Advanced Propulsion Systems Research Articles

Model predictive control for hydrogen fuel cell–driven multi-level permanent magnet synchronous motor drive

ABSTRACT This paper proposes a Model Predictive Control (MPC) strategy for a three-level Permanent Magnet Synchronous Motor (PMSM) drive powered by a Hydrogen Fuel Cell (HFC). The integration of HFC with electric propulsion systems offers a promising avenue for sustainable transportation characterized by high efficiency and low environmental impact. The MPC algorithm optimally manages the power flow between HFC and PMSM drive by predicting future events, with consideration of dynamic interactions and constraints in the system. The proposed MPC strategy was validated through simulation results, which showed a reduction in hydrogen consumption up to 10 liters per minute (lpm) when operating at low speeds, compared to the constant flow of 60 lpm at full power. The system also achieved a nominal motor speed of 1483 rpm at 100 lpm of hydrogen flow, however considering the availability of Oxygen (21%) in the air 50–70 lpm of hydrogen flow will be the optimal. The findings highlight the effectiveness of the MPC approach, resulting in an increase in the HFC stack efficiency under varying motor speed conditions. This research underscores the potential of integrating HFC with three-level PMSM drives, offering a sustainable solution for advanced electric propulsion systems with enhanced energy efficiency and environmental sustainability.

Effect of Nozzle Type on Combustion Characteristics of Ammonium Dinitramide-Based Energetic Propellant

The present study explores the influence of diverse nozzle geometries on the combustion characteristics of ADN-based energetic propellants. The pressure contour maps reveal a rapid initial increase in the average pressure of ADN-based propellants across the three different nozzles. Subsequently, the pressure tapers off gradually as time elapses. Notably, during the crucial initial period of 0–5 μs, the straight nozzle exhibited the most significant pressure surge at 30.2%, substantially outperforming the divergent (6.67%) and combined nozzles (15.5%). The combustion product variation curves indicate that the contents of reactants ADN and CH3OH underwent a steep decline, whereas the product N2O displayed a biphasic behavior, initially rising and subsequently declining. In contrast, the CO2 concentration remained on a steady ascent throughout the entire combustion process, which concluded within 10 μs. Our findings suggest that the straight nozzle facilitated the more expeditious generation of high-temperature and high-pressure combustion gases for ADN-based propellants, expediting reaction kinetics and enhancing combustion efficiency. This is attributed to the reduced intermittent interactions between the nozzle wall and shock waves, which are encountered in the divergent and combined nozzles. In conclusion, the superior combustion characteristics of ADN-based propellants in the straight nozzle, compared to the divergent and combined nozzles, underscore its potential in informing the design of advanced propulsion systems and guiding the development of innovative energetic propellants.

Optimization of Quadcopter Propeller Aerodynamics Using Blade Element and Vortex Theory

The optimization of quadcopter propeller aerodynamics is crucial for enhancing the efficiency and stability of unmanned aerial vehicles (UAVs), especially in their increasing applications across various sectors, including humanitarian relief and delivery services. This study focuses on optimizing quadcopter propeller performance using Blade Element Theory and Glauert Vortex Theory to analyze the aerodynamic properties and predict thrust generation accurately. Experimental methods, including wind tunnel testing and static thrust measurements, were used to validate the theoretical models. The results indicate a close correlation between theoretical predictions and experimental data, providing insights into improving propeller efficiency and mitigating aerodynamic losses. By understanding the propeller characteristics, this research contributes to the development of advanced drone propulsion systems with enhanced thrust, reduced drag, and better overall flight performance. The findings also highlight the impact of environmental factors such as turbulence and blade geometry on quadcopter stability, pointing toward areas for further improvement in propeller design. This paper serves as a valuable resource for drone hobbyists, engineers, and researchers seeking to enhance UAV performance through optimized propeller aerodynamics.

CFD unified approach under Eulerian–Lagrangian framework for methanol and gasoline direct injection sprays in evaporative and flash boiling conditions

Innovative synthetic fuels for advanced propulsion systems, such as methanol and ammonia, and synthetic blended fuels (E00, E10, and E30), known for their high volatility, are often injected directly into combustion chambers. It follows that Eulerian–Lagrangian spray models need to accurately capture the spray collapse as a consequence of flash boiling onset and be capable of proficiently handling the preferential evaporation of multi-component fuels in evaporative scenarios.So, we performed the assessment of an Eulerian–Lagrangian CFD code for simulating methanol and E00 gasoline blend sprays in both early and late injection conditions involving flash boiling conditions and preferential evaporation. The adoption of an effervescent breakup model and of a non-equilibrium phase transition model for the discrete phase allows the adoption of a setup that is almost completely free from specific constant tuning, especially for what concerns the breakup model. We validated the simulations using experimental PLV maps of methanol and E00 sprays issued from the ECN Spray M injector. The results highlight a significantly different morphology of the methanol spray compared to the E00 one under late injection conditions. Under stratified combustion, low-volatile fuels are likely to be ignited first, and the flame propagates toward the high-volatile fuels. The spray collapse was also correctly reproduced, inducing the presence of a low-pressure zone and modifying the spray morphology.

Implementation strategy for launch and performance improvement of high throughput manufacturing inspection systems

Product technologies are changing rapidly in advanced automotive propulsion systems. These products are driving the need for new manufacturing processes and new inspection methods. To keep new propulsion systems affordable and ensure these new products are introduced with high quality, automotive manufacturers are seeking automated inspection solutions with low cost and near-zero error rates to inspect 100% of the items. In this paper, a progressive deployment strategy of a hybrid inspection system is presented and studied in the context of technology development and rapid deployment. It enabled us to begin with human inspection and gradually phase-in automated inspection technology, while almost never failing to identify a bad item. This strategy was applied successfully to inspect ultrasonic welds in lithium ion battery packs. At the time of this study, a 75% reduction in human inspection was achieved with prospects for further reduction. Actual results from the implementation of this strategy in production are presented. Recommendations are made regarding the most appropriate time to employ this strategy and how it could increase the use of advanced automated in-line inspection technologies.

Passive control of thermoacoustic instability in a high-efficiency domestic gas stove with fine-tuning burner

Thermoacoustic oscillation is a significant challenge in the development of advanced thermal power and propulsion systems. The present work focuses on the whistling phenomenon in the practical burners of a developing high-efficiency domestic gas stove. The acoustic analysis is conducted by a Helmholtz acoustic solver, identifying the 1/2 wave longitudinal mode in the outer ring or center nozzle and its upstream pipe and estimating the modal eigenfrequencies fa=599Hz and fb=647Hz which are close to the main frequency of the whistling measured in experiments. The sequential flame images captured by a high-speed camera are processed by a dynamic mode decomposition method to illustrate flame structure oscillations at the peak frequency mode. The results verify that thermoacoustic oscillations are the generation mechanism of the whistling and display the periodic fluctuation characteristics of the flame and the spatial distribution of heat release. Moreover, both structural fine-tuning designs help to achieve better suppression for thermoacoustic oscillations and avoid the whistling phenomenon. These structural fine-tuning strategies have been researched for several decades but rarely reported to be applied to industrial burners in previous work. Motivated by this, it will provide a new insight into the investigation of burner structures on thermoacoustic behaviors and the application of these passive control strategies.

Characterization method of conductive film state of micro-cathode arc thrusters

Micro-Cathode Arc Thruster (μCAT) is an advanced electric propulsion system developed in the past decades to meet the maneuvering requirements of space microsatellites. However, the constraint on the its application is the short lifespan of the thruster. This is attributed to the conductive film, a key component of thruster discharge. In this study, we propose a measurement method for μCAT conductive film, and enables the evaluation of the evolution process of film thickness. The method is based on the four-probe resistivity testing theory and size effect fitting model, and establishes a method for characterizing the thickness and resistivity of μCAT conductive films. A comparison was made between the corrected resistivity test results of 1, 2, 5, and 10 μm film and the fitting results of the titanium film, revealing an error ofapproximately 10%. Additionally, a total of 2500 ignition experiments were conducted to verify the film thickness and resistance measurement of this method. This research serves as a valuable basis for the lifetime investigation of μCAT. Consequently, the thickness of the film progressively decreases with each discharge cycle, and the resistivity exhibits a corresponding increase due to the size effect. This method could be used as an effective method for exploring the μCAT lifespan and performance.

Computational investigation of both geometric and fluidic compressible turbulent thrust vectoring, using a Coanda based nozzle

This study addresses the challenge of enhancing aircraft maneuverability, particularly for vertical landing and takeoff, focusing on the fluidic aerial Coanda high efficiency orienting jet nozzle that employs the Coanda effect to achieve thrust vectoring. This research advances understanding of the interplay between geometric and fluidic factors in thrust vectoring. Stationary, turbulent, and compressible flow conditions are assumed, employing Favre-averaged Reynolds-averaged Navier–Stokes approach with the standard k-ε model. Computational solutions were obtained using a pressure-based finite volume method and a structured computational grid. The key findings include thrust vectoring enhancement due to an increase in the total mass flow rate, septum position (at no shock wave-related issues), and Reynolds number. In addition, shock wave formation (at specific mass flow rates and septum positions) considerably affects thrust vectoring. These insights are crucial for optimizing Coanda-based nozzle design in advanced propulsion systems, including in unmanned aircraft vehicles.

Tailoring the electron free path in an ultra-lightweight gas-solid composite insulation system for high dielectric strength

Reliable electric insulation is the premise for the application of high-voltage technologies, such as power transmission, emergent electrified transportations, and advanced propulsion systems. With the current insulation strategy, the credibility of insulation system depends on the sufficient insulation materials usage, suffering from bulky structure, expensive production costs and environmental pollution. Here, we propose a strategy that applies a lightweight multiple-barrier skeleton in gas insulation to tailor electron free path and restrain electron avalanche, thus realizing a high insulation strength with less material usage. This strategy is verified by the composite insulation of porous polyimide aerogel and various types of insulating gases. It achieves a comparable insulation strength to conventional polymers by less than 10% materials usage. With above insulation strategy, a 152.5% improvement in power density and a 54.6% weight reduction are acquired in the cable system for more or all electric aircraft. This strategy inspires the design of efficient insulation solution with both high breakdown strength and lightweight.

Computational Study on Compressor-Combustor Interactions for Improved Matching of a Micro Gas Turbine

ABSTRACT Understanding complex aerodynamics/combustion interactions across major components of aeroengines, including the compressor, combustor and turbine is demanded for the improved performance of advanced propulsion systems. This study employs high-fidelity CFD simulations to investigate the coupled compressor-combustor interactions for the improved performance of a micro gas turbine. In the prototype configuration, the deficient compressor/combustor matching causes insufficient air/fuel mixing and delayed combustion inside the combustor chamber. By reducing the flow area of the compressor and redistributing the air holes on the combustor chamber, a stable united recirculation structure is formed to promote air/fuel mixing and efficient combustion, achieving a over 50% decrease in OTDF and RTDF at the combustor exit and a total 20% decrease of pressure loss in the entire engine through-flow. Compared with the single-component combustor simulation, the coupled compressor-combustor results exhibit stronger turbulence mixing, increased temperature uniformity inside the combustor chamber. Compared with the single-component compressor simulation, the compressor in the multi-component simulation shows the reduced flow angle and Mach number at the compressor outlet, leading to increased stall critical angles and delayed flow separation at the compressor diffuser and vanes. This demonstrates that the added combustor endues the compressor with an expanded operating range and a lower mass-flow rate instability boundary. This work implies that 3D multi-component CFD simulation is necessary to understand the aerodynamic and combustion interactions and improve the multi-component matching in gas turbine engines.

Hydrogen hypersonic combined cycle propulsion: Advancements, challenges, and applications

In the progress toward net zero, two propulsion systems are attracting increasing interest, one based on energy stored in batteries, and the other based on energy stored in hydrogen. In between the applications where hydrogen energy storage has more advantages, there is hypersonic propulsion, which is the object of this perspective. Hypersonic vehicles are aircraft or missiles able to travel at speeds above Mach 5. There are four main types of hypersonic vehicles, spaceplanes, glide missiles, cruise missiles, and aircraft. While glide missiles generally do not need propulsion, cruise missiles, and aircraft are designed to sustain hypersonic speeds for extended periods. They use advanced propulsion systems, which include scramjets, relying on the forward motion of the vehicle to compress incoming air for combustion, and featuring supersonic combustion. While scramjets work well at hypersonic speeds, they must be integrated with other propulsion systems, such as ramjets, rockets, and turbojets, to move back and forth from zero speed. Spaceplanes have been designed so far by using only rockets or integrating rockets and turbojets for better operation in the atmosphere. Spaceplanes' operation in the atmosphere could also be further improved by using ram/scramjets. Point-to-point hypersonic travel for civil applications, which is the focus of this work, requires significant advantages in jet propulsion systems that have to work over different regimes, from subsonic to transonic to supersonic to hypersonic. The work reports on the challenges of hydrogen hypersonic combined cycle propulsion.

Under-Expanded Jets in Advanced Propulsion Systems—A Review of Latest Theoretical and Experimental Research Activities

The current ongoing rise in environmental pollution is leading research efforts toward the adoption of propulsion systems powered by gaseous fuels like hydrogen, methane, e-fuels, etc. Although gaseous fuels have been used in several types of propulsion systems, there are still many aspects that can be improved and require further study. For this reason, we considered it important to provide a review of the latest research topics, with a particular focus on the injection process. In advanced engine systems, fuel supply is achieved via enhanced direct injection into the combustion chamber. The latter involves the presence of under-expanded jets. Under-expanded jets are a particular kind of compressible flow. For this reason, the review initially provides a brief physical explanation of them. Next, experimental and numerical CFD investigation techniques are discussed. The last section of this manuscript presents an analysis of the jet’s structure. The injection parameters commonly used are examined; next, the characteristics of the near-nozzle field are reviewed and finally, the far-field turbulent mixing, which strongly affects the air–fuel mixture formation process, is discussed.

Effects of solutes on thermodynamic properties of (TMZrU)C (TM = Ta, Y) medium-entropy carbides: a first-principles study

High entropy carbide ceramics have garnered significant interest as a novel class of ultra-high temperature and superhard metallic materials. In the present work, a comparative investigation was conducted for the first time on the stability, mechanical, and thermodynamic properties of two medium entropy carbides (MECs), (TaZrU)C and (YZrU)C, using high-throughput first-principles calculations. Additionally, data from groups IV and V transition metal monocarbides were employed for comparison. The temperature-dependent thermodynamic properties, including bulk modulus (B), constant volume/constant pressure heat capacity (Cv/Cp), Gibbs free energy, volume, entropy, and thermal conductivity, were evaluated using the Debye-Gruneisen model. The results demonstrate that (TaZrU)C and (YZrU)C exhibit similar trends in their thermodynamic properties, with (YZrU)C displaying slightly superior performance as the temperature rises. This work provides valuable insights into the design of innovative high entropy fuels, holding significant implications for the advancement of MEC ceramic fuels in advanced nuclear power systems and nuclear thermal propulsion systems.

Liquid Propulsion Systems in ISRO - Evolution and Perspective

The Liquid Propulsion Systems Centre (LPSC) which was formally constituted as a lead Centre for advanced propulsion systems development in ISRO on 1st June 1987 celebrates Silver Jubilee during 2012. LPSC has the mandate of supporting both the Launch Vehicle and Spacecraft programmes of ISRO. Starting with small Liquid Propellant Control Thrusters and Reaction Control/SITVC system development for SLV-3, today the activities of LPSC have grown many fold and encompasses integration and delivery of Liquid Propellant Booster Stages, Cryogenic Upper Stages and total Spacecraft Propulsion systems. Indigenization and production of Vikas Engine, realisation of Cryogenic Upper Stage for GSLV and the development of 200kN thrust Cryogenic Engine for GSLV-MkIII are some of the challenging assignments handled by LPSC which is also gearing up for the 2000kN thrust Lox-Kerosene Semi-Cryo Engine development. It has been a remarkable span of twenty five years of intense learning and accomplishment.
 In this article, based on the AR & DB Satish Dhawan Memorial lecture delivered in June 2012 for Aeronautical Society of India, the evolution of Liquid Propulsion Systems development in ISRO and their increasing role in the current Indian Launch Vehicle programmes as well as the Spacecraft missions viz. IRS, GSAT, Chandrayan etc is described. The new initiatives in advanced propulsion systems such as Electric Propulsion for satellites and 2000kN thrust Semi-cryo engine development for future ISRO launch vehicles are also outlined.

DetonationFoam: An open-source solver for simulation of gaseous detonation based on OpenFOAM

Detonation has promising applications in advanced propulsion systems, and numerical simulation is widely used to gain insights into the complex interaction between the hydrodynamic flow and chemical reactions involved in detonation. In this work, detonationFoam, an open-source solver for accurate and efficient simulation of compressible reactive flow and detonation are developed based on OpenFOAM. detonationFoam can simulate compressible, multi-component, reactive flow and it can accurately evaluate the detailed transport coefficients using the mixture-averaged transport model. Compared to rhoCentralFoam, the improved HLLC-P approximate Riemann solver is used in detonationFoam and it helps to accurately resolve shock waves appearing in detonation. Besides, the adaptive mesh refinement and dynamic load balancing algorithms are used in detonationFoam, which greatly improves the computational efficiency. Validation tests including homogenous ignition, unsteady diffusion, shock tube problem, premixed flame, planar detonation, double Mach reflection, detonation cellular structure and oblique detonation wave are conducted. These tests demonstrate that detonationFoam can be used to accurately and efficiently to simulate the compressible, multi-component reactive flow and detonation processes. Program summaryProgram Title: detonationFoamCPC Library link to program files:https://doi.org/10.17632/x45zh4nz28.1Developer's repository link:https://github.com/JieSun-pku/detonationFoamLicensing provisions: GPLv3Programming language: C++Nature of problem: Gaseous detonation involves different length scales and complicated chemistry. To accurately and efficiently simulate the gaseous detonation, adaptive mesh refinement needs to be conducted and detailed chemistry should be considered. Besides, the severe load imbalance caused by the chemical source term evaluation may greatly reduce the computation efficiency.Solution method: An open-source solver, detonationFoam is developed based on OpenFOAM. The species equations considering detailed chemistry are solved in detonationFoam and thereby detonation in a compressible, multi-component, reactive flow can be simulated. The adaptive mesh refinement technique and the dynamic load balancing algorithm are incorporated into detonationFoam. It is demonstrated that detonationFoam can accurately and efficiently simulate gaseous detonation.

Advancement of extreme environment additively manufactured alloys for next generation space propulsion applications

The National Aeronautics and Space Administration (NASA) has been involved in the development and maturation of metal additive manufacturing (AM) for space applications since the late 2000's. Several efforts have focused on the understanding of AM processes through material characterization and testing, standards development, component fabrication, and infusion into propulsion development and flight applications. NASA matured commonly used aerospace alloys from various alloy families (Nickel, Copper, Stainless and Steel, Aluminum, and Titanium-based) through detailed AM process and heat treatment characterization, in addition to mechanical and thermophysical testing. While these alloys are actively used in many propulsion applications, there is a need for ongoing AM optimized alloys using integrated computational materials engineering (ICME) and process development for high performance applications. The applications targeted are liquid rocket engines; advanced propulsion systems; and in-space propulsion with high heat fluxes, high pressure, and/or that use propellants that can degrade alloys (e.g., hydrogen). This paper highlights the characterization and physical properties of the more common AM alloys using laser powder bed fusion (L-PBF) and laser powder directed energy deposition (LP-DED) processes. Additionally, this paper discusses some of the ongoing novel alloy development and maturation using AM for use in these harsh environments, such as GRCop-42, GRCop-84, NASA HR-1, GRX-810, and C-103. The results from these processes demonstrated that AM could enable rapid development, and that optimized alloys could be developed using ICME, yielding higher performances. These alloys have undergone modeling, fundamental metallurgical evaluations, heat treatment studies, detailed microstructure characterization, and mechanical testing campaigns. This, combined with direct application-specific component fabrication and hot-fire testing, enabled the increase of the Technology Readiness Level (TRL) through high duty-cycle testing. A background and overview of these novel AM-enabled alloys and AM processing developments including metallurgical and mechanical property studies is presented here. The latest advancement in the parallel component development and hot-fire testing and future developments for these alloys is also discussed.

Advanced Propulsion for Fast Lunar Missions

Half a century ago the Apollo missions carried 12 people to spend a short time on the Moon. After all this time, the space agencies of some countries and a number of private companies committed themselves to restart human lunar exploration, this time with the aim to establish a long-term human presence on our satellite and to start a lunar economy. Most of the planned lunar missions are based on the use of chemical propulsion, which allows to perform the one-way Earth-Moon travel in 3 or 4 days. Recently NASA and DARPA joined forces to develop a nuclear thermal rocket for planetary and lunar missions. In spite of the relatively small distance of the Moon from the Earth, carrying the required payload to the Moon is costly and there is some interest in using more advanced propulsion systems, with the purposes of reducing both the travel time and the cost. In particular, advanced propulsion devices will be developed for travelling to more distant destinations and, when they will be available, they could be used with advantages also for the Moon. The aim of the present paper is to discuss the perspectives which will be opened in the future by the possibility of using nuclear (both thermal and electric) or solar electric propulsion and, in a more distant future, nuclear fusion propulsion to travel to the Moon. A number of examples of lunar missions performed with different types of advanced propulsion show what are the conditions at which these advances can be achieved and which are the constraints that will limit these efforts. Keywords: Lunar Missions, Human Lunar Exploration, Advanced Propulsion, Trajectory Optimization, Specific Impulse Optimization

A short review of challenges and prospects of boron-laden solid fuels for ramjet applications

This short review article explores the advancement, challenges, and prospects of boron-laden solid fuel for ramjet. The energetic aspect of boron combustion is well known, but the complications associated with its efficient combustion persist and must be overcome to harness its potential completely. The strategies like coating, adding additives, and utilizing boron nanoparticles, which may improve its combustion performance, are widely studied. The latest development in advanced rocket propulsion systems, i.e., using a hybrid fuel-based gas generator for ducted rockets or air augmentation of hybrid rockets, seems a feasible idea; as it can provide two-stage combustion, which may significantly promote and improve the combustion performance of boron hence the specific impulse. Since it utilizes hybrid fuel, it retains its advantages of it as well as its drawbacks. To mitigate these drawbacks, various strategies/suggestions are briefly discussed here. A fundamental aspect of boron combustion must be fully understood and addressed for its applications in advanced propulsion systems.

An Optimized Electric Propulsion System for Hyperloop Applications

In this paper, an advanced electric propulsion system (EPS) is designed for an ultra-fast electric train. The proposed system consists of a slotless dual-sided linear synchronous motor (DSLSM) and a three-step track powering topology. A multi-objective optimization workflow based on a reduced-order model of DSLSM is used to optimize the permanent magnets (PMs) and the winding dimensions to maximize the thrust force density and efficiency. The optimized model is validated using the finite element analysis (FEA). Then, a new fault-tolerant control algorithm is proposed for the optimized DSLSM fixing the mover in the center of the DSLSM under any airgap disturbance. Finally, a high-fidelity switching model of the complete EPS is developed. The performance of the proposed EPS is verified using a real-time hardware-in-the-loop (HIL) simulator under normal and faulty conditions.

Experimental Investigation into Closed-Loop Control for HTPB-Based Hybrid Rocket Motors

Space exploration greatly facilitates the development of advanced propulsion systems. Extensive research has shown that hybrid rocket motors have bright prospects for use in variable-thrust propulsion systems. However, the variable-thrust precision control of a hybrid rocket motor with a high-mass fraction of aluminum has not been adequately explored. In this paper, we propose a closed-loop control system for a high-performance laboratory-scale hybrid rocket motor, and verify its performance through tests on a hybrid rocket motor containing 98% hydrogen peroxide and hydroxyl-terminated polybutadiene with 58% of an aluminum additive. The results show that, first, the average value of thrust in the stable sections in the three stages were 400.7 N, 599.1 N, and 400.1 N when the target values were 400 N, 600 N, and 400 N, respectively. Second, the average thrust was stable, and the control error of the average value was better than 0.5%. Third, the real-time error in thrust was controlled to within ± 20 N with a steady-state error smaller than 5%. These results indicate that the proposed closed-loop control strategy for hybrid rocket motors with a high-mass fraction of aluminum can maintain a constant thrust and smooth transitions in case of variable thrust.