The subject matter of this specification can be embodied in, among other things, a method for operating a hydraulic free piston engine includes receiving, at an engine controller for a hydraulic free piston engine, an energy parameter that is representative of an amount of fluid energy to be output by the engine, and a measured fluid pressure value of a fluid load of the engine, determining a piston trajectory of a piston within a hydraulic chamber of the engine, determining a fuel volume value and a servo valve actuation parameter, based on the energy parameter and the measured fluid pressure value, providing a fuel control signal to a fuel control device of the engine based on the fuel volume value, and providing, based on the servo valve actuation parameter and the piston trajectory, a servo valve control signal to a servo valve.

The invention is a pump engine developed for the purpose of launching and pumping capsules in a hydraulic pipeline. The engine operates on the combustion and explosion of a mixture of fuel and oxygen bearing gases against a liquid piston that passes through a dynamic current turbine. The rotation of the turbine maintains a constant direction of rotation through the oscillation of the water column, and drives a special rotor to feed capsules from a hopper into the pipeline, while the liquid piston pushes them into the pipeline and applies the necessary pressure. The turbine also drives the necessary auxiliaries such as alternator and camshaft for water valves and air inlet and exhaust valves. The pump engine is built in single cylinder or multiple cylinders in duplex and fourplex configurations.

The subject matter of this specification can be embodied in, among other things, a method for operating a hydraulic free piston engine includes receiving, at an engine controller for a hydraulic free piston engine, an energy parameter that is representative of an amount of fluid energy to be output by the engine, and a measured fluid pressure value of a fluid load of the engine, determining a piston trajectory of a piston within a hydraulic chamber of the engine, determining a fuel volume value and a servo valve actuation parameter, based on the energy parameter and the measured fluid pressure value, providing a fuel control signal to a fuel control device of the engine based on the fuel volume value, and providing, based on the servo valve actuation parameter and the piston trajectory, a servo valve control signal to a servo valve.

Motion control of a hydraulic free-piston engine is achieved in order to enable advanced combustions such as low temperature combustion. To accomplish this, an active controller acts as a virtual crankshaft, which causes a piston to follow a reference trajectory using energy from a storage element. Given the periodic nature of free-piston engine motion, an advanced controller of the present invention is preferably of robust repetitive type that is capable of tracking periodic reference signals.

An internal combustion engine has a chamber that has a longitudinal centerline, inlet valving operable to admit constituents of a combustible mixture into the chamber for combustion in the chamber to provide a pressure increase in the chamber and outlet valving operable to release an outflow of liquid from the chamber under an influence of the pressure increase. An annular flow passage is defined in the chamber to conduct liquid towards the outlet valving and cause spiraling of the liquid in the flow passage by which a rotatable part exposed to the spiraling flow is caused to rotate. An electrical generator disposed externally of the chamber is driven by rotation of the rotatable part.