Heat transfer technology for internal passages of air-cooled blades for heavy-duty gas turbines.

The present review paper, although far from being complete, aims to give an overview about the present state of the art in the field of heat transfer technology for internal cooling of gas turbine blades. After showing some typical modern cooled blades, the different methods to enhance heat transfer in the internal passages of air-cooled blades are discussed. The complicated flows occurring in bends are described in detail, because of their increasing importance for modern cooling designs. A short review about testing of cooling design elements is given, showing the interaction of the different cooling features as well. The special focus of the present review has been put on the cooling of blades for heavy-duty gas turbines, which show several differences compared to aero-engine blades.

Prediction of pressure loss and heat transfer in internal cooling passages.

This paper reports CFD-simulations of the turbulent flow, pressure loss and heat transfer occurring in ribbed passages. The channel section is rectangular, with an aspect ratio of 2.04. Ribs are square cross-section, their height is 10% of the channel height, and their inclination is varied from 90 degrees to 33 degrees. Reynolds number is 30,000. Three turbulence models (k-epsilon wall functions and 2-layer, V2F) are used and compared to the experimental data of Cho et al. All three models accurately predict the pressure losses due to the ribs and the qualitative heat transfer distribution on the ribbed wall. However, only the V2F model can accurately reproduce the absolute heat transfer levels, this at all inclination angles. The correlation developed by Han and co-workers for smaller rib-heights under-predicts the friction factor and wall heat transfer level on the current configuration. This shows the danger of using a correlation outside of its application range.

The structure and thermotropic phase behaviour of dipalmitoylphosphatidylcholine codispersed with a branched-chain phosphatidylcholine.

The structure and thermotropic phase behaviour of a fully hydrated binary mixture of dipalmitoylphosphatidylcholine and a branched-chain phosphatidylcholine, 1, 2-di(4-dodecyl-palmitoyl)-sn-glycero-3-phosphocholine, were examined using differential scanning calorimetry, synchrotron X-ray diffraction and freeze-fracture electron microscopy. The branched-chain lipid forms a nonlamellar phase when dispersed alone in aqueous medium. Mixed aqueous dispersions of the two phospholipids containing less than 33 mol% of the branched-chain lipid form lamellar phases over the whole temperature range were studied (4 degrees C to 60 degrees C). When present in proportions greater than 33 mol% it induces a hexagonal phase in mixed aqueous dispersions with dipalmitoylphosphatidylcholine at temperatures above the fluid phase transition. At temperatures below 35 degrees C a hexagonal phase coexists with a gel bilayer phase. The lamellar<-->nonlamellar transition can be explained satisfactorily on the basis of the shape of the molecule expressed in terms of headgroup and chain cross-sectional areas. At temperatures below 35 degrees C macroscopic phase separation of two gel phases takes place. Freeze-fracture electron microscopy revealed that one gel phase consists of bilayers with a highly regular, periodic superstructure (macro-ripples) whereas the other phase forms flat, planar bilayers. The macro-ripple phase appears to represent a relaxation structure required to adapt to the packing constraints imposed by the incorporation of the branched-chain lipid into the dipalmitoylphosphatidylcholine host bilayer. The data suggest that structural changes that take place on cooling the mixed dispersion below the lamellar<-->nonlamellar phase transition temperature cannot be adequately described using the molecular form concept. Instead it is necessary to take into account the detailed molecular form of the guest lipid as well as its physical properties.

Ripple phases induced by alpha-tocopherol in saturated diacylphosphatidylcholines.

The effect of alpha-tocopherol on the structure and phase behavior of dilauroyl-, dimyristoyl-, dipalmitoyl-, and distearoyl-phosphatidylcholines was examined using X-ray diffraction and freeze-fracture electron microscopic methods. A ripple phase was observed in all of the mixtures at temperatures well below the pretransition temperature of the corresponding pure phospholipid. Freeze-fracture studies indicated that with proportion of alpha-tocopherol less than 5 mol% a ripple phase with large periodicity (50-150 nm) predominated and with about 10 mol% alpha-tocopherol a ripple phase of periodicity about 16 nm was formed. With more than 10 mol% alpha-tocopherol planar bilayers tended to be formed. Partial phase diagrams of mixed aqueous dispersions of saturated phosphatidylcholines and alpha-tocopherol over temperature ranges about the gel to liquid-crystal phase boundary have been constructed. Alpha-tocopherol-enriched domains form ripple phases that coexist with regions of lamellar gel phase of the pure phospholipid in mixtures containing less than 10 mol% alpha-tocopherol. The presence of increasing amounts of alpha-tocopherol in the phospholipid causes an increase in the proportion of ripple phase at the expense of pure phospholipid bilayer indicating that the alpha-tocopherol-enriched domains might possess a defined stoichiometry of the two constituents.

Hydration of DMPC and DPPC at 4 degrees C produces a novel subgel phase with convex-concave bilayer curvatures.

Hydration of dimyristoyl- and dipalmitoylphosphatidylcholines at 4 degrees C results in the formation of a characteristic subgel phase designated Pcc. Examination of the phase by freeze-fracture electron microscopy shows convex-concave deformations of the planar bilayer which are of two types. A smaller type with a radius of curvature of about 20 nm predominates in DMPC, and a larger type with about 70 nm radii of curvatures dominates in DPPC. The Pcc phase can also be formed in samples hydrated at temperatures above the main phase transition if the dispersion is frozen slowly and subsequently incubated at 4 degrees C for several days. The subgel Pcc phase was distinguished from the subgel Lc phase by the temperature of transition, packing of the acyl chains on the basis of wide-angle X-ray diffraction, and 2H-NMR spectra characteristic of a 'solid-ordered' phase. Vibrational spectra of the carbonyl and phosphate regions are consistent with a partially reduced hydration state. The origin of the convex-concave bilayer deformation is believed to result from constraints imposed by limiting hydration of the headgroup and a frustration arising from the spontaneous curvature of both monolayers.

High-pressure freezing causes structural alterations in phospholipid model membranes.

The influence of high-pressure freezing (HPF) on the lipid arrangement in phospholipid model membranes has been investigated. Liposomes consisting of pure dipalmitoyl-phosphatidylcholine (DPPC) and of DPPC mixed with a branched-chain phosphocholine (1,2-di(4-dodecyl-palmitoyl)- sn-glycero-3-phosphocholine) have been analysed by freeze-fracture electron microscopy. The liposomes were frozen either by plunging into liquid propane or by HPF. The characteristic macroripple-phase of the two-component liposome system is drastically changed in its morphology when frozen under high-pressure conditions. The influence of ethanol which acts as pressure transfer medium was ruled out by control experiments. In contrast, no high-pressure alterations of the pure DPPC bilayer membrane have been observed. We assume that the modification of the binary system is due to a pressure-induced relaxation of a stressed and unstable lipid molecule packing configuration. HPF was performed with a newly designed sample holder, for using sandwiched copper platelets with the high-pressure freezing machine Balzers HPM010. The sandwich construction turned out to be superior to the original holder system with regard to freeze-fracturing of fluid samples. By inserting a spacer between the supports samples with a thickness of 20-100 microns can be high-pressure frozen. The sandwich holder is provided with a thermocouple to monitor cooling rates and allows exact sample temperature control. Despite a two-fold mass reduction compared to the original holder no HPF cooling rate improvement has been achieved (4000 degrees Cs-1). We conclude that the cooling process in high-pressure freezing is determined mainly by cryogen velocity.

The effect of sterols on structures formed in the gel/subgel phase state of dipalmitoylphosphatidylcholine bilayers.

The effect of cholesterol and lanosterol on the formation of structures in the gel/subgel phase of 1,2-dipalmitoylphosphatidylcholine was investigated using freeze-fracture electron microscopy and X-ray diffraction. Mixtures with up to 25 mol% sterol were analysed after annealing for between several days and some months at 4 degrees C. Bilayers of DPPC with 5 or 10 mol% sterol showed a domain structure in the gel state. There are rounded or lens-like and often inclined plates within less smooth either plane or striped bilayer areas. The stripes are formed by parallel lines separated by a distance of 30-60 nm. Parallel lines can be induced also in the less smooth but plane areas by warming up to 25 degrees C. X-ray diffraction showed two lamellar repeat spacings at 6.45 and 8.3 nm in both 5 and 10 mol% samples. The plates are interpreted as domains of (nearly) pure DPPC within the sterol containing bilayer. Stripes are present if the concentration of cholesterol is below a critical value (approx. 15 mol%). With time of incubation at 4 degrees C curved deformations appear in parts of the bilayers. Two main types are formed. The small type has a repeat distance of about 100 nm and the large type of about 400 nm. The curved deformations were progressively flattened by warming up to 25-32 degrees C with an accompanying reappearance of stripes but no plates. After prolonged annealing at 4 degrees C there is also the formation of regular ripples. It is concluded that in presence of 5 and 10 mol% sterol in bilayers of 1,2-dipalmitoy-phosphatidylcholine the immiscibility of gel phase and subgel phase changes during prolonged annealing at 4 degrees C. We assume a rearrangement of the molecules into a homogeneous phase state with liquid-ordered properties.

[Prenatal diagnosis of truncus arteriosus communis (type I) in diabetic pregnancy]. / Pränatale Diagnose eines Truncus arteriosus communis (Typ I) bei einer diabetischen Schwangerschaft.

Recently Ferencz et al. [6] using the datas of the Baltimore-Washington Infant Study found a predominance of double outlet righ ventricle and truncus arteriosus communis among the congenital heart diseases of newborns of diabetic mothers. This paper reports about the prenatal diagnosis of a truncus arteriosus communis Type I in a 23 year old pregnant with insulin-dependent diabetes mellitus (White B). The diagnosis was performed in the 25th week using Real-Time- and Color-Doppler-sonography. The important features in the prenatal differentialdiagnosis from a tetralogy of Fallot are explained. The optimal management of pregnancy, the delivery at a perinatal center with subsequent operative correcture could improve the prognosis of the newborn.

[Early detection of diabetes in pregnancy--a factor for reducing perinatal mortality and morbidity]. / Die Früherfassung des Gestationsdiabetes--ein Faktor zur Senkung der perinatalen Mortalität und Morbidität.

At present the main problem in gestational diabetes (GDM) is that only less than 10% of the pregnant diabetics could be diagnosed and accordingly treated. Analysing 101 cases of pregnant diabetics we refer to the incidence of peripartal and perinatal complications. The treatment with insulin was necessary to be applied on 70 of the patients (69.3%) in order to achieve normal glucose levels (between 3.3 and 6.6 mmol/l). If the metabolic complications are determined and treated in a later phase of pregnancy, there is a higher rate of complications (toxemias 29.7%, premature labor 21.8%, caesarean section 23.8%, perinatal mortality 2.9%, congenital anomalies 5.9% and the likelihood of large for gestational age babies 32.7%). Improvement of such results, which can be obtained in optimally treated insulin - dependent pregnants, is possible only by more early determination of all carbohydrate tolerance disturbances in pregnancy. This proposed diabetic screening is generally required in any pregnant woman with a history diabetes, obesity greater than or equal to 20%, age greater than or equal to 30 years and glucosuria. A gestational diabetes is to be considered into consideration if in a 50 g-oral-glucose-tolerance-test (50 g - OGTT) 2 values exceed normal limits (fasting level 5.55 mmol/l, 60 minutes level 8.88 mmol/l and 120 minutes level 7.22 mmol/l). Further observation of these patients has to be continued centrally.

[Morphology of the placenta in relation to glycemia status in pregnancy in diabetes mellitus]. / Morphologie der Plazenta in Relation zur Glykämielage in der Schwangerschaft beim Diabetes mellitus.

Morphological investigations in 569 placentas of diabetic women have been performed. The histological results of 300 placentas from diabetic women delivered between 1969 and 1973 were compared to 269 placentas of diabetic women from the time period 1979 to 1983. The latest time period was characterised by normoglycemic metabolic control throughout pregnancy. Besides the morphological findings clinical results especially the perinatal mortality and morbidity during the two time periods are discussed. Morphological changes in the placenta of diabetic women are depending one the quality of metabolic control during pregnancy, independing on the White classes. Normoglycemia reduces placental maturation disorders, perinatal mortality and morbidity.

[Serum sialic acid levels in cancer, pregnancy and upper respiratory infections]. / Der Sialinsäuregehalt des Serums bei Krebs, Schwangerschaft sowie Infektionen der oberen Atemwege.

A significant increase in sialic acid content is demonstrable in the sera of cancer patients. Our investigations were performed to find out whether the serum sialic acid level is altered also during pregnancy or with infections of the upper respiratory tract. Our results have revealed a slight increase in sialic acid level to occur only in the last trimester of pregnancy. However, this distinct, though statistically insignificant, increase will not lead to misjudgement in regard to cancer diagnosis, or in case control of this disease. By contrast, in 7 out of 15 patients with infected upper respiratory tract the sialic acid content was clearly above the tolerance limit so that false positive findings may possibly be obtained.

[Measurement of uteroplacental circulation with 113m indium in diabetic pregnancy]. / Die Messung der uteroplazentaren Durchblutung mit 113m In in der diabetischen Schwangerschaft.

In 122 diabetic pregnancies the placental blood flow has been estimated determining the half life of the activity inflow (2 MBq 113 m In labelled transferrin) into the placental bed. We used a highly sensitive detector (modified pinhole collimator) and a computer supported evaluation, free from subjective influences. 259 flow measurements were compared to the risk of complication in the course of a diabetic pregnancy. - The half life values in the diabetic group, calculated by a gamma camera computer system by means of an iterative regression analysis, were significantly different compared to a control group (12 pregnancies without risk.) - Severe diabetic angiopathic complications (White classes D, F, and R) are accompanied by higher half life values (placental blood flow reductions) and perinatal complications. - Even in pregnant women with gestational diabetes or disturbances of the carbohydrate metabolism a disturbed placental hemodynamic is to be found.

[Relation of uteroplacental circulation and morphologic findings in myometrial and decidual arteries in diabetic pregnancy]. / Uber den Zusammenhang von uteroplazentarer Durchblutung und morphologischen Befunden an den myometrialen und dezidualen Arterien in der diabetischen Schwangerschaft.

Placental blood flow measurements are compared to morphologic blood vessel examinations of the placental bed and uterus. In 122 diabetic pregnant women half life time of 113m Indium labelled blood inflow curves into the placenta as measured by a gamma scintillation camera on-line recorded to a computer system. - In 57 patients histological examination of uteroplacental arteries were done. - Congruent results of placental blood flow and arterial morphology were found in 66%. - In almost all patients with normal placental blood flow extensive physiological vessel findings were recorded. In patients with reduced placental blood flow pathomorphological changes were found in 54%. - In diabetes of long duration with angiopathic complications - above all in White-classes D, F and R - the ratio of pathological findings in placental blood flow and morphology was increased. - But also in gestational diabetes and in disturbances of carbohydrate metabolism pathological results are to be found. Pathological results in placental blood flow were more often than morphological changes (70 versus 40%), so that also functional factors as uteroplacental blood flow influencing ones are to be taken into account.

The effect of intensified conventional insulin therapy before and during pregnancy on the malformation rate in offspring of diabetic mothers.

56 out of the 200 pregnant diabetic women admitted to our clinic between July 1981 and June 1983 had followed a pre-pregnancy metabolic intensive treatment programme. Most of these patients achieved near-normoglycemia: 87% or more of all their blood glucose readings before conception and in the early weeks of gestation were normoglycemic. The 56 patients were delivered of 57 babies, one of them suffering from fatal heart malformation. The 144 pregnant diabetics who were admitted to hospital only after eight weeks of pregnancy and had not had any special preconceptional metabolic control gave birth to 145 children, 9 of which presented congenital malformations: 3 of these were fatal another 3 were severe, and 3 were minor. These data are in line with our previously reported results on the years 1977-81. They stress the importance of a reasonably strict metabolic control, started well before conception, to prevent excess rates of congenital malformation.

[Effect, on the newborn infant, of carbohydrate metabolism in pregnancy in insulin-dependent diabetics]. / Der Einfluss des Kohlenhydratstoffwechsels während der Schwangerschaft insulinabhängiger Diabetikerinnen auf das Neugeborene.

The influence of the moment in pregnancy of insulin dependent diabetic women, at which normoglycemia by insulin therapy could be reached, on cord blood insulin concentration and neonatal morbidity was investigated. There is a positive correlation between the moment of normoglycemia (HbA1-values less than or equal to 8.5%) and the insulin concentration and furthermore the incidence of respiratory distress syndrome and macrosomia in the newborn. It is concluded that a tight metabolic control in insulin dependent diabetic women already prior to or early in pregnancy (at least until the 16th week) will be able to decrease the incidence of morbidity in infants of diabetic mothers.

Prevention of congenital malformations in infants of insulin-dependent diabetic mothers.

From April 1977 to April 1981, 420 deliveries of infants of insulin-dependent diabetic women were performed in our department. Of the infants delivered, 23 had congenital malformations (5.5%). The malformation rate was 1.4% for infants of 420 nondiabetic women. Strict metabolic control was begun after 8 wk gestation in 292 of the diabetic women who delivered 22 infants with congenital malformations (7.5%). Intensive treatment was begun before conception in 128 diabetic women planning pregnancy. There was only one malformation in infants of this group (0.8%), a significant reduction from the anomaly rate in the late registrants (X2 = 7.84; P less than 0.01). These observations indicate that reasonable metabolic control started before conception and continued during the first weeks of pregnancy can prevent malformations in infants of diabetic mothers.

[Placental maturation disorders in relation to the quality of metabolic control during pregnancy in insulin-dependent and gestational diabetes]. / Reifungsstörungen der Plazenta in Relation zur Qualität der metabolischen Kontrolle während der Schwangerschaft beim insulinpflichtigen und Gestationsdiabetes.

In 1969/70 and 1979/80, 100 placentas each of diabetics were morphologically examined. The findings obtained were evaluated against the background of metabolic monitoring and typical phenomena of perinatal morbidity. The studies were conducted for the purpose of finding out the extent to which maintenance of normal glycaemic metabolism throughout pregnancy could affect the severity of diabetic disorders of placental maturation. Medium to severe placental maturation disorders were found to be closely correlated with quality of metabolic control (P less than 0.01). The findings thus obtained have produced evidence to the effect that maintenance of normal glycaemic metabolism throughout pregnancy would be of favourable impact not only upon perinatal mortality and morbidity. It would also cause significant reduction of placental maturation disorders.

[Behaviour of human placental lactogen (HPL) following continuous glucose infusion in late pregnancy (author's transl)]. / Das Verhalten des HPL (Humanes plazentares Laktogen) unter Glukoseinfusionsbelastung in der Spätschwangerschaft.

Continuous intravenous glucose infusion was applied to 15 pregnant women of normal body weight, in the 37th week of pregnancy. The glucose levels in the blood, serum immunoreactive insulin, and placental lactogenic hormone (HPL) were monitored for three hours. Glucose tolerances were found to be normal in five probands, borderline in another five, and pathological in five, as well. No relationships were found to exist between insulin requirement und plasma HPL levels. While all HPL levels were somewhat increased in those patients with pathological glucose tolerances, the differences were not significant.

Immunochemical investigations on the problem of the pregnancy zone protein. XII. Serum concentrations of pregnancy-associated alpha-2-glycoprotein in diabetic pregnancy.

The concentration in serum of the pregnancy zone protein (PZ), a high molecular pregnancy-associated alpha 2-glycoprotein, increases during pregnancy, when oral contraceptives are taken and under certain pathological conditions. PZ is probably part of a multifactorial immunological defence system which prevents the premature rejection of the fetus and placenta which together may be regarded as an allograft. Normally, the PZ serum concentration begins to rise during the 6th-12th week of pregnancy and reaches its peak at about the 24th week. The mean values then remain stable and afterwards diminish slightly toward the end of the pregnancy. In contrast, the mean values in mothers with insulin-dependent diabetes mellitus continue to rise. Excessively high serum PZ concentrations are significantly more frequent among pregnant diabetic patients, especially where there is also rhesus D antigen incompatibility. No correlation was found between excessively high values and the risk features used for the Priscilla White classification. A few patients with progressive proliferative retinopathy even had unusually low values.

[Value of ultrasonic fetometry for fetal monitoring in diabetes mellitus]. / Die Wertigkeit der Ultraschallfetometrie zur Beurteilung des Schwangerschaftsverlaufes bei Diabetes mellitus.

Evaluation of ultrasonic fetometry in diabetic pregnancy. In 51 cases we have carried out 134 ultrasonic investigations. The diabetes we classified to the score of White A--F. To evaluate the increase in fetal weight and the maturity in a qualified sense, we measured the biparietal diameter, the transversal and the sagital diameter of the thorax and the trunk length. The findings were registered into diagrams of our percentiles of development.--The fetopathia diabetica will be diagnosed right, if it is joint with fetal hypertrophy. The beginning of the macrosomia of the fetus is possible to recognize from the 32th week of gestation.