Thrust Output Research Articles

Expanding Known Performance Capabilities of Geared Turbofan Engine When Powered by LNG and Methanol

As aviation demand rises, fossil jet fuel consumption follows, thus increasing focus on sustainable aviation fuels to reduce aircraft greenhouse gas emissions. While advanced technologies and optimized operations play a role, alternative fuels, especially non-drop-in options like Liquefied Natural Gas (LNG) and methanol, offer promising potential for significant emission reductions if used in current aero-engines. LNG, a candidate near-term replacement of fossil jet fuel and methanol, even though a less conventional option in aviation, present advantages. Both fuels showcase the ability to generate the same thrust output by also achieving lower post-combustion temperatures, thereby enhancing component life and reducing emissions. Inversely, requesting equal post-combustion temperature as the baseline kerosene operation of the engine can produce greater thrust output, a much needed result for such fuels with low volumetric energy density, which causes greater take-off thrust demand mainly due to their larger tank requirements. This study uses advanced 0-D engine models coupled with detailed chemistry 1-D burner models and mission analysis tools to assess the aforementioned trends of LNG and methanol used to power a current geared turbofan engine. The aim of this work is to provide insights into the advantages, the limitations and the overall viability of the fuels in question as less polluting aviation fuels, addressing both environmental impact and operational feasibility in future aviation applications. According to findings of this article, when compared with Jet-A, LNG can reduce post-combustion temperature by an average of 1% or increase net-thrust by 3% while lowering CO2, NOx and CO emissions by 20%, 46% and 39%, respectively. Adversely, methanol is capable of lessening post-combustion temperature by 3% or enhancing thrust output by 10% while also reducing CO2, NOx and CO emissions by an average of 6%, 60% and 38%, respectively.

A fins-shaped bidirectional linear ultrasonic motor driven by a single-phase signal

Abstract Inspired by the propulsion mechanism of fish swimming through tail-fin oscillations, we have developed and experimentally studied a high-performance miniature bending vibration linear ultrasonic motor driven by a single-phase standing wave. A symmetrical structural design achieves bidirectional motion with consistent output characteristics. Two lead zirconate titanate (PZT) piezoelectric patches are symmetrically distributed on a metal elastic body’s upper and lower sides. In the stator, a sinusoidal signal is applied only to the piezoelectric patch on one side, while the patch on the opposite side is either left open or short-circuited to the ground. This results in an asymmetry in the structural damping between the upper and lower sides of the stator. The first-order bending vibration of the stator generates displacement in an inclined direction at the end of the driving foot. The motor achieves forward and backward motion by applying the same voltage to the piezoelectric patches on different sides. The dimensions of the stator have been finalized, and a prototype of the designed motor has been fabricated. Subsequent experimental tests were conducted to evaluate the prototype’s performance, including its mechanical output characteristics. At a frequency of 138.3 kHz, the maximum speed of the motor without load is 134.58 mm s−1. Under a voltage of 200 Vp-p and a preload of 3 N, the motor’s maximum output thrust is approximately 0.3 N. The actual mass of the motor is approximately 1.2 g, resulting in a thrust-to-weight ratio of 25.

Analyzing Engine Performance and Combustor Performance to Assess Sustainable Aviation Fuel Blends

FT blends derived from biomass have been confirmed to benefit reductions in GHG and particulate matter (PM). An improvement in combustibility is predicted to reduce fuel consumption and lead to further emission reduction. Various FT fuel blends (7%, 10%, 23%, and 50%) were assessed in terms of their potential for energy savings and emission reduction in a ZF850 jet engine. The engine performance, including the thrust, fuel consumption, emissions, exhaust gas temperature (EGT), acceleration, and deceleration, was investigated in terms of the whole thrust output, while combustor performance parameters, including EIUHC, EIPM2.5, EICO, EINox, and combustion efficiency, were also discussed. The benefit gained in engine performance was nonlinearly related to the blend ratio, which indicated that the available FT blends required appropriate fuel properties coupled with the engine design. According to the superior improvements derived from the 7% FT fuel blend and 23% FT fuel blend, an appropriate lower C/H ratio and higher combustion efficiency with low PM emissions led to a reduction in fuel consumption. Through global sensitivity analysis, changes in the thrust-specific fuel consumption (TSFC) and the thrust and combustion efficiency with various fuel properties were captured. These can be classified as engine-influenced and fuel-influenced (EIFI) parameters. EICO and EINOx are mainly dependent on the combustor and engine design and can be categorized as engine-influenced and fuel-less-influenced parameters (EIFLI), while EIUHC and EIPM2.5 can be categorized as EIFI parameters. The results of this work could extend our understanding of the impact of FT blends on engine performance and GHG reduction.

In-situ blade strain measurements and fatigue analysis of a cross-flow turbine operating in a tidal flow

Cross-flow turbines (CFTs) are inherently unsteady devices with regards to operating principle and loading. By improving our understanding of the dynamic loading on these turbines, we hope to better inform CFT design, improve survivability, and reduce overall costs. The University of New Hampshire (UNH) and the National Renewable Energy Laboratory (NREL) collaborated on a project to instrument and test a four-bladed New Energy Corp. vertical axis cross-flow turbine in a real tidal flow. One blade from the 3.2 m diameter x 1.7 m height turbine was instrumented with eight full-bridge strain gauges along the span of the blade. The turbine was then deployed at the UNH-Atlantic Marine Energy Center (AMEC) Tidal Energy Test Site in Portsmouth, NH. Time-synchronized measurements of blade strain, inflow, thrust, rotational speed, and electrical output were obtained to characterize blade loading under various conditions. The blade strain was examined to assess the dynamic loading and conduct a fatigue analysis on the device.

Design and performance evaluation of a spiral bar precision weeding mechanism for corn fields

This paper focuses on addressing the limitations of existing mechanical weeding methods for corn plants by introducing a spiral tendon-type precision weeding device specifically designed for corn fields. The study encompasses mechanical design and theoretical analysis to determine the overall structure, component parts, application scenarios, operation modes, and working principles of the device. The force applied to the spiral tendon weeding cutter head, a crucial working component of the device, is analyzed, along with its motion characteristics. This analysis allows for the calculation of the force required for the spiral tendon to penetrate the soil, as well as the determination of its trajectory and speed in the soil. The desired motion pattern of the weeding cutter head is considered in determining the contour shape of the inner cylinder track and its cooperation mode with the roller follower. Furthermore, the design and optimization of the circulation groove track are conducted to derive the key parameters of the track. A prototype is then constructed based on the proposed structural design and parameter optimization scheme. Soil bin tests are performed to evaluate the device’s performance. The optimal combinations of working parameters are determined as follows: a 70-mm depth of the weeding cutter head into the soil, a movement speed of 80 mm/s, and an output thrust of the electric actuator of 180 N. Under these conditions, the device achieves a weed removal rate exceeding 95% with a 3% wounding rate, demonstrating stable operational performance.

Improving Base-Drag Corrections for Rotating Detonation Combustor Gross Thrust Measurements

One of the primary means of evaluating the total pressure ratio across a rotating detonation engine/combustor requires measuring its gross thrust output. The presence of flat aft-facing surfaces introduces base-drag forces; necessitating corrections to the measured thrust to determine the gross thrust. A finite number of static pressure measurements are taken on these surfaces, which are then numerically integrated to estimate the resulting base-drag force. This work systematically describes the methods of numerically integrating a limited number of pressure measurements at discrete locations. Sample base-drag measurements were performed on the truncated nozzle of a hydrogen/air operated rotating detonation combustor. The nozzle was instrumented with 17 pressure measurements distributed at three evenly spaced circumferential locations. An asymmetry in the pressure distribution is observed contrary to what is typically assumed in the literature. The relative impact of the edge pressure treatment is highlighted and is found to be a significant source of error in the numerical integration. The alternative means of numerical integration using a Gauss–Kronrod scheme is evaluated and compared to the standard Newton–Cotes method. Recommendations are provided to address the limitations and challenges of these types of base-drag measurements as they pertain to rotating detonation combustors.

Adaptive multimodal control of trans-media vehicle based on deep reinforcement learning

To solve the problem that the control system is prone to instability due to the sudden change of physical characteristics, strong interference, and nonlinear in the process of multimodal movement of trans-media vehicle, an adaptive control method combining the Deep Deterministic Policy Gradient (DDPG) and traditional Proportional-Integral-Derivative (PID) controller is proposed in this paper. In this approach, the upper-level DDPG controller continuously monitors the vehicle's state and environmental conditions, dynamically adjusting the PID parameters in real-time. The lower-level PID controller then utilizes these updated parameters to modulate the output thrust of the vehicle's motors, thereby achieving excellent control over the vehicle's entire movement. Firstly, according to the hydrodynamic analysis, the kinematics and dynamics mathematical model of the self-designed trans-media vehicle is constructed. This model includes the multi-stage motion modal process of aerial flight, underwater navigation, and cross-media motion, which is suitable for the simulation and verification of the control method. Then, an adaptive controller called RL-PID combining DDPG and PID is built, so that PID can adjust parameters in real-time according to the changes in the external environment. Finally, after theoretical stability proof, a comparison study is performed across three approaches, namely the novel RL-PID, Fuzzy PID, and PID. The experimental results illustrate the superiority of the proposed approach over the competing ones and the generalization of the proposed approach under different interference.

Energy and exergy analyses on the high-pressure bleeding-air variable cycle designed for a wide-speed-range airbreathing propulsion system

The performance of the traditional turbojet decreases sharply with the increase of the Mach number in the supersonic flight, especially for the turbine-based combined cycle (TBCC) engine in the transition region of the turbojet and scramjet engine. This paper proposes a new high-pressure bleeding-air variable cycle engine (HB-VCE) concept that aims to ease the sharp contradiction between thrust output and fuel consumption of TBCC in the transition region. Through the energy and exergy analyses, the HB-VCE shows greater potential in energy utilization under high Mach flight conditions. The performance of HB-VCE significantly improves as the bleed ratio increases, with a more pronounced effect at higher Mach numbers. At Mach 1.5, the HB-VCE increases the specific thrust (ST) by 2.84 % and reduces the specific fuel consumption (SFC) by 2.73 %. At Mach 2.4, it increases the ST by 6.60 % and reduces the SFC by 6.52 %. Additionally, the controlling law of the critical bleeding ratio constrained by the turbine outlet temperature is proposed. Finally, the effect of the turbine inlet temperature, overall pressure ratio, and Mach number on the critical bleeding ratio is analyzed. This paper provides a promising HB-VCE concept with greater energy utilization for the TBCC design in the transition region.

Development of a Plate Linear Ultrasonic Motor Using the Power Flow Method.

Linear ultrasonic motors can output large thrust stably in a narrow space. In this paper, a plate linear ultrasonic motor is studied. Firstly, the configuration and operating principle of the Π-type linear ultrasonic motor is illustrated. Then, two slotting schemes are put forward for the stator to enlarge the amplitude of the driving foot and improve the output performance of motor. After that, a novel optimization method based on the power flow method is suggested to describe the energy flow of stator, so as to estimate the slotting schemes. Finally, the prototypes are manufactured and tested. The experimental results show that the output performance of both new motors are excellent. The maximum output thrust of the arc slotted motor is 76 N/94 N, and the corresponding maximum no-load speed is 283 mm/s/213 mm/s, while the maximum output thrust of V-slotted motor reaches 90 N/120 N, and the maximum no-load speed reaches 223 mm/s/368 mm/s.

Hybrid rocket engine optimization by controlled oxidizer flow dynamics

Rocket engines are an essential component in delivering any payload such as satellites, rovers, and probes into space. One such kind of engine is the hybrid rocket engine. Classical hybrid rocket engines have first become popular in the early 1970s. These engines, while providing combined advantages of both solid rocket motors and liquid rocket engines, as well as being relatively cheap to manufacture when compared to liquid rocket engines, exhibit drawbacks in thrust throughout the burn of the engine caused by the oxidizer to fuel ratio shifts induced by fuel regression. Their loss in efficiency is what makes them undesirable in the construction of rockets and causes companies to use the more expensive liquid rocket engines which are higher in efficiency and overall thrust output. The negative side effects of the fuel regression can be reduced by eliminating the oxidizer to fuel ratio shifts during the operation of a hybrid rocket engine. In this paper, a new approach of controlled oxidizer flow is proposed to achieve a more favourable combustion. The differential equations of the fuel mass flow rate function are numerically solved in terms of oxidizer mass flow rate, the results of which are taken as a basis to define a control function. It was demonstrated that it is possible to eliminate the oxidizer-fuel ratio shifts for all fuel types.

Influence of humidity and air pressure on thrust characteristics of ion wind propulsion systems

Ion wind propulsion systems have potential applications in the field of unmanned aerial vehicle due to their compactness, quiet operation, and simple design. Previous studies have focused on the influences of power source, electrode arrangement, size, and shape on the output thrust characteristics. However, few studies have been performed on the environmental conditions, which can be beneficial for the practical applications of ion wind aircraft in various climatic conditions. In this work, a measurement platform of the output characteristics of ion wind propulsion system under various environmental conditions has been established. The experimental pressure range was 1–0.7 atm, and the relative humidity (RH) range was 30%–92%. The effects of air pressure and humidity, and voltage level on the thrust, thrust-to-power radio (TPR) corona current have been investigated. The results showed that the corona current and thrust of the wire-wing electrode array decreased with RH within the range of 30%– to 80%. Under higher humidity, the corona current and thrust tend to increase at most voltage levels. Moreover, the thrust and current both decreased with reduced pressure when keeping the voltage-to-pressure ratio (U/P) unchanged. It was also found that the thrust was roughly proportional to the square of the pressure. Finally, the possible explanations of the coupled influences on the output characteristics were discussed.

Design, optimization, and performance analysis of a subsonic high-through flow turbine

This paper presents the design method and numerical analysis results of a two-stage high-through flow (HTF) high-pressure turbine. Compared to conventional design principles, the HTF turbine proposed in this study is a kind of high flow coefficient turbine. This design scheme enables the turbine to effectively increase the output power and thrust while maintaining the same windward area. At the design speed, the pressure ratio of the HTF turbine is 3.8, with an adiabatic efficiency of 91.46%. The flow coefficients of the first and second stage are 0.76 and 0.86, respectively, and the loading coefficients are 2.55 and 1.47. Detailed design parameters, flow characteristics, and aerodynamic performance are presented in this paper. Based on the preliminary design result, the second stage turbine was optimized for a wide range of operating conditions. The computational fluid dynamics simulation results show that compared with the traditional turbine, the loading form of the HTF turbine changes from aft-loaded to front-loaded. In addition, there is a certain increase in tip leakage of the turbine. This study achieves high efficiency, while increasing the turbine flow rate, and provides a corresponding reference for the design method of improving turbine flow capacity.

Improved performance of linear induction motors based on optimal duty cycle finite-set model predictive thrust control

Linear induction machines (LIMs) find widespread adoption in various applications, owing to their inherent advantages such as low noise, compact turning radius, and excellent climbing capability. LIMs are extensively utilized in linear metro applications. However, in practical operations, the output thrust shrinks with the increase in speed, which is attributed to end effects. This phenomenon leads to a reduction in efficiency. In addition, fluctuations in the normal force impact system stability, posing disturbances to the suspension system. To address these challenges, this paper suggests a finite-set model predictive thrust control (FS-MPTC) for a drive system employing a linear induction motor (LIM). The FS-MPTC optimizes the duty cycle for the active voltage vector and allocates the remaining period to one of the zero voltage vectors. The selected zero voltage vector reduces the switching transition between it and the active voltage vectors. The duty cycle is calculated for the six voltage vectors by incorporating the deadbeat concept and the derivative value for the electromagnetic thrust. In the prediction stage of the FS-MPTC, the computed duty cycle and the corresponding voltage vector are used simultaneously and repeated for the six voltage vectors. The cost function comprises two terms: the error between the reference thrust and predicted thrust value as the first term and the error between the rated primary flux linkage and its predicted value as the second term. The reference thrust is generated from the outer speed control loop. To validate the effectiveness of the proposed control approach, Japanese 12000 linear induction machine parameters are employed for verification. Comparative analysis of the performance between the suggested control method with the optimal duty cycle and the same process with a fixed duty cycle demonstrates superior performance when utilizing the optimal duty cycle. Finally, the proposed FS-MPTC with the optimal duty cycle offers a promising solution to enhance the operational efficiency of the LIM-based drive systems.

Output fault-tolerant control of underwater vehicle based on adaptive sliding mode control under multiple constraints

In order to improve the stability of the underwater vehicle, the output fault-tolerant control method of the underwater vehicle based on adaptive sliding mode control is designed on the basis of setting multiple constraints. After the dynamic analysis of the underwater vehicle and its thruster, the output dimension constraint, input amplitude constraint, and state amplitude constraint were set. Based on these three constraints, the recursive cerebellar neural network is used to identify the time-varying and nonlinear unknown faults in the underwater vehicle online, and a deep convolution neural network is used to detect the known faults of the underwater vehicle. The error correction output code is then combined with a support vector machine to classify the detected faults. Finally, the output fault-tolerant control of an underwater vehicle is realized based on adaptive sliding mode control. The experiment shows that after the application of this method, because the recursive cerebellar neural network and the deep convolution neural network can estimate the size of the fault information in time, the sliding mode fault-tolerant controller can readjust the output of the controller according to the result of the fault identification to offset the effect of the fault on the robot, so that the robot can continue to maintain the original stable operation state. Even if the thruster has faults, this method can adjust the output of the thruster in time and reconstruct and recover the total control output, so that the actual output thrust is very close to the expected value, to achieve fault-tolerant control of the underwater vehicle output.

Nash-equilibrium strategies of orbital Target-Attacker-Defender game with a non-maneuvering target

This study investigates the orbital Target-Attacker-Defender (TAD) game problem in the context of space missions. In this game, the Attacker and the Defender compete for a Target that is unable to maneuver due to its original mission constraints. This paper establishes three TAD game models based on the thrust output capabilities: unconstrained thrust output, thrust constrained by an upper bound, and fixed thrust magnitude. These models are then solved using differential game theory to obtain Nash equilibrium solutions for the game problems, and the correctness and effectiveness of the solution methods are verified through simulations. Furthermore, an analysis of the winning mechanisms of the game is conducted, identifying key factors that influence the game’s outcomes, including weight coefficients in payoffs, the maximum thrust acceleration limit, and the initial game state. Considering the unique characteristics of space missions, a specific focus is given to the analysis of the Defender’s initial states in the hovering formation and in-plane circling formation, revealing overall success patterns for defense strategies from these two formations. In summary, this study provides valuable insights into the control strategies and winning mechanisms of orbital TAD games, deepening our understanding of these games and offering practical guidance to improve success rates in real-world scenarios.

Aerodynamic and Structural Assessment of Floating Wind Turbine Rotor Under Varying Tilt Angle

Predicting the aerodynamic performance of floating offshore wind turbines (FOWTs) proves challenging due to platform motion induced by waves. The effect of wind and waves results in a six-degree-of-freedom motion of the platform, directly influencing turbine performance. Understanding the impact of specific degrees of freedom (DOF) motions on aerodynamics and structural response is crucial for effective wind turbine design. This research examines the impact of rotor tilt on both aerodynamic performance and structural response. The investigation employs computational fluid dynamics (CFD) analysis and mapping aerodynamic loads onto the finite element (FE) mesh for structural analysis. The study employs a comprehensive 3D simulation, utilizing the moving reference frame (MRF) method for the NREL 5 MW reference wind turbine CFD simulations. It explores different rotor tilt angles (5°, 10°, 15°, and 20°) encountered by offshore structures during their operation and examines their impact on aerodynamic performance. Predicted aerodynamic loads were mapped onto the blade FE mesh using the radial basis function (RBF) interpolation technique and solved using the open-source FE solver CalculiX. The analysis shows that the turbine performance is relatively unaffected up to a tilt angle of 10°. However, further increase in rotor tilt angle adversely impacts turbine performance, leading to notable reductions in thrust and power output. The fluid-structure coupled analysis provided insights into the deformations and stresses experienced by the turbine blade, indicating a notable increase in flap-wise displacement for larger tilt angles, while edge-wise displacement is not as significantly affected. The maximum stress location on the blade generally correlates well with actual observations.

Performance evaluation of modified pintle-type fuel injector for LRE (liquid rocket engine)

This research focuses on the fluid dynamics analysis and empirical validation of a modified pintle-type fuel injector through computational modeling. The primary aim is to assess the injector's performance metrics, including spray dispersion and orientation, flow velocity, turbulence levels, and vortex formation, by adjusting the pintle's positioning, which inherently modulates the flow rate. The observed effects draw parallels with the interactions seen in conical spray and hollow cone swirl atomizers. A pintle-type fuel injector model was developed using geometric design software, and computational fluid dynamics simulations were conducted to ensure effective fuel and oxidizer blending. This study evaluates key performance indicators, such as thrust output and combustion efficiency, under specific operational pressures and velocities at the injector's orifice.

Simulation of Internal Flow Field in Pulse Thruster Unit

Pulse thrusters are widely used in the attitude control and flight trajectory control of rotating ammunition and vertical launching ammunition, which use own pulse impulse to change the attitude and trajectory of the missile. This paper simulates the internal flow field of a double-layer pulse thruster unit (PTU). The internal flow field of the PTU is simulated at various temperatures based on the three-dimensional compressible N-S governing equations and k-ω SST turbulence model. In addition, the influence of nozzle throat length and divergence half-angle on the performance of pulse T-thruster is analyzed. The simulation results demonstrate that the thrust output error of the PTU is minimum, when the nozzle throat length of the internal pulse thruster is 38 mm. Moreover, the stability of the PTU is improved.

An Energy Efficiency Optimization Method for Electric Propulsion Units during Electric Seaplanes’ Take-Off Phase

The electric seaplane, designed for take-off and landing directly on water, incorporates additional structures such as floats to meet operational requirements. Consequently, during the take-off taxiing phase, it encounters significantly higher aerodynamic and hydrodynamic resistance than other aircraft. This increases energy demand for the electric seaplane during the take-off phase. A mathematical model for energy consumption during this stage was developed by analyzing resistance, using the propeller pitch angle as an optimization variable. This study proposes a coupled energy efficiency optimization method for the take-off phase of an electric seaplane’s electric propulsion unit (EPU). The method aims to determine an optimal propeller pitch angle configuration aligned with the seaplane’s design criteria. This ensures that the propeller output thrust meets minimal requirements during take-off while enhancing energy efficiency. Experimental validation with the two-seater electric seaplane prototype RX1E-S has demonstrated that selecting the optimal propeller pitch angle can effectively reduce energy consumption by approximately 10.4%, thereby significantly enhancing flight efficiency.

A novel high energy density single-phase linear piezoelectric motor: design and experiment

The circuit simplification and simple structure of piezoelectric motor have become a major trend at present. Therefore, a novel, miniaturized, single-phase driven piezoelectric motor is proposed. The suggested piezoelectric motor employs a bending vibration mode of the first order, which is inspired by the motion patterns of fish tail fins. First, the motor’s operational principle and structure are explained. By analyzing the relationship between the working frequency and amplitude of the motor and the output power, the key parameters of the motor are determined, and the structure size of the motor is calculated. Next, the FEM model of the stator is utilized to conduct transient analysis in order to examine the movement path of the driving foot. Symmetrical right-diagonal or left-diagonal motions are formed by the driving foot during the first bending vibration, creating oblique elliptical movements. Finally, a prototype is made and its vibration and mechanical characteristics are tested. At a frequency of 15.6 kHz, the motor’s highest speed without any load is measured at 31.2 mm/s. Both forward and backward performance is identical. When the motor is supplied with a voltage of 140 Vpp and a preload of 2 N, it achieves a moving speed of 4.2 mm/s at 15.6 kHz, with an output thrust of around 0.9 N.