Abstract: Systems and methods for a multi-path purging ejector are disclosed. In one example approach, a dual path purge system for an engine comprises an ejector including a restriction, first and second inlets, and an outlet, at least one break-point at the restriction or inlets, and a shut-off valve coupled to the outlet.

Abstract: A flow control valve (15) for a direct injection pump (10) has an inlet end (12), an inlet valve (26), a compression chamber (48), a pump piston (14), and an outlet (13). The valve (15) has a housing (16) and a non-electrically operated control plunger (22) movable within the housing. The control plunger engages with and disengages from the inlet valve to control opening and closing of the inlet valve. A spring (28) biases the control plunger away from the inlet valve. The pump and housing define port structure (38, 44) fluidly connecting the outlet with a volume (42) that communicates with the control plunger such that when fluid pressure at the outlet is greater than a certain value, the fluid pressure in the volume alone causes the control plunger to move against the spring and engage the inlet valve to hold the inlet valve in an open position.

Abstract: A fuel injection pump is provided which can be manufactured without an increase in the manufacturing cost and which is configured so that the sealing performance of an electromagnetic spill valve can be maintained with minimum maintenance cost.

Abstract: Methods are provided for finding the bulk modulus of a fuel used in the direct injection system of an internal combustion engine. A method is needed to continuously monitor and reliably calculate the fuel's bulk modulus during engine operation on-board the vehicle, where the fuel's bulk modulus may be used to infer the ratio of fuels in a fuel mixture or determine the density of supercritical propane when propane is used as the injected fuel. To find the fuel's bulk modulus on-board a vehicle, methods are proposed that involve monitoring and recording fuel rail pressures, high pressure pump duty cycles, and fractional liquid volume pumped values in order to find zero flow relationships.

Abstract: Provided is an engine starting device enabling the meshing engagement of a pinion gear and a ring gear to be quickly and quietly achieved in an automatic idle-stop system while an engine is rotating by inertia. The engine starting device includes: a ring gear connected to a crankshaft of an engine; a starter motor for starting the engine; a pinion gear for transmitting rotation of the starter motor to the ring gear; pinion-gear moving portion for moving the pinion gear so as to achieve meshing engagement with the ring gear; and starter control portion for executing any one of a plurality of control modes.

Abstract: A method and system for improving automatic engine stopping and starting is presented. In one example, the method adjusts conditions for engine stopping in response to operating conditions that are evaluated according to one or more cost functions. The method may improve vehicle fuel economy and limit driver annoyances.

Abstract: An on-board electrical system for a motor vehicle contains a first energy storage unit with a first voltage level and a second energy storage unit with a second voltage level. A control unit controls a flow of current between the first energy storage unit and the second energy storage unit in both directions. A polarity-reversal protection diode connects the first energy storage unit for supplying operating voltage to the control unit. A switching element bridges the polarity-reversal protection diode when the polarity of the first energy storage unit is correct. The first voltage level is compared with the second voltage level by a comparator and the switching element is moved to its open state when the first voltage level drops to a threshold voltage value which is below the second voltage level.

Abstract: The present invention relates to a method for monitoring an ignition system, wherein the ignition system comprises a charge coil (L1) for charging the ignition system, a primary coil (L4) and a secondary coil (L5), said primary and secondary coils (L4, L5) being arranged to generate a voltage for spark generation, and a control unit (M1), characterized in the steps a) providing a separate coil (L3) adjacent to at least one of the charge coil (L1), the primary coil (L4) and the secondary coil (L5) b) using the control unit (M1) to monitor a magnetic flux at the separate coil (L3), and c) using information regarding said magnetic flux as input for controlling at least one property of an operation of the ignition system. The invention also relates to a control system for an ignition system.

Abstract: Methods and systems are provided for using an engine laser ignition system to perform a visual inspection of an engine and diagnose various cylinder components and conditions based on engine positional measurements. Laser pulses may be emitted at a lower power level during an intake and/or exhaust stroke to illuminate a cylinder interior while a photodetector captures images of the cylinder interior. Additionally, laser pulses may be emitted at a higher power level to initiate cylinder combustion while the photodetector captures images of the cylinder interior using the light generated during cylinder combustion.

Abstract: An in-pipe hydraulic turbine system includes a pipeline for fluid transport, the pipeline having an inlet and an outlet, and a turbine disposed within the pipeline, between the inlet and the outlet. The turbine is actuated by fluid moving through the pipeline and leaves usable fluid pressure downstream of the turbine.

Abstract: A power generating and floating plant (100) over a natural river, a man-made canal or similar for the generation of electricity that comprises: a floating platform (102) of the Catamaran type with pontoons (112) that speed up the flow rate (300) entering into a turbine; a metal grill (113) between said pontoons (112) before the turbine; at least one turbine with a central shaft (103), wherein said turbine comprises a water wheel (101) with curved vanes (410) and at least two supporting disks (400), where said curved vanes (410) rest, and where said supporting disks (400) comprise a plurality of radial and concentric holes (402); and a low-engine speed, permanent magnet generator (105).

Abstract: A device for converting wave-motion power having a float, which, in use, is vertically movable in response to the wave-motion; the motion being transmitted to an input shaft which rotates with reciprocating rotary motion and is connected to an output shaft by way of a transmission unit. The transmission unit transfers torque from the input shaft to the output shaft along two torque paths and has two freewheels that are arranged respectively along the two paths, and are configured so as to make the rotation of the output shaft unidirectional, independently of the rotation direction of the input shaft.

Abstract: A wave responsive electrical generator device having a buoyant member connected to an anchor by a tether line member, the line member passing through a sheave mounted within the buoyant member and descending to a counterweight, whereby vertical motion of the buoyant member results in rotation of the sheave, which in turn operates an alternator to produce electricity, wherein the line member is a plurality of belts mechanically interlocking with the sheave.

Abstract: An electrical generation system based on tidal flow includes a reservoir and a fluid inlet tube extending between a tidal source and the reservoir. The inlet tube has at least one inlet turbine generator disposed therein. The fluid inlet tube extends along a first level. A fluid outlet tube extends between the reservoir and the tidal source. The fluid outlet tube has at least one outlet turbine generator disposed therein. The fluid outlet tube extends along a second level vertically lower than the first level. During high tide at the tidal source, tidal fluid flows from the tidal source, into the fluid inlet tube, past the at least one inlet turbine generator, and into the reservoir and during a low tide at the tidal source, the tidal fluid flows from the reservoir, into the fluid outlet tube, past the at least one outlet turbine generator, and to the tidal source.

Abstract: Systems and methods to convert low temperature solar thermal or waste heat sources for electric power generation, by integrating available technologies with a unique, efficient combined cycle. The device consists of mobile pods immersed within a thermal sink fluid reservoir. A vapor cycle converts thermal energy to buoyant potential energy by inducing density and volume changes of the mobile pods through discrete phase changes of a refrigerant working fluid. Buoyant potential energy is then converted to electrical power through motion of the entire pod within a thermal sink pressure gradient.

Abstract: A fluid powered turbine, such as a wind turbine (10), has a hollow column (12) in which a rotating turbine is housed. A fluid directing structure (14) is supported at or near an end of the column (12) remote from the turbine. The fluid directing structure (14) has a plurality of individual inlet openings (26) spaced around its periphery and is arranged to direct air at each inlet opening into an inner pipe (18). The incoming air is constricted both within the structure (14) and as it exits the column (12) whereby its speed is sufficient to rotate the turbine (20). The structure at the top of the column (12) generally requires no maintenance and maintenance of the turbine (20) is considerably easier than with traditional wind generators as access is easy. As the turbine is enclosed, it is safer than the traditional wind generators and less noisy.

Abstract: A vertical axis wind turbine comprising blade(s) characterized in an airfoil cross section, wherein the top end and the bottom end of said blade(s) are rotationally off-set from each other, twisted up with a vertical line vertical to the horizontal plane.

Abstract: A generator with a vertically reciprocating piston, including: a cylindrical head defining an inner space and having mounted on an inner surface thereof: a solenoid defining an internal space, an upper rack, and a lower rack; a piston including: an upper part extending out of the head, and a lower part moveable within the inner space of the head, the piston adapted to move in a vertical, reciprocal movement under a force of fluid impacting airfoil blades coupled to the upper part of the piston, wherein at least two of the airfoil blades are each coupled to the piston. The lower part of the piston includes a series of magnets, and the vertically reciprocating motion of the piston causes the series of magnets to move in the vertically reciprocating motion within the internal space defined by the solenoid, so as to generate energy.

Abstract: A method for controlling a wind turbine is proposed. The wind turbine is in a wind farm and connected to a point of common coupling that is connected to a utility grid. At least one quantity indicative of a short circuit ratio of the utility grid is measured. A control parameter of a control system controlling the wind turbine and the wind farm is adjusted. based on the measured value of the quantity.

Abstract: A wind powered apparatus (or wind turbine) comprising a stator blade assembly and a rotor blade assembly wherein said stator blades assembly and said rotor blade assembly have counter rotating blades. Both sets of blades assemblies are connected to a generator and are operable to rotate the stator and rotor thereof in opposite directions relative to one another due to the blade arrangement between assemblies. The blades assemblies comprise a hub connected to an outer ring, wherein said outer ring comprises inward blades. The win turbine, more particularly the blade arrangement co-operates to improve performance of the apparatus by affecting its orientation and the rotational speed of the blades.

Abstract: Systems and procedures for wind turbine self-diagnosis which includes: a) A module for the identification (41) of potentially defective components based on the signs provided by the active alarms (31) of the wind turbine's control system, including a module for the filtration of alarms (43); b) A test module (61) with a plurality of tests for verifying the availability of the wind turbine's functional units; c) A self-diagnosis module (51) which manages the selection and sequential execution of the tests (61) applicable to the potentially defective components using a weighted algorithm for the tests (61); d) A communications module (53) which manages the storage and transmission of the results (55) of the self-diagnosis to a control center (73).

Abstract: A heat-electricity combined production system includes: a solar cell module in which a flow path through which a heat source side heating medium heated by solar heat flows, is formed and which generates electricity by solar light; a geothermal heat exchanger that absorbs geothermal heat through the heat source side heating medium; a heat pump including a heat source side heat exchanger that performs heat-exchange between the heat source side heating medium and a refrigerant and a load side heat exchanger that performs heat-exchange between the refrigerant and a load side heating medium; a controller that control the heat source side heating medium to pass through both the solar cell module and the geothermal heat exchanger; and a plurality of pipes that connect the solar cell module, the geothermal heat exchanger and the heat pump.

Abstract: The invention relates to a cam engine used in different field of the mechanical engineering, as internal-combustion engines, compressors, pumps etc. The cam engine comprises cylinders (26) with pistons (25), cylindrical tubular 3D cam (20) having a cam groove on the inner cylindrical surface and at least two asynchronously moving followers (1a and 1b) with arms (37) having main and additional rollers (3, 5).

Abstract: A pump device for lubricant includes a pump main body; a cylinder part having an introduction port and a derivation port; a piston moving within the cylinder part; an actuator moving the piston forward to a 1st position to discharge a lubricant from the derivation port, backward from the 1st position to a 2nd position to suction the lubricant from the introduction port and further backward from the 2nd position to a 3rd position to stop the suction and discharge of the lubricant; and a driving control device controlling the actuator such that when the lubricant is supplied, the piston is moved from the 3rd position to the 1st position and moved between the 1st position and the 2nd position, and when the lubricant is not supplied, the piston is moved to the 3rd position and stopped.

Abstract: A pump chamber is connected to an outlet-side buffer chamber via an outlet channel, and pumps a liquid from the outlet-side buffer chamber. A pressure vibration generated within the pump chamber when the volume of the pump chamber is decreased includes various kinds of information relating to the operating states of the liquid feed pump, such as mixing of bubbles, pumping pressure, dissolved gas amount, and liquid feed amount. Thus, it is possible to detect the pressure vibration, thereby simply and easily detecting the various kinds of information relating to the operating states of the liquid feed pump.

Abstract: The present invention discloses a linear compressor which can rapidly overcome load and improve compression efficiency, by synchronizing an operation frequency of a linear motor with a natural frequency of a movable member varied by the load and varying a stroke of the movable member according to the load. The linear compressor includes a fixed member having a compression space inside, a movable member linearly reciprocated in the fixed member in the axial direction, for compressing refrigerants sucked into the compression space, one or more springs installed to elastically support the movable member in the motion direction of the movable member, spring constants of which being varied by load, and a linear motor installed to be connected to the movable member, for linearly reciprocating the movable member in the axial direction, and varying a stroke of the movable member according to a predetermined refrigeration force, so that the movable member can be linearly reciprocated to reach a top dead center.

Abstract: A compressor valve structure permits improvement in durability and volumetric efficiency of a compressor and limits power losses. The width of the base portion of each suction reed valve is shorter than the width of the valve flap. The valve base plate has support portions, receiving portions, main coupling portions, and auxiliary coupling portions. Each support portion receives a central area of corresponding one of the valve flaps. The receiving portion receives a distal area of the valve flap. The main coupling portion extends from the support portion and couples the support portion to the receiving portion. The auxiliary coupling portion extends from the support portion. The suction ports are formed through the valve base plate, while leaving the support portions, the receiving portions, the main coupling portions, and the auxiliary coupling portions.

Abstract: A device for generating a synthetic jet is described. The device can include a flap, an actuator coupled to the flap and a chamber including an aperture. The flap forms a portion of the chamber. The flap is configured to oscillate in a flapping motion such that fluid is alternately drawn into the chamber via the aperture and expelled from the chamber via the aperture to form the synthetic jet. In some embodiments, multiple flaps can be used on a device to generate the synthetic jet.

Abstract: A damper assembly for a fuel pump includes at least one diaphragm assembly formed by joining two metal diaphragms to respective two sides of an imperforate central plate, thereby creating a pair of closely spaced diaphragms, each acting upon its own gas volume. Preferably, the diaphragm assembly has (a) a circular or polygonal central plate, (b) a first circular diaphragm having a rim portion sealingly secured as by welding to the plate and a relatively thin, flexible, convex portion projecting from one side of the plate and defining a first pressurized gas volume, and (c) a second circular diaphragm having a rim portion sealingly secured as by welding to the plate and a relatively thin, flexible, convex portion projecting from the other side of the plate and defining an independent second pressurized gas volume. The diaphragm assembly can be supported radially inside, outside, or on the weld.

Abstract: The present invention relates to thermally driven pumps. More specifically, one embodiment of the present invention relates to the use of a thermoelectric material to create a thermally driven, bi-directional pump, such as a micro pump, with no moving parts using the thermal transpiration effect (a Knudsen pump). One embodiment of the thermally driven pump of the present invention utilizes a thermoelectric material to assist with the thermal transpiration process resulting in a substantially symmetrical, bidirectional pump. A thermoelectric module is used to induce a temperature gradient across a nanoporous article having at least one nanochannel thus creating fluid flow via thermal transpiration across the nanochannel.

Abstract: A peristaltic pump for use in medical technology with a stator and a rotor. The stator 40 has an occlusion bed 12 which forms the contact area with a tube accommodated within, and the rotor is provided with rolling elements suitable for occluding a tube accommodated between the occlusion bed and the rolling elements. At least a part of the occlusion bed has an electrically conductive surface for reducing and/or preventing electrostatic charging of the tube. The stator may be injection molded from an electrically non-conductive plastic and the electrically conductive surface may be formed by a molded-in metallic insert or a molded-in metallic foil insert.

Abstract: An adhesive dispensing system includes a pump and at least one sensor positioned to sense movements of a component of the pump and produce signals based on the sensed movements. The dispensing system also includes a controller operating the pump and communicating with the at least one sensor to collect information regarding operational cycles of the pump based on the signals. As a result, one or more diagnostic processes are enabled at the controller during operation of the adhesive dispensing system. These diagnostic processes may include a leak rate test for the dispensing system, an overspeed detection test for the pump, and expected life cycle monitoring of the pump or other components.

Abstract: A method for regulating a compressor of a pressure supplying system. The compressor is switched on and off dependent on a threshold temperature of one or more components of the pressure supplying system, the threshold temperature being ascertained using a temperature calculating method. The respective threshold temperature is ascertained by correlating the reciprocal temperature dependence that exists as a result of heat transfer between adjacent components.

Abstract: Detecting a failure mode of a fluid flow controller configured to control fluid flow between first and second chambers of a downhole positive displacement pump and a flow line, wherein the positive displacement pump comprises a piston moving in an axial reciprocating motion, and subsequently adjusting operation of the downhole positive displacement pump based on the detected failure mode such that the downhole positive displacement pump piston operates differently in different axial directions.

Abstract: A pump for use in high pressure liquid chromatography includes a housing with a pump head at one end and an axially-movable, high-pressure piston with a small-diameter plunger reciprocating within the pump head to move fluid from an inlet through an outlet at high pressure. An attached motor rotates a circular cam fixed off center on the motor shaft to reciprocate the piston that has an inner end in engaging contact with the cam periphery. An axially-aligned, torque-compensating piston is provided and has an inner end biased by spring force against the cam opposite the high-pressure piston. A large-diameter piston head may be fixed to the outer end of the torque-compensating piston and slidably mounted within a cylinder defined at the housing end opposite the pump head. The outer end of the piston head is open to ambient atmosphere.

Abstract: Disclosed is an improved segmented fluid end for high-pressure plunger pumps. One segmented fluid end includes one or more fluid end modules, each fluid end module including a body providing a plunger bore configured to receive a plunger therein and a discharge outlet in fluid communication with the plunger bore, wherein a pressurized working fluid may exit the body of each fluid end module via the discharge outlet, a discharge manifold having an elongate manifold body configured to be operatively coupled to each fluid end module, the manifold body providing a first end, a second end, a discharge bore extending between the first and second ends, and one or more discharge inlets that fluidly communicate with the discharge bore, and a ring joint gasket arranged between each discharge inlet of the discharge manifold and a corresponding discharge outlet of the one or more fluid end modules.

Abstract: A system for monitoring wear of pump casing liners is disclosed. The system may include a wear sensor disposed in proximity to the pump casing liner so that the sensor wears at substantially the same rate as the lining. The wear sensor may include a plurality of circuit loops having different lengths. As the pump casing liner and the sensor wear during use, the plurality of circuit loops are sequentially breached. A control system monitors the signals from the plurality of circuit loops to develop liner wear information. This information is employed to signal a user when one or more predetermined wear thresholds are exceeded.

Abstract: An oil pump includes first and second control chambers, a biasing mechanism, and a changeover mechanism. The changeover mechanism connects the first control chamber with a drain portion when a valving element is in a first position, introduces a discharge pressure into the first and second control chambers when the valving element reaches a second position, and drains oil of the second control chamber to the drain portion and introduces the discharge pressure into the first control chamber when the valving element reaches a third position. The changeover mechanism changes from the first position to the second position, when the discharge pressure becomes higher than a pressure level at which the cam ring can move against a set load of the biasing mechanism, and is lower than a pressure level at which a biasing force of the biasing mechanism is increased in a stepwise manner.

Abstract: A device for branching a fluidic partial flow off a main flow by a hydraulic pump (10) includes individual main chambers (12, 14, 16, 18, 20) sealed from each other and divided into functional groups, and operates according to the displacement principle. The chambers enable fluid from at least one main flow inlet (22) to be transported from an inlet or suction side to an outlet or pressure side of the hydraulic pump (10) and then via at least one main flow outlet. At least one independent partial chamber (26) is provided for the transport of the partial flow in addition to the main chambers (12, 14, 16, 18, 20). The partial chamber forms part of the pressure side of the hydraulic pump (10) and is connected to an independent partial current outlet (42) separate from the main flow inlet (22) and the main flow outlet (24).

Abstract: A compressor includes sliding members arranged to slide relative to each other when compressing a refrigerant. At least one of the sliding members has a resin layer that is formed on the whole area or a portion of at least one sliding surface. The resin layer has an arithmetic mean surface roughness (Ra) of 0.3 or more, or the whole area or a portion of an area opposed to the resin layer is entirely or partially harder than the resin layer and has an arithmetic mean surface roughness (Ra) of 0.3 or more.

Abstract: A compressor includes a compression mechanism and a resin layer including a stack of three or more layers formed on a whole area or a portion of at least one surface of at least one part of the compression mechanism. A hardness of a layer most distant from a base in the resin layer is smaller than a hardness of a layer closest to the base in the resin layer. A difference in hardness between two adjacent layers in the resin layer is smaller than a difference in hardness between the layer most distant from the base and the layer closest to the base.

Abstract: A scroll compressor is provided that includes an oil recollecting pump to recollect oil discharged from a shell, thus to effectively recollect oil discharged out of the compressor, and a differential pressure hole formed at a position where it communicates with compression chambers after a suction completion timing, such that oil stored in an inner space of the shell can be supplied into the compression chambers using a pressure difference between a high-pressure inner space of the shell and a low-pressure compression chambers, resulting in allowing oil to be smoothly supplied to a compression unit even during low-speed driving of the compressor and preventing an occurrence of a suction loss due to oil.

Abstract: A scroll compressor includes a fixed scroll and an orbiting scroll. Each of the fixed and orbiting scrolls includes an end plate and a spiral wrap standing on a front surface of the end plate. The scrolls are arranged such that the front surfaces of the end plates face each other and the wraps are engaged with each other. The orbiting scroll eccentrically rotates, without turning on an axis thereof, with respect to the fixed scroll to compress fluid in compression chambers respectively formed inside and outside the wrap of the orbiting scroll. Each wrap is formed in a shape such that at least one of the compression chambers serves as a rate-reduced compression chamber where a volume change rate thereof is reduced in a middle of a compression phase.

Abstract: A motor-driven compressor includes a compression unit, an electric motor, a motor drive circuit, a housing, and a first end plate. The electric motor includes a rotation shaft, a rotor provided with a rotor core, and a stator. The stator includes a state core and a coil. The coil includes first and second coil ends. The rotor core includes a refrigerant passage having a first opening that opens in the compression unit side. The first opening includes a first radially outer region. First and second regions in the housing are in communication through the refrigerant passage. The first end plate includes a first communication port arranged on a first region side end of the rotor core. The first region and the refrigerant passage are in communication through the first opening and first communication port. The first radially outer region is covered by the first end plate.

Abstract: A scroll compressor includes a housing, a fixed scroll, and a movable scroll. A compression chamber is formed between the movable scroll and the fixed scroll. An opposing wall is located in and fixed to the housing. A back pressure region is formed between the opposing wall and the movable scroll, and a back pressure in the back pressure region urges the movable scroll toward the fixed scroll. An annular sealing member is arranged between the movable scroll and the opposing wall. The movable scroll includes a holding portion that holds the sealing member. The sealing member includes a rubber portion, which elastically deforms in the holding portion, and a resin portion, which is made of a material harder than the rubber portion. The resin portion at least partially projects out of the holding portion toward the opposing wall. The resin portion is in contact with the opposing wall.

Abstract: A system in some embodiments includes a machine block comprising features configured to support moving machine components within a lubricating fluid, wherein the machine block includes an integral valve block configured to route the lubricating fluid through a first filter without a second filter and configured to route the lubricating fluid through the second filter without the first filter. Further embodiments include a method that includes switching circulation of a lubricant between a first filter and a second filter in response to an angular position of a valve disposed in a valve block integral to a machine block having moving components lubricated by the lubricant.

Abstract: A pump for pumping molten metal includes a pump shaft having an upper end and a lower end. A motor is connected to the upper end of the shaft. An impeller is fastened to the lower end of the shaft. Support structure supports the motor above the molten metal. A base is disposed below the support structure including an impeller chamber in which the impeller is rotated by activation of the motor. The base includes at least one inlet opening leading to the impeller chamber and at least one outlet passageway leading from the impeller chamber. At least one support post extends between the support structure and the base enabling the base to be submerged in the molten metal beneath the support structure. A device enables the post to resist deterioration while the post is disposed in the molten metal.

Abstract: A cooling system for use in a portable communication device includes a detection module, a cooling module and a central control module. The detection module detects whether the portable communication device is in a communication state and generates an acknowledgement signal. The cooling module includes a fan and a driving unit. The central control module is electrically coupled to the detection module and the driving unit, detects an operational temperature of said device, and generates a detected temperature value corresponding to the detected operational temperature. The central control module controls the fan to operate in a silent mode or a cooling mode. The central control module controls the fan to operate in the silent mode if the central control module receives the acknowledgement signal when the detected temperature value is smaller than a temperature threshold value, else the central control module controls the fan to operate in the cooling mode.

Abstract: A cabin air compressor housing for a cabin air compressor assembly includes a compressor volute configured to direct a compressed flow to a compressor outlet. The cabin air compressor housing also includes a journal bearing support having a journal bearing bore. The cabin air compressor housing further includes an interior portion between the compressor volute and the journal bearing support. The interior portion includes a plurality of cooling airflow holes having a ratio of a diameter of the journal bearing bore to a diameter of one of the cooling airflow holes between 3.64 and 4.52.

Abstract: Methods, devices and systems capable of performing a hot restart of a compressor driven by a turbine are provided. The turbine has a high speed shaft and a low speed shaft connected to the compressor. A base slow roll speed at which a speed of the low speed shaft is in a slow roll range is maintained at the high speed shaft for a predetermined time. Then, when a vibration amplitude of the compressor is larger than a vibration limit, the maintaining is repeated. Otherwise, a set speed of the high speed shaft is increased, until a current speed of the low speed shaft reaches a minimum operating speed. If, while increasing the set speed, the vibration amplitude becomes larger than the vibration limit, the maintaining is repeated.