Dual multi-fuel combustion system with glycerin-based main energy supply, pilot ignition, air-assisted injection and integrated exhaust aftertreatment

Abstract

Compression-ignited dual-fuel combustion engine for road vehicles, comprising (a) a pilot fuel system with common-rail injection, (b) a glycerin fuel system with a heated tank, heated lines, filter / water separator and at least one air-assist inductor having a coaxial supply of glycerin and auxiliary air from an auxiliary air supply, (c) a control unit configured for coordinated control of the pilot fuel system and the glycerin fuel system depending on sensor data including at least one lambda sensor and an exhaust gas temperature sensor, and (d) an exhaust gas-located oxidation catalyst, wherein the engine is designed for lean operation with an air-fuel ratio > 1 and is configured such that at least 85% of the supplied fuel energy can be provided by glycerin.

Description

2. Technical field The invention relates to the field of road vehicle propulsion systems (passenger cars / commercial vehicles) and in particular compression-ignition combustion engines that predominantly use glycerin as a liquid, biogenic energy carrier. 3. State of the art (briefly) Diesel engines offer high efficiency but require fossil fuels. Biogenic alternatives (biodiesel / ethanol) are available, but glycerin is produced in large quantities as a byproduct of biodiesel production. It is viscous, poorly atomizable, and difficult to ignite; incomplete oxidation can lead to the formation of aldehydes. Current systems do not adequately address this combination (pilot ignition + heated, air-assisted glycerin injection + DOC protection) in a production-ready engine. 4. Object of the invention Provision of a near-series engine system that uses glycerin safely, efficiently and with low emissions as the main fuel, without losing the operational robustness of a diesel engine. 5. Solution to the problem (core of the invention) The task is solved by a compression-ignition dual-fuel engine that combines a pilot fuel path (e.g., diesel HVO) with common-rail injection, a glycerin fuel path with heated lines, temperature and hazard control, an air separator filter, and air intake injectors, a control unit (ECU) for coordinated control of pilot and glycerin injectors (including sensors for lambda and exhaust gas temperatures), and a near-exhaust gas oxidation catalyst stage (DOC) in such a way that > ​​85% of the fuel energy can be derived from glycerin, at lean operation (λ / > 1) and controlled aldehyde conversion in the DOC. 6. Detailed description of at least one preferred embodiment 6.1 Engine Basics • Multi-cylinder, turbocharged compression ignition engine (e.g. R4, compression ratio 15-18:1), standard charge air routing. 6.2 Pitot fuel system • Standard common rail with injectors; low energy content (typically 5-15%). • Fuel: Diesel or HVO (Hydrotreated Vegetable Oil). 6.3 Glycerin fuel system • Tank with jacket heating, level and temperature sensors. • Two-stage filtration (coarse / fine) and water separator (glycerin is hygroscopic). • Heated lines and inline heater (controlled) to bring the viscosity into an injection window (e.g., 60–120 °C medium temperature). • Air-assist injectors (coaxial: central nozzle for glycerin, concentric air channel, auxiliary air pressure e.g., 0.5–2 bar) for a droplet spectrum. • Alternative design: Two-stage metering (intake manifold port nozzle + small direct nozzle into the combustion chamber). 6.4 Sensors & Control • ECU with core fields for: glycerin mass flow, auxiliary air pressure, line / nozzle temperature, pilot energy share, desired air-fuel ratio. • Sensors: lambda sensor, exhaust gas temperature sensors before / after DOC, pressure / temperature sensors in the fuel path; optional ion / cylinder pressure sensors. • Thermal management maintains a minimum temperature at the DOC (e.g., > 250 °C) for aldehyde conversion (including acrolein). 6.5 Aftertreatment of aspirated gases • Oxidation catalyst (DOC) positioned close to the exhaust gas (close-coupled). • Optional DPF (diesel particulate filter) as a safety net; particulate formation is low during lean operation. • Optional SCR depending on NOx target. 6.6 Safety and fault modes • Over-temperature, pressure, and leakage monitoring in the glycerol path; safety-safe operation on pilot-only systems. • Anti-coking strategies (flushing cycles, defined shading sequences). • Diagnostic logic for DOC efficiency (CO / HC slip). 6.7 Advantage of the design • Near-series integration on diesel platform. • High glycerin content with stable ignition and emission-safe oxidation. • Robust operation (cold start and emergency operation via pilot path). 7. Examples of implementation (parametric notes) • Glycerin temperature range: 60-120 °C (adjustable), depending on viscosity specification. • Auxiliary air pressure: 0.5-2 bar relative. • Lambda target: 1.1-1.5 (lean). • DOC operating range: 250 °C intake (map-controlled). • Pilot energy share: averaged over driving cycles < 10%. 8. Industrial Applicability Applicable in vehicles (cars / LCVs / HCVs), mobile work machines, and as a stationary range extender.

Claims

Compression-ignited dual-fuel combustion engine for road vehicles, comprising (a) a pilot fuel system with common-rail injection, (b) a glycerin fuel system with a heated tank, heated lines, filter / water separator and at least one air-assist inductor having a coaxial supply of glycerin and auxiliary air from an auxiliary air supply, (c) a control unit configured for coordinated control of the pilot fuel system and the glycerin fuel system depending on sensor data including at least one lambda sensor and an exhaust gas temperature sensor, and (d) an exhaust gas-located oxidation catalyst, wherein the engine is designed for lean operation with an air-fuel ratio > 1 and is configured such that at least 85% of the supplied fuel energy can be provided by glycerin. Motor according to claim 1, wherein the air-assist injector is designed as a coaxial nozzle with a central glycerin outlet opening and a concentric auxiliary air channel. Motor according to claim 1 or 2, wherein the glycerin medium temperature is maintained in a controllable range of 60 °C to 120 °C by means of an inline heater, wherein the control unit infers the viscosity from the temperature and adjusts the injection parameters. Motor according to one of the preceding claims, wherein the auxiliary air supply provides a regulated relative pressure between 0.5 bar and 2 bar. Motor according to one of the preceding claims, with a two-stage glycerin metering system, consisting of a port injection nozzle and a small-dimensioned direct nozzle into the combustion chamber. Engine according to one of the preceding claims, wherein the oxidation catalyst is positioned close to the exhaust gas ("close-coupled") such that its inlet temperature can be maintained at 250 °C. Engine according to one of the preceding claims, with DPF as an optional particulate filter stage. Engine according to one of the preceding claims, wherein the pilot fuel system is suitable for HVO as pilot fuel. Motor according to one of the preceding claims, with water separator ( ) in the glycerol path for reducing the water content of the hygroscopic glycerol. Motor according to one of the preceding claims, wherein the control unit is configured to perform a fail-safe switch to pure pilot operation as soon as sensor data exceed limit values ​​(leakage, overtemperature, DOC inefficiency). Glycerin injection system for retrofitting a compression-ignition engine, comprising the features of the glycerin fuel system according to claim 1 and the control unit for integration with an existing pilot fuel system. Vehicle comprising an engine according to one of claims 1 to 10. Instructions for submission •

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