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This paper presents the model of heat exchanger dedicated to operate in supercritical CO2 cycles (Brayton). The models is built in the Ebsilon software and validated against literature available experimental data. Relatively compact design of the supercritical CO2 cycle elements required using radial turbomachinery and thin plate heat exchangers. Thus, it seems that there is no general relationships for the turbomachinery and real characteristics need to be used for constructing the models.

Global trend to distributed energy generation results in growing interest to efficient, compact and autonomous small-scale energy equipment. One of the best and proven solutions available for power range below 1MW is high-speed oil-free turbomachines with foil bearings. Such maintenance-free energy systems life-time is mostly determined by proper design of bearing and cooling systems. At prototype development stage various layouts should be analyzed to select the best configuration for given customer. Thus fast and reasonably accurate estimation of heat loads is more important than time-consuming determination of precise values. Bearing system is one of the main sources of heat in small-scale high speed turbomachines. Despite intensive experimental and numerical investigation of various foil bearing configurations performance parameters there are no proven correlations for friction losses available in open sources. In order to solve to some extent this problem simple first-principle based scaling procedure for friction losses in radial and axial-thrust bearings estimation is proposed. Presented approach allows recalculating experimentally measured foil bearing performance parameters to any arbitrary geometry and operation conditions using dimensionless analysis of friction losses and load capacity. Average deviation from available experimental data is within 10-15% range that is acceptable for initial prototyping of bearing and cooling systems.

This paper presents the model of heat exchanger dedicated to operate in supercritical CO2 cycles (Brayton). The models is built in the EBSILON software and validated against literature available experimental data. Relatively compact design of the supercritical CO2 cycle elements required using radial turbomachinery and thin plate heat exchangers. Thus, it seems that there is no general relationships for the turbomachinery and real characteristics need to be used for constructing the models.

Creating the modern gas turbine engines is impossible without using numerical methods for analyzing gas dynamics and heat transfer. Improvement of thermal calculations requires the use of mathematical modeling methods to obtain information on the distribution of temperature fields in the blade. The application of numerical simulation is necessary to determine the interaction of viscous and inviscid flows, turbulent heat transfer under favorable and unfavorable pressure gradients, heat transfer in rotating channels, separation of the boundary layer, etc. The ways of increasing the economy of operation of modern gas turbines are considered, including by developing software and information systems for analyzing the thermal state of the turbomachine blades and using the latest research in the field of gas dynamics.Creating the modern gas turbine engines is impossible without using numerical methods for analyzing gas dynamics and heat transfer. Improvement of thermal calculations requires the use of mathematical modeling methods to obtain information on the distribution of temperature fields in the blade. The application of numerical simulation is necessary to determine the interaction of viscous and inviscid flows, turbulent heat transfer under favorable and unfavorable pressure gradients, heat transfer in rotating channels, separation of the boundary layer, etc. The ways of increasing the economy of operation of modern gas turbines are considered, including by developing software and information systems for analyzing the thermal state of the turbomachine blades and using the latest research in the field of gas dynamics.

Air filtration system plays an important role in getting good quality air into turbo machinery such as gas turbine. The filtration system and filters improve the quality of air and protect the gas turbine parts from contaminants which could bring damage. This paper is focused on the configuration of the self-cleaning canister filter in order to obtain the minimal pressure drop along the filter. The configuration includes a modified canister filter cap that is based on the basic geometry that conforms to industry standard. This paper describes the use of CFD to simulate and analyze the flow through the filter. This tool is also used to monitor variables such as pressure and velocity along the filter and to visualize them in the form of contours, vectors and streamlines. In this study, the main parameter varied is the inlet velocity set in the boundary condition during simulations, which are 0.032, 0.063, 0.094 and 0.126 m/s respectively. The data obtained from simulations are then validated with reference ...

This paper focuses on measurements of 3D Operating Deflection Shapes (ODSs), and subsequently, construction of full-field surface strain maps of a number of turbomachinery components. For this purpose a 3D Scanning Laser Doppler Vibrometer (SLDV) is used. The ODS measurements are performed for a large number of modes and results obtained are compared with the 1-D shapes that are most commonly measured. It is demonstrated that the 3D measurements are a significant improvement over the 1-D case in terms of independent amount of extra information they provide. This is confirmed through comparisons with FE results. Special tests are carried out to recover the full-field strain on scanned faces of the components used. Visual comparison of these measurements with FE counterparts reveal that strain maps can be successfully measured, not only for low frequency modes but also for highly complex high frequency ones. These maps are measured with different levels of input force to assess the linearity of strain results to varying response amplitudes. Lessons learnt and observations made are summarised in concluding remarks and the scope of future work to take this study into the production environment is discussed. This study constitutes a unique comprehensive investigation into full-field strain measurements using real application hardware and a large frequency range.

The paper deals with electromagnetic sensors for noncontact vibration diagnostics in rotating machinery. The sensors were designed for operational measurements in turbomachinery by means of the tip-timing method. The main properties of eddy-current, Hall effect, induction and magnetoresistive sensors are described and compared. Possible arrangements of the experimental systems for static and dynamic calibration of the sensors are suggested and discussed.

The structural integrity of blades is critical to the health of turbomachinery. Since operational failure of these blades can possibly lead to catastrophic failure of the machine, it is important to have knowledge of blade conditions in an online fashion. Due to several practical implications, it is desired to measure blade vibration with a non-contact technique. The application of laser Doppler vibrometry towards the vibration based condition monitoring of axial-flow turbomachinery blades has been successfully demonstrated in previous work. In this paper the feasibility of using laser Doppler vibrometry to measure radial-flow turbomachinery blade vibrations is investigated with the aid of digital image correlation and strain gauge telemetry.

Effectively and accurately detecting cracks or defects in critical engine components, such as turbine engine blades, is very important for aircraft safety. Sonic Infrared (IR) Imaging is such a technology with great potential for these applications. This technology combines ultrasound excitation and IR imaging to identify cracks and flaws in targets. In general, failure of engine components, such as blades, begins with tiny cracks. Since the attenuation of the ultrasound wave propagation in turbine engine blades is small, the efficiency of crack detection in turbine engine blades can be quite high. The authors at Wayne State University have been developing the technology as a reliable tool for the future field use in aircraft engines and engine parts. One part of the development is to use finite element modeling to assist our understanding of effects of different parameters on crack heating while experimentally hard to achieve. The development has been focused with single frequency ultrasound excitation and some results have been presented in a previous conference. We are currently working on multi-frequency excitation models. The study will provide results and insights of the efficiency of different frequency excitation sources to foster the development of the technology for crack detection in aircraft engine components.

The cross flow fan is a unique type of turbo machinery where the air stream flows transversely across the impeller, passing the blades twice. Due to its complex geometry, and highly turbulent and unsteady air-flow, a numerical method is used in this work to conduct the characterization study on the performance of a cross flow fan. A 2D cross-sectional model of a typical indoor air conditioning unit has been chosen for the simulation instead of a three dimensional 3D model due to the highly complex geometry of the fan. The simplified 2D model has been validated with experiments where it is found that the RMS error between the simulation and experimental results is less than 7%. The important parameters that affect the cross flow fan performance, i.e. the internal and external blade angles, the blade thickness, and the casing design, are analyzed in this study. The formation of an eccentric vortex is observed within the impeller.

The utilization of turbomachines requires up-to-date technologies to ensure safe operation throughout the widest possible range that makes novel ideas necessary to cope with classic problems. One of the most dangerous instability in compression systems is surge that has to be suppressed before its onset to avoid structural damages as well as other adverse consequences in the system. As surge occurs at low delivered mass flow rates the conventional widely spread surge control is based on bypassing the unnecessary airflow back to the atmosphere. This method has been implemented on a large number of aircraft and provides a robust control on suppressing compressor surge while creating a significant efficiency loss. This paper deals with an idea that has been originally designed as a fixed geometry that could be realized using up-to-date MEMS technology resulting in moderate losses but comparable stability enhancement. Previously the author has established the one-dimensional mathematical model of the concept,...

A three‐dimensional (3D) Navier‐Stokes method is applied to calculate unsteady turbomachinery flows. The 4‐stage Runge‐Kutta time‐marching scheme and time‐consistent multi‐grid technique are adopted in the calculations. In this study, the multi‐passage computation and single passage computation are performed on the actual and scaled configurations respectively. The results from multi‐passage computation and singe passage computations are compared. Results in the form of isentropic efficiency, mass flow, entropy and unsteady aerodynamic force on the blades are presented. It has been found that the blade geometry scaling changes the axial position of the wakes, which leads to greater amplitude of efficiency fluctuation. The blade geometry scaling brings notable effects on the first four harmonics of unsteady tangential force.

Waviness in glass fiber reinforced composite is of great interest in composite research, since it results in the loss of stiffness. Several NDE techniques have been used previously to detect waviness. This work is concerned with waves normal to the plies in a composite. Air‐coupled ultrasonics was used to detect waviness in thick composites used in the manufacturing of wind turbine blades. Composite samples with different wave aspect ratios were studied. Different wavy samples were characterized, and a three step process was developed to make sure the technique is field implementable. This gives us a better understanding of the effect of waviness in thick composites, and how it affects the life and performance of the composite.

The best efficiency point is ideal operational point for any turbomachinery. Selections of turbomachines in industry such as pump, turbine, compressor, etc are basically based on their operating point. The best efficiency point is a point at the highest efficiency. Therefore, turbomachines with nearest operating point to best efficiency point will be chosen due to higher efficiency thus produce great reduction in cost saving. Different speed of rotor blade will cause effect to the best efficiency point, as well as different in rotor and stator blade angle. If angle of rotor and stator blade constant while speed of rotor blade increased, the net head produced by the compressor will also increased. Thus, it will increase the brake horse power and fluid horse power. Although the efficiency of the compressor increases if fluid horse power increased, the increasing in brake horse power will produce lower efficiency. In this paper, the effect of rotor blade speed on best efficiency point of an axial flow compre...

The erosion resulting from sand ingestion into an axial turbomachinery is predicted using a Lagrangian particle tracking model. This simulation takes into account the effects of turbulence and endwalls vorticities on particles, random size distribution and rebound of particles. The governing equations of particle motion through stationary and rotating parts are solved in a stepwise manner separately from the flow field. Particles tracking and impacts are predicted in different cells of the computational domain based on the finite element method. A semi‐empirical erosion correlation is used to predict erosion areas based on impacts condition. The simulations results obtained for different positions of the rotor blade revealed that the main impacted areas are found over the blade leading edge corner and an area of the pressure side extending towards and over the tip, in addition to a strip along the leading edge of the suction side.

For the next leap in the sustainable energy exploitations, we are under obligations not only to cope with the warming global environment but also to conserve natural ecosystems and to coexist with natures. This paper introduces the following advanced technologies in Kyushu Institute of Technology, to utilize effectively the promising ocean and wind resources at the offshore. (1) Counter‐Rotating Type Reversible Hydroelectric Unit, which is composed of the tandem runners and the peculiar generator with the double rotational armatures, is applicable to both rising and falling tides at the power station with the embankment, in place of the traditional bulb type turbines. (2) Gyro‐Type Reversible Hydraulic Turbine, which is composed of some blades with the high aspect ratio, is effective to utilize the tide power even at the shallow and/or the very low range of the tide. (3) Submerged Ocean Wave Power Unit, where a pair of floats is lined up at the interval of one wave pitch and supports the vertical type hyd...

Hydrogen has been brought into focus of industry and public since fossil fuels are depleting and costs are increasing dramatically. Beside these issues new high‐tech processes in the industry are in need for hydrogen at ultra pure quality. To achieve these requirements and for efficient transportation, hydrogen is liquefied in industrial plants. Linde Gas has commissioned a new 5.5 TPD Hydrogen liquefier in Leuna, Germany, which has been engineered and supplied by Linde Kryotechnik. One of the four expansion turbines installed in the liquefaction process is equipped with dynamic gas bearings. Several design features and operational characteristics of this application will be discussed. The presentation will include results of efficiency and operational reliability that have been determined from performance tests. The advantages of the Linde dynamic gas bearing turbine for future use in hydrogen liquefaction plants will be shown.

Closed Brayton Cycle (CBC) turbine systems are under consideration for future space electric power generation. CBC turbines convert thermal energy from a nuclear reactor, or other heat source, to electrical power using a closed‐loop cycle. The operating fluid in the closed‐loop is commonly a high pressure inert gas mixture that cannot tolerate contamination. One source of potential contamination in a system such as this is the lubricant used in the turbomachine bearings. Gas Foil Bearings (GFB) represent a bearing technology that eliminates the possibility of contamination by using the working fluid as the lubricant. Thus, foil bearings are well suited to application in space power CBC turbine systems. NASA Glenn Research Center is actively researching GFB technology for use in these CBC power turbines. A power loss model has been developed, and the effects of very high ambient pressure, start‐up torque, and misalignment, have been observed and are reported here.

Both NASA and DOE have programs that are investigating advanced power conversion cycles for planetary surface power on the moon or Mars, or for next generation nuclear power plants on earth. Although open Brayton cycles are in use for many applications (combined cycle power plants, aircraft engines), only a few closed Brayton cycles have been tested. Experience with closed Brayton cycles coupled to nuclear reactors is even more limited and current projections of Brayton cycle performance are based on analytic models. This report describes and compares experimental results with model predictions from a series of non‐nuclear tests using a small scale closed loop Brayton cycle available at Sandia National Laboratories. A substantial amount of testing has been performed, and the information is being used to help validate models. In this report we summarize the results from three kinds of tests. These tests include: 1) test results that are useful for validating the characteristic flow curves of the turbomachinery for various gases ranging from ideal gases (Ar or Ar/He) to non‐ideal gases such as CO2, 2) test results that represent shut down transients and decay heat removal capability of Brayton loops after reactor shut down, and 3) tests that map a range of operating power versus shaft speed curve and turbine inlet temperature that are useful for predicting stable operating conditions during both normal and off‐normal operating behavior. These tests reveal significant interactions between the reactor and balance of plant. Specifically these results predict limited speed up behavior of the turbomachinery caused by loss of load, the conditions for stable operation, and for direct cooled reactors, the tests reveal that the coast down behavior during loss of power events can extend for hours provided the ultimate heat sink remains available.

A gas‐cooled reactor may be coupled directly to turbomachinery to form a closed‐Brayton‐cycle (CBC) system in which the CBC working fluid serves as the reactor coolant. Such a system has the potential to be a very simple and robust space‐reactor power system. Gas‐cooled reactors have been built and operated in the past, but very few have been coupled directly to the turbomachinery in this fashion. In this paper we describe the option for testing such a system with a small reactor and turbomachinery at Sandia National Laboratories. Sandia currently operates the Annular Core Research Reactor (ACRR) at steady‐state powers up to 4 MW and has an adjacent facility with heavy shielding in which another reactor recently operated. Sandia also has a closed‐Brayton‐Cycle test bed with a converted commercial turbomachinery unit that is rated for up to 30 kWe of power. It is proposed to construct a small experimental gas‐cooled reactor core and attach this via ducting to the CBC turbomachinery for cooling and electricity production. Calculations suggest that such a unit could produce about 20 kWe, which would be a good power level for initial surface power units on the Moon or Mars. The intent of this experiment is to demonstrate the stable start‐up and operation of such a system. Of particular interest is the effect of a negative temperature power coefficient as the initially cold Brayton gas passes through the core during startup or power changes. Sandia’s dynamic model for such a system would be compared with the performance data. This paper describes the neutronics, heat transfer, and cycle dynamics of this proposed system. Safety and radiation issues are presented. The views expressed in this document are those of the author and do not necessarily reflect agreement by the government.

State-of-the-art closed-Brayton-cycle (CBC) space power systems were modeled to study performance trends in a trade space characteristic of interplanetary orbiters. For working-fluid molar masses of 48.6, 39.9, and 11.9 kg/kmol, peak system pressures of 1.38 and 3.0 MPa and compressor pressure ratios ranging from 1.6 to 2.4, total system masses were estimated. System mass increased as peak operating pressure increased for all compressor pressure ratios and molar mass values examined. Minimum mass point comparison between 72 percent He at 1.38 MPa peak and 94 percent He at 3.0 MPa peak showed an increase in system mass of 14 percent. Converter flow loop entropy generation rates were calculated for 1.38 and 3.0 MPa peak pressure cases. Physical system behavior was approximated using a pedigreed NASA Glenn modeling code, Closed Cycle Engine Program (CCEP), which included realistic performance prediction for heat exchangers, radiators and turbomachinery.

This paper presents a study of the dynamics for a single‐stage, axial‐flow, high speed compressor core, specifically, the NASA Lewis rotor stage 37. Due to the overall blading design for this advanced core compressor, each stage has considerable tip loading and higher speed than most compressor designs, thus, the compressor operates closer to the stall margin. The onset of rotating stall is explained as bifurcations in the dynamics of axial compressors. Data taken from the compressor during a rotating stall event is analyzed. Through the use of a box‐assisted correlation dimension methodology, the attractor dimension is determined during the bifurcations leading to rotating stall. The intent of this study is to examine the behavior of precursive stall events so as to predict the entrance into rotating stall. This information may provide a better means to identify, avoid or control the undersireable event of rotating stall formation in high speed compressor cores.

This paper provides a comparison between full‐flow and conventional staged combustion thermodynamic O2/H2 rocket engine cycles for Reusable Launch Vehicle, RLV, single‐stage‐to‐orbit applications. The impact of the cycle thermodynamics, component configuration, and component operating parameters on engine performance and weight for the two approaches is presented. Both cycles were modeled with equivalent technology turbomachinery and chamber/nozzle RLV life requirements. The first order impact of cycle selection, pump exit pressure, and turbine temperature on the empty weight of an SSTO Reusable Launch Vehicle is presented.

The second phase of development of a Nuclear Thermal Propulsion (NTP) engine system design analysis code has been completed. The standalone, versatile Nuclear Engine System Simulation (NESS) code provides an accurate, detailed assessment of engine system operating performance, weight, and sizes. The critical information is required to support ongoing and future engine system and stage design study efforts. This recent development effort included incorporation of an updated solid‐core nuclear thermal reactor model that yields a reduced core weight and higher fuel power density when compared to a NERVA type reactor. NESS can now analyze expander, gas generator, and bleed cycles, along with multi‐redundant propellant pump feed systems. Performance and weight of efficient multi‐stage axial turbopump can now be determined, in addition to the traditional centrifugal pump.Key code outputs include reactor operating charactertistics and weights and well as engine system parameters such as performance, weights, dimensions, pressures, temperatures, mass flows and turbopump operating characteristics for both design and off‐design operating conditions. Representative NTP engine system designs are also shown. An overview of NESS methodology and capabilities is presented in this paper, with special emphasis being placed on recent code developments.The second phase of development of a Nuclear Thermal Propulsion (NTP) engine system design analysis code has been completed. The standalone, versatile Nuclear Engine System Simulation (NESS) code provides an accurate, detailed assessment of engine system operating performance, weight, and sizes. The critical information is required to support ongoing and future engine system and stage design study efforts. This recent development effort included incorporation of an updated solid‐core nuclear thermal reactor model that yields a reduced core weight and higher fuel power density when compared to a NERVA type reactor. NESS can now analyze expander, gas generator, and bleed cycles, along with multi‐redundant propellant pump feed systems. Performance and weight of efficient multi‐stage axial turbopump can now be determined, in addition to the traditional centrifugal pump.Key code outputs include reactor operating charactertistics and weights and well as engine system parameters such as performance, weights, dim...

Earlier this year Aerojet Propulsion Division (APD) introduced a new, advanced nuclear thermal rocket engine (NTRE) concept intended for manned missions to the moon and to Mars. This NTRE promises to be both shorter and lighter in weight than conventionally designed engines, because its forward flowing reactor is located within an expansion‐deflection (E‐D) rocket nozzle. The concept has matured during the year, and this paper discusses a nearer term version that resolves four open issues identified in the initial concept: (1)Reactor design and cooling scheme simplification while retaining a high pressure power balance option; (2)Eliminate need for a new, uncooled nozzle throat material suitable for long life application; (3)Practical provision for reactor power control; and (4)Use near term, long life turbopumps.

This paper presents an overview of soviet planning for manned and unmanned missions to Mars. The feasibility of designing a propulsion system based on a nuclear power reactor with a turbomachine converter of 50 MW electric power is discussed. The problems related to radiation shielding are presented.(AIP)