تجزیه و تحلیل عملکرد از یک سیستم جدید از یک سیکل رانکین آلی حلقه دوگانه (ORC) با یک موتور دیزلی نوری
|کد مقاله||سال انتشار||مقاله انگلیسی||ترجمه فارسی||تعداد کلمات|
|28066||2013||10 صفحه PDF||سفارش دهید||6420 کلمه|
Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : Applied Energy, Volume 102, February 2013, Pages 1504–1513
A small-scale organic Rankine cycle (ORC) can be used to harness the waste heat from an internal combustion engine. In this paper, the characteristic of a novel system combining a vehicular light-duty diesel engine with a dual loop ORC, which recovers waste heat from the engine exhaust, intake air, and coolant, is analyzed. A high temperature loop recovers the exhaust heat, whereas a low temperature loop recovers the residual heat from the high temperature loop and the waste heat from both the intake air and the coolant. A performance map of the light-duty diesel engine is created using an engine test bench. The heat waste from the exhaust, the intake air, and the coolant are calculated and compared throughout the engine’s entire operating region. Based on these data, the working parameters of the dual loop ORC are defined, and the performance of the combined engine–ORC system is evaluated across this entire region. The results show that the net power of the low temperature loop is higher than that of the high temperature loop, and the relative output power improves from 14% to 16% in the peak effective thermal efficiency region and from 38% to 43% in the small load region. In addition, the brake specific fuel consumption (bsfc) of the combined system decreases significantly throughout the engine’s operating region.
Huge amounts of energy are consumed by internal combustion engines in all types of vehicles, with much of this energy is wasted through the exhaust, the intake air, and the cooling systems. Exacerbating this problem is the fact that these combustion products also cause serious environmental issues. Engine waste-heat recovery could improve the fuel thermal efficiency, minimize fuel consumption, and reduce engine emissions. Using an organic Rankine cycle (ORC) to recover the low-grade wasted heat from these systems is the technology that is the closest to being suitable for mass production. When designing an ORC, special attention must give to the choice of the working fluid and the design of a suitable expander , , , , ,  and . Many researchers have investigated ORC system design and parametric optimization. The dynamic performance and control strategy was investigated by Ref.  using a time-varying model. The results indicate that the steady-state optimization of ORC under various conditions is very important. The parameter optimization and performance comparison was also conducted by Ref.  for low-temperature heat source (80–100 °C). When an engine is running, the energy and exergy quantities of the exhaust, the intake air, and the coolant are significantly different. Because of these differences, it is very difficult to design a system that can recover waste heat from all of these systems. Previous investigations have been conducted to solve this problem for various engines , , , ,  and . However, few of these investigations have concentrated on light-duty diesel engine applications. In this paper, a dual loop ORC system is designed, combining a high temperature (HT) loop and a low temperature (LT) loop to simultaneously recover the waste heat from the exhaust, the intake air, and the coolant of a light-duty diesel engine. The HT loop recovers the exhaust heat, whereas the LT loop recovers the residual heat from the HT loop and the waste heat from both the intake air and the coolant. The two separate loops are coupled through a pre-heater. To evaluate the dual loop system performance when combined with a light-duty diesel engine, the waste heat quantities are first calculated using engine test data. Based on these calculations, the working parameters for the HT and LT loops are determined. R245fa and R134a are selected as the working fluids for the HT loop and the LT loop, respectively. Finally, the performance map of the combined system is calculated and compared to a system with a non-bottoming ORC.
نتیجه گیری انگلیسی
In this study, the waste heat from the exhaust, the intake air, and the coolant of a R425 diesel engine are analyzed using measured data. A novel dual-loop ORC system is designed to recover the waste heat from the exhaust, the intake air, and the coolant. The performance map of the combined system is evaluated over the engine’s entire operating region. Based on this analysis, the following can be concluded: 1. The combustion energy is much greater than the engine output power through most of the operating region. The exhaust gas enthalpy (30.5–54.5% of the total combustion energy) is slightly higher than the indicated power (22.4–44.4% of the total combustion energy). The waste heat from the intake air is smaller than that from the coolant. It is, however, still worthwhile to recover this energy in the middle and high engine power region. 2. A dual loop ORC system is designed to recover heat from these three distinct sources simultaneously. An HT loop recovers the exhaust waste heat using R245fa as the working fluid. An LT loop recovers the waste heat from the coolant and the intake air, as well as the residual heat from the HT loop using R134a as the working fluid. The results show that the net power of the LT loop is higher than that of the HT loop (a total of 6.98 kW for the HT loop versus 11.91 kW for the LT loop at the rated power point). 3. The performance map of the combined system is evaluated using the first law method. In the peak effective thermal efficiency region, the augmentation proportion of the effective power for the combined system is the lowest, at 14–16%, but is highest in the small-load and high-speed region where the augmentation proportion is 38–43%. The bsfc is also found to significantly decrease throughout the engine’s operating region. From the viewpoint of power performance and fuel economy, the dual loop ORC system is a promising scheme to recover the waste heat from a vehicular light-duty diesel engine.