تاثیر سوخت‌های گازی و دمای مایع خنک‌کننده بر مشخصه‌های عملکردی و احتراقی یک موتور تک سیلندر دیزل دور پایین

در این پژوهش تاثیر استفاده از سوخت‌های گاز طبیعی فشرده و گاز نفتی مایع بر مشخصه‌های عملکردی و احتراقی یک موتور دیزل تک سیلندر، چهار زمانه، آب خنک با مکش طبیعی و به‌صورت مختلط‌ سوز مطالعه شد. هدف اصلی در این پژوهش تعیین شاخص‌های عملکردی و مشخصه‌های احتراقی موتور در محدوده عملکرد گاورنر و در سرعت‌ها و دماهای مختلف مایع خنک‌کننده‌ی موتور بوده است. آزمایش‌ها در شرایط پایدار برای حالت‌های کارکرد موتور با سوخت گازوییل خالص و مختلط‌ سوز گازوییلگاز و در سرعت‌ها و دماهای مختلف مایع خنک‌کننده‌ی موتور به‌صورت آزمایش‌های فاکتوریل در قالب طرح بلوک‌های کامل تصادفی در سه تکرار انجام و مشخصه‌های عملکردی موتور اندازه‌گیری شد. نتایج آزمایش موتور نشان داد که گشتاور، توان ترمزی و فشار موثر متوسط ترمزی در حالت مختلط‌سوز گازوییلcng نسبت به حالت سوخت گازوییل خالص در تمامی سرعت‌ها و در حالت مختلط‌‌ سوز گازوییلlpg در سرعت‌های پایین موتور افزایش معنی‌داری یافتند. مصرف سوخت و انرژی ویژه‌ی ترمزی نیز با افزایش دمای مایع خنک‌کننده در سرعت‌های پایین موتور و همچنین کارکرد موتور به‌صورت مختلط‌سوز کاهش معنی‌داری را نشان دادند. همچنین با افزایش دمای مایع خنک‌کننده و کارکرد موتور با حالت مختلط‌ سوز بازده حرارتی ترمزی و بازده حجمی به‌ترتیب افزایش و کاهش معنی‌داری را نشان دادند. به‌طورکلی، نتیجه‌گیری شد که استفاده از موتور به‌صورت مختلط‌ سوز گازوییلcng و دمای مایع خنک‌کننده 60 درجه سلسیوس در تمامی سرعت‌ها بهترین نتیجه را روی مشخصه‌های عملکردی و احتراقی موتور دارد.

Effect of Gaseous Fuels and Coolant Temperature on Performance and Combustion Characteristics of a Low-Speed Single Cylinder Diesel Engine

IntroductionToday, diesel engines provide the main power source for the world equipment e.g., common propulsion generators in industry and agriculture. These engines are widely used due to their high combustion efficiency, reliability, compatibility, and costeffectiveness. However, diesel engines are one of the most critical consumers of fuel which in turn causes some environmental pollution. One of the convenient and lowcost ways to reduce the pollution of these engines is dualfuel mode and the use of gaseous fuels as an alternative fuel. This study investigated the effect of blending CNG and LPG with neat diesel in dualfuel mode. Besides, the variation in engine coolant temperature on engine performance characteristics was experimentally studied.Materials and MethodsThe experimental apparatus consisted of a stationary, fourstroke, naturally aspirated, watercooled, singlecylinder compression ignition engine. To control the engine load, an electrical dynamometer was made using a 7.5 kW threephase generator and coupled to the engine as a cradle. A load cell was used to determine the force applied to the generator. The engine speed was monitored continuously by a tachometer. Fuel consumption was measured by using a weight method. A thermostat with variable temperature was used to control the temperature of the engine coolant. To measure the mass flow of air entering the cylinder, an airbox with a sharp edge orifice was used. For this study, factorial experiments in the form of a randomized complete block design with three replications were utilized to analyze the data statistically. The studied parameters were three levels of fuel ratio (100% diesel, 20% diesel and 80%± 2% CNG, 20% diesel and 80%±2% LPG), 11 engine speeds (1500 to 1600 rpm with 10 rpm intervals), and three engine coolant temperatures (50, 60, and 70 °C). All experiments were conducted in the governor control mode.Results and DiscussionThe results showed that the torque, brake power and brake mean effective pressure (BMEP) in the dieselCNG mode at all engine speeds and in the dieselLPG mode at low engine speeds significantly increased compared to pure diesel. The increases in these parameters in the dieselCNG mode were 18.67%, 19.56% and 19.85%, and in the dieselLPG mode were 14.02%, 13.86% and 14.2%, compared to those related to the pure diesel, respectively. This increase could be due to the high calorific value of gas fuels and improvement of combustion inside the cylinder due to the formation of homogeneous charge. At low engine speeds, the reductions in the brake specific fuel consumption (BSFC) and brake specific energy consumption (BSEC) for coolant temperature 60 °C were 11.21% and 10.77%, compared to coolant temperature 50 °C, respectively. Also, the BSFC and BSEC for dieselCNG dualfuel mode decreased by 8.12% and 10.81%, respectively. These values for the dieselLPG dualfuel mode were 5.4% and 2.4%, respectively. The brake thermal efficiency (BTE) also showed a significant increase at high speeds and when using the dualfuel operational mode. However, raising the coolant temperature due to reducing the heat losses of the engine increased the BTE. The increases in BTE for coolant temperatures 60 and 70 °C were 7.19% and 4.37%, compared to the coolant temperature of 50 °C, respectively. When using the engine in dualfuel mode, the volumetric efficiency due to reducing the air ratio showed a significant reduction. These dieselCNG and dieselLPG dualfuel mode values were 20.31% and 24%, respectively. Furthermore, raising the coolant temperature diminished the volumetric efficiency. The reduction in volumetric efficiency for the coolant temperatures of 60 °C and 70 °C were 6.84% and 19.91% compared to the coolant temperature of 50 °C, respectively.ConclusionThe following conclusions can be deduced based on this study:The use of gaseous fuels as the main fuel and with a small amount of diesel in compression ignition engines is possible and improves the engine’s performance characteristics.In the dieselCNG mode, torque, brake power and BMEP at all engine speeds and in the dieselLPG mode at low engine speeds significantly increased compared to pure diesel because of improved combustion inside the cylinder.At low engine speeds, increasing the coolant temperature reduced the BSFC and BSEC. Also, in the dualfuel mode compared to the engine with baseline diesel fuel, the BSFC and BSEC were significantly lower due to the higher calorific value of gaseous fuels and higher power generation.The BTE at high engine speeds and when the engine was in dualfuel mode showed a significant increase. Also, increasing the coolant temperature due to reducing the heat losses of the engine increased the BTE.When using the engine in the dualfuel mode, due to the volume of air replaced by the gas, the volumetric efficiency showed a significant reduction. Also, raising the coolant temperature diminished the volumetric efficiency.Overall, it can be stated that the use of a dieselCNG dualfuel mode with a coolant temperature of 60 °C at entire engine speeds has the best outputs on the performance and combustion characteristics of the engine.