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Technical Paper

A computational study of hydrogen direct injection using a pre-chamber in an opposed-piston engine

2024-07-02
2024-01-3010
Opposed-piston two-stroke engines offer numerous advantages over conventional four-stroke engines, both in terms of fundamental principles and technical aspects. The reduced heat losses and large volume-to-surface area ratio inherently result in a high thermodynamic efficiency. Additionally, the mechanical design is simpler and requires fewer components compared to conventional four-stroke engines. When combining this engine concept with alternative fuels such as hydrogen and pre-chamber technology, a potential route for carbon-neutral powertrains is observed. To ensure safe engine operation using hydrogen as fuel, it is crucial to consider strict safety measures to prevent issues such as knock, pre-ignition, and backfiring. One potential solution to these challenges is the use of direct injection, which has the potential to improve engine efficiency and expand the range of load operation.
Technical Paper

Measurements in the Recirculation Path of a Fuel Cell System

2024-07-02
2024-01-3009
When using "green" hydrogen, fuel cell technology plays a key role in emission-free mobility. A powertrain based on fuel cells (FC) shows its advantages over battery-electric powertrains when the requirement profile primarily demands high performance over a longer period of time, high flexible availability and short refueling times. In addition, FC achieves higher effi-ciencies than the combustion of hydrogen in a gas engine, meaning that the chemical energy is used more efficiently than with established combustion engines. When using FC technology, numerous companies in Baden-Württemberg can contribute their specific expertise from the traditional automotive construction and supplier business. This includes auxiliary units in the air (cathode) and hydrogen (anode) path, such as the air compressor, the H2 recycling pump, humidifier, cooling system, power electronics, valve and pressure tank technology as well as components of the fuel cell stack itself.
Technical Paper

Numerical Investigation of Injection and Mixture Formation in Hydrogen Combustion Engines by Means of Different 3D-CFD Simulation Approaches

2024-07-02
2024-01-3007
For the purpose of achieving carbon-neutrality in the mobility sector by 2050, hydrogen can play a crucial role as an alternative energy carrier, not only for direct usage in fuel cell-powered vehicles, but also for fueling internal combustion engines. This paper focuses on the numerical investigation of high-pressure hydrogen injection and the mixture formation inside a high-tumble engine with a conventional liquid fuel injector for passenger cars. Since the traditional 3D-CFD approach of simulating the inner flow of an injector requires a very high spatial and temporal resolution, the enormous computational effort, especially for full engine simulations, is a big challenge for an effective virtual development of modern engines. An alternative and more pragmatic lagrangian 3D-CFD approach offers opportunities for a significant reduction in computational effort without sacrificing reliability.
Technical Paper

Supercharger Boosting on H2 ICE for Heavy Duty applications

2024-07-02
2024-01-3006
Commercial vehicle powertrain is called to respect a challenging roadmap for CO2 emissions reduction, quite complex to achieve just improving technologies currently on the market. In this perspective alternative solutions are gaining interest, and the use of green H2 as fuel for ICE is considered a high potential solution with fast and easy adoption. NOx emission is still a problem for H2 ICE and can be managed operating the engine with lean air fuel ratio all over the engine map. This combustion strategy will challenge the boosting system as lean H2 combustion will require quite higher air flow compared to diesel for the same power density in steady state. Similar problem will show up in transient response particularly when acceleration starts from low load and the exhaust gases enthalpy is very poor and insufficient to spin the turbine. The analysis presented in this paper will show and quantify the positive impact that a supercharger has on both the above mentions problems.
Technical Paper

The 3D-CFD Contribution to H2 Engine Development for CV and Off-Road Application

2024-07-02
2024-01-3017
The hydrogen engine is one of the promising technologies that enables carbon-neutral mobility, especially in heavy-duty on- or off-road applications. In this paper, a methodological procedure for the design of the combustion system of a hydrogen-fueled, direct injection spark ignited commercial vehicle engine is described. In a preliminary step, the ability of the commercial 3D computational fluid dynamics (CFD) code AVL FIRE classic to reproduce the characteristics of the gas jet, introduced into a quiescent environment by a dedicated H2 injector, is established. This is based on two parts: Temporal and numerical discretization sensitivity analyses ensure that the spatial and temporal resolution of the simulations is adequate, and comparisons to a comprehensive set of experiments demonstrate the accuracy of the simulations. The measurements used for this purpose rely on the well-known schlieren technique and use helium as a safe substitute for H2.
Technical Paper

Simulation of Hydrogen Combustion in Spark Ignition Engines Using a Modified Wiebe Model

2024-07-02
2024-01-3016
Due to its physical and chemical properties, hydrogen is an attractive fuel for internal combustion engines, providing grounds for studies on hydrogen engines. It is common practice to use a mathematical model for basic engine design and an essential part of this is the simulation of the combustion cycle, which is the subject of the work presented here. One of the most widely used models for describing combustion in gasoline and diesel engines is the Wiebe model. However, for cases of hydrogen combustion in DI engines, which are characterized by mixture stratification and in some cases significant incomplete combustion, practically no data can be found in the literature on the application of the Wiebe model. Based on Wiebe's formulas, a mathematical model of hydrogen combustion has been developed. The model allows making computations for both DI and PFI hydrogen engines. The parameters of the Wiebe model were assessed for three different engines in a total of 26 operating modes.
Technical Paper

Numerical Investigation of the Effect of Piston Geometry on the Performance of a Ducted Fuel Injection Engine

2024-07-02
2024-01-3024
Ducted Fuel Injection (DFI) engines have emerged as a promising technology in the pursuit of a clean and efficient combustion process. This article aims at elucidating the effect of piston geometry on the engine performance and emissions of a metal DFI engine. Three different types of pistons were investigated and the main piston design features including the piston bowl diameter, piston bowl slope angle, duct angle and the injection nozzle position were examined. To achieve the target, computational fluid dynamics (CFD) simulations were conducted coupled to a reduced chemical kinetics mechanism. Extensive validations were performed against the measured data from a conventional diesel engine. To calibrate the soot model, genetic algorithm and machine learning methods were utilized. The simulation results highlight the pivotal role played by piston bowl diameter and fuel injection angle in controlling soot emissions of a DFI engine.
Technical Paper

Miller Cycle and Internal EGR in Diesel Engines Using Alternative Fuels

2024-07-02
2024-01-3020
The Single Cylinder Research Engine (SCRE) at the Institute of Internal Combustion Engines and Powertrain Systems is equipped with a variable valve train that allows to switch between regular intake valve lift and early intake valve closing (Miller). On the exhaust side, a secondary valve lift on each valve is possible with adjustable back pressure and thus the possibility of realising internal EGR. In combination with alternative fuels, even if they are Drop-In capable as HVO, properties differ and can influence the emission and efficiency behaviour. The investigations of this paper are focusing on regenerative Drop-In fuel (HVO), fossil fuel (B7), and an oxygenate (OME), that needs adaptions at the engine control unit, but offers further emission potential. By commissioning a 2-stage boost system, it is possible to fully equalize the air mass in Miller mode compared to the normal valve lift.
Technical Paper

Turbocharging system selection for a hydrogen-fuelled spark-ignition internal combustion engine for heavy-duty applications

2024-07-02
2024-01-3019
Nowadays, green hydrogen can play a crucial role in a successful clean energy transition, thus reaching net zero emissions in the transport sector. Moreover, hydrogen exploitation in internal combustion engines is favoured by its suitable combustion properties and quasi-zero harmful emissions. High flame speeds enable a lean combustion approach, which provides high efficiency and reduces NOx emissions. However, high air flow rates are required to achieve the load levels typical of heavy-duty applications. In this framework, the present study aims to investigate the required boosting system of a 6-cylinder, 13-liter heavy-duty spark ignition engine through 1D numerical simulation. A comparison among various architectures of the turbocharging system and the size of each component is presented, thus highlighting limitations and potentialities of each architecture and providing important insights for the selection of the best turbocharging system.
Technical Paper

Experimental and Numerical Investigations of a Dual-Fuel Hydrogen–Kerosene Engine for Sustainable General Aviation

2024-06-17
2024-01-6001
Reducing CO2 emissions is an increasingly important issue. In aviation, approaches such as e-propulsion only represent a solution for special applications due to the low energy density of batteries. Because of the low-cost and robust design of combustion engines, this concept is still the most suitable for general aviation. For defossilization, besides e-fuels and bio-fuels, which represent the so-called sustainable aviation fuels (SAF), hydrogen can serve as a promising energy carrier for CO2 reduction. For this purpose, the combustion process of a dual-fuel hydrogen–kerosene (Jet A-1) engine was developed and investigated for use in small aircrafts. This study explores the influence of hydrogen addition on combustion parameters, emissions, and efficiency.
Journal Article

Engine Behavior Analysis on a Conventional Diesel Engine Powered with Blends of Lemon Grass Oil Biodiesel–Diesel Blends

2024-06-14
Abstract Fossil fuel usage causes environmental pollution, and fuel depletion, further affecting a country’s economy. Biofuels and diesel-blended fuels are practical alternatives to sustain fossil fuels. This experimental study analyses lemongrass oil’s performance, emissions, and combustion characteristics after blending with diesel. Lemongrass oil is mixed with diesel at 10 (B10), 15 (B15), and 25% (B25) and evaluated using a 5.20 kW direct injection diesel engine. B10 brake thermal efficiency is 36.47%, which is higher than other blends. The B10 displays an 8.73% decrease in brake-specific fuel consumption compared to diesel. An increase in exhaust gas temperature for B10 than diesel is 4.5%. It indicates that higher lemongrass oil blends decrease exhaust gas temperature. The decrease in average carbon monoxide emissions in B10 to diesel is 22.19%. The decrease in hydrocarbon emissions for B10 to diesel is 7.14%.
Technical Paper

Transmission of Sound under the Influence of Various Environmental Conditions on Short Distances

2024-06-12
2024-01-2933
Electric vehicles, being inherently quiet without the typical combustion noises, pose a potential safety concern, especially at low speeds. Consequently, an Acoustic Vehicle Alerting System (AVAS) is mandatory in many countries worldwide to warn pedestrians of approaching electric vehicles. The development of AVAS sounds involves conducting measurements on an outside noise test track to verify compliance with regulations. Various environmental parameters on the test track can influence the transmission of sound from the car’s AVAS speaker to the measurement microphones. This research delves into understanding the relationship between the transmission of sound over short distances and environmental parameters. Over a one-year period, 122 measurements were conducted using a specially designed dolly setup. The frequency response function, which characterises the sound transmission, was calculated to determine the dependencies and correlations with environmental parameters.
Technical Paper

Artificial Neural Network for Airborne Noise Prediction of a Diesel Engine

2024-06-12
2024-01-2929
Throughout its history, the engine acoustic character has been emblematic of the product essence, owing to its robust correlation of factors like in-cylinder pressure gradients, components design, and perceived quality. Best practice for engine acoustic characterization requires the employment of a hemi-anechoic chamber, a significant number of sensors and special acoustic insulation for engine ancillaries and transmission. This process is highly demanding in terms of cost and time due to multiple engine working points to be tested and consequent data post-processing. Given the apparent underutilization of Neural Networks (NN) predictive capabilities in this research area, the following paper introduces a tool capable of estimation of engine acoustic performance by processing system inputs (e.g., Injected Fuel, Rail Pressure). This is achieved through the application of a Multi-Layer Perceptron (MLP), which operates as a feedforward network functioning at stationary points.
Technical Paper

Advanced H2 ICE Development Aiming for Full Compatibility with Classical Engines While Ensuring Zero-Impact Tailpipe Emissions

2024-06-12
2024-37-0006
Current GHG emissions are rebounding from an intermediate decline during the economic downturn caused by the Covid-19 pandemic. To get back on track to support the realization of the formulated goals of the Paris Agreement, scientific communities suggest that worldwide GHG emissions should be roughly halved by 2030 on a trajectory to reach net zero by around mid-century. Carbon neutrality imposes substantial changes in our energy mix. Hydrogen (H2) is considered to play a key role as a carbon-free and versatile energy carrier for all kinds of applications and use cases. Considering the high technological maturity of internal combustion engines (ICEs), the interest in ICEs powered by hydrogen as a CO2-free solution is rising worldwide. The content of this publication displays the necessary engineering steps to successfully convert a diesel-based engine to H2 DI operation.
Technical Paper

Influence of Intake Charge Temperature and EGR Rate on the Combustion and Emission Characteristics of Ammonia/Diesel Dual-Fuel Engine

2024-06-12
2024-37-0025
Ammonia has emerged as a promising carbon-free alternative fuel for internal combustion engines (ICE), particularly in large-bore engine applications. However, integrating ammonia into conventional engines presents challenges, prompting the exploration of innovative combustion strategies like dual-fuel combustion. Nitrous oxide (N2O) emissions have emerged as a significant obstacle to the widespread adoption of ammonia in ICE. Various studies suggest that combining exhaust gas recirculation (EGR) with adjustments in inlet temperature and diesel injection timing can effectively mitigate nitrogen oxides (NOx) emissions across diverse operating conditions in dual-fuel diesel engines.
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