bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Purge Flow Swirl on Hot Gas Ingestion Into Turbine Rim Cavities
Authors: Zlatinov M. B. , Tan C. S. , Little D. , Montgomery M.
Published: November 2013

Purge air, injected through seals in the hub of axial turbines, is necessary to prevent hot gas ingestion into endwall cavities, but generates losses by viscous interaction with the mainstream flow. Recent work has shown that for a given purge air mass flow rate, introducing swirl into the purge flow can reduce these losses. This paper investigates the effect of introducing such swirl on the ability of purge flow to prevent ingestion. In particular, it is observed that in the presence of the rotating external pressure non-uniformity due to a downstream blade row, swirled purge flow is much less effective in sealing a turbine disk rim cavity compared to non-swirled purge flow. This is reflected in higher purge air mass flow rates necessary to seal a given cavity, and that in turn diminishes the positive effect of pre-swirling purge flow in the first place. It is shown that this will occur whenever the circumferential pressure disturbance associated with the downstream rotating blades is the dominant driver for externally induced ingestion. It is reasoned that swirled purge flow moves with the rotating pressure non-uniformity and responds to it more readily than non-swirled purge flow, which sees the averaged effect of multiple blade passing events. A flow model based on this physical principle is developed, showing good agreement with computational results. The model yields an ingestion criterion with a parametric dependence on purge flow design parameters. The analysis is extended to an unsteady situation, whereby the effects of both stationary and rotating pressure non-uniformities, from vanes and blades respectively, are taken into account simultaneously. This unsteady flow model points to an optimal design space, in the context of minimizing purge flow losses while maintaining an appropriate margin with regard to hot gas ingestion.
Unsteady Numerical Analysis of a Whole Ring of Finger Seal With Grooves on Finger Pads
Authors: Zhang Hai , Zheng Qun , Yue Guoqiang , Deng Qingfeng
Published: November 2013

This paper presents a numerical investigation of lifting and sealing performance of a whole ring of finger seal with grooving pad structures. Different grooves on the bottom of lifting pad, such as one and two straight grooves, or two herringbone grooves with different gradients etc. are simulated. The rotor vibration is taken into account during the numerical computation. Computational results indicate that the complete ring model is more suitable than an individual finger model to simulate the fluid-solid interactions of the finger seal. Vibration of the rotor changes the deformation pattern of finger seal, and the seal deformation should adapt the clearance in a uniform way according to the rotor position. The grooving pad structures have effects on the leakage flows and the lifting force on the finger. Analytical data revealed the self-adaptive performance of finger seal to rotor vibration. This will be helpful to make the finger seal be of lower wear and smaller leakage in rotational sealing system.
Safety Issues With Reciprocating Compressor Design, Operating Practices and Maintenance
Authors: Upreti K. C. , Dev Amar , Prasad T. V. , Pundarikaksha B.
Published: November 2013

Reciprocating compressors are extensively used on high pressure and critical applications in all industries. These equipment needs through review of design of various components for a failsafe design. API-618 specifies various details about construction of various components, but due to OEM design by compressor vendor, proper review is not done or due to cost economic of equipment these are not given importance.

There are many examples when accident took place when these issues were ignored or correct assembly procedure for assembly of components is not followed and there were mistakes in design of piping system. In this paper, some of such cases are discussed and improvements are suggested for preventing any safety incidents. The issues described are designs of unloaders and venting system, unloader and vent piping, cylinder tap off connections, end clearance pocket unloaders, distance piece and crank case venting system, purge system for motors.

One of the risks with valve unloaders is the contamination of the instrument air with flammable gas specially on high pressure application. The instrument air may get contaminated with hydrocarbon if unloader leaking from stem and leak off gas tubing which is connected to flare may get interchanged with the instrument air connection. The same mistake if not noticed & compressor started, it may lead to the incident where compressor can show showed a strange vibration pattern, and instrument air header may get contaminated with hydrocarbon gases.

Another issue is crank case pressurisation due to improper venting system which can lead to pressurisation of crank case, failure of oil seals leading to flywheel end bearing failures. Further checking for finding reasons of crank case pressurisation, it is observed that excessive rod packing leaks results from incorrect leveling of compressor, distance and cylinders.

Motor purge system is one of the essential requirements for starting large reciprocating compressors; mistake in design/fabrication of vent system may create unsafe condition leading to explosion in motor.

All issues have been discussed in paper and various solutions and fail safe design have been suggested to improve safety and reliability. The studies also indicates that proper start up procedure and follow up of correct checklists during overhauling and start up can eliminate/ identify such mistakes.
Preventing Small Bore Piping/Tubing Failures in Reciprocating Compressors
Authors: Upreti K. C. , Banerjee Dwaipayan
Published: November 2013

API-618 Standard requires pulsation and vibration analysis of reciprocating compressors systems to prevent the system from damages. This analysis is carried out on major piping but often small bore connections are missed out in analysis and mistakes in site fabrication add up to this problem. These small bore connections on reciprocating compressor causes serious problems due to vibrations around reciprocating compressor.

This paper describes the issues of small-bore connection on Refinery CCR Platformer Net Gas Compressors where series of failures observed on small bore connection and associated tubing. Vibration/pulsation was the major contributing factor to various failures. Contributory Reasons for failure were analysed and reasons was found due to inadequate design of piping & tubing supports, Transmittal of vibration to platforms. It was found that small bore connections for PT, volume bottle drains, TI/TW were vibrating with high vibration velocity and amplitude. Max Vibration readings were found 705 micron. The dominant peak of vibration frequency is located at 15/17 X RPM. All vibrations were low frequency vibrations (< 300 Hz).

The problem was overcome by reducing SBC length and provision of better supports, reduced span for tube and pipe supports, replacement of tubes with higher schedule carbon steel pipes, shifting of instruments to less vibration areas such as basement of compressor house etc. Various modifications explained for reduction of vibration levels. Study compares condition prior to modification and new modification proposals. Modification improved vibration levels and no further failure reported.

Study indicates that more attention is warranted for small-bore attachments both in design stage and during operation. It is recommended to remove SBCs wherever possible, redesigning them so they are less susceptible to vibrations and relocating them to areas of less base motion.
N+3 and N+4 Generation Aeropropulsion Engine Combustors: Part 3 — Small Engines’ Emissions and Axial Staging Combustion Technology
Authors: Mongia Hukam C.
Published: November 2013

Comprehensive assessment of the small rich-dome engines was conducted leading to the following emissions correlations:

NOxEI LEC = 0.02991 × OPR1.9791

RMSE = 3.0%

NOxEI TALON II = 0.01666 × OPR2.1403

RMSE = 2.0%

NOxEI CFM TI = 0.06763 × OPR1.7458

RMSE = 2.1%

NOxEI CF34 = 0.0541 × OPR1.7917R2 = 0.9794

RMSE = 2.4%

NOxEI SM = 0.04782 × OPR1.8388

RMSE = 4.2%

NOxEI All = 0.03856 × OPR1.9058

RMSE = 3.9%

The best of the small engines’ gaseous emissions, albeit at lower takeoff pressure ratios, were shown to be very competitive with the best of medium and large size engines.

Axially-staged combustion with partially premixed jets in crossflow was identified as a promising concept to pursue for the (N+3) technology mixers.
Gas Turbine Combined Cycle Dynamic Simulation: A Physics Based Simple Approach
Authors: Gülen S. Can , Kim Kihyung
Published: November 2013

This paper describes a simplified physics-based method derived from fundamental relationships to accurately predict the dynamic response of the steam bottoming cycle of a combined cycle power plant to the changes in gas turbine exhaust temperature and flow rate. The method offers two advantages: (1) rapid calculation of various modes of combined cycle transient performance such as startup, shutdown and load ramps for conceptual design and optimization studies; (2) transparency of governing principles and solution methods for ease of use by a wider range of practitioners. Thus, the method facilitates better understanding and dissemination of said studies. All requisite formulas and methods described in the paper are readily amenable to implementation on a computational platform of the reader’s choice.
Heat Transfer Boundary Condition Waveforms on a Turbine Blade Leading Edge With Unsteady Film Cooling
Authors: Rutledge James L.
Published: November 2013

It is necessary to understand how film cooling both reduces the adiabatic wall temperature and influences the heat transfer coefficient in order to predict the net heat flux to a gas turbine hot gas path component. Although a great number of studies have considered steady film cooling flows, the influence of film cooling unsteadiness has only recently been considered. Unsteadiness in the freestream flow or the coolant flow can cause fluctuations in both the adiabatic effectiveness and heat transfer coefficient, the dynamics of which have been difficult to measure. In previous studies, only time averaged effects have been measured. The present study has determined time resolved adiabatic effectiveness and heat transfer coefficient waveforms using a novel inverse heat transfer methodology. Unsteady film cooling was examined on the leading edge region of a circular cylinder simulating the leading edge of a turbine blade. Unsteady interactions between h and η, were examined near a coolant hole located 21.5° downstream from the leading edge stagnation line, angled 20° to the surface and 90° to the streamwise direction. The coolant plume is shown to shift back and forth as the jet’s momentum fluctuates. Increasing freestream turbulence was found to both reduce η, and the amplitude of the η waveforms.
Computational Engineering Design for Micro-Scale Combustion Devices: A Thermally Improved Configuration
Authors: Saddawi Salwan David , Kipouros Timoleon , Savill Mark
Published: November 2013

A multi-objective design optimisation study has been carried out with the objectives to improve the overall efficiency of the device and to reduce the fuel consumption for the proposed micro-scale combustor design configuration. In a previous study we identified the topology of the combustion chamber that produced improved behaviour of the device in terms of the above design criteria. We now extend our design approach, and we propose a new configuration by the addition of a micro-cooling channel that will improve the thermal behaviour of the design as previously suggested in literature. Our initial numerical results revealed an improvement of 2.6% in the combustion efficiency when we applied the micro-cooling channel to an optimum design configuration we identified from our earlier multi-objective optimisation study, and under the same operating conditions.

The computational modelling of the combustion process is implemented in the commercial computational fluid dynamics package ANSYS-CFX using Finite Rate Chemistry and a single step hydrogen-air reaction. With this model we try to balance good accuracy of the combustion solution and at the same time practicality within the context of an optimisation process. The whole design system comprises also the ANSYS-ICEM CFD package for the automatic geometry and mesh generation and the Multi-Objective Tabu Search algorithm for the design space exploration. We model the design problem with 5 geometrical parameters and 3 operational parameters subject to 5 design constraints that secure practicality and feasibility of the new optimum design configurations. The final results demonstrate the reliability and efficiency of the developed computational design system and most importantly we assess the practicality and manufacturability of the revealed optimum design configurations of micro-combustor devices.
Performance Cycle Analysis for a Multi-Fuel Hybrid Engine
Authors: Yin Feijia , Rao Arvind G. , van Buijtenen Jos P.
Published: November 2013

Over the last decades, aviation has become a dominant way of travelling for human beings. However, the global warming and ozone depletion have become the major problems for humankind. Although aviation only counts for a minority of total pollutions, it shouldn’t be ignored any more. Therefore, the ACARE has set an ambitious objective for the year of 2050 to reduce CO2 emission by 75%, NOx emission by 90% and noise emission by 65% compared to these levels in 2000 [1].This reduction is to be achieved by combined improvements in aircraft, propulsion systems and air traffic management systems.

To achieve the ACARE goal, a novel multi-fuel hybrid engine concept was proposed for a multi-fuel blended wing body aircraft. A parametric analysis has been carried out in previous work, and the reference point was initially chosen at cruise. This paper continues to analyse the cycle performance of the hybrid engine. Firstly, the impacts of using a mixer was analysed at the reference point; secondly, a comparison was made between the hybrid engine and a conventional engine; furthermore, the hybrid engine performance was analysed at various operating altitudes and Mach number; additionally, the impacts of the inter-stage turbine burner were investigated. Finally, the impacts of fuel ratio on the engine performance was examined for a given thrust at take-off.
High-Precision Positioning of Laser Beams for Vibration Measurements
Authors: Marinescu Olguta , Epureanu Bogdan I.
Published: November 2013

Predicting the vibratory response of structures with complex geometry can be challenging especially when their properties (geometry and material properties) are not known accurately. These structures can suffer also from high modal density, which can result in small changes in structural properties creating large changes in the resonant response. To address this issue, structural properties could be accurately identified, or the structural response could be experimentally measured. Both these approaches require collecting measurements of higher order vibration modes which have complicated shape. Consequently, high-accuracy positioning of laser beams is necessary for vibrometers based on laser Doppler velocimetry. This paper presents a methodology to address this challenge. The architecture involves a single-point vibrometer, a motion controller, translating/rotating stages, and special application software for alignment and edge detection. A key novelty of this technology is that the beam of the vibrometer is used for both detecting the edges and for measuring the vibration. Using a motion controller, the system can automatically place/scan and measure the surface of the structure with a positioning resolution of 1 μm. Experimental results are provided to demonstrate the new technique.
Updraft Fixed Bed Gasification of Mesquite Fuel Using Air-Steam Mixture
Authors: Chen Wei , Thanapal Siva Sankar , Annamalai Kalyan , Ansley R. James , Mirik Mustafa
Published: November 2013

The mesquite woody species that dominate uncultivated lands in the south central Great Plains, U.S.A. (Texas, Oklahoma) may have the potential for bioenergy utilization. Gasification of woody biomass is an environmentally promising technology that provides an alternative to the use of fossil fuel. The objective of this study is to study enhancement of heat values of mesquite (Prosopis glandulosa) using an adiabatic fixed bed gasifier using air-steam as gasification medium and compare these values with those from other methods which include: air (N2:O2), CO2-O2 mixture, enriched air, blending biomass with high quality coal etc. The effects of steam/fuel ratio (S:F) and equivalence ratio (ER) on the gasification peak temperature (Tpeak), gas compositions, and gas higher heating value (HHV) were investigated. It is found that the Tpeak in air-steam gasification is lower than that of air gasification and the Tpeak decreased with the increase in the steam to fuel ratio (S:F). In addition, when S: F ratio increased from 0 to 0.45, the CO2 and H2 concentration increased while the CO percentage decreased. The mole composition of the end product gas contained: 8–19% CO, 4–15% H2, 1–3% CH4, and 10–18% CO2. The HHV of the mesquite gas was estimated to be in a range of 2800 kJ/Nm3 to 3800 kJ/Nm3. The HHV increased when the S: F increased from 0.15 to 0.3, and then it decreased when the S: F was increased from 0.3 to 0.45 and the highest value was obtained at S: F = 0.3 and ER = 2.7 (optimum). The HHV of the producer gas from air-steam gasification is found to be almost same as that produced from pure air gasification (2800–4000 kJ) and lower than that obtained from CO2:O2 mixture (79:21) gasification (4000 to 6000 kJ/Nm3). However, H2 rich producer gas was obtained with air steam mixture.
Flame Speed and Vapor Pressure of Biojet Fuel Blends
Authors: Munzar Jeffrey D. , Denman Bradley M. , Jiménez Rodrigo , Zia Ahmed , Bergthorson Jeffrey M.
Published: November 2013

An understanding of the fundamental combustion properties of alternative fuels is essential for their adoption as replacements for non-renewable sources. In this study, three different biojet fuel mixtures are directly compared to conventional Jet A-1 on the basis of laminar flame speed and vapor pressure. The biofuel is derived from camelina oil and hydrotreated to ensure consistent elemental composition with conventional aviation fuel, yielding a bioderived synthetic paraffinic kerosene (Bio-SPK). Two considered blends are biofuel and Jet A-1 mixtures, while the third is a 90% Bio-SPK mixture with 10% aromatic additives. Premixed flame speed measurements are conducted at an unburned temperature of 400K and atmospheric pressure using a jet-wall stagnation flame apparatus. Since the laminar flame speed cannot be studied experimentally, a strained (or reference) flame speed is used as the basis for the initial comparison. Only by using an appropriate surrogate fuel were the reference flame speed measurements extrapolated to zero flame strain, accomplished using a direct comparison of simulations to experiments. This method has been previously shown to yield results consistent with non-linear extrapolations. Vapor pressure measurements of the biojet blends are also made from 25 to 200°C using an isoteniscope. Finally, the biojet blends are compared to the Jet A-1 benchmark on the basis of laminar flame speed at different equivalence ratios, as well as on the basis of vapor pressure over a wide temperature range, and the suitability of a binary laminar flame speed surrogate for these biojet fuels is discussed.
Effects of Jet-to-Target Plate Distance and Reynolds Number on Jet Array Impingement Heat Transfer
Authors: Lee Junsik , Ren Zhong , Haegele Jacob , Potts Geoff , Jin Jae Sik , Ligrani Phil , Fox Michael D. , Moon Hee-Koo
Published: November 2013

Data which illustrate the effects of jet-to-target plate distance and Reynolds number on the heat transfer from an array of jets impinging on a flat plate are presented. Considered are Reynolds numbers Rej ranging from 8,200, to 52,000, with isentropic jet Mach numbers of approximately 0.1 to 0.2. Jet-to-target plate distances Z of 1.5D, 3.0D, 5.0D, and 8.0D are employed, where D is the impingement hole diameter. Steamwise and spanwise hole spacings are 8D. Local and spatially-averaged Nusselt numbers show strong dependence on the impingement jet Reynolds number for all situations examined. Experimental results also illustrate the dependence of local Nusselt numbers on normalized jet-to-target plate distance, especially for smaller values of this quantity. The observed variations are partially due to accumulating cross-flows produced as the jets advect downstream, as well as the interactions of the vortex structures which initially form around the jets, and then impact and interact as they advect away from stagnation points along the impingement target surface. The highest spatially-averaged Nusselt numbers are present for Z/D = 3.0 for Rej of 8,200, 20,900, and 30,000. When Rej = 52,000, spatially-averaged Nusselt numbers increase as Z/D decreases, with the highest value present at Z/D = 1.5.
Heat Transfer Enhancement for Gas Turbine Internal Cooling by Application of Double Swirl Cooling Chambers
Authors: Kusterer Karsten , Lin Gang , Bohn Dieter , Sugimoto Takao , Tanaka Ryozo , Kazari Masahide
Published: November 2013

Improvement of the gas turbine thermal efficiency can be achieved by reducing the cooling fluid amount in internal cooling channels with enhanced convective cooling. Nowadays the state of the art internal cooling technology for thermally high-loaded gas turbine blades consists of multiple serpentine-shaped cooling channels with angled ribs. Besides, huge effort is put on the development of more advanced internal cooling configurations with further internal heat transfer enhancements. Swirl chamber flow configurations, in which air is flowing through a pipe with a swirling motion generated by tangential jet inlet, have a potential for application as such advanced technology. This paper presents the validation of numerical results for a standard swirl chamber, which has been investigated experimentally in a reference publication. The numerical results obtained with application of the SST k-ω model show the best agreement with the experiment data in compare with other turbulence models. It has been found at the inlet region that the augmentation of the heat transfer is nearly seven times larger than the fully developed non-swirl flow. Within the further numerical study, another cooling configuration named Double Swirl Chambers (DSC) has been obtained and investigated. The numerical results are compared to the reference case. With the same boundary conditions and Reynolds number, the heat transfer coefficients are higher for the DSC configuration than for the reference configuration. In particular at the inlet region, the DSC configuration has even higher circumferentially averaged heat transfer enhancement in one section by approximately 41%. The globally-averaged heat transfer enhancement in DSC configuration is 34.5% higher than the value in the reference SC configuration. This paper presents the configuration of the DSC as an alternative internal cooling technology and explains its major physical phenomena, which are the reasons for the improvement of internal heat transfer.
Impact of Cooling Air Injection on the Combustion Stability of a Premixed Swirl Burner Near Lean Blowout
Authors: Marosky A. , Seidel V. , Sattelmayer T. , Magni F. , Geng W.
Published: November 2013

In most dry low NOx combustor designs of stationary gas turbines the front panel impingement cooling air is directly injected into the combustor primary zone. This air partially mixes with the swirling flow of premixed reactants from the burner and reduces the effective equivalence ratio in the flame. However, local unmixedness and the lean equivalence ratio are supposed to have a major impact on combustion performance. Overall goal of this investigation is to answer the question whether the cooling air injection into the primary combustor zone has a beneficial effect on combustion stability and NOx emissions or not. The flame stabilization of a typical swirl burner with and without front panel cooling air injection is studied in detail under atmospheric conditions close to the lean blowout limit (LBO) in a full scale single burner combustion test rig. Based on previous isothermal investigations a typical injection configuration is implemented for the combustion tests. Isothermal results of experimental studies in a water test rig adopting high speed planar laser-induced fluorescence (HSPLIF) reveal the spatial and temporal mixing characteristics for the experimental setup studied under atmospheric combustion. This paper focuses on the effects of cooling air injection on both flame dynamics and emissions in the reacting case. To reveal dependencies of cooling air injection on combustion stability and NOx emissions, the amount of injected cooling air is varied. OH*-chemiluminescence measurements are applied to characterize the impact of cooling air injection on the flame front. Emissions are collected for different cooling air concentrations, both global measurements at the chamber exit and local measurements in the region of the flame front close to the burner exit. The effect of cooling air injection on pulsation level is investigated by evaluating the dynamic pressure in the combustor. The flame stabilization at the burner exit changes with an increasing degree of dilution with cooling air. Depending on the amount of cooling only a specific share of the additional air participates in the combustion process.
A Novel Thermally Activated R744 Heat Pump Cycle
Authors: Bannar-Martin Luke , Childs Peter
Published: November 2013

A novel thermally activated transcritical R744 heat pump cycle, which combines the principles of both the reverse Rankine cycle and Brayton cycle has been analysed. The cycle produces simultaneous hot and cold streams at three temperature levels; 60°C for hot water, 40°C for low temperature ambient heating, 10°C for ambient cooling. The cycle has been designed to fulfil the requirements of a flexible ‘hybrid’ trigeneration scheme, where the three energy streams (electricity, heating and cooling) can be matched closely to the user demands — maximising the Energy Utilisation Factor (EUF) of the fuel. Such a system is likely to be used in environmentally resilient cities in either tertiary sector buildings, interconnected residential zones, industry or other large buildings such as hospitals and educational establishments.

The cycle is activated using recuperated thermal energy from a gas turbine exhaust stream and under certain operating conditions uses a small proportion of the electricity produced by the gas turbine generator set. Recuperation is achieved using a direct exhaust gas to R744 recuperating heat exchanger. At higher levels of thermal recuperation, the increase in expander inlet temperature results in a substantial increase in the Coefficient Of Performance (COP). With an expander inlet temperature of 250°C the cycle achieves a COP in cooling of 1.13, whilst with a expander inlet temperature of 350°C the cycle achieves a COP in cooling of 1.58. These values of COP in cooling are typical of double and triple stage absorption chillers respectively. The values for COP in heating are 1.97 for an expander inlet temperature of 250°C, and 2.41 for an expander inlet temperature of 350°C.

The cycle is also capable of acting as a power positive bottoming cycle, whilst still providing heating and cooling. Under these circumstances, and assuming an expander inlet temperature of 350°C, the cycle has a thermal to mechanical conversion efficiency of 9.7%. The corresponding values of COP in cooling and heating are 1.03 and 1.80 respectively.
Effects of Bio-Derived Fuels on Emissions and Performance Using a 9-Point Lean Direct Injection Low Emissions Concept
Authors: Wey Changlie , Bulzan Dan
Published: November 2013

A 9-Point Lean Direct low emissions combustor concept was utilized to evaluate gaseous emissions performance of two bio-derived alternative jet fuels and a JP-8 fuel for comparison. Gaseous emissions were measured in a flame tube operating at inlet temperatures from 650 up to 1030 F, pressures of 150, 250, and 350 psia, and a range of fuel/air ratios. The alternative fuels consisted of a Hydroprocessed Esters and Fatty Acids Fuel made from tallow and a second bio derived fuel produced from direct fermentation of sugar.
Inverted Brayton Cycle With Exhaust Gas Recirculation: A Numerical Investigation
Authors: Henke Martin , Monz Thomas , Aigner Manfred
Published: November 2013

Micro gas turbine (MGT) based CHP units provide a highly efficient, low-pollutant technology to supply heat and electrical power from fossil and renewable energy sources; however, pressurized MGT systems in an electrical power range from 1 to 5 kWel utilize very small turbocharger components. These components suffer from higher losses, like seal and tip leakages, resulting in a reduced electrical efficiency.

This drawback is avoided by an Inverted Brayton Cycle (IBC) based system. In an IBC hot gas is produced in a combustion chamber at atmospheric pressure. Subsequently, the exhaust gas is expanded in a turbine from atmospheric to sub-atmospheric pressure level. In order to increase electrical efficiency, heat from the turbine exhaust gas is recuperated to the combustion air. After recuperation, the gas is compressed to atmospheric pressure and is discharged from the cycle. To decrease the power demand of the compressor, and thereby increasing the electrical cycle efficiency, it is crucial to further extract residual thermal power from the gas before compression. Coolant flows provided by heating applications can use this heat supply combined with heat from the discharged exhaust gas. The low pressure levels of the IBC result in high volumetric gas flows, enabling the use of large, highly efficient turbocharger components. Because of this efficiency benefit and the described cooling demand, micro-CHP applications provide an ideal field for utilization of the IBC. To further increase the total efficiency, discharged exhaust gas can be partially recirculated to the air inlet of the cycle.

In the present paper a steady state analysis of an IBC with exhaust gas recirculation (EGR) is shown, and compared to the performance of a conventional Brayton Cycle with equivalent component properties. Using EGR, it could be found that the sensitivity of the electrical cycle efficiency to the coolant temperature further increases. The sequent discussion focuses on the trade-off between total efficiency and electrical efficiency, depending on coolant temperature and EGR rate. The results show that EGR can increase the total efficiency by 10 to 15 %-points, while electrical efficiency decreases by 0.5 to 1 %-point. If the coolant temperature is below 35 °C, condensation of water vapor in the exhaust gas leads to a further increase of heat recovery efficiency.

A validated in-house simulation tool based on turbocharger maps has been used for the calculations.
MAN’s New Gas Turbines for Mechanical Drive and Power Generation Applications
Authors: Aschenbruck Emil , Cagna Michele , Langusch Volker , Orth Ulrich , Spiegel Andreas , Wiedermann Alexander , Wiers Sven-Hendrik
Published: November 2013

MAN Diesel & Turbo recently developed a completely new gas turbine family for the first time in its history. The first product line contains both two-shaft and single-shaft gas turbines in the 6 – 7 MW class. The two-shaft engine was thoroughly tested at MAN’s gas turbine test center, and the first engine has been delivered to a launch customer. For MAN, it constitutes a technology platform that will produce further developments and new models in the coming years.

The two-shaft design makes the new gas turbine an ideal mechanical drive for both turbo compressors and pumps. This gas turbine operates to suit the optimum duty point of the driven machine; both in a wide speed and power range. The two stage power turbine design allows for a wide speed range of 45 to 105% while maintaining high efficiency. For power generation a single-shaft version has been created by adding one additional stage to the two stage high pressure turbine. The compressor pressure ratio is 15, which is high enough for achieving the highest potential efficiency for both generator and compressor drive applications. Low pollutant emission levels are achieved with MAN’s DLN combustion technology. The gas turbine exhaust temperature is sufficiently high to reach high heat recovery rates in combined heat and power cycles. Another important feature of the new gas turbine is its unrestricted suitability for taking load quickly and rapid load changes.

Service costs have also been significantly improved upon. MAN opted for a sturdy and modular gas turbine construction, while not compromising on efficiency. The objective is to extend service life and shorten down time occurrences. The modular package assembly process helps to reduce routine maintenance and repair time, and ultimately package downtime.
Numerical Investigation of Rotating Detonation Combustion in Annular Chambers
Authors: Escobar Sergio , Pakalapati Suryanarayana R. , Celik Ismail , Ferguson Donald , Strakey Peter
Published: November 2013

This article presents two dimensional (2D) and three-dimensional (3D) computational analysis of rotating detonation combustion (RDC) in annular chambers using the commercial computational fluid dynamics (CFD) solver ANSYS-Fluent V13. The applicability of ANSYS-Fluent to predict the predominant phenomena taking place in the combustion chamber of a rotating detonation combustor is assessed. Simulations are performed for stoichiometric Hydrogen-Air combustion using two different chemical mechanisms. First, a widely used one-step reaction mechanism that uses mass fraction of the reactant as a progress variable, then a reduced chemical mechanism for H2-Air combustion including NOx chemistry was employed. Time dependent 2D and 3D simulations are carried out by solving Euler equations for compressible flows coupled with chemical reactions. Fluent user defined functions (UDF) were constructed and integrated into the commercial CFD solver in order to model the micro nozzle and slot injection system for fuel and oxidizer, respectively. Predicted pressure and temperature fields and detonation wave velocities are compared for the two reaction mechanisms. Curvature effects on the properties of transverse detonation waves are studied by comparing the 2D and 3D simulations. The effects of diffusion terms on RDC phenomena are assessed by solving full Navier-Stokes equations and comparing the results with those from Euler equations. Computational results are compared with experimentally measured pressure data obtained from the literature. Results show that the detonation wave velocity is over predicted in all the simulations. However, good agreement between computational and experimental data for the pressure field and transverse detonation wave structure proves adequate capabilities of ANSYS-Fluent to predict the main physical characteristics of RDC operation. Finally, various improvements for RDC modeling are postulated, particularly for better prediction of wave velocity.
Heat Transfer for High Aspect Ratio Rectangular Channels in a Stationary Serpentine Passage With Turbulated and Smooth Surfaces
Authors: Smith Matthew A. , Mathison Randall M. , Dunn Michael G.
Published: November 2013

Heat transfer distributions are presented for a stationary three passage serpentine internal cooling channel for a range of engine representative Reynolds numbers. The spacing between the sidewalls of the serpentine passage is fixed and the aspect ratio (AR) is adjusted to 1:1, 1:2, and 1:6 by changing the distance between the top and bottom walls. Data are presented for aspect ratios of 1:1 and 1:6 for smooth passage walls and for aspect ratios of 1:1, 1:2, and 1:6 for passages with two surfaces turbulated. For the turbulated cases, turbulators skewed 45° to the flow are installed on the top and bottom walls. The square turbulators are arranged in an offset parallel configuration with a fixed rib pitch-to-height ratio (P/e) of 10 and a rib height-to-hydraulic diameter ratio (e/Dh) range of 0.100 to 0.058 for AR 1:1 to 1:6, respectively. The experiments span a Reynolds number range of 4,000 to 130,000 based on the passage hydraulic diameter.

While this experiment utilizes a basic layout similar to previous research, it is the first to run an aspect ratio as large as 1:6, and it also pushes the Reynolds number to higher values than were previously available for the 1:2 aspect ratio. The results demonstrate that while the normalized Nusselt number for the AR 1:2 configuration changes linearly with Reynolds number up to 130,000, there is a significant change in flow behavior between Re = 25,000 and Re = 50,000 for the aspect ratio 1:6 case. This suggests that while it may be possible to interpolate between points for different flow conditions, each geometric configuration must be investigated independently.

The results show the highest heat transfer and the greatest heat transfer enhancement are obtained with the AR 1:6 configuration due to greater secondary flow development for both the smooth and turbulated cases. This enhancement was particularly notable for the AR 1:6 case for Reynolds numbers at or above 50,000.
History of Short-Duration Measurement Programs Related to Gas Turbine Heat Transfer, Aerodynamics, and Aeroperformance at Calspan and OSU
Authors: Dunn Michael , Mathison Randall
Published: November 2013

Short-duration facilities have been used for the past thirty-five years to obtain measurements of heat transfer, aerodynamic loading, vibratory response, film-cooling influence, purge flow migration, and aeroperformance for full-stage high-pressure turbines operating at design corrected conditions of flow function, corrected speed, and stage pressure ratio. This paper traces the development of experimental techniques now in use at The Ohio State University (OSU) Gas Turbine Laboratory (GTL) from initial work in this area at the Cornell Aeronautical Laboratory (CAL, later to become Calspan) in 1975 through to the present. It is intended to summarize the wide range of research that can be performed with a short-duration facility and highlight the types of measurements that are possible.

Beginning with heat-flux measurements for the vane and blade of a Garrett TFE 731-2 HP turbine stage with vane pressure-surface slot cooling, the challenge of each experimental program has been to provide data to aid turbine designers in understanding the relevant flow physics and help drive the advancement of predictive techniques. Through many different programs, this has involved collaborators at a variety of companies and experiments performed with turbine stages from Garrett, Allison, Teledyne, Pratt and Whitney, General Electric Aviation, Rocketdyne, Westinghouse, and Honeywell. The Vane/Blade Interaction measurement and CFD program, which ran from the early eighties until 2000, provided a particularly good example of what can be achieved when experimentalists and computational specialists collaborate closely. Before conclusion of this program in 2000, the heat-flux and pressure measurements made for this transonic turbine operated with and without vane trailing edge cooling flow were analyzed and compared to predictive codes in conjunction with engineers at Allison, United Technologies Research Center, Pratt and Whitney, and GE Aviation in jointly published papers.

When the group moved to OSU in 1995 along with the facility used at Calspan, refined techniques were needed to meet new research challenges such as investigating blade damping and forced response, measuring aeroperformance for different configurations, and preparing for advanced cooling experiments that introduced complicating features of an actual engine to further challenge computational predictions. This required conversion of the test-gas heating method from a shock-tunnel approach to a blowdown approach using a combustor emulator to also create inlet temperature profiles, the development of instrumentation techniques to work with a thin-walled airfoil with backside cooling, and the adoption of experimental techniques that could be used to successfully operate fully cooled turbine stages (vane row cooled, blade row cooled, and proper cavity purge flow provided). Further, it was necessary to develop techniques for measuring the aeroperformance of these fully cooled machines.
Mean and Turbulent Velocity Profile Measurements on the Suction Side of a Film Cooled Turbine Vane
Authors: McClintic John W. , Dyson Thomas E. , Bogard David G. , Bradshaw Sean D.
Published: November 2013

Boundary layer velocity and turbulence profiles were measured on the suction side of a scaled up, film-cooled turbine vane airfoil. There have been a number of previous studies of the velocity profile on a turbine vane, but few have taken velocity profile data with film cooling, and none have taken such data on the suction side of the vane. Velocity and turbulence profile data were taken at two locations on the suction side of the vane — one at a high curvature region and one further downstream in a low curvature region. Data were collected for high (20%) and low (0.5%) mainstream turbulence conditions. For the upstream, high curvature location, velocity and turbulence profiles were found with and without the showerhead blowing and within and outside of the merged showerhead coolant jet. The data for the low curvature, downstream location was taken with injection from the showerhead alone, a second upstream row of holes alone, and the combination of the two cases. It was found that the presence of an active upstream row of holes thickens the boundary layer and increases urms both within and beyond the extent of the boundary layer. Span-wise variations showed that these effects are strongest within the core of the coolant jets. At the downstream location, the boundary layer velocity profile was most strongly influenced by the row of holes immediately upstream of that location. Finally, turbulence integral length scale data showed the effect of large scale mainstream turbulence penetrating the boundary layer. The increase in turbulence, thickening of the boundary layer, and large scale turbulence all play important roles in row to row coolant interactions and affect the film cooling effectiveness.
Numerical Computation of the Jet Impingement Cooling of High Pressure Ratio Compressors
Authors: Gröschel Elmar , Lipfert Carsten , Erb Wolfgang , Rusch Daniel
Published: November 2013

The material temperature field of a centrifugal compressor wheel is one important factor for the life time analysis of a compressor stage. Due to increasing thermal loads of advanced compressor stages, the thermal stresses and/or material temperature levels can exceed the allowed limits for a prescribed exchange interval and cooling techniques are needed to reduce the wheel temperature. One efficient cooling technique is the air impingement cooling. Unlike in gas turbines the impingement cooling is located in the back face region of the compressor wheel. From a computational point of view this means that the impingment jet is located in the stationary frame of reference and the cooled wall is located in the rotating frame of reference. In such a case the heat transfer problem becomes unsteady. The paper introduces a novel CHT-mixing plane interface for the frame change between stationary fluid domain and rotating solid domain to overcome the intrinsic unsteadiness caused by the jet impingement. Fluid mixing plane interfaces between rotor and stator are very common in industries to exploit periodic symmetries and to avoid time consuming unsteady compuations. However, the commercial solvers do not provide a mixing plane interface between fluid and solid domains. First, the new mixing plane approach is validated for a representative test case against a time resolved computation. In the second step, the new method is applied to a compressor stage. Two operating conditions, each with three different cooling mass flows have been computed. The comparison of the wheel temperature field corresponds very well to the computational results for all operating conditions. The temperature field analysis reveals valuable information on the heat transfer in highly loaded compressor stages which can be exploited in the design process of the compressor cooling.
Aerodynamic Simulation of a High-Pressure Centrifugal Fan for Process Industries
Authors: Corsini Alessandro , Delibra Giovanni , Rispoli Franco , Sheard Anthony G. , Venturini Paolo
Published: November 2013

Large centrifugal fans in cement factories operate in an aggressive environment, as the cement particles dispersed in the flow are responsible for strong blade surface erosion that leads to performance degradation.

This paper reports on the simulation of the flow field in a large centrifugal fan designed for process industry applications. The aerodynamic investigation, at a preliminary level, highlights the critical regions inside the device and suggests possible modification to increase its duty life.

This paper reports on the simulation of the flow field in a large centrifugal fan designed for process industry applications. The aerodynamic investigation, at a preliminary level, serves the aim of highlighting the critical regions inside the device and suggest possible modification to increase its duty life.

In the paper we show the results of numerical computations carried out with the finite volume open-source code OpenFOAM using Multiple Reference Frame methodology. Reynolds Averaged Navier-Stokes equations for incompressible flow were solved with standard eddy-viscosity k-ε model in order to explore the aerodynamic behaviour of the fan in near-design operations. The incompressible flow hypothesis was adopted even if locally Mach number can exceed 0.5. In fact in this case the pressure-rise does not lead to a variation of the density able to affect the velocity field divergence.

Given the high performance of the investigated impeller, the present work has a twofold objective. First, we seek to define an accurate numerical methodology to investigate high-pressure radial fans. Second, we provide detailed analysis of the inlet ring-impeller-volute assembly inner workings under realistic distorted inflow conditions.

The results provide the evolution of the pressure field in order to validate the accuracy of the simulation in reproducing the motion inside the fan that was fundamental for credible particle dispersion reproduction. We then investigate the three-dimensional flow field through the impeller in order to provide details about the secondary flow structures that develop within the blade vanes.