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Thermodynamic Analysis of LPG Expansion in Direct-Injection Spark-Ignition Engines: Isenthalpic vs Isentropic Modeling Fauzan Azima; Aditya Harjon Bahar; Taufiq Bin Nur
Sustainable in Energy Science and Technology Vol. 2 No. 1 (2026): Sustainable in Energy Science and Technology
Publisher : Politeknik Negeri Medan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.51510/siest.v1i2.3073

Abstract

Liquefied petroleum gas (LPG) fuel in modern direct-injection spark-ignition (DISI) engines must be modeled carefully to predict combustion behavior. In this work, we reformulate a student project into a research manuscript by comparing isenthalpic (Joule–Thomson) versus isentropic (ideal adiabatic) expansions of liquid LPG (propane surrogate) during injection. Using REFPROP thermophysical data and MATLAB simulations, we vary fuel rail pressures (45–100 bar) and fuel temperatures (30–85 °C) to determine critical flow properties at the injector throat (Mach 1 conditions). The choking point is identified by iterating pressure drop until the Mach number reaches unity in either a single-phase or two-phase region. We compute the resulting flashing ratio (liquid volume to vapor volume) for each model. Our results show that fuel temperature has a far greater effect on the speed-of-sound drop than rail pressure across all models, with higher temperatures yielding smaller acoustic drops. Nearly all cases produce flashing ratios Rp>1 (indicating significant vaporization), except under the second isenthalpic model where Rp falls below unity. Notably, the isentropic, first-isenthalpic, and isothermal models best reproduce a reference spray flash pattern, but their flashing ratios are very similar. Thus, we cannot definitively rank one model superior. Our analysis highlights that isentropic expansion yields a larger temperature drop than isenthalpic throttling, consistent with thermodynamic theory. The isentropic and first isenthalpic models predict almost identical choked-flow velocities and speed-of-sound behavior, whereas deviations appear only under the nonideal (second isenthalpic) cases. In summary, this modeling confirms that choosing a flash expansion assumption has only a subtle effect on predicted LPG fueling, provided the two leading models are considered.
Catalytic Pyrolysis of Plastic Waste for Gasoline Fuel: Reaction Mechanism Engine Integration Enzo Wiranta Battra Siahaan; Tulus Burhanuddin Sitorus; Himsar Ambarita; Taufiq Bin Nur; Ilmi Ilmi; Janter Pangaduan Simanjuntak
Automotive Experiences Vol. 8 No. 2 (2025)
Publisher : Universitas Muhammadiyah Magelang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31603/ae.13822

Abstract

The escalating accumulation of plastic waste demands not only scalable but integrative conversion solutions. Among thermochemical routes, catalytic pyrolysis has emerged as a promising pathway to produce gasoline-range hydrocarbons from plastic polymers compatible with spark-ignition engines. This review critically evaluates recent advancements in pyrolysis of key plastics polypropylene (PP), polyethylene (PE), polystyrene (PS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) with a focus on fuel yield, hydrocarbon distribution, and engine-level performance. Comparative analysis reveals PP as the most viable feedstock, achieving up to 85% liquid yield and producing oil with high Research Octane Numbers (RON 85”“95), outperforming PE and PS in combustion efficiency and emission compliance. However, persistent challenges such as fuel instability, catalyst deactivation, and elevated aromatic emissions particularly from PS complicate real-world deployment. The review further dissects the interplay between catalyst type, reactor design, and post-treatment, highlighting how these variables modulate product quality and engine operability. Notably, 10”“20% PP/PE-derived pyrolysis gasoline blends demonstrate near-parity with conventional gasoline in Brake Thermal Efficiency and regulated emissions, without requiring engine modifications. This work bridges molecular-level reaction chemistry with combustion diagnostics and policy-aligned emission metrics, offering a rare multiscale synthesis. By articulating process-emission-performance trade-offs, it provides a strategic reference for researchers and practitioners aiming to scale waste-to-fuel systems within circular economy frameworks.
Blade curvature as a key driver of conical-basin gravitational vortex turbine performance: experimental evidence Andianto Pintoro; Himsar Ambarita; Farel Hasiholan Napitupulu; Tulus Burhanuddin Sitorus; Taufiq Bin Nur; Ilmi Abdullah; Rimbawati Rimbawati
SINERGI Vol. 30 No. 3 (2026)
Publisher : Universitas Mercu Buana

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22441/sinergi.2026.3.001

Abstract

This study investigates the role of runner blade curvature in enhancing the performance of Gravitational Water Vortex Turbines (GWVTs) for low-head hydropower applications. Despite growing interest in GWVT technology, previous studies typically vary multiple geometric parameters simultaneously, leaving the isolated effect of blade curvature radius insufficiently understood. To address this research gap, an experimental investigation was conducted using a conical-basin GWVT with three runner configurations having identical blade inclination (66°) but different curvature radii (0.10 m, 0.20 m, and 0.30 m). Experiments were performed under controlled flow rates of 800, 1025, and 1300 LPM. Turbine torque, rotational speed, mechanical power, and efficiency were measured using a Prony brake dynamometer and magnetic tachometer. Each test condition was repeated three times, and the resulting data were analyzed using mean and standard deviation analysis to ensure measurement reliability and experimental consistency. The results show that increasing blade curvature significantly improves hydrodynamic interaction between the vortex flow and the runner. The runner with a curvature radius of 0.30 m achieved the best performance, producing a peak torque of 15.92 Nm, mechanical power of 109.95 W, and maximum efficiency of 66.43% at moderate flow conditions. The findings establish a direct curvature-performance relationship, demonstrating that larger curvature enhances tangential momentum transfer, prolongs blade-vortex interaction, and improves torque generation in low-head vortex systems. This study empirically confirms blade curvature as the key parameter governing hydrodynamic coupling and energy extraction in GWVT runners, while providing a practical design guideline to improve efficiency in low-head decentralized micro-hydropower systems.