Detlev Wulff

Sensitivity Analysis of a Highly Loaded Turboprop S-Duct Intake by CFD Methods

S-duct intake of a high power turboprop with unconventional integration types requires additional design objectives rather than a basic sizing, considering the propeller-wingnacelle interaction effects. Before the conceptual integration process, sensitivity analysis based on the intake performance has been done to identify the limitations on the S-duct geometry using computational methods. The flow simulations were done on an isolated, uninstalled S-duct intake, excluding propeller effects and particle separator, for an initial specification in advance of the actual sizing. The effects of fundamental geometric features, as the intake aspect ratio, duct lengths and spread angle, were investigated on the flow quality through the aerodynamic interface plane (AIP), quantified by total pressure recovery and distortion. The results show a preference to longer S-ducts whereas the shorter front and end ducts are observed to be advantegous for their higher recovery capacities with lower distortion levels.

Increasing reliability using FEM–CFD

Boiler feed water pumps in power plants are typically subjected to extreme stresses during operation, and are liable to damage as a result. In this article, Sohail Ahmed, Reinhard Leithner, Gunter Kosyna and Detlev Wulff of the Technical University of Braunschweig explore the applicability of coupled FEM–CFD simulations as the potential basis for a condition monitoring tool to improve the lifetime and performance of these huge pumps.

S-Duct Intake Configuration Sensitivity of a Highly Loaded Turboprop by CFD Methods

Highly-loaded turboprop intake was investigated for two different shaft connection types to assess the configuration sensitivity on performance. Turboprop intakes inherently have S-shape to bend around the gearbox, which have significant effects on the flow. Previous geometric sensitivity analysis on uninstalled, isolated single scoop S-ducts with shaft penetration showed higher recovery and lower distortion trends for long intakes with shorter ducts. The major pressure loss was observed over the bore due to the penetrating shaft. It is expected that changing the configuration to wrap-around will overcome the loss introduced by flow around the bore. The two configurations were compared by varying the S-duct curvatures using computational methods. The results showed an increase in recovery with lower total pressure distortion levels for wrap-around configuration of the same sizes. The gain in the recovery by the configuration change was observed to be similar to the gain when the ducts were shortened. However, wrap-around S-duct suffered from higher swirl distortion than shaft penetration of the same size but these were observed to be lower than the shaft penetration type with short ducts. Distortion intensities showed opposite trends for the two configurations, with wrap-around producing low distortion in circumferential whereas high in radial direction. The results will be used as the basis for the turboprop intake design and its over-the-wing integration on the high-lift aircraft.Copyright

Development and Validation of an On-Wing Engine Thrust Measurement System

Maintenance on aircraft engines is usually performed on an on-condition basis. Monitoring the engine condition during operation is an important prerequisite to provide efficient maintenance. Engine Condition Monitoring (ECM) has thus become a standard procedure during operation. One of the most important parameters, the engine thrust, is not directly measured, however, and can therefore not be monitored, which makes it difficult to distinguish whether deteriorating trends e.g. in fuel comsumption must be attributed to the engine (e.g. due to thermodynamic wear) or to the aircraft (e.g. due to increased drag). Being able to make this distinction would improve troubleshooting and maintenance planning and thus help to reduce the cost of ownership of an aircraft. As part of the research project APOSEM (Advanced Prediction of Severity effects on Engine Maintenance), Lufthansa Technik (LHT) and the Institute of Jet Propulsion and Turbomachinery of Technische Universitat Braunschweig develop a method for direct measurement of engine thrust during the operation. In this paper, the design process of the On-Wing (OW) Measurement System is presented, including the validation in labratory tests, the mechanical and thermal calibration as well as the final ground test during an engine test run at LHT test cell and the work on the flight test certification.© 2017 ASME

Aerodynamic Performance Comparison of High Power Turboprop S-Duct Intake on Channel Wing at Varying Azimuth

S-duct intake component for a highly loaded turboprop engine was investigated considering its installation on a channel wing of an active high-lift aircraft using computational fluid dynamics. The objective is to observe the interaction effects of the propeller-nacellewing on the S-duct intake aerodynamics, especially when the intake is positioned at different azimuth angles with respect to rotation axis. Single scoop wrap-around type S-duct was integrated into a representative nacelle body. The propeller was modeled as an actuator disc for the slipstream effects. Steady-state Reynolds-averaged Navier-Stokes simulations were run using negative Spalart-Allmaras turbulence model. Although the results showed that the reference S-duct position at Φ= 270° had the relatively higher recovery than the other variations, significant improvements in total pressure distortion and intensities were achieved at Φ= 0° and 90° positions. Up to 3% decrease in swirl coefficient levels was observed when the wrap-around S-duct was positioned at Φ = 90° in comparison to reference position.

Links between Main Frequencies of Established Rotating Stall and Rotational Frequencies and/or Blade Passing Frequencies

The ratios between the main frequency of rotating stall and rotational frequency may be considered in the form of exact ratios of small natural numbers if the pressure signals in compressors during rotating stall include the rotor rotation frequency component. During rotating stall in compressors with good rotor balancing (with absence of the rotational frequency component in the frequency characteristics of pressure signals), these ratios between the main frequency of rotating stall and rotational frequency are or are not in the form of ratios of small natural numbers. The experimentally received characteristics of power spectral density of pressure signals also show the presence of components with combinations of blade passing frequency and different harmonics of main rotating stall frequency.

Controlling and Monitoring Tool for Reliable and Optimal Operation of Boiler Feed Water Pump

Challenges of operational safety and reliability as well as optimal operation of boiler feed water pump define the requirement of a competent and efficient controlling as well as monitoring tool. The monitoring module of this tool should effectively record the life time consumption of both casings and rotors and also monitor the small gaps between casings and rotors. The controlling module of this tool should ensure the safety and reliability during the operation of the boiler feed water pump based on the feed back from the monitoring module and also should take appropriate actions in order to ensure that the pump operates within the allowable design limits. This tool could enable operators to start up the boiler feed water pump without any unnecessary waiting period and change load rapidly without causing any damage or any life consumption rate getting increased. In this research paper, the methodology of such a tool is explained, having monitoring as well as controlling modules. Similar monitoring and controlling tools, as presented in the paper, can be applied to all turbomachines e.g. gas turbines, steam turbines, compressors etc.Copyright