Pressure Gain Combustion Research Articles

Operation and Power Generation of a Disk-Shaped Pressure Gain Combustor

The objective of this experimental study is to evaluate the power generation capability of an ethylene–air disk-shaped pressure gain combustor (DPGC). The main content of this paper focuses on discussing the DPGC testing results, consisting of detonation wave dynamics, power generation, and accompanying combustion instabilities. The experiments can be grouped into two stages. In the first stage, the DPGC was tested under atmospheric back condition. Continuous detonation wave dynamics were evaluated among various testing conditions. Evolution of the detonation wave velocity with respect to changes in the equivalence ratio has been discussed. In the second stage of the experiments, the DPGC was tested with a turbocharger installed. Shaft power extracted by the turbocharger turbine from the DPGC exhaust was used as a metric for evaluating the DPGC power output. During the operation of the DPGC and turbocharger, low- and intermediate-frequency combustion instabilities were observed, which coexisted with the high-frequency component associated with the circumferentially propagating detonation wave. The experimental results suggest that the DPGC shows superiority in compactness relative to conventional combustion power systems. However, more improvements need to be made with regard to overall thermal efficiency in order to achieve the benefits from detonation combustion.

The hybrid concept of turboshaft engine working according to Humphrey cycle dedicated to variety power demand – CFD analysis

The paper presents a new concept of the turbine engine in the area of pressure gain combustion (PGE). The engine works according to Humphrey’s cycle. Minor modification in construction has allowed power generation of 500 kW, 700 kW, 1000 kW, and 1800 kW. The concept successfully resolved the challenges related to the temporary opening and closing of the combustion chamber. The presented valve timing system has ensured effective gas flow and what stands behind it, an effective process of conversion of a high-pressure gas impulse into mechanical energy. Rotating combustion chambers enabled the application of an effective sealing system. The concept characterizes simple construction and potentially low power-to-weight coefficient. The CFD numerical analysis of the presented engine concept showed very promising effective efficiency and low specific fuel consumption.

Stability Characteristics of an Actively Valved Resonant Pulse Combustor

Abstract Resonant pulse combustors, one of the deflagration-based pressure gain combustion devices, can significantly increase thermal efficiency in gas turbine engines. This experimental study investigates the stability characteristics of a newly designed actively valved resonant pulse combustor, capable of sustained operation and meaningful stagnation pressure gain. The resonant pulse combustor was fired with liquid gasoline fuel while ion and pressure sensors captured the temporally resolved heat release and chamber pressure. First, experimental results were used to demonstrate the general operating principle of the combustor. Then, the stability characteristics of the device were investigated through frequency domain analysis of the ion probe and pressure signal traces. A low frequency oscillation (also observed in steady flames and passively valved resonant pulse combustors), was observed as the device was brought near to its blowout limit. Finally, an index was defined to predict the stability characteristics of the resonant pulse combustor by quantifying the competition between low frequency oscillations and combustion-driven resonance. Experimental results demonstrated the ability of this index to provide early prediction of a blowout event for this device.

Techno-economic analysis of innovative solutions for island grids with high renewable solar share

This paper presents a techno-economic analysis of a hybrid dispatch strategy on an island through conventional internal combustion engine (ICE) and innovative gas turbine (GT) with pressure gain combustion (PGC) in the presence of renewable solar-PV. Plant configurations with conventional technologies were defined based on established industrial data, and specifications of novel PGC-GT technology were estimated using the industrial data of conventional GT and on-design results available in the literature. Optimization of the operational strategy was conducted in WECoMP, a modular and flexible software tool developed by Thermochemical Power Group (TPG) at the University of Genova. The performance of different hybrid plants was analyzed in terms of annual production, fuel consumption, curtailment, CO2 emissions, cost, and sensitivity to fuel price. This is complemented by a parallel paper investigating the mechanical rotating inertia features of such prime movers, further supporting their suitability in enabling the integration of non-dispatchable renewables. Results showed that the 2-stroke ICE technology provided the best performance in terms of emissions and cost. Moreover, for all dispatchable prime movers, minimum LCOE occurred at an optimum value of PV capacity that facilitated annual CO2 reduction by 58.6 kton and LCOE reduction by 8.9 €/MWh. Finally, the optimum PV capacity was found to increase with fuel price, signifying the environmental benefits of high fuel prices.

Large Eddy Simulation of a Pistonless Constant Volume Combustor: A New Concept of Pressure Gain Combustion

Abstract Classical gas turbine thermodynamic cycle has undergone no change over the last decades. The most important efficiency improvements have been obtained by reducing thermal losses and raising the overall pressure ratio and peak temperature. Pressure gain combustion (PGC) represents an increasingly interesting solution to break out current technological limits. Indeed cycle models show that a pressure raise across the combustion process would reduce fuel consumption, increasing efficiency. Providing an efficiency close to the corresponding detonative technological concepts, constant volume combustion (CVC) represents a viable solution that still needs to be studied. In this work, the CV2 (constant-volume combustion vessel) installed at the Pprime laboratory (France) is numerically investigated using the high-fidelity compressible large eddy simulation (LES) solver AVBP. All the successive phases of the CVC cycle, i.e., air intake, fuel injection, spark-ignited combustion, and exhaust, are considered in the LES. Intake and exhaust valves are properly represented by novel boundary conditions able to mimic the valves impact on the flow without the need to directly consider their presence and dynamics during the simulation, reducing the computational costs. The spark ignition is modeled as an energy deposition term added to the energy equation. The combustion phase is treated by the dynamic version of the thickened flame model (DTFLES) extended to deal with nonconstant pressure combustion. Time-resolved particle imaging velocimetry (PIV) and pressure measurement inside the chamber reveal that cold and reactive turbulent flow are well captured in all the phases, showing the reliability of the approach and the models used.

Nonidealities in Rotating Detonation Engines

A rotating detonation engine (RDE) is a realization of pressure-gain combustion, wherein a traveling detonation wave confined in a chamber provides shock-based compression along with chemical heat release. Due to the high wave speeds, such devices can process high mass flow rates in small volumes, leading to compact and unconventional designs. RDEs involve unsteady and multiscale physics, and their operational characteristics are determined by an equilibrium between large- and small-scale processes. While RDEs can provide a significant theoretical gain in efficiency, achieving this improvement requires an understanding of the multiscale coupling. Specifically, unavoidable nonidealities, such as unsteady mixing, secondary combustion, and multiple competing waves associated with practical designs, need to be understood and managed. The secondary combustion processes arise from fuel/air injection and unsteady and incomplete mixing, and can create spurious losses. In addition, a combination of multiple detonation and secondary waves compete and define the dynamical behavior of mixing, heat release distribution, and the overall mode of operation of the device. This review discusses the current understanding of such nonidealities and describes the tools and techniques used to gain insight into the extreme unsteady environment in such combustors.

Preliminary Criterion for Positive Total Pressure Gain in Kerosene/Air Rotating Detonation Combustor

The rotating detonation combustor is promising to be a total pressure gain combustor and receives considerable attention in the past decade. Many studies have pointed out that the pressure gain performance is significantly related to the inlet area ratio, whereas no criterion for obtaining positive total pressure gain has been established until now. This study performed a series of numerical simulations to investigate the idealized total pressure gain performance of vapor kerosene/air rotating detonation combustor by varying the inlet area ratios and injection total pressures. A preliminary criterion for obtaining positive total pressure gain in vapor kerosene/air rotating detonation combustor is established and then validated with simulation cases and existing research. The results indicate that the total pressure gain increases with the increase of the inlet area ratio and chamber diameter, whereas it decreases with the increase of the injection total pressure. The established criterion can serve as a reference value for the design of the vapor kerosene/air rotating detonation combustor, above which a positive total pressure gain can be obtained.

An Optimization Methodology for Turbines Driven by Pulsed Detonation Combustors

Abstract A step-change in efficiency of gas turbine technology and, subsequently, an emissions reduction from this technology requires conceptual changes. Substituting conventional combustion chambers with pressure gain combustion in the form of pulsed detonation combustion (PDC) is one of the promising methods that can reduce gas turbine emissions significantly. Nevertheless, the component matching for the respective systems and specifically that of turbine expanders working with the exhaust flow of PDC tubes is still not solved. The unsteady nature of PDC exhaust flow makes 3D-CFD simulations too expensive to be applied in optimization loops in early design stages. To address this question, the present paper introduces a new cost-effective but reliable methodology for turbine analysis and optimization, based on the unsteady exhaust flow of pulsed detonation combustors. The methodology unitizes a robust unsteady one-dimensional solver, a meanline performance analysis, and an adaptive surrogate optimization algorithm. A two-stage axial turbine is optimized considering all unsteady flow features of a hydrogen-air PDC configuration with five PDC tubes. A three-dimensional URANS simulation is performed for the optimized geometry and the baseline to evaluate the methodology. The results showed that the optimized turbine produces 16% lower entropy than the original one. Additionally, the turbine output power is increased by 14% by the optimized design. Based on the results, it is concluded that the approach is fast and reliable enough to be applied in optimizing any turbine working with unsteady flows, more specifically in PDC applications.

Design and Parametric Analysis of a Supersonic Turbine for Rotating Detonation Engine Applications

Pressure gain combustion is a promising alternative to conventional gas turbine technologies and within this class the Rotating Detonation Engine has the greatest potential. The Fickett–Jacobs cycle can theoretically increase the efficiency by 15% for medium pressure ratios, but the combustion chamber delivers a strongly non-uniform flow; in these conditions, conventionally designed turbines are inadequate with an efficiency below 30%. In this paper, an original mean-line code was developed to perform an advanced preliminary design of a supersonic turbine; self-starting capability of the supersonic channel has been verified through Kantrowitz and Donaldson theory; the design of the supersonic profile was carried out employing the Method of Characteristics; an accurate evaluation of the aerodynamic losses has been achieved by considering shock waves, profile, and mixing losses. Afterwards, an automated Computational Fluid Dynamics (CFD) based optimization process was developed to find the optimal loading condition that minimizes losses while delivering a sufficiently uniform flow at outlet. Finally, a novel parametric analysis was performed considering the effect of inlet angle, Mach number, reaction degree, peripheral velocity, and blade height ratio on the turbine stage performance. This analysis has revealed for the first time, in authors knowledge, that this type of machines can achieve efficiencies over 70%.

Theoretical Performance of Gas Turbines Operating with Pressure-Gain Combustion

Theoretical Performance of Gas Turbines Operating with Pressure-Gain Combustion

Numerical study on the interaction characterization of rotating detonation wave and turbine rotor blades

Rotating detonation as a kind of pressure gain combustion is expected to greatly improve efficiency when applied to gas turbine engines. In this paper, the operation of rotating detonation combustor and turbine rotor blade was studied. Firstly, the analysis of the interaction between detonation wave and turbine blade shows that the compression of gas by detonation wave and reflected wave will lead to a sharp increase in the temperature at the wall of blade. When the detonation wave propagates, the oscillation amplitudes of pressure and temperature at the turbine inlet are 70% and 75% respectively, and the detonation oblique shock will change the flow trajectory of the air flow, resulting in the flow direction deviating from the incident angle. Then the comparison between detonation and deflagration shows that the total pressure of detonation is higher and will have greater work potential. The torque generated by the blades under detonation has the characteristics of high-frequency oscillation, which may be detrimental to the operation of the engine.

Binary Repetitive Model Predictive Active Flow Control Applied to an Annular Compressor Stator Cascade With Periodic Disturbances

Abstract Novel pressure gain combustion concepts invoke periodic flow disturbances in a gas turbine's last compressor stator row. This contribution presents studies of mitigation efforts on the effects of these periodic disturbances on an annular compressor stator rig. The passages were equipped with pneumatic active flow control (AFC) influencing the stator blade's suction side, and a rotating throttling disk downstream of the passages inducing periodic disturbances. For steady blowing, it is shown that with increasing actuation amplitudes cμ, the extension of a hub corner vortex deteriorating the suction side flow can be reduced, resulting in an increased static pressure rise coefficient Cp of a passage. The effects of the induced periodic disturbances could not be addressed intrinsically, by using steady blowing actuation, Considering a corrected total pressure loss coefficient ζ*, which includes the actuation effort, the stator row's efficiency decreases with higher cμ due to the increasing costs of the actuation mass flow. Therefore, a closed-loop approach is presented to address the effects of the disturbances more specifically, thus lowering the actuation cost, i.e., mass flow. For this, a repetitive model predictive control (RMPC) was applied, taking advantage of the periodic nature of the induced disturbances. The presented RMPC formulation is restricted to a binary control domain to account for the used solenoid valves' switching character. An efficient implementation of the optimization within the RMPC is presented, which ensures real-time capability. As a result, Cp increases in a similar magnitude but with a lower actuation mass flow of up to 66%, resulting in a much lower ζ* for similar values of cμ.

Oblique detonation wave triggered by a double wedge in hypersonic flow

Pressure-gain combustion has gained attention for airbreathing ramjet engine applications owing to its better thermodynamic efficiency and fuel consumption rate. In contrast with traditional detonation induced by a single wedge, the present study considers oblique shock interactions attached to double wedges in a hypersonic combustible flow. The temperature/pressure increases sharply across the interaction zone that initiates an exothermic reaction, finally resulting in an Oblique Detonation Wave (ODW). Compared with the case for a single-wedge ODW, the double-wedge geometry has great potential to control the initiation of the ODW. As a tentative study, two-dimensional compressible Euler equations with a two-step induction-reaction kinetic model are used to solve the detonation dynamics triggered by a double wedge. The effects of the wedge angles and wedge corner locations on the initiation structures are investigated numerically. The results show an ODW complex comprising three Oblique Shock Waves (OSWs), an induction zone, a curved detonation front, and an unburned/low-temperature gas belt close to the surface of the second wedge. Both the increasing wedge angle and downstream wedge corner location lead to an abrupt OSW–ODW transition type, whereas the former corresponds to the shock–shock interaction and the later has a greater effect on the exothermic chemical process. Analysis of the shock polar and flow scale confirms that the OSW–ODW initiation structure mainly depends on the coupling of shocks and heat release in a confined initiation zone.

Pressure gain combustion

Pressure gain combustion

RDE research and development in Poland

A very short survey of research conducted in Poland on the development of the rotating detonation engine (RDE) is presented. Initial studies conducted in cooperation with Japanese partners lead to development of a joint patent on RDE. Then, an intensive basic and applied research was started at the Institute of Heat Engineering of the Warsaw University of Technology. One of the first achievements was the demonstration of performance of the rocket engine with an aerospike nozzle utilizing continuously rotating detonation (CRD), and research was directed into development of a small turbofan engine utilizing such a combustion regime. These activities promoted international cooperation and stimulated RDE development not only in Poland but also in other countries. A research directed to measure and calculate flow parameters as well as to analyze the use of liquid fuels was conducted. In the Institute of Aviation in Warsaw, research on the application of the CRD to turbine engines as well as rocket, ramjet, and combined cycle engines was carried out. In the paper, a special emphasis is given to international cooperation in this area with partners from many countries engaged in the development of the pressure gain combustion to propulsion systems.

A robust one-dimensional approach for the performance evaluation of turbines driven by pulsed detonation combustion

Among the solutions to reduce emissions from stationary gas turbines, replacing conventional combustion through pressure gain combustion is one of the most promising options. Nevertheless, coupling pressure gain combustion with a turbine can result in increased losses within the cycle, mainly because of the resulting very unsteady turbine inflow conditions. A reliable simulation tool can help to overcome this challenge and optimize turbine geometries and designs for the specific application. The harsh unsteady flow downstream of pressure gain combustors makes three-dimensional CFD computationally expensive. Thus, the development of a fast computational method is crucial. This paper introduces and explores such an alternative methodology. A one-dimensional Euler gas dynamic approach is combined with blade source terms, computed out of a steady-state turbine meanline analysis. To evaluate the methodology, three-dimensional CFD simulations are performed in parallel and the results are compared with those of the 1D method. The energy extraction of a turbine expander is computed with both methods for three different configurations of pulsed detonation combustor arrays connected at the turbine inlet. The results show that the proposed approach is capable of simulating the turbine in such an unsteady environment accurately. Additionally, it is indicated that around 45% of the total unsteadiness is damped throughout the first blade row, which is almost irrespective of the inlet fluctuation amplitude. Due to its accuracy and very low computational cost, the developed methodology can be integrated into optimization loops in the early design and development stages of turbomachinery for pressure gain combustion applications.

A fast approach for unsteady compressor performance simulation under boundary condition caused by pressure gain combustion

• Introduction of a coupled numerical scheme of 0D-plenum and 1D-pulsed detonation combustion tubes. • Compressor simulation with unsteady boundary condition caused by pressure gain combustion. • Unsteady 1D-Euler results match those computed by unsteady 3D-CFD. • 90% of the fluctuation’s amplitude is damped across four stages of the compressor. • Stability evaluation of a compressor exposed to pulsed detonation combustion. The constant pressure combustion of the Joule cycle is a dominant source of losses in gas turbines. One possible improvement is pressure gain combustion through pulse detonation combustion. However, the total pressure increase is the result of a transient periodic process that can adversely affect the performance of adjoining turbo components. The thermodynamic benefits of pressure gain combustion can thus be undermined by low efficiencies of compressor and turbine. In order to account for such unsteady effects early in the design process, suitable methods are essential. Given 3D-CFD simulations’ undue computational demands, an approach with low computation resources is required for first-order estimates. This paper introduces such an approach based on a 1D-Euler method and demonstrates its applicability. A compressor is simulated with 3D-CFD, which serves as a reference, as well as with the 1D-Euler code employing unsteady outlet boundary conditions that approximate those encountered with pulse detonation combustion. The findings suggest that the 1D-Euler code is able to accurately capture the transient compressor behaviour. Though the relative pressure amplitude at the compressor outlet of 3.6% is attenuated by 90% up to the compressor inlet, it still results in a compressor isentropic efficiency loss of 0.8 percentage points.

Experimental and low-dimensional numerical study on the application of conventional NOx reduction methods in pulse detonation combustion

Although research interest in pressure gain combustion (PGC) remains high, information on pollutant emissions from detonation-based devices such as pulse detonation engines is sparse, especially lacking extensive experimental parameter studies. Nevertheless, available results indicate potentially very high exhaust levels of nitrogen oxides (NOx) due to the significantly increased combustion temperatures and pressures induced by the detonation wave. To counter this issue, this study applies conventional NOx reducing measures in the form of fuel-lean mixtures and nitrogen dilution (emulating exhaust gas recirculation) to a pulse detonation combustor in multi-cycle operation. Their impact on the exhaust gas composition is measured and compared to numerical predictions by two available simplified models. To allow for a broader range of comparison and better assess the capabilities of these numerical models, emissions from fuel-rich and oxygen-enriched mixtures are measured as well. Experimental results confirm high levels of NOx up to several thousand ppm for near-stoichiometric, undiluted mixtures. When conventional NOx reduction measures are applied, significant NOx abatement can be achieved, with further reduction potential primarily limited by unsuccessful deflagration to detonation transition (DDT). Comparison with numerical results shows that simplified models allow for good qualitative agreement and can also deliver good quantitative predictions over a wide range of conditions if a suitable heat-loss model is chosen.

Controlled autoignition in stratified mixtures

The shockless explosion combustion (SEC) is a recently proposed concept aiming for pressure gain combustion through an unsteady process of multiple, distributed autoignitions occurring simultaneously. For this, a stratified fuel profile of dimethyl ether is injected into a continuous air flow. This profile is tailored such that the mixture residence time and ignition delay time are matched, allowing multiple ignition kernels to initiate simultaneously leading to an aerodynamic confinement during heat release. This work first presents an injection strategy for injecting a defined mixture profile into a convection air flow to control the local equivalence ratio throughout the combustor. Line-of-sight measurements are applied to visualize the concentration profile and subsequently used to develop a one-dimensional tool to predict the local equivalence ratio before ignition. Next, an extremum seeking control algorithm is applied to an existing SEC test rig to control the cycle averaged formation of different autoignition modes by optimizing the fuel supply. Pressure and ionization probe data indicate the successful initiation of specific modes of flame propagation by adjusting the fuel injection trajectory. The previously developed simulation tool is applied to the injection trajectories optimized by the controller. Correlating the fuel concentration distribution and the obtained autoignition modes reveal that the ignition process can be very well controlled by the fuel injection trajectory. Lastly, single representative ignition cycles are further investigated by applying optical measurement techniques to obtain OH* and CH* chemiluminescence. The results reveal a complex interaction between heat release and pressure waves influenced by temperature-dependent ignition behavior of the applied fuel. As a conclusion, four different flame propagation modes are identified, namely: turbulent deflagration, subsonic autoignition, supersonic autoignition and aerodynamic confinement by multiple simultaneous autoignition fronts.

Pulsed Impingement Turbine Cooling and Its Effect on the Efficiency of Gas Turbines With Pressure Gain Combustion

Abstract Performance improvements of conventional gas turbines are becoming increasingly difficult and costly to achieve. Pressure gain combustion (PGC) has emerged as a promising technology in this respect, due to the higher thermal efficiency of the respective ideal gas turbine cycle. Previous cycle analyses considering turbine cooling methods have shown that the application of pressure gain combustion may require more turbine cooling air. This has a direct impact on the cycle efficiency and reduces the possible efficiency gain that can potentially be harvested from the new combustion technology. Novel cooling techniques could unlock an existing potential for a further increase in efficiency. Such a novel turbine cooling approach is the application of pulsed impingement jets inside the turbine blades. In the first part of this paper, results of pulsed impingement cooling experiments on a curved plate are presented. The potential of this novel cooling approach to increase the convective heat transfer in the inner side of turbine blades is quantified. The second part of this paper presents a gas turbine cycle analysis where the improved cooling approach is incorporated in the cooling air calculation. The effect of pulsed impingement cooling on the overall cycle efficiency is shown for both Joule and PGC cycles. In contrast to the authors’ anticipation, the results suggest that for relevant thermodynamic cycles pulsed impingement cooling increases the thermal efficiency of Joule cycles more significantly than it does in the case of PGC cycles. Thermal efficiency improvements of 1.0 p.p. for pure convective cooling and 0.5 p.p. for combined convective and film with TBC are observed for Joule cycles. But just up to 0.5 p.p. for pure convective cooling and 0.3 p.p. for combined convective and film cooling with TBC are recorded for PGC cycles.