减压阀是一种自动降低管路工作压力的装置，作用是在给定减压范围后，可以将较高压力的介质减到给定压力。目前多数减压阀都是一种恒压减压阀即减压阀输出的压力保持在一个恒定的范围，且是常开减压阀。但是，对于燃气发动机这一类的燃气设备，这种恒定压力的减压阀不适用，因为发动机运行时，所需的燃气压力和燃气量多少不是恒定的，需要根据实际情况，进行实时调节，以达到输出燃气气体压力和燃气量与发动机所需相匹配。所以，燃气发电机就需要使用起起稳压作用的负压阀来保证发电机的稳定工作。

A pressure reducing valve is a device that automatically reduces the working pressure of a pipeline. Its function is to reduce a medium with higher pressure to a given pressure after a given pressure reducing range. At present, most pressure reducing valves are constant pressure reducing valves that maintain a constant range of output pressure and are normally open. However, for gas equipment such as gas engines, this constant pressure reducing valve is not suitable because the required gas pressure and quantity are not constant when the engine is running, and real-time adjustments need to be made according to the actual situation to achieve output gas pressure and quantity matching the engine's requirements. Therefore, gas generators require the use of negative pressure valves that serve as voltage stabilizers to ensure the stable operation of the generator.