Pressure response of high pressure fluid valving, apparatus and methods therefor

A system to operate on a high-pressure working fluid, comprising,

• a reservoir of working fluid at high-pressure, with a fluid connection supplying the working fluid at a controlled working pressure to,
• a dose chamber to contain a volume of the working fluid at the working pressure,
• a dose valve, biased to close by a bias, and able to be triggered open, between the dose chamber and,
• a working chamber, into which a charge of the working fluid at the working pressure is released from the dose chamber via the dose valve at a first end of the working chamber, to undergo a first expansion in the working chamber and do work therein to or towards a second end of the working chamber distal from the first end, the dose valve under action of the bias closing again before a pressure front of the charge in the working chamber has travelled less than or equal to halfway between the first end and the second end, thereafter allowing a second expansion of the charge to continue doing work,
• the fluid connection having a flow restriction which is significantly less than a flow capacity of the dose valve,
• wherein when the work is completed, the charge in the working chamber is at a pressure less than or equal to half the working pressure.