Variable throat pipe air inlet device for cetane number measuring machine

The utility model discloses a variable throat pipe air inlet device for a cetane number measuring machine. The variable throat pipe air inlet device comprises a measuring machine, a variable throat pipe, an air pump and two fixing blocks, through cooperative use of the positioning mechanism, the transmission mechanism and the sealing ring, after the transmission mechanism drives the positioning mechanism to move to a proper position, the variable throat pipe is taken out to be cleaned or replaced, then the variable throat pipe is in butt joint with the air pump, then the transmission mechanism is loosened, and the positioning mechanism can fix the variable throat pipe while resetting; the variable throat pipe is replaced or cleaned, and the problems that according to an existing measuring machine, the variable throat pipe needs to be connected with an air pump for gas transmission, some foreign matter can be left on a throttle valve at the connecting position after use, and the variable throat pipe needs to b