Variable Cycle Engine Research Articles

The Installation Performance Control of Three Ducts Separate Exhaust Variable Cycle Engine

The research on modeling and installation performance control of three ducts separate exhaust variable cycle engine has been studied. In this paper, we established the fan, the low pressure and high pressure compressor model based on the stage-stacking method. On this basis, a component-level mathematical model is constructed and the compressor model of adjustable mode selector valve area, the third bypass and its exhaust nozzle mode are established. Besides, the research took the inlet inside and outside characteristic model into consideration. The simulation showed that the engine could be able to modulate the third bypass airflow adaptively by control of fan vane, mode selector valve area, third bypass, and main exhaust nozzle area. It is possible to continuously match the engine’s airflow demand to the inlet’s airflow supply. The results show that compared with the mixed exhaust three ducts variable cycle engine, the inlet spillage drag of the separate exhaust variable cycle engine is reduced by about 18%. Under the condition of supersonic flight, the constant flow control can significantly improve the economy of the engine. Compared with the mixed flow variable cycle engine, the inlet spillage drag of the three ducts separate exhaust variable cycle engine is reduced by about 20%.

Research on Influence of Geometric Adjustment on Performance of Variable Cycle Engine

Based on conventional turbofan engine, this paper adding mode selection valve, the front variable area bypass injectors and the rear variable area bypass injectors to build a mathematical model of the variable cycle engine. Then the influence of adjustable components on engine performance is simulated by computation program. The simulation results show that in the same work mode, the front variable area bypass injectors and the rear variable area bypass injectors have the same effect on engine performance, but different from the mode selection valve; Both front variable area bypass injectors and rear variable area bypass injectors have different effects on engine performance in different modes.

Research on Variable Cycle Engine Control Based on Model Reference Adaptive Sliding Mode Control Method

As to solve the problem of multivariable output tracking control of variable cycle engine under system uncertainties and external disturbances, an augmented model reference adaptive sliding mode control method based on LQR method was developed. Firstly, the model is augmented and the reference state is provided to the controller by designing the reference model using the optimal LQR method. Then, based on the state tracking sliding mode control method, the adaptive law is derived based on the strict stability condition of Lyapunov function to estimate the upper bound of the system perturbation matrix and the upper bound of the external disturbances. Finally, the controller achieves the asymptotic zero tracking error of the system under the conditions of uncertainty and external disturbance. The simulation results showed that the LQR-based augmented model reference adaptive sliding mode control method can solve the problem that the traditional sliding mode control method needs to specify the reference state in advance and improve the control performance of the variable cycle engine control with system uncertainties and external disturbance. The tracking of the control command is effectively achieved and the steady-state and dynamic performance are improved. The steady-state control errors under different conditions are less than 0.1%, the system overshoot is less than 0.5%, and the adjustment time is less than 1s, which conformed to the requirements of the aero engine control system technology.

Mission Analysis and Operational Optimization of Adaptive Cycle Microturbofan Engine in Surveillance and Firefighting Scenarios

The current work focuses on mission-based evaluation of a novel engine architecture arising from the conversion of a microturbojet to a microturbofan via introduction of a variable speed fan and bypass nozzle. The solution significantly improves maximum thrust by 260%, reduces fuel consumption by as much as 60% through maintaining the core independently running at its optimum, and enables a wider operational range, all the meanwhile preserving a simple single spool configuration. Particularly, the introduction of a variable-speed fan enables real-time optimization for both high-speed cruise and low-speed loitering. In order to characterize the performance of the adaptive cycle engine with increased number of controls (engine speed, gear ratio, bypass opening), a component map-based thermodynamic study is used to contrast it against other similar propulsion systems with incrementally reduced input variables. In the following, a shortest path-based optimization is conducted over the locally minimum fuel consumption operating points, based on a set of gradient driven connectivity constraints for changes in gear ratio and bypass nozzle area. The resultant state transition graphs provide global optimum for fuel consumption at a thrust range in a given altitude and Mach flight envelope. Then, the engine model is coupled to a flight mechanics solver supplied with a conceptual design for a representative multipurpose unmanned aerial vehicle (UAV). Finally, the associated mission benefits are demonstrated in surveillance and firefighting scenarios.

Interval analysis of the standard of adaptive cycle engine component performance deviation

The deviation of engine component performance has great impact on the Adaptive Cycle Engine (ACE) overall performance and task adaptability. To make ACE performance reach the mission requirement, proper standard of component performance deviation (CPD) should be given in advance. In this paper, an approach based on the first order Taylor series expansion has been proposed and applied to set the standard of CPD without large amounts of calculation. This approach is an inversion process of the normal interval analysis and can take the distinction between the impacts of CPD indexes into consideration. Fifteen component performance parameters and four important operating conditions are investigated. The results show that the distinction between the impacts of CPD indexes and different operating conditions is obvious. Compared with setting uniform standard for all CPD indexes, this method can better utilize component characteristics and make the standard reasonable and economical. The standard of CPD can be derived within 10 times of off-design point calculation through this method, which is much less than 32768 times of calculation for the vertex method. This method is universal and can be applied to setting standard for the CPD of other type of gas turbine engines.

Performance Analysis of a Three-Stream Adaptive Cycle Engine during Throttling

One advantage of the adaptive cycle engine (ACE) is its ability of throttling with constant airflow by the combined control of variable geometries, resulting in an improvement of spillage drag. However, the improvement is achieved at risk of a complex technical solution and control. This article investigates the selection scheme of variable geometries and engine configuration. It focuses on the performance of a three-stream ACE during throttling, whose configuration and control schedule are simpler than other types of ACEs. Five variable geometries are selected from seven available options through comparison analysis. The uninstalled thrust decreases from 100% to 60.36% during the subsonic throttling and to 59.81% during the supersonic throttling. Benefitting from the decreased spillage drag, the installed performance of the three-stream ACE is improved to some degree during throttling. This improvement is less than the result of a three-bypass ACE, whose configuration and control schedule are more complex. Thus, the three-stream ACE is a compromise design considering the technical risk and variable cycle characteristic, which is a better platform to verify the component technology and control schedule for the further research on a more complex type of ACE.

Modeling method of variable cycle engine based on QPSO hybrid algorithm

Modeling method of variable cycle engine based on QPSO hybrid algorithm

Equilibrium running principle analysis on an adaptive cycle engine

As an evolutional concept of variable cycle engine, the adaptive cycle engine draws widely attention with high expectations. It combines a variable geometry schedule and component matching principles to demonstrate its advantages such as avoiding severe inlet spillage drag and the wide variable cycle characteristics. Thus, this paper aims at equilibrium running principle analysis on an adaptive cycle engine at variable operating modes, deriving the equilibrium running equations of an adaptive cycle engine for the first time, and exploring the physical essence of components matching principle on the basis of a newly developed nonlinear component-based adaptive cycle engine performance model. It uncovers the physical essence of components matching relationships and provides mathematical derivation of equilibrium running principles which lay theoretical foundation of the variable geometries modulation schedule and overall performance optimization on an adaptive cycle engine.

A Study on Combined Variable Geometries Regulation of Adaptive Cycle Engine during Throttling

The most remarkable variable cycle characteristic of the variable cycle engine (VCE) is that it keeps airflow almost constant during subsonic cruise throttling by modulating variable geometries, which can efficiently decrease spillage drag and increase installed thrust. One of the most critical challenges for the modulation lies in completely maintaining airflow, as well as avoiding specific fuel consumption (SFC) degradation during throttling. This has resulted in a need to investigate the modulation regulation of the adaptive cycle engine (ACE) which is a new concept for VCE and has greater potential for flexibly modulating airflow and pressure ratio. Thus, the aim of this paper is to study the variable geometries’ modulation schedule of ACE in maintaining airflow during throttling. A configuration of an ACE concept and its modeling study are first put forward. Then, the control schedule is researched via the combination of sensibility analysis and basic working principle instead of optimizing them directly. Results show that when the net thrust decreases from 100% to about 55% during subsonic cruise and to 32% during the supersonic cruise, the demand airflow of the engine is kept almost constant, which greatly improves the installed performance during throttling.

Multidisciplinary Design Optimization on Conceptual Design of Aero-engine

AbstractIn order to obtain better integrated performance of aero-engine during the conceptual design stage, multiple disciplines such as aerodynamics, structure, weight, and aircraft mission are required. Unfortunately, the couplings between these disciplines make it difficult to model or solve by conventional method. MDO (Multidisciplinary Design Optimization) methodology which can well deal with couplings of disciplines is considered to solve this coupled problem. Approximation method, optimization method, coordination method, and modeling method for MDO framework are deeply analyzed. For obtaining the more efficient MDO framework, an improved CSSO (Concurrent Subspace Optimization) strategy which is based on DOE (Design Of Experiment) and RSM (Response Surface Model) methods is proposed in this paper; and an improved DE (Differential Evolution) algorithm is recommended to solve the system-level and discipline-level optimization problems in MDO framework. The improved CSSO strategy and DE algorithm are evaluated by utilizing the numerical test problem. The result shows that the efficiency of improved methods proposed by this paper is significantly increased. The coupled problem of VCE (Variable Cycle Engine) conceptual design is solved by utilizing improved CSSO strategy, and the design parameter given by improved CSSO strategy is better than the original one. The integrated performance of VCE is significantly improved.

Research on Genetic Algorithm-Based Solution Method for Variable Cycle Engine Model

Variable cycle engine is a complex system, which is usually mathematically modeled as a series of multi-dimensional nonlinear implicit equations. Processes for solution of these equations are often complicated; therefore, a genetic algorithm-based method was presented in this paper for the solution of the mathematical model. The method was also evaluated by such parameters as initial value sensitivity, computation efficiency, convergence and stability; and compared with Newton-Raphson method. It shows that genetic algorithm-based method is less sensitive to initial values, more capable in convergent and computing stability than Newton-Raphson method, however more time consuming.

Optimization Design on Variable Cycle Engine Performance Based on Genetic Algorithm

The article have described the optimization of the engine performance problem as nonlinear multi-objective programming, and have analyzed the operation principle of the variable cycle engine, made models of maximum thrust , maximum unit thrust, minimum oil consumption, and then adopts the genetic algorithm to solve the model, gained the guide vane angle of CDFS,the guide vane angle of low-pressure.Turbine and the nozzle throat area when the performance is optimal . It is a problem about multi-objective optimization, obtained a series of satisfactory solution and then selected a set of approximate optimal solution as the final argument. Lastly, The matlab software is used to illustrate the effectiveness of the results.

Areo-Engine Cycle Parametric Analysis and Installed Performance Calculation Based on Aircraft Flight Mission

The aircraft/engine integration design numerical simulation model was established. The engine design performance specifications were obtained by calculating aircraft lift-drag characteristics, mission analysis, constraint analysis. Combining engine cycle parametric analysis with installation loss computing, the engine performance parameters can be found, which meet the aircraft flight envelope performance requirements. Taking double bypass variable cycle engine as an example to check the model, the results show that the variable cycle engine can meet aircrafts thrust and fuel consumption demands under different operating conditions, and achieve cruise thrust adjustment at the same inlet mass flow to reduce installation losses.

Powering Out of Trouble

This article presents a study of Pratt & Whitney’s J58, till date the best and high-powered engine for manufacturing lessons required for the development of F35 Joint Strike Fighter. The J58 Blackbird engine is a variable cycle engine, a turbojet/ramjet combined-cycle engine. It is a conventional afterburning turbojet for take-off and transonic flight, and it approximates a ramjet during high-speed supersonic cruise. The power plant for the Blackbirds is a marvelous development on the part of Pratt & Whitney, as it is the only engine of its kind in the world. The noise and vibration from a J58 test was so great that it could rattle the side-view mirror off nearby cars. The engine was developed at an isolated research center in Florida. At take-off and low-speed flight, the J58 engine/afterburner provides most of the thrust. Both of the Blackbird’s twin nacelles contain an engine supersonic inlet, the J58 engine with its afterburner, and an exhaust ejector nozzle. All three components contribute to the Blackbird’s propulsive thrust in varying proportions, depending on flight speed.

Shaft Power Extraction and Waste Heat Rejection using a Three Stream Variable Cycle Engine

Shaft Power Extraction and Waste Heat Rejection using a Three Stream Variable Cycle Engine

Distribution Device Optimization of Variable-cycle Engine Based on Comprehensive Performance Evaluation in All Speed

Aiming at the special type and parameters optimization problem of distribution device in two-stroke mode of variable-cycle engine(VCE),the simulation models for four-stroke mode and two-stroke mode of VCE are established based on one single-cylinder four-stroke engine,the accuracy of simulation models is verified with cylinder pressure experiments,the composite performance coefficient for quantizing comprehensive performance evaluation is proposed based on multiple engine performance indexes,and its validity is verified with examples calculation and the method of fuzzy matter element.According to the maximum principle of composite performance coefficient,a series of simulation analysis on three schemes of cylinder exhaust port of two-stroke mode are carried out,draw a conclusion that,while the bottom edge of four rounded rectangle exhaust port coincidence with the bottom dead center,the best comprehensive performance of two-stroke mode in all engine speed is getting when Intake valves open at the 46 degrees crank angle before bottom dead center(BBDC) and close at the 86 after bottom dead center(ABDC),cylinder exhaust port width is 30 mm and height is 14 mm.The results indicate that,the engine performance in all speed can be quantizing comprehensive evaluation and comparison in high efficiency by the composite performance coefficient.

Research of Aerodynamic Performance of HP-Turbine with Coolant Injections for Variable Cycle Engine

A highly loaded high-pressure turbine with a supersonic nozzle guide vane and a transonic rotor for a Variable Cycle Engine (VCE) has been investigated. Film cooling strategies were designed for the whole stage, during which the positions, injection orientations and arrangements of cooling holes were confirmed. Three-dimensional steady numerical simulations have been performed in the two operation modes of low and high bypass ratio with different thermodynamic cycle parameters according to the VCE and the coolant injections have been simulated by means of additional source term method. The influences of coolant injections in the fully cooled turbine stage on aerodynamic performance and flow characteristics have been analyzed. The results indicate that, the supersonic nozzle guide vane, over-expansion degree of main flows, fluctuations of static pressure and intensity of corner vortex are lessened or alleviated. In the transonic rotor, expansion and doing work capabilities in the mixed fluid are strengthened. Proper coolants injections are beneficial to the flow characteristics in the blade passage.

Analysis of Adaptive Cycle Engine Noise for Civil Aviation

To improve fuel economy and reduce operating costs are one of the future developments of the air transport. From another part, it is continually called for higher speed to satisfy the global reach and make the world as a neighbor. An airworthiness problem of supersonic civil aircraft is the propulsion system noise. The ACE (adaptive cycle engine) noise is explored at the state of takeoff based on the description and analysis of aero engine noise and supersonic air transport. The conceptual scheme of ACE is shown and then the calculation method of each component is studied, including fan, combustor, turbine and nozzle. The total noise level (EPN dB) is calculated and the impact of components noise is analyzed. The research shows that the ACE noise is lower than the supersonic aircraft Concorde but higher than actual subsonic civil engine. The nozzle and fan should be paid an attention at the noise suppression and the airport location for supersonic aircraft could be a condition of market acceptation.

Sensitivity analysis based on high fidelity simulation: application to hypersonic variable-cycle engine intake design

A sensitivity analysis of a supersonic intake of a turbine-based combined cycle (TBCC) engine is presented. A multi-block Reynolds-averaged Navier-Stokes (RANS) solver was used to compute the flowfield. While RANS simulation provides more realistic performance estimate than a simplified cycle analysis, the intake design must also take into account in-flight uncertainties for robustness. In this study, we focus on the effect of geometric uncertainties on the intake performance, and propose a practical approach to simulation-based sensitivity analysis. The method begins by constructing a radial-basis function (RBF) network, trained via efficiently sampled simulations. Using the RBF network as the surrogate model, sensitivity analysis is performed using the analysis of variance (ANOVA) technique. This approach makes it possible to perform a generalised multi-input-multi-output sensitivity analysis based on high-fidelity simulation. The resulting sensitivity indices help identify dominant parameters as well as the interaction among multiple parameters, which can then be used for design refinement.

Performance of a single nutating disk engine in the 2 to 500 kW power range

A new type of internal combustion engine with distinct advantages over conventional piston-engines and gas turbines in small power ranges is presented. The engine has analogies with piston engine operation, but like gas turbines it has dedicated spaces and devices for compression, burning and expansion. The engine operates on a modified limited-pressure thermodynamic cycle. The core of the engine is a nutating non-rotating disk, with the center of its hub mounted in the middle of a Z-shaped shaft. The two ends of the shaft rotate, while the disk nutates. The motion of the disk circumference prescribes a portion of a sphere. In the single-disk configuration a portion of the surface area of the disk is used for intake and compression, a portion is used to seal against a center casing, and the remaining portion is used for expansion and exhaust. The compressed air is admitted to an external accumulator, and then into an external combustion chamber before it is admitted to the power side of the disk. The external combustion chamber enables the engine to operate on a variable compression ratio cycle. Variations in cycle temperature ratio and compression ratio during normal operation enable the engine to effectively become a variable-cycle engine, allowing significant flexibility for optimizing efficiency or power output. The thermal efficiency is similar to that of medium sized diesel engines. For the same engine volume and weight this engine produces approximately twice the power of a two-stroke engine and four times the power of a four-stroke engine. The computed sea-level engine performance at design and off-design conditions in the 2 to 500 kW power range is presented.