[0001] The present invention relates to a system and method for generating steam in ovens,
which make it possible to improve the injection temperature of water to generate said
steam.
Background of the invention
[0002] Professional ovens are specialised machinery for cooking and processing food with
extensive and very precise control over the internal conditions of the cooking chamber.
These ovens make it possible to control temperature, the stability thereof both at
very low temperatures and at high temperatures, humidity, the heat transfer of steam,
the homogeneous conditions inside the oven, etc.
[0003] Controlling humidity in the cooking chamber is a crucial factor to ensure the correct
preparation of some foods and dishes in modern cooking. Having control over the steam
in the cooking chamber makes it possible to work with very important components of
the final result of the cooked dish, such as juiciness, texture, colour, etc.
[0004] A professional oven must guarantee a very stable and precise control over the humidity
inside, which includes controlling the level, the generation and the extraction of
steam to properly and specifically cook each food. The correct circulation of steam
throughout the interior of the cooking chamber is essential to ensure homogeneous
conditions, or in other words, that all foods will be subjected to the same conditions
for delivering an appropriate and professional result.
[0005] Many modern culinary processes require having control over the level and homogeneity
of the humidity inside the cooking chamber. Therefore, they also require the convection
mechanisms that regulate the concentration of steam and circulation thereof to function
in the most convenient and precise manner possible, without any complications.
[0006] Currently, there are several ways to generate steam in an oven: by means of a boiler,
by direct injection, evaporation, etc.
[0007] One of the most common methods is direct injection, which involves injecting water
either into the centre of the turbine or on one or several points of the blades of
the turbine.
[0008] The injection tube is usually located at a point considered more advantageous or
strategic on the blade, which is where the water precipitates. If the chamber is not
already saturated with steam, more or less steam will be generated depending on the
water inlet temperature.
[0009] Likewise, the injection temperature of water affects the useful life of the turbine:
the lower the difference between its temperature and the temperature of the injected
water, the less thermal shock caused, with which there is a lower likelihood of warping
or imbalances or of the turbine breaking.
[0010] Each manufacturer and model uses different points and tube inclination angles to
try to get the largest amount of steam. Likewise, depending on the degree of humidity
desired and the actual degree of humidity, manufacturers can adjust the flow rate
needed to generate or maintain desired steam levels at the chamber.
[0011] The flow rate of water injected into the oven is generally regulated on a pulsed
basis for a set period of time, with the injection being repeated at the end of each
period, and so on.
[0012] In addition and as a general rule, the solenoid valves are provided with a flow rate
controller that limits the amount of water that is injected, regardless of inlet pressure.
[0013] The steam generation systems used in professional ovens known today generate a limited
amount of steam and their turbines are very likely to deteriorate due to thermal shock.
[0014] Therefore, an object of the present invention is to provide a system for generating
steam in ovens that generates more steam with the same volume of water and in which
the likelihood of deterioration of the turbine due to thermal shock is lower.
Description of the invention
[0015] The system and method of the invention resolve the drawbacks mentioned above and
exhibit other advantages that will be described below.
[0016] According to a first aspect, the present invention relates to a system for generating
steam in ovens, which comprises an injection tube for injecting water into a cooking
chamber of the oven by means of a valve, generating steam in said cooking chamber,
and wherein said injection tube comprises a preheating area where water accumulates
before being injected into the cooking chamber.
[0017] Advantageously, said injection tube also comprises an injection conduit, with the
preheating area being placed between said injection tube and said injection conduit.
[0018] In addition, said preheating area is preferably arranged at a different level with
respect to said injection tube or to said injection conduit.
[0019] Advantageously, said preheating area is located adjacent to a heat-generating zone
of the oven, which preferably comprises at least one resistor or heat exchanger.
[0020] According to three alternative embodiments, said preheating area is a U-shaped portion
where the water accumulates in the lower part of said U-shaped portion; said preheating
area is a bent portion where the water accumulates in the lower part of said bent
portion; or said preheating area is a cavity, where the water accumulates in the lower
part of said cavity.
[0021] According to a second aspect, the present invention relates to a method for generating
steam using the steam generation system described above, which comprises the steps
of:
- determining a water injection flow rate (C);
- determining a water injection regulation flow rate (CREG);
- determining the volume (V) of said preheating area (3);
- calculating the actuation time (WH) of said valve (1) by applying the following formula:

and
- calculating the time (T) between the start of two consecutive water injections by
means of the following formula:

[0022] According to a preferred embodiment, said flow rate (C) is less than or equal to
10 ml/s and said regulation flow rate (C
REG) is also less than or equal to 10 ml/s.
[0023] Consequently, the system and method according to the present invention exhibit at
least the following advantages:
- More steam is generated with the same volume of water.
[0024] With the present invention, more steam is generated in the cooking chamber since
less water is necessary to produce the same amount of steam at a higher water inlet
temperature.
- Lower likelihood of deterioration of the turbine.
[0025] The thermal shock suffered by the turbine of the oven with the preheated water is
lower than the thermal shock suffered with traditional injection systems. As a consequence
of the above, there is less imbalance and a lower likelihood of the turbine breaking.
Brief description of the drawings
[0026] To aid a better understanding of the above, drawings have been attached, in which
a practical embodiment has been schematically represented and only by way of a non-limiting
example.
Figure 1 is a perspective view of a system for generating steam in ovens of the present
invention, according to a first embodiment;
Figure 2 is an elevational view of a part of the water injection tube according to
the embodiment of Figure 1;
Figure 3 is an elevational view of a part of the water injection tube according to
a second embodiment; and
Figure 4 is an elevational view of a part of the water injection tube according to
a third embodiment.
Description of preferred embodiments
[0027] The present invention relates to a system and method which make it possible to improve
the injection temperature of water in an oven for generating steam. This is achieved
through modifications in the injection tube and by adapting both the water injection
time and the injection period between water injections, maintaining the flow rate.
[0028] As shown in Figure 1, the oven comprises at least one injection tube 2, which defines
a preheating area 3, and a cooking chamber 4 such that the water is not injected into
the cooking chamber 4 until the volume of said preheating area 3 is exceeded, as will
be explained below.
[0029] This preheating area 3 is located in a heat-generating zone of the oven, as close
as possible to a convection resistor or heat exchanger of the oven.
[0030] In addition, the oven also comprises a valve 1, such as a solenoid valve, with a
flow rate controller. The outlet of the flow rate controller is connected to the injection
tube 2. When water is injected, this water is stored in the preheating area 3 to increase
its temperature.
[0031] In the following injection, the preheated water will be injected into a turbine 5
of the oven, and cold water will be stored again in the preheating area 3, which will
be heated before being injected, and so on.
[0032] Three possible embodiments of the preheating area 3 defined in the injection tube
2 are shown in the figures.
[0033] In all of these embodiments, the cold water is always in the lower part of the preheating
area 3, while the hot water overflows and is injected into the turbine 5 of the oven
through an injection conduit 6.
[0034] According to a first embodiment, Figure 2 shows that this preheating area 3 is defined
by a U-shaped section, such that the water accumulates in the lower part of said U-shaped
section.
[0035] In the second embodiment, shown in Figure 3, the preheating area 3 is defined by
a bent section that rises between the injection tube 2 and the injection conduit 6,
such that the water accumulates in the lower part of this bent section.
[0036] In the third embodiment, shown in Figure 4, the preheating area 3 is defined by a
cavity or chamber also placed between the injection tube 2 and the injection conduit
6, such that the water accumulates in the lower part of this cavity.
[0037] To preheat the water more effectively, in addition to the preheating area 3 provided
for preheating the water, it is also advisable for a relationship to exist between
the flow rate C, the flow rate controller of the solenoid valve C
REG, the injection time W
H and the period between injections T.
[0038] The first parameter is the water injection flow rate C. This flow rate is usually
between 0 and 10 millilitres per second. The required flow rate is calculated by the
oven control electronics, and is a function of the temperature of the cooking chamber
4, the temperature of a saturation sensor, the amount of food, and other parameters.
[0039] The work cycle C
T is defined as the time during which the solenoid valve is active (W
H), divided by the time during which it is active and inactive (W
H + W
L)

[0040] For example, as the flow rate C is, at most, 10 millilitres per second, and the work
cycle C
T is comprised between 0 and 1, it is clear that C
REG, the flow rate controller of the solenoid valve 1, must also be 10 millilitres per
second.
[0041] Once the required flow rate C has been defined, the work cycle C
T is calculated as

[0042] V is defined as the volume of water housed in the preheating area 3 to determine
the filling in each injection of the volume V of the preheating area. For this to
happen, the solenoid valve 1 is activated with the controller during one W
H such that

is fulfilled.
[0043] Therefore, the W
H value, which causes the volume V to fill completely, is

[0044] Consequently, the work cycle C
T is

where W
L it is the period of time where no injections take place.
[0045] To therefore obtain

[0046] The period between injections T is

[0047] That is, for a required flow rate C, and after setting a value of the flow rate controller
C
REG and a volume V of the preheating area 3, the oven calculates the optimal values W
H and T, which maximise the inlet temperature of the water that is injected while minimising
the time between injections T.

[0048] Example: the flow rate controller of the oven is C
REG = 4 ml/s and the volume V of the preheating area 3 is 20 ml. A flow rate C = 1 ml/s
is required. Therefore:

[0049] The oven will activate the injection solenoid valve 1 for 5 seconds every 20 seconds.
This ensures an increase in temperature of the water that accumulates in the preheating
area 3, and it is not until the following injection that this water, which has already
been preheated, enters the cooking chamber 4.
[0050] Although reference has been made to several specific embodiments of the invention,
it is obvious to a person skilled in the art that the system and the method described
are subject to numerous variations and modifications, and that all the details mentioned
can be replaced by other technically equivalent ones, without departing from the scope
of protection defined by the claims attached hereto.
1. System for generating steam in ovens, which comprises an injection tube (2) for injecting
water into a cooking chamber (4) of the oven by means of a valve (1), generating steam
in said cooking chamber (4), characterised in that said injection tube (2) comprises a preheating area (3) where water accumulates before
being injected into the cooking chamber (4).
2. The system for generating steam in ovens according to claim 1, wherein said injection
tube (2) also comprises an injection conduit (6), with the preheating area (3) being
placed between said injection tube (2) and said injection conduit (6).
3. The system for generating steam in ovens according to claim 2, wherein said preheating
area (3) is arranged at a different level with respect to said injection tube (2)
and/or said injection conduit (6).
4. The system for generating steam in ovens according to any one of the preceding claims,
wherein said preheating area (3) is located adjacent to a heat-generating zone of
the oven.
5. The system for generating steam in ovens according to claim 4, wherein said heat-generating
zone of the oven comprises at least one resistor or heat exchanger.
6. The system for generating steam in ovens according to any one of the preceding claims,
wherein said preheating area (3) is a U-shaped portion, where the water accumulates
in the lower part of said U-shaped portion.
7. The system for generating steam in ovens according to any one of the claims 1 to 5,
wherein said preheating area (3) is a bent portion, where the water accumulates in
the lower part of said bent portion.
8. The system for generating steam in ovens according to any one of the claims 1 to 5,
wherein said preheating area (3) is a cavity, where the water accumulates in the lower
part of said cavity.
9. Method for generating steam using the system for generating steam according to any
one of the preceding claims,
characterised in that it comprises the steps of:
- determining a water injection flow rate (C);
- determining a water injection regulation flow rate (CREG);
- determining the volume (V) of said preheating area (3);
- calculating the actuation time (WH) of said valve (1) by applying the following formula:

and
- calculating the time (T) between the start of two consecutive water injections by
means of the following formula:

10. The method for generating steam according to claim 9, wherein said flow rate (C) is
less than or equal to 10 ml/s.
11. The method for generating steam according to claim 9, wherein said regulation flow
rate (CREG) is less than or equal to 10 ml/s.