Thermodynamic Engine Research Articles

A dynamometer for nature's engines

Muscle is an amazing natural thermodynamic engine that converts chemical energy into mechanical work. Each muscle twitch is ‘sparked’ by an electrically-released pulse of calcium ions, which trigger force-development and cell shortening, at the cost of energy and oxygen, and the dissipation of heat. Like other engines, muscle is inefficient at converting chemical energy to mechanical energy; at least 80% of the energy consumed by the muscle is released as heat. When we want to measure or enhance the performance of a human-made engine, such as an internal combustion engine, we typically attach it to a dynamometer—a device that can apply a controlled load to the engine, and measure its fuel consumption and work output. Imagine that we had a similar tool that allowed us to inspect nature's engine—muscle tissue—and thereby measure its energetic performance. Such a tool would allow us to better understand the muscle's work output and energy consumption, diagnose problems with the engine, tune its performance, and observe its response to changes in load, or to additives in its fuel. In this article, we report on our construction of a dynamometer for heart muscle.

The efficiency of quantum engines using the Pöschl – Teller like oscillator model

In this work, the quantum-mechanical properties of the strongly non-linear quantum oscillator described by the Pöschl-Teller [PT] model is examined. This model has a relation with two well-known models, the free particle [FP] in a box and the harmonic oscillator [HO], as described in our previous works [1–3]. Using the [PT] model, a quantum-mechanical analogue of the Joule-Brayton [JB] cycle and Otto cycle have been constructed through changes of both, the width of the well and its the quantum state. The efficiency of quantum engines based on the Pöschl-Teller-like potential is derived, which is analogous to classical thermodynamic engines.

Performance improvement of drysteam geothermal power plant by employing bottoming binary system

This study examines on how to improve the performance of dry-steam geothermal power plants in Kamojang by utilizing the binary system. The main data taken in this research is the temperature, pressure and mass flow collected from the plant’s operational data. It is then analyzed using the thermodynamic method and Engineering Equation Solver (EES). Results from the analysis showed that the net power output is about 48,865 kW. The first law efficiency increases from 16.45% to 19.44%, while the second law efficiency increases from 18.69% to 28.75%.

Review and Performance Evaluation of Fifty Alternative Liquid Fuels for Spark-Ignition Engines

The currently discussed alternative fuels for spark-ignition engines are numerous. A total of 50 different liquid fuel compounds were identified from the literature. Using a thermodynamic engine mo...

The other half of the principle of heat-work conversion cycles: The theorem, principle and core physical quantity of reversed cycles

Engineering thermodynamics mainly focuses on the principles and methods for the heat-work conversion and to improve heat-work conversion efficiency. In current literatures, discussions are mainly focused on the heat-work cycles, which converts heat to work. Besides, the core physical quantity of heat-work cycles is entropy, which presents the heat-work conversion ability of the system. As for reversed cycles, the discussions are not quite detailed, and most of them applied the theory for heat-work cycles directly on reversed cycles. However, its well known that heat cannot be fully converted to work in a reversible thermodynamic cycle, which leads an efficiency less than 1. For reversed cycles, the heat output from the cycle can be much more than the net work the cycle costs, which derives a coefficient of performance (COP) more than 1. This phenomenon implies the principles of heat-work conversion in ordinary heat-work cycles and reversed cycles are somehow different, and some problems are naturally drawn as follows: (1) Is the COP of the reversed Carnot cycle the maximum possible COP for all reversed cycles within two temperature limits? (2) Heat can be judged from its quality, i.e. its temperature, and does the mechanical work have its quality? To answer these questions, this work analyzed and discussed the theorem, principle, and core physical quantity of reversed thermodynamic cycles. First, the principle for ordinary thermodynamic cycles are briefly reviewed, including the Carnot theorem and its proof, and the derivation of the concept of entropy from the Clausius original approach. Second, current conclusions of reversed cycles are reviewed and the air compression refrigeration cycle is taken as an example. The analysis comparing two cycles within given temperature limits presented that for given two temperature limits, the COP of the reversed Carnot cycle is the minimum possible COP, which is different from current conclusions. The quality of volumetric work is then discussed, and a new reversed cycle named reversed p-V cycle is proposed, which operates between two given pressure limits. The analysis indicates that this cycle is the best reversed cycle operating between two given pressure limits. Based on these discussion, the theorem and principle for reversed cycles corresponding to the second law and the Carnots theorem are derived and proved using the Clausius approach. The performance of the newly proposed reversed p-V cycle is investigated and compared with the reversed Carnot cycle operating within the same temperature limits, and results present that the COP of the reversed p-V cycle is much higher than the COP of the reversed Carnot cycle within the same temperature limits. Finally, from the equation of an arbitrary reversed cycle, it can be seen that the volume has a similar physical interpretation in the reversed cycles to the entropy in thermodynamic cycles, and it can be named as the work-entropy. In summary, the reversed cycles are analyzed, and its theorem, principles and core physical quantity are investigated.

Experimental Teaching Mode of "Virtual and Reality Combination"—Engineering Thermodynamics as an Example

Under the circumstances that the certification process of engineering education is advancing rapidly, The Engineering Thermodynamics has become a compulsory course for certification majors. To improve the teaching effect of Engineering Thermodynamics, under the premise of giving full play to the advantages and complementarities of virtual experiment and entity experiment, a new experimental teaching mode which name is virtual and reality combination was studied in this paper. The implementation of the teaching effect is good.

Quantum engine based on many-body localization

Many-body-localized (MBL) systems do not thermalize under their intrinsic dynamics. The athermality of MBL, we propose, can be harnessed for thermodynamic tasks. We illustrate this ability by formulating an Otto engine cycle for a quantum many-body system. The system is ramped between a strongly localized MBL regime and a thermal (or weakly localized) regime. The difference between the energy-level correlations of MBL systems and of thermal systems enables mesoscale engines to run in parallel in the thermodynamic limit, enhances the engine's reliability, and suppresses worst-case trials. We estimate analytically and calculate numerically the engine's efficiency and per-cycle power. The efficiency mirrors the efficiency of the conventional thermodynamic Otto engine. The per-cycle power scales linearly with the system size and inverse-exponentially with a localization length. This work introduces a thermodynamic lens onto MBL, which, having been studied much recently, can now be considered for use in thermodynamic tasks.

Cosmological Solutions and Quantum Measurements in Conformal Vacuum Analogue

In a quantum measurement with post selection condition for transient short range observations with weak values as statistical ensembles in a time reversed scenario, vacuum energy fluctuations with entangled entropy and with its qubits of information can show transitions to action potentials for energy flows of an anomalous nature, so that superfluid state of vacuum as a quantum condensate system is relativistically transformed as an idealized cosmological fluid system with ultra high temperatures and vorticity, like in Blackhole analogous non singular metric of Einstein vacuum solutions of field equations. This can also explain quark gluon plasmic fluids in such metrics corresponding to quantum fluid vortex systems in a highly thermalised state. For short range and short lived observers, vacuum is measured as a quantum entangled system, with energy fluctuations in a strongly correlated state. This can have analogies with a spin coupled many body system of quantum particles corresponding to a fermionic superfluid as a scalar field with boson excitation and higher amplitude phonon modes. There is conformance with a system of strongly correlated quantum harmonic oscillators where the motion can be approximated to a Fourier Transform of KG equation as a generalised Klein Gordon one describing a quantized complex scalar field dynamics with a self interaction potential. The de Sitter vacuum invariant can be shown to correspond to a Black hole like metric in a non singular solution of field equations, with negative energy domains due to torsion tensor and Dirac Spinor minimal coupling. The geometrical vorticity with space time fluid state angular momentum of a large order can correspond to 2D quantum vortex flows in superfluids. The initial conditions of the hydrodynamic reveal negative energy and negative temperature domains prior to onset of quantum turbulence as the idealized fluid system expands and decays due to entropic effects, naturally. This can show time reversal behaviour with short lived local violations of the second law of thermodynamics, given an entropic lowering effect. However there is entanglement entropy with high mutual information due to strongly correlated state that might even imply negative conditional information. A situation thus locally exists for a time interval of a transient nature when quantum weak measurements by a nearby short range observer can manipulate quantum fluctuations like a supersystem in nature, having analogies to a quantum Maxwell demon translating high mutual information of strongly correlated quantum entangled states of conformal vacuum to action potentials for energy dissipation and work. Quantum mechanical indeterminism permits imposing post selection condition in such time reversed, scenario, so that fast thermalization can take place in a transition from negative temperature state to ultrahigh positive absolute hot conditions, as if a thermodynamic engine with higher than Carnot efficiencies is operating, locally and transiently.

Modeling Cosmic Expansion, and Possible Inflation, as a Thermodynamic Heat Engine

Abstract Assuming a closed universe with slight positive curvature, cosmic expansion can be modeled as a heat engine where we define the “system,” collectively, as those regions of space within the observable universe, which will later evolve into voids. We identify the “surroundings,” collectively, as those pockets of space that will eventually develop into matter-filled galaxies, clusters, superclusters, and filament walls. Using this model, we can find the energy needed for cosmic expansion using basic thermodynamic principles and show that cosmic expansion had as its origin a finite initial energy density, pressure, volume, and temperature. Inflation in the traditional sense, with the inflaton field, may also not be required. We also argue that homogeneities and inhomogeneities in the WMAP temperature profile are attributable to quantum mechanical fluctuations about a fixed background temperature in the initial isothermal expansion phase of the cycle, which we identify with inflation. Fluctuations in temperature can cause certain regions of space to lose heat while other regions will absorb that heat. The voids, being those regions that absorb the heat, will expand, thereby leaving slightly cooler temperatures for the surroundings, where matter will later congregate. Upon freeze-out, this could produce the observed WMAP signature with its associated inhomogeneity. Finally, using the uncertainty relation, we estimate that the temperature and time for formation of WMAP inhomogeneities occurred at roughly 3.02 × 1027 K and 2.54 × 10−35 s, respectively, after first initiation of volume expansion. This is in line with current estimates for the end of the inflationary epoch. The heat input in the inflationary phase is calculated as roughly Q = 1.81 × 1094 J (photons only); the collective void volume increases by a factor of only 5.65. The bubble voids in the observable universe increase in size from about 0.046 to 0.262 m3 within this inflationary period in our model.

Collaborative Projects with simulation assignments in mechanical engineering thermodynamics courses

In the undergraduate engineering classroom, some level of collaborative learning can be employed to enhance learning. Separately, enhancements in curriculum may include the use of computer technology to provide interactivity. The present study explores a new approach to facilitate learning of an engineering thermodynamics course and seeks to address the question: “What are the impacts of a themed Collaborative Project (CP) with a simulation component, on students and their understanding of thermodynamics?”. This approach was implemented into a sophomore-level thermodynamics course at a private university in the New England area of the United States. Over the duration of the semester, the clean water-themed CP required students to: solve thermodynamics problems linked to this theme; use thermodynamics fundamentals to check the results of clean water-related thermo-fluid simulations conducted using COMSOL Multiphysics® software; and ultimately, use thermodynamics to develop a device to clean water. This approach has the potential benefit not only of demonstrating various uses of thermodynamic analysis but also in preparing career-ready students who are better capable of strategically utilizing engineering software in tandem with their fundamental engineering backgrounds. Results presented include select student work, student perceptions as per surveys, and comparison of changes in average final exam grades as compared to previous courses. While students shared limited enthusiasm in utilizing the software, they expressed that they understood thermodynamics, and they performed better on final exam questions. This study follows up on a previous effort, which revealed various benefits for students who experienced such a CP.

Everyday chemical product design as platform for teaching transport phenomena

Transport phenomena is proposed as the second paradigm as a consequence of the inadequacy of the unit operations field for solving process and product engineering problems. The appearance of Bird’s transport phenomena textbook put transport phenomena as an engineering science along with thermodynamics for chemical engineers. Even though this field provides some important fundamentals to solve upcoming undergraduate problems, we have found that students constantly perceive this field as abstract and difficult to apply due to the fashion in which the problems are posed, the mathematics involved, and the three-dimensional view required to understand the phenomena. Chemical product design on the other hand represents the fourth paradigm which has permitted the evolution of the formation of the engineer to a more market-oriented design, so the student becomes more aware of the impact of his design. Here, we show how everyday life product design has facilitated the understanding of the fundamental concepts in transport phenomena for the student using active learning methodologies centered on evaluation of market needs.

Essential Engineering Thermodynamics: A Student's Guide

Engineering Thermodynamics is a core course for students majoring in Mechanical and Aerospace Engineering. Before taking this course, students usually have learned \textit{Engineering Mechanics}—Statics and Dynamics, and they are used to solving problems with calculus and differential equations. Unfortunately, these approaches do not apply for Thermodynamics. Instead, they have to rely on many data tables and graphs to solve problems. In addition, many concepts are hard to understand, such as entropy. Therefore, most students feel very frustrated while taking this course. The key concept in Engineering Thermodynamics is state-properties: If one knows two properties, the state can be determined, as well as the other four properties. Unlike most textbooks, the first two chapters of this book introduce thermodynamic properties and laws with the ideal gas model, where equations can be engaged. In this way, students can employ their familiar approaches, and thus can understand them much better. In order to help students understand entropy in depth, interpretation with statistical physics is introduced. Chapters 3 and 4 discuss control-mass and control-volume processes with general fluids, where the data tables are used to solve problems. Chapter 5 covers a few advanced topics, which can also help students understand the concepts in thermodynamics from a broader perspective.

Design and Application of a Multidisciplinary Predesign Process for Novel Engine Concepts

The purpose of this paper is to present a multidisciplinary predesign process and its application to three aero-engine models. First, a twin spool mixed flow turbofan engine model is created for validation purposes. The second and third engine models investigated comprise future engine concepts: a counter rotating open rotor (CROR) and an ultrahigh bypass turbofan. The turbofan used for validation is based on publicly available reference data from manufacturing and emission certification. At first, the identified interfaces and constraints of the entire predesign process are presented. An important factor of complexity in this highly iterative procedure is the intricate data flow, as well as the extensive amount of data transferred between all involved disciplines and among different fidelity levels applied within the design phases. To cope with the inherent complexity, data modeling techniques have been applied to explicitly determine required data structures of those complex systems. The resulting data model characterizing the components of a gas turbine and their relationships in the design process is presented in detail. Based on the data model, the entire engine predesign process is presented. Starting with the definition of a flight mission scenario and resulting top level engine requirements, thermodynamic engine performance models are developed. By means of these thermodynamic models, a detailed engine component predesign is conducted. The aerodynamic and structural design of the engine components are executed using a stepwise increase in level of detail and are continuously evaluated in context of the overall engine system.

The saturated and supercritical Stirling cycle thermodynamic heat engine cycle

On the assumption that experimentally validated tabulated thermodynamic properties of saturated fluids published by the National Institute of Standards and Technology are accurate, a theoretical thermodynamic cycle can be demonstrated that produces a net-negative entropy generation to the universe. The experimental data on the internal energy can also be used to obtain a simple, empirical equation for the change in internal energy of a real fluid undergoing isothermal expansion and compression. This demonstration provides experimental evidence to the theory that temperature-dependent intermolecular attractive forces can be an entropic force that can enhance the thermodynamic efficiency of a real-fluid macroscopic heat engine to exceed that of the Carnot efficiency.

DETONATION NANODIAMOND AS PROSPECTIVE COMPONENT OF COMPOSITE SOLID PROPELLANTS

In this articlethe the possibility of application of detonation nanodiamond (DND) as a prospective component of composite solid propellants (CSP) and additive approach to optimization of fuel compositions based on binary fuel compositions is considered. The introduction to the fuel composition of DND allows creating a metal-free CSP with increased energy-to-mass characteristics. Usage of the additive approach for calculations when creating new prospective compositions of CSP allows reducing significantly the volume of work to optimize the fuel compositions and to simplify the process of thermodynamic engineering.

Students’ Task Understanding during Engineering Problem Solving in an Introductory Thermodynamics Course

Understanding problems or tasks is a critical step in any problem-solving activity and the heart of self-regulated learning. When encountering a problem, students draw upon information available in the environment, along with knowledge, concepts, and perceptions derived from prior learning experiences, to interpret the demands of the task. Interpretation of tasks is, therefore, a key determinant of the goals set while learning, strategies selected to achieve those goals, and the criteria used to self-assess and evaluate outcomes. The purpose of this study is to better understand engineering students’ self-regulation in task interpretation processes while engaged in problem solving in an introductory engineering thermodynamics course. Two research questions guided the study: (1) What are the gaps, if any, between the instructor’s and students’ interpretation (explicit and implicit task features) of a problem-solving task?; and (2) How do students’ task interpretation (explicit and implicit) change after engaging in self-evaluation of their problem-solving processes? One hundred twelve (112) second year engineering undergraduates voluntarily participated in the study. Analysis of the data collected revealed a significant difference between the instructor’s and students’ task interpretation of the assigned problems. Furthermore, the analysis showed that students’ had a higher ability to identify the explicit parts of problem tasks than implicit ones. Students were able to grasp 63 to 77 percent and 39 to 49 percent, respectively, of the explicit and implicit information that was presented to them while engaged in problem-solving activities.

Modeling and operation of the power-to-gas system for renewables integration: a review

Power-to-Gas (P2G) plays an important role in enhancing large-scale renewable energy integration in power systems. As an emerging inter-disciplinary subject, P2G technology requires knowledge in electrochemistry, electrical engineering, thermodynamic engineering, chemical engineering and system engineering. Aiming at P2G modeling and operational problems concerning the research field of power systems and the energy internet, this paper briefly reviews the main technologies and application potentials of the P2G system, and makes systematic summaries of major progresses related to P2G's integration into the power grid in a bottom-top manner, including the modeling of high/room-temperature electrolysis cells, steady-state/dynamic optimization control of the P2G system, P2G's integrated model and operational strategies at the grid level. In the final part of this paper, suggestions are put forward on future research directions of P2G systems from the aspects of modeling and operational optimization.

Thermodynamic Considerations Related to Knock: Results From an Engine Cycle Simulation

The design and development of high efficiency spark-ignition engines continues to be limited by the consideration of knock. Although the topic of spark knock has been the subject of comprehensive research since the early 1900s, little has been reported on the coupling of the engine thermodynamics and knock. This work uses an engine cycle simulation together with a submodel for the knock phenomena to explore these connections. First, the autoignition characteristics as represented by a recent (2014) Arrhenius expression for the reaction time of the end gases are examined for a range of temperatures and pressures. In spite of the exponential dependence on temperature, pressure appears to dominate the ignition time for the conditions examined. Higher pressures (and higher temperatures) tend to enhance the potential for knock. Second, knock is determined as function of engine design and operating parameters. The trends are consistent with expectations, and the results provide a systematic presentation of knock occurrence. Engine parameters explored include compression ratio, engine speed, inlet pressure, start of combustion, heat transfer, and exhaust gas recirculation (EGR). Changes of cylinder pressures and temperatures of the unburned zone as engine parameters were varied are shown to be directly responsible for the changes of the knock characteristics.

Quantitative study on influence factors of power performance of variable valve timing (VVT) engines and correction of its governing equation

The influences of VVT on engine power performance were well summarized in previous studies from various aspects. However, most of the previous investigations were qualitative analysis and focused on the total effects of VVT without decoupling the influence factors. The primary cause is due to lack of an effective mathematic model to predict the IMEP of VVT engine. In this study, an approach to detect the VVT signals of engine was proposed, and the influence factors of power performance of VVT engines were quantitatively studied. The fundamental relationships among IMEP and its influencing parameters, i.e., intake density, intake VVT, RGF and thermal efficiency, were decoupled and the governing equation of IMEP was derived with the influences of VVT considered, the calculated results through which are in good agreement with tested data. Results indicate that, IMEP is directly proportional to effective cylinder volume at IVC timing and inversely proportional to RGF. The change rate of RGF influence coefficient is almost three times as that of RGF, and the combined effects of these parameters on IMEP equals the product of the coefficients of four influence factors. All these extended engine thermodynamics and provided theory basis for improving VVT engine's power performance.

Anisotropy in Thermal Recovery of Oil Shale—Part 1: Thermal Conductivity, Wave Velocity and Crack Propagation

In this paper, the evolution of thermal conductivity, wave velocity and microscopic crack propagation both parallel and perpendicular to the bedding plane in anisotropic rock oil shale were studied at temperatures ranging from room temperature to 600 °C. The results show that the thermal conductivity of the perpendicular to bedding direction (KPER) (PER: perpendicular to beeding direction), wave velocity of perpendicular to bedding diretion (VPER), thermal conduction coefficient of parallel to beeding direction (KPAR) and wave velocity of parallel to beeding direction (VPAR) (PAR: parallel to bedding direction) decreased with the increase in temperature, but the rates are different. KPER and VPER linearly decreased with increasing temperature from room temperature to 350 °C, with an obvious decrease at 400 °C corresponding to a large number of cracks generated along the bedding direction. KPER, VPER, KPAR and VPAR generally maintained fixed values from 500 °C to 600 °C. 400 °C has been identified as the threshold temperature for anisotropic evolution of oil shale thermal physics. In addition, the relationship between the thermal conductivity and wave velocity based on the anisotropy of oil shale was fitted using linear regression. The research in this paper can provide reference for the efficient thermal recovery of oil shale, thermal recovery of heavy oil reservoirs and the thermodynamic engineering in other sedimentary rocks.