Fig. 8 Injection system of for liquefied CO2 mixed fuel
5. FUEL INJECTION SYSTEM
EXPERIMENTAL APPARATUS AND PROCEDURE - Figure 8 displays the flow sheet of experiments. N2 gas of 10 MPa is transferred to a high pressure vessel in order to melt dry ice into stable liquefied CO2. The pressurized liquefied CO2 is going to an oil pressure booster 1 with quasi-steady state, n-Tridecane, that is, n-C13H28, as fuel oil in a fuel tank is sent into the oil pressure booster 1 also. A rod connected with a piston in an air cylinder is inserted in the oil pressure booster I. A disk attached at the top of the rod is moving up and down in order to stir and mix liquefied CO2 with n-Tridecane. Then, liquefied CO2 Was dissolved in n-Tridecane with arbitrary mixture ratio. Air in an air bomb guided through a pressure regulator drives the oil pressure booster 1. A 5-port solenoid valve controls supply of fuel oil to the oil pressure booster 1 and its pressurization. Injection pressure is governed by a pressure regulator and needle lift of injector is controlled by an oil pressure booster 2. Pressure in an oil hydraulic cylinder located at the upper-side of injector is varied by solenoid valves 1 and 2 and that in an air cylinder at the middle position of injector is done by a pressure regulator. Then, injection timing and injection pressure were controlled arbitrary by both pressures. Injection pressure is set at 10 and 20 MPa. Nozzle needle lift is measured by a gap sensor and injection pressure is detected by a piezo pressure sensor.
6. COMBUSTION CHARACTERISTICS OF MIXED FUEL OF LIQUEFIED CO2 AND n-TRIDECANE
COMBUSTION EXPERIMENTS - For the combustion experiments, a Rapid Compression & Expansion Machine (RCEM) with 100 mm bore was used. The specifications of RCEM is shown in Table 1. The chamber shape is a flat disk type with a side injection system. The temperature of a cylinder wall is adjusted to a predetermined one by supplying hot water into a water jacket. Air is changed in the cylinder through a pressure regulator from an air bomb. And, NO, CO, CO2 and THC concentration in burst gas are detected with a chemiluminescence analyzer (HORIBA : CLA-53), a non-dispersive infrared analyzer (HORIBA : AIA-23) and a flame ionization detection analyzer (HORIBA : FIA-52) after the gas is gathered into a sampling bag. And smoke is measured by a smoke meter (XECSEL: DSM-20A). For a test fuel, n-Tridecane (mole fraction of CO2 is zero), and the mixed fuel of liquefied CO2 and n-Tridecane (mole fractions of CO2 are 0.4, 0.6 and 0.8) are used.
EXPERIMENTAL CONDITIONS - Table 2 shows experimental conditions. Single hole nozzle (dn = 0.18 mm, ln/dn = 4.17), which is set at top side, was used with the injection pressure pinj of 16 MPa. The injected fuel quantity of n-Tridecane was the same as 10 mg/st. for both standard injection of only n-Tridecane (XCO2 = 0.0) and mixed fuel injection (XCO2 = 0.4, 0.6, 0.8).
Fig. 9 Pressure-Temperature diagram for mixed fuel in RCEM
