The paper presents results of numerical simulations and experimental investigations of a cyclone with a square inlet and different dimensions of a vortex finder. Investigations were conducted for five, different cyclone models. The main goal of the research was to determine the influence of cyclone vortex finder geometry (diameter, length) on key parameters for a cyclone operation, such as: gas flow pattern, gas velocity and pressure distribution, pressure drop and collection efficiency. The analysis of flow pattern inside the cyclone was carried out with the use of CFD (Computational Fluid Dynamics) simulations, verified using CTA (Constant Temperature Anemometry). Similarly, pressure distributions, pressure drop and collection efficiency for cyclones were determined numerically and with measurements. The study demonstrated that dimensions of the vortex finder have a significant effect on a cyclone performance. The numerical visualisations of flow showed some unfavorable and beneficial effects and phenomena that may occur in cyclones. Moreover, the smallest pressure drop (305 Pa) was predicted for the cyclone with a maximum diameter of the vortex finder ($D_e$ = 0.105 m), the largest (358 Pa) when this diameter was the smallest ($D_e$ = 0.075 m). The tests did not show any significant influence of the vortex finder length on the pressure drop in a cyclone. A different tendency was observed in the case of collection efficiency. The maximum value of this parameter (89.5%) was predicted for the cyclone with the shortest vortex finder (s = 0.060 m), minimum (85.5%) when the vortex finder was the longest (s = 0.220 m). In this case, however, tests did not show a significant impact of an outlet diameter on the collection efficiency. Results and conclusions presented in this paper can be practically used for design optimization of cyclone separators, and also to select their operating parameters.

The goal of this paper is to point out the types of spatial changes that the small towns located in Krakow's range of influence are currently undergoing, as well as what are the consequences of the various types of changes in these towns. The author asks the question whether the current changes seen in small towns that are under the influence of Krakow can be described as sustainable development – at the basis of which is the increasing of the quality of the functional and spatial structure of a town while preserving its qualities and character – or, on the contrary, that it is more appropriate to describe the changes in the spatial structure of towns as an expansion, which is related only to an increase in their surface area or an increase in the density of their built environment? An attempt has also been made to determine the cause of these changes. An analysis of a set of towns in terms of their accessibility in relation to Krakow, as well as the demographic changes in towns in recent years, has been carried out. This research was useful in determining the dynamic of urban changes or their stagnation. Afterwards, groups of towns with varying degrees of transformation (towns that have been intensively transformed, towns with a balanced degree of spatial changes and towns which remain on the side-lines) were established. In addition, various forms of changes were defined – ranging from cities which register an increase in attractiveness and the changes that it brings while preserving their qualities in accordance with the principles of sustainable development, to settlements which are losing their small-town character as a result of intensive change, at the same time undergoing unification both in terms of space and form of use. From among the groups of towns, example which most fully illustrate the varying degrees and character of the changes of small towns in the area of Krakow has been selected. Based on the research that has been conducted, we can state that small towns in the vicinity of Krakow are undergoing intensive changes and are an attractive alternative in terms of serving as a place of residence, for instance in comparison to the suburban zone of Krakow. However, it is necessary to channel the changes in small towns in a manner that would take advantage of the opportunities for spatial, social and economic development on the one hand, while at the same time causing the intensive changes in those areas to not lead to the loss of their uniqueness, identity and small-town character, as well as the qualities of both a given town and its surroundings on the other. The research that had been performed and the conclusions that were drawn from it can serve as comparative material for other types of small towns and for metropolitan areas.

Rising pollution levels and the amount of generated municipal waste places new challenges before modern cities. These are challenges of a technological, economic, social, as well as a spatial and architectural character. These challenges, when architectural matters are concerned, are often strictly associated with technological conditions. New solutions in the field of technological installations can constitute limitations in design terms, or quite the contrary - they can be treated as guidelines in the case of the creation of a new form. The goal of this article is to provide an answer to two questions: In what manner (in the case of thermal municipal waste processing plants) is the shape of a structure determined by technological solutions? In addition, in what scope does the effect of mutual architectural and technological dependencies in the form of a building affect the immediate surroundings of such plants and - on a wider scale - the space of a city. A significant element of this article is also an attempt at determining whether currently designed new thermal municipal waste processing plants are being located in a manner that gives them the capacity to also play a considerable role in the crystallisation of the structure of a city or of suburban areas, including metropolitan ones. One country that has been faced with the challenge of building new thermal waste processing plants is Italy, due to the considerable problem of managing municipal waste and the associated environmental and social problems. The research performed by the author included an analysis of a selection of thermal waste processing plants located in Italy. Afterwards, as a part of a case study analysis, those structures that stood out against the analysed set either due to distinct architectural features or a higher capacity for spatial impact were presented. The case study presented by the author formed the basis for a discussion about the subject of architectural form and the significance of pro-environmental structures with a hybrid form of use within space. The conclusions drawn from the study can also be useful as models of implementing pro-environmental solutions in other countries that are currently facing an unsolved problem of stockpiling municipal waste.

While searching for the answer to the manner of addressing the problem of waste that is produced in cities, we are on the one hand faced with the necessity of solving it in a fast and effective way, while on the other with searching for effective plans of long-term solutions in this regard. Any prospective answer to the question about the management of municipal waste most often applies not to the processing of waste itself, but efforts being made so that the amount of waste that cannot be subjected to so-called recycling will be as low as possible. The term "cradle to cradle", which is a current where a used product becomes a material for the production of a new one, is one of the main ideas which are at the helm of modern, pro-environmental visions of broadly understood resource management. However, pro-environmental, futuristic ideas regarding waste management are faced with the necessity of being confronted with the current state. One of the most effective means that provide an answer to actual, modern needs is the construction of thermal waste processing plants. The goal of this article is to determine the answer to the question whether - and if so, then in what manner - a visionary approach in terms of environmentally friendly cities has any effect on modern efforts and the solving of problems associated with waste management in cities. Do modern efforts regarding the actual protection of the environment follow far-reaching visions, or are they only an immediate answer to urgent problems? Examples of built projects of thermal waste processing plants, which were built not as a part of far-reaching plans, but as the result of taking quick and urgent "here and now" action due to threats to human life and a high degree of pollution in a city, have been analysed in the article. The analyses that have been carried out will make it possible to formulate conclusions which will be able to serve as reference material during research on both theoretical models of pro-environmental cities and on modern efforts regarding municipal waste management.

Spatial significance of new municipal engineering structures – the case of Italian eco-incineration plants

The increasing awareness of the protection of depleting natural resources results in new challenges for us to face. The necessity to treat domestic water is one of such basic challenges. The intensive development of modern technological solutions in this field creates new possibilities - including those related to the architectural shaping of structures. Simultaneously - following the example of other municipal infrastructure buildings - thanks to the development of technology - sewage treatment plants become structures that are more accessible and spatially attractive. The goal of this article is to answer the question whether these types of urban engineering elements can constitute a structure that is spatially attractive in terms of the tissue of urban and suburban areas, and if so, then under what conditions? The study was performed using a method of analysing a selection of structures in Poland (the first part of the article), in addition to an analysis of examples of good practice regarding such projects in other countries, which constitute state of the art aesthetic solutions in this regard (the second part of the article). The result of the study will allow finding the answer to the question: what is it that causes some sewage treatment plants to have the opportunity to become a significant spatial element, while others only fulfil their technological functions? The results of the analyses performed by the author could form the basis for performing comparative studies of this scope on other examples, including both sewage treatment plants, as well as other municipal infrastructure buildings of a city.