Ejector Tip Injection for Active Compressor Stabilization

2014 ◽  
Author(s):  
Marcel Stößel ◽  
Stefan Bindl ◽  
Reinhard Niehuis
Keyword(s):  
Mass Flow ◽  
Safety Margin ◽  
Stability Limit ◽  
Low Pressure ◽  
Injection System ◽  
Air Mass ◽  
Propulsion Efficiency ◽  
Operating Range ◽  
Ejector Pump ◽  
Pressure Compressor

In propulsion industry there is an ongoing need to significantly reduce SFC of jet engines resulting in cost reduction and lower emissions. Since the design of most of the engine components is at the limit of today’s technology level further gain of improvement on short term is to be achieved by implementation of new system concepts. Especially the stall safety margin in compression system design holds high potential for the optimization of the overall engine system. Once a reliable and effective stall control system becomes available an extension of present operating range is likely to be achieved by moving the steady operating line towards the stability limit and to intervene only in critical situations. At the Institute of Jet Propulsion at the University of the Federal Armed Forces in Munich, Germany a Larzac 04 twin-spool turbofan engine has already been equipped and tested with an adequate active stabilization system of the low pressure compressor for research purposes. Those investigations revealed a strong dependency of the achievable stabilization effect and the amount and momentum of the injected air mass flow. For flying applications this mass flow has to be delivered by carried on means. Therefore it always penalizes the propulsion efficiency. In the given configuration, redirected air from the last stage of the high pressure compressor is used for injection. Usage of this bleed air directly influences the propulsion efficiency of the engine. In order to optimize the mass flow needed for stabilization, the existing injection system was redesigned to utilize ejector pumps. With this configuration a comparable stabilizing effect could be realized with less redirected air mass flow. In fact the open ejector pump configuration showed an even higher performance at maximum injection rate than the closed injection before. Therefore further investigations with this system focused on the effect of additional flow ports to the engine intake as they are necessary for an ejector pump and their basic influence on the operation stability of the low pressure compressor (LPC). In combination with the already existing stall detection algorithm of the institute a very promising system for increasing the available operating range in turbo compressors could be achieved.

Three-Stage Low Pressure Compressor Modernization by Means of Optimization Methods

2015 ◽  
Author(s):  
Evgenii Goryachkin ◽  
Grigorii Popov ◽  
Oleg Baturin ◽  
Daria Kolmakova
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Optimization Methods ◽  
Low Pressure ◽  
Optimal Combination ◽  
Pareto Set ◽  
Optimization Task ◽  
Efficiency Increase ◽  
Optimization Parameters ◽  
Pressure Compressor

Low pressure compressor operation has some features. Firstly, the LPC stages work with cold air. For this reason there is transonic or subsonic flow in LPC. Secondly, the flow in LPC has complex spatial structure. Blade geometry of LPC is described by a large number of parameters. For this reason, it is difficult to pick up optimal combination of parameters manually. The solution of this problem is the usage of optimization methods to find the optimal combination of parameters. This approach was tested in this work. The main goal of this work was the LPC modernization for new parameters of gas turbine engine. Set of unimprovable solutions (Pareto set) was obtained as a result of solving optimization task. Pareto set was a compromise between the efficiency increase and the mass flow decrease. Each point from Pareto set had a correspondence with LPC unique geometry represented as an array of optimization parameters. One point of the Pareto set met all the required parameters of modernized LPC. The LPC geometry that guaranteed the efficiency increase by 1,3%, the total pressure ratio increase by 4% and mass flow rate decrease by 11% in comparison with the original LPC was obtained as a result of the investigation.

Dynamic Reference Value Generation for the Control of a Diesel Engine With HP- and LP-EGR

2010 ◽  
Author(s):  
Matthias Mrosek ◽  
Rolf Isermann
Keyword(s):  
High Pressure ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Exhaust System ◽  
Reference Value ◽  
Low Pressure ◽  
Gas Composition ◽  
Air Mass ◽  
Intake System

A combination of a low-pressure EGR and a high-pressure EGR for Diesel engines can effectively reduce the NOx emissions. In comparison to a conventional high-pressure EGR, the combination with a low-pressure EGR introduces an additional degree of freedom for the air path control. From control perspective the weaker couplings with the charging pressure and the dynamics of the gas composition in the intake and exhaust system are the major differences between the low-pressure and the high-pressure EGR. The lower gas temperature of the low-pressure EGR further reduces the emissions. A control oriented model is presented to control the gas composition in the intake system. Therefore a reference value transformation converts a desired air mass flow rate into a desired gas composition in the intake system. Depending on the dynamical gas compositions in the intake and exhaust system, the reference value of the desired gas composition results in a setpoint for a high-pressure EGR mass flow rate controller. Due to the faster dynamics of the high-pressure EGR, this controller accounts for the fast dynamical effects in the gas system. The presented control structure in combination with the reference value generation is invariant to model and sensor uncertainties and results stationary in an air mass flow rate control. As additional control variable, the intake temperature is controlled by the low-pressure EGR mass flow rate. A calibrated desired temperature delivers the setpoint for a low-pressure EGR mass flow rate controller.

Stall Detection Within the Low Pressure Compressor of a Twin-Spool Turbofan Engine by Tip Flow Analysis

2009 ◽  
Author(s):  
Stefan Bindl ◽  
Marcel Sto¨ßel ◽  
Reinhard Niehuis
Keyword(s):  
Low Pressure ◽  
Detection Algorithm ◽  
Injection System ◽  
Test Facility ◽  
Aviation Industry ◽  
Engine Fuel ◽  
Engine Operation ◽  
Turbofan Engine ◽  
Jet Propulsion ◽  
Pressure Compressor

In order to preserve fossil resources aviation industry faces major challenges to reduce engine fuel consumption. Therefore efforts are concentrated to increase efficiency of any engine component. Investigations at the Institute of Jet Propulsion at the University of Federal Armed Forces in Munich focus on the compressor module. The compression system is designed to work at very high loads and due to this it is one of the most critical components during transient engine operation. Occurring instabilities are mostly limited to the tip region of the compressor blades because of the tip clearance and low momentum fluid from the casing boundary layer. Prior to instability onset such as rotating stall and even surge, some so-called stall precursors commonly occur in this area. In order to predict and avoid those critical engine operations a stall detection algorithm was developed and combined with an active compressor stabilization system. As a research vehicle the Larzac 04 twin-spool turbofan engine is used at the test facility of the Institute of Jet Propulsion. The test vehicle is equipped with additional instrumentation and control systems exceeding those of conventional engine monitoring systems by far. Providing input data to the stall detection algorithm flush mounted Kulite sensors are installed within the casing of the first stage of the low pressure compressor, where stall usually arises in the Larzac 04. The described algorithm is based on the spike theory being the dominant stall precursor in nearly all operating ranges of the test engine. After the detection of an upcoming stall event active countermeasures are triggered to avoid critical engine operation. For this reason an air injection system was attached in front of the fan stage to affect the blade tip region by injecting additional air at a high velocity to re-establish the blade flow. The main emphasis of this paper is to illustrate the signal conditioning used for stall detection and to prove the reliable function of the algorithm in combination with an active countermeasure at an aircraft engine.

Predicting the Port Air Mass Flow of SI Engines in Air/Fuel Ratio Control Applications

2000 ◽  
Author(s):  
Alain Chevalier ◽  
Christian Winge Vigild ◽  
Elbert Hendricks
Keyword(s):  
Mass Flow ◽  
Control Applications ◽  
Air Mass ◽  
Fuel Ratio ◽  
Si Engines

Autostoichiometric vapor deposition: Part I. Theory

1995 ◽  
Vol 10 (10) ◽  
pp. 2536-2541 ◽  
Author(s):  
Ren Xu
Keyword(s):  
Mass Flow ◽  
Vapor Deposition ◽  
Flow Analysis ◽  
Quantitative Measure ◽  
Low Pressure ◽  
Potential Candidate ◽  
Organic Complexes ◽  
Reaction Schemes

The possibility of an autostoichiometric vapor deposition is explored. Heterometal-organic complexes such as double alkoxides are potential candidate precursors for such deposition. Two reaction schemes, the hydrolysis-assisted pyrolysis and the hydrolysis-polycondensation of double alkoxides, are identified to be autostoichiometric reactions. A simple low-pressure apparatus is suggested for autostoichiometric vapor deposition. Mass-flow analysis allows for the identification of a nonstoichiometry factor K which can be used as a quantitative measure of the precursor's autostoichiometric capability.

Implementation of a Rig Test for Rotor/Stator Interaction of Low-Pressure Compressor Blades and Comparison of Experimental Results With Numerical Model

2020 ◽  
Author(s):  
Laura Pacyna ◽  
Alexandre Bertret ◽  
Alain Derclaye ◽  
Luc Papeleux ◽  
Jean-Philippe Ponthot
Keyword(s):  
Low Cost ◽  
Low Pressure ◽  
Angular Speed ◽  
Compressor Blades ◽  
Abradable Coating ◽  
Rotor Stator Interaction ◽  
Blade Tip ◽  
Numerical Tool ◽  
Short Time ◽  
Pressure Compressor

Abstract To investigate the contact phenomenon between the blade tip and the abradable coated casing, a rig test was designed and built. This rig test fills the following constraints: simplification of the low-pressure compressor environment but realistic mechanical conditions, ability to test several designs in short time, at low cost and repeatability. The rig test gives the opportunity to investigate the behavior of different blade designs regarding the sought phenomenon, to refine and mature the phenomenon comprehension and to get data for the numerical tool validation. The numerical tool considers a 3D finite elements model of low-pressure compressor blades with a surrounding rigid casing combined with a specialized model to take into account the effects of the wear of the abradable coating on the blade dynamics. Numerical results are in good agreement with tests in terms of: critical angular speed, blade dynamics and wear pattern on the abradable coated casing.

Low-Pressure Compressor Near-Stall Predictions Using Unsteady CFD Methods

2021 ◽  
Author(s):  
David Vanpouille ◽  
Dimitrios Papadogiannis ◽  
Stéphane Hiernaux
Keyword(s):  
Low Pressure ◽  
Navier Stokes ◽  
Phase Lag ◽  
Sliding Mesh ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Surge Margin ◽  
Large Eddy ◽  
Unsteady Rans ◽  
Pressure Compressor

Abstract Surge margin is critical for the safety of aeronautical compressors, hence predicting it early in the design process using CFD is mandatory. However, close to surge, steady-state Reynolds Averaged Navier-Stokes (RANS) simulations are proven inadequate. Unsteady techniques such as Unsteady RANS (URANS) and Large Eddy Simulation (LES) can provide more reliable predictions. Nevertheless, the accuracy of such methods are dependent on the method used to handle the rotor/stator interfaces. The most precise method, the sliding mesh, requires simulating the full annulus or a periodic sector, which can be very costly. Other techniques to reduce the domain exist, such as the phase-lagged approach or geometric blade scaling, but introduce restrictive assumptions on the flow at near-stall conditions. The objective of this paper is to investigate the near-stall flow of a low-pressure compressor using unsteady methods of varying fidelity: URANS with the phase lag assumption, URANS on a periodic sector and a high-fidelity LES on a smaller periodic sector achieved using geometric blade scaling. Results are compared to experimental measurements. An overall good agreement is found. Results show that the tip leakage vortex is not the origin of the stall on the studied configuration and a hub corner separation is initiated. LES further validates the (U)RANS flow predictions and brings additional insight on unsteady flow separations.

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