Influence of Bubbles Causing Cavitation on Spool Oscillation of a Direct Drive Servovalve

A direct drive servovalve has some inherent benefits over its conventional counterparts, but also has better reliability and output power. However, due to the rigid connection between the spool and the motor, which takes the place of interstage drive-by fluid, the spool oscillation is a long-standing unsolved problem. In order to study the oscillation mechanism and the influencing factors, a double-circuit direct drive servovalve was numerically simulated. An oil return valve cavity was concentrated on as the main flow domain and was used to analyze the fluid flow characteristics. Local cavitation fraction and surface average cavitation fraction were defined to evaluate the cavitation situation. The periodic growth process of bubbles in the valve cavity was obtained. The numerical results show that bubbles in the oil return valve cavity changes, although the occurrence, evolution, and collapse stages were certain. The intensity of pressure pulsation caused by bubble variation is highly related to the bubbles causing the cavitation, which suggests a workable way to inhibit the spool oscillation.

Heimlich Valve as an Ambulation Management of Persistent Pneumothorax or Fluidopneumothorax

Pneumothorax or fluidopneumothorax is a critical condition when there is some air or/and fluid in the plural cavity. The symptoms may include shortness of breath, chest pain, blue discoloration of the skin or lips, increased heart rate, and loss of consciousness. Pleural cavity drainage is management therapy with the concept of Water Seal Drainage (WSD), which requires a long hospital stay. Heimlich valve is a non-return valve that allows fluid and air to exit the thoracic cavity (on inspiration) and prevents fluid and air from re-entering (during expiration). Heimlich valve is a viable, inexpensive, convenient, safe, effective, and efficient alternative in the management of ambulation of patients requiring prolonged pleural cavity drainage. The use of Heimlich valve is an alternative option for patients with persistent pneumothorax or fluidopneumothorax. It can shorten the time of treatment in the hospital, lowering treatment costs, and minimize the presence of nosocomial infections. Relative contraindications include fluidopneumothorax with massive pleural effusion or empyema. The risks and complications are dislodgement or improper reattachment, leaking valve, adhesion, and blockage, thus becoming tension pneumothorax or pleural cavity infection. Currently the latest innovation also improves the patient’s convenience, like Thoracic Vent, Pneumostat, or Mini Mobile Dry Seal Drain.

Simulation of Non-Return Valve Closure in a Thixomolding Process Utilizing a Magnesium Alloy

Simulation of Non-Return Valve Closure in a Thixomolding Process Utilizing a Magnesium Alloy

Simulation of Non-Return Valve Closure in a Thixomolding Process Utilizing a Magnesium Alloy

Simulation of Non-Return Valve Closure in a Thixomolding Process Utilizing a Magnesium Alloy

Hydrodynamic luminescence in a model diesel injector return valve

A sample of unadditized diesel fuel was passed through an optically accessible model diesel injector return valve, which consisted of two successive nozzles connected to an intermediate fuel gallery. The first nozzle was cylindrical, while the second nozzle was stepped. The fuel was observed to produce a multi-phase, cavitating flow and a luminous blue-violet emission at the entrance to the second nozzle hole. The flow in the upstream intermediate fuel gallery and the first nozzle hole remained single-phase. Spectral analysis of the luminous emission revealed a spectrum with thermal features containing broad spectral lines and peaks at 358, 389, 405, 412, 430 and 475 nm, suggesting that the emission was dominated by π*→π transitions in the alkylated mono-, di-, and tri-aromatics, with additional spectral contributions from CH, C2, C3 and hydrogen (H).

ANALYSIS OF THE INFLUENCE OF THE CHECK VALVE FORM ON THE FUEL-SUPPLY PROCESS IN THE DISTRIBUTION TYPE PUMPS

The stability of the values of cyclic feeds and the angle of the actual beginning of the fuel supply largely depends on the presence of the injection valve of the fuel pump section and its design features. The valve must reliably separate the discharge line from the pre-plunger space and, within certain limits, ensure the residual pressure in the discharge line between cycles. However, the installation of the valve causes a repeated reflection from the valve of the pressure impulses, that follow from the nozzle and leads to the appearance of additional injections or a sluggish fit of the needle on the sprayer seat. In order to eliminate negative consequences, double-acting injection valves are installed on distribution-type pumps, in which the pressure impulses are extinguished by transferring fuel through an additional non-return valve. The use of double-acting valves with non-return valves on distribution-type pumps ensures reliable unloading of the discharge pipe from the cut-off cavity. One of the main purposes of a non-return valve is to provide the necessary hydraulic density of the coupling pressure valve - non-return valve. Serial pumps are equipped with cross-shaped and round-shaped check valves in cross-section, which are designed to provide the same hydraulic tightness of the coupling pressure valve - non-return valve. In the course of research, the results of which are presented in the work, it was revealed that they have different sealing characteristics. In parallel, the characteristics of a triangular and square check valve in cross section were investigated. As a result of research, it was found that square valves have the best sealing characteristics. In the course of the research, it was also revealed that serial check valves of cruciform and round shapes do not provide their functional interchangeability, since they have different abilities to ensure hydraulic tightness of the interface with the discharge valve - non-return valve. Square-shaped check valves in cross-section are more technological to manufacture.

IDENTIFIKASI DAMPAK DECK WATER SEAL UNTUK PENINGKATAN KERJA INERT GAS SYSTEM DI MT. GREEN STARS DENGAN METODE FTA

Inert Gas System adalah pesawat bantu yang digunakan untuk mempertahankan kadaroksigen yang rendah dalam tangki sehingga memungkinkan timbulnya kebakaran. Purging padatangki-tangki muatan yang kosong dengan maksud menggantikan campuran hidrokarbon gasdengan inert gas agar bisa mengurangi konsentrasi atau kadar hidrokarbon di bawah garisyang disebut Critical Dilution. Kalau sampai ada udara segar masuk ke dalam tangki tersebutmaka kondisi atmosfir dalam tangki akan segera masuk dalam kantong dimana campuran inidapat terbakar atau rusak. Terdapat 3 permasalahan yang terdapat pada IGS saat dioperasikanyaitu perawatan Deck Water Seal diperlukan dalam pengoperasian IGS, dampak apabila DeckWater Seal tidak bekerja secara maksimal dan upaya yang dilakukan agar Deck Water Sealbekerja secara maksimal dalam pengoperasian IGS. Untuk mengupayakan agar IGS dapat beroperasi dengan maksimal maka diadakanpenanganan yang baik dan tepat, dalam mencari solusi permasalahan digunakan metode FaultTree Analysis (FTA). Metode analisis ini terutama digunakan dalam bidang teknik keselamatandan rekayasa keandalan untuk memahami bagaimana sistem bisa gagal, untuk mengidentifikasicara terbaik untuk mengurangi resiko angka kejadian kecelakaan keselamatan atau systemfungsional, FTA mengidentifikasi hubungan antara faktor penyebab dan ditampilkan dalambentuk pohon kesalahan yang melibatkan suatu gerbang logika sederhana. Perawatan DeckWater Seal sangat penting dalam pengoperasian IGS, yaitu salah satunya merawat komponenyang menunjang kinerja dari Deck Water Seal seperti demister pad, inert gas blower. Dalamdemister pad ada komponen lain yaitu deck seal pump dan drain valve. Begitu juga dalan inergas blower ada safety valve, mast riser, non return valve. Komponen tersebut sangatlah pentingguna menunjang kinerja dari deck water seal. Masinis dapat melaksanakan kegiatan perawatandengan baik terhadap deck water seal, agar kerja dari deck water seal dapat bekerja secaramaksimal pada saat pengoperasian IGS di kapal.