Required Air Flow Research Articles

The HVAC system engineering method for a new family of unified cabins of combine harvesters

BACKGROUND: Designing a combine harvester cabin climate system is a complex and multi-stage process that includes solving a set of tasks. To solve them, a design engineer must have knowledge and skills in various fields, starting with thermal engineering calculations and ending with experimental research methods and computer modeling, which requires a large amount of intellectual and time resources. Therefore, the task of creating a unified method of engineering of combine harvester cabin HVAC system is highly relevant. AIM: Development of the HVAC system for a unified cabin of a grain harvester and a forage harvester. The designed HVAC system is purposed to create a comfortable microclimate in the cabin of the combine for 2 people in summer and winter operating conditions. METHODS: The methodology of calculation and selection of the combine harvester cabin HVAC system, which includes the development of engineering calculation methods and mathematical modeling of thermodynamic and ventilation processes in the cabin, is considered. RESULTS: The main parameters were determined: heat intakes and heat losses for the grain harvester and forage harvester cabins, which amounted to 2.8 and 2.2 kW for the grain harvester, 2.9 and 2.35 kW for the forage harvester; the required air flow rate supplied to the cabin to ensure a comfortable temperature — 740 m3/h; the percentage of air recirculation regarding the conditions of absence of fogging and creation of excessive pressure in the cabin — 75%; the cooling and heating capacity of the HVAC system, taking into account the operating conditions of the combine, are 7.8 and 6.3 kW respectively. The selection of the main equipment of the HVAC system for a unified cabin for a new family of unified cabins of combines — the BUHLER 1000 MFWD evaporator-heater and the Valeo TM16 compressor are chosen. CONCLUSION: The HVAC system designed in accordance with the presented methodology is capable of ensuring a comfortable cabin air temperature in the range of 22–24 °C at various operating modes of the combine harvester in different regions. In addition, the HVAC system parameters eliminate fogging of the cabin windows and the penetration of dusty air inside due to the created excessive pressure.

Optimization of Steam Boiler Airflow Control System in a Typical Oil Refinery Power Plant

This paper presents optimization of Steam Boiler Airflow Control System in a Typical Oil Refinery Power Plant. The power plant is equipped with four steam boilers using a damper-louvers airflow control system. Analysis has revealed significant energy wastage due to inefficiency and over-air supply, with the system requiring 59,904,436 kWh annually at a financial cost of N1, 093,255,884. The existing system's inefficiency results in an annual electrical energy waste of 8,502,302 kWh. This inefficiency is attributed to the Force Draft Fan (FDF) motor operating at maximum speed continuously, regardless of the steam profile or airflow requirements. This study aimed at optimizing the steam boiler airflow control system in a typical oil refinery power plant for improved power efficiency, energy conservation, and cost savings citing Port Harcourt Refinery Company (PHRC) at Alesa-Eleme, Rivers State, Nigeria. To address this, the damper-louvers system was replaced with a Variable Frequency Drive (VFD), which would adjust the motor speed to match the required airflow, thereby reducing energy wastage. The process was simulated and VFD/FDF motor analyzed in MATLAB Simulink, determining the optimal speed, airflow, and power requirements. Results obtained show that the VFD control system improves the FDF motor's power efficiency from 47.7% to 85%, with an annual energy saving of 8,502,302 kWh (8.5 GWh). This results in a total cost benefit of N478.18 million annually, representing a 43.8% cost saving. The implementation cost of the VFD infrastructure was estimated at N111, 440,000, with a payback period of approximately eleven months. The findings suggest deployment of higher FDF motor speed ratings to enhance speed control and energy efficiency in Oil refinery power plant.

Exploring the benefits of hydrogen-water injection technology in internal combustion engines: A rigorous experimental study

Previous hydrogen researchers have demonstrated the great potential of hydrogen as a zero-carbon fuel and its wider operational ability to directly replace the existing fossil-fuelled internal combustion engines (ICE). Hydrogen direct-injection technology can operate at stoichiometric combustion conditions, fully eliminating the intake backfire phenomena, which has the benefit of low airflow requirements and is a suitable solution for naturally aspirated ICE platforms. However, significant challenges must be addressed when operating an H2 ICE at or near stoichiometric. These include rapid pressure rise rate, high in-cylinder gas pressure and temperature and the consequential higher engine-out NOx emissions. This study provides a comprehensive experimental analysis of the effect of water injection on a light-duty H2 engine’s performance, efficiency, burn durations and NOx emission. The engine was modified to operate with hydrogen via a centrally-mounted direct H2 injector and an intake port-mounted water injection system. The study included water vapour measurements, NOx concentrations and other exhaust gases. The practical implications of these findings are significant. The results demonstrated that the NOx emissions were reduced by 79% when the water was injected at a rate of 5 kg/h at 10 bar IMEP and 2000 rpm. This reduction in emissions, coupled with the observed decrease in cylinder pressure and the rate of pressure rise, could substantially improve engine performance and efficiency. At higher load regions, the water injection extended the maximum engine load to 24 bar IMEP and increased the engine torque output by 10%. The maximum Indicated Thermal Efficiency (ITE) increased from 41% at 16.5 bar IMEP to 42.5% at 18 bar IMEP at a lower lambda, with a corresponding reduction in the intake-air-boost pressure requirement. Of particular note, the use of water injection decreased the engine-out NOx emissions under high-load conditions by more than 55%, even at richer AFR compared to pure hydrogen operation.

Multiscale multiphysics modeling of ammonia-fueled solid oxide fuel cell: Effects of temperature and pre-cracking on reliability and performance of stack and system

Ammonia is a promising carbon-free fuel for solid oxide fuel cells (SOFCs). However, direct feeding of ammonia into the SOFC may lead to serious degradation due to the nitriding. Conversely, the pre-cracking of ammonia introduces complexity to the system design and causes increased power losses in the system. Therefore, it is crucial to explore all these aspects simultaneously. In this context, this study introduces a novel multiscale modeling approach by integrating a 3D multiphysics simulation of the ammonia-fueled SOFC stack with system-level modeling to investigate the reliability and performance of the stack and system. Two different cell technologies developed for low temperature (LT) and high temperature (HT) operation are investigated at LT (600 – 700°C) and HT (700 – 800°C) ranges. The results indicate that fuel inlet temperature should be 55°C and 18°C higher than the minimum temperature in 0% pre-cracking case for HT and LT cases, respectively. The increase in the required air flow rate for cooling in the 100% pre-cracking case compared to the 0% pre-cracking case is around 100% and 216% for the HT and LT cases, respectively. However, stack power production and power losses in the system components are comparable for LT and HT cases which leads to similar system performance. A larger share of the active area is affected by nitriding in LT cases than HT ones. However, a smaller cracking ratio at LT (∼ 82%) compared to HT conditions (∼ 92%) is needed for elimination of nitriding. While the LT and HT cases are comparable in terms of system power production, the lower stack outlet temperatures in LT cases require novel and more expensive catalysts for ammonia pre-cracking and HT cases need more expensive steels.

Navigating the Challenges: Construction Lessons in Establishing an Orthopedic Institute in a Sterile Environment

Background: In order to become a new, state-of-the-art orthopedic institute with additional operating rooms, and a brand new sterile processing department (SPD), construction needed to be done within a sterile environment. Expansion of the operating room (OR) included adding a whole new wing, with smaller construction work within the open and active OR. While construction for a new SPD occurred in the midst of an active and open SPD; unlike the addition of the OR, new SPD construction included heavy demolition and multiple dust generating projects. There were many lessons learned from the built of this brand new institute, which took place in the middle of a pandemic era. Method: Each project involved in the making of the new orthopedic institute required an Infection Control Risk Assessment (ICRA), as well as walkthroughs and team meetings prior to the start of work. Team meetings involved the hospital Infection Preventionist (IP), the construction project manager, and the departments [involved] managers. Requirements, to mitigate dust dispersal into the neighboring sterile environment, were listed in the ICRA. In addition, weekly rounding was conducted by the team to ensure air flow requirements were followed, and there were no accumulation of dust dispersing to the sterile side. Reprocessing was also conducted at sister facilities when existing reprocessing items (sterilizers, instrument washers, cart washers, etc) were shut down; the hospital also went on bypass a few times in order to accommodate patients who emergently needed operating services. Result: By April 2022, after two years of construction, the new orthopedic institute with 12 new operating rooms, new ambulatory surgery units (ASU), new post anesthesia care units (PACU), and a brand new SPD went live. There were more than 100 shutdown notices, over 50 alternative practices in place to continue daily operations while also allowing construction work to continue. Noncompliance to any of the requirements was immediately followed up with an urgent notice to the project manager. Conclusion: Hindsight, heavy construction in a sterile environment is not preferred and it would have been easier to add on a new SPD, similar to how the OR additions were added; instead of building within an actively open sterile environment. Multidisciplinary team meetings conducted at the very beginning of the project would have prevented many shut downs and alternate practices; . It is pertinent that IPs and clinical department managers are involved at the most earliest phases of the construction.

New Afton Mine diesel and battery electric load-haul-dump vehicle field test: Heat and dust contribution study

ABSTRACT The New Afton Mine and CanmetMINING conducted a joint study to better understand the environmental and performance impacts of battery- and diesel-powered mobile equipment. The two main objectives were to: (1) determine if battery electric and diesel load-haul-dump vehicles (LHDs) could perform equivalent duties, and (2) gather environmental information for determining the ventilation airflow requirements for battery-powered vehicles. The study focused on the effects of the LHDs on heat and dust generation and energy consumption in a ramp and in a production level. For the production environment tested, respirable crystalline silica concentrations were the driver to assess the battery-powered LHD airflow volume. The potential to reduce this volume was identified in the controlled air streams and conditions tested. However, it depended on the scenario and the dust generation and suppression mechanisms. One scenario evaluated environmental conditions under a reduced airflow (50% less than the diesel LHD). For this mine site, area contaminants levels exceeded limits; therefore, the potential for savings was less than 50%. For the scenarios tested, the battery electric and diesel LHDs were able to move equivalent amounts of material in a similar time.

Occupancy sensor-enabled demand control ventilation using virtual outdoor air flow meters in air handling units without an outdoor air flow meter

Nowadays, the outdoor air (OA) flow requirement for demand control ventilation (DCV) can be accurately determined using occupancy sensors in commercial buildings. However, in air handling units (AHUs) without precise OA flow measurements, the OA is often controlled by a fixed-damper position method, which cannot maintain the required OA flow rate. The objective of this study is to develop and evaluate occupancy sensor-enabled DCV OA control using a virtual OA flow meter in AHUs. Firstly, a virtual OA flow meter is derived from a virtual supply fan flow meter by applying the correlation between the OA ratio and damper position under appropriate building pressure control. Subsequently, experiments are conducted to calibrate the virtual OA flow meter in an AHU with the design OA flow rate of 120 L/s. Finally, occupancy sensor-enabled DCV OA control is implemented by using the calibrated virtual OA flow meter. The evaluation results show that the proposed DCV OA control can match the actual OA flow rate well with the required OA flow rate. The root mean squared error (RMSE) falls within the range of 16–20 L/s, demonstrating an improvement over the fixed-damper position control, which yields an RMSE of 36 L/s.

Determining airflow requirements in mine workings based on field measurements of actual emissions from internal combustion engine equipment

The increasing complex geological and hydrogeological conditions ore deposit mining, deeper excavation sites, and ambitious business expansion strategies, necessitate the use of high-performance, heavy-duty self-propelled machinery and winning equipment. Such activities significantly strain mine ventilation systems and demand innovative safety measures during mining.This study assesses the influence of interconnected production variables on the aerological safety of mining operations. It provides real-world data on emissions from diverse sources within mines. The analysis includes an examination of current methodologies for estimating the air volume needed to dilute exhaust gases from diesel-powered machinery. Through numerical simulation that accounts for changes over time, the study was able to predict how exhaust gas concentrations would disperse within mines. These theoretical findings were then confirmed through empirical observations made in actual mining setting The field studies conducted, alongside their thorough analysis, underscored the necessity for adopting new, more sophisticated approaches to calculate airflow requirements in mines operating ICE machinery. A particular methodology developed by the MMI of the NUST MISIS (hereinafter referred to as the Methodology) was put forward as the primary tool for this purpose. The Methodology’s precision and benefits were closely scrutinized, revealing its effectiveness in ensuring aerological safety in mines.

Design and Computational Fluid Dynamics Analysis of a Fume Extraction System for a Welding Company in Guyana

The arc welding operation results in harmful fumes being emitted where welders are exposed to dangerous metallic gases and fumes for 6 to 8 hours daily at INFAB welding company in Guyana. This paper presents a design of a fume extraction system, the design incorporates workspace dimensions, volume calculations, duct materials required, framework materials, airflow requirements, and fan selection, guided by a target of 6 air changes per hour (ACH). In addition, the calculated required airflow rate of 58,500 ft³/h ensures the selection of appropriate fans. The design aims to create a safe and healthy welding area for the employees by removing harmful fumes. Computational fluid dynamics (CFD) simulations were employed to analyse velocity and pressure distribution, offering valuable insights into airflow patterns and pressure variations.

Effects of verbal tasks with varying difficulty on real-time respiratory airflow during speech generation in healthy young adults.

Respiratory function is linked to sensory, affective, and cognitive processes and it is affected by environmental constraints such as cognitive demands. It is suggested that specific cognitive processes, such as working memory or executive functioning, may impact breathing. In turn, various lines of research have suggested a link between peak expiratory airflow (PEF) and cognitive function. However, there is scarce experimental support to the above assertions, especially regarding spoken language. Therefore, the present investigation aims to evaluate whether breathing varies as a function of performing verbal naming tasks with different difficulty levels. Thirty healthy young adults, (age M = 25.37 years), participated in the study. Participants were required to perform aloud five verbal tasks ranged in order of difficulty: Reading single words, reading a text passage, object naming, semantic and phonemic fluency. A pneumotachograph mask was employed to acquire simultaneously the verbal responses, and three airflow parameters: Duration, peak, and volume at both stages of the respiratory cycle (i.e., inspiration/expiration). Data were analyzed with one-way repeated measures MANOVA. No significant differences were found between reading single words and object naming. In comparison, distinctive airflow requirements were found for reading a text passage, which were proportionally related to number of pronounced words. Though, the main finding of the study concerns the data on verbal fluency tasks, which not only entailed higher inhaled airflow resources but also a significant PEF. Our data demonstrated that the most difficult tasks, namely semantic and phonemic verbal fluencies, relying on semantic search, executive function, and fast lexical retrieval of words were those requiring important amount of inhaled airflow and displaying a high peak expiratory airflow. The present findings demonstrated for the first time a direct association between complex verbal tasks and PEF. Inconclusive data related to object naming and reading single words are discussed in light of the methodological challenges inherent to the assessment of speech breathing and cognition in this line of investigation.

Soundproofing Autonomous Vehicle Computers for Passenger Comfort

The computing superstructure necessary for self-driving cars to function presents a unique acoustics problem - the fans produce significant amounts of noise within the cabin that is uncomfortable for passengers. To ensure consumer comfort and promote more widespread adoption of the technology, soundproofing is required. Any soundproofing solution must not compromise the ability of the self-driving computer to function, meaning that air flow must be preserved. To this end, the UTA Senior Design team creates testing procedures to identify the sound profile of May Mobility's Toyota Sienna. After identifying the frequency range and intensity of the fan noise within the cabin, the team can narrow down potential soundproofing solutions. Given the noise frequency range and air flow requirements, three materials that show promise are identified. The team's testing of varying configurations of cork, open-cell charcoal foam, and closed-cell neoprene foam to determine the most effective solution resulted in the identification of charcoal foam as the optimal material. Soundproofing structures were strategically placed around the computing superstructure and achieved a noticeable reduction of noise within the cabin.

A manikin-based assessment of loose-fitting powered air-purifying respirator performance at variable flow rates and work rates

Loose-fitting powered air-purifying respirators (PAPRs) are used in healthcare settings, although barriers to routine, everyday usage remain, including usability concerns and potential interference with work activities. Loose-fitting PAPRs are approved by the National Institute for Occupational Safety and Health (NIOSH) and must meet minimum performance requirements, including a minimum airflow requirement of 170 L/min. One course of action to address usability concerns is to allow for the use of PAPRs designed with reduced airflow rates. The primary objective of this study was to assess the effect of PAPR flow rate and user work rate on PAPR performance, using a manikin-based assessment method. PAPR performance was quantified using the “Manikin Fit Factor” (mFF), a ratio of the challenge aerosol concentration to the in-facepiece concentration. Flow rates from 50–215 L/min and low, moderate, and high work rates were tested. Two models of NIOSH Approved loose-fitting facepiece PAPRs were tested, both having an Occupational Safety and Health Administration Assigned Protection Factor (APF) or expected level of protection, of 25. A two-way analysis of variance with an effect size model was run for each PAPR model to analyze the effects of work rate and flow rate on PAPR performance. Flow rate and work rate were found to be significant variables impacting PAPR performance. At low and moderate work rates and flow rates below the NIOSH minimum of 170 L/min, mFF was greater than or equal to 250, which is 10 times the OSHA APF of 25 for loose-fitting facepiece PAPRs. At high work rates and flow rates below 170 L/min, mFF was not greater than or equal to 250. These results suggest that some loose-fitting facepiece PAPRs designed with a flow rate lower than the current NIOSH requirement of 170 L/min may provide respirator users with expected protection at low and moderate work rates. However, when used at high work rates, some loose-fitting facepiece PAPRs designed with lower flow rates may not provide the expected level of protection.

Rethinking Classroom Ventilation in post pandemic Situation

This paper aims to contribute in outlining the latest findings and formulating a simple practice in providing sufficient air circulation for classroom activities in preparation for the post-pandemic era. During this pandemic, remote learning over the internet has been a viable solution everywhere, including adopted by education institution to keep serving the learning process. However, as more and more people involved and the time elapses, several disadvantages of e-learning are realized. In addition, education institution should be prepared for the upcoming offline learning activity in post-pandemic era. This paper aims to refine the minimum airflow requirement for the classroom, finetuned based on student activity, ceiling height. Student activity is being the focus rather than teacher because student represents the majority of classroom occupant. In addition, a discussion on how it can be achieved using simpler ventilation system is presented. ON/OFF scheme for the usage of the active ventilation is also elaborated.Keyword: classroom, post-pandemic era, ventilation system, air circulation.

Modeling Solid Oxide Fuel Cells for Hybrid-Electric Turbo Generators in Aircraft Applications

Air travel accounts for a significant portion of domestic and global greenhouse gas emissions. Decarbonized electric propulsion has the potential to be disruptive to replace conventional gas turbine based engines and could be an attractive solution to reduce aircraft emissions. This work aims to design a pressurized hybrid solid oxide fuel cell/gas turbine turbo generator using carbon neutral liquid fuels for narrow body commercial aircraft with high gravimetric power densities. Novel Ni/GDC based cell architectures are used to lower cell operating temperature and thereby, reduce both stack costs (e.g., interconnects and seals) and system balance-of-plant costs. There is currently limited understanding of the operating characteristics and optimum conditions for employing GDC based cells in these applications. Further, the mixed ion electronic conducting (MIEC) nature of GDC and its impact on cell voltage and electrochemical performance has yet to be quantified. This work presents a one-dimensional, down-the-channel stack model that captures physicochemical processes for an intermediate temperature Ni/GDC based fuel cell. The leakage current phenomena of MIEC anodes is captured by calculating open circuit voltage as a function of conductivity, temperature and pressure. Activation overpotentials are calculated based on published results in literature that fit exchange current densities and charge transfer coefficients based on experimental electrochemical impedance spectroscopy measurements [1,2]. Fickian diffusion for mass transport across the porous electrodes and rate mechanisms to evaluate reforming characteristics are used. The model predicts electrochemical performance for varying cell temperatures and flow rates. The distribution of overpotentials with cell temperature and current density is analyzed. Thermal management of power dense stack operating conditions is critical to understand. Thus, the stack model is also employed to within a subsystem where it is integrated with an autothermal reformer and anode gas recycle to parametrically assess operating conditions and performance, particularly towards minimizing cooling air flow requirements. Figure 1

Dynamic alpha factors: Prediction in time and evolution along reactors

The performance of aeration – one of the most costly processes at water resource recovery facilities – is heavily impacted by actual wastewater characteristics which are commonly taken into account using the alpha factor (α). This factor varies depending on hydraulic and organic loading; such variance includes both time and spatial fluctuations. In standard design practice, it is often considered as a fixed number, or at best, a predefined time series. The objective of this paper is to propose a new method of predicting plantwide trends in the α factor through the use of process modelling which can accommodate diurnal and seasonal variations. The authors’ concept takes into account the dependence of α on sludge retention time in the form of degradation kinetics, the effects of organic loading (influent filtered COD), the presence or absence of anoxic zones, diffuser depth, and the impact of high MLSS found in certain, e.g., MBR, technologies. The developed model was calibrated using data from numerous facilities, relying on off-gas measurements and tests in clean and process water. Model validation was carried out against averaged α factor gradient data from one plant, and against diurnal air flow measurements from another. The Benchmark Simulation Model 1 configuration was used to demonstrate the applicability of the proposed model – in estimation of blower energy consumption and peak air flow requirements – comparing it with constant and scheduled α factor-based approaches.

The influence of incubator design features on the incubation result

This article shows the results of chicken eggs incubation by IUP-F-45 and BioStreamer 165HD. There were two different types of machines during two-lots of eggs incubation. The BioStreamer 165HD is equipped with such feature as flexible incubation environment tuning according to its technology of embryo feedback. The sensors control the temperature inside machine by using the temperature of egg shells. Also there are sensors which can monitor the humidity level by controlling and predicting the humidity loss of each egg lot and using the narrow-hatching window technology. The incubators are managed by controller and connected to one computer network. The eggs are set to cellular structure incubation tray. The pulsators are equipped with five wide blades to ensure the required air flow rate. In addition, the roof vents have been improved. The power of the heating elements has been increased, which provides a quick heating time for all eggs at the beginning of the incubation cycle. The larger diameter of the cooling coil creates a wider overall cooling surface. As a result of the research, it was found that the use of the BioStreamer incubator made it possible to increase the hatchability of eggs, to carry out the simultaneous hatching of young brood, reducing the hatching by 5.5 hours, to increase the yield of conditioned young chickens by 0.9% and its quality, to obtain a greater amount of meat products from broilers: the average weight of chickens increased by 2.7 per cent, the safety of brood - by 3.6 per cent.

Design of residential ventilation systems using performance-based evaluation of Indoor Air Quality: application to a Danish study case

A Demand-controlled ventilation (DCV) has been recognized as a promising solution for decreasing energy consumption while ensuring good Indoor Air Quality (IAQ) in buildings. However, its application in the residential sector has increased first recently. Implementation of DCV systems brings the problem related to assessing their performance, not only in the view of energy savings but also in the ability to ensure IAQ. The objectives of this paper were to introduce a multicriteria performance-based approach for the evaluation of residential ventilation systems with CONTAM airflows simulations; illustrate its applicability to three DCV strategies in the context of renovated apartment buildings in Denmark and challenge the minimal background airflow requirements anchored in the Danish building code. Our performance-based approach allows assessing ventilation performance regarding IAQ (CO2, humidity, PM2.5, and formaldehyde-based indicators), energy consumption, and ventilation heat loss. Our results show that DCV strategies can improve IAQ while decreasing airflows. For example, application of DCV reduced the cumulative indicator of occupant exposure to formaldehyde, IHCHO by 6 to 28 %, compared to the constant-airflow system. For humidity controlled mechanical exhaust ventilation, the heat loss can be reduced up 51%.

Introduction of AeroSet software application in mines of Ural Mining and Metallurgical Company

In 2018 Ural Mining and Metallurgical Company, Russia’s largest producer of copper, zinc, coal and precious metals, launched introduction of AeroSet software application at its business entities for the safety assessment in localization and elimination of accidents in mine ventilation modeling. AeroSet is a unit software application for modeling ventilation, air treatment and conditioning in underground mines. This article describes new approaches and tools implemented in AeroSet in 2019–2020. The novel functional of the software was developed in tight cooperation between the Ural Mining Institute and UMMC. The software has ways of exchanging data with Micromine program, and computation tools for blast impact zones and ventilation stability in fire in vertical and inclined underground openings. Today AeroSet possesses the total functional required for computation of accident elimination package, namely, fire development assessment, ventilation calculations, fire-protection water supply modeling, ventilation stability estimation in fire in vertical or inclined underground openings, and determination of blast impact zones. It is intended to improve application of AeroSet in UMMC’s mines towards the standardized calculation of the required air flow rates in mines and the associated optimization of the designs of underground openings, ventilation facilities and the whole ventilation network for the variety of alternate designs of mines, subways, tunnels and other structures, including industrial facilities of heightened danger.The study was carried out in the framework of the Basic Research Program, Project No. 0422-2019-0145-C-01.

Ventilation of roadways using kinetic energy of air flows

The article presents the studies into effectiveness of ventilation by local sources of draught installed in the brattice-free roadways. The relevance of this topic is defined by the need to improve mine ventilation, prevent leaks in the conditions of insufficient fresh air, as well as to remove harmful impurities from faces. The efficiency of ejector units is analyzed versus the aerodynamic drag of a ventilation section and a cross section area of a mixing chamber. On this basis, the optimal parameters for the ejector unit to reach the maximum performance are determined. The numerical simulation of the ejection effect in large crosssection roadways has found that a part of the kinetic energy of the jet is spent for the formation of an air vortex which plays the role of a mixing chamber. The problem connected with insufficient airing is eliminated by means of series arrangement of fans, which reduces air circulation and leakage in minedout voids, and ensures air feed to work spaces. The variants of application of air curtains to reduce air leaks via roadways which cannot be shut by brattices are discussed. It is shown that this method is costeffective when pressure drops are under 2 daPa and is ineffective in prevention of leaks via installations above ground. In ventilation of dead-end roadways, the increase in the distance between the end of the vent pipe and the face surface prevents the damage of the vent pipe by blasted rock chips and reduces the labor input of installation and dismantling. The analytical estimation of the permissible spacing for the face surface–vent pipe is carried out as function of excess flow rate as against the required air flow. The ventilation simulation was carried out using the theory of turbulent jets and elements of numerical simulation in specialized software products for the verification of analytical dependences.The study was supported by the Russian Foundation for Basic Research and by the Perm Krai Government within the framework of R&D Project No. 20-45-596021 r_NOTS_Permskii krai.

Simulation and optimization of a combined cycle power plant with low heating value fuel gas

Combined cycle power plant (CCPP) usually plays an important role in balancing byproduct gas generation and consumption in integrated iron and steel plant. The low heat value fuel gases, such as blast furnace gas (BFG) or mixed gas with Coke oven gas (COG) and BFG, are preferred to be used in high-efficient CCPP for power generation. In practice, the general heat value of mixed gas can be set in the range of 3500–4400[Formula: see text]kJ/Nm3. This paper presents a methodology to simulate operating parameters of CCPP with BFG. A generic model of gas turbine with open loop stage cooling employing air is used to simulate the performance of gas turbines cycle under different compressor pressure ratios and turbine inlet temperatures (TIT). The isentropic efficiencies for gas compressor and gas turbine are supposed to be constants and set corresponding to published industrial experience. The steam cycle is composed of classical double-pressure heat recovery steam generator (HRSG) and steam turbines according to gas turbine outlet temperature. Specific work, gas turbine cycle efficiency, cogeneration thermal efficiency and coolant air flow requirements are evaluated to find the optimal compressor pressure ratio and TIT. The research results are useful to select the optimum operating parameters of CCPP with BFG. Performance features were estimated with the help of compression ratios 12.5–20 and combustor exit temperature 1150–1350[Formula: see text]C.