STUDI EKSPERIMEN PENGARUH PANJANG THROAT TERHADAP KINERJA LIQUID JET GAS PUMP (LJGP)

Dandung Rudy Hartana, Prof. Dr. Ir. Indarto, DEA.

2014 | Tesis | S2 Teknik Mesin

Liquid jet gas pump (LJGP) adalah mesin fluida yang prinsip kerjanya berdasarkan pada perbedaan momentum. Momentum yang dihasilkan oleh nozzle menginduksi gas di dalam suction chamber. Transfer momentum terjadi antara liquid jet dan gas di tempat yang dikenal dengan throat. Di dalam throat terjadi proses mixing antara liquid dan gas. Proses ini menghasilkan perubahan pola aliran dan kenaikan tekanan. Perubahan pola aliran sebelum terjadi mixing adalah jet flow dan setelah mixing adalah froth flow. Perlambatan kecepatan aliran juga mengakibatkan terjadinya kenaikan tekanan. Fraksi gas yang terbawa bersama cairan akan termampatkan di dalam throat setelah terjadinya proses mixing tersebut. Posisi proses mixing ini sangat bergantung dengan perubahan debit liquid jet dan gas. Pada debit gas yang tinggi maka proses mixing terjadi menjauhi throat inlet dan kemungkinan terjadi di dalam diffuser. Kondisi ini mengakibatkan efisiensi turun. Agar agar proses mixing selalu di dalam throat, maka diperlukan penelitian yang mampu menemukan korelasi antara pengaruh debit liquid jet dan debit gas terhadap panjang throat. Serangkaian pengujian dilakukan yaitu: memvariasikan debit liquid jet terhadap debit gas untuk variasi panjang throat berturut-turut 2dt, 4dt, 6dt. Pengujian ini dilakukan pada seksi uji dengan dimensi yaitu: diameter throat (dt) = 8,5 mm, diameter nozzle = 5,7 mm atau area ratio = 0,45. Hasil pengujian memperlihatkan bahwa ada pengaruh panjang throat terhadap kinerja LJGP untuk seluruh variasi debit liquid jet dan debit gas. Karakteristik LJGP secara keseluruhan memperlihatkan kecenderungan yang sama untuk kombinasi variasi debit liquid jet dan debit gas. Kecenderungan tersebut adalah: semakin kecil debit gas semakin rendah tekanannya debit liquid jet tetap, semakin kecil debit liquid jet semakin tinggi tekanan pada suction chamber. Sedangkan pengaruh perubahan panjang throat memperlihatkan panjang throat 4dt menghasilkan efisiensi tertinggi dibandingkan dengan panjang trhoat 2dt dan 6 dt untuk seluruh kombinasi debit aliran liquid jet dan debit gas.

Liquid gas jet pump (LJGP) is a fluid machine working principle is based on the difference in momentum. The momentum generated by the gas nozzle induces in the suction chamber. Momentum transfer between the gas and the liquid jet at a place known by the throat. In the process of mixing the throat occurs between liquid and gas. This process resulted in changes in the pattern of flow and pressure rise. Changes in flow patterns before and after mixing is jet flow to Froth flow. Slowing the flow rate also resulted pressure rise. Fractions were carried with the liquid gas will be compressed in the throat after the occurrence of the mixing process. The position of the mixing process is highly dependent on the change of the liquid flow rate and gas flow rate. At high gas flow rate, the mixing process occurs away from the inlet throat and possibly occurs in the diffuser. These conditions resulted in the efficiency decreases. In order that the mixing process is always in the throat, then the necessary research that is able to find a correlation between the effect of the discharge of liquid jet and gas discharge to a long throat. A series of tests are carried out: varying the liquid flow rate on gas flow rate for length variation throat consecutive 2dt, 4dt, 6dt. The test is performed on a test section with dimensions: throat diameter (dt) = 8.5 mm, nozzle diameter = 5.7 mm or area ratio = 0.45. The test results showed that there was a long-throat effect on the performance of the entire variation LJGP to discharge liquid jet and gas discharge. LJGP overall characteristics show a similar trend for the combination of variation and discharge of liquid jet gas discharge. The trend is: the smaller gas flow rate is the lower pressure in suction chamber on liquid jet flow rate constant. While the length of the throat shows the effect of changing the length throat 4dt produce the highest efficiency compared with the length throat 2dt and 6dt for all combinations of liquid flow rate and gas flow rate.

Kata Kunci : LJGP, throat, diffuser, proses mixing