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Technical Paper

Piston and Guide-Pin Rattle Noise Mitigation in Electro-Mechanical Brake Caliper

2024-09-08
2024-01-3032
The hydraulic brake caliper utilizes pressurized brake fluid to actuate one or multiple pistons generating friction between the brake pads and disc. Calipers are classified into floating and fixed type caliper. Floating caliper slides inboard/outboard direction to apply and release pressure on the outer pad. This type of caliper has rubber or spring components to maintain specific clearance for sliding characteristics. Therefore, caliper rattle noise could occur due to wheel vibrations when the vehicle is driven on unpaved roads or rough surfaces. Rattle noise is particularly pronounced in front calipers positioned closer to the driver and its susceptibility tends to increase with the weight of the caliper. The Electro-Mechanical Brake (EMB) caliper has gained substantial attention in automotive industry for its advantages features including reduced brake drag, optimized vehicle layout and precise brake control.
Technical Paper

Glow-discharge Optical Emission Spectroscopy Study of Cr(III) Sealing in Anodized Aluminium-Silicon Alloys for Brake Component

2024-09-08
2024-01-3038
Calipers and pistons for high-end car braking systems are typically realized using anodized Aluminium-Silicon alloys. Indeed, Aluminium-Silicon alloys are light materials with optimal mechanical properties and, when anodized, excellent corrosion and wear resistances. To achieve these top-notch surface properties, the anodizing process is followed by a sealing post-treatment, which significantly improves the corrosion resistance and tunes the tribological properties (e.g., hardness and friction coefficient) of the anodized pieces. Sealing consists in the precipitation of insoluble hydroxides and functional compounds (e.g., corrosion inhibitors) inside the nano-pores of the anodic layer. Nevertheless, sealing might not penetrate through all the nano-porous structure of the anodic layer. Thus, in light of possible post-machining of sealed, anodized components, it appears fundamental to develop a tool to determine the depth penetration of sealing inside the anodic layer.
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

Numerical Study of Application of Gas Foil Bearings in High-Speed Drivelines

2024-06-12
2024-01-2941
The commitment to environmentally friendly transportation calls for efficient solutions with the evolution of automotive industry. Turbochargers are an important part of this development. The application of Gas or Air Foil Bearings (GFB) instead of traditional hydrodynamic bearings is recently very noticed, with which the fuel consumption, and emissions can be minimized as well as decreasing the maintenance costs and increasing the reliability. However, low viscosity of gas leads to lower dynamic stiffness and damping characteristics resulting in low load carrying capacity and instability at higher speeds. Gas bearings can be enhanced by adding a foil structure commonly known as gas foil bearings whose dynamic stiffness can be tailored by modifying the geometry and the material properties resulting in better stability and higher load carrying capacity.
Technical Paper

Guided Port Injection of Hydrogen as an Approach for Reducing Cylinder-to-Cylinder Deviations in Spark-Ignited H2 Engines – A Numerical Investigation

2024-06-12
2024-37-0008
The reduction of anthropogenic greenhouse gas emissions and ever stricter regulations on pollutant emissions in the transport sector require research and development of new, climate-friendly propulsion concepts. The use of renewable hydrogen as a fuel for internal combustion engines promises to provide a good solution especially for commercial vehicles. For optimum efficiency of the combustion process, hydrogen-specific engine components are required, which need to be tested on the test bench and analysed in simulation studies. This paper deals with the simulation-based investigation and optimisation of fuel injection in a 6-cylinder PFI commercial vehicle engine, which has been modified for hydrogen operation starting from a natural gas engine concept.
Technical Paper

Experimental Study of Lignin Fuels for CI Engines

2024-06-12
2024-37-0022
This study explores the feasibility of using a sustainable lignin-based fuel, consisting of 44 % lignin, 50 % ethanol, and 6 % water, in conventional compression ignition (CI) marine engines. Through experimental evaluations on a modified small-bore CI engine, we identified the primary challenges associated with lignin-based fuel, including engine startup and shutdown issues due to solvent evaporation and lignin solidification inside the fuel system, and deposit formation on cylinder walls leading to piston ring seizure. To address these issues, we developed a fuel switching system transitioning from lignin-based fuel to cleaning fuel with 85 vol% of acetone, 10 vol% of water and 5 vol% of ignition improving additive, effectively preventing system clogs.
Technical Paper

Influences of High-Pressure Pump and Injector Nozzle Geometry on Hydraulics Characteristics of a Mechanical Diesel Direct-Injection System

2024-06-04
2024-01-5061
The geometry of high-pressure pump and injector nozzles crucially influences hydraulic behaviors (e.g., the start of injection, the pressure profiles developed in the high-pressure line, needle lift, and injection rates) in diesel engines. These factors, in turn, significantly impact fuel atomization, fuel–air mixing, combustion quality, and the formation of emissions. The main geometry parameters such as plunger diameter and the number and diameter of nozzles lead to the system complexity, requiring careful analysis, design, and calibration. In this study, a high-speed shadowgraph system and a high-resolution pressure recording system were developed to capture the start of injection, spray structure, and pressure profiles in the high-pressure line. Additionally, a model was developed using GT-Fuel package built within the GT-Suite of simulation tools to explore different plunger diameters and numbers and diameters of injector nozzles.
Journal Article

Auto-Ignited Combustion Control in an Engine Equipped with Multiple Boosting Devices

2024-06-03
Abstract The combustion timing of auto-ignited combustion is determined by composition, temperature, and pressure of cylinder charge. Thus, for a successful auto-ignition, those key variables must be controlled within tight target ranges, which is challenging due to (i) nature of coupling between those variables, and (ii) complexity of managing multiple actuators in the engine. In this article, a control strategy that manages multiple actuators of a boosted homogeneous charge compression ignition (HCCI) engine is developed to maintain robust auto-ignited combustion. The HCCI engine being considered is equipped with multiple boosting devices including a supercharger and a turbocharger in addition to conventional actuators and sensors. Since each boosting device has its own pros and cons, harmonizing those boosting devices is crucial for successful transient operation.
Journal Article

Effect of Ethanol and Iso-Octane Blends on Isolated Low-Temperature Heat Release in a Spark Ignition Engine

2024-05-17
Abstract Low-temperature heat release (LTHR) is of interest for its potential to help control autoignition in advanced compression ignition (ACI) engines and mitigate knock in spark ignition (SI) engines. Previous studies have identified and investigated LTHR in both ACI and SI engines before the main high-temperature heat release (HTHR) event and, more recently, LTHR in isolation has been demonstrated in SI engines by appropriately curating the in-cylinder thermal state during compression and disabling the spark discharge. Ethanol is an increasingly common component of market fuel blends, owing to its renewable sources. In this work, the effect of adding ethanol to iso-octane (2,2,4-trimethylpentane) blends on their LTHR behavior is demonstrated. Tests were run on a motored single-cylinder engine elevated inlet air temperatures and pressures were adjusted to realize LTHR from blends of iso-octane and ethanol without entering the HTHR regime.
Technical Paper

Centrifugal Compressor Map Prediction Based on Geometrical Parameters with Invariant Coefficients

2024-04-24
2024-01-5056
In the present work, a new methodology for predicting the performance of centrifugal compressors is developed. The proposed method differs from existing methods found in literature by gathering principal losses in three parameters: two constants and one variable, which is a function of the compressor wheel geometrical characteristics. As those parameters are constants for a given centrifugal compressor, there is no need for additional corrective parameters in order to obtain coherent results. Indeed, the proposed methodology does not depend on the choice of the slip factor correlation for the prediction of the correct pressure ratio. However, the choice of slip factor influences the efficiency computation. The prediction of the compressor maps for two full stage centrifugal compressors is presented and they show good agreement while compared with manufacturer’s data obtained from gas stand measurements.
Journal Article

TOC

2024-04-15
Abstract TOC
Technical Paper

Improving the Performance of Diesel Engines by Bore Profile Control under Operating Conditions

2024-04-09
2024-01-2832
The cylinder bore in an engine block is deformed under the assembling stress of the cylinder head and thermal stress. This distortion exacerbates the piston skirt friction and piston slap. Through a numerical and experimental study, this article analyzes the effect of an optimized bore profile on the engine performance. The piston skirt friction was estimated in a three-dimensional elastohydrodynamic (EHD) friction analysis. An ideal cylindrical bore under the rated load condition was assumed as the optimal bore profile that minimized the piston skirt friction without compromising the piston slap. The simulation study revealed that secondary motion of the piston immediately after firing the top dead center can be mitigated by narrowing the piston–bore clearance at the upper position of the cylinder.
Technical Paper

Study on the Optimization of Sealing Environment of Cylinder Head Gasket

2024-04-09
2024-01-2833
Typically, modern automotive engine designs include separate cylinder heads and cylinder blocks and utilize a multilayer steel head gasket (MLS) to seal the resulting joint. Cylinder head bolts are used to hold the joint together and the non-linear properties of head gasket provide capability to seal the movement within the joint, which is essential for engine durability and performance. The current design of cylinder head gasket mainly evaluates the sealing performance in hot and cold state through finite element analysis. The sealing performance of cylinder head gasket is mainly determined by sealing pressure, fatigue and lateral movement in the joint, which have been widely studied [1]. However, no one has been involved in the study of factors affecting sealing pressure and lateral movement in the joint.
Technical Paper

Experimental Investigation of Internal and External EGR Effects on a CNG-OME Dual-Fuel Engine

2024-04-09
2024-01-2361
Dual-fuel engines powered by renewable fuels provide a potential solution for reducing the carbon footprint and emissions of transportation, contributing to the goal of achieving sustainable mobility. The investigation presented in the following uses a dual-fuel engine concept running on biogas (referred to as CNG in this paper) and the e-fuel polyoxymethylene dimethyl ether (OME). The current study focuses on the effects of exhaust gas rebreathing and external exhaust gas recirculation (EGR) on emissions and brake thermal efficiency (BTE). A four-cylinder heavy-duty engine converted to dual-fuel operation was used to conduct the engine tests at a load point of 1600 min-1 and 9.8 bar brake mean effective pressure (BMEP). The respective shares of high reactivity fuel (HRF, here: OME) and low reactivity fuel (LRF, here: CNG) were varied, as were the external and internal EGR rates and their combinations.
Technical Paper

Experimental Study on Engine Performance Fueled with Ammonia-Hydrogen Blend Ignited by Diesel Pilot

2024-04-09
2024-01-2365
The global energy crisis and drastic climate change are continuously promoting the implementation of sustainable energy sources. To meet the emission standards and carbon-neutrality targets in vehicle industry, ammonia is considered to be one of the promising carbon-neutral fuels. However, running the engines on high amounts of ammonia may lead to significantly high ammonia slip. This originates huge safety concerns. Therefore, hydrogen is added in certain ratio with ammonia to promote combustion and reduce ammonia slip. Furthermore, adding diesel as a pilot fuel further facilitates the combustion reactions. This experimental study investigated the effect of different ammonia-hydrogen blend ratios on in-cylinder pressure, heat release rate, cumulative heat release, indicated mean effective pressure (IMEP), indicated thermal efficiency (ITE), CA5 and CA50. This effect of blend ratios was tested for varied diesel pilot amounts and timings.
Technical Paper

Elucidation of Deteriorating Oil Consumption Mechanism Due to Piston Top Ring Groove Wear

2024-04-09
2024-01-2269
The piston and piston ring are used in a severe contact environment in engine durability tests, which causes severe wear to the piston ring groove, leading to significant development costs for countermeasures. Conventionally, in order to ensure functional feasibility through wear on the piston top ring groove (hereinafter “ring groove”), only functional evaluations through actual engine durability testing were performed, and there was an issue in determining the limit value for the actual amount of wear itself. Because of this, the mechanism that may cause wear on the ring groove was clarified through past research, but this resulted in judgment criteria with some leeway from the perspective of functional assurance. To establish judgment criteria, it was necessary to understand both functional effect from ring groove wear and the mechanism behind it.
Technical Paper

Validation of a Two-Parameter Controlled Novel Tribometer for Analysing Durability of Piston Ring-Engine Cylinder Tribo-Pair

2024-04-09
2024-01-2067
The wear of the piston ring-cylinder liner system in gasoline engines is inevitable and significantly impacts fuel economy. Utilizing a custom-built linear reciprocating tribometer, this study assesses the wear resistance of newly developed engine cylinder coatings. The custom device offers a cost-effective means for tribological evaluation, optimizing coating process parameters with precise control over critical operational factors such as normal load and sliding frequency. Unlike conventional commercial tribometers, it ensures a more accurate simulation of the engine cylinder system. However, existing research lacks a comprehensive comparative analysis and procedure to establish precision limits for such modified devices. This study evaluates the custom tribometer's repeatability compared to a commercial wear-testing instrument, confirming its potential as a valuable tool for advanced wear testing on engine cylinder samples.
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