Development and Performance Measurement of Oil-Free Turbocharger Supported on Gas Foil Bearings

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Yong-Bok Lee ◽  
Dong-Jin Park ◽  
Tae Ho Kim ◽  
Kyuho Sim
Keyword(s):  
Power Loss ◽  
Time Delays ◽  
Operating Conditions ◽  
Total Power ◽  
Stable Operation ◽  
Compressor Wheel ◽  
Foil Bearings ◽  
Vehicle Engine ◽  
Turbine Inlet ◽  
Diesel Vehicle

This paper present the development of an oil-free turbocharger (TC) supported on gas foil bearings (GFBs) and its performance evaluation in a test rig driven by a diesel vehicle engine (EG). The rotor-bearing system was designed via a rotordynamic analysis with dynamic force coefficients derived from the analysis of the GFBs. The developed oil-free TC was designed using a hollow rotor with a radial turbine at one end and a compressor wheel at the other end, a center housing with journal and thrust GFBs, and turbine and compressor casings. Preliminary tests driven by pressurized shop air at room temperature demonstrated relatively stable operation up to a TC speed of 90,000 rpm, accompanied by a dominant synchronous motion of ∼20 μm and small subsynchronous motions of less than 2 μm at the higher end of the speed range. Under realistic operating conditions with a diesel vehicle engine at a maximum TC speed of 136,000 rpm and a maximum EG speed of 3140 rpm, EG and TC speeds and gas flow properties were measured. The measured time responses of the TC speed and the turbine inlet pressure demonstrated time delays of ∼3.9 and ∼1.3 s from that of the EG speed during consecutive stepwise EG speed changes, implying the GFB friction and rotor inertia led to time delays of ∼2.6 s. The measured pressures and temperatures showed trends following second-order polynomials against EG speed. Regarding TC efficiency, 4.3 kW of mechanical power was supplied by the turbine and 3.3 kW was consumed by the compressor at the top speed of 136,000 rpm, and the power loss reached 22% of the turbine power. Furthermore, the estimated GFB power losses from the GFB analysis were approximately 25% of the total power loss at higher speeds, indicating the remainder of the power loss resulted from heat transfer from the exhaust gas to the surrounding solid structures. Incidentally, as the TC speed was increased from 45,000 to 136,000 rpm, the estimated turbine inlet power increased from 19 to 79 kW, the compressor exit power increased from 7 to 26 kW, and the TC output mass flow rate from the compressor increased from 21 to 74 g/s. The average TC compressor exit power was estimated at ∼34% of the turbine inlet power over this range.

A Communication-Free Decentralized Power Control Approach for Power Loss Minimization in Islanded Microgrids Using Extremum Seeking

2017 ◽  
Author(s):  
Su-Yang Shieh ◽  
Tulga Ersal ◽  
Huei Peng
Keyword(s):  
Power Control ◽  
Power Loss ◽  
Operating Conditions ◽  
Extremum Seeking ◽  
Total Power ◽  
Loss Minimization ◽  
Plug And Play ◽  
Control Approach ◽  
Structure Information ◽  
Power Loss Minimization

This paper considers islanded microgrids and is motivated by the need for decentralized control strategies with minimal communication among grid components to support a robust and plug-and-play operation. We focus on the problem of power allocation among the distributed generation units (DGs) to maintain low distribution power loss in the grid and develop a communication-free distributed power control approach for power loss minimization based on the extremum-seeking (ES) method. In this approach, the DGs implement ES simultaneously and separately to minimize their current outputs by controlling the active power. The total power loss is thus reduced and no grid structure information or communication is needed in the optimization process. The existence of a Nash equilibrium in the resulting non-cooperative game is proved. Numerical simulations are conducted to demonstrate the performance of the proposed communication-free power control approach and show that it is suitable for maintaining low power loss under different operating conditions in a plug-and-play manner.

Feasibility Study of an Oil-Free Turbocharger Supported on Gas Foil Bearings via On-Road Tests of a 2-Liter Class Diesel Vehicle

2012 ◽  
Author(s):  
Kyuho Sim ◽  
Suk Bum Kwon ◽  
Tae Ho Kim ◽  
Yong-Bok Lee
Keyword(s):  
Feasibility Study ◽  
Vehicle Suspension ◽  
External Shocks ◽  
Variable Geometry Turbocharger ◽  
Foil Bearings ◽  
Synchronous Motion ◽  
Vehicle Engine ◽  
Compressor Impeller ◽  
Non Destructive ◽  
Diesel Vehicle

This paper presents the feasibility study of an oil-free turbocharger (TC) supported on gas foil bearings (GFBs) via on-road tests of a 2-liter class diesel vehicle. The oil-free TC is constructed using a hollow rotor with a radial turbine at one end and a compressor impeller at the other end, a center housing with journal and thrust GFBs, and turbine and compressor casings. The oil-free TC reuses parts of a commercial variable geometry turbocharger except for the rotor-bearing system. In a test rig driven by a diesel vehicle engine (EG), the rotordynamic performance of the oil-free TC is evaluated up to the rotor speed of 130 krpm, while being measured at the compressor end. The journal GFBs are modified to enhance the rotordynamic performance by inserting three metal shims between the bump-strip layers and bearing housing. The rotordynamic performance is also measured during on-road tests by replacing the original TC of the test diesel vehicle with the constructed oil-free TC. The journal GFBs have a relatively large bearing clearance and no metal shims to generate sub-synchronous motions at low TC and EG speeds. During normal vehicle driving, the TC rotor motions show steady rotordynamic operations. The oil-free TC rotates at 25 krpm ∼50 krpm while the vehicle runs at 20 km/h ∼30 km/h on the roads. Sub-synchronous rotor motions initiate with a frequency of ∼100 Hz at the TC speed of ∼37 krpm. The TC rotor motion also shows multiple EG-induced harmonics, as expected. Upon external shocks given by passing the vehicle on road-bumps, the sub-synchronous motions are excited only when the rotor rotates above the initiation speed of sub-synchronous motion. The excitation is non-destructive because the vehicle suspension absorbs most of the external shock. Incidentally, the external shocks appear to have no influence on the synchronous motion and engine-induced harmonics of the TC rotor.

Vibration Characteristics of a 75kW Turbo Machine With Air Foil Bearings

2006 ◽  
Vol 129 (3) ◽  
pp. 843-849 ◽  
Author(s):  
Kyeong-Su Kim ◽  
In Lee
Keyword(s):  
High Speed ◽  
Performance Test ◽  
Pressure Ratio ◽  
Vibration Characteristics ◽  
Operating Conditions ◽  
Maximum Pressure ◽  
Stable Operation ◽  
Foil Bearings ◽  
Wide Range ◽  
Free Environment

Air foil bearings are very attractive bearing systems for turbomachinery because they have several advantages over conventional bearings in terms of oil-free environment, low power loss, long life, and no maintenance. However, most of the developed machines using air foil bearings are limited to small and high-speed rotors of 60,000–120,000 rpm, since the increase in power of turbomachinery requires lower rotor speed and greater loading in bearings, which makes it difficult to use air foil bearings for large machines. In this paper, a 75 kW turboblower using air foil bearings is introduced, and the vibration characteristics of the machine have been investigated experimentally under a wide range of operating conditions, including compressor surge in the performance test. The machine is designed to be fully air lubricated and air cooled, and its operating speed is 20,000–26,000 rpm with maximum pressure ratio of 1.8. The results show that the air foil bearings offer adequate damping to ensure dynamically stable operation in the whole range.

Debris Tolerant Compliant Foil Bearings for High-Speed Turbomachines

2015 ◽  
Author(s):  
Andrew Hunsberger ◽  
James F. Walton ◽  
Hooshang Heshmat
Keyword(s):  
Military Service ◽  
Power Loss ◽  
High Speed ◽  
Operating Conditions ◽  
Component Level ◽  
Foil Bearings ◽  
Auxiliary Power Units ◽  
High Concentrations ◽  
Teflon Coating ◽  
Dust Ingestion

High-speed turbomachines such as air cycle machines (ACM), auxiliary power units (APU) and turbogenerators as used in aerospace systems operate in hot and harsh environments. Such operating conditions often dictate the application of compliant foil bearings to provide reliable, low power loss performance. Many such turbomachines in operation today were developed, validated and commissioned into service more than 30 years ago. While these machines are still valuable and highly effective, in some cases premature failures have been observed by the end user. In particular, equipment that has seen use in environments with high concentrations of airborne particulates such as sand, dust and other debris (i.e. Middle East) appear to be particularly vulnerable. Exponential gains in load carrying capacity, damping characteristics and temperature limitations have been demonstrated from compliant foil bearings over the past 30 years and retro-fitting these higher performance complaint foil bearings into legacy turbomachines can provide drastic improvements in system performance, increase mean time between service and reduce, and reduce failure rates. In this paper the authors will present results from testing of an ACM which was developed and initially commissioned into service more than 30 years ago for use in the F/A-18 but remains active in aerospace and military service today [1]. Testing of the fully refurbished ACM and its new cantilever leaf style foil gas bearing components was conducted under normal and abusive conditions such as might be encountered in operational use. The ACM foil bearings came with a Teflon coating. The performance of the cantilever leaf style compliant foil bearings was compared a tension dominated or compliant bump foil style bearing with a Korolon™ polyimide type coating. During component level testing, the compliant bump foil bearings demonstrated lower starting torque, temperature rise, and more consistent and reliable performance than the cantilevered leaf foil bearings under the same operating conditions. System testing of the ACM with both types of bearings under identical conditions was also conducted. Under baseline conditions, cantilevered-leaf bearings were observed to operate at temperatures of 72°C higher than those of the compliant bump foil bearings. The lower operating temperature of the compliant bump foil design indicated lower power loss with compliant bump foil bearings as confirmed by 10% lower turbine pressure and flow required to reach the same speed condition. In dust ingestion testing, the cantilevered-leaf bearings showed a temperature spike due ingestion of dust, leading to failure of the thrust bearings, whereas, the compliant bump foil bearings were unaffected by dust ingestion and operated reliably with minimal signs of wear or damage.

Feasibility Study of an Oil-Free Turbocharger Supported on Gas Foil Bearings Via On-Road Tests of a Two-Liter Class Diesel Vehicle

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Yong-Bok Lee ◽  
Suk Bum Kwon ◽  
Tae Ho Kim ◽  
Kyuho Sim
Keyword(s):  
Feasibility Study ◽  
External Shocks ◽  
Variable Geometry Turbocharger ◽  
The Road ◽  
Foil Bearings ◽  
Synchronous Motion ◽  
Vehicle Engine ◽  
Compressor Impeller ◽  
On The Road ◽  
Diesel Vehicle

This paper presents the feasibility study of an oil-free turbocharger (TC) supported on gas foil bearings (GFBs) via on-road tests of a 2-liter class diesel vehicle. The oil-free TC is constructed using a hollow rotor with a radial turbine at one end and a compressor impeller at the other end, a center housing with journal and thrust GFBs, and turbine and compressor casings. The oil-free TC reuses parts of a commercial variable geometry turbocharger, except for the rotor-bearing system. In a test rig driven by a diesel vehicle engine (EG), the rotordynamic performance of the oil-free TC is evaluated up to the rotor speed of 130 krpm, which is measured at the compressor end. The journal GFBs are modified to enhance the rotordynamic performance by inserting three metal shims between the bump-strip layers and bearing housing. The rotordynamic performance is also measured during on-road tests by replacing the original TC of the test diesel vehicle with the constructed oil-free TC. The journal GFBs have a relatively large bearing clearance and no metal shims to generate subsynchronous motions at low TC and EG speeds. During normal vehicle driving, the TC rotor motions show steady rotordynamic operations. The oil-free TC rotates at 25 krpm ∼ 50 krpm while the vehicle runs at 20 km/h ∼ 30 km/h on the road. Subsynchronous rotor motions initiate with a frequency of ∼100 Hz at the TC speed of ∼37 krpm. As expected, the TC rotor motion also shows multiple EG-induced harmonics. Upon external shocks, produced by driving the vehicle on road-bumps, the subsynchronous motions are only excited when the rotor rotates above the initiation speed of subsynchronous motion. The excitation is nondestructive because the vehicle suspension absorbs most of the external shock. Incidentally, the external shocks appear to have no influence on the synchronous motion and engine-induced harmonics of the TC rotor.

Evaluation of Power Loss of the Rubber V-Belt CVT

1998 ◽  
Author(s):  
T. F. Chen ◽  
C. K. Sung
Keyword(s):  
Power Loss ◽  
Wedge Angle ◽  
Operating Conditions ◽  
Total Power ◽  
Speed Ratio ◽  
Rotating Speed ◽  
Continuously Variable Transmissions ◽  
Torque Loss ◽  
Motion Characteristics ◽  
Loss Mechanisms

Abstract This paper proposes a systematic method for the evaluation of power loss of rubber V-belt continuously variable transmissions (CVT). By observing the interaction between belt and sheaves, the entire belt may be divided into four regions. They are free span, wedging-in, adhesion, and wedging-out regions. Therefore, each region possesses a distinct motion characteristic. Herein, power loss is categorized into speed and torque losses. Since speed loss contributes less than 4% of the total power loss in most operating conditions, only torque loss is considered. The mechanisms causing torque loss may be attributed to the hysteresis of belt bending, compression and shear, and friction due to radial motion of the belt. These loss mechanisms are studied on the basis of motion characteristics in each region. Parameters for loss mechanisms are then analyzed to identify their contributions to the system efficiency. These parameters include external load, rotating speed and wedge angle of the pulley, speed ratio, pre-tension, and thickness and tooth profile of the belt. In addition, an experimental study is performed for verification of the proposed analytical approach.

Analysis of Engine Efficiency of Diesel Vehicle in Transient Operating Conditions

2021 ◽  
Vol 22 (4) ◽  
pp. 941-947
Author(s):  
In Chun Chung ◽  
Young Kuk An ◽  
Jinil Park ◽  
Jonghwa Lee ◽  
Yohan Ji
Keyword(s):  
Operating Conditions ◽  
Engine Efficiency ◽  
Diesel Vehicle

Preliminarily Design of Supercritical CO2 Compression Test System

2021 ◽  
Author(s):  
Geng Teng ◽  
Laijie Chen ◽  
Xin Shen ◽  
Hua Ouyang ◽  
Yubo Zhu ◽  
...  
Keyword(s):  
Simulation Model ◽  
Compression Test ◽  
Thermodynamic Model ◽  
Supercritical Co2 ◽  
Operating Performance ◽  
Test System ◽  
Operating Conditions ◽  
Working Fluid ◽  
Stable Operation ◽  
Test Loop

Abstract The centrifugal compressor is the core component of the supercritical carbon dioxide (SCO2) power cycle. It is essential to carry out component-level experimental research on it and test the working characteristics of the compressor and its auxiliary equipment. Building an accurate closed-loop simulation model of closed SCO2 compression loop is a necessary preparation for selecting loop key parameters and establishing system control strategy, which is also an important prerequisite for the stable operation of compressor under test parameters. In this paper, the thermodynamic model of compressor, pre-cooler, orifice plate and other components in supercritical CO2 compression test system is studied, and the simulation model of compression test system is established. Moreover, based on the system enthalpy equations and physical property model of real gas, the compressor, pre-cooler and other components in the test loop are preliminarily designed by using the thermodynamic model of components. Since the operating conditions are in the vicinity of the critical point, when the operating conditions change slightly, the physical properties of the working fluid will change significantly, which might have a greater impact on the operating performance of the system. So the operating performance and the parameter changes of key nodes in the test loop under different operating conditions are calculated, which will provide theoretical guidance for the construction of subsequent experimental loops.

Influence of operating conditions on population dynamics in nitrifying biofilms

1999 ◽  
Vol 39 (7) ◽  
pp. 5-11 ◽  
Author(s):  
Valentina Lazarova ◽  
Danièle Bellahcen ◽  
Jacques Manem ◽  
David A. Stahl ◽  
Bruce E. Rittmann
Keyword(s):  
Population Dynamics ◽  
Ammonia Oxidation ◽  
Biofilm Reactor ◽  
Operating Conditions ◽  
Stable Operation ◽  
N Removal ◽  
Wide Range ◽  
Total Nitrogen Removal ◽  
Nitrite Oxidizers

TURBO N® is a circulating-bed biofilm reactor that provides stable operation and high N removal for a wide range of N and BOD loadings. This paper describes the influence of operating conditions on biofilm composition and population dynamics when the TURBO N® is operated to achieve tertiary nitrification, simultaneous carbon and ammonia oxidation and total nitrogen removal when coupled with a pre-denitrification fixed floating bed reactor. In situ specific nitrification rates and respiration tests showed that ammonium and nitrite oxidizers became less active in the biofilm once oxidation of influent BOD became important. Analyses of community structure with oligonucleotide probes targeted to the 16S rRNA showed the same general trends for nitrifiers, but also suggested shifts in the makeup of the ammonium and nitrite oxidizers that could not be detected with respirometry or specific nitrification rates.

Design of Multi-Recess Hydrostatic Journal Bearings for Minimum Total Power Loss

1974 ◽  
Vol 96 (1) ◽  
pp. 226-232 ◽  
Author(s):  
C. Cusano ◽  
T. F. Conry
Keyword(s):  
Rotational Speed ◽  
Power Loss ◽  
Load Capacity ◽  
Maximum Load ◽  
Journal Bearings ◽  
Design Criterion ◽  
Total Power ◽  
Eccentricity Ratio ◽  
Constant Ratio ◽  
Design Charts

The design problem is formulated for multi-recess hydrostatic journal bearings with a design criterion of minimum total power loss. The design is subject to the constraints of constant ratio of the recess area to the total bearing area and maximum load capacity for a given recess geometry. The L/D ratio, eccentricity ratio, ratio of recess area to total bearing area, and shaft rotational speed are considered as parameters. The analysis is based on the bearing model of Raimondi and Boyd [1]. This model is generally valid for low-to-moderate speeds and a ratio of recess area-to-total bearing area of approximately 0.5 or greater. Design charts are presented for bearings having a ratio of recess area-to-total bearing area of 0.6 and employing capillary and orifice restrictors, these being the most common types of compensating elements. A design example is given to illustrate the use of the design charts.

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