WO2017091098A1

WO2017091098A1 - Internal combustion engine operation method

Info

Publication number: WO2017091098A1
Application number: PCT/RU2015/000815
Authority: WO
Inventors: Борис Львович ЕГОРОВ
Original assignee: Борис Львович ЕГОРОВ
Priority date: 2015-11-24
Filing date: 2015-11-24
Publication date: 2017-06-01

Abstract

Operation method of a two-stroke internal combustion engine. Near-isothermal compression is carried out in a separate screw compressor with an injection of a cooling liquid. The heat of exhaust gases is used to heat a compressed working medium to a fuel auto-ignition temperature. At the end of an exhaust stroke, a specific quantity of the exhaust gases is compressed. During compression of the exhaust gases, an initial fuel injection is carried out with a specific advance angle. The engine power is adjusted by proportionally reducing the intake phase, the quantity of fuel taken in, and the compressor capacity.

Description

The method of operation of the internal combustion engine

Field of Invention

The invention relates to engine

BACKGROUND OF THE INVENTION

Two-stroke internal combustion engines are known in which the compression of the working fluid was carried out in a separate compressor, and the supply of thermal energy and

expansion directly in the engine cylinder. In this case, as a rule,

it was proposed to compress in a separate cylinder, that is, almost almost adiabatically. Due to the increase in thermal and gas-dynamic losses, this method of operation did not lead to an increase in efficiency compared to internal combustion engines operating on the Otto or Diesel cycle. One of the main disadvantages of the above type of engine is the loss during the flow of the working fluid into the cylinders of the expansion machine

increase with increasing engine speed. This is due to the fact that in known analogous methods, after the expansion stroke, the working fluid is completely pushed out of the cylinder by the piston and remains only in the so-called dead space formed by the piston crown and the head of the block. The pressure in the dead space at the time of opening the intake valve is close to atmospheric and at the inlet, the compressed working fluid is throttled, since the valve opens gradually, and the volume of dead space will be significant in any case. With increasing engine speed, the working fluid will not have time to fill in the dead space with a given pressure when the piston is in TDC and to compensate for the increase in the space above the piston when the piston moves down. Since the inlet of the working fluid with this method begins at the moment when the piston reaches TDC, fuel injection and combustion can be carried out only after TDC. Given the delay in fuel ignition, the active phase of combustion can begin at a high speed only after 20-30 ° of crankshaft rotation after TDC. Such late ignition leads to incomplete combustion of the fuel, loss of efficiency and increase of harmful emissions in the exhaust gases.

Closest to the proposed method are engine operating methods described in US Pat. No. 4,040,400, publication date: 08/09/1977 and RU 2246625 publication date: 05/20/2005, as well as in the author's application PCT / RU2015 / 000010. The methods of operation described in these patents provide for isothermal compression followed by heating the compressed working fluid with exhaust gases, but compression is proposed to be carried out in a reciprocating multistage compressor with intermediate cooling. The compression polytropic compression piston compressor averages 1.3, i.e. closer to the adiabat, and intermediate cooling does not reduce the compression work. The thermodynamic effect of applying compression with intermediate cooling and subsequent heating of the compressed working fluid with exhaust gases will still be, but it will be less significant. Given the low volume and

mechanical efficiency of reciprocating multistage compressors this effect will be minimized or zero. A significant increase in the thermodynamic efficiency of the method of engine operation with compression in a separate compressor, and by applying heat and expanding directly in the cylinder, can be achieved only by applying compression that is as close to isothermal as possible, using thermal energy

exhaust gases for subsequent heating of the compressed working fluid to a temperature of self-ignition and to minimize mechanical losses during implementation.

For effective compression in a separate compressor, the polytropic compression should be close to 1.1 in real conditions and it is preferable to carry out the entire compression process in one step with minimal mechanical losses and high volumetric efficiency. Also, in these methods, at the inlet of the working fluid into the expansion cylinder, throttling will occur, which reduces the efficiency of the engine. And later ignition due to fuel injection after TDC will reduce

fuel combustion efficiency and increase harmful emissions, especially at medium and high speeds.

SUMMARY OF THE INVENTION

The main goal of the proposed method is to increase the efficiency of a two-stroke internal combustion engine with external compression due to a more efficient use of the thermodynamic cycle with isothermal compression and regeneration of thermal energy of the exhaust gases, as well as by optimizing the processes of intake of the working fluid and fuel combustion.

The theoretical thermodynamic cycle of the proposed method of operation includes: isothermal compression - regenerative heat supply - isobaric (isochoric-isobaric) heat supply - adiabatic expansion - isochoric (isobaric) heat removal. The theoretical efficiency of the proposed cycle, provided that the exhaust heat is perfectly regenerated, will be as close as possible to the efficiency of the ideal Carnot cycle for a given temperature difference.

For effective isothermal compression in a separate compressor, the compression polytropic should be as close as possible to the isotherm or in real conditions to a value of 1.1. Moreover, the entire compression process is preferably carried out

single-stage with minimal mechanical losses and high volumetric efficiency.

Currently, only screw compressors with oil or coolant injection meet these requirements.

Effective implementation of the cycle is possible with a degree of pressure increase in the process of isothermal compression from 18 and above.

In the proposed regenerative cycle, after isothermal air compression and separation, the fresh charge is heated with exhaust gases in a heat exchanger

(regenerator) increasing the temperature to 500-700 ° С. In order to avoid throttling at the inlet of the working fluid into the expansion cylinder and the late ignition of the fuel, the exhaust of the working fluid must not be fully exhausted, i.e., the exhaust valve must be closed before the piston arrives at TDC. A small amount of exhaust gas is compressed at the end of the exhaust stroke, while simultaneously producing an initial fuel injection.

Exhaust gases will presumably have a temperature of 600-800 ° C and an oxygen content of about 10%. With a compression ratio of 7, for example, the temperature of the exhaust gases in the dead space of the cylinder will increase to 1600-1700 ° C, and the pressure to 15-16 bar. Fuel injection is carried out with a certain lead angle by analogy with a diesel engine. The active phase of combustion will begin already before TDC as in a diesel engine, and the pressure will increase to the pressure level in the intake pipe (20-22 bar), and the temperature will reach the maximum set temperature of the working fluid. The compression ratio of the exhaust gases can also be increased to 10, then the temperature at the time the piston arrives at the TDC will already be close to the maximum set temperature of the working fluid, and the pressure value will be close to the pressure in the inlet pipe. In this case, the active phase of combustion should be initiated at the moment of opening of the intake valve.

At the moment the piston arrives at the TDC or with a certain advance angle, the inlet valve is opened and the working fluid is inlet. At the same time, fuel injection is continued to maintain a given temperature of the working fluid until the end of the intake process. Upon inlet according to the proposed method, a fresh charge evenly entering the cylinder will quickly heat up and take up an increasing volume

over-piston space without pressure drop and significant losses on

throttling.

Description of drawings

FIG. 1 General diagram of a device operating by the proposed method.

FIG. 2, 3, 4, 5 Schematic representation of engine operation during inlet, expansion, and exhaust. FIG. 6 PV diagram of the cycle according to the proposed method. Description of an embodiment of the invention

The proposed method can be implemented in a piston engine having special intake, exhaust and gas distribution systems, as well as equipped with a separate screw compressor (Fig. 1)

The device contains the following main elements: expansion machine (engine) 1, exhaust valve 2, intake valve 3, regenerator 4, separator 5, compressor 6, fan 7, compressor cooling radiator 8.

The screw compressor with oil or water injection is equipped with a cooling and separation system for the injected liquid. The regenerator is a heat exchanger, which can be supplemented by a pre-heating system and a system of neutralizing harmful substances. The expansion machine or the engine itself is a traditional piston design with a crank mechanism.

The inlet valve must be specially designed to prevent

spontaneous opening due to the pressure difference, as well as being as balanced as possible so that its opening does not require large energy costs. The intake valve actuator must be equipped with a mechanism for controlling the duration of the intake phase to control engine power.

The fuel system of the engine, in general, can be similar to diesel engines with direct injection, but with a special control algorithm.

The proposed cycle is push-pull and is implemented for one revolution of the crankshaft of the piston engine as follows.

When the engine piston approaches the BDC, the exhaust valve is opened and when the piston moves upward, the spent working fluid is discharged (FIG. 2). The working fluid is not fully discharged and the exhaust valve is closed 10-40 ° before the TDC and the spent working fluid is compressed, simultaneously by injecting fuel (Fig 3.) When the piston reaches TDC, the inlet valve is opened and a fresh charge is inlet (Fig. 4), that is, air pre-compressed in a separate screw compressor and heated by exhaust gases in the regenerator-heat exchanger.

The maximum duration of the inlet phase is determined by the specified parameters of the working fluid (temperature, pressure, mass) at the end of the inlet so that the amount of working fluid in the cylinder at the end of the inlet corresponds to the maximum compressor capacity. The duration of the inlet phase is changed simultaneously with a decrease in the amount of introduced fuel and compressor productivity with a decrease in load. With a proportional decrease in the intake phase, the amount of fuel introduced and the compressor capacity, a decrease in engine power will not lead to a decrease in the thermal efficiency of the cycle with a decrease in load. Consequently, the change in the effective efficiency of the entire system depending on the load will not be as significant as that of traditional diesel and gasoline engines. The performance of the compressor is controlled by one of the known methods used based on the readings of a pressure sensor.

At the end of the inlet process, close the inlet valve and carry out the expansion of the working fluid (Fig. 5)

According to preliminary theoretical calculations of the cycle according to the proposed method of operation, the thermal efficiency will be significantly higher than the thermal efficiency of the Sabate-Trinkler cycle and may exceed 80%.

The mode of the proposed engine is two-stroke, therefore, the same power requires a significantly smaller cylinder volume than for a four-stroke diesel engine. The mechanical efficiency of the proposed engine will be higher than the mechanical efficiency of the diesel engine.

Based on the foregoing, it can be assumed that the effective efficiency of the proposed engine can reach and even exceed 60%.

Claims

Claim

The method of operation of a two-stroke internal combustion engine with external compression in a separate compressor and heating the compressed working fluid in the regenerator with exhaust gas heat, characterized in that the compression is carried out in a screw compressor with the injection of a cooling agent into compressible air, and at the end of the exhaust cycle of the engine, the expansion valve is closed machines before the piston arrives at top dead center, compress a certain amount of exhaust gas, produce the initial fuel injection in the squeeze s exhaust gases continue fuel injection during the intake phase of the working body while maintaining a predetermined temperature, the engine power is controlled proportional to the decrease in the intake phase, fuel quantity injected and the compressor performance.