scholarly journals Modelling of a Dual-Fuel-Mode Free-Jet Combustion System

Aerospace ◽  
2019 ◽  
Vol 6 (12) ◽  
pp. 135
Author(s):  
Maxim Cooper ◽  
Ashish Alex Sam ◽  
Apostolos Pesyridis
Keyword(s):  
Combustion Chamber ◽  
Primary Objective ◽  
Future Research ◽  
Combustion System ◽  
Commercial Aircraft ◽  
Dual Mode ◽  
Propulsion Systems ◽  
Hypersonic Propulsion ◽  
Free Jet ◽  
Chamber Design

The focus of this study is to design a combustion system able to sustain hypersonic flight at Mach 8. A Dual-Mode Free-Jet combustion chamber design, first tested in 2010 by NASA, is being adapted to run on hydrogen fuel instead of ethylene while addressing the excessive thermal heat load. This study is part of the FAME (Flight at Mach Eight) project, with the primary objective to design and analyse the engine configuration for a hypersonic commercial aircraft. This CFD analysis and validation study, the first to replicate this combustion chamber design, provides detailed instructions on the combustion system design. The analysis from this study can be used for future research to successfully reach a sustainable design and operation of a Dual-Mode Free-Jet combustion chamber. The 53% size reduction in the combustion system represents significant progress which encourages future research regarding in the design of combustion systems for hypersonic propulsion systems.

Research and development of an advanced combustion system for the direct injection diesel engine

2005 ◽  
Vol 219 (2) ◽  
pp. 241-252 ◽  
Author(s):  
W H Su ◽  
T J Lin ◽  
H Zhao ◽  
Y Q Pei
Keyword(s):  
Diesel Engine ◽  
Combustion Chamber ◽  
Direct Injection ◽  
Combustion System ◽  
Multiple Injections ◽  
Hcci Combustion ◽  
Advanced Combustion ◽  
Chamber Design ◽  
Low Load ◽  
Di Diesel Engine

In order to obtain a simultaneous reduction in both NOx and particulate emissions from a direct injection (DI) diesel engine, an advanced combustion system has been researched and developed in the authors' laboratory. The new combustion system comprises homogeneous charge compression ignition (HCCI) combustion at low load by early and multiple injections, combined HCCI, and lean diffusion burning at medium and higher load conditions by means of a novel combustion chamber design and multiple injections. In this paper, the research and development of the enhanced mixing by means of a raised round object (referred to in this paper as BUMP) and its application to a diesel combustion chamber design is described. Then the experimental results from a DI diesel engine equipped with a multiple injection common rail (CR) fuel injection system and the new combustion chamber design will be presented and discussed. Engine testing has shown that the BUMP combustion chamber was very effective in reducing both NOx and smoke emissions. HCCI combustion by means of multiple injections leads to extremely low NOx emissions under low load operations. At medium and higher load operation conditions, quasi HCCI combustion combined with the BUMP combustion chamber could signficantly reduce NOx emissions without sacrificing particulate emission and fuel consumption.

Corporate Fraud Prevention and Detection: Revisiting the Literature

2015 ◽  
Vol 4 (1) ◽  
Author(s):  
Deepa Mangala ◽  
Pooja Kumari
Keyword(s):  
Fraud Detection ◽  
Primary Objective ◽  
Future Research ◽  
Business Organization ◽  
Corporate Fraud ◽  
Top Executives ◽  
Red Flag ◽  
Worldwide Phenomenon ◽  
Research Gap ◽  
Prevention Methods

Fraud has become a worldwide phenomenon and prime issue of concern. It dwells in all countries and affects all types of organizations irrespective of their size, profitability or industry. The primary objective of this paper is to provide an in-depth understanding of literature related to corporate fraud in order to understand why fraud occurs and how to combat it. Research studies published during the period commencing from the year 1984 to 2014 have been reviewed. The study aims to provide an in-depth discussion on significant red flags that may exist before fraud occurrence. It, also, provides a comprehensive view about fraud detection and prevention methods. Findings reveal that red flag is an important mechanism to prevent fraud. Application of single fraud detection technique will not curb the fraud effectively. Also, the top executives were found to be responsible for implementing anti-fraud policies and techniques within business organization. Further, the present study tries to discern the research gap in existing literature and explore the area of future research.

scholarly journals Decision Making from the Experience of Orthognathic Surgery Patients: A Grounded Theory Approach

2021 ◽  
pp. 238008442110144
Author(s):  
N.R. Paul ◽  
S.R. Baker ◽  
B.J. Gibson
Keyword(s):  
Decision Making ◽  
Grounded Theory ◽  
Treatment Options ◽  
Study Data ◽  
Primary Objective ◽  
Major Surgery ◽  
Future Research ◽  
Decision Making Process ◽  
Theory Approach

Introduction: Patients’ decisions to undergo major surgery such as orthognathic treatment are not just about how the decision is made but what influences the decision. Objectives: The primary objective of the study was to identify the key processes involved in patients’ experience of decision making for orthognathic treatment. Methods: This study reports some of the findings of a larger grounded theory study. Data were collected through face-to-face interviews of patients who were seen for orthognathic treatment at a teaching hospital in the United Kingdom. Twenty-two participants were recruited (age range 18–66 y), of whom 12 (male = 2, female = 10) were 6 to 8 wk postsurgery, 6 (male = 2, female = 4) were in the decision-making stage, and 4 (male = 0, female = 4) were 1 to 2 y postsurgery. Additional data were also collected from online blogs and forums on jaw surgery. The data analysis stages of grounded theory methodology were undertaken, including open and selective coding. Results: The study identified the central role of dental care professionals (DCPs) in several underlying processes associated with decision making, including legitimating, mediating, scheduling, projecting, and supporting patients’ decisions. Six categories were related to key aspects of decision making. These were awareness about their underlying dentofacial problems and treatment options available, the information available about the treatment, the temporality of when surgery would be undertaken, the motivations and expectation of patients, social support, and fear of the surgery, hospitalization, and potentially disliking their new face. Conclusion: The decision-making process for orthognathic treatment is complex, multifactorial, and heavily influenced by the role of DCPs in patient care. Understanding the magnitude of this role will enable DCPs to more clearly participate in improving patients’ decision-making process. The findings of this study can inform future quantitative studies. Knowledge Transfer Statement: The results of this study can be used both for informing clinical practice around enabling decision making for orthognathic treatment and also for designing future research. The findings can better inform clinicians about the importance of their role in the patients’ decision-making process for orthognathic treatment and the means to improve the patient experience. It is suggested that further research could be conducted to measure some of the key constructs identified within our grounded theory and assess how these change during the treatment process.

Siemens SGT-800 Industrial Gas Turbine Enhanced to 50MW: Combustor Design Modifications, Validation and Operation Experience

2013 ◽  
Author(s):  
Daniel Lörstad ◽  
Annika Lindholm ◽  
Jan Pettersson ◽  
Mats Björkman ◽  
Ingvar Hultmark
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Cooling System ◽  
Good Condition ◽  
Combined Cycle ◽  
Combustion Stability ◽  
Combustion System ◽  
Design Work ◽  
Engine Operation ◽  
Cooling Air

Siemens Oil & Gas introduced an enhanced SGT-800 gas turbine during 2010. The new power rating is 50.5MW at a 38.3% electrical efficiency in simple cycle (ISO) and best in class combined-cycle performance of more than 55%, for improved fuel flexibility at low emissions. The updated components in the gas turbine are interchangeable from the existing 47MW rating. The increased power and improved efficiency are mainly obtained by improved compressor airfoil profiles and improved turbine aerodynamics and cooling air layout. The current paper is focused on the design modifications of the combustor parts and the combustion validation and operation experience. The serial cooling system of the annular combustion chamber is improved using aerodynamically shaped liner cooling air inlet and reduced liner rib height to minimize the pressure drop and optimize the cooling layout to improve the life due to engine operation hours. The cold parts of the combustion chamber were redesigned using cast cooling struts where the variable thickness was optimized to maximize the cycle life. Due to fewer thicker vanes of the turbine stage #1, the combustor-turbine interface is accordingly updated to maintain the life requirements due to the upstream effect of the stronger pressure gradient. Minor burner tuning is used which in combination with the previously introduced combustor passive damping results in low emissions for >50% load, which is insensitive to ambient conditions. The combustion system has shown excellent combustion stability properties, such as to rapid load changes and large flame temperature range at high loads, which leads to the possibility of single digit Dry Low Emission (DLE) NOx. The combustion system has also shown insensitivity to fuels of large content of hydrogen, different hydrocarbons, inerts and CO. Also DLE liquid operation shows low emissions for 50–100% load. The first SGT-800 with 50.5MW rating was successfully tested during the Spring 2010 and the expected performance figures were confirmed. The fleet leader has, up to January 2013, accumulated >16000 Equivalent Operation Hours (EOH) and a planned follow up inspection made after 10000 EOH by boroscope of the hot section showed that the combustor was in good condition. This paper presents some details of the design work carried out during the development of the combustor design enhancement and the combustion operation experience from the first units.

Numerical Simulation of Supersonic Combustion in Quasi One-Dimensional Flow

1991 ◽  
Author(s):  
T. Gary Yip
Keyword(s):  
Flow Model ◽  
Cone Angle ◽  
Initial Pressure ◽  
Supersonic Combustion ◽  
Propulsion Systems ◽  
One Dimensional ◽  
Hypersonic Propulsion ◽  
Dimensional Flow ◽  
Conical Shock ◽  
Shock System

Abstract Supersonic combustion induced by a two-shock system has been studied using a chemical nonequilibrium, quasi one-dimensional flow model. The combustion of stoichiometric, premixed H2-air is described by a chemistry model which consists of 11 species and 28 reactions. The freestream Mach numbers used in this calculations are 8, 10 and 12. The initial pressure is 0.01 atm and temperature 300 K. The first of the two shocks is a conical shock and the second is its reflection. Supersonic combustion has been predicted to occur at combustor pressures between 0.8 and 2.9 atmospheres, and temperatures between 1500 and 3000 K. The Mach number of the flow in the combustor is between 1.7 and 4. These combustor conditions are typical of the future hypersonic propulsion systems. The results also show the changes in the composition of the flow during the induction and heat release phases. The two-shock system is assumed to be generated by a cone. For Mach 8, 10 and 12, the minimum cone angle for generating a strong enough two-shock system to induce supersonic combustion has also been identified.

The Correlation between Servqual Dimensions and Student Satisfaction

2021 ◽  
Vol 7 (2) ◽  
pp. 7
Author(s):  
Nur Zihan Abd Rashid ◽  
Tuan Nur Athirah Nabilah Tuan Ismail ◽  
Bibianah Thomas
Keyword(s):  
Higher Education ◽  
Service Quality ◽  
Student Satisfaction ◽  
Learning Experience ◽  
Sampling Technique ◽  
Education Institution ◽  
Primary Objective ◽  
Future Research ◽  
Higher Education Institution ◽  
New Findings

Service quality is a very crucial element in ensuring the competitiveness of various institutions. By having a good service quality, the reputation of the organization will enhance and thus become their added competitive advantage. In higher education institution, service quality is important to ensure the students whom are their primary stakeholders are able to have a good learning experience in which will then influence their satisfaction. The primary objective of this paper is to analyze the correlation between five elements in SERVQUAL dimensions (tangibility, reliability, responsiveness, assurance, empathy) and the student satisfaction. The questionnaires were distributed among the students in various faculties in UiTM Sabah by using convenience sampling technique and 250 questionnaires were managed to be collected for analysis. Overall, the result shows that the students are satisfied with service quality in UiTM Sabah. Specifically, all five SERVQUAL dimensions correlate with student satisfaction. Reliability, responsiveness and empathy dimensions have strong correlation with student satisfaction. Meanwhile, both tangibility and assurance have moderate correlation with student satisfaction. This study is hoped to contribute towards the new knowledge in the field of service quality especially in higher education institutions Future research is also proposed at the final section of this study to discover new findings from different perspectives of service quality. Keywords: servqual; students’ satisfaction; service quality; higher education institution; service delivery.

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