Abstract:
In one embodiment of the invention, a method of cleaning a workpiece is disclosed. The method comprises providing a mobile flushing unit and servicing the workpiece as follows: a) connecting a flexible hose of the mobile flushing unit to one end of the workpiece and connecting another flexible hose of the mobile flushing unit to a second end of the workpiece; b) flowing compressed air through each hose and the workpiece; c) pumping a cleaning fluid through each hose and the workpiece for a predetermined amount of time; d) ceasing cleaning fluid flow, followed by purging with air to remove the cleaning fluid from the workpiece; e) pumping water through each hose and the workpiece for a predetermined amount of time; f) ceasing water flow, following by another purge with air to remove the water from the workpiece; and g) disconnecting each hose from the workpiece.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional patent application of co-pending application Ser. No. 10/799,485 filed on Mar. 12, 2004. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to cleaning processes, including those employed in gas turbine engine overhaul processes. More particularly, this invention relates to an apparatus and process for cleaning oil scavenge tubes of a turbine rear frame. 
     BACKGROUND OF THE INVENTION 
     Modern gas turbine engines, such as the General Electric CFM56-5B and -7B with dual annular combustor engines, have been designed to operate both efficiently and with low amounts of pollution emissions. The engines typically include lubrication systems in which lubricating oil is carried externally of the engine in a separate tank or reservoir. In some modern gas turbine engines, the bearing assemblies are lubricated with oil, and heat from the engine parts is absorbed and dissipated by the same oil. It is known to house the engine bearing assemblies in their own respective sumps. The major components of a dry sump lubrication system include a lubricating oil reservoir or tank, a supply pump for supplying lubricating oil from the reservoir to the bearing assembly sumps under pressure and a scavenge pump for removing lubricating oil from the bearing assembly sumps. The scavenge pump causes the return lubrication oil to pass through a heat exchange assembly, on its way to the tank or reservoir. The heat exchange assembly often puts the return lubrication oil in heat exchange with the jet fuel used by the engine. Fuel, on its way to the combustor, enters and passes through the heat exchanger at a much greater flow rate than the oil, so that large quantities of heat are absorbed from the oil by the fuel. Appropriate filter means are also included in the system to remove contaminants from the oil. 
     The system also includes the necessary lubrication and scavenge tubes. The lubrication and scavenge tubes are often secured to the engine cases, frames, ducts, etc. by clamps and brackets. These lubrication and scavenge tubes run from the pumps to the turbine rear frame. 
     A problem sometimes encountered is heavy coking and blocking of the oil scavenge tubes on the turbine rear frame. This problem may be addressed by stripping the turbine rear frame, including the scavenge tube, off of the low pressure turbine module for cleaning, as the scavenge tube cannot be remove or flushed in situ. During this cleaning, the turbine rear frame may be positioned horizontally and the scavenge tube then blocked at one end. Cleaning fluid may then be manually poured into the tube and after an appropriate amount of time the fluid may be eliminated from the tube. This process may be repeated for several hours, even days, until the tube is cleared of the blockage. Although this cleaning process may be effective, it is often costly and time consuming. 
     Accordingly, there exists a need for effective cleaning processes for cleaning tubes, cavities or similar bodies. There is also a particular need for a process and apparatus for cleaning oil scavenge tubes of gas turbine engine components, particularly oil scavenge tubes of a turbine rear frame. The present invention satisfies these needs. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment of the invention, a method of cleaning a workpiece is disclosed. The method comprises providing a mobile flushing unit and servicing the workpiece as follows: connecting a flexible hose of the mobile flushing unit to one end of the workpiece and connecting another flexible hose of the mobile flushing unit to a second end of the workpiece; flowing compressed air through each hose and the workpiece; pumping a cleaning fluid through each hose and the workpiece for a predetermined amount of time; ceasing cleaning fluid flow, followed by purging with air to remove the cleaning fluid from the workpiece; pumping water through each hose and the workpiece for a predetermined amount of time; ceasing water flow, following by another purge with air to remove the water from the workpiece; and disconnecting each hose from the workpiece. 
     In another embodiment of the invention, a mobile flushing unit for cleaning a workpiece is disclosed. The mobile flushing unit comprises the following elements enclosed within a portable device: a first tank for holding a cleaning fluid; a second tank for holding water; flexible hoses for connection to ends of the workpiece; a heater for heating the first tank to a desired temperature; a filtration system to collect debris removed from the workpiece. The unit further comprises an air supply; and a pump, valve and conduit system coupling the elements for selective: connection to and flowing of compressed air through the hoses and the workpiece; pumping of the cleaning fluid through the hoses and the workpiece for a predetermined amount of time; ceasing of cleaning fluid flow, followed by purging with air to remove the cleaning fluid from the workpiece; pumping of water through the hoses and the workpiece for a predetermined amount of time; ceasing of water flow, followed by another purge with air to remove the water from the workpiece. Advantageously, debris removed from the workpiece is collected by a filter of the filtration system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a gas turbine engine having a rear turbine frame and mounted to a pylon below an aircraft wing by an aft engine mount; 
         FIG. 2  is an enlarged cut-away schematic view of a portion of the engine illustrated in  FIG. 1 . 
         FIG. 3  schematically illustrates an embodiment of the present invention; 
         FIG. 4  is a side view of a portion of the apparatus illustrated in  FIG. 3 ; 
         FIG. 5  is a top view of a portion of the apparatus illustrated in  FIG. 3 ; and 
         FIG. 6  is a diagrammatic view illustrating the interconnection of the various elements of an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although the present invention will be described with respect to the cleaning of an oil scavenge tube of a gas turbine engine component rear frame, it is understood that the invention is applicable to clean any suitable workpiece requiring a cleaning. For example, other gas turbine engine components, such as the internal features of blades and vanes, may be cleaned with the processes and apparatuses described herein. Similarly, any other suitable workpiece or component having a cavity in need of such cleaning may be employed. For example, embodiments of the invention may be employed to clean automotive components, including engines and manifolds, among other workpieces. 
     Referring to  FIG. 1 , there is shown a gas turbine engine, generally designated  10 . The engine  10  has a longitudinal centerline A and an annular casing  14  disposed coaxially and concentrically about the centerline A. Air enters the engine  10  in a downstream axial direction F through a forward fan  16  and is then split into fan bypass air AB through a fan bypass  17  and core air AC through a booster compressor  18  (also referred to as the low pressure compressor). A core engine  20  receives the core air from the AC booster compressor  18  and sends it through a multi-stage high pressure compressor  24 , a dual annular combustor  26 , with radially inner and outer rows of fuel injectors  26 A and  26 B, respectively, and a high pressure turbine  28 , either single or multiple stage, all arranged coaxially about the centerline A of the engine  10  in a serial flow relationship. A high pressure shaft  30  fixedly interconnects the high pressure compressor  24  and high pressure turbine  28  of the core engine  20 . The high pressure compressor  24  is rotatably driven by high pressure turbine  28  to compress air entering the core engine  20  to a relatively high pressure. The high pressure air is then mixed with fuel in the combustor  26  and ignited to form a high energy gas stream. This gas stream flows aft and passes through the high pressure turbine  28 , rotatably driving it and the high pressure shaft  30  of the core engine  20  which, in turn, rotatably drives the multi-stage high pressure compressor  24 . 
     The gas stream discharged by the core engine high pressure turbine  28  is expanded through a low pressure turbine, which drives the forward fan  16  and the booster compressor  18  via a low pressure shaft  32  extending forwardly through the annular high pressure shaft  30 . Some thrust is produced by the residual gas stream exiting the core engine  20  through a core engine or primary nozzle  33  aft of low pressure turbine  22 , but most of the thrust power is generated by the forward fan  16 . 
     The low pressure turbine  22  includes an annular rotatable low pressure turbine rotor  34  having a plurality of turbine blade rows  38  extending radially outwardly therefrom and axially spaced from one another. A plurality of stator vane rows  40  are fixedly attached to and extend radially inwardly from the stationary casing  14 . The stator vane rows  40  are axially spaced so as to alternate with the turbine blade rows  38  and define therewith multiple stages of the low pressure turbine  22 . 
     The booster compressor  18  is driven by the low pressure turbine  22  via the low pressure shaft  32 . The booster compressor  18  includes a booster rotor  42  and a plurality of low pressure compressor or booster blade rows  44  fixedly attached to and extending radially outwardly from the booster rotor  42  for rotation therewith. A plurality of booster stator vane rows  46  are fixedly attached to and extend radially outwardly from the booster rotor  42  for rotation therewith. A plurality of booster stator vane rows  46  are fixedly attached to and extend radially inwardly from the stationary casing  14 . Both the booster blade rows  44  and the booster stator vane rows  46  are axially spaced and so arranged to alternated with one another. 
     The booster rotor  42  also supports a fan blade row  48  of the forward fan  16 . The fan blade row  48  is housed within a nacelle  50  of the engine  10  supported about the stationary casing  14  by a plurality of radially extending and circumferentially spaced fan struts  52 . An engine cowling  54 , which encloses the core engine  20  and the low pressure turbine  22  is disposed within and extends coaxially with a rear portion of the nacelle  50  so as to define therewith a fan discharge nozzle  56 . Most of the thrust produced by the engine  10  is generated by air flow caused by rotation of the fan blade row  48  of the forward fan  16 , which air flow passes over and through the nacelle  50 . 
     The low pressure turbine  22  includes an annular rear turbine frame  62 , which supports a conventional bearing  64  which, in turn, rotatably supports an aft end of the low pressure shaft  32 . The rear turbine frame  62  includes a radially outer first structural ring  66  disposed coaxially about the centerline A and a radially inner second structural ring  68 . A plurality of circumferentially spaced apart struts  70  extend radially between the first and second structural rings  66  and  68  and are fixedly joined thereto. Each one of the struts  70  is conventionally surrounded by a conventional fairing  72  for protecting the struts from combustion gases flowing through the turbine frame  62 , as shown in  FIG. 2 . An oil scavenge tube  113  is secured to casing  14 . 
     As also shown in  FIG. 1 , the engine  10  is mounted below an aircraft wing  114  by a pylon  116  at a conventional forward mount  118 , shown in dashed line, and an aft mount  120  spaced axially downstream from the forward mount  118 . The aft mount  120  fixedly joins the rear turbine frame  62  of the engine  10  to a platform  124 , which is fixedly joined to the pylon  116 . The aft mount  120  includes a circumferentially spaced apart conventional first set of U-shaped devises (not shown) on the rear turbine frame  62  connected by a first set of pins  125  to a set of first links (not shown). Each of the first links has second devises connected by a second set of pins to lugs that depend radially inward from the platform (not shown). 
     After extended operation of the gas turbine engine, coking and blocking of the afore-described oil scavenge tubes may occur. Accordingly, it is desirable to periodically clean these tubes. 
     According to embodiments of the present invention, the oil scavenge tubes may be efficiently and economically cleaned to remove the coking and blockage of the tubes. In one embodiment, a mobile flushing unit  200  is provided, as shown in  FIG. 3 . The portable unit  200  may efficiently and economically be used to flush coked scavenged tubes of a turbine rear frame of CFM engines, or others, whether the tubes are built on and remain on the engine or disassembled therefrom, such as by removal of the turbine rear frame from the low pressure turbine. Similarly, unit  200  may be used to clean any other suitable workpiece in need of cleaning. 
     As shown in  FIG. 3 , the unit  200  comprises a trolley  205  for housing the various elements contained therein. Preferably the trolley is made of a stainless steel material and has at least one removable side panel for equipment access. Preferably, the trolley  205  encloses the elements of the apparatus such that any leak will be contained inside the trolley  205  and that no operator may be exposed to any hot internal tank surface. The trolley  205  may be made of any suitable size and shape, and preferably has a plurality of wheels  207  and at least one hand rail  209 , as shown in  FIG. 3 , for ease of mobility. Advantageously, the unit  200  may be easily transported by an operator to the desired cleaning location. The trolley  205  may further include a bump rail  208 , as also shown in  FIG. 3 . While the mobile unit  200  has been described with respect to transport by a trolley  205 , it is understood that other types of transport vehicles may be employed. 
     As shown in  FIG. 3 , the unit  200  further comprises flexible hoses  211  for connection to a scavenge oil tube inlet and outlet. The flexible hoses  211  may be made of any suitable material, including flexible polymeric material. The lengths of the hoses  211  may also be of any suitable length, depending upon, for example, the size of the workpiece to be cleaned and the distance from the unit  200  to the workpiece, as one skilled in the art would recognize. Advantageously, the ends of the hoses  211  may be modified to conform to the particular workpiece in need of cleaning. For example, clamping or other suitable devices may be secured to the ends to create an effective seal. 
     The unit  200  also comprises a first tank  210  for the active cleaning fluid and a water tank  250 , as shown in  FIG. 3 . Preferably, the first tank  210  is a stainless steel tank capable of holding about 25 to about 50 liters or other suitable amount of alkaline material, such as Ardrox 1618 cleaning fluid, or other suitable cleaning fluid. Ardrox 1618 cleaning fluid is an alkaline cleaning solution effective in dissolving carbon and is sold by Chenetal Co. Other suitable cleaning fluids include any conventional cleaning fluids capable of dissolving carbon materials or other materials desired to be removed and may also include acidic cleaning solutions depending upon the desired application. 
     The tank  210  is preferably fitted with a heater  204  and the contents heated to a suitable temperature, which is typically dependent upon the cleaning fluid employed in the tank  210 . For example, the tank  210  preferably may be heated to about 85° C. when Ardrox 1618 alkaline cleaning fluid is employed. Tank  210  may further include a level indicator LI to ensure that the tank  210  is operating at the correct level, a temperature probe (not shown) rated for the desired temperature, a breather  230  with activated filter, such as a charcoal filter, and heater element  204 . 
     Connected to tank  210  is water tank  250 , as also shown in  FIG. 3 . Preferably, water tank  250  is a stainless steel tank capable of holding about 25 liters to about 50 liters of water or other suitable amount. Water tank  250  is preferably fitted with a level indicator LI to ensure correct water level, a breather  260  with activated filter, such as a charcoal filter, and a heater element  259 . 
     As shown in  FIG. 4 , the unit  200  may further comprise a control enclosure panel  400  exposing the various control mechanisms for operation of the unit  200 . Drains  410  and  420  may also be provided on the unit  200  for the draining of cleaning fluid and water, as desired. Similarly, a sump drain  430  may be provided on the unit for use with a sump for effective draining operation. 
     In an embodiment of the invention shown in  FIG. 5 , the unit  200  may comprise a pump  280 , low level sensor LLS, cleaning fluid or auto top up  240 , water top up  270 , electrical supply connection  271 , low level sensor LLS, level indicator LI, compressed air supply connection  202 , in line return filter  200 , thermocouple  199 , heater element  204  and return  203 . 
     As also shown in  FIG. 6 , control solenoid valves  290  may be employed to open/close values to select the cleaning fluid or water. Similarly, control solenoid valves  300  may open/close air purge on the tubes, as desired. A filtration system  310  may collect any debris in the return pipes from the cleaning fluid and water tanks,  210 ,  250 . As also shown in  FIG. 6 , unit  200  may further comprise a header tank  320  with water to top up the tank  210  and water tank  250 . Preferably a PLC computer control system is used to monitor the liquid level in each tank, and monitor the temperature of cleaning fluid and the switch selection from cleaning fluid to water. The interconnection of the various elements of an embodiment of the invention are also set forth in  FIG. 6 , including various level sensors LS, pressure valves PV, safety valves FSV, switches S and header valves HV. 
     The duration of cleaning cycle typically depends upon the amount of build up in the workpiece, as would be recognized by one skilled in the art. For example, a heavily coked oil scavenge tube may require about 1-2 hours of cleaning, whereas a component that is not excessively coked may only require about 15 minutes of the cleaning cycle. A bore scope may be employed to monitor the cleaning process. 
     An embodiment of the present invention will be now described by way of a flow chart example, which is meant to be merely illustrative and therefore not limiting. 
     EXAMPLE 
     
       
         
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Connect unit to 230vac single phase socket by 
               
               
                   
                 13 Amp plug, connect to compressed air supply 
               
               
                   
                 System checks cleaning fluid level and water 
               
               
                   
                 level, level probes provide feed back and auto top 
               
               
                   
                 up operates, if necessary 
               
               
                   
                 Heat up cleaning fluid tank to 85° C., 
               
               
                   
                 temperature probe provides feedback of PLC when 
               
               
                   
                 desired temperature is achieved 
               
               
                   
                 Connect flexible hoses to each end of the 
               
               
                   
                 oil scavenge tube on the aircraft engine (this operation 
               
               
                   
                 may be carried out with use of a fitter to 
               
               
                   
                 ensure correct connection of the fittings) 
               
               
                   
                 System will give an initial air purge to blow 
               
               
                   
                 all lines with clean air and then return valves closes, 
               
               
                   
                 system builds up to 20 psi air pressure, 
               
               
                   
                 and check for any leaks 
               
               
                   
                 Confirm no leaks, and press button on control 
               
               
                   
                 panel to confirm successful test 
               
               
                   
                 Select cleaning fluid on control panel 
               
               
                   
                 and then cycle start 
               
               
                   
                 Cleaning fluid will circulate through lines 
               
               
                   
                 for predetermined period of time 
               
               
                   
                 At end of clean cycle, cleaning fluid valve 
               
               
                   
                 closes and automatic air purges lines to remove as 
               
               
                   
                 much cleaning fluid as possible 
               
               
                   
                 Select water rinse on control panel and 
               
               
                   
                 then cycle start 
               
               
                   
                 Water will circulate through lines for 
               
               
                   
                 predetermined period of time 
               
               
                   
                 At end of clean cycle, water valve closes and 
               
               
                   
                 automatic air purges lines to remove as much 
               
               
                   
                 water as possible 
               
               
                   
                 Disconnect flexible hoses from oil scavenge tube 
               
               
                   
                 on aircraft engine (or tube removed from 
               
               
                   
                 engine) 
               
               
                   
                 Disconnect electric and air supply from trolley 
               
               
                   
                   
               
             
          
         
       
     
     An advantage of embodiments of present invention is providing a portable cleaning apparatus useful in efficiently and cost effectively cleaning tubes, cavities and other openings on various workpieces, included gas turbine engine components. Embodiments of the invention are particularly useful in removing coking and blockage of oil scavenge tubes on turbine rear frames of gas turbine engine components. However, embodiments of the invention may be adapted to clean any component or article requiring such a cleaning operation. Another advantage is that operators also may be readily trained in the automated cleaning process. 
     While various embodiments are described herein, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made by those skilled in the art, and are within the scope of the invention.