Piotr Kaczmarzyk

The efficiency of positive-pressure ventilation (PPV) in multi-story buildings is determined not only by the technical parameters of the mobile ventilators but also by the geometry of the gas exchange path. This paper presents the results of a computational fluid dynamics (CFD) analysis conducted using the Large Eddy Simulation (LES) approach to evaluate the impact of varying ceiling and outlet window opening areas on tactical ventilation effectiveness. The numerical model was validated against full-scale experimental data, yielding high convergence for the incoming flow parameters—with flow rate and mean pressure deviations of merely 0.4% and 0.6%, respectively—thereby confirming that the Fire Dynamics Simulator (FDS) is a reliable research tool. The simulations evaluated variations in the opening sizes of ceilings (size coefficients: 1.0, 1.25, and 1.5) and windows (size coefficients: 1.0, 1.5, and 2.25). The volumetric flow rate varied widely, ranging from 13,729 m³/h to 19,148 m³/h, while the pressure drop coefficient ranged between 0.09 and 0.55. The findings demonstrate that enlarging the opening cross-sections along the entire gas exchange path reduces local resistance coefficients, consequently enhancing the total flow rate. Conversely, intentional throttling of the outlet opening enables the effective establishment of an overpressure barrier within the ventilated volume. This study confirms that LES modeling facilitates accurate forecasting of flow variables and optimization of tactical rescue operations without requiring costly full-scale field experiments on physical building structures. The data obtained aid incident commanders in selecting optimal opening configurations depending on the operational priority: dynamic smoke clearance or pressure stabilization within the protected volume.

The effectiveness of mechanical tactical ventilation during rescue and firefighting operations can be improved by multiplying the number of positive pressure ventilators. Such action can shorten the time of the operation, improve its execution, and reduce the energy consumed by the ventilators used during the operation. In order to determine the proper conditions for the two ventilators to work together, tests were conducted on their positioning relative to the doorway. These values were determined from the flow parameters (flow rate and static overpressure generated). A set of conventional rotor ventilators (each with an output of 4.4 kW) was tested. The article performs an analysis of the magnitude of flow parameters depending on the setting of the positive pressure ventilator. Proper positioning of the set of ventilators can increase the flow rate through the facility by up to 32% and the pressure by 50%. The analysis conducted in the article can be used as recommendations for rescue teams for the proper selection of the setting of the positive pressure ventilator during firefighting operations of internal fires.

Concepts such as reuse, repurposing, upcycling, remanufacturing, and re-powering can be applied to the reuse of combustion engines from passenger cars and trucks in stationary or mobile machines, such as power generators. Technical, economic, environmental, and research analyses indicate that such solutions may be justified; however, their implementation is limited by homologation and emission regulations. In most countries, there are no specific rules governing emissions from power generator engines, while in the European Union, such engines are categorized as mobile generators (portable or trailer-mounted) subject to Stage V (Reg. 2016/1628/EU), stationary generators (permanently installed) subject to the MCP Directive (2015/2193/EU), and emergency generators (limited operation) partially exempt from MCP but requiring registration. Consequently, engines recovered from road vehicles do not meet formal or technical emission compliance requirements for power generators and can only be used under conditional approval for research, experimental, or temporary purposes. This reveals a paradox of modern environmental policy: although reusing functional engines from dismantled vehicles could embody the principles of a circular economy, restrictive emission standards (Stage V, MCP, NSPS) effectively prevent such technological recycling. Addressing this issue requires legislative action and the development of simplified testing methods for used engines in new applications. This article is the first to systematically demonstrate that current Stage V, MCP and NSPS emission frameworks create a regulatory paradox that prevents the circular-economy reuse of functional automotive engines, and it proposes a dedicated secondary type-approval pathway enabling their legal and environmentally controlled application in power generators.

Compression–ignition engines emit particulate matter (PM) (soot), prompting the widespread use of diesel particulate filters (DPFs) in the automotive sector. An alternative method for PM reduction involves the use of ultrasonic waves to disperse and modify the structure of exhaust particles. This article presents experimental results of the effects of ultrasonic emitter parameters, including the number, arrangement, and power, along with the engine speed, on the exhaust smoke density. Tests were conducted on a laboratory prototype equipped with six ultrasonic emitters spaced 0.17 m apart. The exhaust source was a diesel engine from a construction excavator, based on the MTZ-80 tractor design, delivering 80 HP and a displacement of 4750 cm³. A regression model was developed to describe the relationship between the engine speed, emitter power and spacing, and smoke density. The optimal configuration was found to involve an emitter power of 319.35 W and a spacing of 1.361 m for a given engine speed. Under the most effective conditions—an engine speed of 1500 rpm, six active emitters, and a total power of 600 W—smoke emissions were reduced by 18%. These findings support the feasibility of using ultrasonic methods as complementary or alternative exhaust gas filtration techniques for non-road diesel engines.

This article demonstrates that machine fires caused by a belt transmission are a fundamental and current research problem. The aim of this work is to identify the hazards during thermal decomposition and combustion of a transmission with a toothed belt, used as a drive or conveyor belt to synchronise mechanisms. The analysis distinguished belts in a polyurethane or rubber cushion with a Kevlar, steel, or polyurethane cord. The belts’ composite structure can be a source of unpredictable emissions and toxic substances of varying concentrations and compositions during thermal decomposition and combustion. To evaluate the compared belts, a testing methodology was used to determine the toxicometric indicators (W_LC50SM), according to which it was possible to assess the toxicity of the thermal decomposition and combustion products following EU standards. The analysis was carried out based on the recorded emissions of chemical compounds during the thermal decomposition and combustion of polymer materials at three different temperatures (450, 550, and 750 °C). The least favourable toxicometric indicators (W_LC50SM) are found in rubber cushion belts, which are very toxic (about 13 g/m³) and toxic (about 40 g/m³) materials. The results show that thermoplastic polyurethane cushion belts are moderately toxic materials, with a W_LC50SM index ranging from 411 g/m³ to 598 g/m³.

Determining the appropriate position of a positive pressure ventilator, where it exhibits the highest efficiency (measured by the achieved volumetric flow rate), can influence the success of rescue operations conducted by fire protection units. The aim of this article is to evaluate the possibility of using LES (Large Eddy Simulation) analyses to verify the positioning parameters of positive pressure ventilators in numerical simulation conditions, without the need for time-consuming experiments. The article presents a comparative analysis of full-scale experimental studies (conducted on a test setup to assess the velocity profile of the air jet in open flow) and CFD numerical analyses. The analysis confirmed the convergence of the flow rate parameter entering the surface of the door opening model installed on the test setup. Depending on the distance of the ventilator position (1–7 m), a convergence degree ranging from 1.6% to 3.8% was achieved for the volumetric flow rate. This publication demonstrates that the LES model is a suitable tool for effectively determining the working positions of positive pressure ventilators, as defined in real working conditions (open flow). The analysis may serve as a helpful tool for manufacturers of mobile ventilators, who can use the method for the technological testing of their units without conducting time-consuming experiments.

The air–fuel ratio is a crucial parameter in internal combustion engines that affects optimal engine performance, emissions, fuel efficiency, engine durability, power, and efficiency. Positive pressure ventilators (PPVs) create specific operating conditions for drive units, characterized by a reduced ambient pressure compared to standard atmospheric pressure, which is used to control carburetor-based fuel supply systems. The impact of these conditions was investigated for four commonly used PPVs (with internal combustion engines) in fire services across the European Union (EU), using a lambda (λ), carbon dioxide (CO₂), carbon monoxide (CO), and hydrogen carbon (HC) analyser for exhaust gases. All four ventilators were found to operate with lean and very lean mixtures, with their lambda coefficients ranging from 1.6 to 2.2. The conducted tests of the CO₂, CO, and HC concentrations in the exhaust gases of all four fans show dependencies consistent with theoretical analyses of the impact of the fuel–air mixture on emissions. It can be observed that as the amount of burned air decreases, the values of CO and HC decrease, while the concentration of CO₂ increases with the increase in engine load. Such an operation can accelerate engine wear, increase the emission of harmful exhaust gases, and reduce the effective performance of the device. This condition is attributed to an inadequate design process, where drive units are typically designed to operate within atmospheric pressure conditions, as is common for these engines. However, when operating with a PPV, the fan’s rotor induces significant air movement, leading to a reduction in ambient pressure on the intake side where the engine is located, thereby disrupting its proper operation.

Positive pressure ventilators (PPV) used by 97.7% of officers of the National Fire Service in Poland, are characterized by work that is not in line with the expectations of the firefighters. In order to improve the technical and operational features of these devices, a survey was conducted among 25,000 eligible firefighters, identifying the application of these devices, problems in use and expected development directions. A total of 682 officers voluntarily completed the survey. Based on their findings, it was determined that ventilators are most often used to smoke out buildings after or during a fire. Mentioned problems when using these devices were mainly noise (78.2%), exhaust emissions (68.5%), and impediments to mobility through the device’s relatively heavy weight (40.2%). Other inconveniences were mentioned by less than 20% of firefighters. Polish firefighters expect the development of these devices mainly in terms of the above-mentioned features (noise reduction (81.7%) and reduction of the weight and size of the ventilators (about 50%)). Other expectations relate to the improvement of smoke removal in buildings: increasing the efficiency of smoke removal (46.4%) and efficiency regarding the rate of smoke removal in a building by increasing the size of the incoming airflow from the building’s surroundings (33.2%). About 15% of firefighters expect changes in the operation of the ventilator itself, that is, an increase in the effective operating time (electric ventilators) and an increase in the device’s uptime. The aim of the article is to identify the issues encountered during the operation and to indicate the expected direction of development for PPV by users. This information can be used by engineers to initiate new development work on these devices.

Positioning the positive pressure ventilator in front of the door opening affects the effectiveness of the rescue operation carried out during a fire. An important factor determining the effectiveness of the positive pressure ventilator is also the layout of the rooms within the gas exchange path and the obstacles present there. The purpose of this article is to assess the feasibility of using analyses such as large eddy simulation (LES) to verify the efficiency of mobile fans under simulation conditions, without the need for time-consuming experimentation (also for complex room volumes of buildings). The article presents a comparative analysis to assess the degree of convergence of flow parameters obtained during an experiment (in a multi-story building) and computational fluid dynamics (CFD) simulations. For volumetric flow rate, convergence was achieved at levels ranging from 0.4% (for 5 m) to 11.5% (1 m), and for pressure values, the differences achieved ranged from 0.6% (5 m) to 30.1% (4 m). This paper demonstrates that the LES model can be used to perform CFD simulations in the area of assessing the performance of a positive pressure ventilator. The article also describes a test methodology for determining the flow parameters of an air stream, which can be used to perform numerical simulations.

The effectiveness of mechanical tactical ventilation during rescue and firefighting operations can be improved by multiplying the number of positive pressure ventilators. Such action can shorten the time of the operation, improve its execution, and reduce the energy consumed by the ventilators used during the operation. In order to determine the proper conditions for the two ventilators to work together, tests were conducted on their positioning relative to the doorway. These values were determined from the flow parameters (flow rate and static overpressure generated). A set of conventional rotor ventilators (each with an output of 4.4 kW) was tested. The article performs an analysis of the magnitude of flow parameters depending on the setting of the positive pressure ventilator. Proper positioning of the set of ventilators can increase the flow rate through the facility by up to 32% and the pressure by 50%. The analysis conducted in the article can be used as recommendations for rescue teams for the proper selection of the setting of the positive pressure ventilator during firefighting operations of internal fires.