Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K25/00—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for
  • F01K25/08—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K17/00—Using steam or condensate extracted or exhausted from steam engine plant
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K21/00—Steam engine plants not otherwise provided for
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16N—LUBRICATING
  • F16N15/00—Lubrication with substances other than oil or grease; Lubrication characterised by the use of particular lubricants in particular apparatus or conditions
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16N—LUBRICATING
  • F16N7/00—Arrangements for supplying oil or unspecified lubricant from a stationary reservoir or the equivalent in or on the machine or member to be lubricated
  • F16N7/30—Arrangements for supplying oil or unspecified lubricant from a stationary reservoir or the equivalent in or on the machine or member to be lubricated the oil being fed or carried along by another fluid

Definitions

• This invention relates to the lubrication of expanders used in closed-circuit vapour power generating systems in which lubricant is soluble in, or miscible with, the working fluid.
• the invention is particularly, but not exclusively, concerned with systems for generating power from moderate or low grade heat sources such as geothermal brines, industrial waste heat sources and internal combustion engine waste heat streams where the maximum temperature for the working fluid of the system is rarely in excess of 15O 0 C.
• Such systems typically use organic working fluids such as tetrafluroethane, chlorotetrafluoroethane 1.1.1.3.3 - Pentafluoropropane or light hydrocarbons such as isoButane, n-Butane, isoPentane, and n-Pentane and operate on the Rankine cycle or some variant of it.
• organic working fluids such as tetrafluroethane, chlorotetrafluoroethane 1.1.1.3.3 - Pentafluoropropane or light hydrocarbons such as isoButane, n-Butane, isoPentane, and n-Pentane and operate on the Rankine cycle or some variant of it.
• a vapour power generating system for generating power by using heat from a source of moderate or low grade heat, comprising a closed circuit for a working fluid, the system including heating means for heating the fluid under pressure at a temperature not usually more than 20O 0 C with heat from the source, a separator for separating the vapour phase of the fluid from the liquid phase thereof, an expander for expanding the vapour to generate power, a condenser for condensing the outlet fluid from the expander, feed pump means for returning condensed fluid from the condenser to the heater and a return path for returning liquid phase from the separator to the heater, wherein the liquid phase contains a lubricant for the bearing which lubricant is soluble or miscible in the liquid phase and a bearing supply path is arranged to deliver liquid phase pressurised by the feed pump means to at least one bearing for a rotary element of the expander.
• the condenser may also initially desuperheat the vapour from the expander.
• the lubricant is dissolved or emulsified with the liquid phase of the working fluid and a proportion of the liquid phase leaving the separator is fed along the bearing supply path to the bearing where heat generated in the bearing evaporates the working fluid, leaving sufficiently concentrated lubricant in the bearing to provide adequate lubrication of the bearing.
• collection spaces are provided around and below the bearing.
• Lubricant leaving the bearing and entering the expander travels to the condenser with the working fluid exhaust from the expander.
• the lubricant again mixes with, or dissolves in, the liquid phase formed in the condenser and returns, via the feed pump, to the heater.
• each bearing supporting the rotary element or elements of the expander is lubricated in this manner.
• the total mass of lubricant required is not more than 5% of the mass of working fluid. Typically 0.5% to 2% is sufficient.
• the expander may be a rotary expander.
• the expander may for example be a turbine of the radial-inflow or axial flow type.
• the expander may be of the twin-screw type.
• the twin-screw type expander is of the lubricated rotor type, the lubricant will be an appropriate oil and some of the mixture of oil and liquid from the separator will be fed into the expander, typically through the normal lubrication port provided for lubricated rotor twin-screw machines or a similar port nearer the high pressure port.
• a vapour power generating system for generating power by using heat from a source of heat, comprising a closed circuit for a working fluid, the system including heating means for heating the fluid under pressure with heat from the source to generate vapour, a plural screw expander for expanding the vapour to generate power, a condenser for condensing the outlet fluid from the expander and feed pump means for returning condensed fluid from the condenser to the heater wherein a bearing supply path is arranged to deliver liquid phase pressurised by the feed pump means to at least one bearing for a rotary element of the expander, and the liquid phase delivered to the at least one bearing contains a lubricant for the expander which lubricant is soluble or miscible in the liquid phase.
• the liquid phase may be delivered from an intermediate point of the heater,
• Figure 1 is a circuit diagram of a vapour power generating system according to the invention
• Figure 2 is a circuit diagram similar to Figure 1 but incorporating a modification
• Figure 3 is a sectional view through the rotor axes of a twin screw expander suitable for use in the circuit of Figure 1 or 2,
• Figure 4 is a longitudinal section on the line IV - IV of Figure 3,
• Figure 5 is a diagram showing the vertical disposition of components of a system similar to those shown in Figures 1 and 2, and
• Figure 6 is a circuit diagram of an alternative embodiment of the invention using a single pass boiler.
• the Organic Rankine Cycle system shown in Figure 1 defines a closed circuit for an organic working fluid having a boiling point at atmospheric pressure below 100 0 C. Up to 5% (usually between 0.5 and 2%) by weight of a compatible natural or synthetic lubricating oil is added to the fluid.
• the circuit comprises a heat exchanger assembly 1 for heating the working fluid in counterflow heat exchange with a hot liquid such as geothermal brine or waste from an industrial source at a temperature up to about 15O 0 C.
• a hot liquid such as geothermal brine or waste from an industrial source at a temperature up to about 15O 0 C.
• the heat exchanger assembly 1 defines a path 2 for the hot fluid from the source, the path 2 extending from an inlet 3 to an outlet 4.
• the assembly also defines a path, extending in counterflow heat exchange with the path 2, through a heater section 5, for heating liquid working fluid, and an evaporator section 6 for evaporating at least some of the working fluid.
• a line 7 leads from the outlet of the evaporator 6 to a separator 8, at a higher level than the heater section 5, for separating the vapour component of the evaporator output from the liquid component.
• Lines 9 and 10 serve to return the hot liquid component to the junction 11 between the heater and evaporator sections 5 and 6.
• a line 12 connects the vapour output of the separator 8 to the inlet 13 of a twin- screw expander 14 for expanding the vapour to a lower pressure and thereby generating power to drive an external load such as an electrical generator G.
• a line 15 leads from the exhaust outlet 16 of the expander to a condenser 17 for condensing the expanded vapour in heat exchange with a cooling fluid flowing through a circuit 18.
• a line 19 connects the liquid outlet of the condenser to a feed pump F for returning the liquid to the heater under pressure through a line 20.
• a line 21 leads from the junction 22 of the lines 9 and 10 to inlets 27, 28 in bearing housings 23, 24 containing bearings for the rotating elements of the expander.
• the bearing housings 23, 24 provide sufficient space around the bearings for the oil content of the liquid working fluid to be concentrated as the working liquid evaporates into the expander as a result of heat generated in the bearings.
• the separator 8 is higher than the heater section 5 (and preferably higher than the evaporator 6), and since the column of liquid in the line 9 is denser than the column of fluid in the evaporator 6 and line 7, there will be continuous circulation through the evaporator section.
• the feed pump F ensures continuous circulation through the heater section 5.
• the line 21 may also be connected, by a line 25, to the normal oil-supply port 26 of the expander.
• the circuit shown in Figure 2 differs from that shown in Figure 1 in that the lubricant-containing liquid tapped off from the junction 11 is cooled, for example from 8O 0 C to 35°C, in a heat exchanger 30, in counterflow with the liquid delivered by the feed pump F to the inlet of the heater section 5.
• the outlet of the feed pump F is connected by a line 31 to the inlet of a pre-heater section 32 of the heat exchanger 30.
• the outlet of the pre-heater section 32 is connected by a line 33 to the inlet of the main heater section 5.
• this flow is taken by a line 34 to the inlet of a cooler section 35 of the heat exchanger to flow therethrough in cooling heat exchange with the liquid in the pre-heater section 32 before being fed by a line 36 to the expander bearings 23, 24.
• the lubricating flow may also be taken to the rotor surface lubrication inlet 37.
• the flow rate delivered to the inlet 37 depends on the working fluid and the operating conditions of the cycle but typically is of the order of two to four times the total flow delivered to the rotor bearings.
• FIGs 3 and 4 show a twin-screw expander suitable for use in the circuits of Figures 1 and 2.
• the expander has a housing 40 containing a helically lobed rotor 41 meshing with a helically grooved rotor 42.
• the rotor profiles, as seen in cross section are of the low friction type having helical involute bands in the region of their pitch circles, being preferably of the type disclosed in EP 0,898,655.
• the rotors 41 and 42 are supported in rolling bearings 43, 44 in the bearing housings 23, 24.
• the rotor 41 has an extension 45 projecting through the bearing housing 24, with a sealing assembly 46, to drive the external load such as the generator G.
• the housing is formed with the rotor surface lubrication inlet 37 in a position just downstream of the vapour inlet 13 to ensure a sufficient pressure drop to provide an adequate lubrication flow.
• the working liquid portion of this flow forms the major part of this flow and is free to vaporise and provide work as it flows through the expander while depositing lubricant on the rotor surfaces.
• the resulting surplus lubricant is carried by the flow of vapour leaving the expander to the condenser and is thus recirculated.
• chlorotetrafluoroethane is a particularly suitable working fluid.
• the condenser 17 is positioned at the highest point in the system and the heater 1 and feed pump are positioned low down. Since the expander 14 is of the positive displacement type (e.g. twin screw expander) which can tolerate the possible presence of liquid droplets in the vapour flow, the separator 8 and liquid return line 9 can be omitted. Instead, the vapour from the evaporator section 6 is supplied by a line 51 to the inlet 13 of the expander 14.
• the positive displacement type e.g. twin screw expander
• the expander inlet 13 is at the bottom at one end and the low pressure vapour outlet 16 is at the top of the expander (in contrast to the orientation shown in figure 4). Although excess oil will tend to be expelled with the vapour into the line 15, residual oil may remain in the expander 14. This will ensure adequate lubrication of the rotor surfaces under all working conditions, and also improve the sealing of the working fluid by filling up the leakage gaps formed by the inevitable clearances between the rotors and between the rotors and the casing with oil.
• the liquid condensed in the condenser 17 is conveyed by a line 19A to a liquid receiver 52 which holds a reservoir of working liquid. Liquid from the receiver 52 is conveyed by a line 19B to the inlet of the feed pump F.
• the hydrostatic head between the condenser 17 and the feed pump reduces or avoids the risk of cavitation in the inlet to the feed pump.
• an oil return line 53 connects an outlet 54 in the bottom of the casing of the expander to the return path from the condenser to the feed pump, in this case being connected to the liquid receiver 52.
• the outlet 54 is positioned just up stream of the main outlet 16 of the screw expander in a position where the pressure is just sufficiently higher than that in the receiver 52 to enable the excess oil to leave the expander.
• the heater 1 preferably a plate-type heat exchanger and the liquid flow to the bearings of the expander may be accumulated in a storage vessel 55 before or after cooling in the heat exchanger 30 and being supplied to the bearing housings 23 and 24 and if necessary to the rotor surface lubricating inlet 26.
• the working fluid is heated in a single pass boiler 60 in which cold liquid enters at the inlet 61 and slightly wet vapour leaves at the exit 62, without internal recirculation through a separator.
• the lubricant e.g. oil contained in the working fluid cannot accumulate in the boiler but is transported by the vapour to enter the expander 14.
• the presence of oil in the working fluid has the effect of raising the saturation temperature of the vapour for a given pressure and this effect can be used to advantage in this embodiment.
• the superheated liquid effectively carries the oil to the rotating parts of the expander and leaves an oil deposit there as expansion proceeds in exactly the same manner as it would, if drawn from the recirculated liquid of a conventional boiler.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Engine Equipment That Uses Special Cycles (AREA)

Applications Claiming Priority (3)

Publications (1)

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Cited By (3)

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• 2006
  • 2006-06-09 EP EP06744192A patent/EP1896698A2/de not_active Withdrawn
  • 2006-06-09 WO PCT/GB2006/002148 patent/WO2006131759A2/en not_active Ceased
  • 2006-06-09 CA CA2610762A patent/CA2610762C/en not_active Expired - Fee Related
  • 2006-06-09 AU AU2006256540A patent/AU2006256540B2/en not_active Ceased
  • 2006-06-09 KR KR1020087000806A patent/KR101342066B1/ko not_active Expired - Fee Related

Non-Patent Citations (1)

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