Braking distance prediction for vehicle consist in low-speed on-sight operation:a Monte Carlo approach

The first and last mile of a railway journey, in both freight and transit applications, constitutes a high effort and is either non-productive(e.g. in the case of depot operations) or highly inefficient(e.g. in industrial railways). These parts are typically managed on-sight, i.e. with no signalling and train protection systems ensuring the freedom of movement. This is possible due to the rather short braking distances of individual vehicles and shunting consists. The present article analyses the braking behaviour of such shunting units. For this purpose, a dedicated model is developed. It is calibrated on published results of brake tests and validated against a high-definition model for lowspeed applications. Based on this model, multiple simulations are executed to obtain a Monte Carlo simulation of the resulting braking distances. Based on the distribution properties and established safety levels, the risk of exceeding certain braking distances is evaluated and maximum braking distances are derived. Together with certain parameters of the system, these can serve in the design and safety assessment of driver assistance systems and automation of these processes.

Experimental and numerical investigations of the dry-low-NO_(x) hydrogen micromix combustion chamber of an industrial gas turbine

Combined with the use of renewable energy sources for its production,hydrogen represents a possible alternative gas turbine fuel within future low emission power generation.Due to the large difference in the physical properties of hydrogen compared to other fuels such as natural gas,well established gas turbine combustion systems cannot be directly applied for dry-low-NO_(x)(DLN)hydrogen combustion.Thus,the development of DLN combustion technologies is an essential and challenging task for the future of hydrogen fuelled gas turbines.The DLN micromix combustion principle for hydrogen fuel has been developed to significantly reduce NO_(x) emissions.This combustion principle is based on cross-flow mixing of air and gaseous hydrogen which reacts in multiple miniaturized diffusion-type flames.The major advantages of this combustion principle are the inherent safety against flash-back and the low NO_(x) emissions due to a very short residence time of reactants in the flame region of the micro-flames.The micromix combustion technology has been already proven experimentally and numerically for pure hydrogen fuel operation at different energy density levels.The aim of the present study is to apply and compare different combustion models for the characterization of the micromix flame structure,its interaction with the flow field and its NO_(x) emissions.The study reveals great potential for the successful application of numerical flow simulation to predict flame structure and NO_(x) emission level of micromix hydrogen combustion,help understanding the flow phenomena related with the micromixing,reaction zone and NO_(x) formation and support further optimization of the burner performance.

CFD based exploration of the dry-low-NO_(x) hydrogen micromix combustion technology at increased energy densities

Combined with the use of renewable energy sources for its production,hydrogen represents a possible alternative gas tuibine fuel within future low emission power generation.Due to the large difference in the physical properties of hydrogen compared to other fuels such as natural gas,well established gas tuibine combustion systems cannot be directly applied for dry-low-NO_(x)(DLN)hydrogen combustion.Thus,the development of DLN combustion technologies is an essential and challenging task for the future of hydrogen fuelled gas turbines.The DLN micromix combustion principle for hydrogen fuel has been developed to significantly reduce NO_(x)-emlssions.This combustion principle is based on cross-flow mixing of air and gaseous hydrogen which reacts in multiple miniaturized diffusion-type flames.The major advantages of this combustion principle are the inherent safety against flash-back and the low NO_(x)-emlssions due to a very short residence time of reactants in the flame region of the micro-flames.The micromix combustion technology has been already proven experimentally and numerically for pure hydrogen fuel operation at different energy density levels.The aim of the present study is to analyze the influence of different geometry parameter variations on the flame structure and the NO_(x)emission and to identify the most relevant design parameters,aiming to provide a physical understanding of the micromix flame sensitivity to the burner design and identify further optimization potential of this innovative combustion technology while increasing its energy density and making it mature enough for real gas turbine application.The study reveals great optimization potential of the micromix combustion technology with respect to the DLN characteristics and gives insight into the impact of geometry modifications on flame structure and NO_(x)emission.This allows to further increase the energy density of the micromix burners and to integrate this technology in industrial gas turbines.

Improvement study for the dry-low-NO_(x) hydrogen micromix combustion technology

The dry-low-NO_(x)(DLN)micromix combustion principle is developed for the low emission combustion of hydrogen in an industrial gas turbine APU GTCP 36-300.The further decrease of NO_(x) emissions along a wider operation range with pure hydrogen supports the introduction of the micromix technology to industrial applications.Experimental and numerical studies show the successful advance of the DLN micromix combustion to extended DLN operation range.The impact of the hydrogen fuel properties on the combustion principle and aerodynamic flame stabilization design laws,flow field,flame structure and emission characteristics is investigated by numerical analysis using an eddy dissipation concept combustion model and validated against experimental results.