In the current investigation, raw biogas obtained from rural sectors was used as the alternative to gasoline fuel in the spark ignition (SI) engine. The performance and efficiency are mainly dependent on the combustion phasing for which "ignition timing" is an effective tool in a SI engine. Hence, the objective of the present work is to understand the effect of "variable ignition timing" for a biogas-fueled SI engine. For this purpose, a single cylinder, 4-stroke, SI engine of rated power 4.5 kW was operated with raw biogas at a compression ratio (CR) of 10. By maintaining a speed of 1650 rpm, the engine was operated in wide open (WOT) and part throttle (PT) mode with an equivalence ratio of 0.81 and 0.83, respectively. It was observed that the biogas fueled SI engine was found to be operative only within the ignition advance (IA) range of 33–47° CA bTDC both in WOT and PT conditions. The results showed optimal brake power (BP), brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) are achieved at 45° CA bTDC. The average peak cylinder pressure, neat heat release rate (NHRR) and mean gas temperature (MGT) are also observed to be maximum while CO and HC emission at this point of IA were found to be minimum. Due to controlled and complete combustion, CO2 and NOx concentration in the exhaust emission were found to be higher at this point of ignition timing.
The usage of biogas as a potential fuel in a spark ignition (SI) engine is the theme for the present study. The exhaust gas recirculation (EGR) is a significant technique for improving the performance of the SI engine. Thus, the novelty of the experimental investigations lies in implementing the EGR technique for emission control of the biogas-fueled engine. The raw biogas (52% methane and 47% carbon dioxide), obtained from a biogas digester (using cow dung as the source), was the engine fuel for a four stroke, water cooled, variable compression ratio SI engine set-up. Here, the engine performance and emission related parameters were measured. When operated in the raw biogas mode at an optimum spark timing of 45 °CA before the top dead center, the engine produced maximum torques of 11 N m, 14 N m, and 16 N m for compression ratios 8, 9, and 10, respectively. The effect of different EGR rates on the emission control was also investigated. The net heat release rate without EGR was found to be 22.623J/°CA at 368 °CA, which further reduced to 14.233 J/°CA at 386 °CA for EGR10. Moreover, it was clearly evident that low EGR rates (below 10%) were effective in reducing NOX significantly, with minor compromise in power and brake specific fuel consumption. But the emissions of hydrocarbon and carbon monoxide were found to be higher with the increase in EGR. The operation of the engine with medium or heavy EGR rates resulted in issues related to intense pressure fluctuations and large cycle-to-cycle variation in performance. Thus, the present investigations recommend the use of low EGR (below 10%) in a biogas-based engine for lower NOX emission and better fuel efficiency.
In the present investigation, experiments were conducted in a 4.4 kW, single cylinder, water cooled, constant speed, spark ignition (SI) engine fuelled with raw biogas.The engine was operated at four different compression ratios (10.52, 11.94, 13.96 and 15.29) and within a load range of 6 to 77%.The effect of load level on the performance and emission characteristic of the engine at different compression ratios are analysed and presented in this paper.The brake power producing capability of the engine corresponds to CR 15.29 was maximum and found to be 2.93 kW with 76.27% of brake load.With increasing CR the engine becomes more stable and operates with an appreciable deviation in speed.Irrespective of engine loading condition, the minimum HC and CO emissions were noticed at CR 15.29 and found to very between 23-144 ppm and 0.016-0.091%, respectively.The maximum NOx emission was detected at CR 15.29 and was found to very between 27-240 ppm.
This paper presents a comparative study on thermal performance between a traditional cookstove and an improved cookstove based on energy, exergy and emission. Intending to diminish the use of wood for daily domestic cooking practice in local area, this paper emphasizes on the optimum and efficient utilization of plant-based biomass (peanut shell) as fuel for cookstoves. The thermal and emission performances of two stoves were determined by lab-based water boiling test (WBT). The energy and exergy efficiencies of traditional stove for cold start were 10.70±2.26% and 1.26±0.96%, respectively, whereas those for hot start were 13.21±2.18% and 1.46±1.02%, respectively. Similarly for improved cookstove, the energy and exergy efficiencies were recorded 19.28±1.89% and 3.32±1.11% in cold start condition, and those were 23±1.93% and 4.56±1.23% in hot start condition. The time average values of carbon monoxide (CO) and particulate matter (PM) were recorded as 75±6.21ppm and 7000±1900 µg/m3, respectively for traditional cookstove, and those for improved one were 15±4.89 ppm and the 3806±1175 µg/m3, respectively.
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