Appearance of the two-way shape-memory effect in a nitinol spring subjected to temperature and deformation cycling

The properties of a cylindrical spiral spring of nitinol (shape-memory alloy) are studied. When this spring is used as a working element in a rotary martensitic engine, the appearance of the two-way shape-memory effect in it is shown to decrease the engine operation efficiency.     

液相斯特林机工质的热力学与热物理性质的计算

介绍了液相斯特林机用液相工质的性质。并以工质 RC31 8作为算例 ,介绍了液相工质的热力学性质和热物理性质的数值计算 ,计算结果与已有的实验结果吻合较好。该文也将是研究和开发低品位热源液相热声热机的重要参考。     

Dynamic properties in an endoreversible Curzon-Ahlborn engine using a van der Waals gas as working substance

In this work we analyze the stability of an endoreversible Curzon-Ahlborn engine, using a van der Waals gas as working substance and the corresponding efficiency for such an engine. From the local stability analysis we find that a critical point of an almost linear system is stable. After arbitrary small perturbation, the system state exponentially decays to a critical point with either of two characteristic relaxation times that are a function of the thermal conductance (α), heat capacity (C) and τ=T2/T1. The behavior of relaxation times and solution of the systems are shown qualitatively by sketching its phase portrait. Finally we discuss the local stability and steady state energetic properties of the endoreversible engine.     

Implementing Black Hole as Efficient Power Plant *

Treating the black hole molecules as working substance and considering its phase structure, we study the black hole heat engine by a charged anti-de Sitter black hole. In the reduced temperature-entropy chart, it is found that the work, heat, and efficiency of the engine are free of the black hole charge. Applying the Rankine cycle with or without a back pressure mechanism to the black hole heat engine, the compact formula for the efficiency is obtained. And the heat, work and efficiency are worked out. The result shows that the black hole engine working along the Rankine cycle with a back pressure mechanism has a higher efficiency. This provides a novel and efficient mechanism to produce the useful mechanical work, and such black hole heat engine may act as a possible energy source for the high energy astrophysical phenomena near the black hole.     

基于传递矩阵法的热声发动机频率设计计算

介绍利用传递矩阵法计算热声发动机的工作频率的思路和方法。理论分析表明该方法是切实可行的 ,和其他方法得到了相互的印证。利用该方法的计算结果和已发表的试验结果进行了对比分析。研究结果表明 ,相比已有的计算方法而言 ,传递矩阵法更加简单直观 ,方便于采用计算机编程计算复杂结构的热声系统的工作频率。     

气-液双作用行波热声发动机性能研究

本文提出了环形三部分对称结构的气液双作用行波热声发动机,该发动机采用U形谐振管并引入液体活塞。本文针对平均工作压力、加热器加热量以及液体活塞质量等不同运行参数对系统性能的影响进行了数值模拟。模拟结果表明,提高平均工作压力、增大加热器加热量有利于提升系统压力振幅;引入液体活塞1.13 kg时,系统谐振频率达到最小值17.48 Hz。     

预注冷质的空气涡轮火箭性能分析研究

提出了压气机进口预注冷质的空气涡轮火箭(MIPCC ATR)循环,拓展了ATR在高飞行马赫数下的工作能力。给出了基于工质组分的变比热ATR循环热力学建模方法和工质物性改变时对部件特性的修正方法,基于所推导的准无量纲关系式讨论了循环参数之间的相互作用及其对性能的影响。研究结果表明预注冷质不仅能有效拓宽ATR的工作包线,而且可以提高单位推力,所需付出的代价是比冲会有一定程度的降低。     

热声驱动器谐振频率影响因素分析

分析了结构参数、操作参数以及工质等因素对热声驱动器谐振频率的影响 ,并结合驻波型热声驱动器 ,给出了相应的计算结果和实验数据。     

The performance analysis of a micro-/nanoscaled quantum heat engine

A new model of micro-/nanoscaled heat engines consisting of two thin long tubes with the same length but different sizes of cross section, which are filled up with ideal quantum gases and operated between two heat reservoirs, is put forward. The working fluid of the heat engine cycle goes through four processes, which include two isothermal processes and two isobaric processes with constant longitudinal pressure. General expressions for the power output and efficiency of the cycle are derived, based on the thermodynamic properties of confined ideal quantum gases. The influence of the size effect on the power output and efficiency is discussed. The differences between the heat engines working with the ideal Bose gas and Fermi gas are revealed. The performance of the heat engines operating at weak gas degeneracy and high temperatures is further analyzed. The results obtained are more general and significant than those in the current literature.     

线性与非线性传热过程的Curzon-Ahlborn热机在任意功率时的效率

热机性能的优化是热力学领域的一个重要问题,而工质与热源之间的传热过程是热机工作时产生不可逆的主要来源.本文在引入功率增益和效率增益两个重要参数的基础上,基于一个简化的Curzon-Ahlborn热机模型并利用合比分比原理,给出了线性与非线性传热过程的热机在任意功率输出时的效率表达式,结合数值计算详细讨论了热机在任意功率输出时的特性.研究表明,参数ξ作为功率增益δP的函数存在两个分支:在第一分支上(不利情形),效率呈现出单调变化特征;在第二分支上(有利情形),效率随着的δP变化是非单调的且有最大值.随着传热指数的增加,热机的工作区域减小,这源于非线性传热过程包含热辐射所致.进一步发现功率-效率关系曲线存在权衡工作点,热机在该点附近工作能够实现最有效的热功转换.研究结果有助于深入理解具有不同传热过程热机的优化执行.     

A Critical Review on Physical Vapor Deposition Coatings Applied on Different Engine Components

Friction and wear in different engine components have crucial effects on the engine performance, combustion efficiency, oil consumption and lifetime of the internal combustion (IC) engine. Under certain loads, speeds, and temperatures, the metallic components of the IC engine, especially the piston and valve system suffer from a higher friction. Thin film coating is one of the novel techniques to reduce the frictional forces and improve the mechanical properties of engine components. Due to some versatile tribological properties, increasing attention has been paid to the physical vapor deposition (PVD) technology in the recent decade to deposit thin film coating on engine components. This article presents a comprehensive literature review on thin film coatings for IC engine components deposited by PVD technique. Issues related to tribological properties (wear and coefficient of friction) and mechanical properties (hardness and roughness) are also highlighted. Scientific improvements are presented in the light of literature. It is revealed that PVD coating is significantly effective on wear resistance, scuffling resistance, surface roughness, and friction of the components in IC engine. Laboratory test and data from actual service so far suggest that the plasma-activated electron beam evaporation coating is perhaps one of the best choices for smooth surface finishing with improved mechanical and tribological properties. However, there are still some problems in its practical usage. This compressive review paper presents the major shortcomings of PVD coatings on IC engine components and the possible solutions if any. Finally, a number of issues have been reported which need to be encountered for further studies.     

Maximum power output of a class of irreversible non-regeneration heat engines with a non-uniform working fluid and linear phenomenological heat transfer law

Maximum power output of a class of irreversible non-regeneration heat engines with non-uniform working fluid, in which heat transfers between the working fluid and the heat reservoirs obey the linear phenomenological heat transfer law [q ∝ Δ(T ⁻¹)], are studied in this paper. Optimal control theory is used to determine the upper bounds of power of the heat engine for the lumped-parameter model and the distributed-parameter model, respectively. The results show that the maximum power output of the heat engine in the distributed-parameter model is less than or equal to that in the lumped-parameter model, which could provide more realistic guidelines for real heat engines. Analytical solutions of the maximum power output are obtained for the irreversible heat engines working between constant temperature reservoirs. For the irreversible heat engine operating between variable temperature reservoirs, a numerical example for the lumped-parameter model is provided by numerical calculation. The effects of changes of reservoir’s temperature on the maximum power of the heat engine are analyzed. The obtained results are, in addition, compared with those obtained with Newtonian heat transfer law [q ∝ Δ(T)].     

Bound on Efficiency of Heat Engine from Uncertainty Relation Viewpoint

Quantum cycles in established heat engines can be modeled with various quantum systems as working substances. For example, a heat engine can be modeled with an infinite potential well as the working substance to determine the efficiency and work done. However, in this method, the relationship between the quantum observables and the physically measurable parameters—i.e., the efficiency and work done—is not well understood from the quantum mechanics approach. A detailed analysis is needed to link the thermodynamic variables (on which the efficiency and work done depends) with the uncertainty principle for better understanding. Here, we present the connection of the sum uncertainty relation of position and momentum operators with thermodynamic variables in the quantum heat engine model. We are able to determine the upper and lower bounds on the efficiency of the heat engine through the uncertainty relation.     

行波和驻波模式下热声振荡的临界温度梯度

热声机械作为一种能量转化装置。其效率于传统发动机还有较大差距。本文讨论了热声发动机在驻波和行波两种不同工作状态下,其声功率产生的临界温度梯度与流道尺寸和工作介质的关系,得出了两种模式下最佳的工作条件。结果表明;采用行波形式的热声发动机结构,可以有效降低临界温度梯度,提高热致声的效率,同时可以利用一些低品位来做为热声发动机的高温端。     

Combustion process in a spark ignition engine: dynamics and noise level estimation

We analyze the experimental time series of internal pressure in a four cylinder spark ignition engine. In our experiment, performed for different spark advance angles, apart from the usual cyclic changes of engine pressure we observed additional oscillations. These oscillations are with longer time scales ranging from one to several hundred engine cycles depending on engine working conditions. Based on the pressure time dependence we have calculated the heat released per combustion cycle. Using the time series of heat release to calculate the correlation coarse-grained entropy we estimated the noise level for internal combustion process. Our results show that for a larger spark advance angle the system is more deterministic.     

Performance analysis of a tunneling thermoelectric heat engine with nano-scaled quantum well

A numerical model of a nano-scaled thermoelectric heat engine with InP/InAs/InP trilayer quantum well (QW) is investigated. The expressions of those performance parameters, such as current, power output, and efficiency are expressed. By numerical calculation, the resonant tunneling behavior of electrons in the QW is described, which seems like a very good energy selective electron mechanism for the heat engine. After considering the radiation heat leakage, for fixed layer thicknesses of the QW, the optimum working regions of the heat engine with respect to the chemical potentials and the bias voltage are obtained numerically under the economic criterion. From these results, the power output can be increased by narrowing down the layer thicknesses. In addition, owing to the radiant heat leakage, the efficiency initially increases in the working regions and then decreases when the layer thicknesses increase gradually, from which one can obtain a maximum efficiency by optimizing layer thicknesses of QW. These results calculated here may provide a guide for the optimum designs of tunneling thermoelectric devices.     

关于热声压缩机原理的讨论

回顾了驻波、行波热声机械的发展历史 ,分析了行波与驻波热声压缩机的优缺点。介绍行波驻波混合型热声压缩机的工作原理及结构 ,指出了今后研究的重点和方向。     

内燃机车司机室吸附式空调器的实验研究

本系统是一种采用分子筛－水吸附式制冷原理、以内燃机排气的余热驱动的新型空调系统。制冷系统为单吸附器结构，并通过蓄冷器，实现向内燃机车司机室连续、稳定地供冷。本文阐述了内燃机车司机室吸附式空调系统的设计原理及部分实验研究结果。     

主成分分析在某型柴油机光谱数据分析中的应用

通过改变气缸套和活塞间隙,设计了6种工作状态,获得了某型6缸柴油机在每种工作状态下不同负荷时的润滑油样本共计69个,采用超谱M型原子发射光谱仪分析21种元素浓度。应用主成分分析法,分别以分析元素和润滑油样本为研究对象,基于权系数和主成分得分,对光谱数据进行了元素分类和样本分类。发现应用主成分分析法分析油液光谱数据能比较理想地对元素进行分类,该分类的3种主成分反映了5种类型的元素组合即磨损元素Fe,Cr,Cu,Al和Pb,含量较高的添加剂元素Na,Zn,P,Ca和Mg,含量较低的添加剂元素Ba和B,润滑油主成分元素C和H和干扰元素Ni,Ti,Mo,V和Ag等。不仅如此,主成分分析法对样本的分类较好地区分了来自柴油机不同的气缸套—活塞设计间隙的油样。研究表明应用主成分分析法分析润滑油光谱分析数据可揭示不同元素的来源、监测工况和诊断磨损故障。