Characteristics Of Turbomachinery Research Articles

Insights into thermodynamic performance of a hypersonic precooled air-breathing engine with a complicated multi-branch closed cycle

An advanced precooled airbreathing engine with a closed Brayton cycle is a promising solution for high-speed propulsion, of which the Synergetic Air Breathing Rocket Engine (SABRE) is a representative configuration. The performance of the latest SABRE-4 cycle was analyzed in this paper. Firstly, a relatively complete engine performance model that considers the characteristics of turbomachinery and heat exchangers was developed. Then, Sobol’ global sensitivity analysis of key performance parameters was carried out to identify the most influential design variables. Optimal specific impulses under different target specific thrusts were obtained by particle swarm optimization, of which the thermodynamic parameters corresponding to a specific thrust of 1.12 kN·s·kg−1 and a specific impulse of 3163 s were chosen as the design values. Four different control laws were analyzed in contrast, and the charge control method had the strongest ability of thrust regulation as well as maintaining a favorable specific impulse performance. Finally, working characteristics under the charge control and over a typical flight envelope were calculated, in which the average value of the maximum specific impulse was as high as 5315 s. This study would help to deepen the understanding of SABRE-4 thermodynamic characteristics and other precooled airbreathing engine cycles with similar layouts.

Overspeeding characteristics of turbomachinery for gas generator cycle air turbo ramjet engine

The main interest in the current study focuses on the possibility of overspeeding for the gas-generator cycle air turbo ramjet (GG-ATR) engine. The authors developed the air turbo ramjet engine and investigated its compressor performance. Based on those data, the authors developed the analytical code for the air turbo ramjet engine, which calculates the performances of turbomachinery, gas-generator, and ram combustor. The previous study described that the rotor overspeeding would not occur in the air turbo rocket engine. However, the current results show that degraded ram combustion can decrease the compressor pressure ratio and the compressor power. This reduced compressor power can cause overspeeding for the air turbo ramjet engine. The experimental results of compressor power and turbine inlet pressure support those analytical results.

Flexible power generation based on solid oxide fuel cell and twin-shaft free turbine engine: Mechanical equilibrium running and design analysis

To investigate the application of hybrid technology in scenarios with high concern for system self-accommodation rapidity, an operationally flexible configuration based on SOFC and twin-shaft free turbine engine has been proposed in this research. The corresponding turbomachinery matching expressions are integrated with thermodynamic and electrochemical descriptions in the novel model so that mechanical equilibrium running states can be guaranteed throughout design and off-design analysis. Inclusion of SOFC and combustor pressure losses (3% and 5%) in high-pressure turbine design can effectively alleviate poor turbine operation and improve cell voltage by 54%, thermal efficiency by 31% under design conditions. For the hybrid gas generator, an integrated calculation algorithm has been developed to satisfy both flow and work compatibility requirements, which essentially constitute a closed binary nonlinear equation set after allowed assignment. The coupling of SOFC not only affects along stream parameters, but also imposes restrictions on the solution scope of the equation set from both horizontal and vertical directions. The flow compatibility between the two mechanically separated turbines finally enables the depiction of equilibrium running line/point on turbomachinery characteristics. With one of the appropriate pairing designs of turbines, the running line can pass through the point of rated rotational speed and compression ratio, where a thermal efficiency of 49.3% is achieved.

Theoretical, Numerical, and Experimental Study on an Unsteady Venturi Flowmeter for Incompressible Flows

Abstract To examine the dynamic characteristics of turbomachinery and cavitation, the pulsating flow rates should be evaluated. As it is difficult to measure these pulsating flow rates quantitatively, systematic research has not been conducted on the dynamic characteristics of turbomachinery and cavitation. In this paper, an unsteady energy equation for a venturi tube has been proposed to measure pulsating flow rates. The pulsating flow rates were calculated using two methods based on the unsteady energy equation for incompressible flows. The first method calculated a pulsating flow rate by using the Euler method. The second one calculated the complex amplitude of a pulsating flow rate using a transfer function derived from the linearized unsteady energy equation. We analytically examined the order of magnitude for unsteady terms. The results indicated that the unknown unsteady loss was much smaller than the unsteady momentum. In the experiment, pulsating flows were generated by a reciprocating piston, and the given pulsating flow was measured using a hot wire anemometer. The pulsating flow rates evaluated by using the proposed methods were validated via numerical simulation and experiment. In particular, the influence of amplitudes on the evaluation of pulsating flow rates was numerically examined. Therefore, the nonlinear effect could be evaluated by using the proposed method, and the time-averaged loss coefficient was enough to evaluate the pulsating flow rate coefficient. The proposed unsteady venturi flowmeter can be applied to a wide range of research fields, such as analyzing dynamic characteristics of flows.

Application of neural network approximation methods in the generalization and presentation of the aircraft gas turbine engine turbomachinery characteristics

A technique of generalizing and representing the characteristics of gas turbine engine (GTE) compressor and turbine using the neural network approximation methods is given. The algorithm of generalizing the experimental performance in mathematical packages on methods of artificial neural networks is shown. Results of approximating and interpolating the characteristics with the use of neural networks based on a multilayer perceptron with different estimated values of π c * and π t * are compared.

Thermal Testing of 255-MW Gas Turbine of a Single-Shaft Combined-Cycle Power Plant

Thermal tests of a single-shaft CCPP are conducted. A procedure for processing the test data is developed. Characteristics of turbomachinery at load N GT ≥ 0.4N r are determined. The high temperature of the exhaust gases (650°C) is provided by adjusting the inlet guide vanes.

Development of a Single Sensor Fast Response Probe for the Measurement of Unsteady Flow behind an Axial Flow Rotor

To evaluate the accurate performance and characteristics of turbomachinery, it is important to measure the unsteady flow phenomena downstream of the rotating blades. This paper presents the development of a fast-response total pressure probe and the necessary calibration procedure for the measurement of unsteady flow field at the exit of blades. The fast-response total pressure probe is fabricated by installing a sensor in the cylindrical head of the probe. In terms of simplicity of the measurement system and data reduction method, this method is more competitive over established methods that use multiple sensors. A novel scheme of using fast response probe and virtual instrumentation technology has been successfully implemented in the current programme in place of conventional measurement methods like five-hole probe, three-hole probe and hot wire anemometer. The experiment is conducted in an axial flow compressor using virtual instrumentation technology with components like signal conditioning system, A...

Fast-response total pressure probe for turbomachinery application

To evaluate the accurate performance and characteristics of turbomachinery, it is important to measure the unsteady flow phenomena downstream of the rotating blades. This paper presents the development of a fast-response total pressure probe for the measurement of the total pressure field at the exit of blades. The result of measurement in a one-stage axial turbine is also presented. The fast-response total pressure probe is fabricated by installing a fast-response pressure sensor in the cylindrical head of the probe. In terms of simplicity of the measurement system and data reduction method, this method is more competitive over established methods that use more than four sensors. The probe is applied to the one-stage axial turbine in order to measure the instantaneous total pressure downstream of rotor blades. The measured instantaneous signal is decomposed to obtain the blade-to-blade pressure distribution. The pressure distribution due to blade passing is clearly captured. Due to the loss generation in the casing region, the total pressure and its amplitude of fluctuation by the blade passing are lower in the shroud and hub region than in mid-span. The total pressure distribution at the exit of the rotor blade is found to be slightly different from blade to blade due to the geometric difference and the different relative positions of the rotor blades and stator vanes. The developed probe successfully measures the accurate total pressure distribution at the rotor exit, and allows the evaluation of the loss distribution and the accurate performance of turbomachinery.

Performance estimation of variable geometry turbines

The concept of using variable geometry to alter the characteristics of turbomachinery has been in existence for many years. Advanced gas turbine engines, especially for aeronautical and naval applications, will extensively use variable geometry turbines and, therefore, a tool must exist that is capable of evaluating the performance of such turbines right from the conceptual stage. With this in mind, a new method based on the improved flow model originally proposed by Wang is presented. The improvements resolve two aspects of the flow model that restrict its widely used possibility: that is, the flow model can be applied only to turbines that work under a subcritical condition and it cannot be applied to variable geometry turbines. After these improvements, the new method can be applied to both single-stage turbines and multi-stage turbines with variable geometry used in any stage. To prove this, two examples are presented in this article. One example is a single-stage variable geometry turbine; the predicted results are examined against the experimental results and a satisfactory conformity is obtained. The good agreement shows that the new method is capable of predicting the performance of variable geometry turbine accurately. The other example is a four-stage turbine with variable geometry used in the first stage. All the results show that the ‘bottom-up’ method is an effective way to predict the performance of variable geometry turbine and it can be used extensively.

Numerical Simulation of Aerodynamic Damping for Flutter Analysis of Turbomachinery Blade Rows

This paper describes the calculation of aerodynamic damping for prediction of e utter characteristics of turbomachinery bladerows.Theunsteady aerodynamicbladeloadsareobtainedbysolving theNavier ‐Stokesequations on a dynamically deforming, body-e tted grid. Phase-lagged boundary conditions are used to model the nonzero interbladephaseangleoscillations,and theenergy exchangemethod isused to calculatetheaerodynamicdamping. The analysis is applied to calculate e utter of a transonic forward-swept fan cone guration, which showed e utter at part speed conditions in wind-tunnel tests. The analysis successfully identie ed the most critical mode and the e ow characteristics responsible for the observed e utter. The location of shock wave and variation of its strength were found to strongly ine uence the aerodynamic damping, with outboard stations providing the main contribution. The results also demonstrate that changes in blade shape impact the calculated aerodynamic damping, indicating the importance of using an accurate blade operating shape under centrifugal and steady aerodynamic loading. Sensitivity of thecalculated aerodynamic damping to variation in inlet and exit conditions, the computational time steps, and blade natural frequency are also reported.

Effect of the Specific Heat Ratio on the Aerodynamic Performance of Turbomachinery

Many gases, including carbon dioxide and argon, have been considered as alternative working fluids to air in a number of design studies for closed and semi-closed gas turbine engines. In many of these studies, it has been assumed that if the gas constant R and specific heat ratio γ are included in the speed and flow parameters, the compressor map or turbine characteristic is applicable to other working fluids. However, similarity arguments show that the isentropic exponent itself is a criterion of similarity and that the turbomachinery characteristics, even when appropriately nondimensionalized, will, in principle, vary as the γ of the working fluid varies. This paper examines the effect of γ on turbomachinery characteristics, mainly in terms of compressors. The performance of a centrifugal compressor stage was measured using air (γ=1.4), CO2(γ=1.29), and argon (γ=1.67). For the same values of the nondimensional speed, the pressure ratio, efficiency, and choking mass flow were found to be significantly different for the three test gases. The experimental results have been found to be consistent with a CFD analysis of the impeller. Finally, it is shown that the changes in performance can be predicted reasonably well with simple arguments based mainly on one-dimensional isentropic flow. These arguments form the basis for correction procedures that can be used to project compressor characteristics measured for one value of γ to those for a gas with a different value.

Velocity Measurements Downstream of the Impellers in a Multistage Centrifugal Blower

The paper presents the results of an experimental investigation on a four-stage centrifugal blower, having the aim of obtaining an accurate description of the flow field behind the impellers in several operative conditions and for different geometric configurations. Actually, the test plant allows one to change the turbomachinery characteristics assembling one, two, three, or four stages and three different types of diffuser. In this first research step, the blower has been tested in the four-stage vaneless diffuser configuration. The unsteady flow field behind the impellers and in the diffusers has been measured by means of a hot-wire anemometer. A phase-locked ensemble-averaging technique has been utilized to obtain the relative flow field from the instantaneous signals of the stationary hot-wire probes. Several detailed measurement sets have been performed using both single and crossed hot-wire probes, to obtain the velocity vectors and turbulence trends, just behind the blower impellers and in several radial positions of the vaneless diffusers. These measurements have been done at different flow rate conditions, covering unsteady flow rate phenomena (rotating stall) also. The results obtained allowed us to get a detailed flow field analysis in the multistage centrifugal blower, in relation to the geometric configuration and to the differing operating conditions.

ターボ機械の非定常特性

ターボ機械の非定常特性