Review on the Rotating Detonation Engine and It’s Typical Problems

Detonation is a promising combustion mode to improve engine performance, increase combustion efficiency, reduce emissions, and enhance thermal cycle efficiency. Over the last decade, significant progress has been made towards the applications of detonation mode in engines, such as standing detonation engine (SDE), Pulse detonation engine (PDE) and rotating detonation engine (RDE), and the understanding of the fundamental chemistry and physics processes in detonation engines via experimental and numerical studies. This article is to provide a comprehensive overview of the progress in the knowledge of rotating detonation engine from the different countries. New observations of injection, ignition, and geometry of combustor, pressure feedback, and combustion modes of RDE have been reported. These findings and advances have provided new opportunities in the development of rotating detonation for practical applications. Finally, we point out the current gaps in knowledge to indicate which areas future research should be directed at

Rotating Detonation Combustion: A Computational Study for Stationary Power Generation

The increased availability of gaseous fossil fuels in The US has led to the substantial growth of stationary Gas Turbine (GT) usage for electrical power generation. In fact, from 2013 to 2104, out of the 11 Tera Watts-hour per day produced from fossil fuels, approximately 27% was generated through the combustion of natural gas in stationary GT. The thermodynamic efficiency for simple-cycle GT has increased from 20% to 40% during the last six decades, mainly due to research and development in the fields of combustion science, material science and machine design. However, additional improvements have become more costly and more difficult to obtain as technology is further refined. An alternative to improve GT thermal efficiency is the implementation of a combustion regime leading to pressure-gain; rather than pressure loss across the combustor. One concept being considered for such purpose is Rotating Detonation Combustion (RDC). RDC refers to a combustion regime in which a detonation wave propagates continuously in the azimuthal direction of a cylindrical annular chamber. In RDC, the fuel and oxidizer, injected from separated streams, are mixed near the injection plane and are then consumed by the detonation front traveling inside the annular gap of the combustion chamber. The detonation products then expand in the azimuthal and axial direction away from the detonation front and exit through the combustion chamber outlet.;In the present study Computational Fluid Dynamics (CFD) is used to predict the performance of Rotating Detonation Combustion (RDC) at operating conditions relevant to GT applications. As part of this study, a modeling strategy for RDC simulations was developed. The validation of the model was performed using benchmark cases with different levels of complexity. First, 2D simulations of non-reactive shock tube and detonation tubes were performed. The numerical predictions that were obtained using different modeling parameters were compared with analytical solutions in order to quantify the numerical error in the simulations. Additionally, experimental data from laboratory scale combustors was used to validate 2D and 3D numerical simulations. The effects of different modeling parameters on RDC predictions was also studied. The validated simulation strategy was then used to assess the performance of RDC for different combustion chamber geometries and operating conditions relevant to GT applications. As a result, the limiting conditions for which continuous detonation and pressure gain combustion can be achieved were predicted and the effect of operating conditions on flow structures and RDC performance was assessed.;The modeling strategy and the results from this study could be further used to design more efficient and more stable RDC systems

Primary Investigation on Ram-Rotor Detonation Engine

The study presents a new type of detonation engine called the Ram-Rotor Detonation Engine (RRDE), which overcomes some of the drawbacks of conventional detonation engines such as pulsed detonation engines, oblique detonation engines, and rotating detonation engines. The RRDE organizes the processes of reactant compression, detonation combustion, and burned gas expansion in a single rotor, allowing it to achieve an ideal detonation cycle under a wide range of inlet Mach numbers, thus significantly improving the total pressure gain of the propulsion system. The feasibility and performance of RRDE are discussed through theoretical analysis and numerical simulations. The theoretical analysis indicates that the performance of the RRDE is mainly related to the inlet velocity, the rotor rim velocity and the equivalence ratio of reactant. Increasing the inlet velocity leads to a decrease in the total pressure gain of the RRDE. Once the inlet velocity exceeds the critical value, the engine cannot achieve positive total pressure gain. Increasing the rim velocity can improve the total pressure gain and the thermodynamic cycle efficiency of RRDE. Increasing the equivalence ratio can also improve the thermodynamic cycle efficiency and enhance the total pressure gain at lower inlet velocities. While, at higher inlet velocities, increasing the equivalence ratio may reduce the total pressure gain. Numerical simulations are also performed to analyze the detailed flow field structure in RRDE and its variations with the inlet parameters. The simulation results demonstrate that the detonation wave can stably stand in the RRDE and can adapt to the change of the inlet equivalence ratio within a certain range. This study provides preliminary theoretical basis and design reference for the RRDE

Detonation Confinement in a Radial Rotating Detonation Engine

Radial Rotating Detonation Engines (RRDE) have provided an opportunity for use of a pressure-gain combustor in a more compact form compared to an axial RDE. A successfully tested RRDE has operated over a wide range of test conditions and produced detonation modes with one, two, and three waves. The presence of multiple waves located the detonation waves to the outer radius, while one wave modes operated closer to the inner radius. Locating the detonation wave closer to the inner diameter resulted in less time for combustion prior to the radial turbine. Subsequently, this tended to decrease efficiency. To attempt to alleviate this, the detonation chamber area was modified from its constant area design to a decreasing area design as the flow travelled radially inward to confine the detonation wave to a more radially out- ward position. The detonation chamber featured a at channel plate that reduced the flow\u27s effective cross-sectional area by almost 65% from its inlet to the turbine inlet plane. The constant channel height improved total pressure loss as high as 92% over the constant area geometry for similar ow conditions and increased the RRDEs ability to operate at larger channel heights. Guide vanes were introduced downstream of the combustion section by modifying the at channel plate with modular channel plates. This configuration attempted to provide a combustion section with a confined detonation and a transition section to the guide vanes and nozzle. While in this configuration, the RRDE operated at both detonative and acoustic wave modes. Thin-filament pyrometry (TFP) was also performed to measure transient temperature responses during operation. The successful implementation of the filaments provided temperature measurements during detonative modes up to 2194 K at the guide vanes and frequency responses captured through TFP between 1.6-5.9 kHz

Summary of Pressure Gain Combustion Research at NASA

NASA has undertaken a systematic exploration of many different facets of pressure gain combustion over the last 25 years in an effort to exploit the inherent thermodynamic advantage of pressure gain combustion over the constant pressure combustion process used in most aerospace propulsion systems. Applications as varied as small-scale UAV's, rotorcraft, subsonic transports, hypersonics and launch vehicles have been considered. In addition to studying pressure gain combustor concepts such as wave rotors, pulse detonation engines, pulsejets, and rotating detonation engines, NASA has studied inlets, nozzles, ejectors and turbines which must also process unsteady flow in an integrated propulsion system. Other design considerations such as acoustic signature, combustor material life and heat transfer that are unique to pressure gain combustors have also been addressed in NASA research projects. In addition to a wide range of experimental studies, a number of computer codes, from 0-D up through 3-D, have been developed or modified to specifically address the analysis of unsteady flow fields. Loss models have also been developed and incorporated into these codes that improve the accuracy of performance predictions and decrease computational time. These codes have been validated numerous times across a broad range of operating conditions, and it has been found that once validated for one particular pressure gain combustion configuration, these codes are readily adaptable to the others. All in all, the documentation of this work has encompassed approximately 170 NASA technical reports, conference papers and journal articles to date. These publications are very briefly summarized herein, providing a single point of reference for all of NASA's pressure gain combustion research efforts. This documentation does not include the significant contributions made by NASA research staff to the programs of other agencies, universities, industrial partners and professional society committees through serving as technical advisors, technical reviewers and research consultants

Thermodynamics of a Rotating Detonation Engine

A practical thermodynamic cycle model of a rotating detonation engine (RDE) is developed for the purpose of predicting performance and understanding flow field behavior. The cycle model is based on a heuristic analysis of a RDE numerical simulation. The model is compared to the simulation and to laboratory experiment with good results. The RDE constrains a detonation wave to rotate inside a cylindrical annulus, has no moving parts and requires a single ignition sequence. Thrust is produced continuously and at high frequency. The simplicity of the RDE offers the possibility of a practical detonation engine with efficiencies that exceed conventional Brayton cycles. A RDE numerical simulation (courtesy of the Naval Research Laboratory) is post-processed to yield the underlying thermodynamics. The time-accurate numerical simulation is averaged over many cycles. A Galilean transformation is applied to the time-averaged solution to produce a solution field in the rotating frame of reference. Streamlines are created in the transformed solution field. Velocity, pressure and temperature are extracted along the streamlines. Pressure-volume and enthalpy-entropy diagrams are plotted to expose the simulation thermodynamics. The results are found to be consistent with the conservation of rothalpy as the fundamental statement of the conservation of energy in a rotating frame of reference. The signature of rothalpy in the RDE is shown to be a small amount of azimuthal flow or swirl. The change in flow field swirl is shown to be proportional to the change in stagnation enthalpy and consistent with the Euler turbomachinery equation. The simulation analysis supports the construction of an analytical model based on a modified ZND (Zel’dovich-von Neumann-Döring) detonation theory. This theory is combined with the concept of rothalpy. The result is a realistic thermodynamic cycle model with a theoretical basis for performance prediction and an explanation of the flow field structure. The RDE cycle model is analytical, thermodynamically one-dimensional, steady-state, and independent of geometry and heat release rate. The performance of the modified ZND cycle model is within 3% of the numerical simulation and in good quantitative agreement with experimental test results at the Air Force Research Laboratory Detonation Engine Research Facility

Characteristics of Rotating Detonation Engines for Propulsion and Power Generation

Conventional engines are limited by the efficiency of their combustion mode. Compared to present constant pressure deflagration-based engines, detonation-based systems can realize a higher thermodynamic cycle efficiency, making them an attractive candidate for next generation propulsion systems that will take humanity to hypersonic speeds and even to Mars. For all its performance gains, detonation engines are still far off from implementation. One system, the rotating detonation engine (RDE) is promising as a detonation-based engine concept for its stability, simplicity, and versatility. For these reasons, RDEs have been the subject of studies internationally in efforts to understand their operation and integration into conventional technology. RDEs are on the cusp of field use, considered at technology readiness level 5 with prototype demonstrations occurring today; however, there are still significant barriers holding back this technology from widespread adoption. The work of this dissertation confronts each of these barriers with experimental methods. Using multiple different RDE test facilities, investigations into injection, fueling, exhaust, detonability, and integration were conducted, targeting research gaps in each barrier. As a result, many novel advancements have been made from these studies such as the first demonstration of hydrogen and oxygen rotating detonations, the detonability of sustainable solid particle fuels, and the effect of fuel stratification on rotating detonation propagation. Altogether, the work presented depicts the RDE from a complete perspective by advancing current RDE research through multiple channels with the intention of advancing the technology readiness level of RDEs

Numerical Assessment of the Convective Heat Transfer in Rotating Detonation Combustors Using a Reduced-Order Model

The pressure gain across a rotating detonation combustor offers an efficiency rise and potential architecture simplification of compact gas turbine engines. However, the combustor walls of the rotating detonation combustor are periodically swept by both detonation and oblique shock waves at several kilohertz, disrupting the boundary layer, resulting in a rather complex convective heat transfer between the fluid and the solid walls. A computationally fast procedure is presented to calculate this extraordinary convective heat flux along the detonation combustor. First, a numerical model combining a two-dimensional method of characteristics approach with a monodimensional reaction model is used to compute the combustor flow field. Then, an integral boundary layer routine is used to predict the main boundary layer parameters. Finally, an empirical correlation is adopted to predict the convective heat-transfer coefficient to obtain the bulk and local heat flux. The procedure has been applied to a combustor operating with premixed hydrogen-air fuel. The results of this approach compare well with high-fidelity unsteady Reynolds-averaged Navier-Stokes three-dimensional simulations, which included wall refinement in an unrolled combustor. The model demonstrates that total pressure has an important influence on heat flux within the combustor and is less dependent on the inlet total temperature. For an inlet total pressure of 0.5 MPa and an inlet total temperature of 300 K, a peak time-averaged heat flux of 6 MW/m2 was identified at the location of the triple point, followed by a decrease downstream of the oblique shock, to about 4 MW/m2. Maximum discrepancy between the reduced-order model and the high-fidelity solver was 16%, but the present reduced-order model required a computational time of only 200 s, that is, about 7000 times faster than the high-fidelity three-dimensional unsteady solver. Therefore, the present tool can be used to optimize the combustor cooling system

Performance analysis of turbocharger effect on engine in local cars

The performance of a gasoline-fueled internal combustion engines can be increased with the use of a turbocharger. However, the amount of performance increment for a particular engine should be studied so that the advantages and drawbacks of turbocharging will be clarified. This study is mainly concerned on the suitable turbocharger unit selection, engine conversions required and guidelines for testing a Proton 4G92 SOHC 1.6-litre naturally aspirated gasoline engine. The engine is tested under its stock naturally aspirated condition and after been converted to turbocharged condition. The effect of inter cooled turbocharged condition is also been tested. Boost pressure is the main parameter in comparing the performance in different conditions as it influences the engine torque, power, efficiency and exhaust emissions. The use of a turbocharger on this test engine has clearly increased its performance compared to its stock naturally aspirated form. The incorporation of an intercooler to the turbocharger system increases the performance even further. With the worldwide effort towards environmental-friendly engines and fossil fuel shortage, the turbocharger can help to create engines with enhanced performance,minimum exhaust emissions and maximum fuel economy