bluuebunny/crossref_metadata_2025 huggingface dataset:
Effectively Selecting Suppliers Using Total Cost of Ownership
Authors: Degraeve Zeger , Roodhooft Filip
Published: April 2006

In today's business world characterized by intense global competition, cost management is an important strategic weapon. External purchases of products and services generally account for more than 50 percent of total costs. Significant cost savings can be realized by effectively selecting suppliers and determining optimal order quantities. Existing cost management tools focus on rationalizing production and distribution activities and do not consider the purchasing function. In practice, simple, subjective, and incomplete approaches for supplier selection are often used. This article presents a rigorous decision support system using total cost of ownership information. The system uses a dynamic mathematical programming model that derives a purchasing strategy by minimizing the total costs, taking into account the relevant constraints. It allows the purchasing and supply manager to objectively evaluate alternative policies. A recent implementation of the system for two product groups at Cockerill Sambre shows potential savings of more than 10 percent compared to current practices.
Supply Chain Flexibility: An Empirical Study
Authors: Vickery Shaw nee , Calantone Roger , Dröge Cornelia
Published: April 2006

This article examines dimensions of supply chain flexibility and their relationships with environmental uncertainty, business performance, and functional interfaces. The findings indicate that volume flexibility and launch flexibility are key responses to marketing practices uncertainty and product uncertainty, respectively, in the highly cyclical furniture industry. Volume flexibility is also positively related to all measures of overall firm performance and highly related to market share and market share growth. Overall, excellent performers on supply chain flexibility are rewarded at the bottomline. However, performance with respect to volume, launch, and target market flexibilities has the widest ranging impact on financial and market performance.
Examining Supplier Improvement Efforts from Both Sides
Authors: Forker Laura B. , Ruch William A. , Hershauer James C.
Published: April 2006

Perceptual data from the population of buyers and suppliers to a major electronics firm were collected to test the extent of judgmental convergence between matched pairs of buyers and suppliers with respect to the suppliers' quality management practices and the buyers' supplier development activities. The customer firm (and its supply base) was chosen due to its national leadership in quality improvement achievements and forward thinking in supply management. It was believed that this electronic systems manufacturer would be most likely to have reached a common understanding with its suppliers regarding continuous improvement needs. Results indicate that buyers and suppliers are largely in agreement regarding the extent of the suppliers' total quality management (TQM) implementation. Little agreement was noted regarding the buyers' execution of supplier development activities. Recommendations to supply managers regarding enhanced communication with their suppliers and recognition of their suppliers' role in quality improvement are offered.
Purchasing and Supplier Involvement in Process Improvement: A Source of Competitive Advantage
Authors: McGinnis Michael A. , Vallopra Rafeekh Mele
Published: April 2006

While purchasing and supplier involvement in new product development has been studied, little research has been conducted into purchasing and supplier involvement in production process development/ improvement. Two hundred seventy‐one senior managers responded to a mail questionnaire regarding purchasing and supplier involvement in process development/improvement in anufacturing, service, not‐for‐profit, and government organizations. Factor scores of the research variables were analyzed using t‐tests to assess the effects of process as a source of competitive advantage, purchasing involvement, and supplier involvement on process development/improvement practice and strategy. Contingency table analysis with the chi‐square statistic was used to assess the effects of industry category. It was found that processes contribute to competitive advantage, purchasing plays a major role in process development/improvement, and that purchasing and supplier involvement contributes to process development/improvement in all industry categories. These contributions are greatest in manufacturing. The implications of this research to purchasing professionals, researchers, and academicians are discussed.
The Relationship Among Purchasing Benchmarking, Strategic Purchasing, Firm Performance, and Firm Size
Authors: Carr Amelia S. , Smeltzer Larry R.
Published: April 2006

Benchmarking is not a new process, but it has received increasingly more emphasis within the purchasing process during the recent past. This article presents a brief background and description of benchmarking. The literature on the value of benchmarking is then reviewed. Next, hypotheses are presented and tested on the relationship among benchmarking, strategic purchasing, and firms’ performance. Finally, research and managerial implications of the research results are discussed.
Vendor Selection Using Principal Component Analysis
Authors: Petroni Alberto , Braglia Marcello
Published: April 2006

Purchasing managers need to periodically evaluate supplier performance in order to retain those suppliers which meet their requirements in terms of several performance criteria. The evaluation element typically consists of identifying the attributes, criteria, or factors relevant to the decision and then measuring or rating each vendor by considering each of the relevant factors. A critical part of the overall supplier selection process is the determination of the relative importance of each of the factors. This article presents an alternative decision model to evaluate the relative performance of suppliers that have multiple outputs and inputs. This approach is based on a multivariate statistical method, principal component analysis, that uses information obtained from eigenvalues to combine different ratio measures defined by every input and every output. The method has been employed to aggregate multiple performance measures for a real‐world data set of suppliers of a medium‐sized firm operating in the bottling machinery industry.
Strategic Alliance Success Factors
Authors: Whipple Judith M. , Frankel Robert
Published: April 2006

There is recognition that competition is shifting from a “firm versus firm perspective” to a “supply chain versus supply chain perspective.” In response to this shift, firms seeking competitive advantage are participating in cooperative supply chain arrangements, such as strategic alliances, which combine their individual strengths and unique resources. Buyer‐supplier sourcing relationships are a primary focus of alliance improvement efforts. While interest in such arrangements remains strong, it is well accepted that creating, developing, and maintaining a successful alliance is a very daunting task. This research addresses several critical issues regarding that challenge. First, what factors contribute most to long‐term alliance success? Second, what conditions define the presence of those success factors? Third, do buyers and suppliers in an alliance agree on those success factors and defining conditions? The research results demonstrate a remarkably consistent perspective among alliance partners regarding key success factors, despite the acknowledgment that the resultant success is based on a relatively even, but not equal, exchange of benefits and resources. Additionally, within an alliance's intended “win‐win” foundation, suppliers must recognize their innate dependence on customers. Finally, significant opportunities for improvement exist with respect to alliance goal clarification, communication, and performance evaluation.
The Use and Impact of Communication Media in Purchasing and Supply Management
Authors: Larson Paul D. , Kulchitsky Jack D.
Published: April 2006

Effective communication is a critical component of buyer‐supplier relationships. Purchasing professionals utilize a variety of media to communicate with suppliers, including phone, fax, face‐to‐face, mail, e‐mail, Internet, and electronic data interchange (EDI). The purpose of this research was to assess the impact of EDI and a variety of other media on buyer‐supplier relationships and performance. Analysis of the responses from a survey revealed that EDI is not living up to its promise. The results also show that purchasing professionals’ preference for various communication media depends on the nature of the message being transmitted.
Benchmarking Internal Supply Chain Performance: Development of a Framework
Authors: Shah Janat , Singh Nitin
Published: April 2006

This article develops performance measures that can be computed through publicly available information. The article describes an approach for benchmarking using these performance measures and demonstrates how meaningful results may be derived from this exercise. By following this framework, a firm can identify areas of opportunity for improvement in its internal supply chain. Further, the framework can help to identify specific reasons behind the performance levels in the internal supply chain and stimulate performance improvement. To illustrate the framework, it is applied to the paint industry. The framework provides meaningful results for the firms in the industry.
The Resource Based Perspective, Rents, and Purchasing's Contribution to Sustainable Competitive Advantage
Authors: Ramsay John
Published: April 2006

The resource based perspective (RBP) within the field of strategy seeks to understand the relationship between a firm's resources and its competitive advantage. Some RBP authors have concluded that it is logically impossible for organizations to generate sustainable competitive advantage from purchasing activities. One of this article's central objectives is to test the validity of that conclusion. It is hoped that the completion of that task may make it possible to assist in the process of raising the purchasing function's strategic profile in the modern firm.
Purchasing Professionals' Perceived Differences between Purchasing Materials and Purchasing Services
Authors: Smeltzer Larry R. , Ogden Jeffrey A.
Published: April 2006

This research addresses a gap in the current literature by examining the differences between the process of purchasing services and the process of purchasing materials. Four hypotheses concerning the possible differences were developed based on a review of the relevant literature. These hypotheses were then tested using qualitative focus studies and a quantitative survey involving 82 purchasing managers with an average of 9.8 years' purchasing experience. Also, 14 interviews were conducted with purchasing executives to gain a better understanding of perceived differences. The results indicate that perceived differences exist between the processes of purchasing services and purchasing materials, especially in terms of the complexity of these processes. These perceived differences vary by the number of years of purchasing experience and the type of purchasing experience (services versus materials). Fifteen individual process steps were examined to determine the exact nature of the differences between these two processes. Managerial and research implications are discussed throughout the article.
Supplier Development Practices: Product‐ and Service‐Based Industry Comparisons
Authors: Krause Daniel R. , Scannell Thomas V.
Published: April 2006

Supplier development has become a viable supply chain management practice across industries as firms continue to focus on their core competencies and outsource a significant percentage of the costs of goods sold. Supplier development practices used by buying firms include formal supplier assessment and feedback, supplier incentives, competitive pressure, and direct involvement improving performance through activities such as training and investment. Although it is apparent that such strategies and processes are used to some extent across industries, it is unclear if there are differences in supplier development approaches between product‐ and service‐based firms. The findings indicate that service firms tend to rely on the competitive pressure of market forces to instigate supplier performance to a greater extent than product‐based firms and that productbased firms tend to use assessment, incentives, and direct involvement to a greater extent than service firms.
Buyer‐Supplier Relationships and Organizational Health
Authors: McHugh Marie , Humphreys Paul , Mclvor Ronan
Published: April 2006

This article examines the relationship between organizational health and buyer‐supplier relationships. Contemporary research has emphasized the need for organizations to move toward closer cooperation. The decision to engage in partnership arrangements is one that has major implications for buyers and suppliers. Using evidence from an exploratory case study, the challenges presented in developing a close, cooperative, and mutually beneficial trading relationship between a buyer and a supplier, where one partner, the buyer, is in a powerful position, are investigated. It is argued that powerful buyers can seriously damage organizational health. The findings provide evidence that it is essential to promote communication structures that encourage dialogue, consultation, and employee participation in decisionmaking. This is particularly important where decisionmaking could benefit from the in‐depth technical knowledge of middle and junior managers and shopfloor workers.
Factors Affecting the Level of Trust and Commitment in Supply Chain Relationships
Authors: Kwon Ik‐Whan G. , Suh Taewon
Published: April 2006

Trust is a critical factor fostering commitment among supply chain partners. The presence of trust improves measurably the chance of successful supply chain performance. A lack of trust among supply chain partners often results in inefficient and ineffective performance as the transaction costs (verification, inspections and certifications of their trading partners) mount. Although the literature often mentions a relationship between trust and commitment, there is a lack of empirical testing of such relationship in the supply context. This study attempts to fill the gap between the theoretical argument and empirical testing. Results using a comprehensive survey of supply chain practitioners indicate that a firm's trust in its supply chain partner is highly associated with both sides' specific asset investments (positively) and behavioral uncertainty (negatively). It is also found that information sharing reduces the level of behavioral uncertainty, which, in turn, improves the level of trust. A partner's reputation in the market has a strong positive impact on the trust‐building process, whereas a partner's perceived conflict creates a strong negative impact on trust. Finally, the level of commitment is strongly related to the level of trust. Policy implications are discussed.
The Impact of Energy Deregulation on Sourcing Strategy
Authors: Handfield Robert B.
Published: April 2006

Supply researchers predicted in 1999 that deregulation would change the landscape for the purchasers of energy. The current research was undertaken to determine the nature and direction of the predicted changes in energy sourcing behavior. Based on detailed interviews with managers, government officials, and lobbyists, the risks and rewards associated with recent events in deregulation are examined and analyzed. Next, a detailed process for developing and implementing an energy sourcing strategy for commercial businesses that considers these risks and rewards of alternative energy sourcing channels is developed. This is followed by a process that involves aggregating data, obtaining support, defining risk tolerance, and spending parameters that involved stake‐holders, evaluating proposals, executing the strategy and monitoring it overtime. Finally, insights into the future trends in deregulated energy markets are described. Results suggest that a focused approach to developing detailed supply market intelligence can assist sourcing managers in preparing for the deregulated era and achieve significant cost savings in energy spending.
Outsourcing and Inter/lntra Supply Chain Dynamics: Strategic Management Issues
Authors: Parker David W. , Russell Katie A.
Published: April 2006

This article analyzes the outsourcing of information technology services, using an action inquiry methodology. Research spanned the disengagement and beginning of IT service functions transferred from work groups in the parent company to outsource teams. Results identified the importance of addressing strategic issues and inter/intra relationships between parent company team members and their outsource‐counterparts. Conclusions indicate that behavioral issues such as psychological contracts within inter/intra work groups, power and trust are highly significant managerial issues in the success or failure of an outsourcing strategy.
Study of High Load Operation Limit Expansion for Gasoline Compression Ignition Engines
Authors: Yoshizawa Koudai , Teraji Atsushi , Miyakubo Hiroshi , Yamaguchi Koichi , Urushihara Tomonori
Published: April 2006

In this research, combustion characteristics of gasoline compression ignition engines have been analyzed numerically and experimentally with the aim of expanding the high load operation limit. The mechanism limiting high load operation under homogeneous charge compression ignition (HCCI) combustion was clarified. It was confirmed that retarding the combustion timing from top dead center (TDC) is an effective way to prevent knocking. However, with retarded combustion, combustion timing is substantially influenced by cycle-to-cycle variation of in-cylinder conditions. Therefore, an ignition timing control method is required to achieve stable retarded combustion. Using numerical analysis, it was found that ignition timing control could be achieved by creating a fuel-rich zone at the center of the cylinder. The fuel-rich zone works as an ignition source to ignite the surrounding fuel-lean zone. In this way, combustion consists of two separate auto-ignitions and is thus called two-step combustion. In the simulation, the high load operation limit was expanded using two-step combustion. An engine system identical to a direct-injection gasoline (DIG) engine was then used to validate two-step combustion experimentally. An air-fuel distribution was created by splitting fuel injection into first and second injections. The spark plug was used to ignite the first combustion. This combustion process might better be called spark-ignited compression ignition combustion (SI-CI combustion). Using the spark plug, stable two-step combustion was achieved, thereby validating a means of expanding the operation limit of gasoline compression ignition engines toward a higher load range.
Dynamic Simulation of Carbonate Fuel Cell-Gas Turbine Hybrid Systems
Authors: Roberts Rory A. , Brouwer Jack , Liese Eric , Gemmen Randall S.
Published: April 2006

Hybrid fuel cell/gas turbine systems provide an efficient means of producing electricity from fossil fuels with ultra low emissions. However, there are many significant challenges involved in integrating the fuel cell with the gas turbine and other components of this type of system. The fuel cell and the gas turbine must maintain efficient operation and electricity production while protecting equipment during perturbations that may occur when the system is connected to the utility grid or in stand-alone mode. This paper presents recent dynamic simulation results from two laboratories focused on developing tools to aid in the design and dynamic analyses of hybrid fuel cell systems. The simulation results present the response of a carbonate fuel cell/gas turbine, or molten carbonate fuel cell/gas turbine, (MCFC/GT) hybrid system to a load demand perturbation. Initial results suggest that creative control strategies will be needed to ensure a flexible system with wide turndown and robust dynamic operation.
Tuning Your Fuel-Gas Delivery System
Authors: Newbound T. D. , Al-Showiman K. S.
Published: April 2006

Saudi Aramco has focused more attention in recent years on fuel-gas conditioning for land-based industrial and aeroderivative combustion gas turbines (CGTs). Hydrocarbon dew points and entrained solids are two important fuel quality issues that frequently trouble CGT operators, partly because they cannot be guaranteed by the fuel suppliers and they are rarely monitored by the operators. This paper addresses these issues and offers some practical advice to optimize the design and operation of fuel gas delivery systems. Saudi Aramco has been testing an automated on-line dew point monitor capable of detecting both hydrocarbon and aqueous dew points in natural gas. Dew point monitoring, conducted at three locations on the fuel gas grid, revealed wide variations in the hydrocarbon and aqueous dew points due to a variety of conditions. Gas production and pipeline operations accounted for the most dramatic variations in dew points, but exposure of pipelines to the weather can also be important. Measurement of pipeline solids for the purpose of sizing and placement of particle filters have also been explored. Pipeline scraping, gas velocities, length of pipeline span, pipeline junctions, and control valves are all considerations for solid control strategies. The optimized design and operation of a CGT fuel system is highly dependent on dew point control and efficient removal of entrained pipeline solids. Practical experience in monitoring hydrocarbon and aqueous dew points, pipeline solids control, and optimizing fuel conditioning equipment are considered.
Effects of Heat Release Mode on Emissions and Efficiencies of a Compound Diesel Homogeneous Charge Compression Ignition Combustion Engine
Authors: Su Wanhua , Zhang Xiaoyu , Lin Tiejian , Pei Yiqiang , Zhao Hua
Published: April 2006

A compound diesel homogeneous charge compression ignition (HCCI) combustion system has been developed based on the combined combustion strategies of multiple injection strategy and a mixing enhanced combustion chamber design. In this work, a STAR-CD based, multidimensional modeling is conducted to understand and optimize the multiple injection processes. The parameters explored included injection timing, dwell time, and pulse width. Insight generated from this study provides guidelines on designing the multipulse injection rate pattern for optimization of fuel-air mixing. Various heat release modes created by different injection strategies are investigated by experimental comparison of combustion efficiency, heat loss, and thermal efficiency. It is demonstrated that the process of fuel evaporation and mixing are strongly influenced by pulse injection parameters. Through control of the parameters, the stratification and autoignition of the premixed mixture, and the heat release mode can be controlled. The dispersed mode of heat release created only by the compound diesel HCCI combustion is a flexible mode in combustion control. The thermal efficiency with this mode can reach approximately to as high as that of conventional diesel combustion, while the NOx and smoke emissions can be reduced simultaneously and remarkably.
A Comprehensive Thermodynamic Approach to Acoustic Cavitation Simulation in High-Pressure Injection Systems by a Conservative Homogeneous Two-Phase Barotropic Flow Model
Authors: Catania Andrea E. , Ferrari Alessandro , Manno Michele , Spessa Ezio
Published: April 2006

A general conservative numerical model for the simulation of transmission-line unsteady fluid dynamics has been developed and applied to high-pressure injection systems. A comprehensive thermodynamic approach for modeling acoustic cavitation, i.e., cavitation induced by wave propagation, was proposed on the basis of a conservative homogeneous two-phase barotropic flow model of a pure liquid, its vapor, and a gas, both dissolved and undissolved. A physically consistent sound speed equation was set in a closed analytical form of wide application. For the pure-liquid flow simulation outside the cavitation regions, or in the absence of these, temperature variations due to compressibility effects were taken into account, for the first time in injection system simulation, through a thermodynamic relation derived from the energy equation. Nevertheless, in the cavitating regions, an isothermal flow was retained consistently with negligible macroscopic thermal effects due to vaporization or condensation, because of the tiny amounts of liquid involved. A novel implicit, conservative, one-step, symmetrical, and trapezoidal scheme of second-order accuracy was employed to solve the partial differential equations governing the pipe flow. It can also be enhanced at a high-resolution level. The numerical model was applied to wave propagation and cavitation simulation in a high-pressure injection system of the pump-line-nozzle type for light and medium duty vehicles. The system was relevant to model assessment because, at part loads, it presented cavitating flow conditions that can be considered as severe, at least for a diesel injection system. The predicted time histories of pressure at two pipe locations and of injector needle lift were compared to experimental results, substantiating the validity and robustness of the developed conservative model in simulating acoustic cavitation inception and desinence with great accuracy degree. Cavitation transients and the flow discontinuities induced by them were numerically predicted and analyzed.
Quasidimensional Modeling of Direct Injection Diesel Engine Nitric Oxide, Soot, and Unburned Hydrocarbon Emissions
Authors: Jung Dohoy , Assanis Dennis N.
Published: April 2006

In this study we report the development and validation of phenomenological models for predicting direct injection (DI) diesel engine emissions, including nitric oxide (NO), soot, and unburned hydrocarbons (HC), using a full engine cycle simulation. The cycle simulation developed earlier by the authors (D. Jung and D. N. Assanis, 2001, SAE Transactions: Journal of Engines, 2001-01-1246) features a quasidimensional, multizone, spray combustion model to account for transient spray evolution, fuel–air mixing, ignition and combustion. The Zeldovich mechanism is used for predicting NO emissions. Soot formation and oxidation is calculated with a semiempirical, two-rate equation model. Unburned HC emissions models account for three major HC sources in DI diesel engines: (1) leaned-out fuel during the ignition delay, (2) fuel yielded by the sac volume and nozzle hole, and (3) overpenetrated fuel. The emissions models have been validated against experimental data obtained from representative heavy-duty DI diesel engines. It is shown that the models can predict the emissions with reasonable accuracy. Following validation, the usefulness of the cycle simulation as a practical design tool is demonstrated with a case study of the effect of the discharge coefficient of the injector nozzle on pollutant emissions.
Properties, Weldability, and Applications of Modern Wrought Heat-Resistant Alloys for Aerospace and Power Generation Industries
Authors: Rowe M. D. , Ishwar V. R. , Klarstrom D. L.
Published: April 2006

Alloy selection and alloy design both require consideration of an array of material attributes, including in-service properties, weldability, and fabricability. Critical properties of modern heat-resistant alloys for gas turbine applications include high-temperature strength, thermal stability, oxidation resistance, and fatigue resistance. In this paper, the properties of 12 solid-solution-strengthened and six age-hardenable heat-resistant alloys are compared. Weldability is an important attribute and can be a major limiting factor in the use of certain alloys. Weldability test methods are discussed, and the resistance of alloys to solidification cracking and strain-age cracking is compared. The use of weldability testing in the development of modern heat-resistant alloys is discussed with several examples cited. Finally, alloy selection for gas turbine components is outlined, taking into account both alloy properties and fabricability.
Contact Dynamic Response With Misalignment in a Flexible Rotor/Magnetic Bearing System
Authors: Keogh P. S. , Cole M. O. T.
Published: April 2006

This paper investigates the vibration characteristics of rotor displacement signals in a magnetic bearing system under conditions when rotor contact with auxiliary bearings is possible. Since these signals may be used for feedback control, it is necessary to determine how they may affect the ability of the controller to regain rotor levitation. An experimental system is used to demonstrate the sensitivity of the rotor nonlinear dynamic behavior to unbalance, which is sufficient to cause contact during rotor run-up through rigid-body and flexural mode critical speeds. Complex rotor dynamics may involve contact with more than one auxiliary bearing or bush. Application of appropriate rotating forces to the rotor through a magnetic bearing is also shown to induce similar contact dynamics. Thus, an alternative procedure for assessing the nonlinear rotor dynamic behavior is established with the potential for identification of appropriate control forces. The contact dynamics are also considered in the presence of auxiliary bearing misalignment. Misalignment may arise through physical translation of a housing or through steady-state offset errors in sensor measurements. A misalignment of 50% of the nominal radial clearance is applied at an auxiliary bearing. Various contact modes are evident as the rotor is run up in speed. During rundown, different contact dynamics may be encountered and the level of such hysteresis is assessed.
Stainless Steels With Improved Oxidation Resistance for Recuperators
Authors: Pint Bruce A.
Published: April 2006

New materials are being evaluated to replace type 347 stainless steel in microturbine recuperators operating at higher temperatures in order to increase the efficiency of the microturbine. Commercial alloys 120 and 625 are being tested along with potentially lower cost substitutes, such as Fe-20Cr-25Ni and Fe-20Cr-20Ni. Long-term testing of these materials at 650–700 °C shows excellent corrosion resistance to a simulated exhaust gas environment. Testing at 800 °C has been used to further differentiate the performance of the various materials. The depletion of Cr from foils of these materials is being used to evaluate the rate of attack. Although those alloys with the highest Ni and Cr contents have longer lives in this environment, lower alloyed steels may have sufficient protection at a lower cost.
Gas Turbine Engine Durability Impacts of High Fuel-Air Ratio Combustors: Near Wall Reaction Effects on Film-Cooled Backward-Facing Step Heat Transfer
Authors: Milanes David W. , Kirk Daniel R. , Fidkowski Krzysztof J. , Waitz Ian A.
Published: April 2006

As commercial and military aircraft engines approach higher total temperatures and increasing overall fuel-to-air ratios, the potential for significant chemical reactions to occur downstream of the combustor is increased. This may take place when partially reacted species leave the combustor and encounter film-cooled surfaces. One common feature on turbine endwalls is a step between various engine components and seals. Such step features produce recirculating flows which when in the vicinity of film-cooled surfaces may lead to particularly severe reaction zones due to long fluid residence times. The objective of this paper is to study and quantify the surface heat transfer implications of such reacting regions. A shock tube experiment was employed to generate short duration, high temperature (1000–2800 K) and pressure (6 atm) flows over a film-cooled backward-facing step. The test article contained two sets of 35 deg film cooling holes located downstream of a step. The film-cooling holes could be supplied with different gases, one side using air and the other nitrogen allowing for simultaneous testing of reacting and inert cooling gases. A mixture of ethylene and argon provided a fuel-rich free stream that reacted with the air film resulting in near wall reactions. The relative increase in surface heat flux due to near wall reactions was investigated over a range of fuel levels, momentum blowing ratios (0.5–2.0), and Damköhler numbers (ratio of characteristic flow time to chemical time) from near zero to 30. The experimental results show that for conditions relevant for future engine technology, adiabatic flame temperatures can be approached along the wall downstream of the step leading to potentially significant increases in surface heat flux. A computational study was also performed to investigate the effects of cooling-jet blowing ratio on chemical reactions behind the film-cooled step. The blowing ratio was found to be an important parameter governing the flow structure behind the backward-facing step, and controlling the characteristics of chemical-reactions by altering the local equivalence ratio.
Integration of Gas Turbines Adapted for Syngas Fuel With Cryogenic and Membrane-Based Air Separation Units: Issues to Consider for System Studies
Authors: Wimer John G. , Keairns Dale , Parsons Edward L. , Ruether John A.
Published: April 2006

The purpose of this paper is to aid systems analysts in the design, modeling, and assessment of advanced, gasification-based power generation systems featuring air separation units (ASUs) integrated with gas turbines adapted for syngas fuel. First, the fundamental issues associated with operating a gas turbine on syngas will be reviewed, along with the motivations for extracting air from the turbine-compressor and/or injecting nitrogen into the turbine expander. Configurations for nitrogen-only and air-nitrogen ASU integration will be described, including the benefits and drawbacks of each. Cryogenic ASU technology will be summarized for both low-pressure and elevated-pressure applications and key design and integration issues will be identified and discussed. Finally, membrane-based ASU technology will be described and contrasted with cryogenic technology in regard to system design and integration.
Experimental Analysis of Soot Formation in Sooting Diffusion Flame by Using Laser-Induced Emissions
Authors: Hayashida Kazuhiro , Amagai Kenji , Satoh Keiji , Arai Masataka
Published: April 2006

Two-dimensional images of OH fluorescence, polycyclic aromatic hydrocarbons (PAHs) fluorescence, and laser-induced incandescence (LII) from soot were measured in a sooting diffusion flame. To obtain an accurate OH fluorescence image, two images were taken with the laser wavelength tuned to (“on”) and away from (“off”) the OH absorption line. An accurate OH fluorescence image was obtained by subtracting the off-resonance image from the on-resonance image. For the PAH fluorescence and LII measurements, temporally resolved measurements were used to obtain the individual images; the LII image was obtained by detecting the LII signal after the PAH fluorescence radiation had stopped and the PAH fluorescence image was obtained by subtracting the LII image from the simultaneous image of PAH fluorescence and LII. Based on the obtained images, the relative location of OH, PAH, and soot in the flame was discussed in detail. To investigate the PAH size distribution in a sooting flame using LIF, an estimation strategy for PAH size is proposed. Emission spectra were measured at several heights in the flame using a spectrograph. Since the emission wavelength of PAH fluorescence shifts toward longer wavelengths with increasing PAH size, the main PAH components in the emission spectra could be estimated. The results suggest that PAH grows and the type of PAH changes as the soot inception region was approached. Near the soot inception region, we estimated that the PAHs, which have over 16 carbon atoms, mainly constituted the emission spectrum.
Effect of Developing Turbulence and Markstein Number on the Propagation of Flames in Methane-Air Premixture
Authors: Haq M. Z.
Published: April 2006

In spark ignition engines, initial flame kernel is wrinkled by a progressively increasing bandwidth of turbulence length scales until eventually the size of the flame kernel is sufficient for it to experience the entire turbulence spectrum. In the present study, an effective rms turbulence velocity as a function of time, estimated by integrating the nondimensional power spectrum density (psd) function for isotropic turbulence, is utilized to analyze the statistical distribution of flame front curvatures and turbulent burning velocities of flames propagating in methane-air premixtures. The distributions of flame front curvatures show these to become more dispersed as the effective turbulence velocity increases, and result in increased burning of premixtures. A decrease in the Markstein number also results in a further increase in curvature dispersion and enhanced burning, in line with the flame stability analysis.
Lean Blowout Limit and NOx Production of a Premixed Sub-ppm NOx Burner With Periodic Recirculation of Combustion Products
Authors: Kalb Jochen R. , Sattelmayer Thomas
Published: April 2006

The technological objective of this work is the development of a lean-premixed burner for natural gas. Sub-ppm NOx emissions can be accomplished by shifting the lean blowout limit (LBO) to slightly lower adiabatic flame temperatures than the LBO of current standard burners. This can be achieved with a novel burner concept utilizing spatially periodic recirculation of combustion products: Hot combustion products are admixed to the injected premixed fresh mixture with a mass flow rate of comparable magnitude, in order to achieve self-ignition. The subsequent combustion of the diluted mixture again delivers products. A fraction of these combustion products is then admixed to the next stream of fresh mixture. This process pattern is to be continued in a cyclically closed topology, in order to achieve stable combustion of, for example, natural gas in a temperature regime of very low NOx production. The principal ignition behavior and NOx production characteristics of one sequence of the periodic process was modeled by an idealized adiabatic system with instantaneous admixture of partially or completely burnt combustion products to one stream of fresh reactants. With the CHEMKIN-II package, a reactor network consisting of one perfectly stirred reactor (PSR, providing ignition in the first place) and two plug flow reactors (PFR) has been used. The effect of varying burnout and the influence of the fraction of admixed flue gas has been evaluated. The simulations have been conducted with the reaction mechanism of Miller and Bowman and the GRI-Mech 3.0 mechanism. The results show that the high radical content of partially combusted products leads to a massive decrease of the time required for the formation of the radical pool. As a consequence, self-ignition times of 1 ms are achieved even at adiabatic flame temperatures of 1600 K and less, if the flue gas content is about 50–60% of the reacting flow after mixing is complete. Interestingly, the effect of radicals on ignition is strong, outweighs the temperature deficiency and thus allows stable operation at very low NOx emissions.
Post-Combustion In-Cylinder Vaporization During Cranking and Startup in a Port-Fuel–Injected Spark Ignition Engine
Authors: Cowart Jim S.
Published: April 2006

During port-fuel–injected (PFI) spark-ignition (SI) engine startup and warm-up fuel accounting continues to be a challenge. Excess fuel must be injected for a near stoichiometric combustion charge. The “extra” fuel that does not contribute to the combustion process may stay in the intake port or as liquid films on the combustion chamber walls. Some of this combustion chamber wall liquid fuel is transported to the engine’s oil sump and some of this liquid fuel escapes combustion and evolves during the expansion and exhaust strokes. Experiments were performed to investigate and quantify this emerging in-cylinder fuel vapor post-combustion cycle by cycle during engine startup. It is believed that this fuel vapor is evaporating from cylinder surfaces and emerging from cylinder crevices. A fast in-cylinder diagnostic, the fast flame ionization detector, was used to measure this behavior. Substantial post-combustion fuel vapor was measured during engine startup. The amount of post-combustion fuel vapor that develops relative to the in-cylinder precombustion fuel charge is on the order of one for cold starting (0 °C) and decreases to ∼13 for hot starting engine cycles. Fuel accounting suggests that the intake port puddle forms quickly, over the first few engine cranking cycles. Analysis suggests that sufficient charge temperature and crevice oxygen exists to at least partially oxidize the majority of this post-combustion fuel vapor such that engine out hydrocarbons are not excessive.
Gas Turbine and Generator Test Experience in Support of the Advanced Hull Form Inshore Demonstrator (AHFID)
Authors: Carr Roger J. , Lison Denis , Willett Fred T.
Published: April 2006

This paper describes a test program designed to assess the suitability of a TF40-based gas turbine generator set (genset) for use in the Advanced Hull Form Inshore Demonstrator (AHFID). An overall description of the test program and its objectives is given. Test results are presented. The relevance of the test to the greater program goal of demonstrating the viability of rim-driven propulsion technology is discussed. The genset demonstration test was successfully completed in 2003. The package performed as designed and met all test objectives.
Experimental Validation of an Improved Squish Velocity Model for Bowl-in-Piston Combustion Chambers
Authors: Lappas P. , Evans R. L.
Published: April 2006

A simple two-zone mass transfer model was used to predict the mean squish velocity history at the rim of a conventional bowl-in-piston combustion chamber. The chamber’s geometry produces gas flow that converges radially inwards (“squish”) as TDC (top dead center) is approached. The squish flow generates turbulence, which can be used to enhance the combustion rate. When compared with PIV (particle image velocimetry) measurements, the peak squish velocity at the bowl rim was 12% less than the value predicted by the simple mass transfer model. After a thorough examination, the assumption of uniform density in the simple model was strongly suspected to be the cause of this discrepancy. Improvements were made to the simple model to account for density variations that are caused by nonuniform heat transfer in the combustion chamber. The revised model yielded velocities that were in close agreement with PIV measurements.
Three-Dimensional Catalytic Regeneration Modeling of SiC Diesel Particulate Filters
Authors: Pontikakis George , Stamatelos Anastassios
Published: April 2006

Increasingly stringent diesel particulate emissions standards have reestablished international interest in diesel filters, whose first series application dates back to 1985. Modern diesel engine technology, with computerized engine management systems and advanced, common rail injection systems, needs to be fully exploited to support efficient and durable diesel filter systems with catalytic aids, as standard equipment in passenger cars. Efficient system and components’ optimization requires the use of mathematical models of diesel filter performance. The three-dimensional model for the regeneration of the diesel particulate filter presented in this paper has been developed as an engineering tool for the detailed design optimization of SiC diesel filters of modular structure. The 3-D modeling is achieved by interfacing an existing 1-D model to commercial finite element method software for the computation of the 3-D temperature field within the whole filter assembly, including the adhesive of the filter blocks, the insulation mat, and the metal canning. The 3-D model is applied to real-world component optimization studies of diesel filter systems.
A Novel Approach to Mechanism Reduction Optimization for an Aviation Fuel/Air Reaction Mechanism Using a Genetic Algorithm
Authors: Elliott L. , Ingham D. B. , Kyne A. G. , Mera N. S. , Pourkashanian M. , Wilson C. W.
Published: April 2006

This study presents a novel multiobjective genetic-algorithm approach to produce a new reduced chemical kinetic reaction mechanism to simulate aviation fuel combustion under various operating conditions. The mechanism is used to predict the flame structure of an aviation fuel/O2∕N2 flame in both spatially homogeneous and one-dimensional premixed combustion. Complex hydrocarbon fuels, such as aviation fuel, involve large numbers of reaction steps with many species. As all the reaction rate data are not well known, there is a high degree of uncertainty in the results obtained using these large detailed reaction mechanisms. In this study a genetic algorithm approach is employed for determining new reaction rate parameters for a reduced reaction mechanism for the combustion of aviation fuel-air mixtures. The genetic algorithm employed incorporates both perfectly stirred reactor and laminar premixed flame data in the inversion process, thus producing an efficient reaction mechanism. This study provides an optimized reduced aviation fuel-air reaction scheme whose performance in predicting experimental major species profiles and ignition delay times is not only an improvement on the starting reduced mechanism but also on the full mechanism.
Inlet Air Cooling Methods for Gas Turbine Based Power Plants
Authors: Kakaras E. , Doukelis A. , Prelipceanu A. , Karellas S.
Published: April 2006

Background: Power generation from gas turbines is penalized by a substantial power output loss with increased ambient temperature. By cooling down the gas turbine intake air, the power output penalty can be mitigated. Method of Approach: The purpose of this paper is to review the state of the art in applications for reducing the gas turbine intake air temperature and examine the merits from integration of the different air-cooling methods in gas-turbine-based power plants. Three different intake air-cooling, methods (evaporative cooling, refrigeration cooling, and evaporative cooling of precompressed air) have been applied in two combined cycle power plants and two gas turbine plants. The calculations were performed on a yearly basis of operation, taking into account the time-varying climatic conditions. The economics from integration of the different cooling systems were calculated and compared. Results: The results have demonstrated that the highest incremental electricity generation is realized by absorption intake air-cooling. In terms of the economic performance of the investment, the evaporative cooler has the lowest total cost of incremental electricity generation and the lowest payback period (PB). Concerning the cooling method of pre-compressed air, the results show a significant gain in capacity, but the total cost of incremental electricity generation in this case is the highest. Conclusions: Because of the much higher capacity gain by an absorption chiller system, the evaporative cooler and the absorption chiller system may both be selected for boosting the performance of gas-turbine-based power plants, depending on the prevailing requirements of the plant operator.