbocharging

The operating range extension of radial compressors is a crucial aspect in turbocharging the internal combustion engines in order to extend the operating range of the system at high efficiency for fuel and environmental impact reduction. The future scenario of automotive propulsion will have the fuel cells at the top of the ranking of possible reference systems in substitution of thermal reciprocating engines. Proton exchange membrane fuel cells for automotive or aerospace vehicles are frequently turbocharged because compressed air for the fuel cell stack is required in the cathode system. Therefore, like in turbocharged internal combustion engines, a radial compressor is combined and connected with a radial turbine to exploit the thermal energy of the exhaust gas from the fuel cell. The study and the development of this sort of radial turbomachinery is still strategic to guarantee high performance of the overall propulsion system. The operating range is an important issue and current turbocharger design must be adapted to the new requirements of the fuel cells systems with a need for extending it. Various techniques to extend the operating range of the centrifugal compressor have been investigated and a summary is reported in this work, with a focus on the casing treatment. Through a CFD simulation campaign with appropriate simplified models, the effects of installing the ported shroud, the shutter or the axial groove have been calculated with respect to a baseline configuration. These simulations have supported the identification of the main limits and advantages for each of these solutions at different operating regimes. The performance maps and some physical parameters of interest have been compared