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![WR simplified design: reverse (bottom) and through (top) flow [7]](profile/Gregoire-Lenoble/publication/245392919/figure/fig1/AS:508026452967424@1498134353849/WR-simplified-design-reverse-bottom-and-through-top-flow-7.png)
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![Fig. 1 WR simplified design: reverse (bottom) and through (top) flow [7]](profile/Gregoire-Lenoble/publication/245392919/figure/fig1/AS:508026452967424@1498134353849/WR-simplified-design-reverse-bottom-and-through-top-flow-7_Q320.jpg)
![Fig. 2 WR – combustor assembly [1]](profile/Gregoire-Lenoble/publication/245392919/figure/fig2/AS:508026454056960@1498134353913/WR-combustor-assembly-1_Q320.jpg)
![Fig. 3 Humphrey and Brayton cycle comparison [10]](profile/Gregoire-Lenoble/publication/245392919/figure/fig3/AS:508026455298048@1498134353969/Humphrey-and-Brayton-cycle-comparison-10_Q320.jpg)
In an effort to answer the current needs for more performing and energy efficient gas turbine engines, unsteady pressure gain devices are currently under great focus. This article describes the performance analysis of a novel turbine engine utilizing an internal combustion wave rotor. The performance of this engine is compared to that of a conventi...
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... enable efficient energy exchanges between two flows of different energy levels. In the case of a gas- turbine engine, the compressor delivery air receives energy from the high-energy burnt gases before its own combustion, as illustrated in Fig. 1. Because this energy exchange process is achieved through compression-expansion wave patterns that require an intermittently closed volume, it is performed within channels arranged around the periphery of a rotating drum (see Fig. 2). For the engine's main flow to be kept quasi-steady despite this flow stopping within chan- nels, the ...
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... the combustor of a conventional gas turbine to a WR, as shown in Fig. 1, is equivalent to introducing a high-pressure (HP) shaft. This topping further compresses core air by 20-100 per cent [1,2] and thus enables a combustion pressure gain of 15-20 per cent, which contrasts with the typical 5 per cent pressure losses of a conventional combustor. Perfor- mance gains are therefore achieved through pressure ...
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... to the uncertainty over the novel engine tech- nology, different scenarios have been run for each engine: an improved one, a nominal one, and an impaired one. The impact of the engine BPR on the (engine + nacelle) weight and dimensions has thus been modelled with three different weight factors: a reduced one ('kw = 0.5'), a nominal one ('kw = 1') and an increased one ('kw = 1.5'), respectively, producing figures (Figs 8 to 10). Figure 8 evidences considerable BPR influence on engine and nacelle weights, causing their sum to increase by 63 per cent, 72 per cent, or 76 The interested reader is referred to reference [21] for more details on these models. ...
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... weights, causing their sum to increase by 63 per cent, 72 per cent, or 76 The interested reader is referred to reference [21] for more details on these models. As the engine EIS is an important simulation unknown, its influence on the weight of engines of BPR = 6 and 7 (the first two values above the baseline engine BPR = 5.15) is plotted on Fig. 11. This influence is shown to be linear and negative: a later EIS means lighter and more efficient, compact technologies. On an average, an EIS shift from 1995 to 2050 saves 11 per cent of the total weight, which is relatively impor- tant when compared to the 38 per cent weight change obtained from a technology level scenario to ...
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... tailored as shown in Table 9 and powered by engines listed in Table 6 were run over the mis- sion illustrated on Fig. 12, carrying a typical payload of 23.5 tons over 10 000 km. This range is lower than the one that such aircrafts are typically designed for (12 000 km) but was chosen so as to accommodate take-off with the fuel required for each BPR-modified (heavier) engine without exceeding the maximum take-off weight ...
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... range and to avoid a take-off weight higher than 230 tons, hence the range choice made in section 5.2.2. Besides, climb and descent T40 temperatures have been adapted to each engine configuration, so as to keep the climb and descent times within a 20-25 min range for passenger safety considerations. The mission (fuel burn VS BPR) curve plotted in Fig. 13 illustrates the compromise between the low SFC enabled by BPR optimization (see Fig. 7) and consequent increase in drag and weight suggested by Figs 8 to 10. From Fig. 13, the optimum BPR for the evaluated novel cycle engine lies between 6 and 7, depending on the technology level scenario chosen for the engine. These BPR values are ...
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... engine configuration, so as to keep the climb and descent times within a 20-25 min range for passenger safety considerations. The mission (fuel burn VS BPR) curve plotted in Fig. 13 illustrates the compromise between the low SFC enabled by BPR optimization (see Fig. 7) and consequent increase in drag and weight suggested by Figs 8 to 10. From Fig. 13, the optimum BPR for the evaluated novel cycle engine lies between 6 and 7, depending on the technology level scenario chosen for the engine. These BPR values are interesting to compare with Fig. 7, which would have recommended a very high BPR (15 or even higher) for minimum engine SFC. It is also interesting to note that such BPR ...
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... the optimum BPR for the evaluated novel cycle engine lies between 6 and 7, depending on the technology level scenario chosen for the engine. These BPR values are interesting to compare with Fig. 7, which would have recommended a very high BPR (15 or even higher) for minimum engine SFC. It is also interesting to note that such BPR optimum values Fig. 13 Engine BPR influence on the mission fuel burn are very close to the one of conventional large turbo- fan engines based on similar cycle parameters. This clearly shows that the combustion technology is not a critical factor when determining the optimum BPR of a gas turbine ...
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... illustrated with Fig. 13, the optimum novel cycle engine BPR depends on the technology level scenario, which should be chosen with regard to the following ...
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... compressor, which should increase both weight and drag. This would argue in favour of a total weight higher than the nominal one. 2. The nominal (engine + nacelle) weight given by the WeiDim model includes an increase in technology level through a late engine EIS (2050), which reduces engine and nacelle weights by 11 per cent as shown in Fig. ...
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... mission simulations run with the base- line engine demonstrate a mission fuel requirement of approximately 66 tons. Considering the very sub- stantial fuel savings thus provided by the novel cycle engine (as illustrated in Fig. 13) and the conservative arguments given above, the impaired technology is the most appropriate scenario for this novel engine mod- elling. The optimum BPR for the novel cycle engine is therefore 6, thus requiring about 40 tons of fuel for the aircraft to complete its mission, which provides a very significant 40 per cent reduction in ...
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Citations
... Currently, wave rotor technology has been successfully applied in the gas turbine top cycle, [9][10][11] gas expansion refrigeration cycle, [12][13][14] and some other elds. [15][16][17] As an important component of wave rotor technology, GWEs have been investigated by several scientic research institutions, as shown in Fig. 2. 12,17,23 Power Jets Co., Ltd 18 rst proposed the concept of a GWE, and then Spalding 19 performed preliminary related theoretical research. Kenteld et al. 20 of Imperial College London accomplished the rst test of this technology in conjunction with a gas-wave divider, 21 proving that these two three-port wave rotor devices can achieve equivalent efficiency to turbomachinery when the pressures at each port are close enough. ...
Gas wave ejectors (GWEs) utilize pressure waves to efficiently transfer energy between gases, and they have broad applications in the chemical industry. In order to improve the performance of GWEs, the influence of bending angles on GWE performance was studied and experiments involving a GWE equipped with curved channels were carried out for the first time in this study. The research results show that when the exhaust angle difference (φ dout) is ≤-3.9° and the incident angle difference (φ din) is >5.0° or ≤-5.0°, the equipment performance decreases with an increase in the absolute values of the angle differences. The maximum efficiency of the backward-curved-channel device is 61.6% within the experimental range. The experimental efficiency of the curved-channel device and the static-pressure proportion of the total pressure of the medium-pressure gas are enhanced in comparison with a traditional straight-channel device, and the operating power consumption is relatively reduced. Due to the difference between the gas incident and exhaust angles, the manner in which the performance of the curved-channel device varies with the rotation speed is different depending on the working conditions.
... The application range for wave rotors outlined by the literature is diverse. The bulk of early studies focused on pressure exchangers with straight passage profiles for gas turbine topping cycles [1][2][3][4][5][6][7][8] and supercharging devices for internal combustion engines [9][10][11][12][13][14][15][16]. In recent years, the application to refrigeration cycles [17][18][19] and pressure-gain combustors [20][21][22] has come into the focus of consideration. ...
A wave rotor is a shock-driven pressure exchange device that offers potential efficiency gains in a variety of applications including refrigeration and gas turbine topping cycles. This paper introduces a quasi one-dimensional model for the computation of the unsteady flow field and performance characteristics of wave rotors of straight or cambered channel profiles. The purpose here is to introduce and validate a rapid but reliable method of modelling the performance of a power-generating wave rotor where little such insight exists in open literature. The model numerically solves the laminar one-dimensional Navier-Stokes equations using a two-step Richtmyer TVD scheme with minmod flux limiter. Source terms account for viscous losses, flow leakage between rotor and stator endplates as well as torque generation through momentum change. Model validation was conducted in two steps. First of all, unsteady and steady predictive capabilities were tested on three port pressure divider rotors from open literature. The results show that both steady port flow conditions as well as the wave action within the rotor can be predicted with good agreement. Further validation was done on an in-house developed and experimentally tested four-port, three-cycle, throughflow micro wave rotor turbine featuring symmetrically cambered passage walls aimed at delivering approximately 500 W of shaft power. The numerical results depict trends for pressure ratio, shaft power and outlet temperature reasonably well. However, the results also highlight the need to accurately measure leakage gaps when the machine is running in thermal equilibrium.
... The application range for wave rotors outlined by literature is diverse. The bulk of early studies focused on pressure exchangers with straight passage profiles for gas turbine topping cycles [1][2][3][4][5][6][7][8] and supercharging devices for internal combustion engines [9][10][11][12][13][14][15][16]. In recent years the application to refrigeration cycles [17][18][19] and pressure-gain combustors [20][21][22] has come into the focus of consideration. ...
A wave rotor is a shock-driven pressure exchange device that, whilst relatively rarely studied or indeed, employed, offers significant potential efficiency gains in a variety of applications including refrigeration and gas turbine topping cycles. This paper introduces a quasi one-dimensional wave action model implemented in MATLAB for the computation of the unsteady flow field and performance characteristics of wave rotors of straight or cambered channel profiles. The purpose here is to introduce and validate a rapid but reliable method of modelling the performance of a power-generating wave rotor where little such insight exists in open literature. The model numerically solves the laminar one-dimensional Navier-Stokes equations using a two-step Richtmyer TVD scheme with minmod flux limiter. Additional source terms account for viscous losses, wall heat transfer, flow leakage between rotor and stator endplates as well as torque generation through momentum change.
Model validation was conducted in two steps. First of all, unsteady and steady predictive capabilities were tested on three-port pressure divider rotors from open literature. The results show that both steady port flow conditions as well as the wave action within the rotor can be predicted with good agreement. Further validation was done on an in-house developed and experimentally tested four-port, three-cycle, throughflow micro wave rotor turbine featuring symmetrically cambered passage walls aimed at delivering approximately 500 W of shaft power. The numerical results depict trends for pressure ratio, shaft power and outlet temperature reasonably well. However, the results also highlight the need to accurately measure leakage gaps when the machine is running in thermal equilibrium.
... Over the past decades numerous research studies from a variety of research institutes have been dedicated towards the investigation of dynamic pressure exchange machinery, such as wave rotors. Early research efforts aimed at introducing pressure exchangers of straight channel profiles as a means to enhance gas turbine cycles [3,4,12] and internal combustion engines [6,7,13,14]. More recent studies further pursue gas turbine [15][16][17][18] and reciprocating engine [14,19,[19][20][21][22] enhancement. ...
This paper details an extensive experimental investigation of a novel throughflow micro-wave rotor with symmetrically cambered passage profiles designed for shaft power output as well as pressure exchange. This is the first time comprehensive experimental data from a power generating wave rotor is presented in a peer-reviewed journal. Moreover, the significance and renewed interest in wave rotors for a wide range of applications from refrigeration to micro-gas turbines makes this experimental programme extremely valuable to many fields of research. The wave rotor is a four port, three-cycle unit of 60 mm in diameter, 30 mm in length and houses 46 channels. The unit was experimentally tested on a gas stand in open-loop configuration using electrical heaters as a source of heat for the high pressure inlet and pressurised air for both inlet ducts. Throughout testing, the mass flow rates among high pressure in- and outlet were balanced. A series of tests were conducted investigating the effect of variation in rotational speed, ratio of inlet mass flow rates (loop flow ratio), axial clearances and peak inlet temperature on wave rotor performance. The results show the importance of minimum axial clearance for maximum energy transfer as well as for reduced mixing of hot and cold flows. The competing relationship between pressure ratio, high pressure zone pressure difference, internal exhaust gas recirculation and fresh air exhaustion is also highlighted. Finally, measurements of the temperature distributions in the high pressure outflow show the effect of rotational speed, loop flow ratio and centrifugal forces on the fresh air stream location and its mixing with the hot gas stream. A peak shaft power of 450 W and a peak pressure ratio of approximately 1.63 were obtained close to the design speed that were in line with expectations for clearances and temperatures under investigation. Using a new approach to calculating efficiency that assumes equal values for expansion and compression, a peak figure of 80% was obtained indicating the superiority that such designs have over similarly sized traditional turbomachinery.
... Welch and Paxson [2] pointed out that for small (300-500 kW) and midsize (2000-3000 kW) turboshaft engines the specific power could be raised by 19-21% and the specific fuel consumption rate could be reduced by 16-17% when integrated with a wave rotor; for the largescale turbofan engine (355-450 kN), the specific fuel consumption rate and the turbine inlet temperature could be reduced by 6-7% and 72 K, respectively, keeping the engine thrust unchanged. Furthermore, when the combustion process is transferred from the traditional gas turbine combustor with total pressure loss to the wave rotor channels with the deflagration or detonation combustion mode, which forms the internal combustion wave rotor, the total pressure at the combustor exit could be raised even higher keeping the turbine inlet temperature unchanged and the complexity of the ducting system and the engine weight could be reduced substantially [3,4]. ...
Leakage flow between the rotor and the stator can cause serious performance degradation of wave rotors which utilize nonsteady shock waves to directly transfer energy from burned gases to precompressed air. To solve this problem, primary flow features relevant to leakage are extracted and it was found that the leakage-attributed performance degradation could be abstracted to a special initial-boundary value problem of one-dimensional Euler equations. Then, a general loss assessment method is proposed to solve the problem of nonsteady flow loss prediction. Using the above method, a reasonable physical hypothesis of the initial-boundary value problem depicting the nonsteady leakage flow process is proposed and further, a closed-form leakage loss analytical model combined with an empirical correction method for the discharge coefficient is established. Finally, with the experimentally verified CFD method, comprehensive numerical verification is conducted for the loss prediction model; it is proved that the physical hypothesis of the proposed model in this paper is reasonable and the model is capable of predicting nonsteady shock wave attenuation due to leakage exactly within the range of parameter variations of wave rotors.
... One promising approach to reach efficiency improvements by 10% is to replace the isobaric combustion process by an isochoric one. Benefits of up to 40% fuel savings for a large turbofan engine are stated in [7] and [14]. In [4] an overview about opportunities to improve the thermodynamic cycle of gas turbines is given. ...
The provision of secure compressor operation under circumstances of a pulsed detonation engine is crucial for the success of pressure gaining combustion processes for turbo machinery applications. This paper discusses Active Flow Control as a possible solution to approach this challenge. The presented experiments were conducted on a highly loaded low speed linear compressor stator cascade. A choking-device which was located in the wake of the cascade simulated the non-steady out flow condition that is expected under the conditions of pressure gaining combustion. The flow structures of the non-steady
flow field were strongly correlated to the working-phase of the choking-device. In this paper an Iterative learning Controller (ILC) was used to find an optimized actuation trajectory that was used for closed-loop sidewall-actuation to control the corner separation in the non-steady flow field. The ILC took advantage of the periodicity of the disturbance to calculate a non-steady actuation trajectory that optimally suppressed the impact of the choking-device on the flow. The Active Flow Control Effect was evaluated by means of static pressure rise using five hole probe measurements in the wake of one passage.
... An aerothermodynamic analysis of gas turbine engines with implemented constant volume combustion is given in [15], where 30% fuel savings are stated for a 60 kW microturbine. Potentials of saving up to 40% fuel burn for a 300-passenger long-range mission, compared to a baseline engine modeled on a Rolls Royce Trent772, are stated in [5]. In [3], an overview about opportunities to improve the thermodynamic cycle of gas turbines is given. ...
... where xðkÀn p þ1Þ is calculated from (5). The matrices G 2 R n h Ân h and F 2 R n h Ân x read as follows ...
... using the state space model (5). The optimallðkþn p jkÞ is obtained from minimizing (21). ...
The provision of secure compressor operation under circumstances of a pulsed detonation engine is crucial for the success of pressure gaining combustion processes for turbo machinery applications. This paper discusses active flow control as a possible solution to approach this challenge. The presented experiments were conducted on a highly loaded low speed linear compressor stator cascade operated at \(Re=600{,}000\) and \(Ma =0.07\). A choking-device which was located in the wake of the cascade simulated the non-steady outflow condition that is expected under the conditions of pressure gaining combustion. In the discussed experiments, the choking-device generated a periodic disturbance to every passage at a typical Strouhal number of \(Sr =0.03\). The flow structures of the non-steady flow field were strongly correlated to the working-phase of the choking-device. In this paper, an iterative learning controller was used to find an optimized actuation trajectory that was used for closed-loop sidewall-actuation to control the corner separation in the non-steady flow field. The iterative learning controller took advantage of the periodicity of the disturbance to calculate a non-steady actuation trajectory that optimally suppressed the impact of the choking-device on the flow. The active flow control effect was evaluated by means of static pressure rise using five hole probe measurements in the wake of one passage.
There is widespread interest in using pressure gain combustion in gas turbine engines to increase gas turbine engine efficiency and reduce fuel consumption. However, the fluctuating turbine inlet conditions inherent with pressure gain combustion cause a decrease in turbine efficiency. Designing a turbine for pulsing flow would counteract these losses. An optimization of turbine geometry for pulsing flow was conducted with entropy generation as the objective function. A surrogate model was used for the optimizations based on data extracted from 2D computational fluid dynamics simulations. Optimizations run for different pulsing amplitudes informed a revised turbine design. The new turbine geometry was validated with a periodic, time-accurate simulation and a decrease in entropy generation of 35% was demonstrated. The design recommendations were to weight the design of the turbine toward the peak of the pressure pulse, to consider the range of inlet angles and decrease the camber near the leading edge, and to reduce the blade turning.
Pressure gain combustion shows potential to increase the cycle efficiency of conventional gas turbine engines if used in place of the steady combustor. However, a turbine driven by pulsing flow experiences a decrease in efficiency. An experimental rig was built to compare a steady flow driven turbine with a pulsing flow driven turbine. The pressure pulse was a full annular, sinusoidal pressure pulse. The experimental data showed a decrease in turbine efficiency and pressure ratio. The pressure pulse amplitude and not the frequency was discovered to be the cause for the decrease in turbine efficiency for the current experimental setup. The decrease in turbine efficiency was mapped with turbine pressure ratio and corrected amplitude to demonstrate how the efficiency of a turbine under pulsing flow conditions could be mapped.
