- 著者
- Jens Achenbach Marcus Fischer Bastian Lehrheuer Marco Guenther Stefan Pischinger
- 出版者
- The Japan Society of Mechanical Engineers
- 雑誌
- The international symposium on diagnostics and modeling of combustion in internal combustion engines (ISSN:24242918)
- 巻号頁・発行日
- pp.A4-1, 2022 (Released:2023-01-25)
- 被引用文献数
- 2
High efficiency gasoline combustion engines with up to 50 % indicated efficiency are the target of current research work. To reach this goal, it’s essential to reduce all the combustion engine losses as much as possible. One major loss, with about 30 % of the total fuel energy, is the wall heat transfer loss. To reduce this loss, one solution is a temperature swing insulation, which is characterized by a low thermal conductivity and at the same time a low volumetric heat capacity. In order to analyze the thermal efficiency potential of different insulation materials, a thermal insulation model for one-dimensional engine process simulations has been developed and is presented in this paper. The insulation is discretized by a thermal node model and is coupled to an engine process simulation using the simulation tool GT-Power. The heat transfer and temperature swing behavior of the thermal insulation model is validated against 3D-CFD engine cycle simulations. A predictive detailed chemistry combustion model is used in 3D-CFD simulations to evaluate the influence of thermal insulations on the knocking tendency. Two different thermal insulation materials are investigated using the developed simulation model. One is yttria stabilized zirconia (YSZ) as a common thermal sprayed coating. The second material is produced by an electrolytic oxidation of the piston surface (anodizing). With thermal piston insulation, there is only a small increase in thermal efficiency in the range of 0.2 % to 0.6 % possible with both materials, whereby the potential increases at low speeds and medium loads. The reason can be found in the relative heat losses, which increases with a constant center of combustion and increasing load. An efficiency loss analysis shows that the exhaust losses increase by about two third of the reduced heat losses. Due to its lower volumetric heat capacity and similar heat conductivity, the anodized piston surface shows a thermal efficiency advantage compared to YSZ. The simulation results are finally validated by measurements conducted with a single-cylinder research engine for an YSZ coated piston surface as well as a hard anodized piston surface.
- 著者
- Sabine Fenk Marcus Fischer Christina Strack Gerd Schmitz Thomas Loew Claas Lahmann Andrea Baessler
- 出版者
- 一般社団法人 インターナショナル・ハート・ジャーナル刊行会
- 雑誌
- International Heart Journal (ISSN:13492365)
- 巻号頁・発行日
- vol.56, no.2, pp.196-202, 2015 (Released:2015-03-20)
- 参考文献数
- 43
- 被引用文献数
- 9 36
Obesity and the metabolic syndrome (MetS) are risk factors for left ventricular diastolic dysfunction (LVDD). However, little is known about the impact of successful weight reduction (WR) on diastolic function and physical performance.Obese subjects (øBMI 40.2 ± 8.6 kg/m2) underwent a 1-year WR program comprising diet and lifestyle components. Echocardiography and exercise capacity (6-minute walk) were performed at baseline and after 1 year. The distribution of weight reduction was split at the sample median and subjects were dichotomized in “successful WR” (% WR ≥ median, corresponding to a weight loss of 8%) and “failed-WR” (% WR < median).From a total of 188 obese subjects, 71 had LVDD at baseline. Obese patients with successful WR improved their MetS alterations, including fasting glucose, insulin, lipids, adipokines, blood pressure levels, and epicardial fat thickness. The same was not true for obesity with failed WR. Subjects with successful WR demonstrated significant improvement in echocardiographic LVDD parameters (median [interquartile range]): Δe’ (2,5 [-1.0, 4.7], P < 0.01), Δe’/a’ (0.34 [0.07, 079], P < 0.01), ΔE/e’ (-1.14 [-2.72, -0.54], P < 0.05), ΔE/A (0.08 [-0.04, 0.26], P < 0.05), ΔArd-Ad (-28 [-54, -4], P < 0.01), and 6-minute walk distance (65 [19, 135], P < 0.01). Improvement of ≥ 2 LVDD criteria was accomplished in 30% of subjects with WR versus 10% without (P = 0.009). Using multivariable regression analysis, reduction of epicardial fat thickness was particularly predictive for the improvement of diastolic function.In summary, in severe obesity, successful long-term WR was associated with improved LV diastolic function and exercise capacity.