WO1990015923A1

WO1990015923A1 - Carburettor system for a combustion engine

Info

Publication number: WO1990015923A1
Application number: PCT/NL1990/000084
Authority: WO
Inventors: Jacob Klimstra
Original assignee: N.V. Nederlandse Gasunie
Priority date: 1989-06-21
Filing date: 1990-06-18
Publication date: 1990-12-27
Also published as: NL8901564A; AU5848990A

Abstract

The invention relates to a combustion engine equipped with a system for supplying an air-fuel mixture to the cylinders of the engine, which system comprises an intake manifold, a mixer for mixing the fuel and air in the correct ratio, and lines connecting the mixer to the intake manifold, the mixer to the air intake system and the mixer to a fuel supply system. Both the line (5) connecting the air intake system to the mixer and the line (4) connecting the mixer to the intake manifold have a length at least five times the line diameter.

Description

CARBURETTOR SYSTEM FOR A COMBUSTION ENGINE

The invention relates to a combustion engine equipped with a system to supply an air-fuel mixture to the cylinders of the engine, which system comprises an intake manifold, a mixer for mixing the fuel and air in the correct ratio, and lines connecting the mixer to the intake manifold, the mixer to an air intake system, and the mixer to a fuel supply system. More specifically, the invention relates to a carburettor system for a gas engine.

In considering possibilities of obtaining cleaner exhauεtfumeε from vehicles, the operating principle of the engine plays a major role. The diesel engine utilizes fuel injection, air being drawn in via an inlet valve and then compressed. Compression causes the temperature of the air in the cylinder to rise to a high level so that the fuel subsequently injected combusts spontaneously. In order for the temperature to rise high enough, a high compression ratio is needed. The diesel engine has a high efficiency due in part to the high compression ratio. The output power of a diesel engine is controlled by the amount of fuel to be injected per stroke. Diesel fuel is characterized by the ease with which it combusts spontaneously. Ideally, a diesel engine would have only little adverse effect on the environment. This implies the absence of unwanted substances in the exhaust gas, little noise and no unsafe situations. In practice, the exhaust gas of a reciprocating engine may contain oxides of nitrogen (NO ), oxides of sulphur (SO ), carbon monoxide (CO), hydrocarbons and soot. In combustion processes, under the influence of high temperature, NO evolves from nitrogen and oxygen, the main components of air. NO and SO add to the formation of acid rain. Carbon monoxide, hydrocarbons and soot in the exhaust gasoriginate from incomplete combustion, that is to say, the fuel supplied to the engine does not combust completely with oxygen fromthe air. These substances are often toxic and give rise to the formation of smog and foul odour. Engine noise results from the rapid pressure changes in the engine cylinders. A diesel engine iε noisier than a petrol engine because of the higher pressure in the cylinders and the more rapid combustion. A disadvantage of liquid fuels is that they are heavier than air and, so, may cause soil pollution. Natural gas iε lighter than air and rises, so that soil pollution iε ruled out. For the same reason, the fire and explosion hazards of natural gas are much smaller.

Reducing the NO production of a diesel engine by reducing the cylinder temperature has adverεe effectε on the emission of CO and soot. This iε because, in a diesel engine, a high temperature iε needed for proper ignition and combustion. Improvements in the fuel injection and atomizing techniques may yield some improvement albeit only to a limited extent. For a petrol engine, the Otto engine, it holdε that with a good carburettor the fuel-air mixture can be perfectly homogeneous, contributing to optimum combustion.

Natural gaε exhibitε excellent properties for use as an engine fuel. However, research haε εhown that problems often arose in the preparation of the mixture in respect of inadequate homogeneity of the mixture and irreproducibility of the air-fuel ratio. As a result, the cylinders did not always receive the correct mixture. The purpose of the invention is to equip gaε engines with a system for the preparation of an air-fuel mixture that does not have the above-mentioned diεadvantageε and that enεures good homogeneity of the mixture as well aε good reproducibility of the air-fuel mixture for each cylinder of the engine.

In the invention this iε accompliεhed by uεing, in the supply syεtem for the air-fuel mixture to the engine cylinders referred to in the introduction, lines from the air intake system to the mixer and from the mixer to the intake manifold with a length at least five times the line diameter. In this manner, the fuel is distributed uniformly in the combustion air and a special path is obtained for good mixing of the fuel and the air so that each cylinder always receiveε the optimum air-fuel mixture throughout the load range of the engine. The line connecting the air intake system to the mixer and the line connecting the mixer to the intake manifold should preferably jointly form an S-shaped line. The mixer is preferably placed halfway down the S-shaped line. The mixer incorporates a throttle control valve and the air intake εyεtem incorporateε an air control valve; these two valves are mechanically linked. In order for the gaε to be brought to a higher temperature on leavingthe pressure reducing regulator, in which it cools down, it is brought in heat-exchanging contact with the ambient air through a coiled line. Consequently, on leaving the heat exchanger, the gas haε substantially the same temperature as the ambient air.

Further characteristics and advantageε will be clear from the following description with references to the attached drawings.

Fig. 1 shows a carburettor system which overcomes the mentioned disadvantageε of the gaε engine.

Part 1 is a schematic representation of an Otto engine with six cylinderε each of which iε connected to the intake manifold, which iε connected to the common supply line 2 for the fuel mixture. The supply line changes into an S-shaped line 3 esεentially conεiεting of a first line section 4 with a 180-degree bend and a connecting straight part, a line section 5 comprised of a 180-degree bend and two connecting straight parts and a line section 6. Line section 6 connects at one end to air filter 7 whilst between the other end of line section 6 and line section 5 air valve 8 iε inserted. Between line section 5 and line section 4 is a mixer in which the fuel iε mixed with air. To that end, a fuel supply line 10 with throttle 11 is provided. Furthermore, the customary pressure regulating valve 12 and main adjustment screw 13 are provided in the fuel supply line. The mixer may be of the variety commonly used on gas engines. The air valve and the throttle are mechanically linked εo that the correct air-fuel ratio is maintained under all operating conditions.

Line section 4 and line section 5 are at least five times aε long as their respective diameters. This ensures in line section 5 that the air flow going to the mixer is substantially free from disturbance by the air valve 8. The length of line section 4 ensureε that, at the tranεition from line section 4 to εupply line 2, an air-fuel mixture haε formed that iε εo homogeneous that each cylinder receives a mixture of the same composition and that there iε no difference between the mixtureε going to, notably, the No 1 and No. 6 cylinders.

In addition, when the power output of the engine iε increaεed by the operator, this geometry of the carburetion syεtemautomatically enεureε a richer mixture for a brief period. For, becauεe of the diεtance between the mixer and the air valve, opening of the throttle will have a leading effect on the attendant increaεed air supply, so that the engine will briefly receive a somewhat richer mixture and, as a result, will go into a higher regime more flexibly. Conversely, when the engine is shut down by closing the throttle, the air present in line εection 5 haε a purging effect in the engine, which, unlike current carburettor εystemε, has no polluting effect; this is becauεe in current carburettor systemε a mixture of fuel and air is used for this purpose. A carburetion system as deεcribed in relation to

Fig. 1 may be made suitable for natural gas, which iε usually delivered or available under high pressure (approx. 200 bar), by utilizing the set-up schematically represented by Fig. 2. 20 represents a number of gas tanks containing natural gas with a pressure depending on the degree of filling of the tank. Aε the gaε pressure is reduced to atmospheric, the gas cools down (0.5 K per bar presεure reduction), which may impair the performance of the curburettor system.

Each tank 20 may be connected to a line 21, which is in heat-exchanging contact with a line 22 through which the cooling water of the engine flows. In this way, the gaε is heated to some extent. After the pressure has been reduced, the gaε is brought into heat exchanging contact in a coiled line with a second coaxial line. Ambient air is used here as a heating medium εo that the gas, on leaving the heat exchanger 23, haε substantially the εame temperature aε the ambient air. Finally, the gaε flowε to the carburettor εyεtem after paεεing a εecond system of pressure regulators. Ambient air is supplied to heat exchanger 23 with the aid of a fan, which also supplies ambient air for cooling the engine casing.

Claims

C A M S

1. Combustion engine equipped with a system to supply an air-fuel mixture to the cylinders of the engine, which system comprises an intake manifold, a mixer for mixing the fuel and air in the correct ratio, and lines connecting the mixer to the intake manifold, the mixer to an air intake system and the mixer to a fuel supply system, characterized in that both the line (5) connecting the air intake system to the mixer and the line (4) connecting the mixer to the intake manifold have a length at least five time the line diameter.

2. Combustion engine in accordance with Claim 1, characterized in that natural gaε is used as fuel.

3. Combustion engine in accordance with either of Claims 1 and 2, characterized in that the line connecting the air intake εyεtem to the mixer and the line connecting the mixer to the intake manifold jointly form an S-εhaped line.

4. Combustion engine in accordance with either of Claimε 1 and 2 characterized in that the mixer is placed substantially halfway down the S-shaped line.

5. Combustion engine in accordance with any one of the Claims 1-4 with the mixer incorporating a throttle valve, characterized in that an air supply valve is incorporated in the air intake system, these valves being operated through mechanical linkage.

6. Combustion engine in accordance with any one of the Claimε 1-5 characterized in that, after preεεure regulation, the gaε iε brought into heat-exchanging contact with ambient air.