RU2249807C1 - Method of operation of diesel - Google Patents

Abstract

FIELD: engine engineering.

SUBSTANCE: method comprises intaking air in the cylinders, injecting fuel into the cylinders, burning the fuel, exhausting combustion products, converting the energy of expanding gases into the reciprocation of pistons between the top and bottom dead centers, and utilizing the heat of exhaust gases. The heat is utilized in the thermocatalytic reactor incorporated into the exhaust system of the engine. The reactor is provided with a hydrocarbon composition with low temperature of dissociation, e.g., methanol. The convertible fuel produced is directed to the cylinders where it is burnt out together with the Diesel fuel. The exhaust gases are additionally heated due to burning the products of incomplete combustion. The incomplete combustion products of the Diesel exhaust are oxidized additionally in the catalytic chamber of the reactor. The heat released is used in the endothermic cycle of the conversion of the hydrocarbon composition.

EFFECT: enhanced efficiency of the Diesel engine.

2 dwg

Description

The invention relates to engine building, and in particular to methods of operating a diesel engine.

Known methods of operation of diesel engines, in which the thermal energy of exhaust gases is utilized, used on powerful (more than 10,000 kW) marine and stationary diesel engines [1, 2]. In this case, the heat of the exhaust gases is used to produce water vapor in a steam generator. Steam energy is then used to drive electric generators, space heating, etc. The systems used for the disposal of exhaust gases have large dimensions and mass, which excludes the possibility of their use on mobile ground means, for example, on cars.

A known method of operation of a car diesel engine, based on the use of thermal energy of exhaust gases to produce steam, followed by the sale of its energy in a recycling circuit operating on the basis of the Rankine cycle (combined cycle) [3].

The main disadvantages of such systems, which hinder the possibility of their implementation, include the large dimensions, the structural and technological complexity of the system that implements the method of utilizing the heat of the exhaust gases, and additional operational costs for the maintenance of the diesel engine. In addition, the diesel mode of operation that implements this idea requires the use of complex control and regulation systems for the utilization circuit.

The basis of the invention is the task of increasing the efficiency of a diesel engine, as well as improving its environmental qualities through the combined use of both thermal and chemical components of the energy potential of diesel exhaust gases.

The essence of the invention lies in the fact that in the method of operation of a diesel engine by introducing air into cylinders, injecting fuel into cylinders, burning fuel, releasing combustion products and converting the energy of expanding gases into reciprocating pistons between the upper and lower points, into a thermocatalytic reactor located in the exhaust system of a diesel engine, a hydrocarbon compound with a low dissociation temperature is fed, for example, methanol obtained during the endothermic conversion of a hydrocarbon compound The gaseous products are sent to diesel cylinders, where they are burned together with diesel fuel, and the thermocatalytic reactor is additionally heated by the chemical energy of incomplete combustion products contained in the exhaust gases, while products of incomplete combustion of diesel exhaust are oxidized in a special catalytic chamber of the reactor (analogue of the catalytic exhaust gas converter), and the released heat is used in the endothermic cycle of the conversion of a hydrocarbon compound.

As a result, the efficiency of the diesel engine is improved due to the utilization of the previously irretrievably lost energy of the exhaust gases and its reuse in the diesel operating cycle to perform useful additional work. In addition, not only the thermal energy of the exhaust gases is utilized, but also their chemical energy due to the afterburning of products of incomplete combustion. The technical result is to increase fuel economy and reduce the toxicity of diesel exhaust gases.

Figure 1 shows the diagram of the diesel engine, where 1 is a thermocatalytic reactor for the conversion of liquid hydrocarbon compounds, installed in the exhaust system of diesel 2, and energy flows carried out in the diesel engine.

The thermocatalytic reactor for the conversion of methanol (or another hydrocarbon compound with a low dissociation temperature) is installed in the exhaust system of the diesel engine and adapts according to its main parameters (productivity, heat exchange surface area, catalyst volume, etc.) with the available energy and temperature capabilities of the exhaust gases of this diesel engine.

Converted fuel (gas hydrogen-containing mixture) is supplied to the diesel working space through the inlet pipe together with an air charge, where it is ignited by a “firing” portion of diesel fuel and, when burned, releases the energy accumulated during its preliminary endothermic conversion.

The optimal coordination of the laws of supply of the main (diesel) fuel and converted can be carried out experimentally.

As can be seen from the diagram of figure 1, the total heat Q ₁ introduced per cycle in diesel engines with diesel and converted fuels, corresponds to:

where n $\genfrac{}{}{0ex}{}{\text{T}}{\text{U}}$ , N $\genfrac{}{}{0ex}{}{\text{K}}{\text{U}}$ and H $\genfrac{}{}{0ex}{}{\text{M}}{\text{U}}$ - heats of combustion of diesel fuel, converted fuel (conversion products) and methanol, respectively;

G _T and G _M - cyclic consumption of diesel fuel and methanol;

ΔН $\genfrac{}{}{0ex}{}{\text{K}}{\text{U}}$ G _M - the additional amount of heat introduced into the cycle due to thermochemical regeneration and due to the difference in the calorific value of the converted fuel and methanol:

ΔН $\genfrac{}{}{0ex}{}{\text{K}}{\text{U}}$ G _M = (H $\genfrac{}{}{0ex}{}{\text{K}}{\text{U}}$ -H $\genfrac{}{}{0ex}{}{\text{M}}{\text{U}}$ ) G _M.

The amount of heat regenerated in the diesel cycle corresponds to the endothermic thermal effect of the dissociation reaction of the cyclic dose of methanol, for the organization of which the thermal energy of an external source is used - the heat carrier (exhaust gases).

The thermal energy of the exhaust gases used to organize the conversion process is defined as the difference in the enthalpies of the gases at the inlet and outlet of the reactor:

where G _ОГ - cyclic flow rate of exhaust gases through the engine;

FROM $\genfrac{}{}{0ex}{}{\text{Exhaust gas}}{\text{R}}$ - the average heat capacity of the exhaust gases in the considered temperature range;

i ' _{exhaust gas} and i' _{exhaust gas} - temperature of exhaust gases at the inlet and outlet of the reactor.

From a joint consideration of dependence (1) and expression (2), it becomes apparent that the amount of heat recovered per cycle

(H $\genfrac{}{}{0ex}{}{\text{K}}{\text{U}}$ -H $\genfrac{}{}{0ex}{}{\text{M}}{\text{U}}$ ) G _M = 4200 G _M , kJ / cycle

depends on the amount of the starting hydrocarbon compound, for example, methanol, which has passed the stage of thermochemical conversion in a thermocatalytic reactor.

Figure 2 shows the temperature field of the experimental methanol conversion reactor, the design of which allows you to use not only the thermal energy of the exhaust gases (heating coolant), but also chemical.

In this design, additional heating of the exhaust gases (coolant) is carried out through the afterburning of the energy-intensive (toxic) products of incomplete combustion (CO, CH) contained in them due to the use of an oxidizing catalytic medium.

For this purpose, a methanol conversion reactor and an exhaust gas catalytic converter are structurally combined in a common apparatus housing. The organization of the exothermic (with the release of heat) process of additional oxidation in the catalytic converter section of the products of incomplete combustion contained in the exhaust gases allows not only to utilize the chemical energy of the fuel that was not realized in the combustion process in the internal combustion engine, but also to improve the environmental qualities of the engine.

The calculated value of the additional thermal effect in this case was determined as:

where H _ui , m _i is the heat of combustion and the mass content in the exhaust gases of the i-th component of incomplete combustion of the fuel, respectively;

G _B , G _M , G _T - mass flow rate through the engine of air, methanol and diesel fuel, respectively.

The process of conversion (conversion) of the initial liquid hydrocarbon compound, for example, methanol, is carried out on the basis of endothermic reactions, that is, with the absorption of heat taken from the exhaust gases of a diesel engine. Therefore, according to Hess's law, the conversion products have a higher calorific value than the calorific value of a liquid hydrocarbon feed, for example methanol.

Thus, part of the diesel exhaust gas energy is used to increase the calorific value of the conversion products, which, when burned in a diesel engine, release this energy to do useful work.

A preliminary energy assessment of the effect of thermochemical regeneration (utilization) of the heat of the exhaust gases of a diesel engine operating in conjunction with a conversion reactor of a hydrocarbon compound, for example methanol, can be quite simply established by comparing the calorific value of the initial liquid hydrocarbon compound, for example, methanol and gaseous products of its dissociation . For example, for methanol, the calorific value is 19670 kJ / kg. Dry methanol conversion products are H ₂ and CO, contained in the conversion mixture in a ratio of 65 vol.% (12.5% by weight) and 35 vol.% (87.5% by weight), respectively. The heat of combustion of this two-component gas mixture is 23870 kJ / kg.

Thus, when 1 kg of methanol conversion products obtained from the same mass of liquid methanol are burned in a diesel engine, additional thermal energy is accumulated during the decomposition of alcohol fuel, equal to Н _{u (pcm) -Н u (m)} = 4200 kJ / kg that is, more than 20% of the energy of the exhaust gases used for the endothermic reaction of methanol conversion is returned to the diesel operating cycle.

The thermochemical essence of the process of regenerating the energy of diesel exhaust gases reflects the main provisions of thermodynamics, in particular, the Hess law and its consequences.

From the above it follows that the preliminary decomposition of liquid hydrocarbons, for example, methanol to power a diesel engine, can improve the efficiency of the diesel engine due to the regeneration of the energy emitted from the exhaust gases. In this case, the diesel workflow is implemented on the basis of a regenerative thermodynamic cycle.

Table 1
Performance indicators of the methanol conversion process for various load conditions of the diesel engine 1CH8, 5/7 Engine operating mode The temperature at the measuring points, ° C (figure 2) The composition of the synthesis gas,% Methanol consumption, l / h n, min ^-1 N _e , kW T ₁ T ₂ T ₃ T ₄ T ₅ T ₆ H ₂ With CO ₂ Residue CH ₃ OH 3000 1.4 25 260 245 240 230 180 24.9 30.1 2.6 42,4 0.2 3000 3.2 28 280 255 345 320 260 53.1 31.1 6.9 5.9 0.2 3000 5.7 thirty 320 270 580 555 395 60.0 38.1 0.4 1,5 0.2

Sources of information

1. Seliverstov V.M. Heat recovery in marine diesel plants. L .: Shipbuilding, 1973. - 256 p.

2. Kokuroshnikov MM Ship recycling facilities. - M.: River transport, 1989 .-- 172 p.

3. Sheypak A.A., Baldin V.P. Utilization steam turbines of automotive tractor internal combustion engines // Automotive industry. - 1985. - No. 12. - S.12-14.

Copyright certificates on the priority of the idea of utilization of thermal energy of exhaust (exhaust) gases of internal combustion engines - analogues:

1. A.S. 1129399 (USSR) Powerplant / Technical College at ZIL and NIKTID. - Authors of the invention: A.A.Sheypak, N.G. Khokhlov, V.P. Baldin and others. 01/28/83; No. 3579507 / 25-06. Publ. in B.I. No. 46, 1984.

2. A.S. 1267030 (USSR). Powerplant / Plant-technical college at ZIL and NIKTID. - Authors of the invention: A.A.Sheypak, N.G. Khokhlov, V.P. Baldin and others. 06/13/84; No. 3751050 / 25-06. Publ. in B.I. No. 40, 1986.

Claims (1)

The method of operation of a diesel engine by intake of air into the cylinders, injection of fuel into the cylinders, combustion of fuel, the release of combustion products and the conversion of the energy of expanding gases into reciprocating pistons between the upper and lower points, the utilization of the heat of the exhaust gases, characterized in that the heat of the exhaust gases carried out in a thermocatalytic reactor located in the exhaust system of the diesel engine, which serves a hydrocarbon compound with a low dissociation temperature, for example, methanol, p the converted fuel is sent to the diesel cylinders, where it burns with diesel fuel, and the exhaust gases are additionally heated by burning the products of incomplete combustion contained in them, while the products of incomplete combustion of the diesel exhaust are oxidized in the catalytic chamber of the reactor, and the heat generated is used in endothermic hydrocarbon conversion cycle.

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