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    A novel ignition timing strategy to regulate the energy balance during the warm up phase of an SI engine
    (Elsevier Ltd, 2023) Köksal, Hüseyin; Ceviz, Mehmet Akif; Yakut, Kenan; Kaltakkıran, Galip; Özakin, Ahmet Numan
    The warm up characteristics of an engine have a significant impact on engine performance and exhaust emissions. In SI engines, the light-off performance of the catalytic converter is also important. One of the methods used to shorten the light off time of the catalytic converter is to retard the ignition time. When the ignition time is retarded, the temperature of the exhaust gases increases. However, in this case, the warm up performance of the engine itself may be adversely affected. In this study, firstly, the effects of ignition timing on the energy balance during the warm up period in an SI test engine were revealed. Then, a novel ignition timing strategy was proposed in order to increase the temperature of the exhaust gases, and not to reduce the engine performance. The novel ignition timing strategy working on the principle of sequentially advanced and retarded ignition at certain intervals during the warm up period provides several advantages. When the novel ignition strategy is applied, the energy loss through the exhaust gas was increased up to 7.2% for several operating conditions, while the reduction in engine performance is eliminated. Moreover, 20% reduction in NO emission has been achieved. © 2022 The Authors.
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    Experimental performance assessment of two-stage thermoelectric system in a closed-cycle drying process
    (Pergamon-Elsevier Science Ltd, 2025) Osta, Muhammet Harun; Yakut, Kenan; Koksal, Huseyin
    Traditional drying systems suffer from several limitations, including high energy consumption, insufficient hygienic control, and the inability to maintain precise temperature regulation. Although alternative drying systems have been developed to address these issues, they often encounter practical challenges due to their complex structures and the need for numerous external components. To overcome these limitations, this study proposes and experimentally evaluates a novel, independently operating, two-stage thermoelectric module (TEM) system integrated into a closed-loop drying setup that eliminates the need for external heating and dehumidification components. The proposed system addresses the efficiency and hygiene problems observed in conventional dryers by simultaneously performing air heating, cooling, and dehumidification functions through compact thermoelectric devices. The drying process consists of two stages: the first involves air pre-conditioning (heating/ cooling), while the second is dedicated to dehumidification. The performance of the system has been evaluated based on key metrics such as cooling and heating capacities, the coefficients of performance (COP) for both stages, moisture removal rate (MRR), and moisture removal rate effectiveness (EffMRR). Experimental studies were conducted under input voltages ranging from 3 to 7 V, relative humidity levels between 60 % and 90 %, and varying airflow rates. Under 90 % relative humidity conditions and a 7 V input voltage, the system achieved a maximum moisture removal rate of 13.1 g/h. The first-stage TEM reached a heating capacity of 68.81 W and a cooling capacity of 26.34 W, while the second stage provided 21.17 W of cooling capacity.
  • Küçük Resim Yok
    Öğe
    A novel ignition timing strategy to regulate the energy balance during the warm up phase of an SI engine
    (Elsevier, 2023) Koksal, Huseyin; Ceviz, Mehmet Akif; Yakut, Kenan; Kaltakkiran, Galip; Ozakin, Ahmet Numan
    The warm up characteristics of an engine have a significant impact on engine performance and exhaust emissions. In SI engines, the light-off performance of the catalytic converter is also important. One of the methods used to shorten the light off time of the catalytic converter is to retard the ignition time. When the ignition time is retarded, the temperature of the exhaust gases increases. However, in this case, the warm up performance of the engine itself may be adversely affected. In this study, firstly, the effects of ignition timing on the energy balance during the warm up period in an SI test engine were revealed. Then, a novel ignition timing strategy was proposed in order to increase the temperature of the exhaust gases, and not to reduce the engine performance. The novel ignition timing strategy working on the principle of sequentially advanced and retarded ignition at certain intervals during the warm up period provides several advantages. When the novel ignition strategy is applied, the energy loss through the exhaust gas was increased up to 7.2% for several operating conditions, while the reduction in engine performance is eliminated. Moreover, 20% reduction in NO emission has been achieved.