Dynamic Spin Rig Test Systems
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IntroductionDynamic Spin™ Rigs (DSR) represent the “next generation” of spin testing equipment designed to carryout testing protocols under more realistic engine conditions, resulting in more relevant test data. Dynamic Spin Rigs are capable of performing traditional spin tests such as, overspeed, burst, and low cycle fatigue (LCF) tests, as well as Advanced Spin™ Testing and Dynamic Spin Testing protocols (described below). This new type of test equipment offers a means to conduct engine cell type tests earlier in engine development programs, which helps reduce costly engineering redesigns and lowers the risk of in service component failure. A brief overview of the test capability of Dynamic Spin Rigs is outlined below: Dynamic Spin™ TestingDynamic Spin Rig capabilities include:
Figure 1 - Dynamic Spin Rig Chamber Managing resonant vibration of bladed jet engine rotors represents a technical challenge for engine programs. During operation, engine blades are subjected to bending and twisting modes, caused by resonant vibration, resulting in blade failure in extreme cases. To address this issue, blade, disk, and stator geometry can be modified, and dampers introduced to minimize vibration amplitudes. Dynamic Spin Rigs simulate engine static loads (centrifugal stress), thermal stresses (elevated temperature thermal gradients), and excitation forces. During testing, blades and dampers undergo actual centrifugal stress at operational speeds, replicating engine static loads. Thermal stresses can also be applied by testing at engine operating temperatures. The excitation force used to produce resonant blade vibrations simulates the impact force resulting from blade/stator passage, causing blade distortion. High frequency modes can also be excited with engine orders (EO) of up to 100. Dynamic Spin Rigs can carry out the following tests to evaluate the performance of complete blade/damper/rotor stage assemblies.
Figure 2 Blade CharacterizationCharacterization of the resonant vibration modes and amplitudes of engine blades is critical for design optimization. Slow resonance crossing enables calculation of blade amplification factors for measuring the severity of various modes and the risk they present.
Figure 3 Damper EvaluationDynamic Spin Rigs provide a convenient way to evaluate the performance of damper designs installed in “engine ready” hardware. Complete rotors can be assembled with dampers installed and blade resonant vibrations excited for critical modes to determine the effect of various dampers designs on vibration amplitudes. DSRs are very flexible and several different damper designs or EO configurations can be tested during the same day, with little down time between tests.
Figure 4a - 1F Mode Damper Evaluation
Figure 4b - 1T Mode Damper Evaluation High Cycle FatigueAnother important capability of Dynamic Spin Rigs is performing fatigue life evaluation. Speed can be held at resonance for long periods of time and blade cracking can be detected to measure time to crack. Resonance dwell testing is important for measuring the reduction in fatigue life that results from various kinds of blade damage from foreign object impacts.
Figure 5 Advanced Spin™ TestingAdvanced spin testing incorporates non-traditional tests which either include variation of standard test parameters or provide additional data. Dynamic Spin Rigs include the capability to run advanced spin tests, including: Radial Growth TestingTest Devices’ Dynamic Spin Rigs include the capability to measure the diametrical or radial growth of high speed rotating components in real time. Because the centrifugal forces on rotating components grow alarmingly fast as rotational speeds increase, measuring the growth at speed can be very valuable. Test Devices has used its radial growth testing during several Federal Aviation Administration overspeed/burst certification tests with great success. Growth data taken at the speed at which a component goes plastic can be very important for 3D model verification.
Figure 6 Thermal Gradient TestingDSRs provide a thermal environment which more accurately simulates the engine stress environment by including both the mechanical (centrifugal) and thermal stresses. Traditional spin testing only provide for component testing at either ambient or isothermal elevated temperatures. While isothermal elevated temperatures add an additional thermal stress component to the mechanical stress (centrifugal force), it does not apply the correct stress field across the component. Test Devices’ Dynamic Spin Rigs include the capability to perform overspeed, burst and LCF testing with radial and axial temperature gradients.
Figure 7 Standard Spin TestingStandard spin testing requirements are those typically satisfied by traditional spin testing equipment, and include overspeed, burst, and low cycle fatigue testing. Dynamic Spin Rigs offer additional capability to provide customers with additional valuable test data from these routine test protocols. The additional value is outlined below. Overspeed/Burst TestingDSRs allow for the capture of valuable test data from burst events by recording with high speed camera equipment. The safety view ports installed on the bottom of the DSR provide a clear view for the high speed camera, mounted underneath the test chamber, a clear view of the complete rotating assembly.
Figure 8 Low Cycle Fatigue (LCF) TestingTest Devices spin test systems have long been recognized for their ability to perform rapid cycling with high power density drives, resulting in shorter schedules for LCF testing programs. DSRs include this capability as well as the ability to simulate mission profiles by dwelling at multiple speeds, for set periods of time, during a single cycle. Additionally, the DSR includes very accurate speed control system to satisfy tightly toleranced speed requirements.
Figure 9 Crack DetectionA cracked rotor, with pristine crack surfaces, is much more valuable for analysis purposes than component shrapnel which have impacted the spin chamber containment. Because of the advantage of preserving cracked test components, each DSR includes Test Devices’ patented crack detection monitoring system. The system compares the change in the vibration vector for each cycle to all of the previous completed cycles, in order to detect the initiation and growth of cracks. Test Devices has halted many LCF tests prior to component failure due to cracks detected by this unique system, and preserved numerous customer components.
Figure 10 Strain Survey TestingTest data recorded during strain survey spin testing is often used to correlate 3D design models, and thereby reduce in component design. Strain gages mounted to the rotating assembly, in areas of peak stress, record strain throughout the spin test, up to component failure.
Figure 11 High Speed BalancingWhen balancing of a rotating assembly on a standard balance machine becomes impractical, or when high speed balancing is required, TDI’s DSRs allow the operator to precisely measure the unbalance of the rotating assembly at speed in the spin chamber. Test Devices often uses its high speed balancing system to precisely balance large, complex, test components prior to carrying out spin test protocols. Rather than having large bladed rotor assemblies rotating at high speed on standard balance equipment on the shop floor, the rotor is safely contained within the robust spin chamber of a DSR For additional information about the capability and value of dynamic spin rigs, please contact one of our sales engineers at: |
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