CFD Study on the Influence of Geometric Parameters on the Aerodynamics Within an Ejector Injection System for Compressor Stabilization

2018 ◽  
Author(s):  
Sebastian Brehm ◽  
Felix Kern ◽  
Reinhard Niehuis
Keyword(s):  
Mass Flow ◽  
Armed Forces ◽  
Injection System ◽  
Parameter Study ◽  
Entrainment Ratio ◽  
Node Number ◽  
Nozzle Height ◽  
Secondary Air ◽  
Icem Cfd ◽  
The University

Injection of high-momentum air into the tip-gap region of rotor stages is a measure of active aerodynamic stabilization of turbo compression systems. The Institute of Jet Propulsion at the University of the German Federal Armed Forces Munich advanced the concept of conventional tip air injection by deliberately deploying the ejector effect in order to increase the mass flow rate of the air injected. A novel Ejector Injection System (EIS) has been developed for the Larzac 04 jet engine and its intended ejector performance was proven in experimental pre-investigations. In addition to that, the corresponding CFD setup has been validated and an approach for highly efficient CFD simulations of the EIS ejector aerodynamics (node number reduction > 90%) was developed, verified, and validated. Thus, optimization of the ejector geometry in order to enhance the ejector aerodynamics and subsequently the stabilization performance of the EIS comes into focus now. Within this paper, a parametric CFD study is conducted to determine the influence of three main geometry parameters of the EIS ejector design on the ejector’s performance. The parameters, namely the injection nozzle spacing, the mixing duct length, and the ejector nozzle height, are introduced in the context of the overall EIS design and functionality. For efficiency purposes, a script-based procedure which deploys ANSYS ICEM CFD and ANSYS CFX has been developed in order to conduct the CFD parameter study covering 205 simulations fully automated. Each ejector geometry is thereby simulated with five different primary air mass flow rates supplied to the EIS covering a range from low-speed to transonic operation. It is revealed that all three geometry parameters investigated show partially significant impact on the ejector performance in terms of the entrainment ratio μ. In order to get a detailed insight into the inner EIS aerodynamics, also primary air Mach and Reynolds numbers, the state of mixing between primary and secondary air, and velocity profiles in the LPC’s tip region are subjects of investigation. Based on these findings and the general aerodynamic coherences discovered, recommendations for optimizing the current EIS ejector design are presented.

How to measure the radial load of radial lip seals

2021 ◽  
Vol 68 (3-4) ◽  
pp. 5-12
Author(s):  
Simon Feldmeth ◽  
Mario Stoll ◽  
Frank Bauer
Keyword(s):  
Practice Guideline ◽  
Best Practice ◽  
Parameter Study ◽  
Radial Load ◽  
Measurement Device ◽  
Lip Seal ◽  
Study Results ◽  
Lip Seals ◽  
German Standard ◽  
The University

The radial load of a radial lip seal indicates how strongly the sealing lip is pressed on the shaft. The radial load significantly affects the function of the seal. The German standard DIN 3761-9 describes the measurement of the radial load according to the split-shaft method but leaves room for interpretation. During the revision of the standard, a parameter study was conducted at the University of Stuttgart. This study analyses the influence of the measurement device, the mandrels and the measuring procedure on the results. Based on the study results, recommendations are derived and summarized in a best-practice guideline, which should enable an appropriate and reproducible measurement of the radial load.

Scavenging of Two Stroke Petrol Engine by Using Secondary Air Injection System

2019 ◽  
pp. 913-922
Author(s):  
Sagar Namdev Khurd ◽  
U. B. Andh ◽  
S. V. Kulkarni ◽  
Sandeep S. Wangikar ◽  
P. P. Kulkarni
Keyword(s):  
Air Injection ◽  
Petrol Engine ◽  
Injection System ◽  
Secondary Air Injection ◽  
Secondary Air

An Approach for Efficient CFD Simulations of an Ejector Air Injection System for Active Aerodynamic Compressor Stabilization

2017 ◽  
Author(s):  
Sebastian Brehm ◽  
Felix Kern ◽  
Jonas Raub ◽  
Reinhard Niehuis
Keyword(s):  
Large Scale ◽  
Armed Forces ◽  
Air Injection ◽  
Injection System ◽  
Cfd Simulations ◽  
Data Set ◽  
Numerical Effort ◽  
Enhance Efficiency ◽  
Set Up ◽  
Novel Concept

The Institute of Jet Propulsion at the University of the German Federal Armed Forces Munich has developed and patented a novel concept of air injection systems for active aerodynamic stabilization of turbo compressors. This so-called Ejector Injection System (EIS) utilizes the ejector effect to enhance efficiency and impact of the aerodynamic stabilization of the Larzac 04 two-spool turbofan engine’s LPC. The EIS design manufactured recently has been subject to CFD and experimental pre-investigations in which the expected ejector effect performance has been proven and the CFD set-up has been validated. Subsequently, optimization of the EIS ejector geometry comes into focus in order to enhance its performance. In this context, CFD parameter studies on the influence of in total 16 geometric and several aerodynamic parameters on the ejector effect are required. However, the existing and validated CFD set-up of the EIS comprises not only the mainly axisymmetric ejector geometry but also the highly complex 3D supply components upstream of the ejector geometry. This is hindering large scale CFD parameter studies due to the numerical effort required for these full 3D CFD simulations. Therefore, an approach to exploit the overall axissymmetry of the ejector geometry is presented within this paper which reduces the numerical effort required for CFD simulations of the EIS by more than 90%. This approach is verified by means of both experimental results as well as CFD predictions of the full 3D set-up. The comprehensive verification data set contains wall pressure distributions and the mass flow rates involved at various Aerodynamic Operating Points (AOP). Furthermore, limitations of the approach are revealed concerning its suitability e.g. to judge the response of the attached compressor of future EIS designs concerning aerodynamic stability or cyclic loading.

Performance of Strongly Bowed Stators in a Four-Stage High-Speed Compressor

2004 ◽  
Vol 126 (3) ◽  
pp. 333-338 ◽  
Author(s):  
Axel Fischer ◽  
Walter Riess ◽  
Joerg R. Seume
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Maximum Pressure ◽  
Controlled Diffusion ◽  
Stage 4 ◽  
The University

The FVV sponsored project “Bow Blading” (cf. acknowledgments) at the Turbomachinery Laboratory of the University of Hannover addresses the effect of strongly bowed stator vanes on the flow field in a four-stage high-speed axial compressor with controlled diffusion airfoil (CDA) blading. The compressor is equipped with more strongly bowed vanes than have previously been reported in the literature. The performance map of the present compressor is being investigated experimentally and numerically. The results show that the pressure ratio and the efficiency at the design point and at the choke limit are reduced by the increase in friction losses on the surface of the bowed vanes, whose surface area is greater than that of the reference (CDA) vanes. The mass flow at the choke limit decreases for the same reason. Because of the change in the radial distribution of axial velocity, pressure rise shifts from stage 3 to stage 4 between the choke limit and maximum pressure ratio. Beyond the point of maximum pressure ratio, this effect is not distinguishable from the reduction of separation by the bow of the vanes. Experimental results show that in cases of high aerodynamic loading, i.e., between maximum pressure ratio and the stall limit, separation is reduced in the bowed stator vanes so that the stagnation pressure ratio and efficiency are increased by the change to bowed stators. It is shown that the reduction of separation with bowed vanes leads to a increase of static pressure rise towards lower mass flow so that the present bow bladed compressor achieves higher static pressure ratios at the stall limit.

scholarly journals Telepathology in the Philippines: A Review and Future Prospects

2016 ◽  
Vol 50 (4) ◽  
Author(s):  
Elizabeth R. Arcellana-Nuqui ◽  
Paul A. Fontelo ◽  
Alvin B. Marcelo
Keyword(s):  
Armed Forces ◽  
The Philippines ◽  
Underserved Population ◽  
Future Prospects ◽  
Remote Areas ◽  
Human Capacity ◽  
The University ◽  
Conducive Environment ◽  
Insufficient Number

Background. Challenged with insufficient number and maldistribution of pathologists, the Philippines seemed poised to benefit from telemedicine. Methods. The first modern Internet-based telepathology consultation was conducted between the University of the Philippines Manila and the Armed Forces Institute of Pathology in 1997. Results. While the first remote telepathology consult was a success, more than a decade after this historic referral, telepathology remains in the fringes of mainstream pathology practice despite its huge potential to benefit the underserved population. Challenges with human, organizational, and technology factors hinder its progress. Conclusions. While the original consultation faced difficulties in human capacity, connectivity and infrastructure, rapid developments in governance and technology have the potential to eliminate these problems. Substantial improvements in recent years now provide a more conducive environment to deliver telepathology services to remote areas. This paper proposes a framework for the establishment of mature telepathology services to enable its use in areas of greatest need in the country.

Development of a Method to Evaluate CNG-Injection Valves

2015 ◽  
Author(s):  
Christian von Grabe ◽  
David van Bebber ◽  
Hubertus Murrenhoff
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Test Chamber ◽  
Combustion Process ◽  
Test Method ◽  
Injection System ◽  
Time Behavior ◽  
Gaseous Fuels ◽  
Injection Process

The development of combustion engines with direct injection requires a comprehensive knowledge of the in cylinder combustion process as well as the used high pressure injection system. One main characteristic of injection systems is their mass flow over time behavior. For prevalent diesel and gasoline injection valves (injectors) fully developed simulation models as well as test benches are available to analyze the injection process. Besides the established engines a trend towards compressed natural gas (CNG) engines in passenger cars is recognized. Due to the small injection duration of a few milliseconds, the flow rate measurement is particularly challenging and requires highly dynamic measuring. The existing test benches are designed and optimized for liquid fuels and are only partly suitable for the evaluation of gaseous fuels such as CNG. A typical test method is to inject fuel into a long tube in which a pressure wave propagates. Based on the pressure signal the mass flow of the injected fuel is approximated. For gaseous fuels the correlation of mass flow and pressure propagation is only known for specific test cases and therefore the method is not directly applicable to gaseous fuels. This paper presents a newly designed measurement device to evaluate the mass flow rate as well as the injector needle displacement during an injection process of gaseous fuels. The test bench is designed to operate in a fully equipped injection system including gas lines, common rail and injection valves, to also investigate the interaction of the individual system components. The design is based on a closed test chamber in which the pressure rises during the injection. To overcome the influence of propagating pressure waves inside the chamber on the measurement, different chamber designs are evaluated. An optimized design, separating the chamber into two volumes which are connected by a damping sleeve, is presented. The injection itself is carried out in a first volume and the measurement is conducted in a second damped volume. Based on the measured pressure the mass flow rate through the injection valve is approximated, utilizing the equations of thermodynamics.

Freund-Feind-Denken

2021 ◽  
Keyword(s):  
Armed Forces ◽  
State Theory ◽  
Carl Schmitt ◽  
Professor Emeritus ◽  
The Political ◽  
Political Sphere ◽  
Relevant Today ◽  
German Armed Forces ◽  
The One ◽  
The University

Carl Schmitt emphasised the crucial importance of the friend–enemy dichotomy for the political sphere. Is the connection between the concept of the enemy and politics still relevant today? Or does the political sphere need to be defined quite differently, on the one hand, and does the problem of enmity need to be dealt with beyond the political sphere, on the other? Since the publication of this book’s 1st edition, the issue of ‘enmity’ has by no means been settled, as recent terrorist attacks have shown. On the contrary, hatred of those who think differently seems to be on the increase, and they are then demonised as ‘enemies’. This development is explored in the contributions to the book’s 2nd edition. Rüdiger Voigt, professor emeritus of administrative science at the University of the German Armed Forces in Munich, is the author and editor of numerous books on state theory and state practice.

Charles R. Scoggin, 1914-1944

1944 ◽  
Vol 10 (2) ◽  
pp. 198-201
Author(s):  
Frank H. H. Roberts
Keyword(s):  
United States ◽  
High School ◽  
Formal Education ◽  
Armed Forces ◽  
The United States ◽  
University Of Colorado ◽  
The Hours ◽  
The Many ◽  
The University

Among the many student archaeologists serving in the armed forces of the United States, one of the first to make the supreme sacrifice was 1st Lieutenant Charles R. Scoggin. He was killed in action on Anzio beachhead, Italy, Feb. 2, 1944.Lieutenant Scoggin, son of Dr. W. J. and Essie (Cartwright) Scoggin, was born July 10, 1914, at Bridgeport, Nebraska. He received his preliminary schooling at Chula Vista, California, and in 1927 moved with his parents to Ovid, Colorado, where he attended high school, graduating in 1931. Because of the depression, he was unable to continue his formal education at that time and in 1933 moved with his family to nearby Julesburg, Colorado. He was employed at Julesburg until the autumn of 1935 when he enrolled in the University of Colorado at Boulder. As it was necessary for him to work his way through college his attendance was irregular and he had not completed the hours requisite to a-degree when the tide of world events swept him on to grimmer tasks in the summer of 1942.

Analytical Modeling and Experimental Validation of Heating at the Leaf Seal/Rotor Interface

2016 ◽  
Vol 139 (4) ◽  
Author(s):  
Michael J. Pekris ◽  
Gervas Franceschini ◽  
Andrew K. Owen ◽  
Terry V. Jones ◽  
David R. H. Gillespie
Keyword(s):  
Mass Flow Rate ◽  
Analytical Model ◽  
Mass Flow ◽  
Flow Rate ◽  
Temperature Rise ◽  
Thermal Characteristic ◽  
Frictional Heat ◽  
Test Facility ◽  
Engine Operation ◽  
Secondary Air

The secondary air system of a modern gas or steam turbine is configured to satisfy a number of requirements, such as to purge cavities and maintain a sufficient flow of cooling air to key engine components, for a minimum penalty on engine cycle efficiency and specific fuel consumption. Advanced sealing technologies, such as brush seals and leaf seals, are designed to maintain pressures in cavities adjacent to rotating shafts. They offer significant reductions in secondary air parasitic leakage flows over the legacy sealing technology, the labyrinth seal. The leaf seal comprises a series of stacked sheet elements which are inclined relative to the radial direction, offering increased axial rigidity, reduced radial stiffness, and good leakage performance. Investigations into leaf seal mechanical and flow performance have been conducted by previous researchers. However, limited understanding of the thermal behavior of contacting leaf seals under sustained shaft contact has led to the development of an analytical model in this study, which can be used to predict the power split between the leaf and rotor from predicted temperature rises during operation. This enables the effects of seal and rotor thermal growth and, therefore, implications on seal endurance and rotor mechanical integrity to be quantified. Consideration is given to the heat transfer coefficient in the leaf pack. A dimensional analysis of the leaf seal problem using the method of extended dimensions is presented, yielding the expected form of the relationship between seal frictional power generation, leakage mass flow rate, and rotor temperature rise. An analytical model is derived which is in agreement. Using the derived leaf temperature distribution formula, the theoretical leaf tip temperature rise and temperature distributions are computed over a range of mass flow rates and frictional heat values. Experimental data were collected in high-speed tests of a leaf seal prototype using the Engine Seal Test Facility at Oxford University. These data were used to populate the analytical model and collapsed well to confirm the expected linear relationship. In this form, the thermal characteristic can be used with predictions of mass flow rate and frictional power generated to estimate the leaf tip and rotor temperature rise in engine operation.

Development of a Model for the Simulation of a Reed Valve Based Secondary Air Injection System for SI Engines

2005 ◽  
Author(s):  
Michele Battistoni ◽  
Carlo N. Grimaldi ◽  
Riccardo Baudille ◽  
Marcello Fiaccavento ◽  
Maurizio Marcacci
Keyword(s):  
Air Injection ◽  
Injection System ◽  
Secondary Air Injection ◽  
Si Engines ◽  
Secondary Air ◽  
Reed Valve
Sign in / Sign up

Export Citation Format

Share Document