Ejector having throttle variable nozzle and ejector cycle using the same

An ejector comprising:

• a nozzle having an inner wall surface for defining a fluid passage through which a drive fluid flows, the nozzle including a throat section having a cross-sectional area that is the smallest in the fluid passage;
• a pressurizing section in which a fluid is sucked by entrainment of a jet flow of the drive fluid jetted from the nozzle and is mixed with the drive fluid jetted from the nozzle;
• and
• a needle valve for changing a throttle opening degree of the fluid passage, the needle valve being disposed to be displaced in an axial direction in the fluid passage of the nozzle, wherein:
• the needle valve has an end section formed in a tapered shape so that a cross-sectional area of the needle valve decreases toward a top end of the needle valve;
• the end section of the needle valve reaches to a downstream side of the throat section in a flow direction of the drive fluid at least when the throttle opening degree is minimum;
• and
• the fluid passage is formed into a tapered shape having a cross-sectional area that is gradually decreased by a taper angle θ1 toward an outlet of the fluid from a downstream side of the throttle section to at least the throat section, and the taper angle θ1 of the fluid passage is smaller than a taper angle θ2 of the end section of the needle valve.

An ejector cycle comprising:

• a compressor for compressing refrigerant;
• a high-pressure side heat exchanger for cooling refrigerant discharged from the compressor;
• an evaporator for evaporating low-pressure refrigerant after being decompressed;
• an ejector including
• a nozzle having an inner wall surface for defining a refrigerant passage for decompressing refrigerant from the high-pressure side heat exchanger, the nozzle including a throat section having a cross-sectional area that is the smallest in the refrigerant passage,
• a pressurizing section in which refrigerant from the evaporator is sucked by entrainment of a jet flow of the refrigerant jetted from the nozzle and is mixed with the refrigerant jetted from the nozzle, and
• a needle valve for changing a throttle opening degree of the refrigerant passage in the nozzle, the needle valve being disposed to be displaced in an axial direction in the refrigerant passage of the nozzle;
• and
• a gas-liquid separator for separating refrigerant flowing from the ejector into a gas refrigerant to be supplied to the compressor and a liquid refrigerant to be supplied to the evaporator, wherein:
• the needle valve has an end section formed in a tapered shape so that a cross-sectional area of the needle valve decreases toward a top end of the needle valve;
• the end section of the needle valve reaches to a downstream side of the throat section in a flow direction of the refrigerant at least when the throttle opening degree is minimum;
• and
• the refrigerant passage of the nozzle has a substantially constant cross-sectional area, in a downstream section downstream from the throat section.