Performance Prediction Program Research Articles

Weather Routing Benefit for Different Wind Propulsion Systems

_ Impact of weather routing on a post-panamax bulk carrier equipped with different wind propulsion systems was studied. The studied wind propulsion systems were rotor sails, wing sails, and suction wings and the studied route was a typical bulk carrier route between China and Brazil. A 4 degrees of freedom (4-DoF) performance prediction program was used to generate a performance model of the ship with different wind propulsion devices and the performance models were used in the voyage optimization. The voyage optimization simulations were carried out using historical weather data during the years 2015 to 2019 with one departure per week on both ways. It was found that there is a significant reduction in fuel consumption when weather routing is used on wind propulsion ships, but the magnitudes of the weather routing benefit vary from system to system depending on its versatility. Higher benefits from weather routing were found first for rotor sails, then for suction wings, and finally for wing sails.

One dimensional approach to predict the performance of high pressure multi-stage axial turbine considering air cooling and diffuser performance

This paper provides an improved 1D mid-span program to quickly grasp the off-design characteristic of modern axial turbines. The improvements are mainly focused on cooling, diffuser and the calculation of choke condition. Disk cooling and blade cooling air mixing are considered in detail. A 1D diffuser model that considers the effects of area change, heat transfer, and friction is added so that a realistic boundary condition at the turbine outlet can be obtained. A choke routine that enables the assessment of choked flow up to limit load conditions is introduced to avoid the shortcoming that the calculation method fails to converge near or at the initial choking mass flow rate. Flexible modules for losses, deviation, and mixing models are built-in to increase the accuracy and versatility of the program. This work is of great value because few programs take cooling and diffuser into account in such detail when calculating turbine performance in the form of maps. The salient issues presented here deal first with the construction of the turbine performance prediction program. The validation of the code is first performed on public data for a five-stage low pressure turbine (LPT). The results show that the efficiency relative errors with the experimental value is in the range of −(0.11%−1.64%), which is within acceptable limits. Then, the performance of GE PG9351FA transonic axial turbine is estimated using this program. This industrial axial turbine is predicted for the first time in a form of turbine performance maps in open literature and the obtained performance map is very useful for the simulation of gas turbine.

Asphalt mixture fatigue damage and failure predictions using the simplified viscoelastic continuum damage (S-VECD) model

Fatigue cracking is a primary asphalt pavement distress and various models have been developed to predict the fatigue life of asphalt mixtures using laboratory tests. One such model is the simplified viscoelastic continuum damage (S-VECD) model, which has been implemented in the pavement performance prediction program, FlexPAVETM. The S-VECD model test protocols (AASHTO TP 133 and AASHTO T 400) and data processing tool (FlexMATTM) are widely used around the world. Over the past three decades, this model has been continuously improved and refined. However, questions remain on the model’s ability to predict the material response when stress or strain are used as the model input. Also, different fitting procedures for the model calibration were found to affect the model’s prediction accuracy. In this study, analysis was conducted using data for four typical North Carolina mixes based on single replicate tests and multiple replicate tests to compare the model’s prediction accuracy based on stress versus strain as the model input and by considering fitting errors in the different calculations. The results show that using strain as the model input, which automatically incorporates portions of permanent strain, yields more accurate predictions compared to using stress as the input, regardless of the fitting algorithm. Additionally, in the analysis of individual test data, which is not affected by replicate specimen variability, the model’s predictions match the measured data well, as long as the fitting errors of the damage characteristic curve are controlled. When the data from replicate tests are analyzed together, although specimen variability compromises the S-VECD model’s prediction accuracy, failure can still be reasonably determined when strain is used as the model input.

A Simplified Protocol for Permanent Deformation Characterization of Asphalt Concrete

Abstract Permanent deformation (PD; or rutting) is one of the major distresses in flexible pavements. To predict PD in asphalt concrete, repeated and recovery load tests are usually conducted in the laboratory. The full-blown repeated load permanent deformation (RLPD) is time-consuming, limiting its use in research programs and developing correlations. Therefore, a quicker yet reliable procedure is needed for use in performance prediction programs. This paper presents a simplified and quicker procedure to obtain PD model parameters. It is illustrated using laboratory tests on field specimens. The procedure uses one specimen, compared with three specimens in the full-blown RLPD test, to be tested at two temperatures, the highest and lowest in the RLPD test, under the same conditions as in the RLPD test. The results of any intermediate temperature are obtained from the calibrated model. Two approaches are presented for analyzing the test results: the power equation in the AASHTOWare program, and the construction of a master curve. In the full-blown testing program with three specimens and three temperatures, the master curve approach fitted the results better than the power law. In the simplified procedure, the fitting of the two approaches is almost identical. Results obtained from tests conducted on six mixes show (1) testing one specimen at the highest temperature only and extrapolating the results overpredicts the material behavior at intermediate and low temperatures, and (2) the master curve from the simplified procedure compares very well with the one from the full-blown RLPD program.

Using mix design information for modelling of fundamental viscoelasticity of asphalt mixtures

Fundamental linear viscoelastic (LVE) characteristics of asphalt material is a critical component of pavement performance analysis and modelling. This study presents a practical and innovative approach to predict the complex modulus (E*) if terms of dynamic modulus (|E*|) and phase angle (δ) for asphalt mixtures by means of predicting the shape parameters of master curves using the advanced statistical analysis methods. Twenty distinct mixtures were evaluated and included in this study. The complex modulus test was performed on the mixtures and the |E*| and δ master curves were constructed. The statistical stepwise regression (SSR) model associated with F-test was employed to determine the significant factors and further develop the models for prediction of the shape parameters of these master curves. The prediction models developed only requires the general mixture design information that are readily available during any preliminary mixture design procedure, reducing the needs and efforts of preparing the samples and performing lab tests. The developed models show the good effectiveness and capability to predict the |E*| and δ values at any given frequency and temperature while incorporating the time–temperature superposition principle (TTSP). The developed models show the ability to be used for balanced mix design (BMD) as a predesign tool for evaluating mixtures’ cracking and rutting performance, and be incorporated into the advanced pavement performance simulation and prediction programs for predicting mixtures’ field performance in context of pavement structure, traffic and climatic conditions.

Influence of Kite Characteristics on Propulsive Power Applied to Ship Auxiliary Propulsion

A Design of Experiment method was applied combined with a performance prediction program to assess the influence of four design parameters on the propulsive capacity of kites used as auxiliary propulsion for merchant vessels. Those parameters are the lift coefficient, the lift to drag ratio or drag angle, the maximal load bearable by the kite and the ratio of the tether length on the square root of the kite area. These parameters are independent from the kite area and, therefore, they could be used with various kite ranges and types. The maximum wing load parameter is the one that shows the most influence on the propulsive force. Over 50% of the gains obtained through this study are directly attributable to it. Then the ratio of the tether length on the square root of the kite area comes as the second greatest influence factor for true wind angles above 70°. While the drag angle is more influential for the narrower angles. In fact, the most substantial gains are made upwind.

Case studies on performance prediction of radial inflow turbine under multiple rotor structures and organic fluids

Due to the lack of selection criteria for the ORC radial inflow turbine's loss models, and information about the models' limitations. This paper presents a comprehensive analysis for performance prediction of the ORC radial inflow turbine, and a novel turbine performance prediction program is proposed. This study can be divided into two parts, during the analysis part, 125 cases of CFD simulation were conducted under 5 rotor structures and R245fa as the working fluid. The performance of 6 loss models and their 18 combinations were compared. And in the examination part, another three organic fluids from different categories were chosen to exam the reliability of the proposed prediction program. The results show that loss model combinations E, O, and Q have a good performance in rotor loss prediction. Besides, Δβ4 has an important influence on prediction reliability and turbine performance, it should be lower than a certain value (about 40° in this paper) during the analysis process to get relatively reliable results under different rotor structures. The proposed program can realize an acceptable accuracy for turbine performance prediction under multiple organic fluids and rotor structures, with an efficiency deviation within ±5% and an output power relative error within ±10%.

Performance Prediction Program for Wind-Assisted Cargo Ships

Wind-Assisted Propulsion Systems (WAPS) can play a key role in achieving the IMO 2050 targets on reducing the total annual GHG emissions from international shipping by at least 50%. The present project deals with the development of a six degree of freedom (DoF) Performance Prediction Program (PPP) for wind-assisted cargo ships aimed at contributing knowledge on WAPS performance. It is a fast and easy tool, able to predict the performance of any commercial ship with three possible different WAPS installed: rotor sails, rigid wing sails and DynaRigs; with only the ship main particulars and general dimensions as input data. The tool is based on semi-empirical methods and a WAPS aerodynamic database created from published data on lift and drag coefficients, which can be interpolated with the aim to scale to different sizes and configurations. A model validation is carried out to evaluate its reliability. The results are compared with the real sailing data of a Long Range 2 (LR2) class wind-assisted tanker vessel, the Maersk Pelican. The study indicates that the PPP shows good agreement with the technology suppliers’ own modelling tool and reasonable agreement with the trends of the real sailing measurements. However, for downwind sailing conditions, the predictions are more conservative than the measured values. Lastly, results showing and comparing power savings for the three different WAPS are presented. Rotor Sails are found to be the most efficient WAPS studied with a much higher potential of driving force generation per square meter of projected sail area.

Performance prediction of transonic axial multistage compressor based on one-dimensional meanline method

This study proposes a 1D meanline program for the modeling of modern transonic axial multistage compressors. In this method, an improved blockage factor model is proposed. Work-done factor that varies with the compressor performance conditions is added in this program, and at the same time a notional blockage factor is kept. The coefficient of deviation angle model is tuned according to experimental data. In addition, two surge methods that originated from different sources are chosen to add in and compare with the new method called mass flow separation method. The salient issues presented here deal first with the construction of the compressor program. Three well-documented National Aerodynamics and Space Administration (NASA) axial transonic compressors are calculated, and the speedlines and aerodynamic parameters are compared with the experimental data to verify the reliability and robustness of the proposed method. Results show that consistent agreement can be obtained with such a performance prediction program. It was also apparent that the two common methods of surge prediction, which rely upon either stage or overall characteristic gradients, gave less agreement than the method called mass flow separation method.

Part 2: Simulation methodology and numerical uncertainty for RANS-CFD for the hydrodynamics of wind-assisted ships operating at leeway angles

A Reynolds-averaged Navier Stokes computational fluid dynamics (RANS-CFD) package will be one of the primary tools used during the development of a performance prediction program for wind-assisted commercial ships. This paper describes the simulation verification exercise, performed in support of the experimental validation presented in Part 1 of this two-part series describing the RANS-CFD method employed in this research. The predominance of large-scale separated flow structures in the wake of the sailing ship, an artefact of sideforce production necessary for sailing, points to a careful verification exercise and estimate for the numerical uncertainty to support the systematic investigation of wind-assisted ship hydromechanics and meshing guidelines within the available computer resources. Methods for CFD uncertainty quantification are defined and implemented for verification cases at leeway angles equal to 0ᵒ, 6ᵒ, and 9ᵒ. Analysis for four sets of grids with different meshing strategies and for varying time steps results in a grid definition and time step for simulation validation. Numerical uncertainty as adopted in Part 1 for validation is defined. Finally, the meshing strategy for full-scale simulation is described, as used for the production runs of the Delft Wind Assist Series.

횡단면선 위치 변화에 따른 여객선박의 선형 설계에 관한 연구

The purpose of this study is to investigate the interrelationship of how the ship's wave resistance performance changes with the change of the longitudinal position of the section line in the ship's lines, and to find a way to use it in the hull-form design. To this end, we developed a hull-form automatic change algorithm that can maintain the proper hull-form while moving the section lines in the longitudinal direction, and the computer program for a numerical analysis was developed to apply the developed algorithm. By applying the developed hull-form automatic change algorithm and the wave resistance performance prediction program, the numerical analysis package was constructed. The numerical analysis was carried out for the passenger ship. Numerical analyzes were carried out by moving the section lines of the passenger ship in the longitudinal direction, and the results were compared with each other. Based on the numerical results, we attempted to investigate the correlation between the section line movement and the wave resistance performance.

Part 1: Experimental validation of a RANS-CFD methodology for the hydrodynamics of wind-assisted ships operating at leeway angles

A Reynolds-averaged Navier Stokes computational fluid dynamics (RANS-CFD) package will be one of the primary tools used during the development of a performance prediction program for wind-assisted commercial ships. This paper is Part 1 of a two-part series describing the RANS-CFD method adopted for this study. The modelling challenge presented by large separated flow structures in the wake of a sailing ship points to a conscientious validation study. A validation data set, consisting of hydrodynamic forces acting on the ships sailing with a leeway angle, was collected at the Delft University of Technology towing tank facility, for bare-hull and appended cases. Appended cases were designed to represent a broad range of appendage typologies: Rudder, Bilge-keels, Skeg, and Barkeel. A validation statement is made for simulations for the entire bare-hull series and for appended geometries, excepting the Bilge-keel case. The simulation method is described in Part 2, including the assessment of the numerical uncertainty.

Fatigue Performance Prediction of Asphalt Pavements with FlexPAVETM, the S-VECD Model, and DR Failure Criterion

Reliable predictions of asphalt materials and pavement performance are important elements in mixture design, mechanistic-empirical pavement design, and performance-related specifications. This paper presents FlexPAVE™, a pavement performance prediction program. FlexPAVE™ is a three-dimensional finite element program that is capable of moving load analysis under realistic climatic conditions. It utilizes the simplified viscoelastic continuum damage (S-VECD) model to predict asphalt pavement fatigue life. This S-VECD model currently incorporates the so-called GR failure criterion to define the failure of asphalt mixtures. In this study, a new failure criterion for the S-VECD model, designated as the DR criterion, has been developed to remedy some of the shortcomings of the GR failure criterion. This DR criterion has been implemented successfully in FlexPAVETM. In this paper, FlexPAVETM is used to simulate the fatigue performance of field test sections. These test sections include various pavement structures, such as perpetual pavements and accelerated load facility test pavements in the United States, South Korea, and China, as well as various materials, such as warm-mix asphalt, reclaimed asphalt pavement, and mixtures with modified binders. The DR-based FlexPAVETM predictions have yielded good agreement with the field measurements and show more reasonable trends compared to predictions obtained using the GR failure criterion.

Investigation of heat-exchanger-sizing methods using genetic, pattern search, and simulated annealing algorithms and the effect of entropy generation

A numerical study on the heat exchanger design process has been conducted in order to propose a more effective method for the preliminary design of highly efficient and compact heat exchanger. The e-NTU based performance prediction program and the heat exchanger database having performance correlations of various fin-type heat exchanger were developed. Numerical characteristics of the genetic, pattern search, and simulated annealing algorithms for the heat exchanger sizing were compared in terms of the accuracy and the computational speed. The effect of margins in design requirements were examined through the size ranking and the response surface analysis. The usefulness of the entropy generation minimization was appraised by comparing to the case when the objective function was the volume of the heat exchanger.

Development of the Performance Prediction Program of an Air Brake System

Development of the Performance Prediction Program of an Air Brake System

A continuous and analytical modeling for kites as auxiliary propulsion devoted to merchant ships, including fuel saving estimation

A performance prediction program dedicated to merchant ships was developed to assess fuel saving abilities of a kite. The solving of the parameterization presented led to kite velocities and tethers tensions prediction continuously along a flight path within the wind window, including especially wind gradient and ship velocity. Both static and dynamic flight cases were considered regarding optimization strategy for kite tow efficiency. For dynamic flight case azimuth, elevation and orientation of the trajectory are continuously optimized in the present algorithm. Magnitude orders of towing forces induced by the kite were compared to those obtained in the literature. Especially in upwind conditions, which are the most frequent point of sail for fast vessels, results are dramatically improved. Finally, using a 320 m2 kite on a 50,000 dwt tanker, the fuel saving predicted is about 10% for a wind velocity of 9.77 m s−1 (Beaufort 5) and reaches more than 50% for a wind velocity of 15.68 m s−1 (Beaufort 7).

Design of an air-cooled condenser for engine coolant waste heat recovery

A novel design process for a parallel multi-flow type air-cooled condenser of a dual-loop waste heat recovery system with Rankine steam cycles, for improving the fuel efficiency of gasoline automobiles, has been investigated, focusing on reduction of the pressure drop inside the micro-tubes. The low temperature condenser plays a role in dissipating heat from the system, by sufficiently condensing the low temperature loop working fluid. However, the refrigerant has low enough evaporation temperature to recover the waste heat from engine coolant of about 100°C, but has small saturation enthalpy, so that excessive mass flow rate of the LT working fluid, e.g. over 150 g/s, causes an enormously large pressure drop of the working fluid, to maintain the heat dissipation performance of more than 20 kW. This paper has dealt with a scheme to design a low temperature condenser that has reduced the pressure drop, while ensuring the required thermal performance from the waste heat recovery system. The number of passes, arrangement of the tubes of each pass, and positions of the inlet and outlet pipes on the header are the most critical parameters affecting flow uniformity through all the tubes of the condenser. For the purpose of the performance predictions and parametric study for the LT condenser, we have developed a 1-dimensional userfriendly performance prediction program that feasibly calculates the phase change of the working fluid in the tubes. The proposed design process enables design engineers to find the optimum values of the numbers of passes and tubes of the multiflow condenser, for the reduction of the pressure drop sustaining the heat exchange performance. An example is presented through the proposed design process, and compared with an experiment.

폐열 회수 시스템용 공랭식 응축기의 압력 손실 저감 설계

A novel design process of a parallel multi-flow type air-cooled condenser of a dual-loop waste heat recovery system with Rankine steam cycles for improving the fuel efficiency of gasoline automobiles has been investigated focusing on reduction of the pressure drop inside the micro-tubes. The low temperature condenser plays a role to dissipate heat from the system by condensing the low temperature loop working fluid sufficiently. However, the refrigerant has low evaporation temperature enough to recover the waste from engine coolant of about <TEX>$100^{\circ}C$</TEX> but has small saturation enthalpy so that excessive mass flow rate of the LT working fluid, e.g., over 150 g/s, causes enormously large pressure drop of the working fluid to maintain the heat dissipation performance of more than 20 kW. This paper has dealt with the scheme to design the low temperature condenser that has reduced pressure drop while ensuring the required thermal performance. The number of pass, the arrangement of the tubes of each pass, and the positions of the inlet and outlet ports on the header are most critical parameters affecting the flow uniformity through all the tubes of the condenser. For the purpose of the performance predictions and the parametric study for the LT condenser, we have developed a 1-dimensional user-friendly performance prediction program that calculates feasibly the phase change of the working fluid in the tubes. An example is presented through the proposed design process and compared with an experiment.

트랙터의 견인성능 예측 프로그램 개발

, 2012In this study, we developed a simulation program for the prediction of tractive performance of a tractor, by applying a widely used empirical model for tractive performance prediction of single tire, Brixius. The tractive performance prediction program can readily predict and estimate tractive performance according to various soil conditions and different specifications of tractors. The program was developed with the considerations of tractor's specification-related parameters (e.g., weight, tire size, and wheelbase of the tractor), a soil parameter (i.e., cone index which represents the soil strength), and operating conditions of the tractor (e.g., theoretical speed and driving types such as 2WD and 4WD). Also, the program was designed to provide tractive performance prediction results of tractors such as gross traction, motion resistance, net traction, and tractive efficiency, in the form of not only numerical values but also graphical visualization. To evaluate the feasibility of the program, we input three different soil conditions (which have different cone indexes each other) and tractor operating conditions to the program and analyzed the tractive performance from each input condition. From the analysis, it can be concluded that the developed program can be effectively utilized to predict the tractive performance under various soil conditions and driving types of tractors with different specifications.

Development of a gas turbine performance analysis program and its application

A general-purpose performance prediction program, which can simulate various types of gas turbine such as simple, recuperative, and reheat cycle engines, has been developed. A stage-stacking method has been adopted for the compressor, and a stage-by-stage model including blade cooling has been used for the turbine. The combustor model has the capability of dealing with various types of gaseous fuels. The program has been validated through simulation of various commercial gas turbines. The simulated design performance has been in good agreement with reference data for all of the gas turbines. The average deviations of the predicted performance parameters (power output, thermal efficiency, and turbine exhaust temperature) were less than 0.5% in the design simulations. The accuracy of the simulation of off-design operation was also good. The maximum root mean square deviations of the predicted off-design performance parameters from the reference data were 0.22% and 0.44% for the two simple cycle engines, 0.22% for the recuperative cycle engine, and 0.21% for the reheat cycle engine. Both the design and off-design simulations confirmed that the component models and the program structure are quite reliable for the performance prediction of various types of gas turbine cycle over a wide range of operations.