Real Exploitation Conditions Research Articles

EVALUATION OF THE INDICES OF ENERGY RECUPERATION PART BY THE TROLLEYBUSES IN URBAN CONDITIONS

An investigation of a power consumption by the electric buses, trolleybuses is especially actual nowadays, in the time when an economous using of energy resources is necessary. Finding the power consumption during the tests or separate researches gives only a general image about the indices, but in real conditions of exploitation of the electric drive vehicles, when there is a row of external factors, such as movement conditions, driver’s qualification, movement intensity etc., a value of power consumption can vary a lot, an indice of quantity of the recuperated electric power by a vehicle is especially sensitive to different factors. Buying the new modern movable units by the Urkainian trolleybus parks gives a possibility to make the volume researches of power consumption not only by separate trolleybuses, but also on separate routes and to determine this indice for a trolleybus park in general.
 The analysis of literary sources shows that there is no determination of the fate of the recovered energy during the movement of the vehicle along the established route. Modern trolleybuses are equipped with direct current meters, which provide information on the amount of recovered energy during the vehicle's operation on the route. This fact was the basis of the conducted research.
 In the given research work there is shown that a meaning of an electrical energy recuperation part by the vehicles with an electric traction unit that are powered from a contact system, are distributed by a normal law. It was established that the parameters of the normal distribution law are individual for each city of Ukraine, as they are significantly affected by traffic conditions. There were determined the confiding bounderies for further evaluation of applying this function in the trolleybuses operating systems.
 Keywords: electric power, power consumption, recuperated energy, distribution law, trolleybus.

Shear behavior of the sand-concrete interface under cyclic thermal cy-cles

Energy piles - foundation elements also used as heat exchangers - are subjected to daily and seasonal heating and cooling cycles, which might result in the modification of thermo-mechanical behavior of the soil-pile interface. In order to evaluate the effect of the pile’s geothermal activation on a sand-concrete interface, at laboratory scale, a series of direct shear tests were performed using a device adapted for thermomechanical loading. The constant normal load (CNL) direct shear tests were carried out for three different thermal loading scenarios, i.e., at a constant temperature of 13°C, and for two different cooling-heating (8-18°C) cycles. The volumetric deformation after 10 thermal cycles is evaluated, and the shear results are compared.
 A lot of studies [1, 2, 3, 4, 5, 6, 7, 8] have been performed to investigate the thermal effects on the shear behavior of soil-structure interface through direct shear tests. However, in previous studies all the thermal cycles were performed before the shearing phase. Hence, the effect of temperature cycles on the sand-concrete interface after the shear strength has already been mobilized (i.e., interface shear test) has not been well investigated so far. In fact, in real exploitation conditions, the thermal loading is usually added after a part of the mechanical loading or deformation occurred at the soil-pile interface, given the fact that the geothermal exploitation starts only once the building is in operation. To better understand the effects of thermal cycles on the shear properties of sand-concrete energy piles interface after a prior shear phase, a series of interface direct shear tests were performed in laboratory: (1) Reference Test (RT), shearing under constant temperature of 13°C (undisturbed soil temperature below 5 m in the Parisian region, France); (2) Cyclic Test 1 (CT-1), displacement controlled shearing under constant temperature (13°C), 10 thermal cycles (8 to 18°C), finally displacement-controlled shearing until the constant volume state was generated; (3) Cyclic Test 2 (CT-2), shearing to 1/2 of the residual shear strength, 10 thermal cycles (8 to 18°C), finally displacement-controlled shearing until the constant volume state was generated (CT-2 test). The monotonic displacement-controlled direct shear tests were conducted under constant normal stresses equal to 50 kPa, 100kPa and 150kPa that correspond to the typical normal effective stresses acting on the soil-pile interface at different depths.
 Figure 1 presents the volumetric strain (εv) during the thermal cycles of CT-1 and CT-2. The sand samples are characterized by a contractive behavior during each heating phase and followed by an expansive behavior at the high temperature of 18°C. The samples continue to expand in the next cooling phase, then they start to contract when the low temperature of 8°C is constant. The volumetric strain changes are attributed to the thermal-induced particle rearrangement during the heating-cooling cycles. After the 10 thermal cycles, the sand samples show an overall contractive response. The thermal cycles induce more vertical strain on the samples of CT-2 than CT-1 (see Figure 1). The possible reason is that shearing to 1/2 residual shear strength develops more unstable particle rearrangement in CT-2 samples than shearing to the residual shear strength in CT-1 samples.
 The peak and residual interface friction angles of CT-1 and CT-2 after the 10 cyclic thermal cycles are compared with RT in Table 1. The peak interface friction angle of CT-1 is 28.9°, 0.6° lower than the one of RT (29.5°). Whereas a higher peak interface friction angle is mobilized in CT-2 (31.7°). CT-1 is characterized with a residual interface friction angle of 27.9°, which is 0.5° lower than the 28.4° of RT. However, the difference of residual interface friction angles between CT-2 (28.5°) and RT (28.4°) is only 0.1°. To conclude, the effect of the 10 cyclic thermal cycles on the sand-concrete interface is quite limited, it slightly decreases the peak as well as residual interface friction angles of CT-1 and increases these of CT-2.

Thermodynamic Analysis and Improvement Potential of Helium Closed Cycle Gas Turbine Power Plant at Four Loads

This paper presents thermodynamic and improvement potential analyses of a helium closed-cycle gas turbine power plant (Oberhausen II) and dominant plant components at four loads. DESIGN LOAD represents optimal operating conditions that cannot be obtained in exploitation but can be used as a guideline for further improvements. In real plant exploitation, the highest plant efficiency is obtained at NOMINAL LOAD (31.27%). Considering all observed components, the regenerator (helium-helium heat exchanger) is the most sensitive to the ambient temperature change. An exact comparison shows that the efficiency decrease of an open-cycle gas turbine power plant during load decrease is approximately two and a half or more times higher in comparison to a closed-cycle gas turbine power plant. Plant improvement potential related to all turbomachines leads to the conclusion that further improvement of the most efficient turbomachine (High Pressure Turbine—HPT) will increase whole plant efficiency more than improvement of any other turbomachine. An increase in the HPT isentropic efficiency of 1% will result in an average increase in whole plant efficiency of more than 0.35% at all loads during plant exploitation. In the final part of this research, it is investigated whether the additional heater involvement in the plant operation results in a satisfactory increase in power plant efficiency. It is concluded that in real exploitation conditions (by assuming a reasonable helium pressure drop of 5% in the additional heater), an additional heating process cannot be an improvement possibility for the Oberhausen II power plant.

Termodinamička analiza i usporedba dviju propulzijskih parnih turbina

This paper presents thermodynamic (energy and exergy) analysis and comparison of two different marine propulsion steam turbines based on their operating parameters from exploitation. The first turbine did not possess steam reheating and had only two cylinders (high-pressure and low-pressure cylinders), while the second turbine possesses steam reheating and has one additional cylinder (intermediate-pressure cylinder). In the literature at the moment, there cannot be found a direct and exact comparison of these two marine steam turbines and their cylinders based on real exploitation conditions. Along with energy and exergy analyses, the research it is investigated the sensitivity of exergy parameters to the ambient temperature change for both turbines and each cylinder. It is also presented the influence of the steam reheating process on the energy and exergy efficiency of the entire power plant. For both observed turbines and their cylinders it is valid that relative losses and efficiencies (both energy and exergy) are reverse proportional. The operation of an intermediate pressure cylinder from a steam turbine with reheating is the closest to optimal. Due to the different origins of losses considered in energy and exergy analyses, each analysis detects different turbine cylinders as the most problematic ones. The steam reheating process decreases losses and increases efficiencies (both energy of each turbine cylinder and the whole turbine. The whole turbine with reheating has an energy efficiency equal to 81.46% and an exergy efficiency equal to 86.48%, while the whole turbine without reheating has energy and exergy efficiencies equal to 76.47% and 80.94%, respectively. Exergy parameters of a steam turbine without reheating as well as its cylinders are much more influenced by the ambient temperature change in comparison to the steam turbine with reheating and its cylinders. The steam reheating process will increase the efficiency of the whole power plant in real exploitation conditions between 10% and 12%.

Analysis of the Dynamic Response as a Basis for the Efficient Protection of Large Structure Health Using Controllable Frequency-Controlled Drives

Continuous earthmoving machines, such as bucket-wheel excavators (BWEs), are the largest mobile terrestrial machines exposed to the working loads of a periodic character. This paper aims to launch a new idea regarding the preservation of the load-carrying structures of these machines by the means of implementing a controllable frequency-controlled drive of the excavating device. Successful implementation of this idea requires a detailed analysis of the dynamic response of the load-carrying structure in order to determine the domains of frequency of revolutions of the bucket-wheel-drive electromotor (FREM) where the dynamic response of the structure is favorable. The main goal of the presented research was the development of a unique three-step method for the identification of the FREM ranges, where the vibroactivity of the load-carrying structure is within the allowed boundaries. A methodologically original study of the dynamic response was conducted on a unique dynamic model of the BWE slewing superstructure that allows for continuous variation of the FREM, i.e., of the frequency of excitation caused by the forces resisting the excavation. Validation of the spatial reduced dynamic model of the slewing superstructure and the corresponding mathematical model, as well as the overall approach to the determination of the dynamic response, were performed by the means of vibrodiagnostics under the real exploitation conditions. Application of the developed method has yielded: (1) the resonant-free FREM domains; (2) the FREM domains, where the structure is not exposed to the excessive dynamic impacts; and (3) the frequency ratio ranges defining the resonant areas. Additionally, the results of the research have pointed out that the resonant-free state represents a necessary but insufficient condition for the proper dynamic behavior of the BWE slewing superstructure.

A numerical assessment of a latent heat storage system for district heating substations

This work deals with the development and sizing of a latent heat storage system for an urban district heating system (UDHS). The investigated system is a cylindrical tank containing spherical phase change material (PCM) capsules. A physical model based on the apparent specific capacity method was adopted and validated to describe the phase transition within the capsules. The effects of various designs and operating factors on storage performance are detailed and addressed, including the thermal energy provided by the system during the discharge period, the melting temperature, tank volume, and water return temperature. The results show that the energy efficiency of such a device can be enhanced only through a judicious choice of the mentioned parameters. For example, it was found that increasing the UDHN thermal power demand influences the system's performance and leads to reduce the discharging duration. Based on the presented analyses, it can be concluded that the proposed numerical tool can be used by thermal designers of urban heating networks to size, optimise, and predict the actual dynamic behaviour of the storage system under real exploitation conditions.

Low-cost numerical lumped modelling of lithium-ion battery pack with phase change material and liquid cooling thermal management system

This study is aimed at developing a low cost lumped model for simulating a Li-ion battery pack with thermal management systems (TMS) under continuous charging/discharging cycles. The considered system is composed of twenty-four commercial Li-ion batteries with phase change material (PCM) and nine aluminium tubes for liquid coolant circulation. A zero-dimensional numerical model is developed based on the transient energy balances and the analogy between heat transfer and electrical transfer using resistances and capacitors. The simulations were carried at 3-C discharging/0.5-C charging rates and obtained results were compared with both three-dimensional computational fluid dynamic (CFD) results and experimental results from the literature. The effect of various system design and operating characteristics such as the cooling method, the coolant temperature and its velocity, the number of coolant pipes and the ambient conditions on the system performance were presented and analysed. Results show that combining both PCM and liquid cooling for battery thermal management leads to reduce the maximal battery temperature by about 38 °C and 4 °C compared to natural convection thermal management mode and to passive PCM thermal management mode, respectively. Increasing the number of cooling pipes improves the performance of the system and its optimal number in this system is up to 9 pipes. The maximal battery cells temperature is reduced from 31 °C to 20 °C as the used liquid coolant inlet temperature is reduced from 25 °C to 10 °C. Finally, the suggested low cost lumped model is a promising tool for simulating, designing and optimising battery pack with thermal management systems under real exploitation conditions.

Research on Construction and Sizing of the Metal Structure of a Winding Installation

The paper focuses on the design of the metal tower for the sinking of Netiș de-ventilating shaft in Râul Mare Retezat hydro-energetic setup. The analytical calculation of sizing and verification of the metal structure is doubled by the graphic simulation with speciality software, in view of obtaining results as close as possible to the real exploitation conditions of the tower. The tower of the de-ventilating shaft is considered to be a temporary construction, and its component parts will be decommissioned once the sinking is finalized. The tower is made up of metal structures in four transoms, 3 being mounted with junction plates and screws, the fourth being the roof.

Analysis of the influence of the ambient temperature on the energy efficiency of solar modules by application of empirical correlations for natural convection

In this paper, the effect of the ambient temperature on photovoltaic (PV) modules for different angles of inclinations and different intensities of the solar radiation on the surface of PV module is considered using empirical correlations for natural convection. The analysis used an analytical model based on the energy balance equilibrium between PV module and the environment. It has been shown that in real conditions of exploitation, the value of the solar conversion coefficient of the solar energy to be determined by the manufacturer, valid for the standard test conditions (STC) for PV module (25 °C -1000 W/m2). The results obtained indicates that in the case a smaller number of PV modules corresponding to the required number for average household. The proposed procedure can be applied in the techno-economic analysis for PV system with uniaxial monitoring of the sun position as well as static PV systems.

MODELING OF DISPLACEMENT PROCESSES IN HETEROGENEOUS ANISOTROPIC GAS RESERVOIRS

Nowadays there are important problems of increasing efficiency of development and exploitation of gas deposits. There are problems associated with the growth of gas production in heterogeneous anisotropic reservoirs, increasing gas recovery, achieving economic efficiency and so on. In this situation, there are popular methods of computer modeling of gas productive reservoirs, because they allow getting information of the structure and characteristics of the gas reservoir, the distribution parameters of permeability and other important factors in it. They also allow evaluating and calculating uncertainty arising from the lack of information about the gas reservoir properties outside the well. Currently there are many methods of computer modeling, allowing solving various practical problems. From another hand there are some problems related to the accuracy and adequacy of simulation of heterogeneous anisotropic permeable collector systems in real conditions of gas deposits exploitation. On the base of combined finite-element-difference method for solving the nonstationary anisotropic piezoconductivity Lebenson problem, with calculating of heterogeneous distribution of permeable characteristics of the gas reservoir, we carried out modeling of filtration processes between production and injection wells. The results of computer modeling show that intensity of the filtration process between production and injection wells depends essentially on their location both in a shifting-isotropic and anisotropic gas reservoir. Therefore, for the effective using of poorly permeable shifting-isotropic gas-bearing reservoirs, it is necessary to place production and injection wells along the main anisotropy axes of the gas-bearing layers. At the placing production and injection well systems in low-permeable anisotropic reservoirs of a gas field, the most effective exchange between them will take place when the direction of increased permeability of the reservoirs coincides with the direction of the location of the wells. Obviously, the best conditions for gas production processes in any practical case can be achieved due to optimal selection of all anisotropic filtration parameters of the gas reservoir. One can use obtained results for practical geophysical works with a purpose optimizing of gas production activity in low-permeable heterogeneous anisotropic reservoirs. Presented method for more detailed investigation of low-permeable heterogeneous anisotropic gas-bearing deposits can be used.

A wayside hotbox system with fuzzy and fault detection algorithms in IIoT environment

Moving towards industrial internet of things (IIoT) concept is one of the hot issues of the management, control, and maintenance of railway transportation. The wayside hotbox systems are useful for monitoring of overheated axle bearings in the harsh dust environment. In the paper, the fuzzy-based fault detection algorithm (FDA) of the spatially distributed hotbox monitoring system (SDHMS) and its IIoT concept are presented. SDHMS consists of three stand-alone wayside hotbox monitoring systems that are installed in three distant locations: two thermal power plants and a coal mine. The system plays an important role in keeping railway safety, preventive maintenance and accident avoidance. Therefore, the IIoT concept is needed for increasing the reliability of coal transportation and the energy efficiency of electricity production. The main advantage of the presented concept is the application of the FDA at the edge and fog levels as well as the application of a complex fuzzy model for decision making at the cloud level. Edge computing involves signal processing in hotbox systems with the aim of the fault detection and quality assessment of the measured signals. Fog computing involves data processing with the aim of detecting an overheated bearing (temperature, position, axle number and train side), and alarming. Cloud computing is in charge of assessing the bearing condition and the need for replacement and maintenance planning. The proposed algorithm and fuzzy model were validated in real conditions of exploitation, successfully.

Non-uniform corrosion of steel rebar and its influence on reinforced concrete elements` reliability

Abstract Remarkable place of reinforced concrete structures in construction field has been noted in wide number of recent researches. Subsequently, their degradation due to aggressive environment has become the topical problem nowadays. Therefore, the formulation of reliable technique for corroded element strength decrement is of great importance, and could be achieved only with the use of complex experimental and theoretical analysis. In this article an attempt is made to propose the mathematical approach to corrosive process modelling, taking into consideration the specifics of its development. According to thorough literature review on existing studies, main specifics of the process were indicated for further suppositions and assumptions formulation. Accordingly, the complex theoretical investigation with corresponding mathematical computations was conducted and results of analytical modelling were discussed. As the initial data for analytical modelling results of previously conducted experiments were used. Analysis of the obtained results shows rather high correspondence with the real conditions of structural element exploitation, taking into consideration material anisotropy and complexity of the corroded zone spread along the rebar cross-section. Proposed methodology for limit force decrease evaluation in general demonstrates reliable results and could be used for further evaluation of corrosion impacts on reinforced concrete elements bearing capacity.

Energy and Exergy Evaluation of a Two-Stage Axial Vapour Compressor on the LNG Carrier.

Data from a two-stage axial vapor cryogenic compressor on the dual-fuel diesel–electric (DFDE) liquefied natural gas (LNG) carrier were measured and analyzed to investigate compressor energy and exergy efficiency in real exploitation conditions. The running parameters of the two-stage compressor were collected while changing the main propeller shafts rpm. As the compressor supply of vaporized gas to the main engines increases, so does the load and rpm in propulsion electric motors, and vice versa. The results show that when the main engine load varied from 46 to 56 rpm at main propulsion shafts increased mass flow rate of vaporized LNG at a two-stage compressor has an influence on compressor performance. Compressor average energy efficiency is around 50%, while the exergy efficiency of the compressor is significantly lower in all measured ranges and on average is around 34%. The change in the ambient temperature from 0 to 50 °C also influences the compressor’s exergy efficiency. Higher exergy efficiency is achieved at lower ambient temperatures. As temperature increases, overall compressor exergy efficiency decreases by about 7% on average over the whole analyzed range. The proposed new concept of energy-saving and increasing the compressor efficiency based on pre-cooling of the compressor second stage is also analyzed. The temperature at the second stage was varied in the range from 0 to −50 °C, which results in power savings up to 26 kW for optimal running regimes.

Fault detection using FRA in order to improve the aging model of power transformer

Power transformers are constantly exposed to mechanical, thermal and electrical stresses during operation. In this paper, the authors propose an improved aging model of power transformers by adding the impact of mechanical deteriorations. In the current practice, the mechanical deformation and dislocation of the windings and core are not sufficiently distinguished as components that influence the aging of the transformer. Hence, the current aging model was expanded with a functional block that contains several typical failures in order to emphasize their impact on the lifetime of transformers and their aging as well. The authors used the Frequency Response Analysis (FRA) method for the fault detection and location of the mechanical deformations of its active parts. The correlation function is used to determine the level of the detected failure. All presented test results are obtained in real exploitation conditions.

The Low Duty Centrifugal Compressor Control System and its Impact on the Surge Pressure

This paper presents an analysis of the low duty compressor for marine steam generators and its running conditions. The analysed low duty compressor was observed under three different running zones caused by a throttled flow towards main steam generators. All examples were explained according to real exploitation conditions. As the low duty compressor has the highest influence on the flame stability for the main steam generators while running, it is very important to observe the constant flow towards the main steam generators. Possible flow fluctuation implies instabilities which are explained in the article and the same have to be avoided in order to assure a reliable life span of the low duty compressor and smooth operation of the main steam generators. Furthermore, for preventing efficiency losses of a steam power plant, some methods for avoiding surge effects are emphasized and recommended.

NETWORK ANALYSIS OF COLLABОRATIVE DECISION MAKING BY AIR NAVIGATION SYSTEM'S HUMAN-OPERATORS DURING EMERGENCY CASES IN FLIGHT

Мета: дослідження консолідованого прийняття рішень пілотом та авіадиспетчером у разі виникнення особливого випадку в польоті (на прикладі відмови одного двигуна та пожежі іншого з однієї сторони під час зльоту на багатомоторному повітряному кораблі) для максимальної синхронізації технологічних процедур операторів. Методи: детерміновані моделі спільного прийняття рішень операторами аеронавігаційної системи отримані методами мережевого планування, їх адекватність підтверджена натурним моделюванням на комплексному авіаційному тренажері. Ймовірність розвитку особливого випадку в польоті оцінені за допомогою нейромережевої моделі. Для послідовної оптимізації консолідованої двоканальної мережі «пілот-авіадиспетчер» з метою досягнення наскрізної ефективності спільних рішень використаний мультикритеріальній підхід: досягнення мінімального часу на парирування особливого випадку в польоті при максимальній безпеці/максимальному узгодженні за часом дій операторів. Результати: синхронізовані операційні процедури операторів аеронавігаційної системи в особливих випадках в польоті з оптимальною послідовністю дій і мінімальним часом завершення польоту. Розроблена концептуальна модель системи для управління та прогнозування розвитку особливих випадків в польоті на основі детермінованих та стохастичних моделей прийняття рішень людиною-оператором аеронавігаційної системи,враховуючи вплив факторів професійного та непрофесійного характеру. Обговорення: запропоновані моделі доповнять базу даних розвитку сценаріїв польотних ситуацій в системі підтримки прийняття рішень і можуть бути використані в процесі спільної тренажерної підготовки операторів аеронавігаційної системи і в реальних умовах експлуатації повітряного корабля

Effectivenes of Strengthening Loaded RC Beams with FRCM System

AbstractThe composite materials as FRP (Fiber Reinforced Polymers), which are characterized by benefits resulting from the combination of high strength reinforcement (as carbon, glass, steel or aramid fibers) with synthetic matrix are increasingly used to reinforce existing structures. Reinforcing System as FRCM (Fibre Reinforced Cementitious Matrix), which includes, among others, Ruredil X Mesh Gold System, is much less commonly used. However, the uniform and practical methods for calculating composite reinforced structures are not determined. Especially when considering the real conditions of structure exploitation, which requires further research in this field. In the paper the initial loading level influence on the efficiency of reinforced concrete beams strengthen using system Ruredil X Mesh Gold was investigated.

The analysis of an influence of rubber V-belt physical properties on CVT efficiency

This work deals with the analysis of the CVT efficiency for three different rubber V-belts. The bench tests have been conducted on the complete light two-wheeled vehicle drive system so the experiments refer to real exploitation conditions. The research has been performed for fixed gear ratios. The overall efficiency and belt slip have been specified. The longitudinal belt velocity has been measured by the contactless measurement head. The basic belts physical properties have been estimated and significant dissimilarities of their construction details, used materials and stiffness parameters have been revealed. The explicit differences of overall efficiency and belt slip have been observed between tested belts. The V-belt features limiting specified type of losses contributes to increasing other losses at the same time. Furthermore the gear ratio essential influence on the belt slip has been noticeable. The amount of slip value indicates that this is significant part of the total power losses as it has been described by Bertini. However it clashes with the Chen research, where the slip corresponds with the marginal part of the overall losses.

Creep of concrete caused by freeze and thaw cycle

To the best knowledge available today, the creep of concrete is understood as slow plastic deformation caused by continuous external factors. Changes occurring in the structure of concrete are however not discussed. Creep as a phenomenon is typically perceived “in purity”, in an invariable and favorable environment. Evolution of creep deformations thus has a fading character and usually goes along with consolidation of concrete. It is only under loads near the threshold of concrete’s long-term strength that micro-destructions tend to grow during the first phase following application of the load. Creep phenomenon is researched «in pure form», i.e. in constant favorable external conditions. Developing of creep deformations has fading character and accompanied by seal of concrete. In real exploitation conditions of constructions appears changes in temperature and humidity, influencing on development of creep deformation. Alternate freezing and thawing of concrete, which most affects durability, causes in unloaded concrete significant extension deformations. Deformation development under the joint action of loads and alternate freezing and thawingalmost was not researched. In the article presented results of concrete deformation research, differing by frost resistance, under loads in the range from 0.2 to 0.7 of prismatic strength. Obtained results allows reasonable take stress value in consideration with expected deformations in the process of operation.

Analysis of Influence of Types of Rocks Forming the Goaf with Caving on the Physical Parameters of Air Stream Flowing Through These Gob and Adjacent Headings

In the paper there are presented results of influence of types of rocks forming the goaf with caving on the physical parameters of air stream flowing through these goaf and adjacent headings. It was assumed. that goaf with caving are porous medium. which permeability and porosity depends on the distance from the front longwall and from stratification resistance of rocks forming the heap. On the base of stand tests values of stratification resistance of rock littering at the roof of tested longwalls were determined. The main aim of the tests was to determine an impact of type of rock littering in mined seam on values and distribution of velocity and pressure of air stream in the gobs This aim was realized by a determination of value of stratification resistance of roof rocks on the tested parameters of air stream flowing through these gob. Analysis was performed in the ANSYS Fluent software. Modeling studies were performed for real exploitation longwall and additionally for two types of roof created with the most often presented rocks. For each of these systems distributions of velocities and static pressure along assumed measurement lines were determined. Analysis included determination of physical parameters of the air stream flowing through the gob for real exploitation conditions of this longwall and additionally for assumed two (the most often presented in reality) variants of rock presented in the roof of mining longwall. Developed research methodology and obtained results should be use during selection of ventilation parameters and preventive actions connected with reduce methane and fire hazard in underground mining. DOI: http://dx.doi.org/10.5755/j01.mech.24.1.20214