Performance Evaluation of an Unsteady Turbine Driven by a Pulsed Detonation Combustor

2011 ◽  
Author(s):  
Kurt P. Rouser ◽  
Paul I. King ◽  
Frederick R. Schauer ◽  
Rolf Sondergaard ◽  
John L. Hoke
Keyword(s):  
Reverse Flow ◽  
Brayton Cycle ◽  
Rotor Speed ◽  
Performance Improvements ◽  
Pulsed Detonation ◽  
Time Histories ◽  
Exit Temperature ◽  
Shaft Torque ◽  
Low Entropy ◽  
Gas Pressures

Replacing a Brayton cycle near constant-pressure combustor with a pulsed detonation combustor (PDC) may take advantage of potential performance improvements from low-entropy, pressure-gain heat addition. In this paper, the radial turbine of a Garrett automotive turbocharger is coupled to a hydrogen fueled PDC. Unsteady turbine power is obtained with a conventional dynamometer technique. Sampling frequencies greater than 10 kHz resolve rapid flowfield transients of confined detonations which occur in less than a millisecond and include peak gas pressures exceeding 4 MPa and peak gas temperatures greater than 2,400 K. Results include 6 ms time histories of turbine inlet and exit temperature, pressure, mass flow, and enthalpy during blowdown of a PDC. The unsteady inlet flowfield included momentary reverse flow, which was not observed at the turbine exit. Full pulsed detonation cycle time histories of turbine power, rotor speed, rotational energy and net shaft torque are included to describe the turbine response to detonations. Rotor speed is periodic and net shaft torque oscillates in response to a detonation. Results are shown for fill fractions ranging from 0.5 to 1.0 with a 0.5 purge fraction. PDC operating frequencies in this study range from 10 Hz to 25 Hz.

Performance of a Turbine Driven by a Pulsed Detonation Combustor

2011 ◽  
Author(s):  
Kurt P. Rouser ◽  
Paul I. King ◽  
Frederick R. Schauer ◽  
Rolf Sondergaard ◽  
John L. Hoke
Keyword(s):  
Reverse Flow ◽  
Specific Work ◽  
Time Resolved ◽  
Performance Variables ◽  
Pulsed Detonation ◽  
Fill Fraction ◽  
Pressure Gain Combustion ◽  
Time Histories ◽  
Exit Temperature ◽  
Integrated Performance

There is longstanding government and industry interest in pressure-gain combustion for use in Brayton cycle-based engines. Theoretically, pressure-gain combustion allows heat addition with reduced entropy loss. The pulsed detonation combustor (PDC) is a device that can provide such pressure-gain combustion and possibly replace the typical steady deflagration combustor. The PDC is inherently unsteady, however, and comparisons with steady deflagration combustors must be based upon time-integrated performance variables. In this study, the radial turbine of a Garrett automotive turbocharger was coupled directly to and driven, full admission, by a hydrogen-fueled PDC fueled. Data included pulsed-cycle time histories of turbine inlet and exit temperature, pressure, velocity, mass flow, and enthalpy. The unsteady inlet flowfield showed momentary reverse flow, and thus unsteady accumulation and expulsion of mass and enthalpy within the device. The coupled turbine-driven compressor provided a time-resolved measure of turbine power. Duty cycle increased with PDC frequency. Power and cycle-average specific work increased with PDC frequency and fill fraction.

Experimental and Analytical Surge Cycle Analysis of a High Pressure Aero Engine Compressor

2012 ◽  
Author(s):  
Phillip Waniczek ◽  
Harald Schoenenborn ◽  
Peter Jeschke
Keyword(s):  
Flow Field ◽  
Reverse Flow ◽  
Flow Direction ◽  
Specific Work ◽  
Rotor Speed ◽  
Suction Surface ◽  
Trailing Edge ◽  
Wide Range ◽  
Aero Engine ◽  
Engine Compressor

The unsteady flow field during surge of the front rotor of an eight-stage axial aero engine compressor has been investigated experimentally and analytically. For that purpose, two newly designed multi-sensor probes are installed up- and downstream of the first rotor. Surge experiments are conducted at four different speed lines (75–93% speed) covering a wide range of the compressor map and measurements have been taken at two different channel heights (50% and 70% span). The results show that the flow field varies extremely during surge up- and downstream of the rotor. In contrast to the flow at the rotor leading edge, which is nearly independent of the rotor speed, the flow at the rotor trailing edge is highly dependent of the rotor speed. Therefore, the performance of the rotor during surge is dependent on the reverse through-flow of the stators. At low speeds the flow passes the stators without any changes in the flow direction. If speed is increased the reverse flow is guided more and more by the stators. These different flow conditions have a direct impact on the process of energy conversion of the rotor during the surge event. The incoming reverse flow at the rotor trailing edge impinges on the blade from the suction surface side at lower speeds and turns to the pressure surface side when speed is increased. Hence, the deviation and specific work grow. In addition to the surge experiments simulations of the surge events are conducted with a 1D code called SYSQ3D. The simulations and experiments match well and underline the capability of the new multi-sensor probes to accurately measure the flow patterns during surge.

Systems-Level Performance Estimation of a Pulse Detonation Based Hybrid Engine

2006 ◽  
Author(s):  
Jeffrey Goldmeer ◽  
Venkat Tangirala ◽  
Anthony Dean
Keyword(s):  
Limit Cycle ◽  
Total Pressure ◽  
Pressure Rise ◽  
Performance Estimation ◽  
Published Data ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Total Enthalpy ◽  
Pulse Detonation ◽  
Exit Temperature

A key application for a Pulse Detonation Engine concept is envisioned as a hybrid engine, which replaces the combustor in a conventional gas turbine with a Pulse Detonation Combustor (PDC). A limit cycle model, based on quasi 1-D, unsteady Computational Fluid Dynamics (CFD) simulations, was developed to estimate the performance of a pressure-rise PDC in a hybrid engine to power a subsonic engine core. The parametric space considered for simulations of the PDC operation includes the mechanical compression or the flight conditions that determine the inlet pressure and the inlet temperature conditions, fill fraction and purge fraction. The PDC cycle process time scales including overall operating frequency were determined via limit-cycle simulations. The methodology for estimation of performance of the PDC considers the unsteady effects of PDC operation. These metrics include a ratio of time-averaged exit total pressure to inlet total pressure and a ratio of mass-averaged exit total enthalpy to inlet total enthalpy. This information can be presented as a performance map for the PDC, which was then integrated into a systems-level cycle analysis model, using Gate-Cycle, to estimate the propulsive performance of the hybrid engine. Three different analyses were performed. The first was a validation of the model against published data for specific impulse. The second examined the performance of a PDC versus a traditional Brayton cycle for a fixed combustor exit temperature; the results show an increased efficiency of the PDC relative to the Brayton cycle. The third analysis performed was a detailed parametric study varying engine conditions to examine the performance of the hybrid engine. The analysis has shown that increasing the purge fraction, which can reduce the overall PDC exit temperature, can simultaneously provide small increases in overall system efficiency.

Influence of the Arrangement of Dilution Holes for Dilution Mixing in a Three-Injector Reverse Flow Combustor

2014 ◽  
Author(s):  
Wei Dai ◽  
Yan Zhang ◽  
Yuzhen Lin ◽  
Qian Yang ◽  
Chi Zhang
Keyword(s):  
Temperature Profile ◽  
Swirling Flow ◽  
Reverse Flow ◽  
Ambient Pressure ◽  
Outer Ring ◽  
Inlet Temperature ◽  
Test Model ◽  
Mixing Rate ◽  
Mixing Performance ◽  
Exit Temperature

The exit temperature profile has a great effect on the reliability and security in a gas turbine. In this paper, the exit temperature profile of a small engine reverse-flow combustor with three injectors test module was experimentally obtained to qualitatively analyze the influence of the dilution hole distribution. The test model was a three-injector rectangular reverse-flow combustor with swirling flow atomizing. A 1D moving thermocouple rake was used to measure the global exit temperature profile of the combustor. The pressure was at ambient pressure with the inlet temperature was 290K. The FAR was in the range of 0.03. The dilution holes were in opposed and staggered arrangements. The experimental results showed that the exit temperature profile was obviously influenced by the dilution holes. Compared with the opposed dilution jets, the staggered dilution jets provided more uniform circumferential exit temperature profile, but a little higher pattern factor of 0.1725. The numerical results showed that the staggered dilution jets generated a larger scale counter-rotating vortex pairs. The inner and outer jets not only did not interact with each other (especially at the outer ring of combustor), but also filled the intermediate regions of dilution jets, resulting in a higher gas mixing rate. Consequently, the staggered dilution jets provided a better mixing performance for the outer ring of combustor.

System-Level Performance Estimation of a Pulse Detonation Based Hybrid Engine

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Jeffrey Goldmeer ◽  
Venkat Tangirala ◽  
Anthony Dean
Keyword(s):  
Limit Cycle ◽  
Total Pressure ◽  
Performance Estimation ◽  
System Level ◽  
Published Data ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Total Enthalpy ◽  
Pulse Detonation ◽  
Exit Temperature

A key application for a Pulse detonation engine concept is envisioned as a hybrid engine, which replaces the combustor in a conventional gas turbine with a pulse detonation combustor (PDC). A limit-cycle model, based on quasi-unsteady computational fluid dynamics simulations, was developed to estimate the performance of a pressure-rise PDC in a hybrid engine to power a subsonic engine core. The parametric space considered for simulations of the PDC operation includes the mechanical compression or the flight conditions that determine the inlet pressure and the inlet temperature conditions, fill fraction, and purge fraction. The PDC cycle process time scales, including the overall operating frequency, were determined via limit-cycle simulations. The methodology for the estimation of the performance of the PDC considers the unsteady effects of PDC operation. These metrics include a ratio of time-averaged exit total pressure to inlet total pressure and a ratio of mass-averaged exit total enthalpy to inlet total enthalpy. This information can be presented as a performance map for the PDC, which was then integrated into a system-level cycle analysis model, using GATECYCLE, to estimate the propulsive performance of the hybrid engine. Three different analyses were performed. The first was a validation of the model against published data for a specific impulse. The second examined the performance of a PDC versus a traditional Brayton cycle for a fixed combustor exit temperature; the results show an increased efficiency of the PDC relative to the Brayton cycle. The third analysis performed was a detailed parametric study of varying engine conditions to examine the performance of the hybrid engine. The analysis has shown that increasing the purge fraction, which can reduce the overall PDC exit temperature, can simultaneously provide small increases in the overall system efficiency.

Effect of geometric modification on flow behaviour and performance of reverse flow combustor

2018 ◽  
Vol 233 (4) ◽  
pp. 1457-1471 ◽  
Author(s):  
J Joy ◽  
PC Wang ◽  
SCM Yu
Keyword(s):  
Fuel Consumption ◽  
Turbulence Model ◽  
Pressure Loss ◽  
Reverse Flow ◽  
Numerical Results ◽  
Performance Characteristics ◽  
Experimental Results ◽  
Exit Temperature ◽  
Cooling Effects ◽  
Model C

Numerical investigation had been performed on the reverse flow combustor of a mini gas turbine engine so as to investigate the performance characteristics of the combustor by means of geometry modifications. In order to enhance the thrust performance of the reverse flow combustor, the baseline combustor (Model A) was previously modified by increasing its chamber volume by 15%, the fuel-air ratio (FAR) by 40% and by raising the injection point density to two (Model B). However, the thrust optimization of the baseline combustor resulted in high combustor exit temperature that could potentially damage the combustor liners. To rectify the adversity of high exit temperature, the combustor cooling effects were achieved by subsequently adding additional passage holes at the dilution zone of the Model B combustor so as to direct the incoming cold flow from the compressor exit towards the outgoing hot flow in the reverse flow combustor (Model C). The commercial software ANSYS Fluent 17.0 was adopted in this study and to solve the turbulence model, Reynolds Averaged Navier–Stokes methodology was adopted by employing standard k-ɛ turbulence model with standard wall function. A probability density function model was generated to introduce the combustion species and a discrete phase Model was employed to specify the kerosene fuel-based injector properties. The numerical results of Model A combustor were validated against the previous experimental results using grid convergence test. The numerical results were observed to be in good agreement with the experimental results. However, ineffective mixing was found to be a setback for the baseline combustor (Model A) indicating the need for combustor performance improvement. The comparative results of the revised combustor model (Model C) showed that better cooling effects at the combustor exit could be achieved by adding supplementary passage holes at the downstream of the combustor outer liner, respectively. The addition of dilution holes also resolved the issue of high pressure loss that was observed in Model A combustor with no significant change in the specific fuel consumption. The present paper confirms that the performance of the reverse flow combustor model could be affected by slight geometric modification. The performance characteristics of the combustor models are presented in terms of thrust, thrust-to-weight ratio, specific fuel consumption, pressure loss and pattern factor.

A Development Method and Applications of the Most Severe Engine Parameters for Airworthiness Certification

2015 ◽  
Author(s):  
Huihui Li ◽  
Bin Tang
Keyword(s):  
Operating Conditions ◽  
Aircraft Engines ◽  
Rotor Speed ◽  
Commercial Aircraft ◽  
Certification Process ◽  
Development Method ◽  
Adverse Conditions ◽  
Shaft Torque ◽  
The Difference

For commercial aircraft engines, airworthiness certification is essential and the very first step before entry into service. Airworthiness requirements mainly consider the safety of the aircraft and mandate the aviation products to safely operate under all possible conditions. Therefore, during an airworthiness certification process, the relevant analyses and verifications are generally carried out by considering the most adverse operating conditions. A method for obtaining the most severe engine parameters which represent the possibly most adverse conditions is presented in this paper. Furthermore, it is used to complete the calculation of a set of most severe parameters, including rotor speed, turbine temperature, pressure, shaft torque, etc. Finally, this paper describes applications of these most severe parameters in the certification of the engine airworthiness regulation-CCAR/FAR33. Two examples are provided to illustrate the difference between using the general parameters and the most severe parameters. These examples demonstrate that application of most severe engine parameters to comply with the airworthiness requirements is the most practical way to guarantee the true safety.

Principles of Low-Vacuum SEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1304-1305
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
New Technologies ◽  
High Vacuum ◽  
Optical Microscope ◽  
Specimen Surface ◽  
Electrical Field ◽  
Gaseous Environment ◽  
New Information ◽  
Gas Molecules ◽  
New Interactions ◽  
Gas Pressures

Only recently it became possible to expand scanning electron microscopy to low vacuum and atmospheric pressure through the introduction of several new technologies. In principle, only the specimen is provided with a controlled gaseous environment while the optical microscope column is kept at high vacuum. In the specimen chamber, the gas can generate new interactions with i) the probe electrons, ii) the specimen surface, and iii) the specimen-specific signal electrons. The results of these interactions yield new information about specimen surfaces not accessible to conventional high vacuum SEM. Several microscope types are available differing from each other by the maximum available gas pressure and the types of signals which can be used for investigation of specimen properties.Electrical non-conductors can be easily imaged despite charge accumulations at and beneath their surface. At high gas pressures between 10-2 and 2 torr, gas molecules are ionized in the electrical field between the specimen surface and the surrounding microscope parts through signal electrons and, to a certain extent, probe electrons. The gas provides a stable ion flux for a surface charge equalization if sufficient gas ions are provided.

Morphological behavior of compatibilized ternary blends prepared by mechanical mixing

1993 ◽  
Vol 51 ◽  
pp. 1200-1201
Author(s):  
S.D. Smith ◽  
R.J. Spontak ◽  
D.H. Melik ◽  
S.M. Buehler ◽  
K.M. Kerr ◽  
...  
Keyword(s):  
Interfacial Adhesion ◽  
Diblock Copolymers ◽  
Ternary Blends ◽  
Mechanical Mixing ◽  
Design Considerations ◽  
Covalently Bonded ◽  
Homopolymer Blends ◽  
Emulsifying Agent ◽  
Surface Active ◽  
Low Entropy

When blended together, homopolymers A and B will normally macrophase-separate into relatively large (≫1 μm) A-rich and B-rich phases, between which exists poor interfacial adhesion, due to a low entropy of mixing. The size scale of phase separation in such a blend can be reduced, and the extent of interfacial A-B contact and entanglement enhanced, via addition of an emulsifying agent such as an AB diblock copolymer. Diblock copolymers consist of a long sequence of A monomers covalently bonded to a long sequence of B monomers. These materials are surface-active and decrease interfacial tension between immiscible phases much in the same way as do small-molecule surfactants. Previous studies have clearly demonstrated the utility of block copolymers in compatibilizing homopolymer blends and enhancing blend properties such as fracture toughness. It is now recognized that optimization of emulsified ternary blends relies upon design considerations such as sufficient block penetration into a macrophase (to avoid block slip) and prevention of a copolymer multilayer at the A-B interface (to avoid intralayer failure).

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