Modelling, simulation and validation of the operation of energy-efficient propulsion systems for hybrid-powered shunting locomotives

Demand for energy-efficient and low-emission propulsion long ago formed the driving force behind a rethink with regard to the development of railway rolling stock. The introduction of more stringent environmental standards is putting pressure on the operators of diesel locomotives to reduce emissions

such as harmful substances and noise. New fuel-saving strategies are needed, especially in order to reduce CO2 emissions. These are necessary, as diesel-powered shunting locomotives will continue to play an important role in rail traffic, due to the large number of situations in which they can be deployed. Their scope of operation extends from shunting work at passenger and goods railway stations to runs on medium-density routes that are unsuitable for electrification.

The importance of shunting locomotives in freight traffic, for transferring rolling stock, and for deliveries and workshop operations is confirmed by the current numbers of

heavy shunting locomotives, which has remained almost constant during the past few years. The shunting traffic carried out by those shunting locomotives however accounts for a significant proportion of the overall energy consumed by diesel-powered rolling stock. Not only is 12% of the total CO2 emissions of Deutsche Bahn AG (German Railways) generated by shunting activities, but that figure does not include activities on works railways, a higher proportion of which consist of shunting activities. Saving fuel costs will make a significant contribution towards the overall reduction in CO2 emissions, as well as reducing the quantity of harmful emissions that occur.

Project description

One approach that is very promising is to use hybrid drive systems instead of conventional diesel-powered drive systems. Although hybrid technology has been a familiar concept in road vehicles for a long time, hardly any attention has been paid to the issue in the case of railway vehicles. Nevertheless, potential energy savings of up to 70% when compared to conventional shunting locomotives are certainly realistic.

This was the result of a study at the Nuremberg Institute for Automotive Engineering (IFZN) into the potential energy-saving that theoretically could be achieved. In order to enable those benefits to be achieved in the case of rail vehicles, the first step must be to take account of suitable drive configurations and operating modes in a given area of deployment. Due to the fact that in those areas, the possibilities vary and not all drives can be built and tested, the IFZN took on the task of creating loadable simulation models, which would ultimately make it possible for the hybrid concepts and operating strategies to be optimized. To guarantee that the simulation is as realistic as possible, it is necessary for the models to be continually validated using figures obtained in practice. The measurement data necessary for that purpose will be captured by Deutsche Bahn AG and the IFZN using a prototype locomotive and made available to the research project that will create the model. The aim of the research project into hybrid shunting locomotives is to create simulation models of individual components, with which the effects of the drive configurations can be simulated and optimized with regard to the necessary power levels (engines, energy storage, auxiliary systems) and in line with the demands and functions required of control systems.

Progress and simulation environment

To develop the simulation model, the physical system simulation will be provided by means of a software package. The choice of a suitable simulation environment will directly affect the usability and the future possibilities to expand the simulation calculations. The simulation environment eventually selected was the software package SimulationX. As Figure 3 makes clear, the software package is already in use for motor vehicles and utility vehicles. As only few of the modules available from the automotive sector are fully suitable for use in the project, specific modules that can be used for railway vehicles will need to be designed. This stage will take up most of the time available during the project. In addition to simulating the controls, SimulationX also makes it possible for a physical model to be developed, which is the reason why the program turned out to form a suitable solution. The individual modules are intended to describe not only the essential parameters of hybrid locomotives, but also of the carriages or wagons hitched to them. Once the data has been captured, it will need to be transferred into the relevant modules. In all subsequent examinations, the travel cycles of shunting locomotives will form a key component. These will include all information of relevance to the drive profile and speed profile, the loads hauled, and the duration and frequency of stops.

Based on the travel cycles that form part of shunting operations at Nuremberg Central Station, additional travel cycles can be created synthetically using the software. After that, the information obtained will need to be heavily compressed using statistical processes, so that further driving cycles can be generated artificially, based on the data captured. That way, the process should make it possible to achieve a precise simulation of the system’s actual behaviour, without measuring the routes concerned or being required to drive along them in real life. Despite the fact that different types of locomotive are used to perform the same driving cycles, a comparability will nevertheless be established that will be representative and characteristic of the desired vehicle concepts.

Prospects

Following the introduction of the H3 hybrid locomotives (Figure 1) in autumn 2015, the IFZN started to collect data. Once the first operational results are available, these will be evaluated and incorporated into the simulation. The subsequent planning and review stages will take a further six months, such that any possible optimizations of hybrid concepts can be expected by the third quarter of 2016.

Ultra-clean and efficient generation, recovery, and emission of heat within smart macrocellular combustion reactors

Flameless combustion is a modern combustion technology that provides significant benefits compared to conventional open-air combustion. Low emissions of harmful substances, high radiated power, and a broad power modulation spectrum form the outstanding
features of this combustion technique. The possibilities and limits of this innovative combustion method are currently being analysed in a research project at Nuremberg Institute of Technology. The aim of the “Smart combustion reactors” project is to research and develop an optimum combustion reactor architecture, thereby achieving an efficient and
low-emission heat generator for industrial applications.

Smart combustion reactors

The special architecture of the combustion reactors makes it possible to reduce the maximum temperature level during combustion. This is achieved due to the porous ceramic structure of the reactor, which also serves the purpose of heat recovery. The deterministic structure of the reactor also enables a homogeneous temperature distribution across the entire volume of the reactor. This serves to localize inequalities, known as “hotspots”. Due to the interaction of heat storage and heat decoupling (heat recovery) in the reactor, a high degree of power modulation is achieved, without reducing the quality of the combustion process itself.

Research strategy/progress of project

In order to render the benefits of flameless combustion usable in industrial applications, research must first be carried out into the issues regarding the physical and thermodynamic processes in the combustion reactor itself. In that regard, the focus will especially lie on the suitability of the reactors and on the materials engineering and technological aspects of the macrocellular reactors, so that in the next step, the product development of an industrial reactor heat emitter can be achieved.

The benefits of flameless combustion

The project not only opens up new possibilities in terms of industrial applications. Due to the fact that it brings about a significant increase in efficiency and a significant reduction in emissions, this type of combustion
is making a considerable contribution towards the establishment of clean technologies within in energy-intensive industrial
processes. As well as reducing costs and energy consumption, this optimized combustion process makes it possible to bring emissions of harmful substances such as nitrogen oxides (NOx), carbon monoxide (CO) and hydrocarbons (HC) down to a minimum. The project entitled “Smart combustion engines” – a collaboration between Nuremberg Institute of Technology and its project partner Promeos GmbH – will make it possible for regenerative energy sources to be used directly, thereby achieving a significant reduction in CO2 emissions.