scholarly journals A Numerical Investigation of the Startup Transient in a Wave Rotor

1997 ◽  
Vol 119 (3) ◽  
pp. 676-682 ◽  
Author(s):  
D. E. Paxson
Keyword(s):  
Numerical Investigation ◽  
Gas Turbine ◽  
Wave Rotor ◽  
Turbine Engine ◽  
One Dimensional ◽  
Rotor Center ◽  
Flow Through ◽  
Startup Process ◽  
Topping Cycle ◽  
Volume Models

The startup process is investigated for a hypothetical four-port wave rotor, envisioned as a topping cycle for a small gas turbine engine. The investigation is conducted numerically using a multi-passage, one-dimensional CFD based wave rotor simulation in combination with lumped volume models for the combustor, exhaust valve plenum, and rotor center cavity components. The simulation is described and several startup transients are presented which illustrate potential difficulties for the specific cycle design investigated. In particular it is observed that, prior to combustor light-off, or just after, the flow through the combustor loop is reversed from the design direction. The phenomenon is demonstrated and several possible modification techniques are discussed that avoid or overcome the problem.

scholarly journals A Numerical Investigation of the Startup Transient in a Wave Rotor

1996 ◽  
Author(s):  
Daniel E. Paxson
Keyword(s):  
Numerical Investigation ◽  
Gas Turbine ◽  
Wave Rotor ◽  
Turbine Engine ◽  
One Dimensional ◽  
Rotor Center ◽  
Flow Through ◽  
Startup Process ◽  
Topping Cycle ◽  
Volume Models

The startup process is investigated for a hypothetical four-port wave rotor, envisioned as a topping cycle for a small gas turbine engine. The investigation is conducted numerically using a multi-passage, one-dimensional CFD based wave rotor simulation in combination with lumped volume models for the combustor, exhaust valve plenum, and rotor center cavity components. The simulation is described and several startup transients are presented which illustrate potential difficulties for the specific cycle design investigated. In particular it is observed that, prior to combustor light-off, or just after, the flow through the combustor loop is reversed from the design direction. The phenomenon is demonstrated and several possible modifications techniques are discussed which avoid or overcome the problem.

scholarly journals Performance Benefits for Wave Rotor-Topped Gas Turbine Engines

1996 ◽  
Author(s):  
Scott M. Jones ◽  
Gerard E. Welch
Keyword(s):  
Steady State ◽  
Gas Turbine ◽  
Engine Performance ◽  
Thermodynamic Cycle ◽  
Cycle Performance ◽  
Specific Power ◽  
Inlet Temperature ◽  
Wave Rotor ◽  
Turbine Engine ◽  
One Dimensional

The benefits of wave rotor-topping in turboshaft engines, subsonic high-bypass turbofan engines, auxiliary power units, and ground power units are evaluated. The thermodynamic cycle performance is modeled using a one-dimensional steady-state code; wave rotor performance is modeled using one-dimensional design/analysis codes. Design and off-design engine performance is calculated for baseline engines and wave rotor-topped engines, where the wave rotor acts as a high pressure spool. The wave rotor-enhanced engines are shown to have benefits in specific power and specific fuel flow over the baseline engines without increasing turbine inlet temperature. The off-design steady-state behavior of a wave rotor-topped engine is shown to be similar to a conventional engine. Mission studies are performed to quantify aircraft performance benefits for various wave rotor cycle and weight parameters. Gas turbine engine cycles most likely to benefit from wave rotor-topping are identified. Issues of practical integration and the corresponding technical challenges with various engine types are discussed.

Effect of Divergence Angle on Flow Through Inlet Section of Diffuser of a Gas Turbine Combustion Chamber: The CFD Approach

2006 ◽  
Author(s):  
Digvijay B. Kulshreshtha ◽  
S. A. Channiwala ◽  
Jitendra Chaudhary ◽  
Zoeb Lakdawala ◽  
Hitesh Solanki ◽  
...  
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Total Pressure ◽  
Divergence Angle ◽  
Velocity Head ◽  
Turbine Engine ◽  
Inlet Velocity ◽  
Pressure Losses ◽  
Flow Through ◽  
Mach Numbers

In the combustor inlet diffuser section of gas turbine engine, high-velocity air from compressor flows into the diffuser, where a considerable portion of the inlet velocity head PT3 − PS3 is converted to static pressure (PS) before the airflow enters the combustor. Modern high through-flow turbine engine compressors are highly loaded and usually have high inlet Mach numbers. With high compressor exit Mach numbers, the velocity head at the compressor exit station may be as high as 10% of the total pressure. The function of the diffuser is to recover a large proportion of this energy. Otherwise, the resulting higher total pressure loss would result in a significantly higher level of engine specific fuel consumption. The diffuser performance must also be sensitive to inlet velocity profiles and geometrical variations of the combustor relative to the location of the pre-diffuser exit flow path. Low diffuser pressure losses with high Mach numbers are more rapidly achieved with increasing length. However, diffuser length must be short to minimize engine length and weight. A good diffuser design should have a well considered balance between the confliction requirements for low pressure losses and short engine lengths. The present paper describes the effect of divergence angle on diffuser performance for gas turbine combustion chamber using Computational Fluid Dynamic Approach. The flow through the diffuser is numerically solved for divergence angles ranging from 5 to 25°. The flow separation and formation of wake regions are studied.

A One Dimensional, Time Dependent Inlet / Engine Numerical Simulation for Aircraft Propulsion Systems

1997 ◽  
Author(s):  
Doug Garrard ◽  
Milt Davis ◽  
Steve Wehofer ◽  
Gary Cole
Keyword(s):  
Numerical Simulation ◽  
Gas Turbine ◽  
High Frequency ◽  
Gas Turbine Engine ◽  
Simulation System ◽  
Time Dependent ◽  
Propulsion Systems ◽  
Turbine Engine ◽  
One Dimensional ◽  
Supersonic Inlet

The NASA Lewis Research Center (LeRC) and the Arnold Engineering Development Center (AEDC) have developed a closely coupled computer simulation system that provides a one dimensional, high frequency inlet / engine numerical simulation for aircraft propulsion systems. The simulation system, operating under the LeRC-developed Application Portable Parallel Library (APPL), closely coupled a supersonic inlet with a gas turbine engine. The supersonic inlet was modeled using the Large Perturbation Inlet (LAPIN) computer code, and the gas turbine engine was modeled using the Aerodynamic Turbine Engine Code (ATEC). Both LAPIN and ATEC provide a one dimensional, compressible, time dependent flow solution by solving the one dimensional Euler equations for the conservation of mass, momentum, and energy. Source terms are used to model features such as bleed flows, turbomachinery component characteristics, and inlet subsonic spillage while unstarted. High frequency events, such as compressor surge and inlet unstart, can be simulated with a high degree of fidelity. The simulation system was exercised using a supersonic inlet with sixty percent of the supersonic area contraction occurring internally, and a GE J85-13 turbojet engine.

scholarly journals A Parametric Starting Study of an Axial-Centrifugal Gas Turbine Engine Using a One-Dimensional Dynamic Engine Model and Comparisons to Experimental Results: Part 1 — Model Development and Facility Description

1998 ◽  
Author(s):  
A. Karl Owen ◽  
Anne Daugherty ◽  
Doug Garrard ◽  
Howard C. Reynolds ◽  
Richard D. Wright
Keyword(s):  
Gas Turbine ◽  
Initial Conditions ◽  
Model Development ◽  
Ground Level ◽  
Gas Turbine Engine ◽  
Calibration Data ◽  
Gas Generator ◽  
Turbine Engine ◽  
One Dimensional ◽  
Engine Model

A generic one-dimensional gas turbine engine model, developed at the Arnold Engineering Development Center, has been configured to represent the gas generator of a General Electric axial-centrifugal gas turbine engine in the six kg/sec airflow class. The model was calibrated against experimental test results for a variety of initial conditions to insure that the model accurately represented the engine over the range of test conditions of interest. These conditions included both assisted (with a starter motor) and unassisted (altitude windmill) starts. The model was then exercised to study a variety of engine configuration modifications designed to improve its starting characteristics and thus quantify potential starting improvements for the next generation of gas turbine engines. This paper discusses the model development and describes the test facilities used to obtain the calibration data. The test matrix for the ground level testing is also presented. A companion paper presents the model calibration results and the results of the trade-off study.

Air-Standard Aerothermodynamic Analysis of Gas Turbine Engines With Wave Rotor Combustion

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
M. R. Nalim ◽  
H. Li ◽  
P. Akbari
Keyword(s):  
Gas Turbine ◽  
Gas Dynamics ◽  
Engine Performance ◽  
Algebraic Model ◽  
Operating Conditions ◽  
State Variables ◽  
Wave Rotor ◽  
Turbine Engine ◽  
Fill Fraction ◽  
Wave Compression

The wave rotor combustor can significantly improve gas turbine engine performance by implementing constant-volume combustion. The periodically open and closed combustor complicates thermodynamic analysis. Key cycle parameters depend on complex gas dynamics. In this study, a consistent air-standard aerothermodynamic model with variable specific heat is established. An algebraic model of the dominant gas dynamics estimates fill fraction and internal wave compression for typical port designs, using a relevant flow Mach number to represent wave amplitudes. Nonlinear equations for thermodynamic state variables are solved numerically by Newton–Raphson iteration. Performance measures and key operating conditions are predicted, and a quasi-one-dimensional computational model is used to evaluate the usefulness of the algebraic model.

Performance Enhancement of Gas Turbine Engines Topped With Wave Rotors and Pulse Detonation Combustors

2020 ◽  
Author(s):  
Pereddy Nageswara Reddy
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Compressed Air ◽  
Turbine Engines ◽  
Specific Work ◽  
Wave Rotor ◽  
Detonation Products ◽  
Turbine Engine ◽  
Pulse Detonation ◽  
C 30

Abstract In the present research work, a novel method of integrating the conventional gas turbine engine with a Wave Rotor (WR) and a Pulse Detonation Combustor (PDC) is proposed to increase the specific work and thermal efficiency of the engine. Two gas turbine engine configurations, viz. (i) Baseline engine topped with a wave rotor and a steady flow combustor (BWRSFC), and (ii) Baseline engine topped with a wave rotor and a pulse detonation combustor (BWRPDC), have been analyzed with and without recuperative systems. In the case of BWRPDC, the principle of quasi-steady expansion of detonation products through a nozzle into the ejector to entrain and eject the bypassed compressed air along with detonation products exhausted from WR, and a steady expansion of remained detonation products of PDC through the WR to provide the required energy transfer to further compress and supply the un-bypassed compressed air to PDC, has been considered. The pressure of the ejected gases from the ejector will be 25% to 35% higher than the air pressure delivered by the compressor of baseline engine and can develop more specific work with enhanced thermal efficiency when expanded in the turbine. A computer code is developed in MATLAB to simulate the engine performance with and without recuperation / regeneration. For thermodynamic calculations, two un-recuperated micro-turbine engines called C-30 and C-60 made by Capstone Turbine Corporation are considered. C2H4/air is taken as the fuel-oxidizer. The variation in specific work, and thermal efficiency with wave rotor pressure ratio has been investigated for C-30 and C-60 engines. Further, a sensitivity analysis of the performance of BWRPDC with a change in the Entrainment Coefficient (EC) of ejector has also been made.

scholarly journals Assessment of Combustion Modes for Internal Combustion Wave Rotors

1999 ◽  
Vol 121 (2) ◽  
pp. 265-271 ◽  
Author(s):  
M. R. Nalim
Keyword(s):  
Gas Turbine ◽  
Combustion Wave ◽  
Mode Selection ◽  
Internal Combustion ◽  
Combustion Mode ◽  
Wave Rotor ◽  
Turbine Engine ◽  
Reasonable Time ◽  
Wave Rotors ◽  
Combustion Modes

Combustion within the channels of a wave rotor is examined as a means of obtaining pressure gain during heat addition in a gas turbine engine. Three modes of combustion are assessed: premixed autoignition (detonation), premixed deflagration, and non-premixed autoignition. The last two will require strong turbulence for completion of combustion in a reasonable time in the wave rotor. The autoignition modes will require inlet temperatures in excess of 800 K for reliable ignition with most hydrocarbon fuels. Examples of combustion mode selection are presented for two engine applications.

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