The emission of soot particles from aircraft jet engines is relevant due to their impact on contrail formation and local air quality in airport areas. The reduction of particle emission may be achieved by changes in jet engine design. This, however, will only affect new aircraft. Previous studies have shown that the use of alternative jet fuels feature a co-beneficial reduction of soot emission beside an improved carbon footprint. In the present study, a CFM56-5C4 engine was operated on a test rig with three different fuel types: one reference kerosene, a catalytic hydrothermolysis jet fuel (Readijet) and an unblended alcohol-to-jet (ATJ) fuel. Due to the absence of aromatics in the ATJ fuel, ASTM jet fuel requirements are not met, but the use of this fuel led to a reduction of 70% in particle mass compared to the reference fuel. The ReadiJet fuel has higher aromatic content, lower fuel hydrogen content and, thus, an increase in particle emission was observed. For the present engine, the highest soot reductions were observed at lower power settings. In accordance to previous studies, the soot emission showed a good correlation to the hydrogen content of the fuels and the emission reduction matches the estimations of the imFOX model. In order to compare test rig studies to field studies, transient processes must be considered because they govern takeoff conditions. Four experiments with different transient thrust patterns were performed on the test rig with regular Jet A-1. If the thrust changes were not very rapid (e.g. 5 s to ~90% thrust) the results could be reproduced with a set of pseudo-stationary processes to a sufficient extend. This emphasizes the relevance of test-rig studies for real in-field measurements and local air quality studies.

Erosive damage done to jet engine compressor blading by solid particles has a negative influence on the compressor aerodynamic properties and hence decreases performance. The erosive change of shape has been investigated in a multitude of experiments ranging from eroding flat plates to eroding full engines. The basic challenge to transfer the results from very simple tests to real life erosion remains. Up to date measurement techniques today allow closing this gap. The necessary experimental and analytical steps are shown. The erosion resistance of Ti–6Al–4V at realistic flow conditions with fluid velocities ranging from 200 to 400 m/s is used. The erodent used was quartz sand with a size distribution corresponding to standardized Arizona Test Dust A3 (1–120 μm). Flat plates out of Ti–6Al–4V were eroded at different impingement angles. The particle velocities and sizes were investigated using a high-speed laser shadowgraphy technique. A dimensional analysis was carried out to obtain nondimensional parameters suitable for describing erosion. Different averaging methods of the particle velocity were examined in order to identify a representative particle velocity. Compared to the fluid velocity and the mean particle velocity, the energy averaged particle velocity is found to be the best representation of the erosiveness of a particle stream. The correlations derived from the dimensional analysis are capable of precisely predicting erosion rates for different rig operating points (OPs). The results can be applied to the methodology published by Schrade et al. (2015, “Experimental and Numerical Investigation of Erosive Change of Shape for High-Pressure Compressors,” ASME Paper No. GT2015-42061).

A methodology for improving the quality of high-lift-system performance prediction within a multidisciplinary conceptual design process is presented. The high-lift-system geometry is explicitly modeled and a multiple-lifting-line method is used to compute its aerodynamic characteristics. Computation times are acceptable for use in a conceptual design process. The results for several test cases show good agreement with wind-tunnel and/or high-fidelity numerical data. In addition, the method allows for further enhancement by using nonlinear airfoil polars for interpolation, improving drag prediction, and introducing some degree of nonlinear aerodynamic behavior.

The present study deals with the influence of geometrically degraded transonic engine fan blades on the fan’s aerodynamic behavior. The study is composed of three phases; the first consists of 3D simulations to point out changes in the performance parameters caused by blade degradations. In the second phase, 2D optimizations are carried out to determine the potential of redesigning the blade and in the third phase, measurements on a transonic cascade are used to experimentally verify the numeric results. During engine operation as well as maintenance processes, geometric variations of the fan blades, and especially of the blades’ leading edges, are observed. They mainly originate from the ambient conditions under which the engine is operated. Though the deformations of the blade differ widely, several typical degradation types can be identified. In advance of the study, these degradation types have been systematized and simplified models representing different degrees of degradation have been built. In the first phase, the models are aerodynamically analyzed by means of 3D simulations. A high influence on the performance parameters is found for a fan blade exposed to long-term erosion. The model’s characteristics are a blunt leading edge and a reduced chord length. In contrast, the performance parameters of a model representing a re-contoured blade (reduced chord length but reshaped leading edge) are shown to be similar to those of a new fan blade. This leads to the conclusion that an eroded blade may offer almost the initial performance parameters as long as the leading edge is well reshaped. Since the model of the long-term eroded blade shows great changes in the fan’s performance and the best optimization potential, this has been chosen for the further analysis in the following phases. In the second phase, 2D optimizations are applied to three airfoil sections at different heights of the blade. The parameterization used is limited to a small area of the leading edge; the shape of the rest of the blade is kept constant. The optimizations lead to loss reduction and demonstrate the potential of the optimization process. The third phase is carried out in the Transonic Cascade Wind Tunnel of the Institute of Propulsion Technology in Cologne. As the transonic part of the fan blade is the most sensitive to geometric changes, a transonic airfoil with long-term erosion has been chosen. During the tests, the following measurement techniques are applied: Static pressure probes to determine the Mach number distribution, a 3-hole probe to detect exit angle and loss distribution, Schlieren photographs and PIV-measurements to locate the shock system, the L2F method to measure the cascade inflow angle and to resolve the boundary layer distribution and Liquid crystal measurements to observe transition activities. The full analysis of the measurements with PIV, L2F and Liquid Crystals are still in progress, but the evaluation of the loss polar and the Schlieren photographs show increased losses for the degraded blade and a good match with the numeric results.

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Erosive damage done to jet engine compressor blading by solid particles has a negative influence on the compressor aerodynamic properties and hence decreases performance. The erosive change of shape has been investigated in a multitude of experiments ranging from eroding flat plates to eroding full engines. The basic challenge to transfer the results from very simple tests to real life erosion remains. Up to date measurement techniques today allow closing this gap. The necessary experimental and analytical steps are shown. The erosion resistance of Ti-6Al-4V at realistic flow conditions with fluid velocities ranging from 200 to 400 m/s is used. The erodent used was quartz sand with a size distribution corresponding to standardized Arizona Test Dust A3 (1 to 120 μm). Flat plates out of Ti-6Al-4V were eroded at different impingement angles. The particle velocities and sizes were investigated using a high speed laser shadowgraphy technique. A dimensional analysis was carried out to obtain nondimensional parameters suitable for describing erosion. Different averaging methods of the particle velocity were examined in order to identify a representative particle velocity. Compared to the fluid velocity and the mean particle velocity, the energy averaged particle velocity is found to be the best representation of the erosiveness of a particle stream. The correlations derived from the dimensional analysis are capable of precisely predicting erosion rates for different rig operating points. The results can be applied to the methodology published in [1].

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 Universität 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.

Aircraft engine maintenance is performed on an on-condition basis. Monitoring the engine condition during operation is important to provide an efficient maintenance. Engine Condition Monitoring has thus become a standard procedure during operation. However, one of the most important parameters, the engine thrust, is not directly measured 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. This paper describes the development and quality assessment of a system for direct engine thrust measurement during the normal engine operation. The system was designed, calibrated and validated with engine test runs. After the necessary certification of the whole system a flight test campaign to validate the system, when installed on an aircraft, was started. In the presented work an assessment of the quality of measured data from the first period of the ongoing flight test is presented.