Semih Olcmen

Soft computing applications on a SR-30 turbojet engine

The use of soft computing algorithms in hardware-in-the-loop applications has been investigated. A fuzzy logic controller (FLC) was designed and successfully tested on the Turbine Technologies SR-30 turbojet engine for the main-stage operation of the engine. A transfer function model of the plant was obtained using frequency-response methods. To ensure safe operation of the engine, a PID controller was first tested on the engine, and both the PID and FLC controllers were tested in a simulated environment before being used with the engine.

A spark-plug LDV probe for in-cylinder flow analysis of production IC engines

Development of a sub-miniature, traversable, two-simultaneous velocity component fibre-optic, laser-Doppler velocimetry (LDV) probe for flow measurements in a production-car IC engine is discussed. The probe is manufactured to fit into an M8 spark-plug hole and it can be traversed 50 mm allowing measurements inside the engine cylinder including the spark-plug location. The probe has been first tested in a steady free round jet and next has been employed on a Honda CIVIC LX car engine for preliminary time-dependent velocity measurements at 10 mm and 36 mm into the engine cylinder. Results indicate lower turbulence intensity values closer to the spark plug than into the engine.

A miniature laser-Doppler velocimeter for simultaneous three-velocity-component measurements

A miniature laser-Doppler velocimeter (LDV) system was developed to make simultaneous three-velocity-component measurements. The probe has been tested in a zero-pressure gradient two-dimensional turbulent boundary layer and the results agree well with earlier data and several DNS data sets. The overall size of the probe is 23.3 mm × 8.7 mm × 90.6 mm and measurement spatial resolution is 50 µm. The probe volume can be traversed 32 mm vertically. The lightweight and compact design of the LDV probe head allows the probe head to be embedded inside models and machinery for three-dimensional turbulent flow measurements where larger probes are unusable.

Supersonic, variable-throat, blow-down wind tunnel control using genetic algorithms, neural networks, and gain scheduled PID

Abstract In this paper the design and application of a control algorithm is discussed to control the test conditions within plenum chamber and the test section of a supersonic blow-down, variable throat wind tunnel at the University of Alabama. The artificially intelligent controller algorithm was designed using a gain scheduled Proportional-Integral-Differential (PID) control approach. The PID controller was augmented to work with time variant properties of the control problem by determining a functional form of the integral term of the controller from the governing equations of the tunnel. The controller was optimized using genetic algorithms (GA) on a neural network (NN) model of the tunnel and was compared to a conventional PID controller using the same NN model. The process was repeated for different throat settings to find the control gains for each setting. The controller algorithm was next applied to the actual wind tunnel at different throat settings and the results were compared. The optimized controller is proven to work very well at every throat setting.

Experimental study of a round jet impinging on a convex cylinder

The flow physics of a free round air jet prior to impinging on a convex cylindrical surface is discussed. Two components of mean velocity, normal stress and shear stress profiles were obtained using a novel fibre-optic, two-simultaneous velocity component laser-Doppler velocimetry probe. Velocity profiles obtained at seven axial locations in the impinging jet case are compared to profiles obtained at eight axial locations away from the jet exit to determine the surface effects on the free jet. The Reynolds number of the flow based on the jet diameter was Re = 25 000 and the convex cylinder was located at x/d = 4.0 (jet exit velocity, Uj = 24 m s−1; jet diameter, d = 15.24 mm; circular cylinder diameter, D = 60.5 mm). Flow visualization results show that the initially axisymmetric jet becomes a three-dimensional flow, wraps itself on the cylinder across the cylinder and also behaves similar to a wall jet along the cylinder axis. The jet axial mean velocity starts reducing sharply one diameter (1d) away from the cylinder. The jet axial, radial, tangential normal stresses and the shear stress are not affected by the presence of the surface in the vicinity of the jet axis until 0.05d away from the surface, and are affected near the jet edge about 0.75d away from the surface.

Miniature rainbow schlieren deflectometry system for quantitative measurements in microjets and flames

Recent interest in small-scale flow devices has created the need for miniature instruments capable of measuring scalar flow properties with high spatial resolution. We present a miniature rainbow schlieren deflectometry system to nonintrusively obtain quantitative species concentration and temperature data across the whole field. The optical layout of the miniature system is similar to that of a macroscale system, although the field of view is smaller by an order of magnitude. Employing achromatic lenses and a CCD array together with a camera lens and extension tubes, we achieved spatial resolution down to 4 mum. Quantitative measurements required a careful evaluation of the optical components. The capability of the system is demonstrated by obtaining concentration measurements in a helium microjet (diameter, d=650 microm) and temperature and concentration measurements in a hydrogen jet diffusion flame from a microinjector (d=50 microm). Further, the flow field of underexpanded nitrogen jets is visualized to reveal details of the shock structures existing downstream of the jet exit.

Octant analysis based structural relations for three-dimensional turbulent boundary layers

A flow structure based triple-product correlation model developed by Nagano and Tagawa [J. Fluid Mech. 215, 639 (1990)] has been expanded to three-dimensional turbulent flows. Three-dimensional turbulent boundary layer data obtained away from the vortex in a wing-body junction flow are analyzed to calculate the contributions from eight velocity octants to the stresses and higher-order products. The analysis showed that the sweep and ejection modes dominate the flow physics of some shear stresses and some triple products, while the interaction modes are negligible away from the wall. These experimental observations are used together with the extended Nagano-Tagawa mathematical model to obtain relations among the triple products in three-dimensional turbulent boundary layers that can simplify the turbulent diffusion modeling used in Reynolds-averaged Navier-Stokes equations. Results show that u3¯, u2v¯, and v3¯ triple product correlations can be modeled if an appropriate turbulence model is described fo...

Use of soft computing technologies for rocket engine control

NASA issues and remedial applications for rocket engine control are presented. A testbed for researching these applications is presented and further detailed. Automation and control of the operation of the testbed, a Turbine Technologies SR-30 (single radial) small turbojet engine, is discussed. A fast data acquisition board, fuel-flow rate meter, a valve controller are implemented to the existing system, which was already equipped with pressure, temperature, RPM and load sensors. Start, operation and stop sequences are automated using National Instruments Labview software. Classic PID control algorithm is applied in the initial phase of the automation. Data collected during the start, transient/steady operation, and stop sequences of the engine has been analyzed to design a Bayesian Belief control algorithm. PID algorithm implementation and fuzzy algorithms are currently being conducted.

Influence of Passive Flow-Control Devices on the Pressure Fluctuations at Wing-Body Junction Flows

The effectiveness of passive flow-control devices in eliminating high surface rms pressure fluctuations at the junction of several idealized wing/body junction flows was studied. Wall-pressure fluctuation measurements were made using microphones along the line of symmetry at the wing/body junction of six different wing shapes. The wings were mounted on the wind tunnel floor at a zero degree angle-of-attack. The six wing shapes tested were: a 3:2 semi-elliptical-nosed NACA 0020 tailed generic body shape (Rood wing), a parallel center-body model, a tear-drop model, a Sandia 1850 model, and NACA 0015 and NACA 0012 airfoil shapes. Eight different fence configurations were tested with the Rood wing. The two double-fence configurations were found to be the most effective in reducing the pressure fluctuations. Two of the single fence types were nearly as effective and were simpler to manufacture and test. For this reason one of these single fence types was selected for testing with all of the other wing models. The best fence flow-control devices were found to reduce rms wall-pressure fluctuations by at least 61% relative to the baseline cases. DOI: 10.1115/1.2746917

A miniature three-component LDV probe

In this paper, development of a three-simultaneous-velocity component, miniature, traversable fibre-optic laser Doppler velocimetry probe head is described. The cylindrical probe head has a diameter of D = 12 mm and a length of about L = 75 mm. While the two velocity components perpendicular to the probe axis are measured using conventional laser- Doppler velocimetry concepts, the third component along the probe axis is measured using a heterodyne technique. The miniature probe was designed small enough to be inserted into wind-tunnel models and to fit into most common spark-plug ports to make measurements in working car engines. The probe was initially tested in a round free-jet flow to demonstrate its capabilities.