# US 4,399,786 A · Method for pilot injection of fuel in diesel engines

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- Number: US 4,399,786 A
- Document ID: US4399786A
- Status: Granted
- Kind: A
- Application number: 06/181,241
- Filed: 1980-08-25
- Granted: 1983-08-23
- Earliest claimed: 1977-11-23
- Assignees: AB Volvo
- Inventors: Heinz E. A. Holmer
- Web page: https://patentgrep.com/patent/US4399786A

## CPC

- F02M 59/08: characterised by two or more pumping elements with conjoint outlet {or several pumping elements feeding one engine cylinder (feeding common rails F02M63/0225)}
- F02B 3/06: with compression ignition (compression ignition engines using air or gas for blowing fuel into compressed air in cylinder F02B13/02)
- F02B 23/0663: {having multiple injectors per combustion chamber}
- F02B 23/0696: {W-piston bowl, i.e. the combustion space having a central projection pointing towards the cylinder head and the surrounding wall being inclined towards the cylinder wall}
- F02M 63/00: Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; {Combination of fuel pump with other devices, e.g. lubricating oil pump}
- F02B 23/0624: {Swirl flow}
- F02B 23/0666: {having a single fuel spray jet per injector nozzle}
- F02B 23/0669: {having multiple fuel spray jets per injector nozzle}
- F02B 2275/14: Direct injection into combustion chamber
- Y02T 10/12: Improving ICE efficiencies
- F02M: SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02B: INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL (gas-turbine plants F02C; hot-gas or combustion-product positive-displacement engine plants F02G)
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A method for the pilot injection of fuel in a direct injection diesel engine with a depression in the tops of the pistons. The pilot fuel, of relatively high cetane number, e.g. diesel fuel, is sprayed prior to the main spray, obliquely from the side into the piston depression in a direction counter to the rotation of the intake air. Thereafter, during the same combustion cycle, the main spray, of lower cetane number, e.g. methanol, is sprayed in a zone around the center axis of the piston depression. A substantial reduction in pollutants is achieved.

## Claims

### Claim 1

In a fuel injection method for direct injection diesel engines with a depression in the tops of the pistons, in which a first injection pump with a regulator and accompanying first injector for each cylinder sprays fuel with a relatively low cetane number in a main spray in a zone around the center axis of the respective piston depression; the improvement comprising injecting a pilot spray of a fuel with a relatively high cetane number from a second injection pump (6) with a regulator and accompanying second injectors (8) for each cylinder, from the side into the respective piston depression in a direction (B) toward a central zone in the piston depression in which the intake air rotates, operating both of said injection pumps during a combustion cycle, and injecting said pilot spray before said main spray so that the compression combustion of the fuel from the second injection pump (6) can initiate the combustion of the fuel from the first pump (1).

### Claim 2 (depends on 1)

Injection method according to claim 1, in which each respective first injector (4) is disposed to inject the fuel with a large uniform distribution around the center axis (Z) of the piston depression, while each respective second injection (8) is disposed to inject the fuel with a small distribution obliquely from the side into the piston depression (A).

### Claim 3 (depends on 1)

Injection method according to claim 1, in which the first injectors (4) have multi-hole nozzles, while the second injectors (8) have single-hole nozzles.

### Claim 4 (depends on 1)

Injection method according to claim 1, in which each respective second injector (8) is disposed to inject the fuel from a location on or in the vicinity of the periphery of the piston depression (A) and with an injection path (B), which forms an angle (.alpha.) of between 10.degree. and 20.degree. with a cross-sectional plane through the cylinder and whose projection onto said plane is tangent to a circle concentric to the periphery of the piston depression, the radius (r) of said circle being between 0.35 and 0.45 times the radius (R) of the piston depression.

### Claim 5 (depends on 4)

Injection method according to claim 4, in which said angle (.alpha.) is about 15.degree..

### Claim 6 (depends on 4)

Injection method according to claim 4, in which said radius (r) is about 0.40 times the radius (R) of the piston depression.

### Claim 7 (depends on 1)

Injection method according to claim 1, in which the second injection pump (6) is set to essentially only inject the required amount of fuel for starting, warming up and idling, the first injection pump (1) being inactive when the engine is idling.

### Claim 8 (depends on 1)

Injection method according to claim 1, in which the first injection pump (1) is set to inject fuel at about 10 degrees of rotation of the crankshaft after the second injection pump (6).

### Claim 9 (depends on 1)

Injection method according to claim 1, in which said fuel of relatively low cetane number is an alcohol.

### Claim 10 (depends on 9)

Injection method according to claim 9, in which said alcohol is methanol.

### Claim 11 (depends on 1)

Injection method according to claim 1, in which the pilot spray is injected obliquely from the side into the respective piston depression in a direction (B) which is counter to the rotation of the intake air.