scholarly journals Leakage Assessment of Pressure-Exchange Wave Rotors

2008 ◽  
Vol 24 (4) ◽  
pp. 732-740 ◽  
Author(s):  
P. Akbari ◽  
M. R. Nalim ◽  
E. S. Donovan ◽  
P. H. Snyder
Keyword(s):  
Wave Rotors ◽  
Pressure Exchange ◽  
Leakage Assessment

Numerical Modeling of a Wave Turbine and Estimation of Shaft Work

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Ravichandra R. Jagannath ◽  
Sally P. M. Bane ◽  
M. Razi Nalim
Keyword(s):  
Angular Momentum ◽  
Dynamic Pressure ◽  
Work Output ◽  
Reference Case ◽  
Efficient Energy Transfer ◽  
Curvature Effects ◽  
Axial Channel ◽  
Curved Channels ◽  
Wave Rotors ◽  
Pressure Exchange

Wave rotors are periodic-flow devices that provide dynamic pressure exchange and efficient energy transfer through internal pressure waves generated due to fast opening and closing of ports. Wave turbines are wave rotors with curved channels that can produce shaft work through change of angular momentum from inlet to exit. In the present work, conservation equations with averaging in the transverse directions are derived for wave turbines, and quasi-one-dimensional model for axial-channel non-steady flow is extended to account for blade curvature effects. The importance of inlet incidence is explained and the duct angle is optimized to minimize incidence loss for a particular boundary condition. Two different techniques are presented for estimating the work transfer between the gas and rotor due to flow turning, based on conservation of angular momentum and of energy. The use of two different methods to estimate the shaft work provides confidence in reporting of work output and confirms internal consistency of the model while it awaits experimental data for validation. The extended wave turbine model is used to simulate the flow in a three-port wave rotor. The work output is calculated for blades with varying curvature, including the straight axial channel as a reference case. The dimensional shaft work is reported for the idealized situation where all loss-generating mechanisms except flow incidence are absent, thus excluding leakage, heat transfer, friction, port opening time, and windage losses. The model developed in the current work can be used to determine the optimal wave turbine designs for experimental investment.

Crypto-steady supersonic pressure exchange: A simple analytical model

2008 ◽  
Vol 85 (4) ◽  
pp. 228-242 ◽  
Author(s):  
Hongfang Zhang ◽  
Charles A. Garris
Keyword(s):  
Analytical Model ◽  
Simple Analytical Model ◽  
Pressure Exchange

Performance Benefits of R718 Turbo-Compression Cycle Using 3-Port Condensing Wave Rotors

2004 ◽  
Author(s):  
Amir A. Kharazi ◽  
Pezhman Akbari ◽  
Norbert Mu¨ller
Keyword(s):  
Performance Enhancement ◽  
The Novel ◽  
Wave Rotor ◽  
Flash Evaporation ◽  
Pressurized Water ◽  
Wave Rotors ◽  
Compression Cycle ◽  
Performance Map ◽  
Wave Compression ◽  
Novel Concept

A number of technical challenges have often hindered the economical application of refrigeration cycles using water (R718) as refrigerant. The novel concept of condensing wave rotor provides a solution for performance improvement of R718 refrigeration cycles. The wave rotor implementation can increase efficiency and reduce the size and cost of R718 units. The condensing wave rotor employs pressurized water to pressurize, desuperheat, and condense the refrigerant vapor — all in one dynamic process. In this study, the underlying phenomena of flash evaporation, shock wave compression, desuperheating, and condensation inside the wave rotor channels are described in a wave and phase-change diagram. A computer program based on a thermodynamic model is generated to evaluate the performance of R718 baseline and wave-rotor-enhanced cycles. The detailed thermodynamic approach for the baseline and the modified cycles is described. The effect of some key parameters on the performance enhancement is demonstrated as an aid for optimization. A generated performance map summarizes the findings.

Basic design scheme for wave rotors

Shock Waves ◽  
2008 ◽  
Vol 18 (5) ◽  
pp. 365-378 ◽  
Author(s):  
Florin Iancu ◽  
Janusz Piechna ◽  
Norbert Müller
Keyword(s):  
Basic Design ◽  
Design Scheme ◽  
Wave Rotors

Defining the Thermodynamic Efficiency in a Wave Rotor

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Shining Chan ◽  
Huoxing Liu ◽  
Fei Xing
Keyword(s):  
Gas Turbine ◽  
Control Volume ◽  
Thermodynamic Efficiency ◽  
Wave Rotor ◽  
Wave Rotors ◽  
Compression And Expansion ◽  
Efficiency Estimation ◽  
Parametric Analyses ◽  
Control Volumes ◽  
Thermodynamic Processes

A wave rotor enhances the performance of a gas turbine with its internal compression and expansion, yet the thermodynamic efficiency estimation has been troubling because the efficiency definition is unclear. This paper put forward three new thermodynamic efficiency definitions to overcome the trouble: the adiabatic efficiency, the weighted-pressure mixed efficiency, and the pressure pre-equilibrated efficiency. They were all derived from multistream control volumes. As a consequence, they could correct the efficiency values and make the values for compression and expansion independent. Moreover, the latter two incorporated new models of pre-equilibration inside a control volume, and modified the hypothetical “ideal” thermodynamic processes. Parametric analyses based on practical wave rotor data demonstrated that the trends of those efficiency values reflected the energy losses in wave rotors. Essentially, different thermodynamic efficiency definitions indicated different ideal thermal cycle that an optimal wave rotor can provide for a gas turbine, and they were recommended to application based on that essence.

On Length Scales for the Radial Rotating Jet Pressure Exchange Mechanism

2008 ◽  
Author(s):  
Muhammad Umar ◽  
Charles A. Garris
Keyword(s):  
Momentum Transfer ◽  
Near Field ◽  
Exchange Process ◽  
Energy Levels ◽  
Mixing Layer ◽  
Complex Flow ◽  
Transfer Energy ◽  
Length Scales ◽  
Pressure Exchange ◽  
Energy And Momentum

The crypto-steady rotating jet pressure exchange ejector is a novel concept in turbomachinery where two fluids, at different energy levels, come in direct contact with each other to transfer energy and momentum between them through non-steady interface pressure forces. The current paper seeks to provide an insight into the complex flow phenomena occurring inside the radial flow pressure exchange ejector. The primary mechanisms controlling the process are pressure exchange and mixing. This paper will seek to discriminate between energy transfer by each respective mechanism. The energy and momentum transfer in the near field is shown to be mainly due to the pressure exchange process, as the mixing layer does not develop substantially in this region. As the radius increases, the mixing layer tends to grow and the energy and momentum transfer is governed by the mixing process. As a consequence, the length scales of the pressure exchange zone are small, thus making the pressure exchange ejector more compact in size. The paper will delineate between the two length scales. If this new concept is shown to be viable for gas compression at sufficiently high pressure ratios, then, in refrigeration applications, it would enable environmentally benign refrigerants to replace the harmful chlorofluorocarbons (CFC) and reduce the effluence of greenhouse gases. Applications in many other areas, where conventional ejectors are currently used, are also possible.

Computational Analysis of Flow Inside a Diffuser of Three-Dimensional Supersonic Non-Steady Ejectors

2005 ◽  
Author(s):  
Khaled Alhussan ◽  
Charles Garris
Keyword(s):  
Computational Analysis ◽  
Static Pressure ◽  
Three Dimensional ◽  
Critical Element ◽  
Induction Mechanism ◽  
Structure Of Flow ◽  
Primary Fluid ◽  
Contour Plots ◽  
Complex Fluid ◽  
Pressure Exchange

The work to be presented herein is a Computational Fluid Dynamics investigation of the complex fluid mechanisms that occur inside a non-steady, three-dimensional, supersonic pressure exchange ejector, specifically with regard to the pressure exchange mechanisms and the induction processes between a “driving” primary fluid and a “driven” secondary fluid and how this is affected by the diffuser surface. The results will show that this ejector is capable of producing the desire affect of the flow induction in a three-dimensional supersonic, non-steady, viscous flow. Results of contour plots of total pressure and static pressure demonstrate that the flow inside the diffuser is a critical element in flow induction mechanism, especially when a pressure recovery is needed. Results of velocity vectors will show the structure of flow induction mechanism in a complex three-dimensional conical surface.

The Port Width and Position Determination for Pressure-Exchange Ejector

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Wenjing Zhao ◽  
Dapeng Hu ◽  
Peiqi Liu ◽  
Yuqiang Dai ◽  
Jiupeng Zou ◽  
...  
Keyword(s):  
High Pressure ◽  
Performance Optimization ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Operating Conditions ◽  
Maximum Deviation ◽  
Dimensionless Time ◽  
Pressure Flow ◽  
Outlet Pressure ◽  
Pressure Exchange

A pressure-exchange ejector transferring energy by compression and expansion waves has the potential for higher efficiency. The width and position of each port are essential in pressure-exchange ejector design. A dimensionless time τ expressing both port widths and the positions of port ends was introduced. A prototype was designed and the experimental system was set up. Many sets of experiment with different geometrical arrangements were conducted. The results suggest that the efficiency greatly changes with the geometrical arrangements. The efficiency is about 60% at proper port widths and positions, while at improper geometrical arrangements, the efficiency is much lower and the maximum deviation may reach about 20%. The proper dimensionless port widths and positions at different operating conditions are obtained. For a fixed overall pressure ratio, the widths of the high pressure flow inlet and middle pressure flow outlet increase as the outlet pressure increases and the low pressure flow inlet width is reduced with a larger outlet pressure. The middle pressure flow outlet (MO) opening end remains constant at different outlet pressures. The positions of the high pressure flow inlet (HI) closed end and the low pressure flow inlet (LI) open end increase with the elevation of outlet pressure, however, the distance between the HI closing end and the LI opening end is constant. The port widths and positions have a significant influence on the performance of the pressure-exchange ejector. The dimensionless data obtained are very valuable for pressure-exchange ejector design and performance optimization.

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