GB2574325A

GB2574325A - Gas boiler intake system

Info

Publication number: GB2574325A
Application number: GB1907515.9A
Authority: GB
Inventors: W T Parsons Robert
Original assignee: Ideal Boilers Ltd
Current assignee: Ideal Boilers Ltd
Priority date: 2018-05-30
Filing date: 2019-05-28
Publication date: 2019-12-04
Anticipated expiration: 2039-05-28
Also published as: GB201907515D0; GB2574325B; GB201808817D0

Abstract

A gas boiler intake system (1) includes an air intake (2), a gas intake (3) and a Venturi (4). The air intake (2) is arranged adjacent to the gas intake (3) such that, in use, combustion air is directed through the air intake (2) before inducing gas at the gas intake (3). The gas intake projects into the Venturi (4). The intake system uses frictional resistance of air flow through a Venturi to dampen pressure pulsation oscillations which may be caused by lean combustion conditions.

Description

Gas Boiler Intake System

The present invention relates to a gas boiler intake system, and to gas boiler systems and methods relating thereto.

Gas boilers have been used for many years to provide heating for various processes and applications, such as heating homes and commercial establishments.

Over the years, gas boiler technology has significantly advanced. Modern gas boilers include a number of useful features and operational modes, e.g. means for automation and improving safety.

Gas boilers are typically fuelled by a mixture of air and gas. In use, when a low heating demand is required a gas boiler may be configured to operate in a lean burn mode, which involves modulating the burner of the boiler to a minimum heating rate, which progressively decreases the proportion of gas in the air/gas mixture.

At the lean operating limit of a burner of a gas boiler the flame stability of the burner can be impaired. This impairment can result in pressure oscillations upstream of the flame which interrupt and perturb the equilibrium gas pressure. This can result in a loss of control over the air to gas ratio and thus further instability or even failure of the flame.

The present invention has been made in consideration of these issues.

According to a first aspect of the present invention, there is provided a gas boiler intake system comprising an air intake, a gas intake and a Venturi, wherein the air intake is arranged adjacent the gas intake such that, in use, combustion air is directed through the air intake before inducing gas at the gas intake, wherein the gas intake projects into the Venturi.

In use, a volume of combustion air is enclosed in the air intake before being directed to the gas intake. The enclosed combustion air (and the air intake) provides frictional resistance against, and reduces the magnitude of, any pressure oscillations that occur as a result of combustion of gas in a lean mixture of air and gas (referred to herein as 'lean mixture'). Thus, the gas boiler intake system provides inertia to a gas boiler system by opposing such pressure oscillations.

Accordingly, the gas boiler intake system stabilises oscillations in pressure at the gas intake that could otherwise occur from combustion of gas in a lean mixture. The gas boiler intake system thus enables a gas boiler to better operate using lean mixtures (e.g. those supplied in Europe). Therefore, the gas boiler intake system can improve the flame stability and performance of a gas boiler.

Additionally, as the gas boiler intake system facilitates combustion of lean mixtures it can accommodate a wider calorific value range of natural gas. This also allows a gas boiler to operate for an extended period of time in a lean burn mode (i.e. combustion of gas in a lean mixture) which can reduce carbon monoxide and nitrous oxide emissions and thereby improve the environmental profile of a gas boiler. Furthermore, this also allows a gas boiler to operate over a wider modulating range of the gas boiler to satisfy the heating requirements of low energy housing.

Furthermore, as the gas boiler intake system stabilises pressure oscillations a wider heat delivery range is possible. This also allows for the gas to combustion air ratio to be adjusted to provide a leaner mixture for combustion, to thereby reduce emissions (e.g. of carbon monoxide and nitrogen oxide gasses). This improves the environmental profile of a gas boiler.

Moreover, by optimisation of the gas boiler intake system, combustion stability close to the theoretical limit (maximum theoretical efficiency) is possible.

'Combustion air' refers to air supplied for use in the combustion of gas by a gas boiler.

'Gas' refers to any gas suitable for combustion by a gas boiler. For example, the gas may comprise hydrocarbons (such as methane, ethane, propane, butane, or mixtures thereof), hydrogen, carbon monoxide, or mixtures thereof.

'Lean mixture' refers to a mixture of air and gas with an excess of air. As a person skilled in the art will appreciate, the composition of the lean mixture may vary considerably from one application to another.

The gas boiler intake system comprises a Venturi. The Venturi may be defined as a tube having a constriction that causes an increase in the velocity of flow of a fluid and a corresponding decrease in fluid pressure. The Venturi may comprise a tube having a tapering constriction. The tapering constriction may be disposed towards one end of the Venturi. The Venturi may be arranged so as to envelop the gas intake.

In use, when the combustion air is directed from the air intake, through the throat of the Venturi, to the gas intake, the gas from the gas intake is induced into the Venturi for mixing with the combustion air. This further stabilises any oscillations in pressure at the gas intake.

The air intake may be arranged adjacent the gas intake such that, in use, combustion air is directed through the air intake before inducing gas at the gas intake.

The gas intake projects into the Venturi. The gas intake may project into the tapering constriction of the Venturi. In this arrangement, there is particularly effective gas induction and stabilisation of pressure oscillations.

In use, when the gas intake projects into the Venturi, gas exiting the gas intake is located in a region of high velocity airflow (i.e. accelerating in the direction of the burner). This high velocity airflow provides resistance against any pressure oscillations (e.g. those originating downstream at the burner). This increases the stability of the flame at the burner.

In particular, in use, when the gas intake projects into the tapering constriction of the Venturi (i.e. where airflow is at a maximum velocity), gas exiting the gas intake is located in a region of optimum velocity airflow (i.e. where the velocity is maximised). This provides further resistance against any pressure oscillations, such that the equilibrium gas pressure at the gas inlet is further stabilised. This further increases the stability of the flame at the burner.

The gas boiler intake system may take the form of an elongate structure tapering at one end. The gas boiler intake system may take the form of a substantially frustoconical structure.

The gas boiler intake system may comprise an inner surface, wherein the inner surface and the outer surface of the Venturi may define the air intake. In this way, the inner surface may be arranged so as to envelop the Venturi.

The inner surface may take the form of an elongate structure tapering at one end. The inner surface may take the form of a substantially frustoconical structure.

In use, combustion air can be directed through air intake (defined by the inner surface and the outer surface of the Venturi) before entering the inside of the Venturi, via its tapering constriction, and inducing gas at the gas intake.

The air intake may comprise one or more channels. One or more or each of the channels may be suitable for directing combustion air to the gas intake. The one or more channels may comprise one, two, three, four, five, or six channels.

The air intake may comprise an intake manifold. The intake manifold may be arranged in fluid communication with one or more or each of the channels. The intake manifold may be arranged in sealable engagement with one or more or each of the channels. The intake manifold may be arranged in sealable engagement with the Venturi.

In use, the combustion air can be directed through one or more or each of the channels and intake manifold before entering the inside of the Venturi, via its tapering constriction, and inducing gas at the gas intake.

Without being bound by theory, by allowing the combustion air to be directed through the air intake before inducing the gas at the gas intake, the combustion air reaching the gas intake is considered to be characterised by a more laminar flow profile.

The present invention provides a means of improving flame stability in and performance of a gas boiler. The present invention provides a means of improving the environmental profile of a gas boiler. The present invention can improve the lean operating point of a gas boiler. The present invention can enable a gas boiler to operate using lean mixtures. The present invention allows the gas boiler to operate over a wider modulating range to match the heating requirement of low energy housing.

Moreover, as a person skilled in the art will appreciate, the gas boiler intake system may be used in combination with existing boiler componentry without impairment of performance.

The aforementioned statements of suitable features and advantages of the first aspect apply to any other aspect as described herein, without departing from the scope of the present teachings, whether explicit or implicit herein.

According to another aspect of the present invention, there is provided a gas boiler system comprising a gas boiler connected to a gas boiler intake system according to the first aspect.

The gas boiler may comprise a burner.

The gas boiler may comprise a heat exchanger.

The gas boiler may comprise a gas supply means operable to supply gas.

The gas boiler may comprise any other suitable component of a gas boiler as will be known to a person skilled in the art.

According to yet another aspect of the present invention, there is provided a method of stabilising an oscillation in pressure resulting from combustion by a gas boiler of gas in a lean mixture, the method comprising:

a) providing a gas boiler intake system according to the first aspect;

b) providing a gas boiler;

c) connecting the gas boiler intake system to the gas boiler; and

d) operating the gas boiler.

Suitably, step a) occurs before step b), step b) occurs before step c), and step c) occurs before step d).

In order that the invention may be more clearly understood, specific embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 shows a cross sectional view of a gas boiler intake system according to a first embodiment;

Fig. 2 shows a cross sectional perspective view of the gas boiler intake system of Fig. 1; and

Fig. 3 shows a plan view of a gas boiler intake system according to a second embodiment, where the system is connected to a fan and burner arrangement.

Fig. 4 shows a plan view of the gas boiler intake system of Fig 3., showing only the components in immediate contact with the gas boiler intake system.

Fig. 5 shows a plan view of the gas boiler intake system of Fig 3., where the system is connected to a complete heat engine (rather than to the fan and burner arrangement in Figs. 3 and 4).

Referring to Figs. 1 and 2, a gas boiler intake system 1 comprises an air intake 2, a gas intake 3 and a Venturi 4.

The gas intake 3 comprises a gas supply nozzle 6 and an injector 7. The injector is operable to inject gas into the Venturi 4.

The Venturi 4 comprises a Venturi inlet 4a and a Venturi outlet 4b. The Venturi 4 is of the form of an elongate tube having a tapering constriction arranged towards the Venturi inlet 4a. The diameter of the Venturi inlet 4a is smaller than the diameter of the Venturi outlet 4b.

The gas boiler intake system comprises an inner surface 5 having a substantially frustoconical hollow structure which is closed at its narrower end and open at its wider end. The inner surface 5 envelops the Venturi 4, such that the closed end of the inner surface 5 is adjacent the Venturi inlet 4a, and the Venturi outlet 4b projects outwardly from the open end of the inner surface 5.

In this way, the air intake 2 is defined by the inner surface 5 of the gas boiler intake system 1 and an outer surface of the Venturi 4.

The gas intake 3 is fixedly mounted at the closed end of the inner surface 5, such that the injector 7 projects through the Venturi inlet 4a and into the Venturi 4, in parallel with the longitudinal axis of the Venturi 4.

Accordingly, the cross section of the gas boiler intake system 1 includes two substantially concentric circles, the inner concentric circle defined by of the Venturi 4, and the outer concentric circle defined by the inner surface 5.

In use, combustion air is directed through the air intake 2 (defined by the inner surface 5 and the outer surface of the Venturi 4) via an opening defined between the open end of the inner surface 5 and the Venturi outlet 4b, then through the Venturi inlet 4a into the Venturi 5 where it induces gas at the injector 7. This forms a combustion mixture of air and gas which is directed to a burner of a gas boiler for combustion. The flame front of the combustion mixture is located at a burner skin formed by an interface between the burner and a heat exchanger of the gas boiler. Flame instability often occurs at the burner skin causing oscillations in pressure within the burner and Venturi 4, which in extreme cases can cause combustion failure. The gas boiler intake system 1 stabilises such oscillations in pressure.

Referring to Figs. 3 and 4, a gas boiler intake system 1 comprises an air intake 2, a gas intake 3 (numbering not shown for clarity) and a Venturi 4.

The gas boiler intake system 1 is connected to a gas boiler 100 comprising a burner 101, a heat exchanger 102 and fan arrangement 103.

The air intake 2 comprises two air intake ducts 2a, 2b, and an intake manifold 2c. The intake manifold 2c comprises a substantially rectangular cuboid structure, but the skilled person will appreciate that it may take other forms. The intake manifold 2c ensures that incoming combustion air is drawn through the air intake ducts 2a, 2b. Each of the air intake ducts 2a, 2b is of a substantially circular cross section and comprises an air inlet and an air outlet. Each of the air outlets of the intake ducts 2a, 2b is arranged in sealable engagement with an opposite side the intake manifold 2c.

The gas intake 3 is operable to supply gas and comprises a gas supply nozzle 6 and an injector 7. The injector 7 is arranged at the throat of the Venturi 4. The air pressure generated at the throat at the Venturi 4 induces gas flow from the injector

7.

One end of the Venturi inlet 4a is arranged in sealable engagement with a side of the intake manifold 2c between the sides to which the air outlets of the intake ducts 2a, 2b are engaged. The other end of the Venturi 4b is releasably attached to a fan arrangement 103 by means of a bayonet connection.

The gas intake 3 is fixedly mounted on the intake manifold 2c, at the same side of the intake manifold 2c as the Venturi 4, such that the injector 7 projects outward from the intake manifold 2c and into the tapering constriction of the Venturi 4, in parallel with the longitudinal axis of the Venturi 4. In this way, the Venturi 4 envelops the injector 7.

The gas intake 2 is connected to a gas supply means operable to supply gas for combustion. The gas supply means projects through a side of the intake manifold 2c opposing the side on which the gas intake 3 is mounted, and is arranged in sealable engagement with the gas intake 3. .

Referring to Fig. 5, a gas boiler intake system 1 of the second embodiment, having the same components as described in relation to Figs. 3 and 4, is connected to a complete heat engine. The engine comprises a burner 101, a heat exchanger 102 and a fan arrangement 103.

In use, combustion air is directed through the air intake ducts 2a, 2b, then through the intake manifold 2c, then through the Venturi inlet 4a into the Venturi 5 where it induces gas at the injector 7 (i.e. inside the Venturi 4). This forms a combustion mixture which, in use, is directed to the burner 101 of the gas boiler 100. The flame front of the combustion mixture is located at a burner skin 103 formed at an interface between the burner 101 and the heat exchanger 102. Flame instability often occurs at the burner skin 103 causing oscillations in pressure between the burner 101 and the Venturi 4. In extreme cases this can cause combustion failure. The gas boiler intake system 1 stabilises such oscillations in pressure.

The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.

Claims

1. A gas boiler intake system comprising an air intake, a gas intake and a Venturi, wherein the air intake is arranged adjacent the gas intake such that, in use, combustion air is directed through the air intake before inducing gas at the gas intake, wherein the gas intake projects into the Venturi.

2. A gas boiler intake system as claimed in claim 1 wherein the gas comprises hydrocarbons, hydrogen, carbon monoxide, or mixtures thereof.

3. A gas boiler intake system as claimed in any preceding claim wherein the Venturi comprises a tube having a tapering constriction.

4. A gas boiler intake system as claimed in claim 3 wherein the tapering constriction is disposed towards one end of the Venturi.

5. A gas boiler intake system as claimed in any preceding claim wherein the Venturi envelops the gas intake.

6. A gas boiler intake system as claimed in any preceding claim when dependent on claim 3 wherein the gas intake projects into the tapering constriction of the Venturi.

7. A gas boiler intake system as claimed in any preceding claim wherein the gas boiler intake system takes the form of an elongate structure tapering at one end.

8. A gas boiler intake system as claimed in any preceding claim wherein the gas boiler intake system takes the form of a substantially frustoconical structure.

9. A gas boiler intake system as claimed in any preceding claim wherein the gas boiler intake system comprises an inner surface, wherein the inner surface and the outer surface of the Venturi define the air intake.

10. A gas boiler intake system as claimed in claim 9 wherein the inner surface is arranged so as to envelop the Venturi.

11. A gas boiler intake system as claimed in claim 9 or 10 wherein the inner surface takes the form of an elongate structure tapering at one end.

12. A gas boiler intake system as claimed in any of claims 9 to 11 wherein the inner surface takes the form of a substantially frustoconical structure.

13. A gas boiler intake system as claimed in any of claims 9 to 12 wherein, in use, the combustion air is directed through air intake, before entering the inside of the Venturi, via its tapering constriction, and inducing gas at the gas intake.

14. A gas boiler intake system as claimed in any of claims 1 to 6 wherein the air intake comprises one or more channels.

15. A gas boiler intake system as claimed in claim 14 wherein the air intake comprises one, two, three, four, five or six channels.

16. A gas boiler intake system as claimed in claim 14 or 15 wherein the air intake comprises an intake manifold arranged in fluid communication with one or more or each of the channels.

17. A gas boiler intake system as claimed in claim 16 wherein, in use, the combustion air is directed through one or more or each of the channels and intake manifold before entering the inside of the Venturi, via its tapering constriction, and inducing gas at the gas intake.

18. A gas boiler system comprising a gas boiler connected to a gas boiler intake system as claimed in any preceding claim.

5

19. A gas boiler system as claimed in claim 18 wherein the gas boiler comprises a burner.

20. A gas boiler system as claimed in claim 18 or 19 wherein the gas boiler comprises a heat exchanger.

21. A gas boiler system as claimed in any of claims 18 to 20 wherein the gas boiler 10 comprises a gas supply means operable to supply gas.

22. A method of stabilising an oscillation in pressure resulting from combustion by a gas boiler of gas in a lean mixture, the method comprising:

a) providing a gas boiler intake system as claimed in any of claims 1 to 17;

b) providing a gas boiler;

15 c) connecting the gas boiler intake system to the gas boiler; and

d) operating the gas boiler.

23. A method as claimed in claim 22, wherein step a) occurs before step b), step b) occurs before step c), and step c) occurs before step d).