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This work develops a methodology for full engine FEA simulation of the fan blade off containment test for a jet engine using LS-Dyna. The fan blade off containment test is a safety requirement involving the intentional release of a fan blade when the engine is running at full power. The released blade must not pierce or fracture the engine cases during the impact or rotating unbalance. The novel feature of the LS-Dyna simulation is the extensive full engine geometry as well as the widespread use of nonlinearities (mainly plasticity and friction) to absorb the large kinetic energies of the engine rotors. The methodology is simple to use, runs quickly and is being recognized by industry as a contender for widespread implementation. Future applications look promising enough that the methodology warrants further development and refinement.

This work develops a methodology for full engine FEA simulation of the fan blade off containment test for a jet engine using LS-Dyna. The fan blade off containment test is a safety requirement involving the intentional release of a fan blade when the engine is running at full power. The released blade must not pierce or fracture the engine cases during the impact or rotating unbalance. The novel feature of the LS-Dyna simulation is the extensive full engine geometry as well as the widespread use of nonlinearities (mainly plasticity and friction) to absorb the large kinetic energies of the engine rotors. The methodology is simple to use, runs quickly and is being recognized by industry as a contender for widespread implementation. Future applications look promising enough that the methodology warrants further development and refinement.

A new method for predicting forced vibratory blade response to total pressure distortion has been developed using modal and harmonic analysis. Total pressure distortions occur in gas turbine engines when the incoming airflow is partially blocked or disturbed. Distorted inlet conditions can have varying effects on engine performance and engine life. Short-term effects are often in the form of performance degradation where the distorted airflow causes a loss in pressure rise, and a reduction in mass flow and stall margin. Long-term effects are a result of vibratory blade response that can ultimately lead to high cycle fatigue (HCF), which in turn can quickly cause partial damage to a single blade or complete destruction of an entire compressor blade row, leading to catastrophic failure of the gas turbine engine. A better understanding and prediction of vibratory blade response is critical to extending engine life and reducing HCF-induced engine failures. This work covers the use of finite element modeling coupled with computational fluid dynamics-generated pressure fields to create a generalized forcing function. The first three modes of a low-aspect-ratio, transonic, first stage blade of a two-stage fan were examined. The generalized forcing function was decomposed to the frequency domain to identify the dominant harmonic magnitude present, as well as other contributing harmonics. An attempt to define the relationship between modal force with varying total pressure distortion levels produced a sensitivity factor that describes the relationship in the form of a simple multiplier. A generalized force was applied to the blade and varied harmonically across a frequency range known to contain the first natural frequency. The mean rotor stress variation was recorded and compared to experimental results to validate the accuracy of the model and verify its ability to predict vibratory blade response accurately. / Master of Science

A flex-fan has flexible blades which undergo large deformation under centrifugal forces to give the desired air-flow and power-consumption characteristics with speed. The finite element technique has been used to obtain the deflected shape of the blade of such a fan used for automobile radiator cooling. The natural frequencies of vibration are also evaluated at different speeds, up to 5,000 rpm. A partially conforming deflection function has been used in the analysis. The blade has been treated as a thin shell, idealized as an assembly of thin flat triangular elements. / Thesis / Master of Engineering (ME)

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Axial flow fans used in large-scale air-cooled steam condensers (ACSCs) may operate under distorted inflow conditions. These conditions occur due to the prevailing wind conditions, the presence of buildings, and the location of the fan within the ACSC. Fans located on the periphery of the ACSC are affected the most due to their exposure to strong winds and the inner fans drawing in air past them. Distorted inflow conditions cause varying fan blade and gearbox loading conditions. The purpose of the investigation was to simultaneously measure the inlet air flow and the resultant blade and gearbox loading conditions of a single fan located on the periphery of a large-scale ACSC. Inlet and heat exchanger bundle outlet air flow velocities were measured using a combination of ultrasonic and propeller anemometers while blade loading was measured with strain gauges attached at the neck of the specific blade being monitored. Strain gauges were also attached to the low-speed fan shaft to measure gearbox loading. Measurements were recorded over a period of 8 days where it was found that increased wind resulted in increased air flow in the axial direction of the fan, which then caused a reduction in average blade loading. This was due to a decreased static pressure rise over the fan. The fan blade was found to vibrate at its own natural frequency of 6 Hz when excited by the variable aerodynamic loading. The aerodynamic loading was extracted from the measured data and was found to correlate well with previous experimental work performed by Bredell et al. (2006a). Shaft bending stresses and torque were found to oscillate at the fan’s rotational frequency of 2Hz with a large torque exerted on the shaft during fan start-up. / AFRIKAANSE OPSOMMING: Aksiaalvloeiwaaiers wat by groot lugverkoelde stoomkondensors gebruik word, werk dikwels onder verwronge inlaat lugvloei toestande wat geskied as gevolg van heersende winde, die teenwoordigheid van geboue en die posisie van die waaier in die kondensor. Waaiers wat geleë is op die rand van die kondensor word die meeste beïnvloed as gevolg van blootstelling aan die sterk winde en dwarsvloei wat deur die binneste waaiers geïnduseer word. Verwronge inlaat lugvloei veroorsaak gevolglik variërende waaierlem en ratkas belastingstoestande. Die doel van hierdie ondersoek was om terselfdetyd die inlaat lugvloei asook waaierlem en ratkas belastingstoestande van ’n enkele waaier wat op die rand van ’n grootskaalse lugverkoelde stoomkondensor geleë is, te meet. Waaier inlaat en warmteruiler uitlaat lugvloei snelhede is gemeet met ’n kombinasie van ultrasoniese- en skroefwindsnelheidsmeters terwyl die lem en ratkas belastings gemeet is met rekstrokies. Metings is oor ’n tydperk van 8 dae geneem. Die bevindinge toon dat ’n toename in windsnelheid ’n toename in aksiale lugvloei tempo, deur die waaier veroorsaak. ’n Afname in die gemiddelde lembelasting is waargeneem as gevolg van ’n afname in die waaier statiese druk. Daar is ontdek dat die waaierlem teen ’n natuurlike frekwensie van 6 Hz vibreer wanneer dit opgewek word deur die wisselende aerodinamiese belasting. Die aerodinamiese belasting is verkry uit die gemete data en vergelyk goed met die numeriese werk van Bredell et al. (2006a). Daar is ook bevind dat waaier-as buigspannings en wringkragte ossileer teen die waaier se rotasiefrekwensie van 2Hz met ’n groot wringkrag wat op die as uitgeoefen word wanneer die waaier aangeskakel word. iii

Examensarbetet går ut på att frambringa några principkonstruktioner till axialfläktar med fasta inställbara skovlar åt FläktWoods. Fläktarna det rör sig om är stora industrifläktar med en diameter mellan en och fem meter, som används för att till exempel transportera ner luft i gruvor. Endast förslag till principkonstruktioner tas fram och ej en färdig produkt, syftet med rapporten är i första hand att ge FläktWoods konstruktörer ett annat synsätt på problemet. Två olika delar av fläkten undersöks, dels fästet av skoveln på hjulet, dels själva hjulet i sig. Tillvägagångssättet är att från formulerat problem tas först några förslag fram, de utvärderas sedan och de bästa går vidare till nästa steg. Utvärderingen sker med hjälp av produktförslagsdiagram samt genom diskussion med berörda parter. Efter det ritas några detaljerade versioner av de bästa förslagen upp, vilka sedan är grunden för kraftanalyserna. Analyserna visar var de högsta spänningarna befinner sig och var den svaga länken i konstruktionen är. Avgränsningar inom arbetet är att endast en statisk dragkraft appliceras på modellerna under analyserna och ej någon dynamisk kraft. Ytterligare en avgränsning är att vid kraft/spänningsanalyserna undersöks endast en del av fläkten, som motsvarar ett fläktblad som är fäst vid en rigid del av ringen. Resultatet visar att det endast är i några få punkter och områden som kraftansträngningen blir för höga i principkonstruktionerna för det valda materialet. / The diploma work is about producing some construction proposal for axial fans with fixed adjustable blades for FläktWoods. They are large industrial fans with a diameter between one and five meters. Which is used to, among other things, transport air to mines and for the cooling in power plants. It’s only some proposal that shall be produced and not a finished product, the purpose is mainly about giving the design engineers at FläktWoods a new way to look at the problem. There are two different parts that are under consideration, the way the blade is mounted to the impeller and the construction off a new impeller. The course of action is to from the discussion of the problem produce some proposals that will be evaluated, the best of the proposals will go on to the next step. The evaluation will be done with help of an assessment of solution variants and through discussions with the concerned parties. The next step is to produce some models with more details of the best proposals, this models will be the foundation for the force/stress analysis. The analysis shows where the highest stresses are located and where the weakest part of the proposals. Delimitations within the diploma work is that only a static force will be used during the analysis, and no dynamic force. Another delimitation is that during the force/stress analysis only a part of the fan will be examined, that corresponds to one fan blade that is mounted to a rigid part of the impeller. The result shows that there is only a few point and areas where the forces/stresses are to large in the proposals, for the used material.

<p>Examensarbetet går ut på att frambringa några principkonstruktioner till axialfläktar med fasta inställbara skovlar åt</p><p>FläktWoods. Fläktarna det rör sig om är stora industrifläktar med en diameter mellan en och fem meter, som används för att</p><p>till exempel transportera ner luft i gruvor. Endast förslag till principkonstruktioner tas fram och ej en färdig produkt, syftet</p><p>med rapporten är i första hand att ge FläktWoods konstruktörer ett annat synsätt på problemet. Två olika delar av fläkten</p><p>undersöks, dels fästet av skoveln på hjulet, dels själva hjulet i sig. Tillvägagångssättet är att från formulerat problem tas</p><p>först några förslag fram, de utvärderas sedan och de bästa går vidare till nästa steg. Utvärderingen sker med hjälp av</p><p>produktförslagsdiagram samt genom diskussion med berörda parter. Efter det ritas några detaljerade versioner av de bästa</p><p>förslagen upp, vilka sedan är grunden för kraftanalyserna. Analyserna visar var de högsta spänningarna befinner sig och var</p><p>den svaga länken i konstruktionen är.</p><p>Avgränsningar inom arbetet är att endast en statisk dragkraft appliceras på modellerna under analyserna och ej någon</p><p>dynamisk kraft. Ytterligare en avgränsning är att vid kraft/spänningsanalyserna undersöks endast en del av fläkten, som</p><p>motsvarar ett fläktblad som är fäst vid en rigid del av ringen.</p><p>Resultatet visar att det endast är i några få punkter och områden som kraftansträngningen blir för höga i</p><p>principkonstruktionerna för det valda materialet.</p> / <p>The diploma work is about producing some construction proposal for axial fans with fixed adjustable blades for</p><p>FläktWoods. They are large industrial fans with a diameter between one and five meters. Which is used to, among other</p><p>things, transport air to mines and for the cooling in power plants. It’s only some proposal that shall be produced and not a</p><p>finished product, the purpose is mainly about giving the design engineers at FläktWoods a new way to look at the problem.</p><p>There are two different parts that are under consideration, the way the blade is mounted to the impeller and the construction</p><p>off a new impeller. The course of action is to from the discussion of the problem produce some proposals that will be</p><p>evaluated, the best of the proposals will go on to the next step.</p><p>The evaluation will be done with help of an assessment of solution variants and through discussions with the concerned</p><p>parties. The next step is to produce some models with more details of the best proposals, this models will be the foundation</p><p>for the force/stress analysis. The analysis shows where the highest stresses are located and where the weakest part of the</p><p>proposals.</p><p>Delimitations within the diploma work is that only a static force will be used during the analysis, and no dynamic force.</p><p>Another delimitation is that during the force/stress analysis only a part of the fan will be examined, that corresponds to one</p><p>fan blade that is mounted to a rigid part of the impeller.</p><p>The result shows that there is only a few point and areas where the forces/stresses are to large in the proposals, for the used</p><p>material.</p>

Outdoor heating, ventilating, and air-conditioning (HVAC) units emit a significant amount of noise, which may lead to poor sound quality and a perceived low product quality. It is the job of the noise control engineer to reduce the undesired noise and improve the sound quality of the outdoor HVAC unit to decrease consumer annoyance. There is great interest in developing a detailed and accurate acoustic model of the outdoor HVAC unit so that the sound of the outdoor HVAC unit can be listened to before the unit is constructed. Having an acoustic model which can synthesize sounds allows the noise control engineer to evaluate and improve the sound quality of the outdoor HVAC unit during the design process, without the need for extensive prototyping. Acoustical holography methods will be used to identify and localize noise due to the fan, and other significant noise sources, to visualize the sound field. In the current study, an acoustic model is described which can be used to model the noise due to structural radiation and vortex shedding of the outdoor HVAC unit’s rotating fan blades, one of the top contributors to the unit’s overall noise level. This moving source model simulates the Doppler effect which occurs when the blade moves towards and away from a receiver. The results from this moving source model is shown for different source signals, including sinusoidal, bandpass random, repeating random, and sinusoidal with time-varying frequency source signals. The parameters of this moving source model will be optimized to reproduce the experimental results, including the power spectral densities, tonal power component, and auralizations.