bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Air Injection and Cavity Size Within a Circumferential Combustor to Increase G-Load and Residence Time
Authors: Cottle Andrew E. , Polanka Marc D. , Goss Larry P. , Goss Corey Z. 
Published: September 2016

Combustion at high G-loading offers the promise of higher flame speeds and shorter residence times. Ultra-Compact Combustors (UCC) make use of this phenomenon by injecting air and fuel into a circumferential cavity around the main core flow. Air is injected tangentially into the combustion cavity to induce bulk circumferential swirl. Swirl velocities in the cavity produce a centrifugal load on the flow that is typically expressed in terms of gravitational acceleration, or g-loading. The Air Force Institute of Technology (AFIT) has developed an experimental facility in which g-loads up to 2000 times the earth’s gravitational field (“2000 g’s”) can be established.
This paper investigates the flow within the combustion cavity to determine conditions that lead to the generation of higher g-loads and longer residence times. This is coupled with the desire to completely combust the fuel — ideally within the combustion cavity. These objectives have led to changes within the AFIT test setup to enable optical access into the primary combustion cavity. Particle Image Velocimetry (PIV), complemented by traditional high-speed video imagery, provided high-fidelity measurements of the velocity fields within the cavity. These experimental measurements were compared to a set of Computational Fluid Dynamics (CFD) solutions. Improved cavity air and fuel injection schemes were evaluated over a range of air flows and equivalence ratios. Increased combustion stability was attained by providing uniform distribution of air drivers. Lean cavity equivalence ratios at a high total airflow resulted in higher g-loads and complete combustion showing promise for utilizing the UCC as a main combustor.
Origins and Structure of Rotating Instability: Part 2 — Numerical Observations in a Transonic Axial Compressor Rotor
Authors: Wu Yanhui , An Guangyao , Chen Zhiyang , Liu Jun , Yang Guowei 
Published: September 2016

Rotating instability (RI) is an obvious unsteady flow phenomenon occurring in the tip region of compressors, which is potentially linked to tip clearance flow noise, blade vibration and rotating stall/surge. The existing investigations for RI indicate the origins of RI are closely related to unsteady flow behaviors in given blade passages in the rotating reference frame, which depend on the design specifics of axial machines. However, no efforts are made to set up a quantitative link between the time scale of unsteady behavior in a given passage and the characteristic parameters of RI, let alone to define the fluid dynamic processes/events which are causally linked with the RI inception. This is the motivation for the current investigations.
For the case shown in Part I, a quantitative link between the time scale of tip flow unsteadiness and the characteristic parameters of RI has been set up. The consistency between experimental and numerical results also demonstrates that multi-passage computations with the circumferential extent larger than the length scale of RI could shed light on the flow mechanisms relevant to the emergence of RI. In this part, systematic multi-passage simulations were thus laid out for a tip-critical transonic rotor, NASA Rotor 35, to identify the fluid dynamic processes for the inception of RI in presence of shock wave. It is found that the flow field becomes unsteady when the mass flow rate is below a critical value close to the stability limit. The flow unsteadiness in specific passages originates from the rotor tip region, but it is not synchronous with the occurrence of the circumferential travelling wave similar to RI as is the case in Part I. The origin of flow unsteadiness attributes to the periodic oscillation of a new vortex structure is termed as tip secondary vortex (TSV). The TSV is essentially a vortex segment arising from the spiral-type breakdown of TLV. The underlying flow mechanism for the inception of a rotating wave similar to RI is that the periodic oscillation of TSV is capable of inducing the flow blockage transfer against the rotor rotation direction. In conjunction with the investigation results reported in Part 1, a local inception criterion for RI is thus identified, which could be depicted as the initiation of the flow blockage transfer induced by the unsteady flow behavior in blade passages near tip.
Geometric Modeling and Analysis for Gooseneck
Authors: Tu Qiuye , Zhang Dongdong , Chen Jie , Cai Yuanhu 
Published: September 2016

Demands on the high by-pass ratio of modern civil engine, an increasing radial offset between the booster and the high pressure compressor highlights the importance of S-shaped gooseneck. A desirable balance between the length and the radial offset by optimizing inner-wall and outer-wall for gooseneck will save the length of low pressure rotor and improve the situation to deliver the flow through it.
This paper presented a geometric modeling method which adopted polynomial curves to construct inner-wall and section area distribution for goosenecks. With the given boundary dimensions of gooseneck, the location of inflection point served as a variable to control the inner-wall curve, and the peak value and its location served as the other two variables to control the area distribution curve. A series of 3-D models were built from the baseline gooseneck model in order to analyze the relationships between the geometric parameters and the aerodynamic performance.
The 3-D numerical simulation results indicated that the peak value of area distribution has the most important effects on the total pressure loss of gooseneck. An appropriate peak value of area distribution could be obtained by changing the normalized Mach number at peak point to weaken the flow separation near the outer-wall and after the struts. Inner-walls with large curvature near the entrance of gooseneck, and area distributions with an appropriate peak location, would improve the streamline of outer-wall and restrain the flow separation. Subsequently, the relationships between the geometric control variables and the total pressure loss were established.
Moreover, taking the constructional blocking effects of struts into account, a series of simplified 2-D flow paths were modeled and the relationships were reestablished. The 2-D results indicated that the simplified model could also reveal the flow field near the inner-wall address the correct peak value. But the optimum peak location and the inner-wall inflection point were not consistent with the 3-D results due to the geometric changes on the outer-wall. The equivalent method will be further improved in the future research.
Numerical Analysis and Design Optimization of a Low Pressure Cylinder Control Valve Block of a High-Power Steam Turbine
Authors: Arkhipova Liubov , Bogachev Anton , Tyukhtyaev Alexey 
Published: September 2016

A problem of energy losses reduction in the steam flows through different channels and flow paths of steam turbines is one of the issues of the day in turbo machinery.
In the report a comparative numerical analysis of two design options of control valve blocks and two different confuser pipes located upstream the control valves are presented. The aim of the research was minimization of energy losses in the control valve blocks and confuser pipes. The investigation consists of two parts.
In the first part a numerical study of steam flow through two alternative designs of the low pressure control valve block is discussed.
Another investigation presented in the report aims to selection of the optimum design of confuser pipes supplying steam to the control valve block. The cone angle and length of the pipe were varied in the study.
As a result of the work optimal design of confuser pipe and control valve block was chosen in respect to energy losses decrease.
Unified Thermodynamic Evaluation of Radical Aero Engine Cycles
Authors: Kaiser Sascha , Seitz Arne , Vratny Patrick , Hornung Mirko 
Published: September 2016

The Joule-/Brayton thermodynamic cycle is the base cycle of all major contemporary aero engines. Over the decades, the achievement of further significant improvements has become progressively challenging, and the increase of efficiency approaches physical limitations. In order to meet the ambitious long-term emission reduction targets, the introduction of radical new propulsion system concepts is indispensable. Various cycles promising significant efficiency improvements over the conventional Joule-/Brayton-cycle are being examined by the engine community. However, as no clear favorite has emerged from these potential technical solutions, a transparent methodological approach for the consistent evaluation of the concepts is necessary.
Consistent thermodynamic description and performance metrics for three engine cycles are presented in this paper: The turbofan as reference and two radical engine cycles, namely the composite cycle and the cycle-integrated parallel hybrid. Laws for the estimation of component performance for large parametric variations are introduced. A method for the estimation of power plant system mass for the investigated engine cycles is proposed to evaluate fuel burn reduction. The studies substantiated that the turbofan improvement potential is saturating. The composite cycle engine offers a tremendous potential for fuel burn improvement of 24.5% over state of the art turbofan engines, which allows meeting the emission reduction targets in 2035. The cycle-integrated parallel hybrid engine improves the turbofan moderately with year 2035 technology, but is not capable of meeting the corresponding emission reduction targets on a short-to-medium range aircraft platform.
Generation of the Equations for the Profile Losses Calculation in Blade Row of Axial Turbines in Design Analysis
Authors: Baturin Oleg , Kolmakova Daria , Gorshkov Aleksey , Popov Grigorii 
Published: September 2016

The paper proposes a method for evaluating the reliability of models for estimating the energy losses in the blade rows of axial turbines, based on the statistical analysis of the experimental data deviation from the calculated. It was shown that these deviations are subject to the normal distribution law and can be described by mathematical expectations μΔξ and standard deviation σΔξ.
The values of profile losses were calculated by five well-known models for 170 different axial turbines cascades, representing the diversity of turbines used in aircraft gas turbine engines. The findings were compared with experimental data. Comparison results were subjected to statistical analysis. It was found that the best model to describe the profile losses in axial turbines is model that has been developed in Central Institute of Aviation Motors (Russia). It allows the calculation of profile losses deviating from the actual values of losses by −8±84% with a probability of 95%.
Taking into account the mentioned statistical criteria, a new equation was proposed based on the analysis of the profile losses nature and using mathematical optimization techniques. This equation makes possible to define the profile loss of axial turbine more accurate than the investigated models. It allows the calculation of profile loss values in the axial turbine that differ from the actual value by 10±61% with a probability of 95%. The proposed new equation takes into account more geometric and operational factors affecting the value of losses.
Modeling and Simulation of Common Core Gas Turbine Engine Variant Applications
Authors: Sands Jonathan S. , Karl Alexander H. , Mavris Dimitri N. 
Published: September 2016

The development of a clean sheet gas turbine engine program can be a multi-billion dollar undertaking. The decision to take on such a program can place the company at great risk. In order to distribute this capital risk among a large quantity of products, the engine core should be utilized across a family of products. However, common core engine variant designs must also achieve performance levels that are competitive and economically viable options for likely customers.
Common engine core design decisions should be made with knowledge of how a candidate core definition will impact initial and future product applications. Implications must be drawn to estimate the impacts on performance, weight, and cost when employing a single core definition across a variety of likely product applications. This introduces an immense computational challenge. If commonality were enforced via post processing of simulation data, a large portion of the design space would not represent common core applications, making the associated data useless to the designer. Therefore, engine commonality should be implicitly imposed across the various product applications being considered. To further reduce the computational burden of simulating multiple applications, design space exploration of the core and corresponding variant applications must also be done in an efficient manner.
This research aims to develop and demonstrate a computationally efficient method for modeling and simulating a variety of common core engine variant applications simultaneously. The modeling approach to enforce commonality will first be shown. Additionally, the method will be shown to enable design space exploration of multiple common core engine applications simultaneously. Through the use of surrogate models, the relationship between a common engine core definition and corresponding variant application will be captured in mathematical form. This mathematical relationship will then be duplicated for each product application, tying all applications to a single baseline engine core definition. The approach allows core design implications to be drawn instantaneously to each product application considered.
After establishing the unique modeling and simulation approach, the method will be demonstrated for a multiple application common core design problem. The process will be used to arrive at an engine core definition that can be employed across multiple high bypass turbofan applications. In order to enumerate the amount of compromise made by employing a single baseline core definition across multiple applications, each resultant common core variant design will be compared to corresponding clean sheet designs selected for each individual application. The knowledge gained from this modeling and simulation approach allows the designer to make performance, weight, and cost trades efficiently across a family of products earlier in the development process.
Aerodynamic Turbine Design for an Oxy-Fuel Combined Cycle
Authors: Dahlquist Adrian , Genrup Magnus 
Published: September 2016

The oxy-fuel combined cycle (OCC) is one of several carbon capture and sequestration (CCS) technologies being developed to reduce CO2 emissions from thermal power plants. The OCC consists of a semi-closed topping Bryton cycle, and a traditional bottoming Rankine cycle. The topping cycle operates with a working medium mixture of mainly CO2 and H2O. This CO2-rich working fluid has significantly different gas properties compared to a conventional open gas turbine cycle, which thereby affects the aerodynamic turbine design for the gas turbine units. The aerodynamic turbine design for oxy-fuel gas turbines is an unexplored research field. The topic of this study was therefore to investigate the aerodynamic turbine design of turbines operating with a CO2-rich working fluid. The investigation was performed through a typical turbine aero-design loop, which covered the 1D mid-span, 2D through-flow, 3D blade profiling design and the steady-state 3D analysis. The design was performed through the use of conventional design methods and criteria in order to investigate if any significant departures from conventional turbine design methods were required.
The survey revealed some minor deviations in design considerations, yet it showed that the design is feasible with today’s state-of-the-art technology by using conventional design practice and methods.
The performance of the oxy-fuel combined cycle was revised based on the performance figures from the components design. The expected total performance figures for the oxy-fuel combined cycle were calculated to be a net electrical power of 119.9 MW and a net thermal efficiency of 48.2%. These figures include the parasitic consumption for the oxygen production required for the combustion and the CO2 compression of the CO2 bleed stream.
Installation and Performance Analysis of 125 kW Organic Rankine Cycle for Stationary Fuel Cell Power Plant
Authors: Huh Kwanghak , Mirmobin Parsa , Imani Shamim 
Published: September 2016

Installation and performance analysis of Thermapower™ 125MT Organic Rankine Cycle (ORC) System for recovery of waste heat from an existing Molten Carbonate Fuel Cell (MCFC) plant are presented. Over the last three years, about 100 MWe of new FC stationary power plants are in operation in Korea and more FC stationary power plants are on order and planned. The success of these fuel cell plants is their capability to supply both electricity and heat to customers. In order to promote renewable energy in Korea, the Korean Government is enforcing large power plants to supply electricity generated by renewable energy. The Korea Power Exchange (KPX) buys fuel cell generated electricity as renewable energy with higher price than other fossil fuel power plants [1].
Most of these FC plants supply electricity to power companies with their full capability, however valuable heat is wasted due to the limited demand, especially in summer season and off working hours or lack of heat pipe infrastructures. Due to the recent decrease in electricity price for renewable energy in Korea, the need for efficient utilization of waste heat is ever more demanding.
In this study, 125 kWe ORC system is installed to 11.2 MWe FC power plant to demonstrate cost saving benefits. This FC Power plant has 4 units of 2.8 MWe fuel cell in operation and has capacity of producing 6.0 ton/h of 167°C steam. In order to install an ORC system to existing FC plant, their Balance of Plant (BoP) has to be modified since only excess steam is allow to be utilized by the ORC system, after supplying steam to their prime customer. Furthermore, site has distinctly hot and cold seasons, thus affecting condensing conditions and therefore ORC performance. Design considerations to accommodate varying ambient conditions as well as steam flow rate variation are presented and discussed.
A Comparison of Actuator Disc Models for Axial Flow Fans in Large Air-Cooled Heat Exchangers
Authors: Wilkinson Michael B. , Louw Francois G. , van der Spuy Sybrand J. , von Backström Theodor W. 
Published: September 2016

The performance of large mechanical draft air-cooled heat exchangers is directly related to fan performance which is influenced by atmospheric wind conditions, as well as the plant layout. It is often necessary to numerically model the entire system, including fans, under a variety of operating conditions.
Full three-dimensional, numerical models of axial flow fans are computationally expensive to solve. Simplified models that accurately predict fan performance at a lesser expense are therefore required. One such simplified model is the actuator disk model (ADM). This model approximates the fan as a disk where the forces generated by the blades are calculated and translated into momentum sources. This model has been proven to give good results near and above the design flow rate of a fan, but not at low flow rates. In order to address this problem two modifications were proposed, namely the extended actuator disk model (EADM) and the reverse engineered empirical actuator disk model (REEADM).
The three models are presented and evaluated in this paper using ANSYS FLUENT. The models are simulated at different flow rates representing an axial flow fan test facility. The resulting performance results and velocity fields are compared to each other and to previously simulated three dimensional numerical results, indicating the accuracy of each method. The results show that the REEADM gives the best correlation with experimental performance results at design conditions (ϕ = 0.168) while the EADM gives the best correlation at low flow rates.
A comparison of the velocity profiles shows that none of the three models predict the radial velocity distribution at low flow rates correctly, however the correlation improves at flow rates above ϕ = 0.105. In general the upstream velocity profiles, where reversed flow occurs through the fan, are poorly predicted at low flow rates. At the flow rates above ϕ = 0.137 the correlation between the velocity profiles for the simplified modes and the three dimensional results is good.
Modeling of Compressor Drum Cavities With Radial Inflow
Authors: Amirante D. , Sun Z. , Chew J. W. , Hills N. J. , Atkins N. R. 
Published: September 2016

Reynolds-Averaged Navier-Stokes (RANS) computations have been conducted to investigate the flow and heat transfer between two co-rotating discs with an axial throughflow of cooling air and a radial bleed introduced from the shroud. The computational fluid dynamics (CFD) models have been coupled with a thermal model of the test rig, and the predicted metal temperature compared with the thermocouple data.
CFD solutions are shown to vary from a buoyancy driven regime to a forced convection regime, depending on the radial inflow rate prescribed at the shroud. At a high radial inflow rate, the computations show an excellent agreement with the measured temperatures through a transient rig condition. At a low radial inflow rate, the cavity flow is destabilized by the thermal stratification. Good qualitative agreement with the measurements is shown, although a significant over-prediction of disc temperatures is observed. This is associated with under prediction of the penetration of the axial throughflow into the cavity. The mismatch could be the result of strong sensitivity to the prescribed inlet conditions, in addition to possible shortcomings in the turbulence modeling.