Identification of the Problem in Controlling the Air–Fuel Mixture Ratio (Lambda Coefficient λ) in Small Spark-Ignition Engines for Positive Pressure Ventilators

Łukasz Warguła (), Piotr Kaczmarzyk, Bartosz Wieczorek, Łukasz Gierz, Daniel Małozięć, Tomasz Góral, Boris Kostov and Grigor Stambolov
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Łukasz Warguła: Institute of Machine Design, Faculty of Mechanical Engineering, Poznan University of Technology, Piotrowo 3, 60-965 Poznań, Poland
Piotr Kaczmarzyk: Institute of Machine Design, Faculty of Mechanical Engineering, Poznan University of Technology, Piotrowo 3, 60-965 Poznań, Poland
Bartosz Wieczorek: Institute of Machine Design, Faculty of Mechanical Engineering, Poznan University of Technology, Piotrowo 3, 60-965 Poznań, Poland
Łukasz Gierz: Institute of Machine Design, Faculty of Mechanical Engineering, Poznan University of Technology, Piotrowo 3, 60-965 Poznań, Poland
Daniel Małozięć: Scientific and Research Centre for Fire Protection, National Research Institute, Nadwiślańska 213, 05-420 Józefów, Poland
Tomasz Góral: Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, A. Mickiewicza 30, 30-059 Krakow, Poland
Boris Kostov: Department of Heat, Hydraulics and Environmental Engineering, University of Rousse “Angel Kanchev”, 8 Studentska Street, 7017 Ruse, Bulgaria
Grigor Stambolov: Department of Manufacturing Technology, Faculty of Machine Technology, Technical University of Sofia, 8 bul. Kliment Ohridski Street, 1756 Studentski Kompleks, 1756 Sofia, Bulgaria

Energies, 2024, vol. 17, issue 17, 1-15

Abstract: 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 (CO 2 ), 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 CO 2 , 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 CO 2 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.

Keywords: PPV; fuel supply system control; incorrect operation of a combustion engine; lean fuel–air mixture; fire brigade equipment; smoke removal from buildings (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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