Thrust Estimation Research Articles

Thermodynamic analysis on specific thrust of the hydrocarbon fueled scramjet

The aim of this work is to provide an upper estimate of the theoretical maximum specific thrust of the hydrocarbon fueled scramjet. An idealized thermodynamic cycle analysis is carried out to evaluate the performance of scramjet engines at different flight conditions, inlet pressure ratio and fuel equivalence ratio. Contrary to known Brayton cycles for the gas-turbine and ramjet engine, the inherent total pressure loss with heating must be taken into account in the high speed flow of the scramjet. The results show that the specific thrust initially grows asymptotically with fuel equivalence ratio, then reaches a maximum, and finally reduces rapidly for a given flight Mach number. The optimum inlet pressure ratio and fuel equivalence ratio at which the value of the specific thrust attains a maximum are presented. Variations of maximum specific thrust with freestream Mach numbers and material temperature limit are analyzed respectively.

Cassini Thruster Calibration Algorithm Using Reaction Wheel Biasing Data

Thrust force estimates for the reaction control thrusters onboard the Cassini spacecraft are presented in this paper. Cassini consists of two thruster branches, each with eight thrusters. The eight thrusters in each branch control the three body-fixed axes of the spacecraft. It is important to track the thrust force estimates in order to detect any thruster degradation and for supporting various activities in spacecraft operations (Titan flyby, spacecraft maneuvers, etc.). The Euler equation, which describes the rotational motion of the spacecraft during a reaction wheel bias event (wheel momentum change), is used to develop the algorithm. The thrust estimates are obtained from the pseudoinverse solution using flight telemetry during the bias. These results are similar to thrust estimates from the Kalman filtering algorithm. Cassini operations used the first thruster branch from launch until November 2008. Results show that two thrusters in this branch exhibited degraded thrust in November 2008. Because of the degraded thrust performance, the first branch usage was discontinued, and the prime branch was swapped to the second thruster branch in March 2009. The thrust estimates from this branch do not show any degradation to date. The algorithm is used to trend the thruster branch thrust force estimates as the mission continues.

Predicting performance of EPB TBMs by using a stochastic model implemented into a deterministic model

The current study is an attempt to address the stochastic nature of the rock excavation process by suggesting a stochastic performance prediction model implemented into a deterministic model developed for hard rock TBMs. Full-scale linear cutting experiments using constant cross-section and V-type of disc cutters are performed on two different limestone samples to provide the basic input required for the deterministic model used for estimation of instantaneous penetration rate, daily advance rate, thrust and torque requirements of TBMs. Stochastic estimation is performed by using a Monte Carlo simulation program by applying iterations to implement the probabilistic distribution of each model parameter and provide knowledge of a confidence level. Results of the suggested model are verified by measuring the field performance of two earth pressure balance (EPB) TBMs excavating competent rocks in semi-closed mode. The results indicate that the suggested model works well for prediction of instantaneous cutting/penetration rate for both TBMs and both types of disc cutters. However, an improvement on the model is required for estimation of cutterhead torque and thrust of EPB TBMs. The stochastic model implemented into the deterministic model results in almost similar predictions with the deterministic model in 50% (best guess) probability. However, the stochastic modeling provides a tool for exploring the full implications of linear cutting experiments and allows assessing the probability of occurrence and predicting variations of the TBM performance parameters, covering the uncertainties/risks.

Analysis of Propeller Static Thrust Estimation Method

Propeller thrust estimation method is convenient in selection of propellers. In this paper the Abbott formula method, Hamilton method and strip theory are introduced and then compared with the test value of propeller static thrust. The result shows that the three methods are all correct on the tendency of static thrust varies with revolution. Considered on the entire factor the Hamilton method is recommended.

Prediction of Fundamental Properties of Ionic Liquid Electrospray Thrusters using Molecular Dynamics

Molecular dynamics (MD) simulations are performed to model an electrospray thruster for the ionic liquid (IL) EMIM-BF4 using two coarse-grained (CG) potentials. Different equilibrium properties were obtained for the two potentials and then both were used to study the electrical extrusion of the IL for different electric field strengths and mass flow rates. The MD simulations provide the first insight into the atomistic modeling of a capillary-tip-extractor system, the basic elements of an electrospray thruster. One of the CG potentials was found to predict the formation of the Taylor cone, the cone-jet, and other extrusion modes for similar electric fields and mass flow rates observed in experiments of a IL fed capillary-tip-extractor system. Current distributions and anion and cation behavior were characterized and estimates of thrust and specific impulse are presented and compare reasonably well with measurements. Moreover, the role of inhomogeneities in the electric field as well as that of the IL space-charge most likely will improve agreement between modeling and experiment.

Thrust Estimates of a Partially Filled Multi-Cycle Pulse Detonation Rocket Engine

Partially filled multi-cycle operation usually happens in pulse detonation rocket engines (PDREs). Thrust estimates of PDREs under such operating conditions will provide significant reference for relevant studies. An analytical model for thrust estimates is proposed in the present study. This model is based on Wintenberger' model for impulse calculation and empirical formula for specific impulse prediction of partially filled tubes; moreover, it takes into account performance penalty created by obstacles preliminarily, which are introduced to accelerate deflagration to detonation transition. Four specific analytical models are developed according to three previously proposed empirical formulas and a fitting one proposed for partial filling effect. Comparisons between model predictions and experimental measurements are carried out to validate the reliability of the models. It is found that the models make reasonable estimates and one of the models performs very well over a wide range of conditions. Discussion and analysis on the proposed model and partial filling effect are also performed in this study. Although there are many other factors that should be considered in evaluating thrust of partially filled multi-cycle PDREs, the present study supplies a rapid and effective means for thrust estimation and provides some modeling ideas meanwhile.

A Four-Quadrant Thrust Estimation Scheme Based on Chebyshev Fit and Experiment of Ship Model

This paper proposes a thrust estimation scheme for marine propellers in four-quadrant operations. To calculate the thrust and torque coefficients of screw propeller in four-quadrant, a Chebyshev fit expression of the propeller properties in four-quadrant for surface vessel is given, and then it is changed into an ordinary polynomial expression. These expressions are suitable for calculating the value of the propeller thrust and convenient for studying the ship's maneuverability. On the basis of ship-propeller movement characteristics, the dynamical models of propeller in four- quadrant operations are given. The effectiveness of the proposed thrust estimation scheme is validated by experimental results derived from an electrically driven fixed pitch propeller, which provides a good reference for the vessel operations.

EVENT SHAPES FOR HADRONIC FINAL STATE: EXPERIMENTAL REVIEW

The analysis is presented for the first moments of collective observable distributions in two-jet events for various interaction types and for wide initial energy range. These observables include sphericity, thrust, components of transverse particle momentum, alignment and planarity. Database of experimental results created in the framework of the paper includes data for all interactions. Energy dependencies of average values for collective observables except components of transverse momentum show universal behavior for various interactions. Particle transverse momentum as well as its components increase faster for e+e- interaction with growth of [Formula: see text], than that for other interactions. Empirical analytical functions are suggested for description of energy dependence for all collective observables under study with exception of infrared-stable thrust variable. Energy dependence for average thrust is compared with QCD predictions including perturbative part and analytical phenomenological corrections which account for nonperturbative effects. Dispersive model and single dressed gluon approximation are considered for description of energy dependence of first moment of thrust distribution and estimation of strong coupling constant for various interactions as well as for joint sample. The dispersive model allow to describe average thrust versus initial energy in wide range of [Formula: see text] down to strongly nonperturbative domain [Formula: see text] at qualitative level at least. Study of event shape observables allows to obtain estimations of αS(MZ) which are in reasonable agreement both with world average value and with results extracted in the framework of other methods. Using suggested analytical fitted functions some estimations of values of collective parameters under study have been obtained for present and future facilities. In TeV energy domain average values of collective observables either depend on [Formula: see text] weakly or do not depend on initial energy at all within errors. Thus, the TeV scale can be considered as an estimation of the low boundary of asymptotic region for traditional collective parameters. Usually, multiplicity dependence of collective observables under consideration agree with power function in energy domain [Formula: see text] at qualitative level at least. Behavior of sphericity versus multiplicity and comparison of experimental results with model calculations allow to suggest that the universal estimation of the low energy boundary for experimental appearance of event jet structure in multiparticle production processes is [Formula: see text].

A New Pulse Modulator for Solid Propellant Attitude Control Motors

Antimissile interceptors with the attitude control motors (ACM) were researched. For solid propellant ACM, a pulse frequency modulation scheme is proposed, which is based on conventional PWPF modulator. The modulator extends the application of modulation control method to solid propellant ACM, and integrates it with a feedback of thrust estimation which is decided by location and thrust interaction factors. The stability of the new modulator was analyzed by Lyapunov method and a stability margin was given. Simulations show that the stability margin is conservative, but acceptable. Interceptor simulations using the modulator indicate that this technique provides closer-to-linear actuation than conventional bang-bang thruster control methods.

Model-based on-board turbofan thrust estimation

In this article model-based thrust estimation for turbofan engines is discussed. Two different model-based thrust estimation filters are applied to a low bypass ratio turbofan engine. The two estimators are based on a simple gross thrust model and on a thermodynamic semi-transient model, respectively. The filter parameter estimation as well as the corresponding validation of parameters is based on the use of the “leave one out cross validation” technique. In this article it is demonstrated, in particular, that a thrust estimation filter based on the thermodynamic semi-transient engine model 1 1 Steady state model with measured dynamic states as input. shows good accuracy and predicts the transient thrust and static measurements very well.

G226 ラジアルタービンのスラストに関する研究(OS7 高温・高効率発電)

Radial turbines that have a permanent magnet generator rotor in a common shaft have been widely used for small turbines like a microturbine. Though one of the features for those turbo machineries is their capability to be configured with a simplified rotor configuration without gear boxes, thrust generated by the rotor system has to be canceled in the rotor system itself. A simple method is presented for thrust estimation which has been used in development of a 150kW class microturbine. This simple method for thrust estimation was applied to design a similar type of small radial inflow turbine. The turbine rotor was designed to satisfy both high turbine efficiency and low thrust. Experimental results of the prototype turbine load tests showed that the estimated thrust was within the design allowance range at the rated load.

Experimental evaluation of pumpjet propulsor for an axisymmetric body in wind tunnel

Design of a Pump Jet Propulsor (PJP) was undertaken for an underwater body with axisymmetric configuration using axial/low compressor design techniques supported by Computational Fluid Dynamics (CFD) analysis for performance prediction. Experimental evaluation of the PJP was earned out through experiments in a Wind Tunnel Facility (WTF) using momentum defect principle for propulsive performance prior to proceeding with extensive experimental evaluation in towing tank and cavitation tunnel. Experiments were particularly conducted with respect to Self Propulsion Point (SPP), residual torque and thrust characteristics over a range of vehicle advance ratio in order to ascertain whether sufficient thrust is developed at the design condition with least possible imbalance torque left out due to residual swirl in the slip stream. Pumpjet and body models were developed for the propulsion tests using Aluminum alloy forged material. Tests were conducted from 0 m/s to 30 m/s at four rotational speeds of the PJP. SPP was determined confirming the thrust development capability of PJP. Estimation of residual torque was carried out at SPP corresponding to speeds of 15, 20 and 25 m/s to examine the effectiveness of the stator. Estimation of thrust and residual torque was also carried out at wind speeds 0 and 6 m/s for PJP RPMs corresponding to self propulsion tests to study the propulsion characteristics during the launch of the vehicle m water where advance ratios are close to Zero. These results are essential to assess the thrust performance at very low advance ratios to accelerate the body and to control the body during initial stages. This technique has turned out to be very useful and economical method for quick assessment of overall performance of the propulsor and generation of exhaustive fluid dynamic data to validate CFD techniques employed.

Status report of the electric sail in 2009

The electric sail is a new propulsion concept which uses charged tethers to extract momentum from the solar wind by Coulomb interaction. We give a status report of the electric sail as of October 13, 2009. We report progress during the last two years in plasma physical thrust estimation, tether manufacture methods, navigability, test mission planning and applications. The thrust estimates have gone up recently by a factor of about five, samples of final-type tether have been manufactured, accurate navigability of the sail in variable solar wind has been shown numerically, a CubeSat test mission for measuring the electric sail force in orbit is in Phase-A study and trajectory calculations for many classes of missions have been made. Using existing technology, it seems possible to build an electric sail of ∼ 1 N thrust, ∼ 100 kg mass and ∼ 10 year lifetime. In terms of lifetime produced impulse per unit propulsion system mass, such a near-term and general-purpose device would be about 1000 times more efficient than a chemical rocket and about 100 times more efficient than a contemporary ion engine. This level of performance is enough to enable a host of important applications, such as in situ measurements in interstellar space, sample return from most solar system targets, non-Keplerian orbit probes for space weather forecasting and helioseismology and economical utilisation of asteroid resources.

Experimental evaluation of pumpjet propulsor for an axisymmetric body in wind tunnel

Design of a Pump Jet Propulsor (PJP) was undertaken for an underwater body with axisymmetric configuration using axial flow compressor design techniques supported by Computational Fluid Dynamics (CFD) analysis for performance prediction. Experimental evaluation of the PJP was carried out through experiments in a Wind Tunnel Facility (WTF) using momentum defect principle for propulsive performance prior to proceeding with extensive experimental evaluation in towing tank and cavitation tunnel. Experiments were particularly conducted with respect to Self Propulsion Point (SPP), residual torque and thrust characteristics over a range of vehicle advance ratio in order to ascertain whether sufficient thrust is developed at the design condition with least possible imbalance torque left out due to residual swirl in the slip stream. Pumpjet and body models were developed for the propulsion tests using Aluminum alloy forged material. Tests were conducted from 0 m/s to 30 m/s at four rotational speeds of the PJP. SPP was determined confirming the thrust development capability of PJP. Estimation of residual torque was carried out at SPP corresponding to speeds of 15, 20 and 25 m/s to examine the effectiveness of the stator. Estimation of thrust and residual torque was also carried out at wind speeds 0 and 6 m/s for PJP RPMs corresponding to self propulsion tests to study the propulsion characteristics during the launch of the vehicle in water where advance ratios are close to Zero. These results are essential to assess the thrust performance at very low advance ratios to accelerate the body and to control the body during initial stages. This technique has turned out to be very useful and economical method for quick assessment of overall performance of the propulsor and generation of exhaustive fluid dynamic data to validate CFD techniques employed.

S0502-4-4 急加速する板の後流([S0502-4]噴流,後流および剥離流れ現象の解明と制御(4))

We studied on a vortex ring generated by a suddenly accelerated disk to understand a relation between the circulation and necessary force to accelerate the disk. To estimate a propulsive force of small swimming animals is our motivation. We measured velocity fields using a PIV system and high speed CMOS camera around a circular disk as a model of a fin and paddle. We showed that the time derivative of the circulation related to the force to drive the disk. Thus, the disk gives energy impulsively to the vortex ring. This gives us the way to estimate thrust if we could measure the change in circulation of the starting vortex ring by the disk. We applied it to the estimation of thrust by an accelerated non-circular disk by introducing an equivalent circle that has the same area as the non-circular disk.

Simulation and experiment research on vaporizing liquid micro-thruster

In the present work, a micro-thruster chip with dimension of 19.5 mm × 9.5 mm was fabricated with MEMS technologies for the experiment study of vaporizing liquid micro-thruster. In addition, a full 3D computational model was constructed to simulate the aft section of a vaporizing liquid micro-thruster for investigating flow characteristics. The results show that there were four distinct flow patterns observed in this study including snake flow, vapor-droplet flow, vapor-droplet-jet flow, and vapor flow. To prevent the failure of micro-thruster chip from generating of snake flow, the heating treatment of an empty micro-thruster chip at 300 °C for 2 h was the key factor. The generation of vapor flow preliminarily proved that the concept of vaporizing liquid micro-thruster chip was feasible. Furthermore, the numerical model in this study successfully provided the thrust estimation. The channel cross-section of 1 mm × 100 μm designed in this study was fit for developing a micro-thruster of O(mN) (ranging from 1 to 6 mN approximately). The numerical simulation could match better with the experiment results for the vapor flow cases if the flow oscillation was taken into consideration, and the heating channel of micro-thruster was lengthened to completely vaporize the liquid water.

Estimation of Terrain Forces and Parameters for Rigid-Wheeled Vehicles

This paper provides a methodology for the estimation of resistance, thrust, and resistive torques on each wheel of a rigid-wheeled vehicle generated at the vehicle-terrain interface, and from these forces and moments, a methodology to estimate terrain parameters is presented. Terrain force estimation, which is independent of a terrain model, can infer the ability to accelerate, climb, or tow a load independent of the underlying terrain properties. When a terrain model is available, parameters of that model, such as soil cohesion, friction angle, maximum normal stress, and stress distribution parameters, are determined from estimated vehicle-terrain forces using a multiple-model estimation approach, providing parameters that relate to accepted mobility metrics. The methodology requires a standard proprioceptive sensor suite-accelerometers, rate gyros, wheel speeds, motor torques, and ground speed. Sinkage sensors are not required. Simulation results demonstrate efficacy of the method on three terrains spanning a range of soil cohesions reported in the literature.

A Four-Quadrant Thrust Estimation Scheme for Marine Propellers: Theory and Experiments

A thrust estimation scheme for marine propellers that can operate in the full four-quadrant range of the propeller shaft speed and the vessel speed has been developed. The scheme is formed by a nonlinear observer to estimate the propeller torque and the propeller shaft speed and by a mapping to compute the thrust from the observer estimates. The mapping includes the estimation of the propeller advance ratio. The advance speed is assumed to be unknown, and only measurements of shaft speed and motor torque have been used. The robustness of the scheme is demonstrated by Lyapunov theory. The proposed method is experimentally tested on an electrically driven fixed pitch propeller in open-water conditions, in waves and with a wake screen that scales the local flow down in order to simulate one of the effects of the interaction between the propeller and the vessel hull.

The hydrodynamics of ribbon-fin propulsion during impulsive motion

Weakly electric fish are extraordinarily maneuverable swimmers, able to swim as easily forward as backward and rapidly switch swim direction, among other maneuvers. The primary propulsor of gymnotid electric fish is an elongated ribbon-like anal fin. To understand the mechanical basis of their maneuverability, we examine the hydrodynamics of a non-translating ribbon fin in stationary water using computational fluid dynamics and digital particle image velocimetry (DPIV) of the flow fields around a robotic ribbon fin. Computed forces are compared with drag measurements from towing a cast of the fish and with thrust estimates for measured swim-direction reversals. We idealize the movement of the fin as a traveling sinusoidal wave, and derive scaling relationships for how thrust varies with the wavelength, frequency, amplitude of the traveling wave and fin height. We compare these scaling relationships with prior theoretical work. The primary mechanism of thrust production is the generation of a streamwise central jet and the associated attached vortex rings. Under certain traveling wave regimes, the ribbon fin also generates a heave force, which pushes the body up in the body-fixed frame. In one such regime, we show that as the number of waves along the fin decreases to approximately two-thirds, the heave force surpasses the surge force. This switch from undulatory parallel thrust to oscillatory normal thrust may be important in understanding how the orientation of median fins may vary with fin length and number of waves along them. Our results will be useful for understanding the neural basis of control in the weakly electric knifefish as well as for engineering bio-inspired vehicles with undulatory thrusters.

Jet-driven molecular outflows from class 0 sources: younger and stronger than they seem?

Context. The momentum, age and momentum injection rate (thrust) of molecular outflows are key parameters in theories of star formation. Systematic biases in these quantities as inferred from CO line observations are introduced through simplified calculations. These biases were quantified for radially expanding flows. However, recent studies suggest that the youngest outflows may be better described by jet-driven bowshocks, where additional biases are expected. Aims. We investigate quantitatively the biases in momentum, age, and thrust estimates in the case of young jet-driven molecular outflows, and propose more accurate methods of determining these quantities. Methods. We use long-duration (1500 yr) high resolution numerical simulations in concert with the standard observational methods of inferring the relevant quantities to quantify the systematic biases in these calculations introduced, in particular, by dissociation, erroneous inclusion of transverse momentum, and hidden material at cloud velocity. Jet/ambient density contrasts of 0.1–1 are considered, leading to bow speeds of 60–135 km s −1 . Results. When mass-weighted velocities are used, lifetimes are overestimated by typically an order of magnitude. The molecular thrust is then underestimated by similar amounts. Using the maximum velocity in CO profiles gives better results, if empirical corrections for inclination are applied. We propose a new method of calculating the lifetime of an outflow which dramatically improves estimates of age and molecular thrust independent of inclination. Our results are applicable to younger flows which have not broken out of their parent cloud. Conclusions. Published correlations between the molecular flow thrust and the source bolometric luminosity obtained with the maximum CO velocity method should remain valid. However, dissociation at the bow head may cause the observable thrust to underestimate the total flow thrust by a factor of up to 2–4, depending on the bow propagation speed and the magnetic field strength. Detailed evaluation of this effect would greatly help to better constrain the efficiency of the ejection mechanism in protostars.