Anthony J. Gannon

Solar Chimney Cycle Analysis With System Loss and Solar Collector Performance

An ideal air standard cycle analysis of the solar chimney power plant gives the limitingperformance, ideal efficiencies and relationships between main variables. The presentpaper includes chimney friction, system, turbine and exit kinetic energy losses in theanalysis. A simple model of the solar collector is used to include the coupling of the massflow and temperature rise in the solar collector. The method is used to predict the per-formance and operating range of a large-scale plant. The solar chimney model is verifiedby comparing the simulation of a small-scale plant with experimental data.@S0199-6231~00!00503-7#

Solar Chimney Turbine Performance

An experimental investigation of the performance of a solar chimney turbine is presented. The design features a single rotor and uses the chimney supports as inlet guide vanes (IGVs) to introduce pre-whirl. This reduces the turbine exit kinetic energy at the diffuser inlet and assists the flow turning in the IGV-to-rotor duct. The rotor configuration allows the supports to be placed directly under the chimney walls. Measurements from a scale model turbine are used to calculate the turbine performance and efficiency. Efficiencies over a wide operating range and detailed performance measurements at two operating points are presented. Total-to-total efficiencies of 85-90% and total-to-static of 77-80% over the design range are measured. The detailed measurements give insight into the turbine performance and possible design improvements. These results allow more accurate simulation of solar chimney power plants.

Compressible flow through solar power plant chimneys

Chimneys as tall as 1500 m may be important components of proposed solar chimney power plants. The exit air density will then be appreciably lower than the inlet density The paper presents a one-dimensional compressible flow approach for the calculation of all the thermodynamic variables as dependent on chimney height, wall friction, additional losses, internal drag and area change. The method gives reasonable answers even over a single 1500 m step length used for illustration, but better accuracy is possible with multiple steps. It is also applicable to the rest of the plant where heat transfer and shaft work may be present. It turns out that the pressure drop associated with the vertical acceleration of the air is about three times the pressure drop associated with wall friction. But flaring the chimney by 14 percent to keep the through-flow Mach number constant virtually eliminates the vertical acceleration pressure drop.

Pressure Drop in Solar Power Plant Chimneys

The paper investigates the flow through a representative tall solar chimney with seven sets of internal bracing wheels with radial spokes. The paper presents experimental data measured in a 0.63 m diameter laboratory scale chimney model with and without bracing wheels. A fan at one end of the chimney model either sucked or blew the flow through it. The measured friction pressure drop was higher than theoretical values for smooth walls, and swirling, blown flow increased it by another 12%. The seven bracing wheels, each had twelve spokes, each spoke consisting of a pair of rectangular section bars, caused order of magnitude larger pressure drops than wall friction. For the sucked-through flow the forced, swirling, disturbed flow increased the pressure drop by up to 36%. Bracing wheels also increased the exit kinetic energy coefficient to 1.26 with the last wheel at the chimney exit. This effect could in combination with the bracing wheel drag reduce flow through the chimney. Designers of large chimneys should take care to minimise the number of bracing wheels, and possibly to streamline spoke sections. If possible, the top bracing wheel should be far enough from the exit for the flow to reattach to the wall after passing over the spoke attachment rim at the wall.Copyright

Solar Chimney Turbine: Part 1 of 2 — Design

The solar chimney is a simple renewable energy source consisting of three main components, a solar collector, chimney and turbine. Air under the collector is heated by the greenhouse effect. This less dense air rises up a chimney at the collector centre and drives an electricity-generating turbine. The operation of a solar chimney power plant is simple but high component efficiencies are needed for successful operation. A turbine design based on the design requirements for a full-scale solar chimney power plant is presented. The design integrates the turbine with the chimney. It is proposed that the chimney base legs be offset radially to act as inlet guide vanes and introduce pre-whirl before the rotor to reduce the exit kinetic energy. A three-step turbine design method is presented. A free vortex analysis method is used to determine the major turbine dimensions. A matrix throughflow method predicts the flow path through the inlet guide vanes and rotor. Finally the blade profiles are design using an optimization scheme coupled to a surface vortex method to achieve blades of minimum chord and low drag. The proposed turbine design can extract over 80% of the power available in the flow.Copyright

Pre-Stall Instability Distribution Over a Transonic Compressor Rotor

The present study was part of the compressor research program sponsored by the Propulsion and Power Department of the Naval Air Warfare Centre, Patuxent River, MD with Ravi Ravindranath as the technical monitor.

Design and Test of a Transonic Axial Splittered Rotor

A new design procedure was developed that uses commercial-off-the-shelf software (MATLAB, SolidWorks, and ANSYS-CFX) for the geometric rendering and analysis of a transonic axial compressor rotor with splitter blades. Predictive numerical simulations were conducted and experimental data were collected in a Transonic Compressor Rig. This study advanced the understanding of splitter blade geometry, placement, and performance benefits. In particular, it was determined that moving the splitter blade forward in the passage between the main blades, which was a departure from the trends demonstrated in the few available previous transonic axial compressor splitter blade studies, increased the mass flow range with no loss in overall performance. With a large 0.91 mm (0.036 in) tip clearance, to preserve the integrity of the rotor, the experimentally measured peak total-to-total pressure ratio was 1.69 and the peak total-to-total isentropic efficiency was 72 percent at 100 percent design speed. Additionally, a higher than predicted 7.5 percent mass flow rate range was experimentally measured, which would make for easier engine control if this concept were to be included in an actual gas turbine engine.© 2015 ASME

The Effect of Steam Ingestion on Transonic Rotor Stall Margin

The adverse effect of high temperature water vapor on the stall margin of a transonic compressor rotor is investigated. This type of flow condition is experienced during the takeoff of carrier born aircraft. An experiment is designed to replicate these flow conditions on a transonic compressor test rig. The transient inlet conditions are measured and the changes in gas properties as well as the reduction in stall margin for differing steam inlet pressures are presented. High speed data measurements are used to investigate the initial conditions of the compressor before steam is introduced to the flow. Evidence of pre-cursors rotating at near half rotor speed are found and the strength of these appear to give an indication of the compressor’s susceptibility to stall.

Experimental and Computational Investigation of Cross-Flow Fan Propulsion for Lightweight VTOL Aircraft

Cross-flow fan propulsion has not been seriously considered for aircraft use since an Vought Systems Division (VSD) study for the U.S. Navy in 1975. A recent conceptual design study of light-weight, single seat VTOL aircraft suggest that rotary-engine powered cross-flow fans may constitute a promising alternative to the conventional lift-fan vertical thrust augmentation systems for VTOL aircraft. The cross-flow fan performance data obtained by VSD supported the hypothesis that they could be improved to the point where their thrust augmentation could be used in a VTOL aircraft. In this paper we report results of a NASA Glenn supported experimental and computational cross-flow fan investigation which is currently in progress and we provide an assessment of the potential suitability of crossflow fans for VTOL aircraft propulsion. The tests are carried out in the Turbopropulsion Laboratory of the Naval Postgraduate School, using an existing Turbine Test Rig as a power source to drive the cross-flow fan. A 0.305 m (12-inch) diameter, 38.1 mm (1.5-inch) span cross-flow fan test article was constructed to duplicate as closely as possible the VSD fan so that baseline comparison performance data could be obtained. Performance measurements were taken over a speed range of 1,000 to 7,000 RPM and results comparable to those measured by Vought Systems Division were obtained. At 3,000 RPM a 2:1 thrust-to-power ratio was measured which dropped to one as the speed was increased to 6,000 RPM. Performance maps were experimentally determined for the baseline configuration as well as one with both cavities blanked off, for the speed range from 2,000 to 6,000 rpm. Using Flo++, a commercial PC-based computational fluid dynamics software package by Softflo, 2-D numerical simulations of the flow through the cross-flow fan were also obtained. Based on the performance measurements it was concluded that the optimum speed range for this rotor configuration was in the 3,000 to 5,000 rpm range. The lower speed producing the best thrust-to-power ratio and the upper speed range producing the highest efficiency over sizeable throttling range.Copyright

Axial Transonic Rotor and Stage Behavior Near the Stability Limit

Transient casing pressure data from a transonic rotor and rotor-stator stage measured using high-speed pressure probes embedded in the casewall over the rotor tips are analyzed. Using long data sets sampled at a high frequency, low-frequency (less than once-per-revolution) nonaxisymmetric flow phenomena were detected while operating at steady-state conditions near stall. Both the rotor and stage cases are investigated, and the difference in behavior of a rotor with and without a stator blade row is investigated. Data for both cases over the speed range 70–100% of design and from choke to near the stability limit (stall or surge) are presented. The root mean square power of the low-frequency signal as well as its fraction of the total pressure signal is presented. It was thought that the behavior of these signals as stall was approached could lead to some method of detecting the proximity of stall. For the rotor-only configuration, the strength of these nonaxisymmetric phenomena increased as stall was approached for all speed-lines. However, for the stage configuration, more representative of an operational machine, these were of a lower magnitude and did not exhibit a clearly increasing trend as stall was approached. This would seem to indicate that the stator suppressed these signals somewhat. It is also shown that these nonaxisymmetric phenomena led to a significant variation of the mean relative inlet flow angle into the rotor blade. During stable operation near to stall at 100% speed for the rotor-only case, a 1.9 deg variation of this angle was measured. This compared with a 5.6 deg variation over the entire speed-line. Further, it was observed that while the rotor and stage cases had different stability limits, their peak relative inlet flow angles near stall were similar for both along most speed-lines.