GB2316631A - Separator for use in a fuel system - Google Patents

Abstract

A separator for a fuel system comprises a housing 20, inlet and outlet ports 26, 24, a sedimenter means 30 and a float valve 36. The sedimenter is arranged to remove high density contaminants, such as water from the fuel and the float valve controls the bleeding of low density contaminants, such as air. The fuel exits via the outlet 24 and is returned to a fuel pump; the low density contaminants being returned to a reservoir and the high density contaminants being drained via tap 40.

Description

SEPARATOR This invention relates to a separator for use in a fuel system in order to separate air, water and other contaminants from fuel.

In a typical fuel system, fuel from a suitable reservoir is drawn through a filter by a pump arrangement including low and high pressure fuel pumps, the low pressure pump being arranged to supply fuel to the high pressure pump which delivers fuel to an associated engine. Some of the fuel which is pumped by the low pressure pump along with leakage fuel mainly from the high pressure pump is returned to the reservoir or to the dirty side of the filter. Where the fuel is returned to the dirty side of the filter, as the filter becomes clogged, in use, where fuel is supplied to the filter under pressure, the pressure of fuel within the pump housing increases which can have an adverse effect on the operation of the timing control of the pump. Rather than return the fuel to the reservoir or dirty side of the filter, it is known to return the fuel to the low pressure pump, by-passing the filter as the fuel has already been filtered.

Such a fuel system is known as a closed loop system.

During the operation of the pump arrangement, air, water and other contaminants may be introduced into the fuel or collect to form pockets of contaminant, and as the returned fuel by-passes the filter, such contaminants may be returned to the low pressure pump where they may reduce the efficiency of and cause damage to the pump arrangement.

It is an object of the invention to provide a separator for use in such a fuel system in order to minimise the disadvantages described hereinbefore.

According to the present invention there is provided a separator comprising a housing, an inlet arranged to receive fuel from a fuel pump, an outlet arranged to supply fuel from the housing to be returned to the fuel pump, sedimenter means for separating relatively high density contaminants from the fuel before the fuel flows to the outlet, and a float valve arrangement arranged to control the bleeding of relatively low density contaminants from the fuel.

The float valve arrangement is conveniently arranged to control the bleeding of contaminants from the housing to a reservoir.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagram illustrating a fuel system; Figure 2 is a sectional diagram of a separator in accordance with an embodiment of the invention; Figures 3 and 4 are diagrams of an alternative arrangement, Figure 4 being a cross-sectional view along the line 4-4 of Figure 3; and Figure 5 is a view similar to Figure 2 of a further alternative.

The fuel system illustrated in Figure 1 comprises a fuel reservoir arranged to contain fuel at relatively low pressure. Fuel from the reservoir 10 is drawn through a sedimenter 12 which is arranged to separate relatively high density contaminants such as water from the flow of fuel under the action of gravity, the sedimenter 12 including a drain plug arrangement whereby the contaminants can be removed from the sedimenter 12 at appropriate intervals. The fuel from the sedimenter 12 is drawn through a filter arrangement 14 including a filter member 16 arranged to remove further contaminants from the fuel which were not removed from the fuel by the sedimenter 12. The outlet of the filter arrangement 14 is connected to the inlet of a fuel pump arrangement 18 which is arranged to draw the fuel from the reservoir 10 through the sedimenter 12 and filter arrangement 14. In an alternative arrangement, a low pressure fuel pump may be provided adjacent the reservoir 10 to supply fuel to the sedimenter 12 and filter arrangement 14.

The pump arrangement 18 takes the form of a housing containing a low pressure fuel pump 18a arranged to supply fuel to a high pressure fuel injection pump 18b. A valve arrangement 1 8c is provided in order to control the pressure of the fuel supplied by the low pressure pump 18a.

In use, the high pressure fuel pump 18k leaks a quantity of fuel into the housing. In addition, a quantity of fuel may be supplied to the housing by the low pressure pump 18a denoted by the restricted path 186 in Figure 1. The housing is provided with an outlet whereby excess fuel within the housing is supplied to a separator 20 an outlet of which is arranged to return fuel to the filter arrangement 14. This fuel supplied to the filter arrangement 14 by-passes the filter member 16 thereof and thus is not filtered by the filter arrangement 14. The separator 20 further includes a connection whereby air separated from the flow of fuel by the separator 20 is returned to the reservoir 10.

Figure 2 illustrates a separator 20 in accordance with an embodiment of the invention. The separator 20 comprises a generally cylindrical housing 22 having an inlet port 24 located adjacent an upper end of the housing 22. The inlet port 24 is arranged to receive fuel from the outlet of the fuel pump housing as described hereinbefore. The lower end of the housing 22 is provided with an outlet port 26 which is arranged to communicate with the outlet of the filter arrangement 14 as described herein before. The outlet port 26 is connected to an upwardly extending passage 28 provided within the housing 22, the upper end of the passage 28 being substantially at the same height as the inlet port 24.

A baffle or cowling arrangement 30 is located within the housing 22 above the end of the passage 28 and defines with the housing 22 a relatively narrow annular flow path through which fuel must flow in order to pass from the inlet port 24 to the outlet port 26. The outer edge of the cowling 30 extends downwardly below the level of the upper end of the passage 28.

The upper end of the housing 22 is provided with a backleak outlet 32 which is connected to a line which communicates with the reservoir 10 as described hereinbefore. The backleak outlet 32 includes a narrow orifice 34 providing a restriction to the flow of air from the housing 22 to the backleak outlet 32. The orifice 34 further defines a valve seating with which a valve member 36 is engageable, the valve member 36 being connected to a float arrangement 38 which is pivotally connected to the upper end of the housing 22, the float arrangement 38 being arranged such that when the level of fuel within the housing 22 falls below a predetermined level, the valve member 36 moves away from its seating to permit the flow of fluid through the orifice 34 to the backleak outlet 32. When the level of fuel within the housing 22 is above the predetermined level, the float arrangement 38 causes the valve member 36 to engage its seating thus preventing the flow of fluid from the housing 32 through the orifice 34 to the backleak outlet 32.

In use, the separator 20 is connected in the fuel system as described hereinbefore. Fuel entering the housing 22 through the inlet port 24 flows over the cowling 30 and along the annular flow path to the lower end of the housing 22. Relatively dense contaminants such as water and dirt carried by the flow of fuel tend to collect in the lower part of the housing 22 whilst the fuel flows upwardly beneath the cowling 30 and flows along the passage 28 to exit the housing 22 through the outlet port 26. At predetermined intervals, the contaminants which collect in the lower end of the housing 22 may be drained therefrom using tap 40 provided in the lower end of the housing 22. Relatively low density contaminants, for example air entering the housing 22 with the flow of fuel tend to be separated from the fuel and collect in the upper part of the housing 22 thus reducing the level of fuel within the housing 22.

After a determined quantity of low density contaminants have collected in the upper part of the housing 22, the level of fuel within the housing 22 will fall below the level at which the valve member 36 is able to leave its seating under the action of the float arrangement 38. Once the valve member 36 no longer engages its seating, the low density contaminants are able to leave the housing 22 through the orifice 34 and backleak outlet 32 to be returned to the reservoir 10. The flow of relatively low density contaminants out of the housing 22 permits the level of fuel within the housing 22 to rise, and a point will be reached at which the float arrangement 38 causes the valve member 36 to engage its seating once more whereafter further flow of low density contaminants through the orifice 34 is prevented.

If the sedimentation area of the housing 22 is approximately 30 cm2, then at a flow rate of 50 litres/hour of fuel through the housing 22, it is expected that particles of diameter approximately 70 pm or more will be removed from the flow of fuel by the separator. Since the float arrangement 38 is sensitive to the density of the materials within the housing 22, and not the pressure therein, the separator 20 is operable independently of the pressure of fuel and contaminants within the housing 22.

In a practical arrangement, in order to prevent fuel from being drawn from the reservoir 10 to the separator 20 via the backleak outlet 32 and orifice 34 for example due to the filter member 16 becoming blocked, a suitable non-return valve may be included in the line connecting the backleak outlet 34 to the reservoir 10. Further, an orifice may be provided in the line connecting the outlet port 26 to the filter arrangement 14 in order to restrict the flow of fuel therethrough, hence ensuring that fuel is drawn by the pump 18 from the reservoir 10 through the sedimenter 12 and to ensure that the pressure within the separator is sufficient to enable the non-return valve to open when the valve member 36 is moved away from its seating to permit air to escape from the separator.

Figures 3 and 4 illustrate an alternative embodiment, and like references are used in Figures 3 and 4 to denote parts which are similar to those of Figure 2. In the arrangement of Figures 3 and 4, the inlet port 24 is provided in the lower surface of the housing 22, the outlet port 26 being adjacent the upper end of the housing 22. In this arrangement the cowling 30 is omitted, and instead an arrangement 43 is provided whereby fuel and any contaminants carried by the fuel flow from the inlet port 24 along a spiral-shaped flow path which promotes sedimentation by providing a relatively high cross-sectional area for the flow of fuel, and hence a low rate of fuel flow, and a relatively high area for sedimentation to occur, relatively dense contaminants carried by the flow of fuel tending to move downwards within the flow of fuel until they reach a lower surface 42 of the sedimenter. The lower surface 42 is provided with a series of openings 44 which permit the contaminants to flow to a lower collection chamber 46 from which the contaminants may be drained at appropriate intervals using the tap 40. The fuel exits the sedimenter through an outlet 43a at the upper end of the sedimenter, the fuel flowing through a chamber 47 which promotes the separation of relatively low density contaminants, for example air, from the flow of fuel, the low density contaminants tending to collect in the chamber 47 whilst the fuel is permitted to flow from the housing 22 through the outlet port 26.

A float valve arrangement 38 is provided in the chamber 47. The float valve arrangement comprises a valve member 36 which is engageable with a seating defined around an orifice 34, the valve member 36 being carried by a float 38 which is captive within guide means 39 connected to the upper end of the housing 22, the guide means 39 permitting the float 38 to move in a vertical direction thereby permitting the valve member 36 to move between a position in which it engages its seating and a position in which it is spaced from its seating, but restricting lateral movement of the float 38 and hence the valve element 36.

Operation of this arrangement is similar to that described herein before and will not be described in detail.

The arrangement illustrated in Figure 5 comprises a housing 22 of substantially square cross-section, an inlet port 24 being provided in the lower surface of the housing 22. A cowling 30 is provided within the housing 22 in order to separate the housing 22 into a sedimenter region which promotes the separation of high density contaminants from the fuel, the contaminants tending to collect in the lower part of the housing 22 from which they may be removed using tap 40. The cowling 30 further defines a flow path to an outlet port 26 also provided in the lower surface of the housing 22, the flow path requiring the fuel to flow from the inlet port 24 in the lower surface of the housing 22 to an upper part of the housing 22 and from there back to the lower part of the housing 22 to exit through the outlet port 26.

Adjacent the upper surface of the housing 22, a backleak outlet port 32 is provided, the connection of the port 32 with the housing 22 including an orifice 34 defining a seating with which a valve member 36 is engageable, the position of the valve member 36 being controlled by a float arrangement 38 which is pivoted to a side wall of the housing 22, operation of the float arrangement 38 to control the position of the valve member 36 being similar to that described with reference to Figure 2.

A tubular extension 26a extends upwardly from the outlet port 26 and defines an annular collection chamber 26b arranged to collect further contaminants which are separated from the flow of fuel after passing the outlet port 32. In order to restrict the flow of such contaminants through the outlet port 26, the cowling 30 includes a projection 30a.

Each of the embodiments described hereinbefore is advantageous in that contaminants which are introduced into the flow of fuel by the pump arrangement 18 can be separated from the flow of fuel before the fuel returned to the inlet of the pump arrangement 18 thus reducing any inefficiencies and damage which would otherwise be caused by the presence of such contaminants being returned to the pump inlet.

Claims (4)

1. A separator comprising a housing, an inlet arranged to receive fuel from a fuel pump, an outlet whereby fuel from the housing can be returned to the fuel pump, sedimenter means for separating relatively high density contaminants from the fuel before the fuel flows to the outlet, and a float valve arrangement arranged to control bleeding of relatively low density contaminants from the housing.

2. A separator as claimed in Claim 1, wherein the float valve arrangement controls the bleeding of contaminants from the housing to a reservoir.

3. A separator as claimed in Claim 1 or Claim 2, wherein the float valve arrangement is arranged to permit such bleeding when the fuel level within the housing falls below a predetermined level.

4. A separator substantially as hereinbefore described with reference to Figure 2 or Figures 3 and 4 or Figure 5 of the accompanying drawings.