ITNA20120023A1 - IMPROVED TRADITIONAL WOOD OVEN AND IMPROVED COMBUSTION WITH INNOVATIVE STRUCTURAL TECHNIQUES. - Google Patents

Description

2) DESCRIPTION

TRADITIONAL WOOD-BURNING OVEN WITH IMPROVED SEAL AND COMBUSTION WITH INNOVATIVE STRUCTURAL TECHNIQUES.

The invention distorts the normal operation of the traditional oven (see TABLE 1) in terms of performance with significant increases in combustion and sealing efficiency, finally reducing ignition times thanks to the possibility of closing the control volume (VC TABLE 12) in the transitional phase.

STATE OF THE ART

It should be noted that the present invention applies to the traditional wood-fired oven, where by traditional it is meant that the product (pizza, bread and the like) is cooked in the same combustion chamber, ie directly exposed to the flame. This type of furnace in most cases consists of refractory clay (B TABLE 1 figure 1), expanded clay concrete (A TABLE 1 figure 1), ordinary concrete (C TABLE 1 figure 1) and a layer of sand ( D TABLE 1 figure 1). The peculiar feature of this category of ovens that have been used for centuries is that the combustion chamber is not directly connected to the smoke channel. In fact, the opening of the oven has three different functions: 1. insertion of firewood and products to be cooked; 2. combustion air inlet 3. combustion products outlet

This mixed function involves problems of various kinds which affect the efficiency of the oven and the health of the user. In fact, the products of combustion go up into the smoke channel not because they are attracted by a depression at the base of the chimney, but exclusively because these, being very hot, tend to rise. This involves a limit in the exploitation of the residual heat of the fumes themselves because before entering the smoke duct they mix with the external ambient air (A1, TABLE 1 figure 2), cooling partially. Therefore, in these conditions it is not possible to think of using the heat of the fumes for energy efficiency of the system, since it would run into problems of condensation and difficulty in drafting the chimney.

Another problem that often occurs in the use of these appliances, especially in the transient phase (where the power developed is very high in relation to the initial fuel charge and the combustion products are colder because the heat released is greater), is the diffusion of combustion products in the workplace. These products come out of a combustion that is badly regulated precisely because there is only one opening; this implies that the fumes themselves have a high content of toxic substances.

Another obstacle that prevents a correct use of these appliances is the direct contact of the user with the hot fumes every time he has to insert or remove a product from the oven, bearing in mind that the fumes are at a temperature of about 350 degrees.

In these appliances, food is cooked according to different modes of heat transmission, for example a pizza placed on the cooking surface (P, TABLE 2 figure 4) is cooked by radiation from the flame and the brick dome and by conduction from part of the hob. Since the heat absorbed by conduction is greater than that which the hob is able to recover in steady state, since the latter is not lapped by the hot fumes, there is a continuous drop in the hob temperature which often forces users to temporarily stop production at the order to reinvigorate the top (P, TABLE 2 figure 4).

Finally, as regards the technology of this type of ovens, based on surveys carried out in the main pizzerias in Campania, including the Pizza a Metro in Vico Equense, it emerged that these are made by workers who have handed down the profession from generation to generation. and use materials for the thermal seal that are not suitable for insulation compared to a modern appliance. In fact, the thermal insulation layers are often made up of sea sand, lime and gypsum, materials that have no insulation properties.

The present invention has the purpose of overcoming the following shortcomings of traditional wood-burning ovens:

1. combustion efficiency; 2. reduction of C02 emissions; 3. cooling of the hob; 4. exploitation of the residual heat of the fumes; 5. thermal seal; 6. reduction of risks for users

For correct combustion, approximately 5 m <3> of air (stoichiometric quantity) is required for each kg of wood, which must be increased by approximately 20% due to the non-uniformity of the gas-oxygen mixture. In conditions of natural air circulation, an ordinary appliance can reach acceptable yields because the opening of the combustion chamber only serves to enter the combustion air; in a wood-fired oven the combustion efficiency does not exceed 60% because turbulence develops near the opening which prevents the entry of a sufficient quantity of air (AP, TABLE 1 figure 2). To solve this problem without upsetting the structure of an oven, which has a thousand-year tradition, oxygen injectors have been placed (I, TABLES 2 figure 4, TAVOAL 3 figure 5) near the fire (1, TABLE 5) with the function of blowing air directly onto the flame.

These are connected to a variable flow fan (A, TABLE 2 figure 4) by means of a special regulator, to satisfy the user's needs. This expedient, by improving the combustion efficiency, increases the flow rate of the fumes exiting (F, TABLE 2) from the opening; however, this implies some drawbacks, on the one hand the risk for the user is increased and the probability of the dispersion of fumes (F, TABLE 1 figure 2) in the environment (A1, TABLE 1 figure 2), on the other hand the dwell time of the fumes in the combustion chamber (VC, TABLE 6 figure 12), which will be evacuated at a higher temperature to the detriment of the efficiency of the appliance.

To solve the safety problems for users and exploit the residual heat of the fumes, ejectors (E, TABLE 2 figure 4, TABLE 3 figure 5) are placed in the combustion chamber (fig. 5), on the opposite side of the fire ( 1, TABLE 3 figure 5). These, connected to a collection tank (a, TABLE 3 figure 5), are connected to a second fan (F, TABLE 2 figure 4, TABLE 3 figure 5) and have the function of sucking the fumes and conveying them to a heat exchanger. smoke turns (CF, TABLE 2 figure 4, TABLE 3 figure 6) placed under the top and which will be described in detail below. Therefore this expedient also allows to solve the cooling problem of the top (P, TABLE 2 figure 4).

The suction fan (F, TABLE 2 figure 4, TABLE 3 figure 5) is also adjustable and has a slightly oversized flow rate compared to that of the fumes produced, so as to develop a slight depression near the opening which prevents the flue gases (F, TABLE 1 figure 2) to be released into the environment (A1, TABLE 1 figure 2) and allows users to work in safe conditions.

Thanks to the aforementioned systems, the opening of the combustion chamber (TABLE 1) will no longer have a mixed use but will only be used by the user to insert and extract the dish. This allows a further innovation, that is to use an open combustion chamber appliance as a closed chamber one (in transient). In fact, in the thermal transient the opening can be closed through a special watertight door (TABLE 5) reaching even higher efficiency values.

The exchanger placed under the hob, indicated in TABLE 4 with CF1 ... 4, transfers heat to a layer of material with heat capacity and conductivity such as to constitute a SET (A, TABLE 4 figure 7) for the hob throughout the time of use of the appliance.

To improve the thermal resistance compared to the traditional oven (A, TABLE 1 figure 1) a double insulating layer is installed on the upper casing, of which the first layer (Cl, TABLE 4 figure 7) is made of a material with a thermal capacity very low in order to reduce the duration of the transient (for example dissolved vermiculite), while the second layer (C2, TABLE 4 figure 7) is made of an insulating material with low thermal conductivity (for example glass wool) in order to reduce the transmittance of the casing.

Another innovative aspect consists in placing a double flue with axial symmetry on the forced exhaust of the fumes (EF, TABLE 2 figure 4) such as to form an exchanger (SC, TABLE 2 figure 4), in which the air touches the external surface of the internal flue gas duct before entering the injectors (I, TABLE 2 figure 4, TABLE 3 figure 5) this technique, especially in the initial transient phase, will cause the formation of condensation due to the collapse of the temperature of the fumes, so it is necessary to intervene with a kit condensate collector (RC, TABLE 2 figure 4) as per graphic annex. The natural smoke evacuation system EN, TABLE 2 figure 4) remains unchanged to meet the evacuation needs due to an inadequate adjustment of the system and / or a sudden blackout of the system which, as is known, is one of the problems still unsolved in pellet stove technology.

In traditional wood-fired ovens the door plays a marginal role, since it is not used both in the transitory and in the stationary. In the transient, our door model (TABLE 5) plays a fundamental role that transforms the appliance from an open chamber to a closed chamber; for these reasons it has been designed with a sliding system consisting of: a sliding carriage (1, TABLE 5), upper support rail (6, TABLE 5) and fixed guide rail (8, TABLE 5). Furthermore, it consists of a deflector (7, TABLE 5), a ceramic thermal glass (3, TABLE 5) to sight the combustion, with an air chamber (7, TABLE 5) and finally a sliding handle ( 4, TABLE 5).

As regards the structure of a traditional oven, this is characterized by a strong hyperstaticity (TABLE 1) which causes structural problems (lesions) when the thermal distortion is applied and which constitutes the operating load of the structure; to obviate these drawbacks it was decided to break down the entire structure into three isostatic blocks, whose behavior under the operating load does not induce further interaction stresses between them, but being free to expand, they slide without generating cracking. The aggregative scheme is graphically summarized in the annex in TABLE 2 figure 3 (while the static one in TABLE 4 figure 8). The first block (1, TABLE 2 figure 3) consists of:

1. hollow oblate semi-ellipsoid (A, TABLE 2 figure 3), (consisting of refractory clay bricks with refractory binder)

2. circular crown (B, TABLE 2 figure 3) (with the same characteristics)

3. distribution slab (C, TABLE 2 figure 3) in lightened concrete

The three elements of block 1 are linked together by the internal interlocking constraint (1, TABLE 4 figure 8)

The second block (2, TABLE 2 figure 3) consists of the entire SET package (A, TABLE 4 figure 7), which is placed on steel connectors (2, TABLE 4 figure 7) by means of its base plate . The third block (3, TABLE 2 figure 3) is constituted by the circular spatial trellis with triangular section (3, TABLE 4 figure 8; TRS, TABLE 4 figure 7) which is the support base for the first block and, in the upper internal part , is the fixing base of pendulums (2, TABLE 4 figure 8) that support the plate (4, TABLE 4 figure 8; 1, TABLE 4 figure 7) to which the steel connectors are welded (2, TABLE 4 figure 7) ; this block has the only carrier function.

Claims (10)

CLAIMS TRADITIONAL WOOD-BURNING OVEN WITH IMPROVED SEAL AND COMBUSTION WITH INNOVATIVE STRUCTURAL TECHNIQUES. 1. Traditional wood-fired oven (where traditional means that: 1. the product is cooked in the same combustion chamber, i.e. directly exposed to the flame; 2. the combustion chamber is made entirely of refractory material) with improved combustion with blowing of air (A-l, TABLE 2 figure 4, TABLE 3 figure 5), combustion products suction system (E-F, TABLE 2 figure 4, TABLE 3 figure 5), smoke turns (CF, TABLE 2 figure 4, TABLE 3 figure 6), watertight door (TABLE 5), air preheating system (SC, TABLE 2 figure 4), improved thermal seal (C1-C2, TABLE 4 figure 7), equipped with SET (A, TABLE 4 figure 7) ), control panel (TABLE 6 figure 11) and internally isostatic structure (TABLE 2 figure 3, TABLE 4 figure 8). 2. Oven according to claim 1 characterized in that the blowing of air takes place through a variable number of injectors (I, TABLE 2 figure 4, TABLE 3 figure 5) placed near the fire (1, TABLE 3 figure 5), connected to a fan with adjustable flow rate (A, TABLE 2 figure 4). 3. Oven according to claim 2 characterized in that the combustion products suction system takes place through a variable number of ejectors (E, TABLE 2 figure 4, TABLE 3 figure 5) diametrically opposite to the injectors (I, TABLE 2 figure 4 , TABLE 3 figure 5), connected to an aspirator with adjustable flow rate (F, TABLE 2 figure 4, TABLE 3 figure 5). 4.Oven according to claim 1 characterized in that the smoke turns (CF, TABLE 2 figure 4, TABLE 3 figure 6) are placed under the SET (A, TABLE 4 figure 7) and connected to the extractor (F, TABLE 2 figure 4, TABLE 3 figure 5) on one side and to the air preheating system (SC, TABLE 2 figure 4) on the other. 5. Oven according to claim 1 characterized in that the door (TABLE 5) is watertight and equipped with: sliding system (1-6-8, TABLE 5), deflector (2, TABLE 5), thermal glass (3 , TABLE 5) and double lining with air chamber (7, TABLE 5); and that if it is closed! transitory drastically reduces the times and risks (for health and fire) deriving from ignition. 6. Oven according to claim 1 characterized in that the incoming air is preheated by the heat taken from the exhaust fumes (SC, TABLE 2 figure 4). 7. Oven according to claim 1 characterized by the fact that the thermal seal is guaranteed by two layers with different types of insulation, respectively (from the inside to the outside) with low thermal capacity and low thermal conductivity (C1-C2, TABLE 4 figure 7). 8. Oven according to claim 1 characterized in that the structure consists of mutually isostatic blocks (TABLE 2 figure 3, TABLE 4 figure 8), in particular: by a circular spatial lattice (TRS, TABLE 4 figure 7; 3, TABLE 4 figure 8), from a block that constitutes the SET (A, TABLE 4 figure 7) anchored by means of pendulums (2, TABLE 4 figure 8) and from the upper casing (1, TABLES 2 figure 3; TABLE 4 figure 8) which rests on the trellis (TRS, TABLE 4 figure 7; 3, TABLE 4 figure 8). 9. Oven according to claim 1-8 characterized in that the user can operate in safe conditions against the following risks with respect to the traditional oven (TABLE 1): poisoning, burns, blinding and inhalation of toxic substances. 10. Oven according to claim 1 characterized in that the control panel (TABLE 6 figure 11) consists of: 1. speed regulators of the fumes and air fans (2, TABLE 6 figure 11); 2. a variable number of thermometers (3, TABLE 6 figure 11) to monitor the temperature of the fumes (TF, TABLE 2 figure 4), air (TA, TABLE 2 figure 4), SET (A, TABLE 4 figure 7) and volume control (TABLE 6 figure 12) (TVC, TABLE 2 figure 4); 3. differential magnetothermic switch (1, TABLE 6 figure 11).