燃气轮机装置定压加热循环的数学分析

本文用数学分析的方法对燃气轮机装置定压加热循环进行了分析,着重研究了各种参数对热效率和循环净功的影响,从而得出了一般热效率和循环净功表达式中难以直接得出的结论。     

非共沸工质与纯工质在ORC系统中的特性比较研究

工质的特性是影响ORC(有机朗肯循环)系统性能的重要因素之一。建立了65~100℃低温地热水有机朗肯循环发电系统数学模型,将R245fa分别与R601a和R227ea以不同比例混合作为ORC系统的工质,比较了非共沸混合物和纯物质两类工质对ORC系统循环净功、热效率和火用效率的影响。研究结果表明:无论是纯工质还是非共沸工质,系统的循环净功、热效率和火用效率都随着热源温度的升高而增大。工质在相变过程中是否存在温度滑移,是影响ORC系统性能的重要因素之一。在65~100℃的热源条件下,综合考虑3个评价指标,当R245fa配比为0.1~0.7时,R245fa/R601a混合物的循环净功、热效率和火用效率分别提升0.012~2.48 k W、0.005%~1.15%和0.08%~10.7%;当R245fa配比为0.5~0.9时,R245fa/R227ea混合物的循环净功、热效率和火用效率分别提升0.049~4.25 k W、0.057%~1.75%和0.21%~16.1%。     

内燃机循环熵产分析和性能评价

引入无因次熵产数Ns表示内燃机热力性能完善程度，对内燃机循环进行热力分析。研究了内燃机热力性能参数压缩比ε、定容增压比λ、定压预膨胀比p等对循环热效率ηm和无因次熵产数Ns的影响。研究表明压缩比ε、定容增压比λ增大，循环热效率ηm和无因次熵产数Ns相应增大，定压预膨胀比p增大，则无因次熵产数Ns增大且循环热效率ηm降低。根据内燃机常规性能参数范围，选定最高温度最高压力，依据性能分析经过一系列优化计算，得到考虑无因次熵产数Ns尽可能小的优化性能参数。     

对流热采油页岩过程低温余热ORC系统热力分析

为回收利用对流热采油页岩过程中产生的低温余热蒸汽,提出并设计有机朗肯循环(ORC)系统进行热力发电。在特定余热蒸汽参数条件下,基于R245fa循环工质,编制计算程序模拟分析了ORC系统变工况参数对该系统热效率及输出功率的影响规律。数值模拟结果表明:设定汽轮机背压为0.25MPa时,工质最高蒸发压力为2.566MPa,在此范围内,系统热效率随蒸发压力升高单调增加,增幅减缓;取蒸发器出口温度85℃时,对于不同的蒸发压力系统允许运行工质流量范围不同,在同一蒸发压力下,由于热源限制导致系统热效率并未随工质流量增加显著提高,但可得到更多输出净功;蒸发压力为1.5 MPa时,随余热排放温度的降低,系统输出净功显著提高;随汽轮机背压的降低,系统热效率得到明显改善,但汽轮机背压的降低增加了工质冷凝的困难,合适的背压值取0.2MPa。     

CO2与R41跨临界朗肯循环低温发电系统比较分析

本文以R41为工质的跨临界朗肯循环低温发电系统进行了热力性能分析,并与CO_2跨临界发电系统进行比较,结果表明:R41和CO_2系统均存在一个最优进口压力使得热效率在相同的膨胀机进口温度下达到最大值,且膨胀机进口温度越高,对应的最优压力也越大。同热效率一样,系统均存在一个最优进口压力使得净功在相同的膨胀机进口温度下达到最大值,且R41系统比CO_2系统所作的最大净功平均提高52.6%,最优进口压力平均降低41.6%,系统火用效率平均提高24.8%。     

内燃机混合加热(Dual)循环有限时间热力学分析

对内燃机混合加热循环的特性做了进一步的分析与研究,使得对该循环的分析结果与内燃机实际热力过程的不可逆性充分接近,对内燃机的设计和理论研究工作具有重要意义;并运用有限时间热力学的方法,对135柴油机Dual循环进行了有限时间特性分析,得出了应用该方法对内燃机缸内热力过程不可逆性进行研究具有重要实际意义的结论。     

内燃机烟气余热ORC系统热力学特性分析

本研究分析了ORC对内燃机烟气余热回收的节能潜力及关键参数影响规律。该研究采用理论模拟方法,基于某内燃机实际特性曲线,分析了负荷变化,对ICE-ORC联合循环系统整体输出功率及热效率的影响。模拟结果显示额定工况条件下,该系统方案的整体热效率较独立ICE系统提高3.3%,内燃机低负荷条件下可能出现露点温度的情况,存在腐蚀设备的隐患。上述研究表明,采用ORC对内燃机烟气余热能够进行有效回收,且节能潜力随着内燃机负载的增加而提高。     

内燃机有限时间内不可逆循环热力学分析

本文讨论了内燃机循环在逐步考虑各种主要不可逆因素后所构成的一系列新的热力学模型下有限时间热力学分析，重点寻找出在规定的模型下其循环最大输出功率与对应的热效率之间的关系，给出了有限时间热力学意义下内燃机循环新的性能界限，它们对实际内燃机性能的评估及改进有一定的指导意义。     

回热型SCO2循环基本性能分析与优化

考虑有限温差传热、不可逆压缩过程和不可逆膨胀过程等不可逆因素,应用有限时间热力学理论建立了变温热源条件下的回热型超临界二氧化碳布雷顿循环模型。首先,分析了工质质量流率、压比、透平效率和压缩机效率对循环净输出功率、热效率和循环最高温度的影响;然后,在总热导率一定的条件下分别以输出功率最大和热效率最大为目标,对加热器、冷却器和回热器热导率分配比进行优化。结果表明：回热型S-CO₂布雷顿循环功率-效率特性曲线呈过原点的扭叶型,存在相应的压比使得输出净功率与热效率分别达到最大;相比于初始设计参数计算的循环性能,优化后循环净输出功率可提高27.3%,最大比功可提高46.9%,最大热效率可提高17.78%。     

闭式注蒸汽燃气轮机循环热效率的估算方法

将实际循环在循环完善程度和设备完善程度方面与理论的卡诺循环进行对比,通过循环的特性参数估算出闭式注蒸汽燃气轮机循环的热效率,并在此基础上给出了中冷,再热和燃煤气的闭式注蒸汽循环热效率的估算公式,同时分析了循环系数和完善系数对循环热效率的影响。     

Finite‐time thermodynamic performance of a Dual cycle

Finite‐time thermodynamic analysis of an air‐standard internal‐combustion Dual cycle is performed in this paper. The relation between net work output and efficiency of the cycle is derived. The maximum net work output and the corresponding efficiency limit of the cycle with heat transfer considerations are also found. Detailed numerical examples are given. The results obtained herein provide a guidance to the performance evaluation and improvement for practical internal combustion engines. Copyright © 1999 John Wiley & Sons, Ltd.     

Performance analysis of open cycle gas turbines

In this study, the performance of ideal open cycle gas turbine system was examined based on its thermodynamic analysis. The effects of some parameters, such as compressor inlet temperature (CIT), pressure ratio (PR) and the turbine inlet temperature (TIT), on the performance parameters of open cycle gas turbine were discussed. The turbine net power output, the thermal efficiency and the fuel consumption of the turbine were taken as the performance parameters. The values of these parameters were calculated using some basic cycle equations and variables values of thermodynamic properties. Other variables such as lower heating value, combustion efficiency and isentropic efficiencies of compressor and turbine were assumed to be constant. The result showed that the net power output and the thermal efficiency increased by a decrease in the CIT and increase in the TIT and PR values. If it is aimed to have a high net power output and the thermal efficiency for the turbine, the CIT should be chosen as low as possible and the TIT should be chosen as high as possible. Copyright © 2008 John Wiley & Sons, Ltd.     

废热重整甲醇内燃机-涡轮复合循环

介绍了一种清洁、高效的废热甲醇重整气涡轮-内燃机复合动力循环,研究了甲醇操作压力、水醇比、压缩比及过量空气系数对循环热效率的影响,并与氢气机、甲醇机、汽油机进行了对比分析。     

闭式循环柴油机系统的仿真研究

本文基于内燃机热力循环理论，编制了内燃机工作过程仿真程序，针对4102柴油机进行了开式循环和闭式循环的稳态模拟。通过计算结果与试验数据的比较，验证了计算的正确性。并比较了开式循环和闭式循环的各项参数，给出工质中不同含量的二氧化碳对闭式循环柴油机的影响规律。     

Study on homogeneous charge compression ignition combustion in argon circulated closed cycle hydrogen engine

It is important to improve thermal efficiency and to reduce harmful exhaust gas emissions in internal combustion engines. A closed cycle engine system that uses a monatomic molecular gas as the working fluid can be expected to have high thermal efficiency due to the high specific heat ratio of the gas. Several studies have been reported on closed cycle engines with conventional spark ignition or compression ignition. This research newly proposes an argon circulated closed cycle homogeneous charge compression ignition (HCCI) engine system fueled with hydrogen. In this engine system, effects of in-cylinder gas initial temperature and residual water in recirculated gas on combustion characteristics were investigated. The results show that the system with argon circulation has the wider range of operable conditions and the higher thermal efficiency compared to the case with air as the working fluid.     

Unified cycle model of a class of internal combustion engines and their optimum performance characteristics

The unified cycle model of a class of internal combustion engines is presented, in which the influence of the multi-irreversibilities mainly resulting from the adiabatic processes, finite-time processes and heat leak loss through the cylinder wall on the performance of the cycle are taken into account. Based on the thermodynamic analysis method, the mathematical expressions of the power output and efficiency of the cycle are calculated and some important characteristic curves are given. The influence of the various design parameters such as the high-low pressure ratio, the high-low temperature ratio, the compression and expansion isentropic efficiencies etc. on the performance of the cycle is analyzed. The optimum criteria of some important parameters such as the power output, efficiency and pressure ratio are derived. The results obtained from this unified cycle model are very general and useful, from which the optimal performance of the Atkinson, Otto, Diesel, Dual and Miller heat engines and some new heat engines can be directly derived.     

Fluent在非常规内燃机设计中的应用

简单介绍典型非常规内燃机的工作原理及独特结构;计算方法的进步和计算机技术的快速发展促进了计算流体力学在内燃机研制中的应用,减少了实验工作量,降低了研究费用,缩短了研发周期,Fluent软件突破了内燃机专用软件中对内燃机结构的限制,提供了用户自定义函数这一用户接口,为非常规内燃机的瞬态数值仿真计算提供了平台。非常规内燃机为提升内燃机热效率提供了发展思路,在非常规内燃机开发中应用Fluent进行数值模拟可加快研发进程。     

Numerical analysis of two-stroke free piston engine operating on HCCI combustion

An opposed-piston hydraulic free piston engine operating with homogenous charge compression ignition (HCCI) combustion, has been proposed by State Key Laboratory of Engines as a means of significantly improving the IC engine’s cycle thermal efficiency and lowering exhaust emissions. Single and multi-zone Chemkin model with detailed chemical kinetics, and unique piston dynamics extracted from one dimensional gas dynamic model, have been used to analyze the combustion characteristics and engine performance. Intake heating, variable compression ratio and internal EGR are utilized to control the combustion phasing and duration in the cycle simulations, revealing the critical factors and possible limits of performance improvement relative to conventional crank engines. Furthermore, real engine effects such as heat transfer with air swirl, residual mass fraction, thermal stratification, and heat loss fraction between zones are considered in the sequential CFD/multi-zone method to approach the realistic engine performance at an acceptable knock level.     

液化天然气冷能回收发电的工艺流程模拟

根据勃雷登燃气动力循环和朗肯循环原理,提出一种液化天然气冷能回收发电的工艺流程,并利用ASPEN PLUS软件对该流程进行了模拟,获得了流程各物流的压力、温度、流量等状态参数,各热力过程的热功等过程参数,以及各循环热效率、总热效率等热力学性能参数,为建立高效的液化天然气冷能发电系统提供理论支持。     

Review and recent developments of laser ignition for internal combustion engines applications

Performance of future ignition system for internal combustion engines should be reliable and efficient to enhance and sustain combustion stability, since ignition not only initiates combustion but also influences subsequent combustion. Lean burn systems have been regarded as an advanced combustion approach that could improve thermal efficiency while reducing exhaust gas emissions. However, current engines cannot be operated sufficiently lean due to ignition related problems such as the sluggish flame initiation and propagation along with potential misfiring. A high exhaust gas recirculation engines also has similar potential for emissions improvement, but could also experience similar ignition problems, particularly at idle operation. Similarly, ignition is an important design factor in gas turbine and rocket combustor.Recently, non-conventional ignition techniques such as laser-induced ignition methods have become an attractive field of research in order to replace the conventional spark ignition systems. The fundamentals of conventional laser-induced spark ignition have been previously reviewed. Therefore, the objective of this article is to review progress on the use of such innovative techniques of laser-induced ignition including laser-induced cavity ignition and laser-induced multi-point ignition. In addition, emphasis is given to recent work to explore the feasibility of this interesting technology for practical applications concerning internal combustion engines.