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Truck platooning and related autonomous vehicle coordination concepts have been proposed as sustainable ways to increase profits and improve service quality. Recently the concept of truck caravanning, a hybrid truck platooning with only one truck driver required per platoon, has been proposed in the literature. This paper describes the research effort in developing a model that can estimate the cost savings of truck caravanning. The motivation of the proposed model is to investigate if substantial monetary savings exist to justify the initial capital investment (both in equipment and infrastructure) required for the implementation of the truck caravanning concept. A linear programming model is developed and used to evaluate different size networks. Results from numerical experiments indicate that a caravan size of four trucks or greater is needed for significant cost savings to be achieved and that driver compensation is the most critical factor dictating profitability.

As internal combustion engines are getting downsized and require lower mass flow rate, their cycle efficiency drops significantly. Such small engines with swept volume (~435 cc) are used in three wheelers in our country. Around 2,32,000 three wheelers are sold in Tamil Nadu alone, and thus the auto rickshaw is an ever-growing industry for public transport in India. The decrease in cycle efficiency hampers good performance and results in major pollutant formations. The naturally aspirated engines used in all the rickshaws consume more fuel, are bigger in size and give out more emissions. A novel wave rotor technology developed in the past few decades is a germane solution to the fuel efficiency and emissions conundrum. The Greaves single-cylinder 435 cc engine was modelled on SOLIDWORKS software and then simulated on Converge CFD software. The results were compared with experimental testing of the engine. With the simulation result validated for the engine, the engine was simulated with boosted air pressure of 2 bar. This boosted pressure value was obtained from previous experimentation done on Comprex. The simulation result obtained at boosted pressure showed significant increase in efficiency of the engine with peak pressure of 129.25 bar and reduction in CO emissions.

Design and testing of a wave-rotor constant-volume combustor achieved stable combustion at near-atmospheric inlet conditions and demonstrated the potential of pressure-gain combustion using a wave ...

This work presents implementation of numerical analysis and topology optimization techniques for redesigning traditional injection molding tools. Traditional injection molding tools have straight cooling channels, drilled into a solid body of the core and cavity. The cooling time constitutes a large portion of the total production cycle that needs to be reduced as much as possible in order to bring in a significant improvement in the overall business of injection molding industry. Incorporating conformal cooling channels in the traditional dies is a highly competent solution to lower the cooling time as well as improve the plastic part quality. In this paper, the thermal and mechanical behavior of cavity and core with conformal cooling channels are analyzed to find an optimum design for molding tools. The proposed design with conformal cooling channels provides a better alternative than traditional die designs with straight channels. This design is further optimized using thermo-mechanical topology optimization based on a multiscale approach for generating sound porous structures. The implemented topology optimization results in a light-weight yet highly effective die cavity and core. The reduction in weight achieved through the design of dies with porous structures is meant to facilitate the adoption of additive manufacturing for die making by the tooling industry.

Wave rotors are periodic-flow devices that provide dynamic pressure exchange and efficient energy transfer through internal pressure waves generated due to fast opening and closing of ports. Wave turbines are wave rotors with curved channels that can produce shaft work through change of angular momentum from inlet to exit. In the present work, conservation equations with averaging in the transverse directions are derived for wave turbines, and quasi-one-dimensional model for axial-channel non-steady flow is extended to account for blade curvature effects. The importance of inlet incidence is explained and the duct angle is optimized to minimize incidence loss for a particular boundary condition. Two different techniques are presented for estimating the work transfer between the gas and rotor due to flow turning, based on conservation of angular momentum and of energy. The use of two different methods to estimate the shaft work provides confidence in reporting of work output and confirms internal consistency of the model while it awaits experimental data for validation. The extended wave turbine model is used to simulate the flow in a three-port wave rotor. The work output is calculated for blades with varying curvature, including the straight axial channel as a reference case. The dimensional shaft work is reported for the idealized situation where all loss-generating mechanisms except flow incidence are absent, thus excluding leakage, heat transfer, friction, port opening time, and windage losses. The model developed in the current work can be used to determine the optimal wave turbine designs for experimental investment.

This paper describes best practice and effective techniques in international administration (IA) within the Globally Engaged University. The Globally Engaged University is one that continually promotes, communicates, initiates, controls, monitors, and evaluates international activity in at least one of its major academic units [5]. Emphasis is IA within engineering and technology higher education. Nonetheless, the description of best practice in IA is also applicable to various other academic disciplines at the Globally Engaged University. In describing best practice in IA, the paper adds the perspective of the authors' applied experience. The combined IA experience among the coauthors includes successful international programs in South and Southeast Asia, the European Union, and the USA. Three of the co-authors are senior administrators within one and the same university in the USA. Another co-author is a senior administrator at a university in Malaysia. Broadening the perspective yet further, another team member is an IA specialist at a Globally Engaged University in Poland. The authors compare and contrast techniques and organizational structure common to IA at three differing locations: USA, Malaysia, and Poland as a central member state of the European Union.

Natural gas substitution for diesel can result in significant reductions in pollutant emissions. In addition, with a high ignition temperature and relatively low reactivity, natural gas can enable promising approaches to combustion engine design. In particular, the combination of low-reactivity natural gas and high-reactivity diesel may allow for optimal operation as a reactivity-controlled compression ignition (RCCI) engine, which has potential for high efficiency and low emissions. In this computational study, a lean mixture of natural gas is ignited by direct injection of diesel fuel in part-load operating condition in a model of the heavy-duty CAT3401 diesel engine. A multi-dimensional simulation was performed using a finite-volume computational code for fuel spray and combustion processes in the Reynolds-averaged Navier-Stokes (RANS) framework. Adaptive mesh refinement (AMR) and multi-zone reaction modeling enables simulation in a reasonable time. The latter approach avoids expensive kinetic calculations in every computational cell, with considerable speedup. The model produces encouraging agreement between the simulation and experimental data. For reasonable accuracy and computation cost, a minimum cell size of 0.2 millimeters is suggested for the natural gas-diesel (NGD) dual-fuel engine. The results reveal that in part-load operating condition, much of the CH4, which is used as surrogate fuel for natural gas, cannot burn. The main goal of this research work is to assess the possibility to improve the performance of Caterpillar-3401 engine in NGD dual-fuel operation by in-cylinder modification strategies. The results reveal that among different strategies, double injection of diesel fuel with an early main injection can reduce the unburned hydrocarbon (UHC) emission significantly.

For some decades, efforts have been made to exploit nonsteady combustion and gas dynamic phenomenon. The theoretical potential of nonsteady-flow machines has led to the investigation of various oscillatory flow devices such as pulse detonation engines, wave rotors, pulse jets, and nonsteady ejectors. This paper aims to provide a progress review of past and current research in developing a particular combustion concept: the wave rotor combustor. This pressure-gain combustor appears to have considerable potential to enhance the performance and operating characteristics of gas turbine and jet engines. After attempts in the mid-twentieth century were thwarted by mechanical problems and technical challenges identified herein, recent successes in Switzerland and efforts in the United States benefited from design expertise developed with pressure-exchange wave rotors. The history, potential benefits, past setbacks, and existing challenges and obstacles in developing these nonsteady combustors are reviewed. This review focuses on recent efforts that seek to improve the performance and costs of future propulsion and power-generation systems.

A simultaneous consideration of the thermodynamic, economic and emission criteria regarding both CO 2 and NO x emissions of a distributed combined heating, cooling and power generation (tri-generation) system in an urban residential area in Beijing has been realized through thermo-economic optimization. Technologies such as gas turbine, internal combustion engine, absorption chiller and gas boiler are considered as options of the plant optimum configuration. System Net Present Value (NPV) is taken as the objective to be maximized. The presented mixed integer and non-linear programming (MINLP) problem is solved by a Genetic Algorithms (GAs) optimizer. The optimal plant configurations are found with the consideration of system configuration, design and operation under different economic and environmental legislation contexts.

Significant performance enhancement of microturbines is predicted by implementing various wave-rotor-topping cycles. Five different advantageous cases are considered for implementation of a four-port wave rotor into two given baseline engines. In these thermodynamic analyses, the compressor and turbine pressure ratios and the turbine inlet temperatures are varied, according to the anticipated design objectives of the cases. Advantages and disadvantages are discussed. Comparison between the theoretic performance of wave-rotor-topped and baseline engines shows a performance enhancement up to 34%. General design maps are generated for the small gas turbines, showing the design space and optima for baseline and topped engines. Also, the impact of ambient temperature on the performance of both baseline and topped engines is investigated. It is shown that the wave-rotor-topped engines are less prone to performance degradation under hot-weather conditions than the baseline engines.

Synovial joints are loaded by weight bearing, stretching, and fluid-driven shear. To simulate in vitro fluid-driven shear, we developed an "oscillating Couette flow mechanical shear loader". Oscillating Couette flow mimics relative motion of articular surfaces; hence, characterizing flow-induced shear by the loader enhances understanding of mechanotransduction in the joint tissue. Here, the analytical and computational models for an oscillating Couette flow were used to predict time-varying shear distribution on a plate surface, applying numerical simulation to evaluate the effects of finite plate dimension in a 2D flow. Shear stress on the plate was significantly different from that in simpler models (unbounded plates and viscous low-frequency flow). High-stress spots appeared near the leading and trailing edges of a moving plate, and a relatively uniform shear region was restricted to the interior area. Stress prediction in an example experimental geometry is presented, where the frequency and finite width effects are feasibly accounted.

Combustion and evaporation processes occurring in a closed chamber can result in signie cant pressurerise and direct work transfer. The pressure and volumetric changes that accompany such processes allow substantial work potential to be achieved in cyclic nonsteady devices, such as internal combustion engines and pulsed combustion or detonation engines. The ideal pressure gain or work production is a function of the prescribed ine ow and oute ow conditions, volumetric cone nement, e uid properties, and other parameters. The generalized thermodynamic limits of pressure gain and work production in such devices are investigated. Analytic and iterative methods are provided to evaluate cyclic combustion and evaporation processes for enhancing airbreathing combustion engine performance.

A wave rotor may be used as a pressure-gain combustor, effecting wave compression and expansion, and intermittent cone ned combustion, to enhance gas-turbine engine performance. It will be more compact than an equivalent pressure-exchange wave-rotor system, but will have similar thermodynamic and mechanical characteristics. Because the allowable turbine blade temperature limits overall fuel ‐air ratio to sube ammable values, premixed stratie cation techniques are necessary to burn hydrocarbon fuels in small engines with compressor discharge temperatures well below autoignition conditions. One-dimensional, nonsteady numerical simulations of stratie ed-charge combustion are performed using an eddy-diffusivity turbulence model and a simple reaction model incorporating a e ammability limit temperature. For good combustion efe ciency, a stratie cation strategy is developed that concentrates fuel at the leading and trailing edges of the inlet port. Rotor and exhaust temperature proe les and performance predictions are presented at three representative operating conditions of the engine: full design load, 40% load, and idle. Theresults indicate thatpeak local gas temperatures will causeexcessivetemperaturesintherotorhousingunlessadditionalcoolingmethodsareused. Therotortemperaturewillbeacceptable,but the pattern factor presented to the turbine may be of concern, depending on exhaust duct design and duct ‐rotor interaction.

Hot-jet ignition of a combustible mixture has application in internal combustion engines, detonation initiation, and wave rotor combustion. Numerical predictions are made for ignition of combustible mixtures using a traversing jet of chemically active gas at one end of a long constant-volume combustor (CVC) with an aspect ratio similar to a wave rotor channel. The CVC initially contains a stoichiometric mixture of ethylene or methane at atmospheric conditions. The traversing jet issues from a rotating prechamber that generates gaseous combustion products, assumed at chemical equilibrium for estimating major species. Turbulent combustion uses a hybrid eddy-breakup model with detailed finite-rate kinetics and a two-equation k-ω model. The confined jet is observed to behave initially as a wall jet and later as a wall-impinging jet. The jet evolution, vortex structure, and mixing behavior are significantly different for traversing jets, stationary centered jets, and near-wall jets. Pressure waves in the CVC chamber affect ignition through flame vorticity generation and compression. The jet and ignition behavior are compared with high-speed video images from a prior experiment. Production of unstable intermediate species like C2H4 and CH3 appears to depend significantly on the initial jet location while relatively stable species like OH are less sensitive.

More efficient and powerful gas turbine engines can be designed using constant-volume combustors that may involve ignition of a combustible mixture using a hot gas jet, subsequent flame and pressure-wave propagation, and their interactions. Accurate prediction of three-dimensional transient turbulent combustion is computationally challenging. To resolve propagating turbulent combustion, predict ignition, and track pressure waves accurately requires techniques to minimize the numerical cell count and kinetics calculation times. This study of shock-flame interaction (SFI) used detailed chemistry that includes low-temperature ignition reactions. Computational cells with similar temperatures and composition were grouped as ‘zones’ where kinetics are solved only once per zone per time step, using average values of species concentrations and thermodynamic properties for that zone. This avoids expensive kinetic calculations in every computational cell, with considerable speedup. A relatively coarser initial mesh was refined selectively and automatically, based on predicted velocity and temperature gradients, tracking propagating pressure waves and flames. The time step is variable, limited by the local speed of sound, to ensure accurate wave propagation. These techniques, previously validated for non-premixed, premixed and multiple-fuel turbulent combustion in industrial IC engines, are applied to study SFI during premixed combustion in a long constant-volume combustor.

A wave-rotor pressure-gain combustor (WRPGC) ideally provides constant-volume combustion and enables a gas turbine engine to operate on the Humphrey-Atkinson cycle. It exploits pressure (both compression and expansion) waves and confined propagating combustion to achieve pressure rise inside the combustor. This study first presents thermodynamic cycle analysis to illustrate the improvements of a gas turbine engine possible with a wave rotor combustor. Thereafter, non-steady reacting simulations are used to examine features and characteristics of a combustor rig that reproduces key features of a WRPGC. In the thermodynamic analysis, performance parameters such as thermal efficiency and specific power are estimated for different operating conditions (compressor pressure ratio and turbine inlet temperature). The performance of the WRPGC is compared with the conventional unrecuperated and recuperated engines that operates on the Brayton cycle. Fuel consumption may be reduced substantially with WRPGC introduction, while concomitantly boosting power. Simulations have been performed of the ignition of propane by a hot gas jet and subsequent turbulent flame propagation and shock-flame interaction.

Early drop out and poor retention rates are a major challenge to engineering education, which in many institutions have prompted a focus on improved first-year experiences. Retention and contributing learning challenges persists into the middle years, particularly when students confront the first engineering science courses in their major field. Students often perceive these courses as too abstract, intended to weed them out, and not meaningfully connected to their professional aspirations. A proven approach to improve student learning, self-efficacy, motivation, and retention is the use of active learning, including problems and projects [1–4]. Despite evidence of the benefits of active learning, engineering schools and faculty members have inadequate incentives to experiment with non-traditional approaches [5].

The application of problem-based learning (PBL) to undergraduate engineering education has emerged as an area of research interest over the past few decades, although it does not appear to be the dominant pedagogy for most engineering programs. A related form of active learning is project-enhanced learning (PEL), specifically designed to enhance but not replace traditional teaching methods in engineering science courses. The perceptions of instructors who attempt PEL were examined using extended-term mixed-method approaches, seeking to examine perceived benefits and barriers to PEL as an intervention for improved student learning. Instructors expressed satisfaction with improved student motivation, interaction, and socialization, which may help with student success and retention in engineering. Instructors also expressed concern about losing focus on the challenging analytical course topics, but were able to achieve appropriate balance by designing project tasks to align well with the topics and limiting non-aligned project activity.

Renewed interest in pressure gain combustion applied as a replacement of conventional combustors within gas turbine engines creates the potential for greatly increased capability engines in the marine power market segment. A limited analysis has been conducted to estimate the degree of improvements possible in engine thermal efficiency and specific work for a type of wave rotor device utilizing these principles. The analysis considers a realistic level of component losses. The features of this innovative technology are compared with those of more common incremental improvement types of technology for the purpose of assessing potentials for initial market entry within the marine gas turbine market. Both recuperation and non-recuperation cycles are analyzed. Specific fuel consumption improvements in excess of 35% over those of a Brayton cycle are indicated. The technology exhibits the greatest percentage potential in improving efficiency for engines utilizing relatively low or moderate mechanical compression pressure ratios. Specific work increases are indicated to be of an equally dramatic magnitude. The advantages of the pressure gain combustion approach are reviewed as well as its technology development status.

A procedure to design a preliminary wave rotor cycle for any application is presented. To complete a cycle with heat addition there are two separate—but related—design steps that must be performed. Selection of a wave configuration determines the allowable amount of heat added in any case, and the ensuing wave pattern requires associated pressure discharge conditions to allow the process to be made cyclic. This procedure, when applied, gives a first estimate of the cycle performance and the necessary information for proceeding to the next step in the design process, namely, the application of a characteristic-based or other appropriate detailed onedimensional wave calculation that locates more precisely the proper porting around the periphery of the wave rotor. Examples of the design procedure are given to demonstrate its utility and generality. These examples also illustrate the large gains in performance that might be realized with the use of wave rotor enhanced propulsion cycles.

A review of recent testing has been performed to assess the viability of a wave-rotorbased pressure-gain combustor. Tests accomplished in 2009 at the Purdue Zucrow lab on the Wave Rotor Combustor Rig (WRCR) provide basic information on the combustion processes achievable in a wave rotor passage. During a 30 day test period, 34 successful tests were completed, the longest of which was a 3-second firing was completed which totaled nearly 2,000 individual combustion events. Analysis of the results indicated stable combustor operation. The operability of the device is assessed regarding stability and combustion speeds. Agreement with predicted operation is examined. Potential for successful integration into a gas turbine as a replacement of a conventional combustor is addressed.

Ignitability and the ignition delay time of ethylene-air mixtures, ignited by a hot gas jet generated from combustion in a pre-chamber were investigated experimentally. The jet enters one end of a long combustion chamber, consistent with seeking a viable igniter method for wave rotor combustors. A numerical simulation of jet penetration and mixing in the main chamber provided guidance in testing and interpretation. The ignitability limits were established and ignition delay times were measured for a range of equivalence ratios. Chemical kinetics and mixing between the combustion torch jet and the combustible mixture both appear to be important in determining ignition delay times. This is in contrast with chemical ignition delay studies using shock-heated ignition techniques. Ethylene-air mixtures proved to be ignitable for initial premixed equivalence ratios ranging from 0.4 to 2.4, with the shortest ignition delay times of about one millisecond occurring for lean nearstoichiometric mixtures. The ethylene-air ratio of the combustion torch jet affected the ignition delay time in the main chamber combustible mixture, with the slightly rich prechamber mixtures providing the lowest delay times in igniting the main chamber ethyleneair mixtures.

High-fidelity unsteady, three-dimensional simulations were used to understand the mixing characteristics of gas from an injector that traverses the end of a narrow long chamber. Such a translating jet has applications in a Wave Rotor Constant Volume Combustor (WRCVC) for fueling and ignition. The simulations help visualize the jet in 3D injected through a hole and illuminate the possible mixing mechanisms responsible for gas mixing. Comparisons are made with previous 2D simulations, which represent injection through a slot. A method to quantify the amount of mixing between injected gas and the chamber gas is also proposed. The simulations discussed here do not model combustion and only analyzes gas mixing. To allow relative motion, a moderate clearance gap between a hot gas injector and multiple combustion chambers is assumed. The simulations indicate that pressure differences cause hot gas flow between chambers in the form of a ‘wall jet’ that precedes injector arrival. This hot gas tends to stay in the vicinity of the end wall, and may be a potential source of ignition, but only if an ignitable combustible mixture exists at that location. The 2D slot jet is seen to have higher penetration in the axial direction compared to the 3D hole jet for the same velocity, density and temperature boundary conditions at the injector inlet. As expected for injection through a hole, there are regions near the end wall that are bypassed by the jet and remain near chamber conditions, whereas the slot jet sweeps away all chamber gas near the wall.

Shear-dominated flows generated by compressible turbulent confined jets were simulated using two-equation turbulence models. A representative test problem was selected for which reliable experimental data was available for comparison. For validation of the improved models used for this study, a confined steady round turbulent jet interacting isothermally with co-flowing air was analyzed. The method was implemented in a widely used code using a pressure-based implicit solver. Three variations of two-equation models were considered: (i) a ‘high-Reynolds-number’ k-e equations with corrections for compressibility effects and non-linearity of the governing equations, (ii) standard k-e model with correction for round jets due to vortex stretching in three dimensions, and (iii) shear stress transport (SST) k-ω model.

The wave rotor combustor can significantly improve gas turbine engine performance by implementing constant-volume combustion. The periodically open and closed combustor complicates thermodynamic analysis, and key cycle parameters depend on complex gas dynamics. In this study, a consistent air-standard aerothermodynamic model with variable specific heat is established. An algebraic model of the dominant gas dynamics estimates fill fraction and internal wave compression for typical port designs, using a relevant flow Mach number to represent wave amplitudes of compression and expansion. Nonlinear equations for thermodynamic state variables are solved numerically by Newton-Raphson iteration. Performance measures and key operating conditions are predicted, and a quasi-one-dimensional computational model is used to evaluate the usefulness of the algebraic model.

A numerical method is developed with the capability to predict transient thermal boundary layer response under various flow and thermal conditions. The transient thermal boundary layer variation due to a moving compressible turbulent fluid of varying temperature was numerically studied on a two-dimensional semi-infinite flat plate. The compressible Reynolds-averaged boundary layer equations are transformed into incompressible form through the Dorodnitsyn–Howarth transformation and then solved with similarity transformations. Turbulence is modeled using a two-layer eddy viscosity model developed by Cebeci and Smith, and the turbulent Prandtl number formulation originally developed by Kays and Crawford. The governing differential equations are discretized with the Keller-box method. The numerical accuracy is validated through grid-independence studies and comparison with the steady state solution. In turbulent flow as in laminar, the transient heat transfer rates are very different from that obtained from quasi-steady analysis. It is found that the time scale for response of the turbulent boundary layer to far-field temperature changes is 40% less than for laminar flow, and the turbulent local Nusselt number is approximately 4 times that of laminar flow at the final steady state.

Gas flows of varying temperature occur in heat exchangers, nuclear reactors, non-steady flow devices, and combustion engines, among other applications with heat transfer processes that influence energy conversion efficiency. A general numerical method is developed for predicting the transient laminar thermal boundary layer response to arbitrarily prescribed changes in the bulk far-field fluid temperature. The method is tested for the step change of the far-field flow temperature of a two-dimensional semi-infinite flat plate with steady hydrodynamic boundary layer and constant wall temperature assumptions. Changes of the fluid-wall temperature difference in magnitude and sign are considered, including flow with no initial temperature difference and built-up thermal boundary layer. The governing differential equations for momentum and energy are solved based on the Keller-Box finite difference method. The accuracy of the solutions is verified through comparing with the steady state solution. Transient heat transfer coefficients are presented, which indicate that both magnitude and direction of heat transfer can be significantly different from quasi-steady models commonly used.

Design and evaluation of the wave rotor as a combustion device requires estimates of the performance as a function of operating conditions and gasdynamic processes occurring inside the rotor channels. An analytical model based on a combination of thermodynamic and gasdynamic approaches is established for assessing quantitatively the influence of various design parameters and operating conditions on the wave rotor performance. Performance results expressed by specific cycle work, thermal efficiency, and specific fuel consumption are calculated as functions of several design parameters. The results indicate that significant performance improvements are possible using combustion wave rotors, making this technology desirable for next generation of gas turbines and propulsion systems.

This study is aimed to make a systematic comparison between performance of pulse detonation engines (PDE) and detonative wave rotors, using a quasi-one dimensional numerical model. The model incorporates almost all major losses including viscous, heat transfer, port mixing, gradual opening and closing of channels losses. Two scenarios of (a) instantaneous detonation and (b) deflagration to detonation transition (DDT) for each engine are considered and flow field of these cases are compared with each other. To make flow field comparisons, the same rotor length, fuel distribution, inlet port size, and frequency are used for both engines. As expected, the outlet flow of the detonative wave rotor is shown to be more uniform than of the PDE, due to its fast rotation and large number of channels. This is more acceptable to turbine blades for gas turbine applications and may provide the combustor for new generation of aircraft engines. Higher pressure gain is produced in the detonative wave rotor configuration due to the mixture pre-compression by a hammer shock. Other advantages of the wave rotor approach are discussed.

This work is aimed to investigate the fundamental combustion and reignition process in semi-intermittent pressure-gain combustors for gas turbine applications. A combustion-torch ignition method is used to simulate reignition in one tube of a pressure-gain combustor by employing burned gas produced in a pre-chamber combustor. Numerical flow and combustion simulations are performed to understand and guide preliminary experimental results. The computational fluid dynamics code StarCD® is used to predict internal flow and combustion upon attempted ignition by a hot gas jet. This study provides improved understanding of the complex, sub-millisecond processes involved: transient supersonic jet mixing, ignition, highly turbulent flame propagation, and shock-flame interaction in near-wall region. The results are useful for successful design of rotary pressure gain combustors or internal combustion wave rotors under various operating conditions.Copyright © 2006 by ASME

Efficient cooling system designs are required for the modern diesel truck engine to meet new standards of increased efficiency and reduced emissions. Often, emissions reduction requires substantial cooled exhaust gas recirculation (EGR) to decrease peak combustion temperatures. This extra heat rejection imposes additional costs on the cooling system, and may not comply with application space constraints. Space and cost constraints require minimization of EGR cooler size and the risks from coolant boiling and exhaust condensation, while restraining growth in radiator frontal area, pumping power, and fan power. These objectives are usually contradictory, and a careful optimization is needed. This paper examines the effect of a coolant flow rate and peak temperature on these objectives, in parallel-flow and counter-flow arrangements of EGR cooler systems. It is concluded that these systems are likely to be inadequate, and alternative configurations may be necessary.Copyright © 2005 by ASME

Pressure gain combustion in a wave rotor approaching the thermodynamic ideal of constant volume combustion has been proposed to significantly enhance the performance of gas turbine engines. A computational and experimental program is currently being conducted to investigate the combustion process and performance of a wave rotor with detonative and near-detonative internal combustion. An innovative and flexible preliminary design of the test rig is presented to demonstrate the operation and performance of the system. A preliminary design method based on a sequence of computational models is used to design wave processes for testing in the rig and to define rig geometry and operating conditions. The operating cycle allows for propagation of the combustion front from the exit end of the combustion channel to the inlet end. This is similar to and motivated by the Constant Volume Combustor (CVC) concept that seeks to produce a relatively uniform set of outflow conditions in both spatial and time coordinates.Copyright © 2004 by ASME

The objective of this paper is to provide a succinct review of past and current research in developing wave rotor technology. This technology has shown unique capabilities to enhance the performance and operating characteristics of a variety of engines and machinery utilizing thermodynamic cycles. Although there have been numerous efforts in the past dealing with this novel concept, this technology is not yet widely used and barely known to engineers. Here, an attempt is made to summarize both the previously reported work in the literature and ongoing efforts around the world. The paper covers a wide range of wave rotor applications including the early attempts to use wave rotors, its successful commercialization as supercharges for car engines, research and development for gas turbine topping, and other developments. The review also pays close attention to more recent efforts: utilization of such devices in pressure-gain combustors, ultra-micro gas turbines, and water refrigeration systems, highlighting possible further efforts on this topic. Observations and lessons learnt from experimental studies, numerical simulations, analytical approaches, and other design and analysis tools are presented.Copyright © 2004 by ASME

In the last two decades, jet engines and gas turbines attempting constant-volume combustion without positive–displacement mechanisms have regained attention, mainly due to their theoretical high efficiency, potential low emissions, and compact design features. The idea can be traced back to experiments in the 1930’s and production of devices like the V1 missile motor and the Comprex® supercharger. Both for power generation and for aerospace applications, specific hardware and ingenious cycle designs are being developed to address known technological challenges. Different thermodynamic approaches and design methods are proposed to predict the performance potential of these periodic-unsteady wave machines. There have been experimental studies and successfully operated test-rigs that were sometimes shelved due to immediate economic concerns. These “lost” previous studies and experiences are worth reviewing amidst the increased attention to pulse detonation engine and wave-rotor applications proposed for gas turbine cycles by engine makers and government laboratories. In this review paper, our aim is to summarize the status and important efforts in this field. Recent research is highlighted by specific research groups worldwide attempting diverse applications. A compilation of promising applications is presented, to help focus efforts on future work needed.Copyright © 2003 by ASME

Prediction of shear stress induced by the fluid flow on knee joint cells is the main aim of this study. Oscillatory flow of a Newtonian synovial fluid is examined in two-dimensional joint geometries. The experimental model is a fluid driven shear loader test rig, which features a finite plate oscillating at 1Hz, that is 1mm over a stationary cell culture surface. Oscillating Couette flow in the thin gap is generated by the finite span plate. An incompressible two-dimensional transient and laminar CFD model is developed using the STAR-CD® code. The infinite oscillating plate Couette flow solutions (Stoke’s Second Problem with a finite gap) are reviewed and used in the grid sensitivity and validation tests of the computational finite oscillating plate model. The resulting flow features and vorticity convection are discussed and shear stress induced on the stationary plate due to an oscillating finite plate is compared with its infinite counterpart. As an extension, the effect of articular cartilage curvature is studied in a topologically equivalent model with and without menisci.Copyright © 2003 by ASME