Search NASA⌕ Search

SEARCH · Search NASA

Results for “Pulse Combustors”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Computational Optimization of a Rotary Valved Pulse Combustor Concept

A resonant pulse combustor valve concept is introduced that utilizes two slotted, coaxial counterrotating discs for mechanical actuation at the combustor inlet. The intended test article for prototype demonstration is a small, 22 in. long, propane fueled laboratory combustor, flowing approximately 0.006 lbm/s of air. The objective is to develop an externally actuated (i.e., active) valve that yields better performance and longer life than the traditional internally actuated (i.e., passive), reed-type valve found on most pulse combustors. The rotary valve motion is optimized using an axisymmetric, two-dimensional computational fluid dynamic simulation with a domain that includes the valve as a moveable interior wall. Parameters such as slew rate, dwell period in the open position, and total closed period are varied using fuel specific impulse as the figure of merit. Variations in fuel injector location and air fuel ratio are also examined. Additionally, the performance impact of leakage from the rotary valve is quantified since leakage is endemic to the design. The optimized simulation results indicate that the rotary valve concept can deliver the desired performance attributes using disc rotational speeds and stresses that are well within the realm of modern materials. A preliminary mechanical valve design is included in the report.

pressure gain combustion↗
NASA NTRSDate not supplied

Computational Optimization of a Rotary Valved Pulse Combustor Concept

A resonant pulse combustor valve concept is introduced that utilizes two slotted, coaxial counterrotating discs for mechanical actuation at the combustor inlet. The intended test article for prototype demonstration is a small, 22 in. long, propane fueled laboratory combustor, flowing approximately 0.006 lbm/s of air. The objective is to develop an externally actuated (i.e., active) valve that yields better performance and longer life than the traditional internally actuated (i.e., passive), reed-type valve found on most pulse combustors. The rotary valve motion is optimized using an axisymmetric, two-dimensional computational fluid dynamic simulation with a domain that includes the valve as a moveable interior wall. Parameters such as slew rate, dwell period in the open position, and total closed period are varied using fuel specific impulse as the figure of merit. Variations in fuel injector location and air fuel ratio are also examined. Additionally, the performance impact of leakage from the rotary valve is quantified since leakage is endemic to the design. The optimized simulation results indicate that the rotary valve concept can deliver the desired performance attributes using disc rotational speeds and stresses that are well within the realm of modern materials. A preliminary mechanical valve design is included in the report.

pressure gain combustion↗
NASA NTRS2015

Parametric Study of Pulse-Combustor-Driven Ejectors at High-Pressure

Pulse-combustor configurations developed in recent studies have demonstrated performance levels at high-pressure operating conditions comparable to those observed at atmospheric conditions. However, problems related to the way fuel was being distributed within the pulse combustor were still limiting performance. In the first part of this study, new configurations are investigated computationally aimed at improving the fuel distribution and performance of the pulse-combustor. Subsequent sections investigate the performance of various pulse-combustor driven ejector configurations operating at highpressure conditions, focusing on the effects of fuel equivalence ratio and ejector throat area. The goal is to design pulse-combustor-ejector configurations that maximize pressure gain while achieving a thermal environment acceptable to a turbine, and at the same time maintain acceptable levels of NOx emissions and flow non-uniformities. The computations presented here have demonstrated pressure gains of up to 2.8%.

pulsejet↗
NASA NTRS2015

Parametric Study of Pulse-Combustor-Driven Ejectors at High-Pressure

Pulse-combustor configurations developed in recent studies have demonstrated performance levels at high-pressure operating conditions comparable to those observed at atmospheric conditions. However, problems related to the way fuel was being distributed within the pulse combustor were still limiting performance. In the first part of this study, new configurations are investigated computationally aimed at improving the fuel distribution and performance of the pulse-combustor. Subsequent sections investigate the performance of various pulse-combustor driven ejector configurations operating at high pressure conditions, focusing on the effects of fuel equivalence ratio and ejector throat area. The goal is to design pulse-combustor-ejector configurations that maximize pressure gain while achieving a thermal environment acceptable to a turbine, and at the same time maintain acceptable levels of NO(x) emissions and flow non-uniformities. The computations presented here have demonstrated pressure gains of up to 2.8.

Pressure Gain Combustion↗
NASA NTRS2018

Computational Study of Compact Ejector-Enhanced Resonant Pulse Combustors

Previous studies of Ejector-Enhanced Resonant Pulse Combustors considered configurations that were relatively long, making them difficult to incorporate in practical gas turbine engines. In the present study, more compact configurations are analyzed, focusing on the system pressure gain. The study shows that it is possible to reduce the length of both the pulse combustor and ejector components without compromising the device's performance. In fact, it is found that in several of the compact configurations analyzed, the system pressure gain actually increased, reaching pressure gain levels above 5%, significantly higher than those obtained in previous studies. The Rayleigh efficiency, which has been used in the past to characterize the performance of pulse combustors, is computed for several of the Ejector-Enhanced Resonant Pulse Combustor configurations. The Rayleigh efficiency is seen to correlate with both average combustor pressure and system pressure gain for a given configuration, however, it could not be used to compare different configurations.

Compact↗
NASA NTRS2014

Effect of Fuel Injection and Mixing Characteristics on Pulse-Combustor Performance at High-Pressure

Recent calculations of pulse-combustors operating at high-pressure conditions produced pressure gains significantly lower than those observed experimentally and computationally at atmospheric conditions. The factors limiting the pressure-gain at high-pressure conditions are identified, and the effects of fuel injection and air mixing characteristics on performance are investigated. New pulse-combustor configurations were developed, and the results show that by suitable changes to the combustor geometry, fuel injection scheme and valve dynamics the performance of the pulse-combustor operating at high-pressure conditions can be increased to levels comparable to those observed at atmospheric conditions. In addition, the new configurations can significantly reduce the levels of NOx emissions. One particular configuration resulted in extremely low levels of NO, producing an emission index much less than one, although at a lower pressure-gain. Calculations at representative cruise conditions demonstrated that pulse-combustors can achieve a high level of performance at such conditions.

Propulsion↗
NASA NTRSDate not supplied

Experimental and Computational Investigation of Valve Motion in a Resonant Pulse Combustor

The motion of a passive reed-type valve and a poppet-style valve operating in a small scale, liquid-fueled pulse combustor is investigated experimentally. Valve position and combustion chamber pressure are simultaneously measured using an in-house fabricated optical position probe. The reed valve configuration is found to operate in a self-aspirated mode, generating significant pressure gain. The poppet valve configuration cannot operate without forced air, and does not generate pressure gain. Both type valves are tested in combustors of multiple lengths. Close examination of the respective valve motions indicate that the reed valve is highly non-linear, with unique attributes that appear essential for self-aspiration. Dynamic models for the motion of each valve are implemented in a computational fluid dynamic (CFD) simulation of the pulse combustor in order to assess if this unique valve motion is critical to successful operation. The results show that it is. The implications of these results are discussed. The need for active actuation with feedback control, rather than passive valve actuation is highlighted as a critical technology for practical resonant pulse combustors.

Combustion↗
NASA NTRSDate not supplied

Experimental and Computational Investigation of Valve Motion in a Resonant Pulse Combustor

The motion of a passive reed-type valve and a poppet-style valve operating in a small scale, liquid-fueled pulse combustor is investigated experimentally. Valve position and combustion chamber pressure are simultaneously measured using an in-house fabricated optical position probe. The reed valve configuration is found to operate in a self-aspirated mode, generating significant pressure gain. The poppet valve configuration cannot operate without forced air, and does not generate pressure gain. Both type valves are tested in combustors of multiple lengths. Close examination of the respective valve motions indicate that the reed valve is highly non-linear, with unique attributes that appear essential for self-aspiration. Dynamic models for the motion of each valve are implemented in a computational fluid dynamic (CFD) simulation of the pulse combustor in order to assess if this unique valve motion is critical to successful operation. The results show that it is. The implications of these results are discussed. The need for active actuation with feedback control, rather than passive valve actuation is highlighted as a critical technology for practical resonant pulse combustors.

Combustion↗
NASA NTRS2016

Numerical Evaluation of an Ejector-Enhanced Resonant Pulse Combustor with a Poppet Inlet Valve and a Converging Exhaust Nozzle

A computational investigation of a pressure-gain combustor system for gas turbine applications is presented. The system consists of a valved pulse combustor and an ejector, housed within a shroud. The study focuses on two enhancements to previous models, related to the valve and ejector components. First, a new poppet inlet valve system is investigated, replacing the previously used reed valve configuration. Secondly, a new computational approach to approximating the effects of choked turbine inlet guide vanes present immediately downstream of the Ejector-Enhanced Resonant Pulse Combustor (EERPC) is investigated. Instead of specifying a back pressure at the EERPC exit boundary (as was done in previous studies) the new model adds a converging-diverging (CD) nozzle at the exit of the EERPC. The throat area of the CD nozzle can be adjusted to obtain the desired back pressure level and total mass flow rate. The results presented indicate that the new poppet valve configuration performs nearly as well as the original reed valve system, and that the addition of the CD nozzle is an effective method to approximate the exit boundary effects of a turbine present downstream of the EERPC. Furthermore, it is shown that the more acoustically reflective boundary imposed by a nozzle as compared to a constant pressure surface does not significantly affect operation or performance.

Computational Fluid Dynamics (CFD↗
NASA NTRS2017

Resonant Pulse Combustors: A Reliable Route to Practical Pressure Gain Combustion

A particular type of pressure gain combustion (PGC) device is described, which is under investigation at GRC. The Resonant Pulse Combustor (RPC) has been largely overlooked due to its theoretically low performance. However, its practical performance is quite competitive with other PGC systems, and its physical simplicity is unmatched.

detonation↗
NASA NTRS2018

Resonant Pulse Combustors: A Reliable Route to Practical Pressure Gain Combustion

Pressure Gain Combustion (PGC) defined: A fundamentally unsteady process whereby gas expansion by heat release is constrained, causing a rise in stagnation pressure and allowing work extraction by expansion to the initial pressure. A particular type of pressure gain combustion (PGC) device is described, which is under investigation at GRC (Glenn Research Center). The Resonant Pulse Combustor (RPC) has been largely overlooked due to its theoretically low performance. However, its practical performance is quite competitive with other PGC systems, and its physical simplicity is unmatched.

combustion↗
NASA NTRSDate not supplied

Resonant Pulse Combustors: A Reliable Route to Practical Pressure Gain Combustion

Pressure Gain Combustion (PGC) defined: A fundamentally unsteady process whereby gas expansion by heat release is constrained, causing a rise in stagnation pressure and allowing work extraction by expansion to the initial pressure. A particular type of pressure gain combustion (PGC) device is described, which is under investigation at GRC (Glenn Research Center). The Resonant Pulse Combustor (RPC) has been largely overlooked due to its theoretically low performance. However, its practical performance is quite competitive with other PGC systems, and its physical simplicity is unmatched.

combustion↗
NASA NTRS2008

Operability of an Ejector Enhanced Pulse Combustor in a Gas Turbine Environment

A pressure-gain combustor comprised of a mechanically valved, liquid fueled pulsejet, an ejector, and an enclosing shroud, was coupled to a small automotive turbocharger to form a self-aspirating, thrust producing gas turbine engine. The system was constructed in order to investigate issues associated with the interaction of pulsed combustion devices and turbomachinery. Installed instrumentation allowed for sensing of distributed low frequency pressure and temperature, high frequency pressure in the shroud, fuel flow rate, rotational speed, thrust, and laboratory noise. The engine ran successfully and reliably, achieving a sustained thrust of 5 to 6 lbf, and maintaining a rotor speed of approximately 90,000 rpm, with a combustor pressure gain of approximately 4 percent. Numerical simulations of the system without pressure-gain combustion indicated that the turbocharger would not operate. Thus, the new combustor represented a substantial improvement in system performance. Acoustic measurements in the shroud and laboratory indicated turbine stage sound pressure level attenuation of 20 dB. This is consistent with published results from detonative combustion experiments. As expected, the mechanical reed valves suffered considerable damage under the higher pressure and thermal loading characteristics of this system. This result underscores the need for development of more robust valve systems for this application. The efficiency of the turbomachinery components did not appear to be significantly affected by unsteadiness associated with pulsed combustion, though the steady component efficiencies were already low, and thus not expected to be particularly sensitive.

Paxson, Daniel E.↗
NASA NTRS2001

Laser High-Cycle Thermal Fatigue of Pulse Detonation Engine Combustor Materials Tested

Pulse detonation engines (PDE's) have received increasing attention for future aerospace propulsion applications. Because the PDE is designed for a high-frequency, intermittent detonation combustion process, extremely high gas temperatures and pressures can be realized under the nearly constant-volume combustion environment. The PDE's can potentially achieve higher thermodynamic cycle efficiency and thrust density in comparison to traditional constant-pressure combustion gas turbine engines (ref. 1). However, the development of these engines requires robust design of the engine components that must endure harsh detonation environments. In particular, the detonation combustor chamber, which is designed to sustain and confine the detonation combustion process, will experience high pressure and temperature pulses with very short durations (refs. 2 and 3). Therefore, it is of great importance to evaluate PDE combustor materials and components under simulated engine temperatures and stress conditions in the laboratory. In this study, a high-cycle thermal fatigue test rig was established at the NASA Glenn Research Center using a 1.5-kW CO2 laser. The high-power laser, operating in the pulsed mode, can be controlled at various pulse energy levels and waveform distributions. The enhanced laser pulses can be used to mimic the time-dependent temperature and pressure waves encountered in a pulsed detonation engine. Under the enhanced laser pulse condition, a maximum 7.5-kW peak power with a duration of approximately 0.1 to 0.2 msec (a spike) can be achieved, followed by a plateau region that has about one-fifth of the maximum power level with several milliseconds duration. The laser thermal fatigue rig has also been developed to adopt flat and rotating tubular specimen configurations for the simulated engine tests. More sophisticated laser optic systems can be used to simulate the spatial distributions of the temperature and shock waves in the engine. Pulse laser high-cycle thermal fatigue behavior has been investigated on a flat Haynes 188 alloy specimen, under the test condition of 30-Hz cycle frequency (33-msec pulse period and 10-msec pulse width including a 0.2-msec pulse spike; ref. 4). Temperature distributions were calculated with one-dimensional finite difference models. The calculations show that that the 0.2-msec pulse spike can cause an additional 40 C temperature fluctuation with an interaction depth of 0.08 mm near the specimen surface region. This temperature swing will be superimposed onto the temperature swing of 80 C that is induced by the 10-msec laser pulse near the 0.53-mm-deep surface interaction region.

Zhu, Dong-Ming↗
DOE OSTI2021

Comparative Study for Pressure Gain Combustion-Gas Turbine System Performance in NGCC Configurations

The Department of Energy (DOE) has a goal to increase natural gas combined cycle (NGCC) plant efficiency to greater than 70 percent on a lower heating value (LHV) basis. Improvement in gas turbine (GT) efficiency is key achieving this goal. While many of the traditional improvement methods (higher firing temperature, advanced materials, improved cooling methods, etc.) may increase current GT and NGCC efficiencies incrementally, combining these traditional advancements with breakthrough technologies such as pressure gain combustion (PGC) may provide significant system efficiency gains. PGC is a combustion process that results in a net pressure increase across the combustor (up to pressure ratio of 2.2) rather than the traditional (<5%) pressure drop. There are multiple PGC technologies being developed that create the pressure rise phenomena, including resonant pulse combustors (RPCs), pulse detonation engines (PDEs), wave rotor combustor (WRC) engines and rotating detonation engines (RDEs). In this study, scoping analyses of PGC concepts applied to NGCC power plants were performed by combining simplified analytical models for the RPC, PDE, WRC, and RDE types of pressure gain processes with a GT model to evaluate impacts of using each of the PGC technologies on key GT performance parameters. Sensitivity analyses were also performed. Ultimately, the PGC technologies were found to have the potential to increase simple cycle efficiency by 4–6 percent (absolute) and NGCC efficiency by 2–3 percent (absolute) based on the results of the current study.

03 NATURAL GAS↗
NASA NTRS2018

Pressure Gain Combustion 101

This presentation contains notes for a 30 minute lecture that is part of an AIAA Special Session titled, Pressure Gain Combustion Overview: Principles, Operation, and Applications. The presentation covers an introduction to Pressure Gain Combustion (PGC) and the devices used to implement it. The concept of PGC is discussed on a thermodynamic basis, the performance benefits are demonstrated, and methods of implementation are described. These include devices such as Resonant Pulse Combustors, Internal Combustion Wave Rotors, Pulse Detonation Engines, and Rotating Detonation Engines.

pressure gain combustion↗
NASA NTRS2019

Defining and Measuring Pressure Gain

This presentation describes experimental and computational approaches to measuring pressure gain in the various devices currently under investigation wherein the working fluid undergoes a pressure gain combustion (PGC) process. Pressure gain is essentially a measure of the fluid availability for work or thrust production. The devices covered are Resonant Pulse Combustors, Internal Combustion Wave Rotors, Pulse Detonation Engines, and Rotating Detonation Engines. The approaches to pressure gain measurement differ in each device. However, all of the approaches attempt to address the fundamental challenges of PGC system measurement: the extremely harsh environment which makes instrumentation difficult, and the temporal and spatial non-uniformity associated with the exhausting flow which makes assigning a single value to the total pressure difficult. As part of the two-day 2019 International Constant Volume and Detonative Combustion Workshop, held in conjunction with the 2019 AIAA Propulsion and Energy Forum, this presentation is intended to foster discussion and eventual consensus on acceptable measurement methods.

pressure gain combustion↗
NASA NTRS2019

Pressure Gain Combustion for High Speed Propulsion

This presentation contains notes for a one-hour lecture that is part of a two-day AIAA Short Course titled, Hypersonic Air-Breathing Propulsion: Emerging Technologies and Cycles. The presentation covers an introduction to Pressure Gain Combustion (PGC) and its applicability to high speed airbreathing propulsion (HSABP). The concept of PGC is discussed on a thermodynamic basis, the performance benefits are demonstrated, and methods of implementation are described. These include devices such as Resonant Pulse Combustors, Internal Combustion Wave Rotors, Pulse Detonation Engines, and Rotating Detonation Engines.

pressure gain combustion↗