• Energy Research

In this study, nitrogen oxides emission reduction is investigated with humid combustion in a non-premixed combustion chamber of a gas turbine that burns natural gas using computational fluid dynamics. For humidification of the combustion chamber, two methods are studied: direct water injection into the combustion chamber and increasing the inlet air humidity. The mathematical model of combustion, governing equations, numerical method, and the combustion chamber properties are extensively discussed. The mathematical model is first validated. The two approaches are then simulated and compared for low water and steam flow rates. The results show that at the water to fuel ratio of about 1, direct water injection is 1.69 times more efficient than increasing inlet air humidity in reducing nitrogen oxide emission. Finally, it is concluded that direct water injection is appropriate at low flow rates (up to the fuel flow rate) and for situations where reducing nitrogen oxide emission is highly relevant. Furthermore, increasing the humidity of the inlet air up to 25% is suitable and increases the combustion efficiency and reduces pollutants, while the outlet temperature is not decreased too much.

Abstract A novel thermal management system including wavy/stair channel liquid cooling and copper sheath is developed and studied experimentally in this investigation to control the temperature of cylindrical lithium-ion batteries. The influences of different variables on cooling performance during charge/discharge operations are investigated: C-rate, alumina nanoparticle concentration, inflow velocity, and stair channel geometry. The experiments are conducted with two volume fractions of 1% and 2%. With increasing the concentration of alumina nanoparticles in the deionized water, the maximum temperature and temperature difference reduced remarkably. Also, the non-uniformity of the temperature is reduced, while an increase in the inflow velocity results in reducing the peak temperature and temperature non-uniformity. Additionally, to control the cooling capacity and temperature distribution inside a battery pack, a new method—liquid cooling lithium-ion battery thermal management system—is developed based on the stair channel cooling. The stair channel reduced the maximum temperature and temperature non-uniformity of the battery pack under 5C discharge process compared to the straight channel by about 3.59 K and 0.65 K, respectively. The results show that these approaches can reduce the maximum temperature and temperature non-uniformity of the battery pack under 5C discharge/charge operations to values lower than 305.13 K and 2.01 K, respectively.

Abstract In the present paper, a novel method is proposed to enhance the power production and resolve the inconsistent electricity generation of solar chimney power plants (SCPPs) during nighttime. For this purpose, an integrated renewable cycle is proposed by incorporating two technologies: solar chimney and waste-to-energy. The combination is performed by exploiting the warm air of the condensers outlet into the SCPP. The waste-to-energy (WTE) plant in Tehran is thermodynamically analyzed and the mass flow rate of the condensers cooling air is found. Results indicate that by decreasing the humidity of the municipal solid waste (MSW) from 40% to 30% or by increasing MSW feeding rate (0.934–1.146 kg/s), the mass flow rate of the condenser cooling air increases from 190.3 kg/s to 233.7 kg/s. In addition, by increasing the feeding rate or by decreasing the humidity of MSW in the mentioned range, net power output of the WTE plant increases from 1350 kW to 1650 kW. The best injection method is proposed for the warm air of the condensers outlet into the SCPP. Subsequently, the average power increase is examined in different months and parametric study is performed to assess the influence of the effective WTE parameters and meteorological variables on the power output of the SCPP. The final power of the SCPP reaches 20–70 kW (even at the hottest night of the year with 5% relative humidity) and increases 20–1200% and 65–94% (monthly average) compared to the case of without injection. Results demonstrate that in the integrated system, by a 22% increase in the MSW feeding rate (from 0.934 kg/s to 1.146 kg/s) or by decreasing the MSW moisture content (from 40% to 30%), power output of the WTE plant and SCPP increases by 22% and 7%, respectively. Additionally, relative humidity of the surrounding air can increase the SCPP power production by 25%. In addition, the results indicate that wind speeds higher than 12.5 m/s will not affect power production of the SCPP, while relative humidity of the surrounding air, ambient temperature, the MSW feeding rate, and humidity of the MSW have considerable effects on the SCPP power production. In average, total energy and useful exergy efficiency of the proposed system is increased by 0.15% and 0.12% compared to the standalone WTE plant during nighttime. The integration of SCPP with the WTE plant is an applicable method to enhance the power generation and overcome the inconsistent power production of SCPP during nighttime.

AbstractIn the present paper NOx emissions from biomass combustion was studied, with the objective to demonstrate the applicability of stationary computational fluid dynamics simulations, including a detailed representation of the gas phase chemistry, to a multi-fuel lab-scale grate fired reactor using biomass as fuel. In biomass combustion applications, the most significant route for NOx formation is the fuel NOx mechanism. The formation of fuel NOx is very complex and sensitive to fuel composition and combustion conditions. And hence, accurate predictions of fuel NOx formation from biomass combustion rely heavily on the use of chemical kinetics with sufficient level of details. In the present work we use computational fluid dynamics together with three gas phase reaction mechanisms; one detailed mechanism consisting of 81 species and 1401 reactions, and two skeletal mechanisms with 49 and 36 species respectively. Using the detailed mechanism (81 species), the results show a high NOx reduction at a primary excess air ratio of 0.8, comparable to the NOx emission reduction level achieved in the corresponding experiment, demonstrating both the validity of the model and the potential of NOx reduction by staged air combustion.

The thermodynamic analysis carried out focuses on biomass mixing to reduce the formation of corrosive (mainly alkali) chlorides during straw combustion. The calculations confirm the reduction abilities of sewage sludge and peat and provide information on the addition levels at which no corrosive compounds are expected to form. The calculations provide insight into the mechanisms responsible for the disappearance of alkali chlorides. The mechanisms that can potentially take place are known (reaction with sulfur and reaction with or adsorption on aluminosilicates or other ash compounds). However, many aspects remain unclear, and calculations cast light on several of them. The main result obtained in this study is that, in a given binary mixture, the chemical elements involved in the decomposition of corrosive alkali chlorides (or preventing them from forming) change with the mixing proportions, an important fact never mentioned to our knowledge. The practical implications are significant: in a real system, ...

Abstract Lithium ion batteries are considered as the main energy storage option. High temperatures cause capacity fading and can even produce fire. It is, therefore, essential to design an effective thermal management system (TMS) to keep battery temperature in the safe range. In this study, thermal response of lithium ion batteries is investigated in high discharge rates with a new TMS combining active and passive methods. Refined paraffin in blockform (P 42–44 #107150) combined with porous copper metal foam was considered as the passive part and aluminium mini-channel containing coolant flow was regarded as the active part of TMS. The experiments were conducted at three different Reynold numbers in active and hybrid methods and it was shown that at higher flowrates the maximum temperature is lower. The research has also shown that passive cooling was inefficient in keeping the battery temperature below the safety limit of 60 °C in high discharge rates. The hybrid thermal management system (HTMS) reduced the steady-state temperature of batteries by 19.5% compared to active method at a Reynolds number of 340 and heat generation power of 3.7 W. The active method was also ineffective in controlling the battery temperature at high heat generation power levels while HTMS showed an appropriate thermal performance at the same condition. Furthermore, effect of utilizing Al2O3-water nanofluid with two different volume fractions was investigated in both active and hybrid systems. It was shown that, compared to the base case with water flow, nanofluid can reduce the maximum temperature of batteries by 15.5% and 8.5% in active and hybrid methods, respectively.

The combustion of biomass, in this case demolition wood, has been investigated in a grate combustion multifuel reactor. In this work a temperature range of 850–1000 °C is applied both for staged ai...