Engine Design Research Articles

Thermal–structural response and life prediction of lattice regenerative cooling thrust chambers in liquid rocket engines based on a simplified viscoplastic model

With advances in aerospace technology, the reusability of liquid rocket engines has become the focus of considerable research interest. Traditional channel-type regenerative cooling thrust chambers often experience plastic deformation and microcracks, which limit their lifespan. This study proposed a novel lattice regenerative cooling thrust chamber using a simplified viscoplastic model and ABAQUS finite element software to simulate thermal–structural responses under different pressure conditions. The lattice structure not only enhanced the cooling efficiency and reduced the structural weight but also mitigated the plastic deformation and high-temperature creep of the inner wall. At an inner-wall temperature of 820 K, creep damage was significant. Compared to that of traditional chambers, the lattice structure of the proposed chamber exhibited different mechanical behavior and failure modes, with a more uniform stress distribution and initial failure occurring at the lattice nodes. The proposed design avoided the “doghouse” effect evident in traditional chambers, achieving an inner-wall lifespan of up to 202 cycles, a 359 % improvement. The high design flexibility of the lattice structure in the cooling channels enabled enhanced thrust chamber longevity. The study results provide new insights and technical support for next-generation liquid rocket engine designs.

Geothermo-mechanical energy conversion using shape memory alloy heat engine

AbstractThe shift towards renewable energy sources like geothermal energy has become desirable due to the recurrent energy crisis and global warming challenges influenced by fossil fuels. Geothermo-mechanical energy conversion using shape memory alloy (SMA) heat engines presents a novel and sustainable approach for harnessing geothermal energy. Shape memory alloys, known for their ability to undergo reversible phase transformations driven by temperature changes, are ideal for thermal-to-mechanical energy conversion. This paper explores the design and performance of an SMA heat engine that utilizes geothermal heat sources to drive mechanical work. The engine operates by cycling between the high-temperature geothermal environment and a cooler sink, exploiting the shape memory effect to generate mechanical motion. By integrating geothermal energy and SMA technology, this system offers a potential solution for renewable energy generation, with applications in remote or off-grid locations. The paper also investigates output power and the thermodynamic efficiency. A model is formulated and the engine behavior is simulated. A series of experiments are conducted for engine output power and efficiency. The model is compared to the experimental data for validation. The engine developed a maximum power of 3.5, 8.5, and 11.5 watts at 60, 80, and 90 °C respectively. The proposed SMA-based geothermo-mechanical energy conversion system offers a promising solution for efficient, reliable, and scalable geothermal energy harvesting. This research contributes to the development of innovative, efficient geothermal energy conversion technologies, supporting global renewable energy goals and reducing greenhouse gas emissions. This innovative energy conversion mechanism could play a key role in the future of sustainable power generation.

Effective torque modeling of a gasoline-ethanol engine for multivariable adaptive control design

Effective torque modeling of a gasoline-ethanol engine for multivariable adaptive control design

THE COOLING EFFECT OF COMBUSTOR EXIT LOUVER SCHEME ON A TRANSONIC NOZZLE GUIDE VANE ENDWALL

Abstract The ever-increasing combustor exit temperature in modern turbine engine designs raises challenges for the nozzle guide vane cooling. Due to the complexity of NGV cooling design, the cooling effect from the upstream combustor cooling features can prove valuable. This study investigates, experimentally and numerically, the cooling effect of a louver cooling scheme near the combustor exit on the NGV endwall. The wind tunnel testing and CFD simulation are carried out with engine-representative conditions of an exit Mach number of 0.85, an exit Reynolds number of 1.5 × 106, an inlet turbulence intensity of 16%, and a density ratio of 2.1. Various coolant mass flow ratios from 1% to 4% are tested to demonstrate the effect of the coolant rate. For the geometry studied, the results found a critical mass flow ratio between 1%~2%. The coolant forms a uniform film only by exceeding this value to provide good coverage upstream of the NGV passage inlet. As for the cooling of the NGV passage, the mass flow ratio of the range investigated is insufficient for desirable cooling performance. The pressure side endwall proves most difficult for the coolant to reach. In addition, the fishmouth cavity at the combustor-NGV passage causes a three-dimensional cavity vortex that transports the coolant in the pitch-wise direction. The transport pattern is dependent on the coolant mass flow ratio. Therefore, the authors propose combining this louver scheme with the upstream jump cooling scheme for a desirable NGV cooling system.

Speed controller design for turboshaft engine using a high-fidelity AeroThermal model

Abstract One of the main objectives of this research is to construct a high-fidelity aerothermal model for controlling the turboshaft engine power turbine rotational speed. Firstly, a high-fidelity aerothermal model of General Electric T700 is formed. The turboshaft engine aerothermal model is simulated and compared to engine design point data on MATLAB/Simulink environment. Thermodynamic equations and some algebraic equations are used. In predicting compressor mass flow rate, the adaptive neuro-fuzzy inference system method is preferred. A propeller model is also added to the turbo shaft engine aerothermal model and to keep the power turbine rotational speed at a constant value, a Proportional Integral Derivative controller is designed and applied. Open-loop and closed-loop simulations are conducted and successful outcomes are achieved. Results indicate that the differences between simulation and actual engine data are within acceptable limits. The suggested model can be readily updated and expanded to control additional parameters of the engine. PACS 2010 Classification: Control theory in mathematical physics, 02.30. Yy, Computer modeling and simulation, 07.05.Tp, 05.70.Ce Thermodynamic functions and equations of state.

Analysis and Comparison of the Performances and Applications for the State-of-art Thermal Engines

Abstract. As a matter of fact, the development of contemporary internal combustion engines focuses on enhancing fuel efficiency and reducing emissions due to stringent environmental regulations. With the rise of electric cars, the development of hybrid technologies has driven innovation in internal combustion engines, and many modern vehicles combine internal combustion engines with electric motors. In this study, it introduces three different types of thermal engines with latest application in different transportation. By analyzing the limitations of internal combustion engines like thermodynamic limits and emission causing air pollution, it points the direction of future efforts on thermal engines. According to the results, internal combustion engines can be improved by increasing compression ratio through optimizing design and using better fuel like hydrogen. This article hopes to provide a clear understanding of the advantages and limitations of internal combustion engines. For companies and researchers, especially in the automotive sector, it aims to support strategic decisions in engine design and deployment.

Analysis of the Efficiency Improvements for Engines: Evidence from Jet and Marine Engines

Abstract. As a matter of fact, in recent years, the environmental issues are becoming more and more critical due to the huge pollution especially the emission and energy consumption caused by aircraft engines contributes to the problem. Thus, as two major types of engines, the jet engines and marine engines should be improved as they are the most commonly used aircraft engines. In this article, the diversity of some types of jet engines are introduced, and few modifications in the aspect of structure, power system and fuel are briefly talked about. The passage concluded some problems to overcome and actions that may be conducted in the future. At the same time, in another area that is close to jet engines, the engine design of modern large civilian ships (i.e., marine engines) mainly focusing on efficiency, environmental protection, and reliability. However, civilian ships pay special attention to reducing fuel consumption and environmental pollution, which has prompted the application of various advanced technologies.

Critical Role of Solenoid Valves in Modern Engine Design

Solenoid valves, which serve as actuators, are vital in engine design because they can precisely control fluid and gas flow within the engine systems. This allows fuel injection, emission controls, and better performance in modern engines. This paper explores the role that a solenoid valve has been playing in engine designs and underlines its importance for fuel efficiency, emission reduction, and reliability of the engine's performance. Keywords—Solenoid valves, Actuators, Engine control, Fuel injection, Emission control, Engine performance, Valve timing, Fluid flow regulation, Engine Braking, Piston cooling Nozzle valve, CAM phaser Control.

Effect of injection strategy on spray and combustion processes in 2-stroke rod-less opposed piston engine (2S-ROPE)

The 2-stroke Rod-less Opposed Piston Engine (2S-ROPE) is a novel engine design that has garnered attention owing to its high power and low fuel consumption. This study investigated the effects of different fuel injection strategies on the in-cylinder working process of a 2S-ROPE engine, which features a smaller combustion space and lateral injection than conventional diesel engines. A high-precision three-dimensional simulation model was developed to examine the fuel atomization and in-cylinder combustion processes under four distinct injection strategies (S1, S2, S3, and S4). The results demonstrated that the injection strategy significantly influenced the number of oil droplets, particularly for small particles. The number of small droplets in S4 was approximately 6 times that in S1. The double-layer injection strategies (S3 and S4) exhibited a better atomization breakup and oil-air mixing, leading to a faster combustion rate and higher lift power than the single-layer injection strategies (S1 and S2). These findings suggest that the double-layer injection strategy is more suitable for a 2S-ROPE engine, increasing the lift power by up to 23 %. The results can guide the improvement of combustion parameters in most opposed piston engines.

Experimental Determination of a Mixture Composed of Camisea Natural Gas and CO2 Laminar Burning Velocity

The aim of this work is to provide new experimental data on laminar burning velocities for a new synthetic mixture composed of Camisea natural gas and CO2. It was found that the relevant published experimental background data are limited to mixtures composed of methane and CO2; considering the fact that Camisea natural gas is widely used in Peru, this experimental research will serve as a supportive resource for further experimental and industrial implementations in this country, such as the design and modeling of new engines or industrial burners that are designed to be fueled by this mixture. An experimental setup for analyzing three types of flame geometry, which is feasible to implement for a wide range of conditions, was built in PUCP PI0735 laboratory and all the measurements were obtained for a range of mixtures (0%, 21.2%, 28.5%, 38.9%, 50% CO2) and ratios from around 0.55 to 0.95 at atmospheric conditions. The laminar burning velocities results obtained were analyzed in groups based on %CO2. In addition, the experimental margin error was determined by considering all the sources. The following conclusions were reached: (1) The laminar burning velocity decreases with the increase in CO2 percentage in the mixture due to the CO2 decreasing the flame temperature effect. (2) The flat flame type provided the highest value of burning velocity for each group of CO2 percentage in which it appears. (3) The highest obtained laminar burning velocity value was 22.64 ± 0.15 cm/s, for a flat flame with a ratio of 0.72 and 29.98% of CO2, while the lowest obtained value was 6.78 ± 0.15 cm/s for a conical trunk flame with a ratio of 0.59 and 49.83% of CO2. (4) The highest evaluated CO2 percentage was 50.97% for a conical trunk flame with a ratio of 0.69 and a burning velocity value of 11.04.

Generation of hydrogen fuel on board vehicles with internal combustion engines

This article discusses advances in the design of hydrogen fuel engines; the main characteristics of the hybrid engine are studied; prospects for further research are outlined; development and improvement of engine designs, research of processes in engines running on natural gas and hydrogen. Transport is one of the key elements of modern civilization. Its condition and development prospects largely depend on the ability to supply transport power plants with fuel. The depletion of liquid hydrocarbon fuel reserves and problems of environmental pollution may present humanity with a choice - either to reduce transport transportation or to find new ways to supply energy to transport. OBJECTIVE: To review the electrochemical technologies used for the production of hydrogen at gas stations and the operation of hybrid electric vehicle engines using fuel cell batteries. Conduct a comparative analysis of the production and use of energy by electrochemical and traditional methods in vehicles. METHODS are based on analysis of literature data and mathematical calculations. For a passenger electric vehicle, the amount of electricity that can be obtained in a fuel cell by processing 1 kg of hydrogen was calculated. It has been shown that the specific fuel consumption for a hydrogen electric vehicle averages 1 kg of hydrogen per 100 km. Hydrogen has the potential to be the sustainable fuel of the future, reducing global dependence on fossil fuel resources and reducing carbon emissions from the transportation industry.

Retrofit Measures for Aircraft Noise Reduction: Simulation Benchmark and Impact Assessment

DLR, German Aerospace Center, has developed a low-noise retrofit to reduce noise generation of a conventional midrange transportation aircraft, i.e., measures to the airframe and engine exhaust nozzle. Selected measures have been installed onboard of DLR’s flying testbed Advanced Technology Research Aircraft and been subject to a flyover noise campaign. The aircraft in its original configuration and the modified aircraft have been tested and measured in flyover campaigns in 2016 and 2019, respectively. Initial simulation models have been derived from the results and previous component simulations and wind tunnel tests to account for the new reduction measures within DLR’s system noise prediction tool Parametric Aircraft Noise Analysis Module (PANAM). This paper presents the developed measures as selected for the flight test campaigns. An overview of the conducted flight tests is provided. The overall noise simulation process, including aircraft and engine design, flight simulation, and noise prediction, is presented. Simulation results obtained from this process are then compared to the measured levels from the flight campaigns. Estimated simulation uncertainties from PANAM can now be directly compared to differences between measured and simulated levels. Finally, a parameter study is conducted in order to assess the reduction potential of the novel retrofit measures along different simulated flight procedures. Spatial noise distribution in sound exposure level contours is assessed.

Design of an Efficient Multimodal Correlation Engine for Smart IoMT Imaging System for Pre-Emptive Analysis of Breast Cancer Stages

Design of an Efficient Multimodal Correlation Engine for Smart IoMT Imaging System for Pre-Emptive Analysis of Breast Cancer Stages

Innovative Design and Fast Iterative Manufacturing of Micro-Turbojet Engines at Low Cost

The turbojet is the foundation of the gas turbine engine, which combines knowledge of fluid dynamics, thermodynamics, heat transfer, mechanical design, manufacturing, and jet propulsion. This paper describes in detail the inspiration source, design process, fluid dynamics analysis, manufacturing steps, ignition test method and test process of small jet engines. 3D modeling software SolidWorks was used for the preliminary modeling and fluid simulation was performed to optimize the design. Part of the model was produced by 3D resin printing technology, and the turbine engine model was driven by compressed air for no-load testing to verify the feasibility and structural stability of the resin model. Subsequently, some parts were printed with metal materials, combined with traditional machining techniques to complete production and assembly, and finally successfully carried out static ignition tests. The micro turbojet engine designed in this paper has successfully achieved static ignition test and demonstrated the feasibility of efficient development with limited resources and low manufacturing cost. This exploration proves the feasibility of rapid iteration technology route. The market prospect and manufacturing cost of micro turbojet are also analyzed.

Breakup dynamics in a pressure-swirl injector for urea-water solution applications: A computational study

The co-optimization of in-cylinder combustion and after-treatment technology has become a major aspect in engine design and development, with the goal of meeting the increasingly restrictive emission regulations in the transportation industry. Selective Catalytic Reduction is a robust technology to control the emission of NOx, and the injection of urea in water solution is the exhaust tailpipe is a key aspect of its operation. The proposed work uses high-fidelity Computational Fluid Dynamics to characterize the atomization dynamics of the liquid jet in relevant cross-flow conditions. The study focuses on a commercial low-pressure (9 bar) pressure-swirl injector which is characterized in its internal geometry through high-resolution X-ray micro-computational tomography. The internal two-phase flow has been modeled according to the volume-of-fluid approach in a large eddy simulation framework and validated against near-nozzle X-ray radiography measurement. Moreover, characterizing the breakup dynamics for the swirling hollow cone formation, and assessing the influence of the cross-flow in the breakup dynamics was completed. The results have been reported proposing Re-Oh maps and probability density functions of the spray kinematics. Higher cross-flow momentum generates an increase in the jet intact length and a reduction of the liquid droplet diameters. The axial momentum of the jet is affected by the cross-flow already in the near-nozzle region, determining a relevant deviation of the spray velocities. This work aims to inform the initialization of Eulerian-Lagrangian spray models through the assignment of droplet kinematics and static one-way coupling between volume-of-fluid results and Lagrangian spray parcels, to be used for system-size domain simulations.

0D-1D coupled method for performance design and analysis of adaptive cycle engine - Modeling, simulation and validation

Adaptive cycle engine (ACE) can efficiently operate in different modes to fulfill complex mission requirements, which features better mission adaptability than the conventional engine, but also brings great challenges to the performance design and analysis. To deal with the low accuracy of the traditional zero-dimensional (0D) method in predicting the ACE performance under variable geometry and off-design conditions, a zero-dimensional and one-dimensional (0D-1D) coupled simulation method is proposed and validated in this paper. The physics-based 1D mean-line models for the adaptive fan and variable geometry turbine are established, and then coupled with the 0D engine model by iteratively coupled method. Besides, an adaptive selection strategy on the coupling parameters is proposed to improve the convergence issue related to the usage of generic performance maps and accelerate the convergence. Different coupled methods are also compared regarding engine performance, component characteristics and computing time. The 0D-1D coupled method provides a more physical, more accurate and efficient solution for reasonably considering the effects of the design parameters and variable geometry parameters on the ACE performance. The maximum computing time for a single operating point is less than 2 min, which is significant for the quick iteration in the stage of ACE conceptual and preliminary design.

Spray characteristics and combustion mechanism influence on combustion stability of UDMH/NTO pre-combustor under external excitation

To study the combustion stability of liquid rocket engines with hypergolic propellant more comprehensively, external pressure pulse excitation was applied to the UDMH (unsymmetrical dimethylhydrazine)/NTO (methylhydrazine) pre-combustor. The effects of pressure pulse intensity, spray characteristics (droplet diameter and spray cone angle), and combustion mechanism on combustion stability characteristic frequencies and attenuation characteristics after excitation were investigated. The simulation results show that all operation conditions capture the first three longitudinal frequencies of the pre-combustor, and all factors have a greater impact on frequencies with higher orders. Increasing the pulse intensity and reducing the droplet diameter are not conducive to combustion stability. The influence of the spray cone angle on the combustion stability is not monotonous. The pre-combustor has good stability when the spray cone angle is 70°. Different combustion mechanisms have a significant effect on the results before and after pressure pulses, and considering a more complete combustion process may increase the attenuation time in the pre-combustor. The obtained rules can provide a reference for the design and simulation of hypergolic liquid rocket engines, which is beneficial for predicting and evaluating the combustion stability of liquid rocket engines.

Сучасні тенденції розвитку двигунів безпілотних літальних апаратів

The subject of this study is the current state and prospects for the development of the market for unmanned aerial vehicles (UAVs) and power plants. The purpose of this work was to identify trends in the development of UAV engines of various classes. Task: collection, systematization, and analysis of information on the most common engines of reconnaissance and strike UAVs of the operational-tactical level, as well as UAVs of the "barrage ammunition" class. This article provides a brief description of various types of UAV power plants, and their main advantages and disadvantages are given, which are often decisive when choosing the type of power plant for a specific UAV. It was found that a power plant with an internal combustion engine (ICE) is best suited for use in medium- and long-range UAVs.This study demonstrated that four-stroke internal combustion engines are most commonly used in reconnaissance-strike UAVs at both operational and tactical levels. The features of the design and characteristics of four-stroke internal combustion engines, which have become the most widely used UAVs, are described. It was determined that the introduction of turbocharging or increasing the pressure is the main means of forcing four-stroke internal combustion engines, which makes it possible to simultaneously achieve high specific power and high brake efficiency of the engine over a wide range of altitudes during its operation. It is shown that one of the most important tasks for a long-range UAV engine is to reduce the specific brake fuel consumption. Thus, there is a tendency to promote the use of high-powered aviation diesels in long-range UAVs. It was determined that the main requirements for UAV engines of the "barrage ammunition" class are high specific power, low cost and adaptability to mass production. This study shows that gasoline two-stroke internal combustion engines with crank-chamber scavenging are extremely widespread in UAVs of the "barrage ammunition" class. The design features and characteristics of UAV two-stroke internal combustion engines are described. The main means of ensuring high specific power of such two-stroke internal combustion engines are increasing the engine RPM, optimizing gas exchange processes, and reducing the weight of the construction by using new materials. Conclusion. The results show that depending on the UAV type, the set of engine requirements can vary significantly. Modern trends in the development of UAV engines of various classes have been determined. Potentially promising directions for increasing the efficiency of engines and for comprehensive improvement of their indicators and characteristics have been determined.

Virtual Development of a Single-Cylinder Hydrogen Opposed Piston Engine

A significant challenge in utilizing hydrogen in conventional internal combustion engines is achieving a balance between NOx emissions and brake power output. A lean premixed charge (Lambda ≈ 2.5) allows for efficient and stable combustion with minimal NOx emissions. However, this comes at the cost of reduced power density due to the higher air requirements of the thermodynamic process. While supercharging can mitigate this drawback, it introduces increased complexity, cost, and size. An intriguing alternative is the 2-stroke cycle, particularly in an opposed piston (OP) configuration. This study presents the virtual development of a single-cylinder 2-stroke OP engine with a total displacement of 0.95 L, designed to deliver 25 kW at 3000 rpm. Thanks to its compact size, high thermal efficiency, robustness, modularity, and low manufacturing cost, this engine is intended for use either as an industrial power unit or in combination with electric motors in hybrid vehicles. The overarching goal of this project is to demonstrate that internal combustion engines can offer a practical and cost-effective alternative to hydrogen fuel cells without significant penalties in terms of efficiency and pollutant emissions. The design of this novel engine started from scratch, and both 1D and 3D CFD simulations were employed, with particular focus on optimizing the cylinder’s geometry and developing an efficient low-pressure injection system. The numerical methodology was based on state-of-the-art commercial codes, in line with established engineering practices. The numerical results indicated that the optimized engine configuration slightly surpasses the target performance, achieving 29 kW at 3000 rpm, while maintaining near-zero NOx emissions (<20 ppm) and high brake thermal efficiency (~40%) over a wide power range. Additionally, the cost of this engine is projected to be lower than an equivalent 4-stroke engine, due to fewer components (e.g., no cylinder head, poppet valves, or camshafts) and a lighter construction.

Study of nonequilibrium regenerative heat exchange in positive displacement compressors

BACKGROUND: An important task in the design of thermal engines is the evaluation of power losses in different processes to determine the installation efficiency. One of the processes that generates power losses in the compressor is the process of nonequilibrium regenerative heat exchange (NRHE) of the compressed gas with the working cavity walls. This heat exchange occurs at a significant temperature difference, which can lead to noticeable power losses. Modern compressor design methods do not consider losses from nonequilibrium regenerative heat exchange and do not describe them separately from other types of losses. AIM: This study investigates the mechanism of losses during regenerative heat exchange between the gaseous working flow out and the working cavity walls and evaluates the scale of these losses. METHODS AND RESULTS: This work provides a qualitative description of the mechanism for the formation of losses from NRHE. As a result of solving the problem of unsteady thermal conductivity, an analytical expression for calculating such losses is derived based on the Gouy-Stodola theorem. CONCLUSIONS: The study revealed that power losses from NRHE account for a significant share in the overall balance of machine losses. Parameters influencing the magnitude of these losses were also determined, and recommendations were developed to reduce them.