Martin Plohr

Bio: Martin Plohr is an academic researcher from German Aerospace Center. The author has contributed to research in topics: Conceptual design & Range (aeronautics). The author has an hindex of 7, co-authored 21 publications receiving 223 citations.

Experimental Test of the Influence of Propulsion Efficiency on Contrail Formation

Abstract: According to a previously established thermodynamic theory, contrails are expected to form at a threshold temperature that increases with the overall efficiency of the aircraft propulsion. As a consequence, aircraft with modern engines, with higher overall efficiency, cause contrails over a larger range of cruise altitudes. To validate this theory, an experiment was performed in which contrail formation was observed behind two different four-engine jet aircraft with different engines flying wing by wing. Photographs document the existence of an altitude range in which the aircraft with high engine efficiency causes contrails whereas the other aircraft with lower engine efficiency causes none. For overall efficiencies of 0.23 and 0.31 and an ambient temperature lapse rate of 12 K km -1 , the observed altitude difference is 80 m. This value would be larger (200 m) in a standard atmosphere with smaller temperature lapse rate (6.5 K km -1 ) In a standard atmosphere, an increase of overall efficiency from 0.3 to 0.5, which may be reached for future aircraft, would cause contrails at about 700 m lower altitude

Climate impact assessment of varying cruise flight altitudes applying the CATS simulation approach

Abstract: The present paper describes a comprehensive assessment and modelling approach that was developed in the DLR project Climate compatible Air Transport System (CATS) with the goal to analyze different options to reduce the climate impact of aviation. The CATS simulation chain is applied to assess the climate impact reduction potential (via CO2, contrail-cirrus, H2O, NOx, ozone, methane, primary mode ozone) for the world fleet of a representative long-range aircraft operated on a global route network in the year 2006. The average temperature response (ATR) and the direct operating costs (DOC) are calculated for flights with varying cruise flight altitudes and speeds. The obtained results are expressed as relative changes with respect to the minimum DOC trajectory and assessed as cost-benefit ratio (ATR vs. DOC). The results are highlighted for a single route and transferred to the global route network, showing a large potential to reduce the climate impact of aviation for small to moderate increments on costs.

System analysis of turbo-electric and hybrid-electric propulsion systems on a regional aircraft

Abstract: The increasing environmental requirements in the air transport sector pose great challenges to the aviation industry and are key drivers for innovation. Besides various approaches for increasing the efficiency of conventional gas turbine engines, electric propulsion systems have moved into the focus of aviation research. The first electric concepts are already in service in general aviation. This study analyses the potentials of electric and turbo hybrid propulsion systems for commercial aviation. Its purpose is to compare various architectures of electrical powertrains with a conventional turboprop on a regional aircraft, similar to the ATR 72, on engine and flight mission levels. The considered architectures include a turbo-electric (power controlled and direct driven), hybrid-electric (serial and parallel) and a pure electric concept. Their system weights are determined using today’s technology assumptions. With the help of performance models and flight mission calculations the impact on fuel consumption, CO emissions and aircraft performance is evaluated.

Estimates of the climate impact of future small-scale supersonic transport aircraft – results from the HISAC EU-project

Abstract: The climate impacts of three fleets of supersonic small-scale transport aircraft (S4TA) are simulated. Based on characteristic aircraft parameters, which were developed within the EU-project HISAC, emissions along geographically representative trajectories are calculated and in addition the resulting changes in the atmospheric composition (carbon dioxide, ozone layer, water vapour) and climate (near surface global mean temperature) are deduced. We assume a fleet development with an entry in service in 2015, a full fleet in 2050. The results show a temperature increase of 0·08mK (0·07-0·10mK) with only small but statistically significant variations between the configurations, leading to a minimum climate impact for a weight optimised and hence lower flying aircraft. A climate impact ratio of 3·0 ± 0·4 between a S4TA and its subsonic counterpart is calculated, which is considerable less than for previous supersonic fleets because of a lower flight altitude, leading to smaller water vapour impacts.

Historical and future trends in aircraft performance, cost, and emissions

Abstract: ▪ Abstract The interdependency of aircraft technological systems, the global reach of the aviation transport industry, and the uncertainty surrounding potential atmospheric effects have made defining the relationship between aviation and environmental impact an arduous task. Air travel continues to experience the fastest growth of all modes of transport, and although the energy intensity of the aviation transport system continues to decline, fuel use and total emissions have steadily risen. This trend, which represents a conflict between growth and environmental impact, has motivated the aircraft manufacturing and airline industries, the scientific community, and governmental bodies to consider what pace of emissions reduction is acceptable. This paper analyzes the historical influence of aircraft performance on cost to examine the potential pace of future efficiency improvements and emissions reduction. Technological and operational influences on aircraft energy intensity are quantified and correlated wi...

Formation and radiative forcing of contrail cirrus

Abstract: Aircraft-produced contrail cirrus clouds contribute to anthropogenic climate change. Observational data sets and modelling approaches have become available that clarify formation pathways close to the source aircraft and lead to estimates of the global distribution of their microphysical and optical properties. While contrail cirrus enhance the impact of natural clouds on climate, uncertainties remain regarding their properties and lifecycle. Progress in representing aircraft emissions, contrail cirrus and natural cirrus in global climate models together with tighter constraints on the sensitivity of the climate system will help judge efficiencies of and trade-offs between mitigation options.

On the Radiative Forcing by Contrails

Abstract: A parametric study of the instantaneous radiative impact of contrails is presented using three different radiative transfer models for a series of model atmospheres and cloud parameters. Contrails are treated as geometrically and optically thin plane parallel homogeneous cirrus layers in a static atmosphere. The ice water content is varied as a function of ambient temperature. The model atmospheres include tropical, mid-latitude, and subarctic summer and winter atmospheres. Optically thin contrails cause a positive net forcing at top of the atmosphere. At the surface the radiative forcing is negative during daytime. The forcing increases with the optical depth and the amount of contrail cover. At the top of the atmosphere, a mean contrail cover of 0.1% with average optical depth of 0.2 to 0.5 causes about 0.01 to 0.03 Wm−2 daily mean instantaneous radiative forcing. Contrails cool the surface during the day and heat the surface during the night, and hence reduce the daily temperature amplitude. The net effect depends strongly on the daily variation of contrail cloud cover. The indirect radiative forcing due to particle changes in natural cirrus clouds may be of the same magnitude as the direct one due to additional cover.