Analytical method for profiling of radial stator blades of turbine stages

The method of analytical profiling of radial stator blades is considered, which in combination with numerical modelling of three-dimensional viscous flows allows us to improve the efficiency of the flow part of high-loaded centripetal turbines. The profile of radial blades is determined in a curvilinear coordinate system and consists of the trailing and leading edges, and also of suction and pressure sides described by polynomial curves of the 5th and 4th order, respectively. Thanks to this method, highly efficient radial stator blades of high-loaded stages can be designed. The special form of blade-to-blade channels allows us to obtain a low level of profile and trailing edge losses, as well as low supersonic and shock wave losses of kinetic energy. Three variants of turbines with different types of stator blade profiles are considered: the profile developed using a standard method for axial blades; the “half-drop” profile and the profile developed using the proposed method. For the stator profile developed in this paper, the stator kinetic energy losses related to the enthalpy drop in the stage were decreased by 2,2% compared to the profile of a classic form, and by 1,1% compared to the “half-drop” profile. Using of the high-loaded stage with a new type of stator blade profile allowed us to significantly improve the aerodynamic characteristics of the flow part in the whole stage.Рассмотрен метод аналитического профилирования радиальных лопаток направляющих аппаратов, использование которого в сочетании с численным моделированием трехмерных вязких течений позволяет повысить эффективность проточных частей высоконагргженных центростремительных турбин.Запропоновано аналітичний метод побудови профілів радіальних лопаток турбінних ступенів. Профіль задається в криволінійній системі координат, складається з вхідної та вихідної кромок, а також спинки і коритця, описаних кривими 5-го та 4-го порядків відповідно. Розглянуто приклад високонавантаженого радіально-осьового ступеня з профілем направляючого апарата нового типу, застосування якого дозволило істотно поліпшити аеродинамічні характеристики проточної частини

Improving the efficiency of radial-axial rotors of turbine stages through the use of complex lean of trailing edges

The influence of shape of the blade trailing edges on the flow patterns and integral flow characteristics of the radial-axial turbine rotors is investigated. Also a modified analytical method of design of spatial blades of radial-axial rotors with complex lean of leading and trailing edges is proposed. A radial-axial rotor designed for a turboexpander unit of a complex gas treatment plant working in a gas condensate field is chosen as an object of investigations. Three types of rotors are considered having the same geometry of meridional contours, but differing in shape of blade trailing edges. In the first variant of the rotor its blades have radial trailing edges, in the second variant the trailing edges are straight with circumferential lean, and in the third variant they are designed in the form of arcs leaned in the circumferential direction. It is shown that the application of complex lean of trailing edges of low-loaded radial-axial rotor blades allows us to increase the flow efficiency by 3.1% compared with the rotor blades having radial trailing edges.Проведено исследование влияния формы выходной кромки на структуру потока и интегральные характеристики проточной части, а также предложен модифицированный аналитический метод задания пространственных радиально-осевых рабочих колес (РК) со сложными навалами входных и выходных кромок. В качестве объекта исследования выбрано радиально-осевое РК, предназначенное для турбины турбодетандерного агрегата установки комплексной подготовки газа, работающей на одном из газоконденсатных месторождений. Рассмотрено три типа РК, имеющих одинаковую геометрию меридиональных обводов, но отличающихся формой выходных кромок. В первом варианте РК выходные кромки радиальные, во втором – прямые с окружным навалом, а в третьем – в виде дуги, наваленной в окружном направлении. Показано, что использование сложного навала выходных кромок низконагруженного радиально-осевого РК позволило повысить КПД на 3,1% по сравнению с конструкцией с радиальными выходными кромкамиЗапропоновано модифікований аналітичний метод задання просторових радіально-осьових робочих коліс зі складними навалами вхідних і вихідних кромок. Досліджено вплив форми навалу вихідних кромок лопаток радіально-осьових робочих коліс на їх ефективність. Показано, що використання складного окружного навалу вихідних кромок дозволяє забезпечити істотне підвищення коефіцієнта корисної дії низьконавантажених радіально-осьових робочих коліс

Jejunal Diverticular Perforation due to Enterolith

Jejunal diverticulosis is a rare entity with variable clinical and anatomical presentations. Although there is no consensus on the management of asymptomatic jejunal diverticular disease, some complications are potentially life-threatening and require early surgical treatment. Small bowel perforation secondary to jejunal diverticulitis by enteroliths is rare. The aim of this study was to report a case of small intestinal perforation caused by a large jejunal enterolith. An 86-year-old woman was admitted with signs of diffuse peritonitis. After initial fluid recovery the patient underwent emergency laparotomy. The surgery showed that she had small bowel diverticular disease, mainly localized in the proximal jejunum. The peritonitis was due to intestinal perforation caused by an enterolith 12 cm in length, localized inside one of these diverticula. The intestinal segment containing the perforated diverticulum with the enterolith was removed and an end-to-end anastomosis was done to reconstruct the intestinal transit. The patient recovered well and was discharged from hospital on the 5th postoperative day. There were no signs of abdominal pain 1 year after the surgical procedure. Although jejunal diverticular disease with its complications, such as formation of enteroliths, is difficult to suspect in patients with peritonitis, it should be considered as a possible source of abdominal infection in the elderly patient when more common diagnoses have been excluded