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Compressible Natural Gas Flow Study For Vehicle Refueling Equipment

Hisam, Nor Azizah (2006) Compressible Natural Gas Flow Study For Vehicle Refueling Equipment. Masters thesis, Universiti Teknologi Petronas.

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There is considerable interest in Malaysia for the use of natural gas as the fuel for transportation. Natural Gas Vehicles (NGV) are known to be more environmentally friendly, safer and of lower fuel cost. To encourage the public to use natural gas, more NGV stations would have to be built. A major constraint in providing this facility is the high construction and operating cost of the stations. This is mainly due to the high cost of the metering system (cost of metering system is RM 80,000 while cost ofrefueling equipment is RM120, 000) and the compression power needed. The present research is undertaken to find a solution to these problems by developing a new low cost metering system and a new operating system approach which will lower the overall compression power needed at the refueling station by RM 0.89 millions per year. To understand the reasons for the high compression cost, the compressible gas dynamics model oft he refueling system is required. The flow of natural gas between the storage and the receiver has been modeled as Fanno Flow. In the event where the storage pressure is significantly higher than the automotive fuel tank, Mach number increases along the dispensing hose and ultimately become one at the tip of the hose. The Mach number cannot become higher than one under the Second Law of Thermodynamic, causing a pressure discontinuity between dispenser tip and automotive fuel tank. Due to the pressure discontinuity, the gas will experience sudden expansion and the expansion experienced by the gas at the pipeline exit was found to be significant thus resulting in high energy loss. To avoid this high energy loss, the study conducted indicates that by utilizing several sources placed at different pressure levels and by gradually changingover from the lower to the higher pressure source, the energy losses could be reduced. From the compressible gas flow model study, a new cascaded storage system which consists of 3 different levels of pressure banks i.e. 2MPa, 1 OMPa and 24.8MPa as low, medium and high pressure bank respectively has been proposed. This new cascaded storage system will help to reduce the operation cost by 17.5% by reducing the compression energy required and also the energy loss during refueling. For developing a simple and cost effective measurement technique, a study on the properties relationship of natural gas is important. From the consideration of several equations of state (EOS) which are available in literature, it is important to find one which can represent the natural gas system with sufficient accuracy. For finding the most suitable equation for the system the approach used was analyzing the relationship between pressure and mass for different types of equations with assistance of HYSYS Software. These theoretical values were then compared with the actual measured experimental values. For natural gas system, the Peng Robinson equation was found to be the most accurate equation for the system with average error of0.19%. Besides the high compression cost in the filling stations, high metering cost is also an obstacle to the growth of NGV refueling facility. The flow meter used in the metering system namely Coriolis Flow Meter represents about 33.3% of the total typical 2 hose CNG dispenser cost. This project is believed to contribute in reduction of at least 30% (from RM120,000 to RM80,000) of current CNG dispenser capital expenditure (CAPEX) value. From the study of the EOS, a new concept of metering system has been developed, which is based only on measuring the pressure and temperature. This new metering system eliminated the dependency on currently used Coriolis Flow Meter which is a very expensive mass flow meter.

Item Type: Thesis (Masters)
Academic Subject : Academic Department - Chemical Engineering - Process System Engineering
Subject: T Technology > TP Chemical technology
Divisions: Engineering > Chemical
Depositing User: Users 2053 not found.
Date Deposited: 27 Sep 2013 11:06
Last Modified: 25 Jan 2017 09:46
URI: http://utpedia.utp.edu.my/id/eprint/7007

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