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考虑实际动力装置的尺寸约束,基于有限时间热力学的思想建立了具有压降不可逆性的开式双轴燃气轮机循环模型。在该模型中,工质沿途有八种流阻。这些流动阻力均为模型入口相对压降的函数,控制着循环输出功率等性能参数。导出的性能参数的函数表明,通过改变质量流率(或沿通流路径压力损失)可以使开式双轴燃气轮机循环的热力学性能最优。结果表明,循环最大输出功率对应一个最佳的质量流率(或沿通流路径压力损失),如此也可以确定一个压气机压比的附加最大值。在燃油消耗和装置总尺寸约束条件下,对模型入口和出口之间的流通面积进行优化分配,可以进一步优化循环功率效率。 相似文献
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《热力透平》2016,(3)
对中冷后回热式布雷顿-逆布雷顿联合循环构型进行有限时间热力学分析和优化,推导出了燃料燃烧放热流率、循环净功率、循环热效率和各个部件由于流动不可逆性产生的压力损失与顶循环压气机进口相对压力损失的函数关系。给出了循环净功率的分析和优化结果,以及在燃油消耗和尺寸约束条件下循环热效率的分析和优化结果。通过数值计算,详细分析了各主要设计参数对循环最优性能的影响。研究发现,存在最佳的中冷压比、压气机1进口相对压力损失、压气机3的压比和总压比,使循环功率获得最优值;在燃油消耗和装置尺寸的约束下,存在最佳的中冷压比、压气机1进口相对压力损失和总压比,使循环效率获得最优值;中冷过程能有效提高循环的功率,回热对循环功率影响很小。 相似文献
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考虑实际动力装置的尺寸约束,基于有限时间热力学的思想建立了具有压降不可逆性的开式微型燃气轮机外燃循环模型。在该模型中,工质在流动过程中将依次遭遇8种流动阻力。这些流动阻力均为压气机入口相对压降的函数,并且控制着质量流率和循环输出功率。导出的循环输出功率、效率及其它的一些参数的表达式表明,调整质量流率可以优化开式微型燃气轮机外燃循环的热力学性能。分析表明,存在最佳的质量流率使循环输出功率最大,该最大功率对应于压气机压比存在附加最大值。给定动力装置燃油消耗和总尺寸的情况下,通过合理分配压气机入口和涡轮机出口之间的流通面积,可以进一步使循环功率效率最大化。 相似文献
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本文研究恒温和变温热源条件下具有等熵压缩、膨胀过程的闭式燃气轮机回热循环有限时间热力 学性能,导出两种情况下的功率输出和热效率与循环压比间的关系,由此可得最佳功率、效率特性。对于给定的热源条件,回热对循环功率有很大影响,这一结论与经典的分析明显不同。分析中计入了工质与高,低温热源间换热器和回热器的热阻损失,当不计高、低温侧换热器的热阻损失时,本文结果与经典结论一致。 相似文献
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具有等熵压缩、膨胀过程的闭式燃气轮机回热循环有限时间热力学性能 总被引:2,自引:2,他引:0
本文研究恒温和变温热源条件下具有等熵压缩、膨胀过程的闭式燃气轮机回热循环有限时间热力学性能,导出两种情况下的功率输出和热效率与循环压比间的关系,由此可得最佳功率、效率特性.对于给定的热源条件,回热对循环功率有很大影响,这一结论与经典的分析明显不同.分析中计入了工质与高、低温热源间换热器和回热器的热阻损失.当不计高、低温侧换热器的热阻损失时,本文结果与经典结论一致. 相似文献
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为了解决燃气轮机高温部件热防护问题,采用实验研究涡流管在不同进口压力(0.20~0.65 MPa)和冷气流率(0.17~0.89)下的冷却特性。实验结果表明:实际温降,在不同进口压力下随着冷气流率的增加先增大后减小,在相同冷气流率下随着进口压力的增大而增大;温度〖JP2〗效率,在不同进口压力下随着冷气流率的增大先增大后减小,在冷气流率等于0.5时达到最大值;绝热效率,在进口压力等于0.20 MPa时最小,在大于0.30 MPa时随着进口压力的增加变化不大;制冷效率,随冷气流率的增加会先增加后减小,进口压力等于0.30和0.40 MPa时制冷效率最高。 相似文献
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《Applied Energy》2004,78(2):199-218
A performance analysis and optimization of a open-cycle regenerator gas-turbine power-plant is performed in this paper. The analytical formulae about the relation between power output and cycle overall pressure-ratio are derived taking into account the eight pressure-drop losses in the intake, compression, regeneration, combustion, expansion and discharge processes and flow process in the piping, the heat-transfer loss to the ambient environment, the irreversible compression and expansion losses in the compressor and the turbine, and the irreversible combustion loss in the combustion chamber. The power output is optimized by adjusting the mass-flow rate and the distribution of pressure losses along the flow path. Also, it is shown that the power output has a maximum with respect to the fuel-flow rate or any of the overall pressure-drops and the maximized power output has an additional maximum with respect to the overall pressure-ratio. The numerical example shows the effects of design parameters on the power output and heat-conversion efficiency. 相似文献
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A thermodynamic model for open combined Brayton and inverse Brayton cycles is established considering the pressure drops of the working fluid along the flow processes and the size constraints of the real power plant using finite time thermodynamics in this paper. There are 11 flow resistances encountered by the gas stream for the combined Brayton and inverse Brayton cycles. Four of these, the friction through the blades and vanes of the compressors and the turbines, are related to the isentropic efficiencies. The remaining flow resistances are always present because of the changes in flow cross-section at the compressor inlet of the top cycle, combustion inlet and outlet, turbine outlet of the top cycle, turbine outlet of the bottom cycle, heat exchanger inlet, and compressor inlet of the bottom cycle. These resistances control the air flow rate and the net power output. The relative pressure drops associated with the flow through various cross-sectional areas are derived as functions of the compressor inlet relative pressure drop of the top cycle. The analytical formulae about the relations between power output, thermal conversion efficiency, and the compressor pressure ratio of the top cycle are derived with the 11 pressure drop losses in the intake, compression, combustion, expansion, and flow process in the piping, the heat transfer loss to the ambient, the irreversible compression and expansion losses in the compressors and the turbines, and the irreversible combustion loss in the combustion chamber. The performance of the model cycle is optimized by adjusting the compressor inlet pressure of the bottom cycle, the air mass flow rate and the distribution of pressure losses along the flow path. It is shown that the power output has a maximum with respect to the compressor inlet pressure of the bottom cycle, the air mass flow rate or any of the overall pressure drops, and the maximized power output has an additional maximum with respect to the compressor pressure ratio of the top cycle. When the optimization is performed with the constraints of a fixed fuel flow rate and the power plant size, the power output and efficiency can be maximized again by properly allocating the fixed overall flow area among the compressor inlet of the top cycle and the turbine outlet of the bottom cycle. 相似文献
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This study involves the design of a single flash cycle which comprises a separator, steam turbine, condenser and pump combined with Organic Rankine Cycle (ORC). The ORC has a three-stage heat exchanger. The mass flow rate of the organic fluid varies depending on the type of organic fluid. The system is heated by geothermal water. The effect of changing the geothermal water temperature [200–260°C] on performance parameters including the power output and overall efficiency has been studied. Four working fluids (n-Butane, Isobutane, R11 and R123) were chosen depending on their properties. The results show that a drop in the source temperature (T1) by 10% will result in 9.7% and 25.3% drop in overall efficiency and net power output for Isobutane. Also, Isobutane has a drop of 4.2% in both; overall efficiency and net power output for a 10% drop in pressure ratio (rp). R11 shows the highest overall efficiency and net power output (18.76% and 24.887 MW) respectively at the design point. 相似文献
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To recover the waste heat from solid oxide fuel cell (SOFC) and improve the overall electrical efficiency, a new integrated power system driven by SOFC is proposed to achieve the cascade energy utilization. This system integrates an SOFC–GT system with an organic Rankine cycle (ORC) using liquefied natural gas (LNG) as heat sink to recover the cryogenic energy of LNG. Based on the mathematical model, a parametric analysis is conducted to examine the effects of some key thermodynamic parameters on the system performance. The results indicate that the overall electrical efficiency of 67% can be easily achieved for the current system, which can be further improved with parametric optimization. An increase in fuel flow rate of SOFC can raise the net power output, but it has a negative effect on SOFC and overall electrical efficiency. The compressor pressure ratio contributes to an increase in SOFC and overall electrical efficiency, which are contrary to the effects of air flow rate and steam-to-carbon ratio. Under the given conditions, compared with the Kalina sub-system, the ORC sub-system produces 12.6% more power output by utilizing the cryogenic energy of LNG with simple configuration. 相似文献
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In this paper we report the results of our modelling studies on two-phase forced convection in microchannels using water as the fluid medium. The study incorporates the effects of fluid flow rate, power input and channel geometry on the flow resistance and heat transfer from these microchannels. Two separate numerical models have been developed assuming homogeneous and annular flow boiling. Traditional assumptions like negligible single-phase pressure drop or fixed inlet pressure have been relaxed in the models making analysis more complex. The governing equations have been solved from the grass-root level to predict the boiling front, pressure drop and thermal resistance as functions of exit pressure and heat input. The results of both the models are compared to each other and with available experimental data. It is seen that the annular flow model typically predicts higher pressure drop compared to the homogeneous model. Finally, the model has also been extended to study the effects of non-uniform heat input along the flow direction. The results show that the non-uniform power map can have a very strong effect on the overall fluid dynamics and heat transfer. 相似文献
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Avdhesh Kr. Sharma 《Biomass & bioenergy》2011,35(1):421-428
When the objective is to generate motive or electric power via I.C. engine, the overall pressure drop through the suction gasification system in addition to gas quality has become a sensitive issue. This work, therefore, presents an experimental study on a suction gasifier (downdraft) arrangement operating on kiker wood or Acacia nilotica (L). Studies were conducted to investigate the influence of fluid flow rate on pressure drop through the gasifier system for ambient isothermal airflow and ignited mode, pumping power, and air-fuel ratio, gas composition and gasification efficiency. Results of pressure drop, temperature profile, gas composition or calorific value are found to be sensitive with fluid flow rate. Ignited gasifier gives much higher pressure drop when compared against newly charged gasifier bed with isothermal ambient airflow. Higher reaction temperatures in gasifier tends to enhance gasifier performance, while, overall pressure drop and thus pumping power through the system increases. Both ash accumulated gasifier bed and sand bed filters with tar laden quartz particles also show much higher pressure drops. 相似文献
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《International Journal of Hydrogen Energy》2022,47(77):33039-33057
The rational design of flow fields is of vital importance for the internal distribution uniformity and overall power output of solid oxide fuel cells (SOFCs). This study reports the design of discrete cylindrical landing flow fields for planar SOFCs to tackle the in-plane unevenness problems. The effect of key geometric parameters on the internal mass and current distribution and the overall power output of SOFCs has been investigated using three-dimensional (3D) multi-physics numerical simulations. It is found that the cylindrical landing flow fields significantly reduce the local variation of mass distribution and improve the uniformity of current distribution compared with the parallel landing flow fields. The overall output performance of the cell is improved by the cylindrical landing flow field (D2.0-S1.0) due to the synergetic effect of increased pressure drop, enhanced gas transport and reduced ohmic loss. The results of this study demonstrate the effective of the cylindrical landing flow fields for improving the distribution uniformity of planar SOFCs and provide theoretical insights for further development and optimization of the cylindrical landing flow fields for related applications. 相似文献
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建立了考虑压降的开式回热燃气轮机热电冷联产装置的有限时间热力学模型,导出了各个部件的相对压降和各个热流率与压气机进口相对压降的关系式,以第一定律效率、[火用]输出率、[火用]效率和利润率为目标,在无燃料消耗和装置尺寸约束下,通过数值计算发现分别存在最佳的压气机进口相对压降使[火用]输出率和利润率取得最优值,进一步优化压比,得到了最大[火用]输出率和利润率,分别存在最佳的供热温度使最大[火用]输出率和利润率取得双重最大值,以利润率为设计目标能够减小装置的尺寸.在燃料消耗和装置尺寸约束下,优化了压气机进口相对压降,得到了最优效率,同时各部件流通面积分配也得到了优化.回热能够增大装置的利润率和效率. 相似文献
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Optimizing the operation of a power plant with respect to the so-called “cold end” allows for a higher overall efficiency. Among other methods it also requires the proper adaptation of the mass flow rate of the cooling water. In this paper a pinch analysis with respect to heat and mass transfer has been applied to find the optimum mass flow rate for the cooling tower. 相似文献